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Thread: Sam'sFAQ driver mod for beam supression?

  1. #1
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    Default Sam'sFAQ driver mod for beam supression?

    Ok, so I've been doing a lot of research on how to design an analogue driver and I've decided to go with a modified design based off of the driver on Sam's Laser FAQ page (http://www.repairfaq.org/sam/ldschpcb.gif). I will use the same LT1215 op amp but I will replace the LM317 with an LM338T or similar for higher output current. I can't guarantee that the resistor and cap values will be the same since I will be making a few adjustments to the circuit in order to add a soft start feature, interlock, and a few other ideas I have. The one thing I want to add but have not been able to understand is how beam suppression works, particularly for the M140 and A140 445's. Can anyone help me understand how it works and how I might implement it into the circuit?
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  2. #2
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    the magical word is Hysteresis

  3. #3
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    I came across that when reading about threshold currents. I understand what it is but I guess not how it works. I'll read up on it some more. Thanks.
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  4. #4
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    Default

    Be careful with that one, it has a undefined current state at startup.
    It can source a lot of current till the opamp powers up and closes the loop.

    Steve
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  5. #5
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    What is the fix to prevent the current from flowing through the diode while the Op-Amps power up? Or does that require a totally different style of driver?

  6. #6
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    I've been considering integrating a 555 timer to the circuit to delay startup and and reset of the interlock. Perhaps I can wire it to shunt initial start up current through a resistor to ground or even just create an open output circuit which will close after a delay period.
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