# power supplies



## yellerstang (Feb 20, 2012)

Im looking for a decent power supply for my 1/8 mile Tomy AFX track drag strip. I want at least 18v and 20 amps. What do you recommend?

Can anyone explain the difference between linear and switching as it applies to drag cars pulling 10+ amps on launch
??

Thanks

Jesse


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## kartkid1 (Nov 20, 2014)

yellerstang said:


> Im looking for a decent power supply for my 1/8 mile Tomy AFX track drag strip. I want at least 18v and 20 amps. What do you recommend?
> 
> Can anyone explain the difference between linear and switching as it applies to drag cars pulling 10+ amps on launch
> ??
> ...



You could always use a car battery..lol 
Not sure how to go about hooking that up, but back in the day my dad used to do that at his track


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## Bubba 123 (Sep 10, 2010)

yellerstang said:


> Im looking for a decent power supply for my 1/8 mile Tomy AFX track drag strip. I want at least 18v and 20 amps. What do you recommend?
> 
> Can anyone explain the difference between linear and switching as it applies to drag cars pulling 10+ amps on launch
> ??
> ...



Mr. Alpink, Your "Services", are Needed... 
(Sir John Steed; The Avengers) :grin2:

Bubba The Senile :willy_nilly:


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## Rich Dumas (Sep 3, 2008)

If you are not using rewound armatures 20 amps should be plenty. You can calculate the maximum amps that a car will pull if you know the ohms of the armature and the track voltage, simply divide the track voltage by the ohm value of the armature, thus with 18 volts and a 6 ohm arm you will draw 3 amps if that much is available. That would be the starting amperage, once the cars start to move the amps will drop a lot. That is why a drag strip is a special case, your starts are a much more important part of the race.
My own track, which can be a road course or oval, uses a pair of Mastech 20 amp switching power supplies, each runs two lanes. I suppose that it is overkill, but I can run 12 and 18 volt cars during a single practice session, besides nothing exceeds like excess.
I thought that I had a good explanation of switching power supplies saved, but I was not able to find it. With a linear power supply the limiting factor is the transformer, which has to be good for the full rated amperage. A 20 amp transformer is a large, heavy and expensive item. With a switching power supply the transformer is much smaller, all it has to do is invert half of the AC wave form. The voltage is actually controlled by rapidly turning the power on and off. The motor would thus see a series of pulses if there was not a circuit to smooth those out. A switching power supply should be smaller, lighter and cheaper, not to mention cheaper to ship than a linear supply of the same capacity. So what is the downside to a switching power supply? It has been said that there can be an AC component to the output voltage, but that is also possible with a poorly designed linear supply. Another possible difference is that the voltage regulating circuit has to be more complex and might be slower to respond to changes in the load, but once again that can be a factor with a regulated linear supply. I did test my old laboratory grade regulated power supply rated at 8.6 amps by switching in various loads, with a 1 amp load applied the voltage dropped from 18.50 to 18.30. That power supply was a surplus item from work, a more modern one might have had a smaller drop, for my purposes it was good enough. I have not tested the Mastech power supplies. I had a matched pair of the linear supplies and the voltage display on one of those was starting to flicker, although the voltage output was OK when I checked it I decided to go for a new power supply. The old ones were donated to another guy in my club who uses them with an external volt meter. In researching power supplies I found that linear power supplies greater than 10 amps had become scarce. The Mastech switching supplies were specifically listed as being good for slot racing and were on sale, so I went with those.


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## Rich Dumas (Sep 3, 2008)

I took another look and found this in Wikipedia: https://en.wikipedia.org/wiki/Switched-mode_power_supply


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## yellerstang (Feb 20, 2012)

*amps*

Years ago we used marine batteries for 18v neo cars. Drag and road course. I want ample power, not going to batteries ever again... 

We have one car that pulls 10 amps on launch. I can see others doing that too.

My concern on the power supplies... I use a switching power supply to supply power to my chargers for my rc model airplanes. I fly electric planes, the batteries take some amps to charge. My switching power supply spools up, on demand. You can hear the fan speed increase with the load.

I dont want any waiting for my 10 amps or more. I want it NOW. So... you can see why I am concerned about this. I would love to hear from guys who are running some hot slots, just how much power and what type of power supply are you using?

The scary part of this for me is this... My friend has an adjustable 0-30 volt, 10 amp $110 power supply. It cant handle even my 3 ohm arms with poly magnets in my tjets. It trips the internal circuit breaker.

My very old industrial (large and heavy) 5 amp rated power supply can handle the cars at the same voltage, no problem. It cannot, however, handle a hot neo type car.

I want to spend my money to get what I need, and spend it just once....

Thanks to those who are replying to this. I appreciate the feed back.


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## Milton Fox Racing (May 27, 2014)

I am not even a novice as to drag track racing, but was wondering about your track design and the impact its design has on your power needs (problems).

I am understanding it is an HO scale - so around ten feet long?

Only two lanes?

How many track segments (gaps) does it have?

How many taps do you have to the track?


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## yellerstang (Feb 20, 2012)

Its 1/64 scale, so a bit over 10'. I have power taps at both ends of the track. I may solder the joints at a later date, if power is an issue.

The track is all brand new, its clean and running ok. I want to polish all of the rails again with 1000 grit, then 2000 grit to finish.

2 lanes. Every connection is 16 gage stranded wire.

This aint my first rodeo....


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## Milton Fox Racing (May 27, 2014)

Understand, my electric work is at lower voltage and amp and much longer distances. And I didnt know what your set up was like.

How many joints is it you would need to solder?


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## alpink (Aug 22, 2010)

aren't joints smoked?


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## yellerstang (Feb 20, 2012)

*track connections*



Milton Fox Racing said:


> I am not even a novice as to drag track racing, but was wondering about your track design and the impact its design has on your power needs (problems).
> 
> I am understanding it is an HO scale - so around ten feet long?
> 
> ...


I didnt count them, but its 10'7" or so... divided by 15" straights... my head hurts. If I need to solder them up, I will. Until we get a decent power supply and really start running some hotter cars, it shouldnt matter too much.

The bottom line, I can race anything really fast (by my standards) until I get a decent power supply.


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## alpink (Aug 22, 2010)

Jesse, I think Rich's explanation is pretty complete and certainly more than I can relate.
it appears that you will have to spend a little more than you want if you expect to supply two 10 amp drawing cars simultaneously. 
try to find DRHOE online and see if he can answer some questions.
they race EXTREME builds and I am sure the amp draw is significant.
they use a power supply I am not familiar with.
I haven't raced with those guys in a good many years, but i am sure that Steve Geary would be happy to help you out.
just do not mention me. he really doesn't care for me at all. LOL
bottom line, as much as i don't like it, but I used automotive batteries previously, two 12 volt with 990 cold cranking amps each, that would always supply ample amperage and the two 12 volt in series provided 24+ volts allowing us to race anything created.
I guess if you change your mind, a 6 volt and a 12 volt in series would work well. 
I used just such a set up before i got attracted to running 24 volts.
you must disconnect the jumper between the positive and negative terminals in order to charge them.
otherwise, just pay the large price for a really good power supply. I think the cost might be in the same range as two good automotive batteries and safer in the long run.

on a side note, I have been reviewing race results from when i used the batteries and now with my variable 30 volts variable 10 amp power supplies and ETs are comparable.
we haven't raced any "outlaw" or EXTREME builds in the period of time and certainly not recently, to make those comparisons.


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## Milton Fox Racing (May 27, 2014)

yellerstang said:


> I didnt count them, but its 10'7" or so... divided by 15" straights... my head hurts. If I need to solder them up, I will. Until we get a decent power supply and really start running some hotter cars, it shouldnt matter too much.
> 
> The bottom line, I can race anything really fast (by my standards) until I get a decent power supply.


As I noted above my volts and amps draw was low and slow, but IIRC I used a tap for every 7 to 10 gaps. If my math is close you at most have 8 gaps.

I am not an electrical engineer either, but have you tried running with just one tap connected at a time to see if there is a difference in performance (or problems)?


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## yellerstang (Feb 20, 2012)

*power*

Al and company... thanks for the replies. I think I can get a new power supply for about $200, they turn up used on ebay for about $120. I dont need crazy power, I just want enough to run anything we can without pulling down the power supply. I have found a few to pick from. 

Jess


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## Rich Dumas (Sep 3, 2008)

If you are going to run cars with rewound armatures and neo magnets it would be normal for those to pull more than 10 amps at startup. In that case if it was me I would use either a single 30 amp power supply or a pair of 20 amp supplies. If you want to go crazy buy one of these Astron linear supplies, they only weigh 49 pounds. I would also use 10 or 12 gauge wire.
https://www.dxengineering.com/parts/asr-vls-35m
If your power supply can't supply enough amps one of several things might happen. First off the output voltage might drop well below the set point voltage. Secondly the current limiter might kick in, depending on the circuit design you could also get a voltage dip or you might have to reset the power supply. If the high current condition lasts for very long you might blow a fuse, burn up your power transformer or burn out one or more of the transistors in the voltage regulator circuit. It is not a bad idea to have a fast acting fuse or circuit breaker for each lane. The closer to the maximum amount of amps that you expect a car to pull the better off you will be.


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## alpink (Aug 22, 2010)

power taps and amperage carry...........
be sure to understand that amperage runs on the outer molecules of conductor.
so .... there are more paths on fine strand (think Monster Wire for music systems) wire than the same gauge solid wire.
also, multiple taps provide more access to said amperage than few or no taps and the voltage AND amperage trying to carry down thin steel rails and through poor conducting connections at each track section.
on 1/64 scale 1/4 mile drag strips, I like to use one 4 gauge common and two 8 gauge individual lane from controllers to just past the finish line.
On my portable 1/4 mile i had to compromise somewhat and used large gauge extension cords for the ease of assembly and disassembly. 
the sections are 6' long with a tap in the middle of each. additional tap just past the finish line and one at the very beginning of the track.
so power only needs to flow a maximum of 3' in any direction on the continuous steel rails.

there are many thoughts to power taps, and this is just my take.
I do tend to go a tad overboard with these things! LOL


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## Milton Fox Racing (May 27, 2014)

Al described what I was hinting at but coulndnt remember the technical terms to describe. As short as the OPs track is a single tap in the middle may work better or adding a third tap in the middle even better, but with smaller guage stranded wire as Al notes. :cheers2:


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## alpink (Aug 22, 2010)

https://www.circuitspecialists.com/csi3020sw.html


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## aurora fan (Jan 18, 1999)

I just always ran my 60' 4 lane on 4 wall warts and never noticed a problem. Is this because I don't miss what I never had or is this something I should look into in the future? I run Tjets and 70's AFX. I realize this was about dragstrips but wanted to ask. I never saw the need for fancy power supplies but we're just garage rats anyway. Drinkin' beers, havin' fun.


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## yellerstang (Feb 20, 2012)

*power*

If you are running stock cars, you can get away with a power pack per lane. In long layouts, you would definitely see a power drop, even with the older 6ohm AFX cars.

I have a 55+ Tomy AFX track, 4 lanes, all new.... I have a heavy duty, industrial regulated power supply that is rated for 5 amps. That power, along with jumpers in my track, is sufficient for my Tjet racing. When one car deslots, there is a slight boost in power to the running cars. You can see it.

But, for our racing, this is fine. When I get my power supply for the drag track, I will likely use the same unit for my road racing too.

Hot cars draw power, several hot cars draw LOTS of power. Tjets only pull about half and amp on launch, if that and certainly less to maintain speed.

So, it just depends on your needs...

If you tried to run a really hot neo type car on a stock track with stock factory controllers, it would probably just smoke the controllers. The big demand for power needs big power to make it work.

I want the power...

Jesse


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## alpink (Aug 22, 2010)

you remind me of a man 
....... what man?
the man with the power
....... what power?
the power of hoodoo
....... hoodoo?
you do
....... What?
remind me of a man 

.
.
.
.
.

:wink2:






.


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## Milton Fox Racing (May 27, 2014)




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## yellerstang (Feb 20, 2012)

I agree with Joe Isuzu! Nice to see Al and his humor.


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## Dyno Dom (May 26, 2007)

Does anyone have a Mastech power supply? I'm considering the adjustable 30 Volt, 30 Amp unit for my 6 lane road course to replace my existing unit and would appreciate input.


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## Rich Dumas (Sep 3, 2008)

Here you go.










Two 0-30 volt 20 amp Mastechs. They call their switching power supplies Volteqs.
In an earlier post I stated that you could calculate the maximum amps that a car could use, I have also done readings with a Tyco 440X-2 going around the track. It takes a special meter with a peak hold feature to measure the actual starting current, to get the running amps I pointed a video camera at the power supply amp display and ran some laps. The car was pulling 0.5 amps as it accelerated off of a corner and 0.25 amps when it had reached top speed. I also tested T-Jet type car with a Dash 4 lamination armature that measured about 4.5 ohms. The track was in its oval configuration and the voltage was set at 18.5. I saw 0.2 to 0.7 amps as the car circulated around the track and 1.2 amps when the car started from a dead stop. Note that the display shows time averaged values, otherwise it would be flickering and you would not be able to read it. Maybe this link is still working.

http://vidmg.photobucket.com/albums/v12/RichD/Movies/Dash Armature Amp Test_zpsfeozjs2u.mp4

Set type power supplies are good for less than an amp, in addition they are not regulated, so the output will change as the amps draw changes. Having a separate supply for each lane will eliminate the power surge that you get when another car comes off, but your voltage will not be constant. I once tested an old Aurora power supply, that read 19 volts with no load and dropped to 14 volts with a 0.55 ohm load. I call that the poor man's traction control, it makes the car's response a little soft, so low downforce cars like T-Jets will be easier to drive.


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## yellerstang (Feb 20, 2012)

*MORE Power*

I pulled the trigger on a nice power supply, 0-30 volts and 0-30 amps. Digital, not linear, but it should do the job. This should be enough power for anything that I can throw at it.


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## alpink (Aug 22, 2010)

*share*

do you mind sharing source?
pic?
link?
please!
:grin2:


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## Dyno Dom (May 26, 2007)

I'm waiting for a Mastek 30V/30A PS to arrive.


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## yellerstang (Feb 20, 2012)

Ebay. $269. I just couldnt go with my 5 amp linear anymore....


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## beast1624 (Mar 28, 2009)

Bought my 30V/20A Mastech from here @ 5 years ago for our 112' 4 lane Tommy track. Still going strong. Very satisfied.

Switching DC Power Supplies - Best Deals on Mastech Variable DC Power Supply


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## slotking (May 27, 2008)

I picked up:

Ridgeyard DC Power Supply Variable, Adjustable Switching Regulated Power Supply Digital, 0-30 V 0-10A with Alligator Leads US Power Cord
Be the first to review this item 
Price:	$59.99 & FREE Shipping
From Amazon

but I use it for my dyno.

I have a 68amp unit for my track


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## Rich Dumas (Sep 3, 2008)

I did check the regulation of one of my 20 amp switch mode power supplies. Changing the load did not affect the voltage at all, my old Lambda linear supplies did have a slight drop as I mentioned earlier. With a different make your results could be different.


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## Post442 (Mar 23, 2008)

*Power supply*

I just updated to a TekPower TP3030E 30V 30A this season and I am very happy with it. Got it on Amazon. Replaced my MG PS10AD 20V 10A which worked great for many years, except for NEO cars. For that, I used batteries. Having a couple of old cars that I don't drive in the winter, I would use a 12V out of one of the cars and buy a 6V every 5 or 6 years. (not stored in the house) Glad to get away from batteries. I didn't see it mentioned, I recommend using a relay to turn the power on/off instead of the power supply switch. The added cycles may damage the power supply over time.


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## Rich Dumas (Sep 3, 2008)

I use a 15 amp wall switch to turn my power supplies on and off, they are plugged into a dedicated 20 amp circuit. You should be aware that a 30 amp power supply will not pull 30 amps from the wall when it is operating at full capacity. The maximum would be about 8 amps.
Batteries can be a pain in the neck. A towmotor battery at a local track drooled on the carper and made a hole in it. Local fire codes usually prohibit charging lead acid batteries indoors. The ones at the track were on shop creepers and were supposed to be rolled outside to be charged. Of course they never were, the fire marshal never checked up on that I suppose. In the event of a fire the insurance company might refuse to pay up if it was determined that the batteries were a factor.


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