cncmachineguy
- 7th October 2010, 21:01
Hello all, I have gone done a path that may be a dead end for me. Inspired by this post http://www.picbasic.co.uk/forum/showthread.php?t=13808, I looked over the schematic and quickly went to work ordering some parts. the fets and diodes to be exact. 80 pieces of each. Last night it came to me there is no current sensing in the schematic. I posted about this on microchip's forum and have been advised in fact this circut will not work as is for my steppers. They are 2A 1.8ohm coils.
Some very good suggestions were posted concerning single chip solutions. My trouble is I am a bit scared of the way they heat sink.
So heres my question, can I just add a current sense resistor in the ground path of each coil, then read it and do something when the current reaches 2A? ie, turn off the pwm or change the duty cycle.
Don't get me wrong, its not that I can't find some other use for the parts I have, but I went with a uni-polar drive for this project because of the soldering requirements of the single chips. I could use the torque benifits of driving the motors bi-polar. I don't even mind letting out some magic smoke if I am learning something, but I want to feel like I am heading the right direction. Now it seems like all the block diagrams for the single chips do it this way, this is why I think I can.
I do realize this is a PBP forum, but there seems to be lots of hardware folks here too.:)
Some very good suggestions were posted concerning single chip solutions. My trouble is I am a bit scared of the way they heat sink.
So heres my question, can I just add a current sense resistor in the ground path of each coil, then read it and do something when the current reaches 2A? ie, turn off the pwm or change the duty cycle.
Don't get me wrong, its not that I can't find some other use for the parts I have, but I went with a uni-polar drive for this project because of the soldering requirements of the single chips. I could use the torque benifits of driving the motors bi-polar. I don't even mind letting out some magic smoke if I am learning something, but I want to feel like I am heading the right direction. Now it seems like all the block diagrams for the single chips do it this way, this is why I think I can.
I do realize this is a PBP forum, but there seems to be lots of hardware folks here too.:)