# Driver's Station/Controller Adjustment Circuit



## Dslot (Sep 2, 2007)

I'm planning a small road course layout and I'm considering building driver's stations that would extend the response range of 40 to 60 ohm set controllers (old Aurora or Tyco) to give them better low-end control with ThunderJets, JLs and old AFXs and Aurora 20-22 V power packs, one per lane. Does anybody have experience with or comments on this circuit - 
Cheap and Easy Adjustable Voltage?
It simply lowers the output voltage incrementally by dialing various numbers of diodes into the circuit, each dropping the voltage by .7 V. I realize that top speed will decrease as you dial up, but low-end control will be improved, better for a tight road course. Theoretically, by changing the setting, you could find the right balance for your driving style with any particular car.

Any thoughts are welcome. Thanks.

-- D


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## AfxToo (Aug 29, 2003)

The diode based voltage stepper is a neat idea. (Incidentally, that's the basis for the original Professor Motor controllers except they use much heavier diodes.) A rheostat that can handle the same current would be prohibitively expensive. Just make sure you use a fuse or circuit breaker that's rated for *less *current than the max diode current. This will give you per lane voltage control, which is nice for some younger racers who use a controller as a toggle switch. You may even be able to use it as a handicapping feature to even out the field when you have a disparity between racers.


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## SwamperGene (Dec 1, 2003)

It's not a bad idea, I've done it on the fly with jumper wires, alligator clips, and rectifiers. I don't think it gives quite the same feel as regulated voltage, though. Personally I've always wanted to try a choke setup but the only person I know of that's done this successfully now makes controllers with the magic built in so I don't think he'll divulge the specs. I have an old SlotWorks controller, SN 026, which is likely what AFXToo is refering to as the basis for PM (early PM's had "SlotWorks" on the handle, too), this uses a bank of square rectifiers which by design allows dual polarity.

Speaking of polarity... this just reminded me, before you get started, most stock set type terminal tracks (cars going left to right) are configured as "negative gate", ie the positive side is common. Something to keep in mind if you put diodes in.


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## AfxToo (Aug 29, 2003)

The wiring diagram that's shown on the link for the stepper switch and the drivers station is *positive *polarity. Most everyone outside of the UK and really old timer 1:24 guys wire their tracks for *positive *polarity. I've never encountered a negative polarity track in my lifetime, but they do exist. 

The wiring diagram shown on Steve's page (and hoslotcarracing.com) are good examples of *positive *polarity wiring.

http://home.comcast.net/~medanic/Wire_Perform.htm


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## SwamperGene (Dec 1, 2003)

Never? Stock Tyco terminal tracks are negative gate. Stock Tomy (cars running counterclockwise) is negative gate. If you are using stock terminal tracks, this is something that would need to be considered, and checked, if putting inline diodes into the system, especially if you are using positive gate wiring diagrams.


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## Hornet (Dec 1, 2005)

Look around your local surplus store for a big ole 1 ohm or lower resistor,you can get them with a sliding band on the resistor,hook this onto your black track feed (positive polarity),then hook your controller to the sliding band and start adjusting away,you've just put a choke on your track.
In laymans terms,a choke is nothing more then a resistor on the power out side (black wire to rail) of your controller ,if you put the resistor inline with the power-in feed (white wire to your power supply),it becomes inline resistance :wave: .
Basically a choke softens the trigger output response :thumbsup:
To do it with stock set controllers you'll have to do some modifying to the plug-in so that you can wire the resistor inline with the track rail feed


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## SwamperGene (Dec 1, 2003)

Rick the way I gathered it from some of Steve's documents is that a choke is much more sophisticated than a simple resistor. As an inductor, I believe it's resistance is based on load, throttle up at full load (ie starting line) it softens that initial punch, but if your cruising down a straight and nail it the choke is essentially "out" of the circuit. 

That's the way I took it anyhows. :freak:


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## Hornet (Dec 1, 2005)

LOL,don't worry Gene you're not the only guy misled by that statement.
Steve and i had a discussion awhile ago about his wording,as he leaves it very misleading,nothing hi-tech really about a choke.It basically removes itself,the faster the car goes,less amp draw by the car as it speeds up,means less resistance is generated by the resistor,ideally to totally remove the resistor you just have to bypass it when you hit full travel on the trigger,easily done in most controllers.
When you pin the throttle is when the car draws the most amps,as it gains speed it's amp draw dimish's,nullifying the resistors effect the faster the car goes,and if you bypass it at the top-end it's removed from the circuit
Chokes have been around for years,long before we had anything electronic,i've built them out of old "pop" cans with several wraps of wire,you just hook an alligator clip on to the wrapped wire,depending on how much resistance you need :thumbsup: 
Hey how are you feeling these days Gene,don't see you posting much lately,and was wondering if you're still alittle under the weather. :wave: 
Rick


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## AfxToo (Aug 29, 2003)

That correct, I've never run on a track with negative polarity. But it is important to note that diodes are polarity sensitive and the way they're being used here is in forward biased mode, which means they are conducting. If you hook your power supply up backwards (negative polarity), the diodes will be reverse biased and not conducting. The stepper will simply not work unless all diodes are bypassed. Fortunately, this is very easily detected and very easily corrected by switching the supply leads.

It does not matter whether you wire your track for positive or negative polarity, but you must be absolutely certain that you KNOW how your track is wired so that anyone using your track is fully aware of its polarity. 

Knowing the track polarity is extremely important with semiconductor junction based (PM) and transistor based controllers (Difalco and others). The worst possible thing you could ever do is provide direction reversal by switching the polarity of the power supply feed to the control station, which is exactly what Tomy does. This technique is only safe for resistor based controllers. If you want to provide direction reversal, do it in the connection from the control station to the track. The wiring diagram that Steve shows is correct.


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## Dslot (Sep 2, 2007)

Wow. Thanks for all the info, guys. Sorry to be so long in replying, but I've been trying to make sure I understand it all, and rereading some of the Siberian Racing Team tech pages that you linked to. I'd read them before, but rereading them in light of my later knowledge and your comments is helpful.

Just checking, Hornet. You did mean a one (1) ohm or lower resistor, right? And by "lower" you mean like half or 3/4-ohm?
-- D


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## Hornet (Dec 1, 2005)

Yup the lower the better,usually about all you'll ever need to dial in for choke is at the most a 1/2 ohm of resistance,it doesn't take much resistance to soften the output response of the controller,and try to get a fairly big ceramic based one,they will run hot.
If you hunt around,i think you can still find articles on how to build yourself a homemade choke,the 1/24th guys have had chokes since the 60's,so they might be the best guys to look to for info,if you want to build your own :thumbsup:


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## Slott V (Feb 3, 2005)

All good stuff here DSlot, and probably the most important point in wiring your stations:

If you incorporate directional switches, make sure they are wired AFTER the controller input. The polarity input to the controller should never change. That way if guys come over with electronic controllers there is less concern for damaging the controller. Also, if you don't wire in a brake circuit, most guys with electronic guns won't be able to race. Professor Motor controllers will let you run without a brake wire hooked up and some have the LED polarity indicator, but the DR and Theisen need the brake wire hooked up to run correctly, as well as requiring positive polarity. Not sure about Steve Medanic's M-Magic or others.


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## Brixmix (Dec 2, 2007)

The Difalco and M-Magic can be run in 2 wire. I have both and have used them in this mode and both can be switched from + or -


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