# Data Acquisition is a Reality



## hankster

It's been talked about for awhile. Some have even taken kart systems and used them on their RC cars. Soon you will no longer have to resort to those extremes.

Eagle Tree Systems is in the final stages of releasing a data acquisition system for RC cars. I got a test unit to help them debug it and while I haven't actually got it installed and running. I can give you a few preview pictures.

The test unit (which doesn't even have a case yet) included the following:
Y cables for the steering and throttle servo (for position recording)
RPM sensor
Current sensor
Voltage sensor
Temperature sensor

Weight (no case) including all of the above sensors is 1.5 oz.
Size (no case) 2.75" x 1.25" (about the size of a normal ESC)

Not sure what other options will be available, but it looks like there is room for 8 more channels of data!

I plan on installing it today and giving it a test run as soon as the rain stops... never fails, just when you need decent weather, you get rain!!!

We plan on offering this system for sale and will have a dedicated forum for questions, tips, etc.

Below are a few pics to wet your appitite. I'll post more info as I get further in my testing.


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## pepe

Will it be out by Christmas? I need something else to put on my list,


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## hankster

I guess it depends on how the testing goes.


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## tw78911sc

*G loads*

I'd rather see info like side G loads and slip angle info in helping me get my chassis dialed in. It would be great to see the difference between sets of springs/tires/bodies/wings etc and then tie it to the RPMs

How much does it weigh? Do you download to a laptop?
Tom


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## hankster

First, the unit I have a first production prototype, it doesn't even have a case yet. The software is still beta, so what I now have is subject to change.

Not yet sure of the full options that will be available but looking at the raw data I see places for X & Y G-Force. The data is downloaded to a computer. The present software allows playback in a "real time" display. While that may not be optimal display for closely inspecting the info, the software they have for airplanes does allow for graphing. You can also import the raw data to Excel.

Weight (specs in the 1st message) is 1.5 oz as shown.

*Since it is raining here I haven't had a chance to run the car outside. I did run it in my livingroom but the 8 x 6 foot of space available didn't really tell me much except that it worked.*

I am attaching a graph I did in Excel for some of the data on this test run. The RPM & Amp Draw use the left scale, the Pack Voltage, Receiver Voltage and Motor Temp. uses the right scale. This was captured at 8 samples per second so you can see I have about 25 seconds of data here.


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## hankster

Another note on the data that can be collected. It will record any "glitches" you get in either your steering servo or your ESC... good for finding out if a receiver voltage drop is causing control problems.


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## DynoMoHum

can you give us a ball park figure on what the street price is likely to be on something like this?

I'm drooling already.... This is a gadget guy RC racers dream... and that's exactly what I am...


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## hankster

The current street price for the aircraft system is $150.00. I suspect the car system will be priced very close to this. Since I don't know for sure we can guess that it will be close to the aircraft system since the functions are pretty much the same. They normally include a couple sensors, my guess is these could be the 2 servo Y cables and the RPM sensor.

Also... another goodie, they are working on making it a lap counter also. An external IR beam will trigger an onboard IR sensor to record when your car passes the beam. I suspect it could be used with multiple beams to get split times on different parts of the track.

The nice thing is, is that the system is modulor. You can buy the main unit now and buy other sensors as you need them... they just plug in and you configure the system to collect whatever data you want. Want RPM, Volts and Amps now... great, just get those sensors. Want G-Force or Lap Counting later... no problem, just get those sensors and plug them in... reconfigure the unit to collect that data and you are set to go.


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## DynoMoHum

Sounds like a fair price to me... (well less would be better... but anyway)...

IR beam trigerd lap/segment time... COOL.

For me Amp, volt, and RPM would be great. It might be really cool to have Volts at battery and Volts at motor... however this may not be all that usefull, since the voltage at the motor is plused and that may make it somewhat hard to interpet in any meaningfull way.

Put me on the list of buyers...


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## hankster

To take motor voltage, you could just connect the voltage sensor wire to the motor instead of the battery... I haven't tried it so I have no idea how well it works... will have to try that.

Considering the present day motor dynos (single purpose units) are priced at 500 bucks or so, $150 seems like a bargin to me...


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## McLin

It certainly seems as though this is a “serious effort” and not just a toy. Where the motor information would be nice to have, I think I would be more interested in chassis information. I’m not sure just how they would go about that but things like shock and front-end movement would be good to know. ANYTHING that would show what is really going on when the rubber meats the road!


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## patcollins

This is pretty interesting, I really dont see a need for it for RC cars atleast for me. My interest is in it because I do data acq for a living on military aircraft, but my stuff typically is in the 100 lb range but that is for 100's even 1000's of parameters. Hank if the company needs any technical suggestions for data acq as it could relate to RC cars direct them my way.


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## hankster

This is designed off of a already manufacturered and marketed unit that is built for RC cars. Considering the "guts" are pretty much the same and only the layout was changed to make it smaller, the only real R&D is for the software. For what I would consider a "low end unit" (under $200.00) it does a lot.

I'd like to see 4x the memory, higher sample rates and more sensors. But then would there be a market for something that cost twice as much?

Right now I have my car wired for RPM, voltage, current, motor temperature, steering and ESC. As it is, the wiring is a rats nest. I suppose it could be made a little neater but having many more sensors then this can end up being a real pain to wire and maintain.

Pat, I'll contact them and see if they require any assistance.


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## pepe

I agree with Mclin, the more we know about what is REALLY HAPPENING on the track the better off we are,this may just completly change the way we think about set ups.Not only that but think what it will do for manufactors when it comes to new designs.


