At 09:09 AM 7/6/2009, Mark Scoville wrote: >Hi Piclisters, > >I have a project at work that I need to test while powered from 120Vac 50Hz. >All I have available in the USA (Cleveland, Ohio) is 60Hz. Does anyone have >any clever and inexpensive ideas for how to generate 120Vac 50Hz? I need >about 4 amps to do my testing. > >So far my thought is to buy a "Modified Sine" inverter ($100) that runs off >12Vdc and produces 220Vac at 50Hz. Then I could step down the 220Vac using a >transformer (which we already have). It's not very elegant, and not ideal, >but this is only needed for a few days of testing and then will probably sit >on a shelf for 20 years getting dusty. Many of our local stores sell vehicle power inverters - I'm thinking of Canadian Tire but there are others. 400 Watt 120V inverters go on sale for about Can $25 on a regular basis. I also purchased a 1000 Watt model for Can $75 a couple of years ago. Its a very simple process to go inside and change a single resistor to move the output frequency from 60 Hz to 50 Hz. The downside of using those cheap inverters is that the so-called modified sine wave output is really nothing more than a 150V peak square wave with lots of dead time. They do it that way so that the peak and average values match a real sine-wave source. It actually works quite well but you need to be aware of the limitations. FWIW - we purchased about a hundred of those cheap 400W inverters last year - we go inside and grab the regulated 150Vdc for use in one of our pipeline transmitters. Same deal as with lots of other stuff - we can't purchase and assemble a 150 Vdc 4 Amp dc-dc inverter for anything close to $25. dwayne -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist