Ok, you are handling more current then I am comfortable with. I was going to sugest some H-bridge chips, but they are no where near your curretn requirement (about 3 A only). David Ted Mawson wrote: > David Harris wrote... > > "What kind of current do you want?" > > Answer... > I'm thinking in the 100-150 Amp range. Basic outline is for a PIC that > senses 2 standard R/C servo channel pulses on 2 inputs and converts this to > signals for 2 H Bridge drives, 1 per motor. > > Questions that I have at the moment are... > 1. Whether to poll the inputs or trigger the pulse width count using an > interrupt? > 2. Whether to drive 4 PWM outputs or just 2 with a 3rd direction control > (per motor)? The latter has the advantage that it is less likely to get > into a drive for all 4 FETs in the bridge. > 3. How to handle the current in the output stages? MOSFETs like the BUZ11 > can take 30A, 50 Volts, and have an on resistance of 0.03 Ohms and there are > many more out there that can handle 80V and 50A. I'm thinking of > paralleling up 2 or 3 MOSFETs per channel with the resistance of a carefully > designed PCB providing some kind of current sharing resistor capability. It > seems like a no brainer to use opto-isolators to separate the PIC output > from the MOSFET gate drivers. > > Enough detail? > > Ted PICman@Portfoliopm.com > www.portfoliopm.com > > ----- Original Message ----- > From: "David P. Harris" > To: > Sent: Friday, February 08, 2002 11:27 AM > Subject: Re: [PIC]: Robot Motor Controller > > > What kind of current do you want? > > David > > > > Ted Mawson wrote: > > > > > Hi Bob, > > > > > > Your description is exactly what I was thinking of. I'd be very > interested > > > in seeing what you've got so far. > > > > > > Have you got the H bridge FET drive stuff fully worked out? I have some > > > specific ideas in this area, seems to me that it should be possible to > make > > > a very high current H bridge by using MOSFETs that can have on > resistances > > > of 0.03 Ohms! > > > > > > Ted > > > ----- Original Message ----- > > > From: "Bob Blick" > > > To: > > > Sent: Thursday, February 07, 2002 10:16 PM > > > Subject: Re: [PIC]: Robot Motor Controller > > > > > > > I've done something like that for a fighting robot. Takes two R/C > > > > receiver channels and generates pwm for two motors. Treats one > > > > stick as fwd/rev and the other stick as left/right. One motor goes on > > > > each side of the bot. Also monitors the current on the h-bridges and > > > > limits current. Has extensive amounts of code designed to reject > > > > spurious signals coming from the receiver. > > > > > > > > I was planning to do a web page about it. If you can wait, then it > > > > would come with some explanation, but I can send it to you if you > > > > want to figure it out yourself. > > > > > > > > Uses a 16F876, coded in HiTech C. > > > > > > > > Cheers, > > > > > > > > Bob > > > > > > > > On 7 Feb 2002 at 18:10, Ted Mawson wrote: > > > > > > > > > To save me re-inventing the wheel, can anyone point me to a PIC > project > > > that takes 2 Radio Control servo pulse inputs (from an R/C receiver) and > > > generates the PWM drive for 2 DC motors running in H bridge mode via > FETs? > > > > > > > > > > Thanks, > > > > > > > > > > Ted > > > > > > > > > > -- > > > > > http://www.piclist.com hint: The list server can filter out > subtopics > > > > > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > > > > > > > > > > > > > > > > -- > > > > http://www.piclist.com hint: The list server can filter out subtopics > > > > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > > > > > > > > > > > > -- > > > http://www.piclist.com hint: The PICList is archived three different > > > ways. See http://www.piclist.com/#archives for details. > > > > -- > > http://www.piclist.com hint: The PICList is archived three different > > ways. See http://www.piclist.com/#archives for details. > > > > > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.