slowing the rpm's of a motor??

[duhaas88]

I have some small motors sold by Radioshack for their zip-zaps that are rated at 19,000-38,000 rpm's. The reason I would like to use these small motors is for their extremely small size. My questions is how do I slow the rpms to a 1/4 that. I am thinking of using them in a model as "stepper" motors. By simply limiting the voltage with this slow the rpms' wihout using gears like a servo?? I would like to create a simple PIC controller that will allow me to control them via switch so that once the switch is pushed they would go for a preset time and stop, and then go the opposite direction when the swith is pushed again.

Thanks for any suggestions

[duhaas88]

If I simply lower the voltage that is available to the motor will that in turn keep the rpms down??

[slipstick]

Yes. But if you're driving any sort of a load you want to check the speed WITH the load first. Two things reduce motor speed, reducing the voltage and increasing the load.

Steve

[duhaas88]

What would be the best way to control 3 of these motors to get them to spin for so long and then stop when I switch is pulled on the transmitter?? And then when the switch is pulled again, the motors repeat the sequence but in the opposite direction. I"m trying to build a micro retract system, wthout using servos:) Would the use of a PIC be simple?? I'm not a coder or a PIC guru:(

any ideas??

[flunki]

In case you dont want to use PICs you could try:

- microswitches, just contacts from relays, to make them move between 2 positions. Such switches, micro motors and micro gears can be found in PC CD-Rom drives.

- servo eletronics from a broken servo. With a 3 position switch or a slider you could control left (-0%), stop(50%) right(100%). Set the poti of the old servo electronics to center position.

Wouldnt use a timer. The speed will depend on battery and gear load . . .

[MatC]

Some simple solutions:
If you have a reversing switch already, you can use two microswitches to limit travel, and still allow the reverse direction to work.
If you have a reversing voltage, you can use two microswitches and two diodes to limit travel, and still allow reverse to work.

I'd really consider using servos, but if you want an easy way to do it with motors:
Pull a servo apart, remove the motor, set its pot at 50% (glue), and use the board's output to give you a motor drive circuit (check your motor current/voltage, servo motors are smallish!). Depending on the transmitter switch (high or low, let's say), you'll get a positive or negative drive as the servo notices the huge discrepancy between 50% and the high or low input.
Then put two diodes in parallel with that output (opposite directions), and switches in series with the diodes. That way you can limit the motor in each direction, and still allow the reverse to work. You can use that arrangement for each motor so that each wheel will reach full position and lock.

Avoid the pic route unless you want to become a programming guru :)

The "move for a certain time" is ok, but unless you have a slip or stop at the end of the travel, they'll get out of sync.

Show us a video when it works :)