destroying my last pic? driving a miniature motor

[Darrel Taylor]

Is there a difference in connecting the load between emitter and ground, or between collector and vdd (besides resistance increasing base to ground when the load is on the emitter side)?

With transitors, the current you get out is dependant on the current from the base to emitter. If the voltage on the emitter changes, then the base to emitter current will be reduced. So if the load is between the emitter and power, ... as the transistor starts to conduct, the emitter voltage changes and counteracts the base current that's trying to turn it on. While it seems to kinda sorta work a little bit, you always end up with a lower current output.

So basically, you want the emitter to be at a constant voltage, either GND or V+.

But the difference is ... if you want to "source" current to the load from V+ (like in the first schem.) you would use a PNP transistor. Then output HIGH from the PIC is OFF, and LOW is ON.

And as I read this back, it doesn't even make sense to me. (I'm a software guy).

Alain!!! Help!!!! Anybody!!!

[Archangel]

Thanks Darrel,
I have seen it in print that the transistors should go one way but not the other, but never an explanation as to why.
Thanks!

[Acetronics2]

And as I read this back, it doesn't even make sense to me. (I'm a software guy).

Alain!!! Help!!!! Anybody!!!

Hi, Darrel

For simplicity :

1) Motor ( or load ) has one terminal connected to GROUND

- use a PNP Transistor w/Emitter to POwer ( or P- Mosfet W/ Source to Power ). the "ON" state will be with a LOW state from the PIC.

2) Motor has one terminal Connected to POWER

- use a NPN Transistor W/Emitter to GRound ( or N Mosfet w/ Source to GRound ). the "ON" state will be with a HIGH state from the Pic.


That's all !!!

Alain