104Views7Replies

### Author Options:

I bought an ebay 3.2vdc laser and want to power it with a 5vdc wall charger, will it work or do I need a resister? if so what size?

Tags:

## Discussions

The forums are retiring in 2021 and are now closed for new topics and comments.

If you are using a resistor switch box be extremely careful how you change a decade as there can be a serious current jump mistake at switch over.

Always Up then Down..

Lower the voltage using 3 Schottky diodes in series 3X0.6=1.8, 5-1.8=3.2

You can also buy a cheap DC down converter on eBay for about \$1, How many mW is it? I can give you a link to what you need if you tell me how many mW it is

Using a resistor... like, in series with the laser and the 5V supply. That might work.

Start by trying a resistor that is too big. Then check the voltage across the laser. Then try a resistor a little bit smaller than that. Then check the voltage across the laser again. Then repeat this process until you find a resistor that gives you voltage, across the laser module, less than or equal to 3.2 volts, with the laser module emitting light, which is probably the goal here, right?

Or if you have some idea for maximum current, then you can just calculate the size of your resistor from the expected voltage drop across it.

Note that if you pick a resistor that is too small, then the laser will probably get overpowered and die. But it was a cheap laser anyway. Or, at least, it didn't cost me anything. Ha!

I dunno. I think the usual solution for something like this is to use a voltage regulator, or use a 3 volt DC adapter, rather than a 5 volt one.

I am also guessing the actual amount of power, voltage times current, wanted by your laser is small; i.e. current for this is 10s of milliamperes, not bigger than that.

BTW, dumb question: Is this a laser module, like intended to run from maybe 2 AA bateries? Or is it a bare laser diode?

If it is laser module, then it wants constant voltage, similar to that which would be supplied by 2 AA batteries in series.

If it is bare laser diode, then it wants constant current, and the way you do that is either by using a true constant current regulator, or if it is only a small amount of current required, then you can just use a resistor in series with a constant voltage source, where the current is (1/R) times the voltage drop across the resistor.

What is your electronic skill set ?

There is a reason why you can buy a proper laser including the right power supply...
If you need to ask these question than I already know your knowledge of following a fix will not be sufficient.
Get a suitable constant current driver for your toy and add a suitable power supply.

resistors don't change voltage what you need is a constant driver circuit