small dc motors

The thing that worries me is that raul seems to not even have been taught the difference between TO-92 and TO-220.

Thanks, Rich

"The thing that worries me is that raul seems to not even have been taught the difference between TO-92 and TO-220."

Your right Rich, I don't know the difference.

Anyway, here is the bread board of Ed's schematic but, the motor runs continuously so obviously I've done it wrong. Does anyone have any ideas?

Thanks, Raul

A TO-92 is one of those small, three pin plastic packages that you see used with signal transistors. The transistor you have is a TO-220.

Also, how is this supposed to shut off? It looks like you can vary the duty cycle, and thus slow down or speed up the motor, but shutting it off requires you to permanently pull the base of the TIP31C to ground somehow.

You can add another switch that will turn it off by toggling the reset pin to ground (view with fixed point font)

5V-----o------ | o Switch, open = off, closed = ON \\ o------ To Reset | [100k] | GND----o------

--
Regards,
  Bob Monsen

" We can allow satellites, planets, suns, universe, nay whole systems
of universes, to be governed by laws, but the smallest insect, we wish
to be created at once by special act."
 -- Charles Darwin

I think I see the 150 ohm resistor connected to the 7555 on pin 2 rather than pin 3...

Right. The circuit is not intended to shut the motor off, only to control its speed. On/off would be a switch in the supply line - or your suggestion below.

Raul: Can't tell from the picture, but it looks like the 1K and the 150 may be shorted together. The 150 is supposed to go to pin 3 - the 1K to pin 2.

Ed

I think there should be one BFC from 12V to gnd on the controller board somewhere.

Lord Garth, you were right! I didn't see it. Thanks, it works now. Raul

Thanks Guys! Raul