destroying my last pic? driving a miniature motor
Hi everyone,
Please help me if you can....I don't want to destroy my last pic....
I'll get right on topic:
I had partial success driving a 4mm motor directly from the 4 pwms of my 16f690. I was using pulse steering to output hpwm signal on 4 pins. Testing this, I realized that this would not allow me enough current on the motor i am using.
Here's what I did initially:
I chose 250 ohm resistors for each pwm output because 5v/250ohm is 20 mA the max a pic can source or sink. After the resistor these lines converged going to the positive terminal of the motor. Because I gave moter 4 pwm signals, the resistance to 5v(supplied by PWM) was actually 250/4=62.5ohm.
My motor has 9.6ohm internal resistance
62.5ohm divider: 9.6/9.6+62.5ohm x 5V==>motor was only getting .666v….
Current through the motor 5v/72.1ohm = 69.3mA
This was not enough to get it spinning nicely...
Here's where I destroyed 2 pics:
I quickly tried hooking up one of the 4 pwm signals through a 2n2222 to
boost the current. Although i thought i had enough protection using diodes when I ran the program, not much happened... Also some sensors on i2c and power lines didn't blink as they normally do at startup. Only removing the pic 16f690 got those sensors blinking again. After adding some more diodes, safer resistor values I tried again with another pic....Same result... Unfortunately I can not reproduce the exact schematics as it was 5am and I was tired a little impatient and yes...drinking...
I think I may have left the other pwm pins floating, or possibly switched the collector and emitter. All I know is that I didn't even get to see smoke...
Can anyone advise me on a lowest partnumber/smallest parts solution that would do the beforementioned. HERE IS WHAT I HAVE IN MIND...
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