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## Fred B

The major addition of the new system is amps. They have an area on the board for acceleration so I'm assuming that it's just not in there yet.

Once you have amps and RPM, it's off to the dyno. You can also see the changes in gearing which is a must in 12th. I'll be running it a little more this weekend.


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## DynoMoHum

Ok, once they get the load sensors G force and all that stuff, then transmit it to a remote seat that I sit in and it gives me real time feedback so I can feel the car break loose in the corner and correct for it...


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## hankster

For those that are testing the system, could you please contact me via email. I'd like to have a private area where we can discuss the system and what is being found. Also, we can discuss how best to address some of the improvements that are needed.


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## hankster

Here is a picture of the case that the unit will be enclosed in. I understand the production label is slightly different then the one shown in this picture.


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## patcollins

What are the servo connections for?


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## hankster

It records the position of the steering servo and throttle esc/servos.


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## hankster

Just an update, the latest version of the software allows real time recording of data while hooked up to the computer.

This could lead to all kinds of interesting options.... how about a full chassis dyno that records motor RPM, Amp draw, MPH and Voltage? This could make dedicated motor dynos obsolete!


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## lannyt

Has a price been determined yet? Curious as to how much this is going to cost, software included.

Thanks


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## patcollins

On tower hobbies website they have the airplane version for $144.95


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## hankster

The price is not set yet so saying what i think it would cost could give a false impression. BTW, what do you think it is worth and what, out of the above sensors, should be included in that price?


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## McLin

They really do seem to be doing their homework on this one. Looks great. I do have one concern though and that is the type of computer it will take to use it. The reason I say that is, most of us use a pretty cheap lap top to carry around to the race track. Maybe USB adaptors could be an "option" or at least put it in the directions as to where to get them (Radio Shack part numbers and such).

Just a thought. I for one am VERY interested in this thing.

Keep in mind guys that this is a "set up tool" and it's not legal to race with it in your car. But, that is why it is being made.............SETUP!

As for what sensors?.................All of them, don't go half way now!

Put me on your list Hank!


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## McLin

Didn't read one of your post above before I posted the last. ON THE TRACK, LIVE INFORMATION!! This COULD do away with dynos and achieve better information!! IF it could send back AMP, RPM and VOLTAGE, and they could figure some type of "time factor" into it, then TORQUE could be calculated also.

DANG! Put me on your list TWICE!!! and UNDERLINE it!! LOL


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## hankster

It should run fine on most any system that can run Windows 98SE or later. I have a 233Mhz laptop that I will be trying the software on.

For the most part the computer does nothing but download the data from the recorder and store it for further use. The software does have a "payback" mode where you can see the results just as if it was in your car, but I find this is not as useful as the graphing feature that will be added.

The "real time" part of the software is not completed yet, so I have no idea how that works yet. Non the less, I will be testing on my laptop so we can see if it works on one with that slow of a processor and will report how well it works on that.

USB to Serial port adaptors are available. I'll look up some RS numbers but I'll bring this up to them and I'm sure they can find a supplier so they can offer them too. Also, there are USB PCMCIA cards available for laptops. But a minimum of Windows 98SE will be needed for proper USB support in most cases.

With the way laptop prices are dropping it's almost worthwhile to buy a new or used one. New Dell laptops can be had for $600.00 and good used ones are available for $300 or less

I see no reason why it couldn't be used during racing. It isn't "active" in any way, it does nothing to "control" your car, it is passive in that all it does is collect data.

Note on possible new feature: At this time the fastest collection rate is 10 hz or 10 readings per second. They are going to try and boost that up to 20 hz. This would be most useful for oval races as this will cut down the total collection time to somewhere around 60 seconds but will provide detailed information for those fast 3 second lap times we see on some short oval tracks.


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## pepe

Yea this is defintly going on my list of must have's sign me up Hank.


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## patcollins

10 Hz, that really means that we can only really see what is going on with any hopes of accurately recreating the signal would be at a frequency of 2Hz (Nyquist theory).

A motor dyno would have to sample at approximately 3500 Hz to be of much use. 

Data is so easy to misinterpret and the data acq is so easy to take for granted, I guess thats why I have a job though.


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## McLin

Hank, I haven't bothered to look up the rule because it is just not that important to me LOL but if I remember it right, there may be some questions about it. Like I said though, I just don't care, all I would want it for is tuning anyway.


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## VegasJim

Does this use the cars battery for power or does it have its own power source? What is the voltage required?

Lateral G's would be very useful. Then you could compare steer input to lateral G input. This would tell you if you have a over or under steer situation.


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## hankster

I wanted to post this interesting throttle curve that I found when the data recorder was hooked up to my GM ESC in a pan car. The curve shows about 3 sec of an acceleration curve. The car was off the ground and the wheels stopped. I fully gunned the throttle for a short time to come up close to full speed and then let off the throttle.

The ESC has a "traction control" system turned on where it is suppose to limit the current for a short time to help eliminate wheels spin when you quickly hit full throttle. I noticed when hitting the throttle that the motor would sort of stall for a short time after I hit the throttle and then go to full speed… this was strange, I never noticed it before.

Looking at the graph we can clearly see that the RPM is actually limited for about 1.5 seconds before full power and RPM is allowed. Since it doesn't appear that the current is actually limited, the ESC must be internally limiting the amount of throttle being applied during that time.

Also notice the small amount of "regeneration" when I let off the throttle.


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## hankster

Opps, forgot to attach the graphic, here it is.


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## DynoMoHum

Hank, 

Somewhere up there you asked what sensors we thought should be included in the price for $150 or so... Well... From my perspective, Voltage, Current, and RPM are essential for electric car system components.... I'd like to see all three in a package deal, even if it meant paying slightly more then the $150 price. I'd not really like to have to buy extra sensors just to get what I would consider essential for electric RC car info.


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## hankster

I believe that there will be some type of "base" unit with general sensors (servos, RPM) that can be used by all kinds of vehicles, then packages available. Since the needs for electric and nitro are different, it makes sense to do it that way. But I ask so we can see what people think.

Everyone's feedback is being read by the manufacturer so keep it coming.


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## hankster

patcollins said:


> 10 Hz, that really means that we can only really see what is going on with any hopes of accurately recreating the signal would be at a frequency of 2Hz (Nyquist theory).
> 
> A motor dyno would have to sample at approximately 3500 Hz to be of much use.
> 
> Data is so easy to misinterpret and the data acq is so easy to take for granted, I guess thats why I have a job though.



Pat, Since they read the messages here they wanted to comment on your post. To quote their email:


> The recorder does sample motor current/voltage at a much, much higher rate than 10Hz, but it averages the values it records and reports that average once each logging period (10 averages/second for 10hz).


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## hankster

I've had a couple questions via email about mounting the RPM sensor. In the attached example the sensor is mounted to the rear pod plate with servo tape and the two magnets are super-glued to the diff hub.


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## patcollins

*The recorder does sample motor current/voltage at a much, much higher rate than 10Hz, but it averages the values it records and reports that average once each logging period (10 averages/second for 10hz).*

For all intensive purposes that is no different than sampling at 10 Hz. The averaging does smear out noise, but it also smears out your signal.


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## billpa

Hi Pat,

The purpose of the current/voltage acquisition feature is to provide logging ahmmeter/voltmeter functionality in an actual race setting, rather than just on a bench.

To get accurate results, we have to take tons of almost continuous samples over the logging period (1/10th second for example) and average these together for each log. This of course is required due to the sinusoidal nature of motor current draw. If we didn't do this, and only sampled once every 1/10th second, we'd get random numbers corresponding to whatever the current draw was at that instant.

As it is, the values logged now agree closely with units such as the Astro Whattmeter. The Whattmeter seems to average over a much longer period however, like 1-2 seconds rather than 1/10th second.

As you point out, the unit is not designed to log at the rate necessary to plot the actual sine (or other) waves of motor current draw that occur as the motor rotates thru a single revolution. I'm not precisely sure how this level of data would actually be used for tuning, but I'm interested in learning! Let me know your thoughts on this and if there are different data that we can consider logging in the future.

By the way, thanks to you all for providing all this great feedback! We're paying close attention to it and it's very helpful.

Bill Parry
Eagle Tree Systems


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## patcollins

Hi Bill

Its great to hear from you. Just want you to know that Im not bashing your product in any way, im always amazed how small these things can be made. 

I think these very short "abnomalities" can actually be very useful in tuning a motor. But that is just conjecture on how and I wont get into that. 

My main reason for thinking a10Hz sampling rate isnt enough is that when coming out of a corner a motor accelerates a car to atleast 80% of its top speed in about 2-3 tenths of a second. This is pretty much what makes a difference between a slow car and a fast car. If the phenomonem happens this fast I think that this is the most important thing to capture for data analysis. 

Off topic but possibly interest to you, I recently did a job where 35 strain gages needed to capture the peak strain caused by gun fire. The pulse took place over 1 millisecond. Typically it would be sampled at 10x this, but since we wanted to capture the peak within 99% of its full value I sampled 25x every millisecond. I think uping that to 35 or so would have helped but I had run out of bandwidth.


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## billpa

Hi Pat,

Definitely not considered bashing in any way. Great feedback! 

The recorder should be able to go up to 20hz. Do you think this data rate would get you the info you need?

Thx,

Bill


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## patcollins

It would definately help, is bandwidth or frequency response of the sensor the limiting factor? Personally I would give up the other functions for a 100Hz sample rate with a record time of 60 seconds, I would also settle for 10 bit resolution too.


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## DynoMoHum

I know next to nothing about data acuasition, not even how to spell it... However I'm with Pat in the sense that I really would be interested in having at least the option of seeing everything as fast as possible , even if it meant a realtively short collection period was possible... 60 seconds worth of data, in very fine detail would be very nice for some interesting things... Heck even 30 seconds worth of data would be cool, if it meant getting raw data that was not filtered and such. 

I wouldn't want this to be the only mode available, but it certianly could prove to be very interesting at times.


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## billpa

I'll see how fast we can get this puppy to go! 

Bill


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## McLin

Man! I'm almost ready to PAY to help test this thing LOL


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## hankster

I am posting attaching a screenshot as an example of what can be displayed. You can configure the display to show a number items that are recorded and show then in graphic or digital format.

When you first load in the data (as shown here), the display shows the maximum and minimum values for the complete run. For example, in this case we can see the maximum RPM, max Amp Draw, minimum Pack Voltage, etc. Not all the data is here as an incomplete data file is being used.

More example coming as I do some more testing.


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## patcollins

Hey I really like the look of the playback software. 

Still there is nothing like looking at the raw data files for info though.


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## tw78911sc

didn't see anything to do with G loading or the rpm difference between L & R or F & R to determine wheel spin or slip.


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## hankster

Graphing is being added to the software but is not included yet. You can look at the saved raw data now in Excel. There is a spot in the raw data to store G Force but I suspect the G-Force sensor development is not complete yet. There is only one RPM sensor so you can not get wheelspin.

The data holders in the raw data files now include (I would guess this is still subject to change): Steering Throttle RPM Speed Rec-Bat*10 Temp1*10 Temp2*10 Amps*100 PackVolt*10 GForceX GForceY ThermoA ThermoB IsEvent EventError EventData Timestamp


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## SecretSquirrel

patcollins said:


> 10 Hz, that really means that we can only really see what is going on with any hopes of accurately recreating the signal would be at a frequency of 2Hz (Nyquist theory).
> 
> 
> Actually the Nyquist Theory states that the sampling frequency needs to be greater than twice the maximum frequncy in order to remove any aliasing from the signal. That would mean 5 Hz resolution at best, not 2 Hz.
> 
> Hank, do they have any intentions of trying to beam the data wirelessly. Being able to watch the data in real time while the car is on the track would be very cool.
> 
> Also, do they have a website. I do DAQ for a living and would be interested in learning more about what they are doing
> 
> SS


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## patcollins

SS, 2 is theory, but ever look at a sine wave? If you sample twice the frequency of it you could actually end up hitting the zero crossings and think you have no signal what so ever. In the real world 5x the filter cutoff frequency is the minimum acceptable to avoid "folding" effects of your data. 10x is more of an accepted value. 

The only thing 2x is really good for is if you only want the power spectral density of the data and dont care about the actual amplitude of the data or signal recreation. Thats something they dont teach in any class, but you can find tons of published papers on the subject matter, hopefully one by me soon on maximum amplitude capture.

Tons of good publications can be found through www.telemetry.org


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## hankster

I don't see wireless anytime in the near future... for many reasons. Their web site is http://www.eagletreesystems.com


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## SecretSquirrel

Thanks for the info Hank.

If you decide that testing that unit is too much work for you I am sure I could help you out with that 

I love the idea of this and I am sure the release version will be sweet.

Pat - lets see - gunfire testing in Maryland. I bet you are somewhere near Aberdeen  I am a DAQ guy myslef, but most of what I do is 0-20 kHz noise acquisition - accels and microphones for measuring automobile service brake noise.

I wonder if the logger could be configured to run at different sample rates within the 10-20 hz scan rate. For example, temperatures change very little in .1 seconds, but amp draw does. It would be interesting if you could run a sub-scan at a higher rate (50-100 Hz), but only 1 or 2 channels and run the rest at a slower rate (.1 Hz).

Just thinking out loud
SS


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## patcollins

Not Aberdeen, thats Army, I work for the Navy about 2 hours south of Aberdeen.


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## SecretSquirrel

Pat,

My brother is at Aberdeen with the Army so I assumed. Sounds like you do some interesting work.

SS


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## patcollins

Small world eh, I graduated college with several people that work at Aberdeen. It is an interesting job, never the same thing twice however the way us "support" people are treated leaves alot to be desired.


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## patcollins

billpa

You had mentioned averaging data into 1/10th second samples to get out the higher speed stuff. Has any thought been put into using a presample filter for the current sensor? I think a good filter would help with obtaining good usable data for this. Not sure on how small it could be made but a 6 pole Butterworth is fairly simple and does the job quite nicely.


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## billpa

Hi Pat,

Tell me more about what the additional filtering would provide you. We currently already do the averaging in firmware to get the average current (and voltage) over the sampling period. The results we get on both current and voltage (and hence AH and Watts) closely matches what traditional instruments like the Whattmeter record. 

Thanks!

Bill


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## patcollins

What a presample filter can do is can get rid of higher frequency signals (its a low pass filter) that you can't properly recreate anyway due to your sample rate. Lets say the highest frequnecy of interest would be 100 Hz, I would design a filter so that the signal would be 99% there at this 100 Hz, for a 6 pole butterworth filter the fc would be 1.4 times your sample rate or in this case 140 Hz. Then I would sample atleast 5x fc to accurately recreate the signal.

These filters are often refered to as anti aliasing filters, they really help clean out noise that otherwise wouldnt do anything except affect what you are trying to measure in a bad way. 

The hard part about DAQ isnt getting information, its knowing what information that you are not getting. Presample filtering helps in this respect.

Personally I would get rid of the averaging feature and take data at whatever rate you can and put a filter in there, that way you wouldn't have to worry about it and with an electronic filter such as this there is alot less error in what is actually measured.

It would probably add a bit to cost but would result in a much better unit, one that I would be more apt to trust the data from.


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## McLin

Dang!! Just think, last month all I was interested in was getting a good stop watch!!!!! LOL


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## Fred B

I haven't seen any erronious data yet. Don't forget guys, with the extra sample rate, you're going to get overwhelmed with data.

Just as an example, for a track like Cleveland...The running line is 330 feet or so and the lap times were 10-12 seconds. with the sample rate at 10 HZ, that's 100 to 120 data points at between 3 and 3.5 feet average (5 or so on the straight)(3000 points plus in 12th). With the exception of that "thing" going onto the straight, you could capture the entire layout easily and draw it from the data.

Sample any faster, and you'll lose the end of the run. You end up missing how much the motor and batteries drop off and that's very important. Even with more memory, the data might not fit into Excel easily.

I'm currently cutting out laps at the beginning, middle and end of the run.


