Chris,
Usually an inductor that is being switched, I.e like your motor, would have a resistor and a capacitor (a snubber network to dampen the ringing) and a hi PIV diode across the motor......
taking the switching frequency to somewhere around 10Khz will eliminate the whine......If you go to Vellemans website and look up their pwm kit,look at the schematic especially around the output stage.That will explain a lot...(hopefully )
??
Chris, John is suggesting putting three electronic parts across the terminals of your present motor, if you use your present speed controller that whines. The intent would be to stop that whine.
The three components he is talking about are a capacitor, a resistor and a diode.
A high PIV diode just means a diode that has a high voltage rating, in other words it isn't going to burn out when it gets a momentary spike of voltage. So if your motor is expected to see about 10 volts maximum, you would pick a diode that is about 4 times that (or more) in rating. A 50 volt capable diode would be fine, and so would a 100 volt capable diode.
Here in the States we have Radio Shack, where we can walk into the store and say to the clerk "Gimme a 50 volt diode!" and he would then consult with others there until someone would eventually lead you over to a display with drawers one of which said "DIodes and Rectifiers" and he would then depart. You would open the drawer and find a small section that said "SILICON DIODES 50 VOLT" or 50 PIV, and then buy one or ten if packaged that way.
Anyway, since you sent for the other controller, you may not have the hum problem -- I don't on the wiper motor I used, and I hope yours will be the same.
With regard to pushing the weight of pennies, were you thinking of a low friction material, like fomica (countertop material)?
I would think pennies would slide pretty easily on that. Also, the way this works is by averaging just like a drop of water falling an inch into a bucket. You could say that the drop moves 10 kg of water. But it doesn't move it very far. The pennies work the same way. Each penny may move many others (but usually not all of them by a long shot) but the ones it moves move only a small portion of its movement. Pennies fall because they are usually on the edge and reguire only a very slight movement to topple off. Thus there is a mechanical advantage inherent in the whole process of moving coins. You would never move all of the coins, and the ones you move move less than one penny width.
