Laser On/Off problems

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07-25-2009, 14:54
Laser Ben

Laser On/Off problems

Hey Everybody,

I am working on a projector for a friend and I have been having problems with the Lasever 150mW green laser on it, it seems to cycle on and off every couple seconds, it is really strange, I have never encountered. I have checked the modulation input, and it is getting a stable 5V input with no fluctuations, the input is NOT a square wave like the graph appears to show. The laser does not do this until after it has warmed up, ~2-5 minutes.

Does anyone have a clue what could be causing this?

http://farm4.static.flickr.com/3522/...e718aae9_o.jpg
07-25-2009, 15:50
fuzcub

If the red LED on the driver board is blinking/flickering then the Lasever laser thinks it's overheating. If this doesn't seem true, then there might be electrcal noise on the 5v supply that's effecting the temperature controller.
1/Scope for noise on the supply
2/ Make sure that the mod ground is attached to supply ground
3/ Make sure the head is electrically grounded and very well thermally heatsunk
If that fails, trimpot VR4 sets the temp cutoff, I think anticlockwise raises the cutoff point. Adjusting this will void your warrentty unless instructed to by David @ Lasever.
Barney.
07-25-2009, 17:16
Laser Ben

Thank You! I will test that out in a minute, I am guessing it may be an overtemp issue because the driver gets quite hot.
07-26-2009, 04:27
mixedgas

Quote:

Originally Posted by Laser Ben

Thank You! I will test that out in a minute, I am guessing it may be an overtemp issue because the driver gets quite hot.

If this is a external switching power supply that powers a driver board, put the PSU on a load that draws the same or more as the laser drivers and let it set a while, open circuit voltage being five volts does not mean there is not a problem with a switcher, and when switchers start to fail they burst on for a few seconds , loose regulation, reset, then shut down and try a restart with a period of a few seconds as you describe. I've seen this over many years and with many brands of switcher psu, so I strongy urge you to isolate the switcher from the laser and load test it for a long period of time. The next phase if it is the switcher doing this is catastrophic failure with overvoltage output. You have to put the switcher on a large dummy load (lightbulb, power resistor) and watch it with a scope.

Steve