April 1, 2012
about 3 years ago
Wish I’d read this earlier, but I did diagnose - and fix - the problem.
Yes, the motor draws more current than the circuit (as shown) supplies. It works if you swap the 10k resistor (which limits the current from pin 9 to the transistor base) for a 1k resistor. The transistor isn’t switching all the way on with the tiny current the 10k lets through. It will work with some low current motors (I got it to work with a tiny motor at 20ma) but not the bigger one with the kit.
The kit doesn’t come with 1k resistors. The value isn’t too critical, so if you don’t have one handy you can use 330 ohm resistors in series (at least 2, for 660 ohms) or three 10k in parallel (3.3k) to get into the right ballpark. (You need enough resistance to prevent burning out the pin from too much current draw.)
No public wish lists :(
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