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setting up flexmod drivers

ndrew2505

ndrew2505

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i got 2 flexmods from drlava today and began trying to get them setup for my scanner. i can seem to get the current set for the bias but not for the gain. unless i misunderstood the sheet that came with it im doing it right but when i try to test the bias i dont get any current at all. anyone know what i may be doing wrong?
 





ok so i figured out what i was doing wrong.. :/

anyone know how i should set up the bias to gain ratio? im also guessing that it should be white balanced on both?
 
I just finished setting up my Flexmod driver. The standby current is set by the 0bias pot with the mod wires shorted. This should be just below the lasing threshold but not zero. Here is a quote from Drlava that helped me quite a bit,
"Yes the Mod + input can be connected to the 5V+ of the power supply, no problem. It won't draw much current.
The Mod- IS the same as the Power - which is to be connected to gnd on the power supply.
The standby current is below lasing threshold, the 'blanked' current of the diode whether TTL or Analog modulation input. The standby current should not be zero, and should not be lasing.
Yes, you should re-check the standby current after setting the max modulation current.

Another thing to remember is to isolate the diode from ground always. Never connect the diode to a powered driver. Discharge the capacitor after the power is off or wait a minute before connecting the diode. Don't touch the bottom of the driver while it is operating. It contains sensitive circuits and the conduction of your skin may cause a current spike.

I highly highly yea verily DO IT! recommend setting this up with a test diode first, say an open can, and getting comfortable with the way things should work. Don't rush in and try to learn how to use the FlexMod with a new expensive diode. Once you are comfortable with it and have tested out modulation, then you can move to the expensive diode."

Thanks for all of your help DrLava.
 
ndrew2505 said:
ok so i figured out what i was doing wrong.. :/

anyone know how i should set up the bias to gain ratio? im also guessing that it should be white balanced on both?
Click to expand...
What do you mean by white balanced? If you're referring to setting the laser to give the best white color balance, you could do that but I recommend just using the controls in your software to adjust white balance.

Also, I was informed awhile back that if you use Flexmods you need to make absolutely sure that your incoming modulation signal never exceeds 5V. As the incoming signal ramps up, so does the laser's power. The issue is that as the signal exceeds 5V, the laser continues to get fed more current. There is no safety, so you could potentially blow a diode if the modulation voltage is not set precisely. With most commercial DACs, you won't have to worry about it since the modulation voltages are set, but if you use a soundcard DAC this is very relevant.
 
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The Current revision of FlexMods do have protection for over 5V input. It cuts out at about 5.2V after that the current dies not rise.
 
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