This parts list is not yet complete but it does show where to get some of the bits. Some of the bits will require you to look for local suppliers.

Motor/gearboxes are available from several suppliers. You can buy them as "solar motor drive" part number 37-0442 from Rapid Electronics on 01206 751166 or "solar motor and gearbox" part number 450-040 from JPR Electronics on 01582 470000.

The pulleys (wheels) come from JPR Electronics 0n 01582 410055 as part number 450-076.

The tyres are 22 mm dia by 5 mm width O rings from our local bearing supplier.

The balsa wood came from our local model shop. Sometimes you can save a few pennies by buying an offcuts pack rather than a large plank.

I have no idea where the drawing pin came from originally!

The trimmers are 430-500R from JPR Electronics on 01582 410055. There are many alternatives but make sure that you use a 12 turn trimmer or you will wish that you had when you are tuning for best performance.

The relays are not critical. The contacts should be rated at 1A or more. I have used both 5V and 12V coils. 5V are over-run but they are only on when turning right and the higher drive may give faster switching. You could use 820-321 parts from JPR on 01582 410055 or 635-522s from Farnell on 0870 1200 200.

The LEDs can be anything that you can lay your hands on. Red is better than green as they need less volts to turn on. If you have got both red and green, it makes it easier to see what the sensors are doing. Don't use white or blue ones as the forward voltage is too high.

All the diodes can be 1N4001. You can get these from any electronics supplier as they are very common.

The transistors are any medium power NPN types. I used BD433. BD437s would be just as good. They need to be rated at more than 1A collector current with a reasonable HFE at this current. Anything in a TO126 or TO220 package can probably handle the power.

Any lever-type microswitches will do. Ones with long levers are best, but short levers can be extended with wire or similar. The ones I used were 800-138 from JPR Electronics on 01582 410055.

The capacitors can be whatever you can lay your hands on. The values are not critical. The 100n capacitors can be anything greater than 1nF rated at 12 volts or more. Disc capacitors are cheap and suitable. You could use 110-140s from JPR Electronics on 01582 410055. The electrolytics can be anything of 10uF or greater rated at 10 volts or more. For example, you could use 100-048s from JPR.

The battery clip could be salvaged from an old radio or you could use 440-005 from JPR.

The resistors can be anything of 1/4 watt or greater. I used SFR25s; CR25s from JPR would be O.K.

The battery is a PP3. Alkaline types are best.

last modified 14/9/01