Re: Sync gap strobe light...

• To: tesla-at-pupman-dot-com
• Subject: Re: Sync gap strobe light...
• From: Terry Fritz <twftesla-at-uswest-dot-net>
• Date: Tue, 29 Jun 1999 17:13:48 -0600
• Approved: twftesla-at-uswest-dot-net
• Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme
• In-Reply-To: <37788B0C.8821E14A-at-bellsouth-dot-net>
• References: <4.1.19990628192030.00a1b750-at-pop.dnvr.uswest-dot-net>

>At 04:59 AM 6/29/99 -0400, you wrote:
>snip...
>
>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
>


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.

Thanks John!

	Terry

• Sync gap strobe light...
• From: Terry Fritz <twftesla-at-uswest-dot-net>

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