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Old 08-12-2009, 11:15 AM   #2180 (permalink)
NiHaoMike
Master EcoModder
 
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Quote:
Originally Posted by mcudogs View Post
Application note for a linear optocoupler circuit is http://www.clare.com/home/pdfs.nsf/www/AN-107.pdf/$file/AN-107.pdf. The problem with using this is that you have to derive a low voltage supply from the pack voltage to run the op amp on the battery side.

NiHaoMike, so the diac discharges the cap through the LED of the opto when the voltage across the cap reaches the diac breakdown voltage ~30vdc? The time taken to charge the cap depends on the battery voltage. Therefore the frequency of the pulses through the opto is relative to the battery voltage.

That is certainly a simple circuit. Do you have a working circuit we can borrow?
Start with a simple neon bulb blinker, replace the neon bulb with a diac (lower voltage for better linearity), and add an optoisolator or pulse transformer in series with the diac. The battery with the series resistor can be approximated as a current source, which charges the capacitor until it reaches the diac trigger voltage, causing it to discharge the capacitor through the transformer or optoisolator. The frequency would vary depending on the battery voltage.
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