Output current to a DC motor

[bigbanner]

Hey all,

I'm very new to programming in PICBASIC. We are trying to output current to a DC motor for 5 seconds, off for 5 seconds, on for 5 seconds, etc. We have built a circuit with a PIC16f77 that will do this for voltage (it's running in 4.23 voltage supplied to the pic, and we have LEDs lighting up for 5 seconds with 4.23 volts supplied, off for 5 seconds, on for 5 seconds, etc.)

So, my question is how can I have the same logic with current output instead of voltage? The DC motor won't run on voltage. I apologize if this question seems trivial, we were thrown into the fray with little to no help.

Thanks!

[sinoteq]

An easy way is to use a ULN2001. They can handle alot of current and are cheap. Connect the Pic to one side and the DC motor on the other. When the PIC-pin is High the motor will spin. Low on the Pic-pin and it will stop. If you connect all inputs to one Pic-pin and connect all outputs to the motor you have plenty of current to use, if you only use one channel you get 500mA. Just be careful you don't overload the chip, then black smoke will come out and that is kind of bad.

To make the motor even stronger you can connect it like this:

+ of Vbattery or main dc source to the motor
- side of the motor to the ULN chip
Pin 9 of the ULN chip to the +side of the motor. This is to enable a diode inside the ULN to protect the chip when using inductive loads.
Pin 8 of the ULN to GND

A Pic output pin to the correct ULN inside.


That should work... or you get a MOSFET transistor and do the same thing.



If you connect this way your motor will not be on the 5v supply and you get less noice on that line.... That is good