I have a 7.2V Johnson Electric DC motor. I'm trying to incorporate it into a mobile platform I'm building. The only trouble is that I was planning on using a power supply which supplies 12V and 5V.
This has led me to a few problems which I can't resolve:
1) Can I put a resistor in series with a motor to lower the voltage a bit? I suspect not, because the internal windings of the motor are probably like 3 or 4 ohms, yeah? And a 4-ohm resistor would dissipate a lot of heat and waste energy. I saw a book where they tested motor idle current by inserting a series resistor, and it was this enormous one with the label "Behemoth" written in the caption.2) What happens if I apply 12V to a motor rated at 7.2 nominal volts? Are the ratings there only to prevent the motor from overheating? And if so, then would I be safe running such a motor at 12V if i ensured that it never stalled? Im planning on running the motor at a about a 50:1 gear reduction, and its not carrying too much weight.
3) Assuming the two above ideas are bad ideas, (and as I've written this I've convinced myself that they probably are), what would you hobbyists out there do: find a 12V motor or find a 7V regulator?