All,

Whether you have motors to test and break-in or you need to power your tire truer, a variable power supply is indispensable  for slot cars.

Power supplies are normally quite expensive, their price climbs as their maximum working amperage goes up or if their physical size gets smaller. I just wanted to show you what I consider to be the best bang-for-the-buck in terms of a compact variable power supply.

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What you see below is not a “full” power supply, it is an adjustable voltage regulator – the unit itself doesn’t power anything but it will allow a fixed input voltage to be adjusted.

The regulator is around 4″ L x 3″ W x 2.5″ T; its maximum DC input is 35 volts; the maximum output, indicated in the L.E.D. display,  is 1.2 to 30 volts at a maximum of 3 amps.

When looking to purchase a variable power supply you need to look at two things: voltage and amperage – you want both to cover your maximum variances.

The “limitation” in this unit is the maximum amperage rating of 3 amps; it is plenty to test motors (1/32 to 1/24 scale slot car motors, not “wing” type motors) and probably enough to power a 2 lane home track but it may not power your tire truer (something you can fix by replacing the tire truer motor to a milder version).

To power the regulator, you will need a fixed voltage power supply (car battery, wall wart or power adapter from dead/unused electronic devices, etc.); just remember that there is always a drop in voltage (~3V) when using voltage regulators: if you have 12 volts/1 amp at the regulator input, you will probably get 9 volts/1 amp at the output. Also, DO NOT exceed the regulator’s maximum input voltage (35 volts in this case) but if you want 3 amps for maximum output, you NEED TO feed the unit with more than 3 amps.

To power the regulator, I chose an old laptop adapter rated at  19 volts/3.42 amps (most laptop adapters are 19V, their amperage varies according to size/performance) which should give me a maximum output of 16V/3A.

You can just cut the plug-end of the adapter and attach the wires to the regulator’s input but I made separate cables to suit my own needs:

This is how it looks after everything is connected:

Here the unit is running at lowest/highest voltage output:

And here I’m breaking-in a motor at 4 volts:

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The regulator was purchased for $15.99 from eBay, if the link doesn’t work, search eBay for: Adjustable LM338K.

If you are a club member and in need of a power source, $5 will get you the power adapter in this article – just let me know.

Ary.