The trouble with power supplies is about $250 for a good one. The otherproblem is to be serious about racing you need one. The good news is thatSlotSide can solve both of these problems for you.
If you value your armatures you probably won't run them on "unclean" powerlike what you get from cheap plug in transformers meant to run your portablephone or battery charger. That's a quick way to turn a quick arm to smoke.Furthermore, the few milliamps are not sufficient to break in a motor thatmay draw 4 or more amps. So, the first thing you need is a clean supply ofabout 12 volts and a good 8 amps. Why 8 amps for a motor that draws 4? Well,like everything else a power supply functions best when you are not suckingevery last electron out of it. You can get away with about 5 amps but themore the better.
So, you think 8 clean amps at 12 volts is expensive, eh? That's where youare wrong! Most electronic surplus stores have these devices forabout $20 designed for audio or computer applications. These uses requirecleaner power than even your most treasured G7 armature.
The problem with these is you get exactly that, 12 volts. No metering, novoltage regulation. You can't just put a variable resistor on the output,unless it is the size of a small car, to handle the current load and givesmooth control at the same time. Integrated circuits do a neat job of thisin a very compact package. I recommend using the Linear Technology LT1083 voltage regulator. About $8 at electronics stores and widely available. Butyou have to know how to use it.
That is where SlotSide comes in.
What follows is a circuit diagram that requires about $20 in electronic parts if purchased from a surplus store. It will control and meter your voltage and current. Best of all it is a very simple circuit and can be built by anyone.
Surplus store is the key for the meters. A good place will chargeabout $5 each but you may have to do some scouting around. I bought mystuff at Active Surplus in Toronto.
A few words about building this thing. It is best done on a small piece ofperforated circuit board using insulated copper wire connections. If youwant to get fancy you can etch a printed circuit board with ferric chloride,but if you can do that then you don't need to be reading this.
The LT1083 integrated circuit should not be mounted on the board because itrequires a heat sink that should be bought at the same time. This can bescrewed to the case of the power supply. This brings us to the next point,how does all this connect to the 12 volt audio power supply we bought for $20?Well, most devices like this come with space in the box that you are going toexploit to fit all this. Mounting it all is like fitting into the jeans youwore 10 years ago, possible but not comfortable. You will need to cut holesto allow the meters to show and the control to be accessible. A dremel doesa neat job. If you can't fit the control module into the power supply boxyou can put it in it's own box and wire them together, but this is less elegant than you may deserve. It is not necessary to buy a fancy variableresistor for 'R2' on the circiut diagram. It carries minimal current andshould not cost more than $1. Similarly low power capacitors are all youneed.
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