Thanks for the reply, The 2nd option sounds OK. I'll still need to create a 12Vdc supply for the filter circuit and opamp buffer. Any other suggestions for generating the 12V supply from the 120Vac input. My plan is to use a Zener and series power resistor to drop the voltage. Peter Homann mailto:Peter.Homann@adacel.com Adacel Technologies Limited, 250 Bay St, BRIGHTON, 3186, AUSTRALIA http://www.adacel.com Telephone +61 (3) 8530 7777, Facsimile +61 (3) 9596 2960 Mobile 0421-601 665 -----Original Message----- From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Wouter van Ooijen Sent: Friday, 29 November 2002 11:54 AM To: PICLIST@MITVMA.MIT.EDU Subject: Re: [EE]: Generating an isolated 0-10Vdc voltage > The question is how do I isolate the output voltage. The > voltage is to drive > a 90V DC motor controller where the controller ground is live. Use a dual optocoupler. I don't know what the term is for this circuit, but the second coupler is put in the feedback loop on the HV side to make the transfer independent of the coupler's characteristic, provided that the two couplers have the same characteristic. Or (avoid the problem instead of solving it) put the PWM signal through an optocoupler (or trafo), do the filtering on the HV side. Wouter van Ooijen -- ------------------------------------------- Van Ooijen Technische Informatica: www.voti.nl consultancy, development, PICmicro products -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads