Connect with us

Laser diode power questions

Discussion in 'LEDs and Optoelectronics' started by Scott Johnson, Jan 30, 2018.

Scroll to continue with content
  1. Scott Johnson

    Scott Johnson

    4
    0
    Jan 30, 2018
    I'm playing around with a 30mw laser diode. It says that it's 5v input. I'd like to eventually power this with batteries. However, with my desktop AC power supply I have it set to 4.5v DC for testing and it seems that it works ok. It may be a little dimmer than I'd have hoped though.

    So two questions
    1) If I run 3 x 1.5 v DC (3 AA batteries) straight to the diode, do I have to worry about burning out the diode
    2) If I wanted to run 4 x 1.5 v DC (4 AA batteries) is it as simple as adding in a resistor to bring the power from 6v to 5v? If so, how do I calculate the resistor?

    Thanks!
     
  2. kellys_eye

    kellys_eye

    4,275
    1,147
    Jun 25, 2010
    Have you looked at the manufacturers data sheet for the device? What is the actual device number?
     
  3. Scott Johnson

    Scott Johnson

    4
    0
    Jan 30, 2018
    Unfortunately, no. I don't know what the device number is... It came from China and it didn't come with spec sheets.
     
  4. davenn

    davenn Moderator

    13,877
    1,964
    Sep 5, 2009
    does it already come with a driver circuit ?
    if not you will need to get/build one and without spec's that's going top be really difficult ....
    you cannot just put voltage from a battery/other PSU straight across the diode, you will damage/destroy it
     
  5. Scott Johnson

    Scott Johnson

    4
    0
    Jan 30, 2018
  6. kellys_eye

    kellys_eye

    4,275
    1,147
    Jun 25, 2010
    Without knowing what they are actually using as a current controlling device it isn't reliable to operate it at anything other than the voltage specified. If they genuinely mean '5V' then it's likely that it's just a series resistor to limit the current - pretty crappy as far as laser diodes are concerned. A decent driver would be constant current and have a wide(ish) voltage range.

    Stick to 5V (or as close to it as you can) - a 4.5V battery will be ok, use a 6V battery by fitting a series diode (to drop 0.6V) or a low drop-out regulator for higher voltages.
     
    BobK and davenn like this.
  7. Bluejets

    Bluejets

    5,026
    1,048
    Oct 5, 2014

    Attached Files:

  8. Externet

    Externet

    775
    168
    Aug 24, 2009
    The one on the Ebay link is a module containing a laser diode and driver circuitry. It regulates the laser current for variations in supply voltage. How big can the variations be is in the always absent chinese data sheets, but perhaps can be found for similar modules/schematics.
     
  9. davenn

    davenn Moderator

    13,877
    1,964
    Sep 5, 2009
    as long as it is the SAME as the one in the link .... SIMILAR mite be a dangerous assumption ;)

    indeed it does say driver :)


    Dave
     
  10. Scott Johnson

    Scott Johnson

    4
    0
    Jan 30, 2018
    So it will be a diode to drop the voltage down .5 volts and not a resistor?
     
  11. Externet

    Externet

    775
    168
    Aug 24, 2009
    If the laser pointer was meant to be used only with a fixed voltage as "5V", a resistor would suffice and the chinese would not spend half a penny extra in its manufacture implementing circuitry. But the driver circuit implies the constant current is produced from the components, so it should accept varied voltages as in aging batteries. How varied is the question, as there is a few style boards used in pointers/modules and perhaps someone else can find their schematics to learn variables, or reverse engineer :
    ----> https://duckduckgo.com/?q=laser+pointer+driver+board&t=canonical&ia=images&iax=images
    The constant current setting potentiometers are another section of the driver circuitry, not necessarily telling the input V range.

    To my suspicion, these cheap pointers should be capable of handling 12V input, their internal regulator will take care of that.
    If smoke escapes, they are available at the 99 cent store.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-