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Scalextric Sport
 Race Start Controller

 Kit484K Supplemental page

  • Overview

  • Schematic

  • Construction

  • Important notes

  • Firmware



The original Race Start Controller project includes a PCB layout for those that wanted to build it themselves.  However the PCB has never been available to buy from Picprojects. In 2010 I designed a new multifunction PCB, and the original Race Start Controller has been modified slightly to work with this PCB.  The hardware design is essentially the same, the firmware functionally unchanged, the only modifications to the code being the I/O since different pins are used to accommodate the design on the PCB480.  You can read more about the PCB480 design here

This page provides construction details for the new PCB and provides information on specific differences. It connects to the Scalextric throttles in exactly the same way as the original version and therefore rather than duplicate the information here you should refer to them main project page for assembly and connections to your slot car setup. (back to main page)

You can buy a self-assembly kit of parts from the Picprojects eShop


This schematic is for the version of the Race Start Controller assembled using PCB480 and sold as Picprojects kit #484K.

Download schematic PDF


Construction details are shown below.  You can buy the PCB only or a kit of parts for this project from the eShop.  The kit #484K contains all the components required to assemble the complete board as shown in the photo guide below, including a pre-programmed PIC microcontroller.

Click on the photos below for 1024x768 version

Step 1

Step 2

Step 3
Step 1.  Use a blob of solder to bridge the two solder jumpers as shown.  Be sure to bridge only one half of each jumper.

Step 2.  Install the resistor identifying them using the coloured bands.  It doesn't matter which way round the resistors are fitted, the coloured bands show the value not the orientation.

 brown, black, orange, gold - 10K (R25, R26)

  orange, orange, brown, gold - 330R (R1,R2,R3,R4,R5,R9,R32,R33)

Step 3.  Install the two 1N4003 diodes.  Make sure to fit them with the silver band at the end shown. (this matches the PCB overlay)

Step 4

Step 5

Step 6
Step 4.  Install the 100nF capacitor C2. Will usually have the number 104 on the body (colour of part may vary)

Step 5. Fit the 7805 voltage regulator IC

Step 6. Install the two IC sockets.  Note they are indented at one end.  Fit the socket so the indent is at the end arrowed.

Step 7

Step 8

Step 9
Step 7.  Install the 330nF capacitor C1

Step 8. Fit the two 2-way terminal blocks together using the dovetail key.

Step 9. Install the switch and terminal blocks.

If you are using an alternative switch mounted away from the PCB you may want to omit the switch and solder wires to the switch position on the PCB.  In this case connect to the two smaller holes within the switch outline of the component overlay.

Step 10

Step 11

Step 12
Step 10.  Install the 3-way terminal block

Step 11. Install the five LEDs into positions LED1 to LED5.  Make sure to identify the short lead and fit it into the hole with the square pad as shown.

Step 12. You may want to bend the leads through 90o in which case make sure to bend it so the short lead will still fit into the hole with the square pad.

Step 13

Step 14

Step 15
Step 13.  Before proceeding this is a good point to check the PCB for bad solder joints, solder splashes or bridges and any component lead off-cuts that may be stuck to the PCB.  Having done this apply power to the board at the 3-way terminal block and use a multimeter to measure the voltage at the 5 volt test point. (see photo)  It should measure between 4.75 and 5.25 volts, if it doesn't investigate the cause before continuing.

Step 14 / 15. Disconnect the power to the PCB.  Next install the PIC16F628A and CNY74 opto-isolator into their respective sockets.  Make sure to fit the IC's with the indent in the IC package at the end shown arrowed

Step 16

Step 17

Step 18

Step 16. With all the parts fitted, reconnect the power to the PCB through the 3-way terminal block.

You can now test the board by pressing S1.  With no external connections from the throttles it appears to the firmware that the throttles are closed so the board with go through a normal start sequence each time S1 is pressed.  If you press and hold S1 it will enter the setup mode as described on the main page.

Step 17. Since the PCB used is a multifunction board, the diode and resistor connecting to the throttles are not accommodated on the PCB.  The photo shows how they should connect between the throttles and the terminal blocks.  Wire tail colours correspond to the diagrams on the main project page

This is done to provide a clear illustration of the wiring.  It is not recommended to assemble the resistor and diode without suitable insulating sleeving.  (see Important notes section below)

Step 18. The original start controller has a connection to operate a 'power control' output.  This output is also available and connects to the PCB at the point shown by the Orange wire in this photo.  If you're not using the power control output you can ignore this step.

Important notes

These notes cover some details important to getting the project working correctly.  Please read

Connecting power

The power supply to the board connects via the 3-way terminal block. The PCB is marked V+ and V- indicating the positive and negative power input. There are two V- connections, either can be used.  The board has reverse polarity protection so if you accidentally connect it the wrong way the board shouldn't be damaged.

Connecting LEDs using the option header K1

Rather than mounting the five LEDs on the PCB they can be connected via cables using the optional header. You can buy a 16-way IDC header socket, plug and cable from the Picprojects eShop under the 'Components - Connector/Cables' product section
If you use the header to connect the LEDs do not fit LEDs to the PCB (it's either/or not both)

Power supply requirements

This version of the controller needs a smoothed DC power input.  The Scalextric Power Supply supplied with the track does not have an output smoothing capacitor so isn't directly suitable for use with this PCB. If you are building this project in conjunction with the power supply project you can use the power from that.  If you are retaining the original Scalextrix Power Supply, this board will need powering from a separate DC power supply.  Since the board has its own regulator on board any 9-18 volt DC power supply that is rated for 150mA or greater will work.

Connecting the throttles

Since the PCB used is a multifuction board one resistor and diode in each throttle channel have to be mounted off the PCB.  When I built the original projects I replaced the 3.5mm jacks on the throttles with  3-pin XLR plugs and sockets.  If you are doing similar the back of the socket would be a good place to fit the diode and resistor.  You can then run two wires back to the terminal block on the PCB (with two throttles you will have two pairs of wires going back to the PCB)

The schematic diagram on this page uses the same red / black / green identifiers for the connections to the throttles.  You can therefore refer directly to the main page for additional information on connecting to the slot car throttles and track.

PIC Firmware

The PIC supplied with the kit #484K includes a pre-programmed PIC16F628A so you don't need to download this code or program the PIC yourself.  However, should you need to reprogram the PIC for any reason you can download the original code here.

The HEX file ready to program into a 16F628A can be downloaded for free from here (right-click Save As).
(a 16F627A can also be used without any modification to the code or hardware)

Description Filename Download link
HEX file ready to program into the PIC 480-scs-main.HEX, v1.0.0. 06/02/2011 download
checksum 0xAFCD