February 10, 2005

Slotict’s Track Designs

Power Center from Professor Motor Install

And a bit more…


September 24, 2004

Revised: February 10, 2005

Rand Fredricksen

















My track is 54.57 feet of 1/32 2-lane Scalextric Classic road-course with five power taps. I am using Professor Motor HO & 1/32 Super Low End Sensitivity Model Electronic Slot Racing Controllers, 2043, with the low cost variable sensitivity system installed.


I had been using two surplus paper shredder power bricks rated for 1.5 amps at 15 volts. Unregulated, they produce 22 volts with no load. I built a pair of voltage regulators, but I knew that when a high load was placed on the supplies the voltage was dropping below the setting I used most often, 18 volts. My track is wired directly to the rails using plug-in booster cables that Scalextric sells. I cut them in half and solder alligator clips to the ends. Then I have twin-lead wire for each lane with alligator clips on one end and several places where I have stripped the insulation and tinned the wire that I clip the booster cables to. So I have no power base.


Booster cable

Clipped to power feed



Last week I received from Professor Motor a new power supply (DPS400GL) and the Professor Motor 2 Lane Power Center (PMTR1072), as well as two post kits ((PMTR1075) for connecting alligator clip controllers. Eagerly, I set the power supply on the floor and hooked it to my homemade hardwiring conglomeration.


My old wiring was on a barstool.


I didn’t notice any immediate change, that is, the cars were not seat-of-the-pants faster. As I put more laps behind me I realized that the cars were easier to control. The voltage-dividing controllers now have a constant voltage supplied and are therefore more proportional. I am happy!



I had to get the power supply off the floor. I thought of buying a large project box to install the power center and controller hook-ups. But I still needed a shelf to support the power supply. I could use another shelf to support the project box. And shelves are good to have anyway! I found a plastic unit with 4 - 22 X 14 inch shelves for less than $10US. It snapped together with standard 1½” ID plastic pipe as the vertical members, very easy to cut with a hacksaw to adjust the height. Forget the project box, I can mount the controller posts right to a shelf!





I did not want the controller connectors protruding from the front of the shelf and I did not want them on top. People have been known to stumble occasionally around the slot car table. The power supply should be low because it is heavy, but this is in my basement so I didn’t want it just above the floor. The shelf unit was designed that the bottom shelf sat on the floor, I used some 3” pieces of pipe to raise it. If this was upstairs I would have put the power supply on the bottom and the power strip next to it, or perhaps fastened to one of the uprights.


I made the second shelf 7 ½” above the bottom shelf, enough to clear a power strip and some small power supplies. The shelves are 1 /12” thick in this case so that left 6” of clearance. The height of the third shelf was determined by the height of the fourth shelf. The fourth shelf needed to be just enough lower than my table to store the controllers. I decided 3” would be enough so the top shelf would be 29”. I set the third shelf, containing the controller hook-up posts so I would have 3” clearance, so it is 4 ½” below the top shelf. The distance you want from top of shelf to top of shelf is the length to cut the pipes.


The power center will be mounted on the bottom of the third shelf with the controller posts fitted to the front of the shelf and the outputs to the track on the back of the shelf. A pair of wires will drop to the power supply and be attached to the screw posts that double as banana jacks on the power supply.


There is a wide variety of sizes and number of shelves and colors available. Think about what you want to put on the shelves, use the appropriate number of shelves, and space them accordingly.


Power Center


I used zip ties to attach the connector block to the bracing through a pair of holes I drilled in the shelf bracing. Because the terminal strip was wide enough to span two braces I mounted it that way. Hot glue does not stick to any of these plastics; I tried.


I like to mark the wires and circuit breakers with red and blue electrical tape to sort the lanes according to the colors of my controllers.


The instructions from Professor Motor were easy for me to understand.


Underside of third shelf (upside down, so left is right)


I then determined the spacing for the controller hook-up posts. I wanted to be sure to avoid the shelf bracing, so I divide by two to get the first and third post spacing. I divide again by two to determine where the center post would go. Then I centered the 2nd and 3rd posts on a brace. In my case the braces were 3 ¾” apart so the post spacing was 1 7/8”. The first post was then set 15/16” to one side of a brace, the next two spaced 1 7/8” from the previous post. This worked out well with the colored disks being just under ½” apart.


I determined that 2” from the front of the shelf would work well and carefully marked and drilled six holes from the top. Drilling from the top leaves any burrs on the bottom.


I selected a red 14 gauge solid wire, bent it to the general shape to connect a red post to the power center and cut it a bit longer than I thought it should be. I soldered a supplied wire terminal to one end of it. I put a washer on one of the post screws, slid the wire connector on, pushed it through the correct hole and added the plastic colored piece, another flat washer and a lock nut.


Because the posts come with locknuts they are difficult to turn by hand and the posts are pretty long. Since I didn’t have the proper nut driver on hand I selected the correct socket and inserted a slotted screwdriver bit in my cordless drill. I found that, as long as I went slowly, I could hold the socket with my fingers and allow the screw to penetrate the orifice on the socket designed to attach the socket to a ratchet. I didn’t tighten the screw and nut yet, just brought them close together.


