9.4V motor driver problem

[Tanna]

Hi.

I'm trying to PWM a hobby-motor running on 9.4V.
I'm using i PIC with a BC107 transistor inn front a IGBT transistor (IRG4BC30U), which runs the motor.

My problem is that only 3 to 4V gets to the motor, and the IGBT will not let more than 2-3A to flow through the device. (I need 6-7A).  My power supply is big enough, and the motor runs fine without the IGBT (straight on the supply)... I have also tried a MOSFET BUZ10, but that don't change anything worth mentioning.. The motor don't run on max, and the transistor gets extremely hot.

What can I do to drive this motor as I please ?
Is it normal that MOSFET and IGBT transistors make this big voltage drop when it's on?

 

[indulis]

No they shouldn't get hot if they are driven properly.

Could you provide a little more info...

At what frequency are youu running?
At what voltage are you driving the MOSFET?
A schematic would help... exactly how is your circuit configured "after" the PIC?

For 6-7A a MOSFET should work just fine. It's not to hard to find a MOSFET with a Rds on in the 10 milliohm range. If you do the math (I^2*R) for 100% duty cycle, that's only .49W @ 7A. The current you would need to drive it would depend on the switching frequency.

 

[Tanna]

aaa... Found the problem..

I had placed det motor between the emitter and GND. Makes bad feedback for the workpoint of the transistor..
When I placed the motor between the collector and +9.4V it works fine...

Anyway.. Thank you...