Re: Sync gap strobe light...
>At 04:59 AM 6/29/99 -0400, you wrote:
>I see one potentially fatal problem with this design. Let's assume
>the cap charges to near the peak AC voltage minus maybe 3 volts for
>the LED drop on the positive swing. let's say 15 volts. On the
>negative swing, the LED must also serve as the blocking diode and
>thus is subjected to 15 + (12.6*1.414) = 32.8 volts. I've never
>seen an LED that will withstand that kind of PRV for long. To fix
>the circuit, just put another diode, say a 1n4001, in series with
>the LED and put one in reverse in parallel across the LED. The
>latter to limit the PRV on the LED to one forward diode drop.
>Other than that, nifty little circuit. Elegant in its simplicity.
John is absolutely right!
The LED is rated for 4.1 volts reverse voltage. I tested it on a curve
tracer and it breaks down in the reverse direction at about 30 volts (the
regular LEDs I tried went to ~200 volts!!! Wonder why they are rated so
low?). I will modify the instructions at my web site to add the two diodes
as John suggests. I wired them into the circuit and everything works fine
with them in there.