Re: design alternatives: servo control and power source Hi Doug:     I built a 12-servomotor walking robot using two SSCs - their interface with the HandyBoard is well documented, and ICB drivers are available on the webpage.  I communicate with two SSCs (www.seetron.com) via one serial line connected to PA7 - a digital input port - as documented. The SSCs require a 9-volt supply, so I share the HandyBoard battery.  I use a rechargable NiCd battery, and to this point it hasn't required intentional recharging.  The SSCs also take in a 4.8-volt to 6-volt supply that is pulse-width-modulated to drive the servomotors.  In my experience, the twelve standard motors (50oz-in) can draw 3A at 5V at stall - which is a large amount of current. If you have a large 9-volt supply to power the boards and the motors, the servomotor current draw will spike and probably reset your control boards. You could try to isolate the supply leading to your boards, but that would be complicated and not completely effective.  You'd also have to voltage divide the large 9-volt supply, and this gets tricky - you'd have a considerable loss over the voltage divider that would make this unattractive.  The number 15% comes to mind, but I can't back that up. I used the one 9-volt NiCd for the HandyBoard and the SSCs, and a 4x1.2-volt NiCd battery pack for the servomotors.  As I mentioned, the motors peaked at 3A of current draw.  In retrospect, I would have designed for double the weight in batteries, and put four more NiCds in parallel for extended operating life. I hope that helps! -- William Sitch, http://www.engsoc.carleton.ca/~wsitch 4th Year Electrical Engineering at Carleton University ----- Original Message ----- From:  To:  Sent: Friday, April 16, 1999 11:59 AM Subject: design alternatives: servo control and power source >Hello, > >I am planning to build a robot based on the Lynxmotion Hexapod II >and Big Grip kits. There will be 12 servos for lego control, 2 >servos for the manipulator, and 2 more for a camera pan/tilt >unit. Everything appears fairly straightforward, but: > >1) I am trying to decide on whether to use two mini SSCs or the >   Ferrettronics chips to control the servos. Does anyone have >   any info/experience that might sway me one way or the other? >   Is anyone aware of documentation or tips for using either >   of these with the handy board? > >2) I am wondering if I can run the servos from the handy board >   batteries or if I need to have a separate battery pack for >   the servos. Obviously the HB batteries won't last very long >   if they are also running 16 servos, but would this work? > >TIA, >Doug >