Peter C. Wallace wrote: > The three phase PWM generator does have high and low side drive and > deadzone > timers but a three phase drive is probably not a good beginner project :-) > > You can also count TTL encoder signals directly with the FPGA board. > Hm, some good memories come back. My CNC days started with a flat-bed plotter with 400V 3 phase drives and resolvers for feedback. Three 19" full height cabinets full of transistor boards - Real transistor Transistor Logic :-) to do the math for circular and parabolic arcs.
I was thinking along the same lines (create my own H-bridge) - I can get some cheap servos but did not want to spend too much money on a driver just to test if I will buy more to replace the steppers in my current mill and the new one; > But... > > I think Rays suggestion of using a parallel port (or multiple ports) > is a better starting point. If you use the bare FPGA card signals to drive a > home-made HBridge, you risk damaging the expensive FPGA card instead of a > $15.00 parallel port card. The magic word is Optocouplers. All the signals from my 5i20 cards run through opto's. Even the 10V signal for the VFD is opto-coupled and also all limit and home switches. As long as you can cope with a switching time of 10 us a cheap 4N35 opto is great. For less than 50 cents per channel I am not going to risk my fpga board or any other part of the PC. Some weeks ago I had a problem with a short circuit in the VFD (Toshiba VF S-11) resulting in a flash and a loud bang from the inners from the VFD - luckily all PC parts are still OK :-) Rob ------------------------------------------------------------------------------ Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day trial. Simplify your report design, integration and deployment - and focus on what you do best, core application coding. Discover what's new with Crystal Reports now. http://p.sf.net/sfu/bobj-july _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
