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.