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## DynoMoHum

Don't forget us oval guys... 3 scond laps...

Or worse yet... a drag racer...

All I need for many purposes, is a few good laps worth of data... If I need more laps, and there's a option to slow the collection rate down and I can get a whole 4 minutes, I'm good.


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## Fred B

A 220 ft track at 3 seconds and 10 Hz is just over 7 feet apart on the track and 30 datapoints per lap. I can see where it would be nice for oval racing to have a little faster sample rate but there is plenty of data in a 4 minute acquisition to pull out what you need.

The one thing that would be nice would be to have a marker in the data for the start of each lap (or at least close). It's pretty interesting to see how the two ends of the track are different.


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## eric_kav

I can "look" really fast with one of these. Looks are important to us slow guys!


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## albie

Since im mostly a drag race only guy will this thing work with say 10 or 17 cells without blowing up the voltage and amp readings.... i remember the victor iq tracker it didnt start recording till after 3 sec into the run no good for drag racing we need something that will record right at the pull of the trigger .. let me know want to put it in my record setting cars to find out whats going on inside......albie


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## hankster

The unit draws its voltage from the receiver. Since you most likely use a 4 or 5 cell reciever and don't feed 12 to 20 volts into your receiver you shouldn't have any problems. The unit starts recording as soon as you turn it on, so it will catch before the beginning of the run and even after the run is over.

Now, I am not sure how high of a pack voltage it can read, Bill should be able to answer that. If nothing else you should be able to put a voltage divider into the pack voltage circuit to chop the voltage the unit reads in half.

From what I understand the amp sensor is rated 100 amps but will handle 120 amp spikes.


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## PizzaDude

Seems to be some off-topic action slipping into the dynothread.
sorry.

http://www.hobbytalk.com/bbs1/showthread.php?p=628996


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## billpa

Hi,

Re max current/voltage, he system will measure voltage up to 50 volts and current up to 100A. Nothing bad would happen with higher current spikes. 

Thx,

Bill Parry
Eagle Tree Systems


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## Fred B

Actually, when I posted on the other thread, I was more interested in how people would be using the data with their dyno's.

Also, I'm working on a new spreadsheet for the new logger that I will post sometime after the new year. I was thinking about automating things a little but I'm pretty much too lazy to write the macro's. You guys can get an idea of what's going on from the old data that I posted (it used the Flight Data Recorder).

At full throttle you are measuring motor and pack voltage (there's basically no resistance in the circuit). At part throttle, you are measuring pack voltage only but if you're at part throttle you have more than enough power anyways.


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## Fred B

One last thing, the "cockpit" playback in the program is very useful for finding your place on the track and pausing the run to record times for a spreadsheet. Also, you can use it to quickly compare two runs by switching back and forth between files.


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## hankster

Fred, That's fine, just wasn't sure if those in the Oval area had seen this thread. Anyways, as you can see, I've open a whole new area for the system. Carry on...


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## PizzaDude

Fred B said:


> One last thing, the "cockpit" playback in the program is very useful for finding your place on the track and pausing the run to record times for a spreadsheet. Also, you can use it to quickly compare two runs by switching back and forth between files.



Fred,
Do I understand correctly, that the excell sheets as well as the Cockpit will be available.
Not one OR the other.

Man that souns like the best of 2 worlds then.


But comparing 1 graph to oneother by pasting #1 over #2 in the same graph, will not be possible?!

thnx


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## patcollins

Fred B said:


> I haven't seen any erronious data yet.



Not sampling fast enough will not cause erronious data, but it can make you think the shape of the data is different than what it really is. Remember data acq is taking discrete points not the entire signal. Only knowing these discrete points forces you to interpolate what the data looks like in between them. 

Imagine if your system only took data before you started and after you quit, it would read 0, but that would in effect be correct. To find out whats in between you have to sample faster and faster until you find a "good point". 

In my field we generally know what the maximum frequency of interest is because we know the natural frequency of a vibration mode and we will often capture 2nd, 3rd, 4th harmonics etc.

I have taken data as fast as 10,000 samples per second and still needed faster to see what happens "inbetween".

Wait I got the perfect example, ever watch an old cowboy and indian movie? Ever see the wagon wheels look like they are going backwards? This is because movies are actually discrete images taken at a time interval. It turns out that the capture rate of the camera wasnt fast enough to show a true signal of the wagon wheel and the data was aliased. I know this is a difficult concept to grasp for someone not in the field, it took me a while to believe it when I first read about it but that example should help.


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## hankster

PizzaDude, Graphing will not be a feature when the software is first released. It will be added in a future release. Graphing is now being done by us using Excel. So by using Excel it is possible to import or cut and paste two or more data sets if that is what you want to do.

I wish I knew Excel better so I could make a "snappy" spreadsheet to distribute but about all I know how to do is import the data into Excel and create a graph.

The data is saved to your computer in a space delimited format so it can be manipulated by the user however they want.


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## PizzaDude

Sounds great ( I keep repeating myself)

Well even the excell as it was shown shows a lot clear info!


Questions keep popping to mind.I hope you don't mind me asking!

How long is the recording time of this data?
Is the recording time expendable?
Can it be used troughout a days testing and at home be read-out by the PC?
Wil it be represented as for example 5 different runs? 
Which can be saved with each individual setup?

As some of the pics shown as well as reading this thread, should be pretty close to release.
Will there be a first batch (proto or early production) first be available for members of Hobbytalk?

Well, that's it for now!

