Thanks for the great question. This question is one of the most commonly asked questions by racers when first experiencing polarity sensitive electronic controllers. Please click on the "email us if questions link" below if you have more questions that are not adequately covered by our response.
Professor Motor Controller Frequently Asked Questions
Question : I just received a new Professor Motor controller, but I have a problem when hooked up. The problem is that I have to depress the trigger of the controller all the way on before a car even moves ! Has anyone had a similar problem ? Do you pretest these controllers before you ship them or is it possible that I have a faulty one? Is it possible that my track is wired incorrectly ? My track works correctly for a Parma resistor controller.
Response : The difference between a Professor Motor controller and a conventional Parma controller is that we use electronic semiconductors in place of resistive elements. This feature does give our controllers a number of advantages, but unfortunately does cause a problem with polarity sensitivity. The following schematic illustrates a track wiring configuration that is "negative" polarity and would cause the "nothing but WOT" problem :
There are a couple of possible solutions for the polarity issue :
1. You could revise the track polarity. Directions for rewiring track to + polarity follow ....
Negative lead from power supply :
Wire to brake (red) post, ideally
through a circuit breaker (2 to 5 amp max recommended).
Also wire to left side of rail or
braid (considering car travel) .. each lane in common.
Positive lead from power supply :
Wire to white post at controller
stations
Black post at controller station
:
Wire to right hand side of rail
individually for each lane
Sounds harder than it is ... should take 1 hour to 1 1/2 hour total per track.
2. You can revise the controller polarity :
We have a kit coming out this summer with a reversing switch and a special brake circuit contact. This will allow use with either + or - polarity & can be switched to either as the track requires. (Available July 2001)
Question about pretesting : All of our controllers are 100% tested on our 4 lane basement club track. Each controller is given a lap or two with our orange MPC Mako Shark test car just to make sure the quality is what is should be. Since the process of building one of these is very involved with a great number of steps, we feel we will always do this to help prevent any customer issues. One day I even found we had soldered an alligator clip shut !!