Top of third shelf – controller posts


Bend the wire more exactly, cut it, attach a connector and screw it to the power center.


Repeat for the other red wire and the two white wires.


Track Connections

The black wires run directly from the controller posts to the track outputs.


Determine where you want the outputs to the track to be. Because it won’t be readily seen I didn’t do any measuring and marking for these, I just eyeballed them in… You need two outputs for each lane, positive for the right rail and ground to the left rail. I wasn’t worried about these sticking straight out the back because my shelving unit is under the table. You might rather have them come straight up, like the controller posts.


The white wires to the track are connected to the power center.


The Professor Motor site doesn’t indicate selling extra posts with hardware for the track outputs, as most people want to direct wire to the track. I wanted to use posts and alligator clips though, so I will need to trip over to the hardware store this afternoon and purchase four more brass screws and the associated hardware. For now I just pushed the wires through the screw holes I drilled and hot-glued them. Bought the hardware, here’s another picture.


Out to track with hot glue – black to right rail (red lane.)

Blue lane connected to the brass track posts.


Power Supply

Route a red and a black from the appropriate positions on the power center so they can connect to the output on the power supply. Cut them and solder a connector to one end of each and connect them to the power center. I drilled holes in the braces and zip-tied the wires so they won’t sag.


Tighten all the controller posts and output posts. It is better if you can tighten the nuts (always is) rather than the screws, but either way should be okay in this case. Be sure the wiring center screws are tight.


I used solid wire so most of it stays where I put it. If you used something softer you may want to fasten some of the longer ones to the braces.


The colors used on controller connections are not the same as used in conventional electrical connections and can be a bit confusing if you are used to thinking that red is positive and black is negative, just follow the instructions and you will be fine. I like to remember white to wall (power), black to track, red to stop.


Don’t forget to leave some extra length in the wires to the power supply to have some play.


It can’t hurt to check the torque on all the screws before you button things up.


Put the shelves together, connect the track to the outputs, clip your controllers to the posts, connect the power supply and plug it in.  Switch it on and Go Racing!



The white posts are connected to the positive output of the Power Center.


The black posts from the controllers go directly to the right rails on the track. These are the positive, right rail, connections.


The red posts are connected to the Power Center and through circuit breakers are connected to the left track rails (ground.)


The right rails are connected directly to the black posts.


The left rails are connected to the power center.

Power Center:

The white and red controller posts are connected.


The left rails (negative / ground) are connected.


The power is connected from both plus and minus power supply outs.

Power Supply:

Connected to the power center.


Computer Controlled Track Power

I installed an on/off relay in line with the positive power from the supply so my timing computer can control the track power. To do this I cut the red wire between the power supply and the power center and attached each end of the cut to the normally open contacts on the relay. The relay I used had solder connections on the bottom for the control (low voltage) so I soldered the computer controlled wires to those. The top of the relay had push connectors for high power and I soldered the wires to such connectors. I hot-glued the side of the relay to the shelf bracing. That didn’t stick, I now have a zip tie holding it in place. I paralleled the relay with a toggle switch so I can have power without booting up the computer. Because of the bracing of the shelf the override switch had to be offset from the center. Usually you will have enough wire to add this relay later without a problem, but you might want to leave an extra loop of wire if you think you might install a relay later.


Power relay and bypass switch


Brake Switches

I toyed with the idea of installing reversing and brake switches, but since I am using alligator clips one can simply unhook the brake (red) wire.

Challenger Car

Disconnect a controller and use a jumper with alligator clips to connect the white and black posts. This will give you full power in that lane.

Reversing Switches

In my case the track rails are connected with wires ending in alligator clips. Reversing the red and black clips to the control center output on any lane will reverse the direction of the cars on that lane. It will not affect the positive/negative to the controller.

Lane Selection

Swapping the track connection pairs to the other outputs will swap the lanes relative to the controllers. You can connect both lanes to one controller for practice laps. You can set a car on either lane and use one controller to move them.


Rear of complete unit



Computer Control

Now that I have the track power rat’s nest sorted out and off the floor I decided to do the same with the wires that connect my timing computer to the sensors, power control, and starting lights.


I hot-glued the computer-controlled light and power box to the top of the wiring shelf. It came loose 5 times so I drilled a few holes through the shelf and zip-tied it in place. I zip-tied the parallel port cable to the shelf and plugged everything together. Another zip tie was used to keep excess wire off the floor and a few twist-ties were used to make things a bit neater. I know, another distracting background. What is an amateur to do?


Reinstall the top shelf, push the unit under the table, and voila, nice and neat J


Rear with computer controls installed

Front of completed unit


Track Call

In the latest update to SRM Mario has included the ability to read a button press to halt a race by cutting track power. I had a large white button I mounted front and center of the top shelf.


Track Call button.




Wiring the control center was made simple with step-by-step instructions and the block diagram supplied. Two wires go in from the power supply and two wires come out for each lane. The three wires from the controller are demystified. I love it when a plan comes together J


The Professor Motor wiring center and the controller connector kits contain everything you need to quickly and simply wire your slot car track in a safe and skilled manner.


Questions or comments: Slotict@UX5490.US

Thank you,

Rand Fredricksen

Copyright 2004-2005