Pizza


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## Fred B

The Excel sheet was somethign that I was working on using the old logger. The data from the new logger is pretty much the same. The only downside to using Excel is that you have to pick out the data that you want to graph from well over 1000 lines. It's really not that hard if you have a template, but it is a little time consuming.

Pat, I understand the problems with sample rates. Work with them every day. Two things. First, You can get a pretty good idea of what's going on from the data with the current sample rate. Also, Bill is saying that there is averageing over the .1 second sample time. This will act like a filter filter for what is probably a very dirty signal. You will still see the initial spike and have a good idea of it's shape.

Just an FYI. It takes a couple of tenths of a second to pull the trigger and for the speedo to react. I'm guessing from the data that this ramp up reduces the current spike somewhat. 

As for the logger questions, It is not currently expandable but it has plenty of memory to record several runs and then take it home. The data remains stored without power. You have to keep track of what you ran on each run. I can get over 8 minutes if I turn some of the extra stuff off.


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## hankster

As Fred has stated, I have also found the information given very useful even if it is at 10hz. I guess we could go to the extreme of saying we would have to gather info at least at 180Khz (20K RPM * 3 armature segments * triple samples per segment) to get the kind of detail some are asking about, but that's not likely to happen. Anything less then that is filtering

I think most will find the info very useful. As shown in the graph segment here > http://www.hobbytalk.com/bbs1/attachment.php?attachmentid=6709 and as Fred brought up, I would think most never thought that it takes a couple tenths to pull the trigger fully... that is something no dyno duplicates.


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## albie

will there be a way to get the logger upgraded to show more amps.. in drag racing 100amps isnt seen to estimated 30 ft after the launch so there is alot of data gonna be lost from the begining of the run till the motor winds and the amp drops under 100. also say i want 2 rpm sensors can this be done as i would like to see how far the car carrys the front wheels .. i think this is great and in a drag car can provide alot of useful data especially as the amp draw can be used with the dyno... albie


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## patcollins

Im not saying it has to be that fast. Hank your math is off by the way you forgot to divide by 60 to convert minutes to seconds. 

A couple tenths to pull the trigger and for the speedo to react, man could I get a holeshot on you.


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## hankster

Oh yeah... divide by 60. Even so, at 3K hz just the electronics to count and store that amount of info for one channel would cost more then this whole unit costs.

Wait till you get one... you might be surprised at what the data shows you...


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## Fred B

If you want to get an idea of how quickly you can pull the trigger, get out the old stop watch and see how quickly you can start and stop it with your left finger. Thing is, the trigger throw is much farther than the button on the stop watch. We saw the same results logging at 100 Hz on our Pace Sci logger. I've yet to find relavent data that's missed at 10Hz and I have used loggers that sample much higher.


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## hankster

You can view a preview of my "public" review of the unit. You can check it out at http://www.hobbytalk.com/datarecorder/


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## SecretSquirrel

*Excel Macros*

All,

Excel macros is a good portion of what I do for work. We have a variety of functions and subroutines that do most any kind of data import and graphing you would want. If you list your requirements with a hunk of sample data I would be happy to do the macros for free.

Post the data, the requirements, and give me a couple of days and I will get it done for you.

Let me know
SS


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## hankster

The new software that just came out tonight has graphing built-in. So, for the most part, using Excel will no longer be needed.

Although some may find using Excel may be easier.... YMMV.


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## PizzaDude

SecretSquirrel said:


> All,
> 
> Excel macros is a good portion of what I do for work. We have a variety of functions and subroutines that do most any kind of data import and graphing you would want. If you list your requirements with a hunk of sample data I would be happy to do the macros for free.
> 
> Post the data, the requirements, and give me a couple of days and I will get it done for you.
> 
> Let me know
> SS



Squirrel, 
I am interested for sure.
A nice idea could be if you can combine the CDR-data (CarDataRecorder) and laptimes combined.
Laptimes fi being imported from Maylaps.com.
Or imported from the Orion lapcounter software....

Hank, 
Will Eagletree be devolloping an integrated lapcounter in the near future?


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## hankster

PizzaDude, It may be possible to make a lap counter. I am looking into it now.


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## albie

Hank this is the best thing since the motor dyno... i hooked the rpm sensor today in my drag tc3 which i use to test my drag motors and breakin my drag batteries... tc3 hit top speed of 61 mph and 65000 rpm.......... i double checked all the parameters and the motor in the car is my #2 drag motor with my #3 6 cell drag 2400s ..............cant wait for the g force meter


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## swtour

what would it take to add a "Flash Media" or memory stick type card to the data recorder for additional memory?


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## hankster

Albie, Let us know how it works out in your drag car.

SW, It would be pretty much impossible to add memory. Why would you need more then 6+ minutes of recording?


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## vtl1180ny

Ok, I think I saw it posted but is there a mode which allows me to plug the car into the computer while on a stand and watch in real time??? This is my deciding factor....


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## albie

hank i recieved the new sensor today and all is working great.. only thing is the amps meter says high of 17.86 but the car was drawing 117.86 which the graphing shows..

vtl.. yes the recorder can go live and run on a stand and you can see things in real time.. albie


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## vtl1180ny

Cool... Been lurking since I somehow found the link to the recorder and to here... I toasted a P2K2 this weekend and would have to seen why, I'm gathering this would have told me why if I had it last week...


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## ahibj8

I have just got mine :thumbsup: now its time to start playing LOL

Thanks Hank 

Scott J


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## hankster

Yes, there is a real time mode available.


