Help with Evaluating Laser Modules

Discussion in 'General Electronics Chat' started by CoachKalk, Jul 8, 2012.

  1. CoachKalk

    Thread Starter Member

    Sep 20, 2011
    I am making great progress on my laser maze and have started to hook up my 532 nm 5mW lasers.

    I am beginning to wonder if my great deal on ebay may backfire a bit. I have asked a few questions from the seller and have received no answer, so I am wondering if someone here can give some advice.

    The spec sheet for the modules states: Working Current 280<mA @ 3V input.

    I have a 5V 4A supply that I have been using. First, I will explain what I did to size the resistors and then I have a few questions (assuming the first part isn't whacked).

    I assumed a 3V drop since that was the specified input V. The power supply measures 5.14V so I came up with 5.14-3 = 2.14V. I then divided by .28A and the result was 7.64 Ohms. I went with the standard 10 ohm resistor.

    Several of the modules were very dim or not lighting at all (I could see they were trying - red glow, but no light). After double checking my calculations, I realized the 10 ohm resistors calculated at 214 mA. My thought was perhaps I was not providing enough current, so I used two 15 ohm resistors in parallel to get 7.5 ohms.

    This seemed to help as I was able to get a few to provide good light, but several can still not be used.

    In all cases, when I quickly use a straight 5V supply, each and every module lights great - I only verify light and shut off asap.

    I have tried to get clarification regarding the way the working current is listed: 280<mA @ 3V. So, without getting feedback from the seller, I am looking for some guidance.

    Would the 280mA be a minimum required for operation?
    Is there a typical range that laser modules have with regard to current?
    Is it a tradeoff between brightness and module life?
    I realize every module will not be the exact same, so am I stuck with trying each one or is there some way to use my meter to determine the units that seem to require more than 280mA?

  2. bertus


    Apr 5, 2008

    Can you post the datasheet of the devices?

  3. CoachKalk

    Thread Starter Member

    Sep 20, 2011
    This is the only info posted on the auction. I cannot get the seller to respond, so this is all I have at this time.

    Power output​
    5mW with 10% tolerance​
    Working Current​
    280<mA at 3.0V input
    Electronical Pole​
    Copper burl to"+" and Spring for "-"​
    Working Temperature​
    Storage Temperature​
  4. bertus


    Apr 5, 2008

    Does it say that the laser is voltage or current controlled?
    If they act like leds, they are probably current controlled.

  5. CoachKalk

    Thread Starter Member

    Sep 20, 2011

    First, even though I am unable to provide you with any answers to your questions, I appreciate your attempts at helping. At this time, I just have no other info.

    Would you be willing to offer a brief "what if" scenario/difference between being current controlled versus voltage controlled?

    I obviously do not want to fry the laser after 30 seconds, but there seems to be quite a range of current needed to get these things to light.

    I was considering using a pot to dial in the lasers. Is that a feasible option, in your opinion? Other than just looking at the result (laser brightness), I am not sure how to dial in each laser.

    I do have a laser temp gun that I could use to determine if the module temp is going through the roof. I am not sure if that is a realistic/reliable way to check though.

  6. Wendy


    Mar 24, 2008
    My understanding is they are current controlled devices, similar to LEDs, except more fragile.
  7. steveb

    Senior Member

    Jul 3, 2008
    First of all, don't do this. (at least not yet) If the device does not have additional circuitry, and is just a straight current controlled device, then you likely damaged the devices by doing this!

    It's possible that a current limiting resistor, or a current source circuit are already installed in the module, in which case, it might require 5 V or more. However, if this is just a straight diode device, then you should drive it with a current source, as mentioned by others above.
    Last edited: Jul 8, 2012
  8. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    Solid state lasers can be destroyed in an instant if you do something silly like touch PSU wires onto the laser, EVEN IF you have a resistor. This is because they are very sensitive to static and spikes.

    Once destroyed by a spike they will light up but be very dim, and may also flicker.

    The first thing to do with a new laser is use grounded tools and solder a 0.1uF or 0.22uF cap across it leads. After that they are a bit safer to handle, but even then it's advisable to be careful with static and just don't go touching leads onto things when the leads have power! Connect the leads when powered down and then turn the switch or PSU on.
  9. CoachKalk

    Thread Starter Member

    Sep 20, 2011
    Unfortunately, I may just have to bite the bullet and look into different laser modules. I currently have 9 working very good with the 2 15 ohm resistors in parallel.

    I think I have been fortunate not to have destroyed any yet, because they have all lit up as/when I lower the resistor used (some need more lowering than others).

    I think I will just play with different resistor values for the oddball lasers and hope for as long as life as I can get. Currently they are of no use to me now anyway.

    Thanks everyone for your input/advice.