Controlling a DC Motor (Mabuchi FA-130)
July 27, 2009
I'm trying to run a Mabuchi FA-130 (#18100) DC Motor, it uses 3V and 2.1A when stalled. However, I did some measures and when I forced the motor to stall it consumed nearly 4A, but I think this was some sort of coincidence since It has never happened again.
I'm using a circuit similar to this one posted by Simon Z in his post:
(By Simon Z and taken from http://letsmakerobots.com/node/7990)
The difference being that after reading the comments on that post I'll use a BD139 transistor. Anyway, I'm studying Computer Science so I'm very bad with circuits, and I have some very basic that I'll appreciate if could be answered.
- The BD139 transistor has a maximum current of 1.5A, won't it burn with my motor? If so, I couldn't find a 2.1A transistor, anyone know one? or can you make an equivalent one with some sort of transistor's grouping?
- Is there a simple way to limit the motor current so it will never burn the transistor?
- How do you choose the value of that resistance of 500 ohms and what is it for?
- I searched and read somewhere that the diode is used to protect the motor from the transistor on-off changes, is that correct? If so, how do you know which diode to use?
If at least one of these questions could be answered I'll appreciate it, thanks.