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Laser Diode Project. Help!

Discussion in 'LEDs and Optoelectronics' started by John TM, Mar 9, 2015.

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  1. John TM

    John TM

    Mar 9, 2015
    I am trying to connect one hundred Laser diodes in parallel and need to know what is needed and how to build my circuit.

    These are the questions I have:
    Power Source Capacity?
    Do I need any other electronic component? Regulator, capacitors, resistors, etc?
    How should I build my electronic diagram?
    What is the best way to solder all these cables?

    These are the specs of the laser diodes and I am also attaching a picture of one of them so you can have an idea on how they look like.

    100 Laser diode 650 nm
    5 Volts DC
    5 mW

    Am sorry if I am asking for too much but really need to make this project happen so any help or feedback would be greatly appreciate it.

    Thanks for your time

    Attached Files:

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  2. Gryd3


    Jun 25, 2014
    100 of these suckers! Have fun soldering.. The best way is 'cleanly' . Keep the clutter and rats nest down and physically plan out where they are going.
    According to the specs, the 5mW lasers will draw 1mA of current each... this seems tiny...
    Do the lasers have a current draw spec? Do they have an onboard or built-in current limiting resistor?
  3. John TM

    John TM

    Mar 9, 2015
    They don't have a current draw spec and therefore I am almost certain that the built it limiting resistor is not present.?
  4. davenn

    davenn Moderator

    Sep 5, 2009
    if these don't have a built in driver circuit, then you will have to supply one for each diode

    laser diodes need a specific driver that normal LEDs dont
    Gryd3 likes this.
  5. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    You should not try to connect laser diodes in parallel, unless each diode contains a current driver integrated into the laser diode package. This could be something as simple as a current-limiting resistor. And that does appear to be the case for cheap Chinese knock-off laser diodes, such as the example you have shown.

    What happens when you connect just one of these diode lasers to a 5 V DC power supply? How much current is drawn? Does the laser "light up" or does it melt down? Do you have a part number or a datasheet for your laser diode?

    If the laser diode "lights up" with 5 V DC applied, you are home free. No other components needed. Just connect all the red wires together and then connect them to the +5 V DC terminal of a 5V DC power supply. Connect all the blue wires together and then connect them to the common of the 5 V DC power supply. This is assuming that a single laser diode "lights up" when its red lead is connected to positive terminal and its blue lead is connected to negative terminal of 5 V DC power supply. Be sure to verify this polarity first before going to all the trouble of wiring 100 of these "laser diodes" in parallel.

    Looks like you need a 5 V DC power supply capable of providing about 100 mA or 500 mW of power to operate one hundred 5 mW "laser diodes" in parallel.

    I would solder together twenty groups of five "laser diodes" and add a pigtail to each red and each blue wire in each group of five. Cover the soldered joints with shrink tubing. Use 60/40 lead/tin flux-cored solder and a pencil soldering iron with a spade tip. Make sure the tip is well-tinned with solder. Tie all the like-colored pigtails together and then connect them to the power supply terminals.

    You don't need an electronic diagram. This is like wiring light bulbs in parallel.
  6. John TM

    John TM

    Mar 9, 2015
    Thanks so much. The laser diode lights up when connected to the 5V power supply. I do not have a datasheet for the diodes. Again thank you this will keep me going.

  7. BobK


    Jan 5, 2010
    I expect that 5mW is not the electrical power drawn, but the optical power output. The electrical power might be 5 to 10 times that high.

    davenn and hevans1944 like this.
  8. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    Right! That's why the OP should measure the current drawn by one of them before trying to power up 100. I missed that, so thanks @BobK for pointing it out. Also, these diodes were apparently originally used in a laser printer where they were out of sight. 5 mW output power in the visible is enough to damage vision if intentionally directed into the eye. These are likely to be Class 3R lasers for which normal precautions apply: don't stare into the beam, etc.
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