Sync gap strobe light...

Hi All,

	While watching the input of a switching power supply today at work, I had
a "brainstorm" about the sync gap strobe thing.  Then I read all the great
suggestions many people gave and combined them into a neat little design.

	When a transformer charges a cap through a diode, it pulls current as a
series of sharp current spikes at the peak of the AC waveform *:-)  By
replacing the diode with an LED and doing a little tuning to keep the RMS
current right (so the LED is bright) and keeping the peaks within the LED's
ratings, and then playing with the values on the computer (MicroSim) to get
the peaks to line up just right the to AC waveform peaks, I got a very nice

I made a zip file with some pics of the rough layout and details at:


	All the parts are from Radio Shack and can be had for about $11.  I will
put it into a nice metal grounded box when finished.  The big Radio Shack
LED (276-0206) is super nice and bright and is focused so it can shine at a
few feet very well.  the pulse is about 2mS wide and is about 3 degrees
before the AC peak which is no big deal.  I could probably get the peak
sharper but it seems to work well as is.

	The design should be fool proof but don't change any of the values or
things may go bad.  R1 is a current limiter and help get the pulse times
just right.  R2 provides a load so the cap discharges just the right amount
to need more charge at each cycle.  C1 is a cap that likes to draw spikes.
D1 is the big LED.  T1 is a small 12.6 volt AC transformer.

	Many many thanks for all the great ideas!!  I was going to use a white LED
till I saw the post about the phosphor in them.  The Radio Shack LED is
perfect for this.  There are other similar circuits that should work well
too but this is were I ended up...