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  • DaveB98 commented on calincostelcoty's instructable Diy Arduino Laser Engraver9 months ago
    Diy Arduino Laser Engraver

    Thanks, In all the years I never came across using the 317 as a constant current source and to top it all off when I google it it's a very common practice! Going to go take all the DVD burner diodes I've saved and give this a try.

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  • DaveB98 commented on calincostelcoty's instructable Diy Arduino Laser Engraver9 months ago
    Diy Arduino Laser Engraver

    The power supply circuit does have some problems. The components are all there, it's just the connections that got a little messed up. The current for the laser diode should not run through the voltage divider. It should be connected directly to the output of the voltage regulator. The voltage divider should be connected between the output and ground (-V). The ADJ pin of the voltage regulator should then be connected to the junction between the fixed and variable resistor of the divider.That way the voltage regulator is not switched and is constantly outputting the required voltage, Depending on what you use for the laser diode you may also need to add a current limiting resistor in the current path of the diode. A quick search for LM317 will get you a data sheet that will give you info...see more »The power supply circuit does have some problems. The components are all there, it's just the connections that got a little messed up. The current for the laser diode should not run through the voltage divider. It should be connected directly to the output of the voltage regulator. The voltage divider should be connected between the output and ground (-V). The ADJ pin of the voltage regulator should then be connected to the junction between the fixed and variable resistor of the divider.That way the voltage regulator is not switched and is constantly outputting the required voltage, Depending on what you use for the laser diode you may also need to add a current limiting resistor in the current path of the diode. A quick search for LM317 will get you a data sheet that will give you information on component values. The 317 will supply up to 1.5 amps but will need a heatsink to do so. Bypass capacitors are not absolutely needed but will improve transient response. (voltage dips and spikes caused by switching the diode off and on).

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