Sensor Electronics

Heres the design for a WOW compatible sensor. It has a couple of improvements over the original though.
It can be set to have between 1-9 hits and has an optional shield function.

As well as the circuit plan you will also need the hex file for programming the PIC chip which is located in the file in the Download section. The model of PIC used is a 16F84 microprocessor (18 pin) so you will also need an 18 pin DIL chip holder.

Component Placement

component placement

The 100 K ohm optional resistor is needed if you want to wire the shield activation switch. If you do fit it it is soldered to the TRACK side (opposite side to the rest of the components).

The Bi-colour leds are the 3 legged type that have both a red chip and green chip on board. When both wafers are powered up you get a yellow/orange colour. You have to get them wired the correct way round. There are ‘r’ and ‘g’ markers on the pcb to indicate which leg needs to be connected where, r=red, g=green, middle led is common ground.

Wiring Up

wiring up

A momentary switch should be wired between Point ‘A’ and ground (the black ‘block’ on the ground track with 3 holes in it is for this purpose). If you want to use the shield function then another switch is wired in between point ‘B’ and ground. A peizo sounder is connected where it says ‘spkr’ on the board.

4 core wire connects the main circuit board to the rear sensor board and then to the front sensor board.
You may have noted that the arrangement of pads on the main sensor electronics is in a specific pattern.
This is because it is possible to solder an RJ11 4/4 socket to the board here (the 2 large round pads are markers for 2 3mm mounting holes). If the socket is wired in it allows you to unplug the sensor harness for ease of replacement.

Battery needed is 9 volt so a PP3 is ideal. It is wired to the 2 pads marked + & - on the board.


Switch on :-). All 3 leds should light up green, at this point pushing switch A will remove one of the 9 start hits, each press removes another (accompanied by a short beep).
Don't worry if you go to far, removing them all resets it back to 9. If you don't press switch A for a short period the sensor times out and the sensor will continue with the start up process, it will give an audiable series of tones indicating start up and the hits will be set.

At this point the sensor is live and will take hits. While the sensor is live the LEDs on the sensor boards will flash dimly, if you want to disable the LEDs flashing (it may be night and you might be a sniper etc) then push switch A, this will switch the flashing off, pushing it again will switch them back on.


By default the sensor has 3 time limited shields. When activated they make you invulnerable for approx 5 seconds.
Each shield has a colour, green yellow and red. The first shield makes all the hit lights flash rapidly green as well as the piezo will beep rapidly and the hit light will flash brightly while in operation.
The second shield makes the lights flash yellow and the last one red. When they have been used up you need to reset the sensor to recover them.

All this information as well as the track layout is also contained in the file available to download.