# Electronic controllers



## mking (Apr 25, 2000)

I recently bought an electronic controller from Trek Lawler (a fray guy from the Kansas City area). Very nice controller that I enjoy very much. 

I've been tuning a lot of JLTOs lately, and I have several different controllers attached to different lanes on my track. Treks controller has a coast feature which will actually drive a car around the track at a fairly modest pace. I use this to break in a car after its tuned, while I'm at my workbench tuning another car. After awhile, I was noticing that cars that seemed to be running very smoothly using the coast feature on the electronic controller didn't seem to drive very well at all using a resistor based controller (my other lane had a New Jersey nostalgia hobby 120/100/80 ohm Parma controller). 

I verified that cars that drove very very well using the electronic controller didn't drive very well using the resistor controller. I was able to improve lap times by more than 15% simply by switching controllers. 

One thing I really don't understand is why the car should be smoother with the electronic controller. That is, with the resistor controller the car seemed to surge, almost as if the drive train was not smooth and there was a gear binding somewhere. That all went away with the electronic controller. 

Also, some cars had more power with the electronic controller than with the resistor controller, even when the resistor controller was in the full wide open position. That doesn't make sense to me, because it seems that the top end should be the same regardless which controller is used. 

For example, with one car I could basically drive around the track with the resistor controller in the wide open position. Car didn't seem to run very well. Switching to the electronic controller, the same car was a joy to drive, and I had to be careful in the turns to prevent deslotting. 

I switched the lanes the controllers were being used on, to make sure that I didn't have a problem with one lane. It wasn't the lane, it's the controllers.

Anybody have an explanation for this? Do I need to go buy more electronic controllers (ouch, $135 a pop).

Thanks
Mike


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## AfxToo (Aug 29, 2003)

Why a difference at full throttle? 

Transistor based controllers have a very small amount of current in the control part of the circuit, the part of the circuit affected by the trigger. This low current controls a large power transistor that sends power to the car. 

(A transistor is kind of like a water valve, and is basically a solid state version of a vacuum tube. Vacuum tubes are even called "valves" in the audiophile arena. The control part of the circuit is kind of like a valve gate and the trigger is like the knob.) 

The power transistor drops a little voltage, but the large reduction in power losses in the controller more than make up for it. Power losses are proportional to the _current squared_, so reducing the current in a controller that has a certain wiring and contact resistance at full throttle has a noticable benefit. Less power loss in the controller means more power delivered to the car. (fyi - this is why power transmission lines use very high voltage, like 200,000V to 500,000V volts plus, but at a low current to move lots of power around the grid.)

A resistor controller sends full current through the control part of the circuit. This results in far greater power losses in the controller even at full throttle. If you were to try using a resistor controller to break in a car like you do with the coast pot on a transistor controller you may burn down your house. Never leave a resistor controller with the throttle locked in a mid range setting, it will heat up like a toaster oven.

I can talk about the sensitivity characteristics of a transistor based versus resistor based controller later if anyone is interested. I believe it's been discussed in recent controller related postings.


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## tjd241 (Jan 25, 2004)

*Ouch is right...*

$135? I try to follow this stuff...trends, better gear, parts, etc. Then I see the cost. OY ! ! :freak: Maybe its me but sometimes it isn't as fun when a big price tag is tied on. Shoot... take a look at my keyboard. I gotta keep it simple man... tjd


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## AfxToo (Aug 29, 2003)

If you want to run a lot of different types of cars with one controller the higher cost electronic ones make sense economically. A Parma will set you back $25-$50 each and if you run 4 or 5 different types of cars then the $125 controller can be justified. If you run one type of car and are looking for a 10% performance improvement then it becomes a harder decision. 

But for hardcore racers a 10% improvement is HUGE. The difference between winning and losing a race are usually fractions of a percent in terms of lap/distance totals. If the second place car in the Daytona 500 came in 50 miles behind the winner that would be a blowout. Racers are willing to pay, and pay big, for fraction or a percent improvements. That's racing.


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## Mike(^RacerX^) (Mar 15, 2003)

I have a big pile of Parma Econos.Some 25's,45's and a few 120's.

I bought myself a Professor Motor,I believe it was a 2050 model for Xmas.

I absoloutly LOVE my PM controller!!!!!!!! I just cant say enough good stuff about it.No controller enhanced my HO slot car racing like that one did.

If I had it to do all over again,I would have spent my dough on four of those.For what It cost me to buy all of the resistor ones I have,I probably could have,had I known.

Mike


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## ramcatlarry (Oct 25, 2005)

And the new Platinum series transistor controller lists for $120 - in two versions. HO/homeset and light commercial duty. The control circuit resistance is for different ranges with the commercial duty BEST suited for High end HO, Falcon and 16d (30 guage wire) motors. I am sure a coast circuit can be added to either, if wanted.


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