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## SecretSquirrel

If someone would post a small chunk of Car Data Recorder data and some Lap Counter data I will make a macro to inport and graph it.

Let me know or PM me to take this discussion to email
SS


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## jerrit1

Can someone with the car data recorder give me some info:

I'm interested in knowing if you take a stadium truck like a XXX-T and a stock motor and 3000 or 3300 batts and nail the throttle from a stand-still and/or out of a turn how low does the battery voltage go? how many amps is the motor drawing?

How about wide open on the straight...just before breaking for the turn, what is the battery voltage and how many amps is the motor drawing?

Thanks for your help.

Jerrit


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## hankster

I've seen somewhere around 40/45 amps and a drop in voltage for about 1.6 volts on startup. Amp draw at the end of a long stright is about 14 amps with a voltage drop of about .6 This is on a track with fairly low traction.


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## hankster

albie, Could you report the problem to [email protected] I haven't drawn that high an amp rate so I never noticed it before... most likely just needs a tweak to the software.


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## albie

hank iv talked to bill about this already.. he is a great person to deal with.. i took the car out yesterday and made a few runs the car pulled 118.2 amps the voltage was 8.3 until the amps hit then the car battery dropped to 4.78 volts this was for about 2-3 tenths of a sec...then the amps leveled out to about 70 and the voltage went up to 6.67. this little unit is very interesting and just seeing how the voltage drops is amazing.. also when the amps hit and the voltage drops the reciever voltage drops also on the cyclone .. im gonna put either a stock motor or a 19 t in the car and play with that... dont like putting wear on my drag motors... albie


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## hankster

You mean you aren't running one of our receiver packs in your drag car????


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## SecretSquirrel

*Data File*

Would someone be willing to send me or post a raw data file from the Data Recorder (new version) so I can see the data format in its rawest form?

A full run in Comma Seperated or something similar would be great.

Thanks in advance
SS


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## Fred B

Albie,

The voltage drop is why we run receiver packs in 12th. The speedo won't boost voltage above pack voltage so it falls off under heavy load. It still happens to a degree with 6 cells but is probably a little worse with drag motors.

Now you can test different cells to see what ones pall off the least.

FB


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## albie

thats the idea im having fred.. i want to test the diff between 48 and 64 pitch gears as some people say 48 robs horsepower.. i personally run 48 pitch and have since day 1 and i cant get the 64 pitch to run for me.. i cant wait for the g force meter so i can do some more testing...

hank i dont run my drag cars outside of national events for any reason in the drag cars i run microswitches and yes i do have a reciever pack in the car .. when it goes bad i will order from you for sure..... i have a tc3 with a cyclone in it that i use to test motors and breakin batts with that is set up with locked diffs. im currently using the tc3 as a test bed just to get aquainted with the onboard computer..
i would like to see a way to graph 2 runs side by side to see the difference between 2 seperate runs to map how changes will effect.. 

hank any info on the g meter when it will be avail.....albie


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## hankster

No info on the G meter yet.


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## Sands

don't know if this has been asked yet...

Motec (the 1:1 car DAQ and engine control company) has a system where they map out the track layout, then overlay acceleration, braking, g's etc. on the picture. anything like this for this system?

sands


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## hankster

No, there is not anything like this available... but then we are talking about a $200 system compared to a $5000 system.


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## Sands

On the g meter stuff. Have you looked a MEMs devices? They are essentially board mounted accelerometers. I am an engineering manager at an appliance manufactere and we recently added some to a consumer machine for vibration and displacement monitoring. If memory serves, they are less then $5 bulk cost.

www.analog.com is a manufacter of them. Specs range from up to 5g to 10 g, less then .5 mA draw, up to 5 volts and analog output. Resolutions at 2mg and a 2.5 hz bandwidth. Should be more than adaquate for an RC car. They will also do 2 axis measurements for acceleration and yaw.

full link:
http://www.analog.com/Analog_Root/s...D212%26level2%3D213%26level3%3D%252D1,00.html


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## Sands

Oh yeah, they also have gyros for yaw rate measurement - would be cool for your airplane applications.


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## Sands

albie said:


> thats the idea im having fred.. i want to test the diff between 48 and 64 pitch gears as some people say 48 robs horsepower.. i personally run 48 pitch and have since day 1 and i cant get the 64 pitch to run for me.. i cant wait for the g force meter so i can do some more testing...
> 
> hank i dont run my drag cars outside of national events for any reason in the drag cars i run microswitches and yes i do have a reciever pack in the car .. when it goes bad i will order from you for sure..... i have a tc3 with a cyclone in it that i use to test motors and breakin batts with that is set up with locked diffs. im currently using the tc3 as a test bed just to get aquainted with the onboard computer..
> i would like to see a way to graph 2 runs side by side to see the difference between 2 seperate runs to map how changes will effect..
> 
> hank any info on the g meter when it will be avail.....albie


If I understand this tool correctly - you can get the raw data out, which would let your manually build charts. With drag that would be cool, but with road, the graphs would get out of sync with crashes, traffic, etc. Unless you look at general trends; voltage early in the race and late, temps with different gearing, etc.


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## hankster

I am sure they are using something like that for their development. They have the G-Force (X & Y axis) and a lap timer in development now. No word on when they will be completed.


