On 23 June 2011 13:05, Erik Christiansen <dva...@internode.on.net> wrote:
>> The drawback of this circuit is that wherever it is put it needs both >> the logic positive supply and the controlled positive supply, but I >> can't see any way round that if you want to actively discharge the >> output cap on one part of PWM cycle. Having a passive discharge >> resistor leads to non-linearity and pwm frequency dependency. > > Oh, I had assumed the feed to the top of the opto H-bridge would be from > the top of the removed pot, so no additional supply would be needed, now > that the H-bridge resistances are low enough to obviate the need for a > buffer. That also automatically scales the output voltage for > compatibility. Yes, that is exactly the plan. What I am saying is that the circuit needs connections to both the pot high (maybe 100+ V above logic ground, with a KBIC controller) and to the computer +5V rail. Which means an extra wire not sourced from the P-port. -- atp "Torque wrenches are for the obedience of fools and the guidance of wise men" ------------------------------------------------------------------------------ Simplify data backup and recovery for your virtual environment with vRanger. Installation's a snap, and flexible recovery options mean your data is safe, secure and there when you need it. Data protection magic? Nope - It's vRanger. Get your free trial download today. http://p.sf.net/sfu/quest-sfdev2dev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
