Ok, I am programmer and not really too familiar with electronics and circuits and was wondering how I would power a set
of AlexP’s lasers? or in a sense how I would wire them up? I have read that people could use a old power supply that has
the correct voltage, but how do I know which wire on the power supply is negative versus positive? Also when I went
to Radio Shack, one guy suggested I could just use a battery pack to power something that only need about 5V, which
is what AlexP’s lasers require. I am not sure if this is a very good solution though.

The other question I had is about voltage regulators? Is there a way to maybe only use one power supply and have it powering
both lasers with a voltage regulators?

Here are the stats for AlexP’s lasers just for reference.

- 850nm laser diode with 10mW (max power)
- Laser diode power supply circuit (photo-diode feedback LD current control)
- Focusable line with 120° spread using a special non-linear lens (even brightness)
- Variable voltage supply 3.5V-5V

Gooswa - 23 July 2008 01:14 PM

Ok, I am programmer and not really too familiar with electronics and circuits and was wondering how I would power a set
of AlexP’s lasers? or in a sense how I would wire them up? I have read that people could use a old power supply that has
the correct voltage, but how do I know which wire on the power supply is negative versus positive? Also when I went
to Radio Shack, one guy suggested I could just use a battery pack to power something that only need about 5V, which
is what AlexP’s lasers require. I am not sure if this is a very good solution though.


The other question I had is about voltage regulators? Is there a way to maybe only use one power supply and have it powering
both lasers with a voltage regulators?

Here are the stats for AlexP’s lasers just for reference.

- 850nm laser diode with 10mW (max power)
- Laser diode power supply circuit (photo-diode feedback LD current control)
- Focusable line with 120° spread using a special non-linear lens (even brightness)
- Variable voltage supply 3.5V-5V

Black is (usually) negative and red is positive. As well as the rating in Volts, you should also have a rating in milliamps, this will tell you whether you can power more than one laser from a single adapter. For example I just had a look at an old nokia charger and it gives the rating on the plug as 5V / 890 mA (5 volts / 890 milliamps) So for example, if your lasers use 400 mA each then you could power two from the same adapter, since 2 x 400mA is less than 890mA.

I wouldn’t try to use batteries as I imagine they will drain really quickly. I used some high power ir leds for a beam breaker once and they drained 9v batteries in just a few hours.

Make sure you use IR safety goggles even when wiring up your lasers as you won’t know if they are working or not…

technodai - 23 July 2008 02:53 PM

Gooswa - 23 July 2008 01:14 PM

Ok, I am programmer and not really too familiar with electronics and circuits and was wondering how I would power a set
of AlexP’s lasers? or in a sense how I would wire them up? I have read that people could use a old power supply that has
the correct voltage, but how do I know which wire on the power supply is negative versus positive? Also when I went
to Radio Shack, one guy suggested I could just use a battery pack to power something that only need about 5V, which
is what AlexP’s lasers require. I am not sure if this is a very good solution though.


The other question I had is about voltage regulators? Is there a way to maybe only use one power supply and have it powering
both lasers with a voltage regulators?

Here are the stats for AlexP’s lasers just for reference.

- 850nm laser diode with 10mW (max power)
- Laser diode power supply circuit (photo-diode feedback LD current control)
- Focusable line with 120° spread using a special non-linear lens (even brightness)
- Variable voltage supply 3.5V-5V

Black is (usually) negative and red is positive. As well as the rating in Volts, you should also have a rating in milliamps, this will tell you whether you can power more than one laser from a single adapter. For example I just had a look at an old nokia charger and it gives the rating on the plug as 5V / 890 mA (5 volts / 890 milliamps) So for example, if your lasers use 400 mA each then you could power two from the same adapter, since 2 x 400mA is less than 890mA.

I wouldn’t try to use batteries as I imagine they will drain really quickly. I used some high power ir leds for a beam breaker once and they drained 9v batteries in just a few hours.

Make sure you use IR safety goggles even when wiring up your lasers as you won’t know if they are working or not...

Yeah I am getting my goggles on Friday, so I am going to start doing testing then.
So the only part that matters in this situation is the voltage correct? How do I know
how much mA the lasers are using? The other thing is a have a few adapters that
don’t even have a two colors, just all black.

Do you have a multimeter (if not you should pick one up anyways)? If so then you can just plug in the adapter and test the voltage. You’ll want to do this if you’re planing on cutting off the plug and wiring directly to the lasers.

Otherwise, if you look at the power adapter, you should see a symbol like on of the following

This tells you the polarity of the connector on the end of the cord. The partial circle is the polarity of the outside the connector, and the dot is the polarity inside the connector.
You can then pick up a coaxial DC power jack that’s the same size as the plug, and solder it according to the polarity of the adapter. RadioShack has some, but you can probably find a better deal, or even salvage one from something else.
This is also the cleaner way to connect up the power, but if you don’t mind cutting off the plug and having the adapter permenantly connected then the first method will work just as well (and cheaper if you already have a meter).

Unfortunately most adapters nowadays use coaxial instead of two wires. It means that inside the wire there are two layers, one is positive and one negative. It’s a real pain in the proverbial to try and rewire once it’s been cut so I’d have to recommend spbogie’s suggestion above.

As for the question of milliamps, I suppose the best person to ask would be Alex P!

Cool, So I found one that is 5V & 2.5A and have a millemeter that gauged at 5.36V, and it has the polarity on the charger.
I would think this would do fine for powering at least one wire? or would I be able to power both lasers?