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## PizzaDude

Hank,
I seem to be unable to get rpm-numbers in?
magnets are placed a diff outrdive.
2 small ones with the black dot outwards.
sensor is about 1.5mm away!.
Amy thoughts?

pizza


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## hankster

Do you have the sensor pluged into the CDR properly? Are you sure you have the CDR set to record RPM? Do you have a the latest version of the software?


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## PizzaDude

I'll triple check and let you know.
thnx


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## sosidge

A good way to find the right placement for the RPM sensor is to run the unit in live mode before installation.

Move the RPM sensor by hand to find the point where it registers reliably, then work out how to stick it there!

The magnets should have the black ink side facing the printed face of the sensor.

Hope that helps,

Dave


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## albie

also make sure you enter all the gear ratio and tire size data i know mine acted up at first till i added all that info... albie


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## PizzaDude

HHEELLPPPPpppppppppppppp..............

Sorry guys, I checked everything but somehow all signal work OK.
Except no RPM at all?????

Any way to measure wheter the sensor is broke or anything?

Regards,
Pizza wo rpm


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## hankster

Contact Bill at [email protected] and he can take care of it for you.


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## albie

i spoke with bill 2 days ago he was leaving for a hobby show and wasnt gonna be back till next week.. albie


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## hankster

First, make sure you are using the latest version of the CDR software.. there were a couple RPM bugs in the previous version. Since I am not sure if you have a digital multimeter with a diode tester I will give you the follow ing info. While I am not sure the following test will tell you if the RPM sensor is good, radically different readings will let you know that it is most likely bad. Use a digital voltage meter set to read resistance and check the following.

Put the black lead (negative) of the meter on the black wire of the RPM sensor and the red lead (positive) of the meter on the red wire... reading should be approx. 33M ohms.

Put the black lead (negative) of the meter on the white wire of the RPM sensor and the red lead (positive) of the meter on the red wire... reading should be apporx. 26M ohms.

Any other combinations of hookups should show open circuits.


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## teamductape

would there be any way to synchronize the data graph from this recorder with video from a small camera(something like this http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=19164&item=5700583714&rd=1 ) mounted on the car


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## sosidge

The data from the recorder can be played back in real time - with the standard screen of dials and readouts.

So it should be relatively straightforward to synchronise the video with the readouts (all you need to do is find a way of doing a dynamic screen grab from the PC you're viewing the data on). This would have to be done after the run - the recorder doesn't send back live data from the car (yet).

The graphs are just created as a complete graph - they don't draw gradually - so you couldn't watch the graph draw itself during a run.


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## AZ_Ron

It would seem to be a simple thing to add an interface to the main unit that would allow you to use an SD card, or something similar to expand the memory, and thus the recording time...

I'm wondering how this would function on a 1/4 scale Sportsman car... RPM, EGT, etc would be very handy...

R


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## hankster

There are a number of 1/4 and 1/5 scale racers that are using it. The only real drawback is it is designed for only one RPM input. What I have found is that after 4 or 5 minutes of data is collected, the data become "unweldy" in that it is hard to graph all of the data even just to pick out the spots you want to look at. To get maximum time just record the items that are important... the fewer items you collect data on the more time it will record.


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## Fred B

Depending on what you want to log, you can get about 8 minutes of data from the recorder. I think I was getting about 7 1/2 minutes with 12th (recording servo's, rpm, amps, and voltage). This is more than enough data to see what the car's doing.

With the gas car, I set-up for servo's, rpm, g force and one temp. With those channels selected there's more than enough time. The cool thing is that the system really will measure 40,000 rpm at the flywheel.


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## hankster

*RC Car Data Recorder G-Force and RPM Sensor Mounting in a T4*

I thought I would pass on a few pics of how I am mounting the RC Car Data Recorder g-force and rpm sensors on my T4. I haven’t messed with the data recorder for awhile but figured I’d drag it out because I want to compare on-track performance between my own tuned stock motors against a couple “pro-tuned” motors that I recently received. I’m heading to the Region 5 Off-road Champs and figured this would be a good place to get some data to compare motors. Once I get the data I’ll post the results here.

*G-Force Sensor Mounting*

First you can see how I mounted the g-force sensor. I used a piece of plastic from bubble packaging. You know the plastic covering that you find on items you buy in your local department store…. It shows the item you are buying and you have to cut the darned thing apart to get it out. Lexan would also well if you have a spare piece lying around.
I just cut out a piece the same length as g-force sensor and formed it around the battery strap. When you clamp down the battery, it holds the sensor snugly in place. The advantage here is that you can shift the position of the sensor to match the CG of the truck. In this case, the CG is approx. over the 3rd cell of the battery pack.







Larger Pic







Larger Pic

*RPM Sensor Mounting*

With the RPM sensor, I wanted a place that would make it easy to remove. Ideally, you want to mount it close the motor but I couldn’t come up with a way to easily mount it and make it easily removable. So I decided to mount it on the rear outdrive. I superglued the magnets to the outdrive and then bent a paperclip to so it would screw to the transmission brace and hold the sensor close to the magnets.

This makes it easy to remove but has the disadvantage of not always giving true motor RPMs because of the diff action. Guess it’s a tradeoff that I’ll have to live with.








Larger Pic







Larger Pic

Hopefully this will give you a few ideas on mounting your g-force and rpm sensor when using the RC Car Data Recorder.


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## sosidge

Great pics Hank - it's a good idea marking the G-force directions of the top side... wish I had done that instead of continuously flipping the sensor because I'd forgotten which way was which!


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## hankster

The problem I had was the servo tape I used to stick it down ripped off the label. Luckly I had another so I could see which way was which.


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