On 7/30/05, Russell McMahon wrote: > > How large is the transformer ? > > A transformer is a very eledgant solution, technology notwithstanding. > You can get very small main transformers - certainly under 25mm^2 > footprint. > Jinx may be able to comment due to recent similar experience. Using a transformer it's still an old methode for our days having only the disadvantage of PCB space consuming and a magnetic field generator. > > An alternative is a purpose build double tx, single rx opto made for > this sort of task. There are a number available. The sender uses a > feedback loop to contioj the sending signal and the receiver slaves > this. Opto tx drift not a problem. Why double tx ? A PIC running floated on to 230V mains with an optoisolated full duplex communication (half duplex on 2 wire EIA485 or whatever). I have a few projects running this way. > > Infineon HCNR200, HCNR201 > "High-Linearity Analog Optocouplers" > 0.01% non linearity > The light side of the force at work. > > Clare AN107 Linear Opto Couplers (Google knows) > LOC110. LOC111. LOC112 > Techniques apply to other manufacturer's products. > > I have often thought that you could probably do an OK version of this > using a std dual opto IC. And at least one operational amplifier. It works very good, is temperature compensated. On the nonisolated section (mains) the voltage is converted into current using a simple resistor. On the isolated section a middle supply voltage is negative feedback controlled by an OA and two photo-transistors. Two more resistors required to fix the middle voltage of the supply. It works very nice and is cheaper than any optoisolated amplifier factory made. cheers, VAsile -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist