How to drive green laser using an Arduino

[Johnyz]

Nope, like this:

 

[ar1999]

OK, here are the results:

With 4.5V power adapter ON (and Arduino ON):
up to 4.1 volts (laser lights up and blinks as expected)
up to 490mA (laser lights up but do not blink - stays on forever...)

WIth 4.5V power adapter OFF (only Arduino ON):
up to 2 volts
up to 10mA
OBS: just for a comment: with this setup (power adapter OFF) obviously laser does not light up. BUt I find it strange to see 2 volts at the multimeter... Shouldnt it be 0 volts?

Also the result of 490mA gets me worried if my laser can take that without eventually blowing up...
Is there a way I can measure the maximum current it can take? (P.S.: I dont have any datasheet for that laser and I dont know the manufacturer and model)
I do have the 3.7V rated battery that came with the box and is recommended to use with it. But I prefer to drive it with a power adapter, so I dont have the headache of recharging the battery.

 

[Sigurthr]

With the multimeter hooked up as shown by Johnyz's post you should NEVER have the meter in current (mA / A) mode because that mode presents a short circuit to the driver. You may have just fried your driver.

Power your laser and the arduino, not just one. Hook everything up correctly but leave the multimeter disconnected and in VOLTAGE mode. Does the diode light? If it lases at all; pulse or constant, you're still ok. If it no longer lases at all you've fried either your diode or your driver or both by setting the meter to current.

If it lases hook your multimeter back up as shown and post the voltage it reads.

To measure the voltage ACROSS a component you have to connect your multimeter across that component. Voltage mode on a meter looks like nothing is connected to the devices you connect it to; in other words it can't fry them and generally doesn't load them down so they stop working. Current is never across a component but THROUGH a component, and to measure current through something you need to disconnect that component and connect the meter in SERIES with the component as if the two leads from the meter were just a piece of wire connecting the component to where it goes. Meters in current mode appear just like a solid piece of wire - a direct short - to whatever you hook them up to. You cannot measure voltages in series or currents in parallel with the component you are working on. Usually the incorrect hookup for voltage won't burn the meter or break what you're testing, but having it in current mode hooked up in parallel WILL almost always burn up the traces/fuses/components in the meter and fry it or fry what you're working on.

 

[ar1999]

It may have fried my laser... I hope not. It was an expensive laser.
Sometimes it shines dim and sometimes it shines all the way bright...
SInce it is shining bright sometimes, I hope this is just some bad hoked up wires
Again I would like to thank all of you guys that are helping me with this.
It is a dream come true for me and hopefully I will get this done soon.
I promise to share the result with you all, so you can have fun with it too!

regards,
Laser Harp Guy.

 

[ar1999]

Just a pre-production pic: here is my current setup (all parts for the Laser Harp Project connected and testing... )

I tried to post a youtube video last time but it seems it did not show. Just the link was there...
I have to figure out how to do that and then I will post some video of this project up to date.

:thanks:

 

[benmwv]

I'm suprised no one else has mentioned this, but a 300mw green laser is going to take alot more than 280ma, and a 1W green laser us going to take a hell of a lot more than 200ma.

If it only draws 200ma I doubt it's any more than 50mw. A real 1w green laser would draw around 3-4 amps, maybe more. A 300mw laser would draw over one amp.

 

[ar1999]

I measured with my multimeter and it seems to work with 490mA.
Label says 1W green laser, but since I got it from china, who knows...
I dont have a professional measure device to check it out for sure...
But it sure light matches without any mod on my part... I did the test.

 

[benmwv]

If it draws about 500ma then you are probably looking at around 150mw, maybe a little more.

Did you measure that directly on the power supply or through the transistor?

 

[ar1999]

If it draws about 500ma then you are probably looking at around 150mw, maybe a little more.

Did you measure that directly on the power supply or through the transistor?

I did measure Amps through the transistor as shown in Johnyz's picture, and almost short out my laser... as Sigurthr explained I should NOT do that measuring Amps (only for volts) ...
Anyway it said 490mA, and 4.1 volts.

Did you measure that directly on the power supply

WHat do you mean by that? (sorry, english is not my native language and also I am not a professional with this stuff...)
I did use the power supply during that measurement (4.5 volts 2.5A) and not the batteries.

 

[benmwv]

Try measuring the amperage with the arduino and transistor out of the circuit.

Use your 3.3v supply and hook the laser minus to the supply minus, then with the meter in amperage mode put one wire of the meter to the laser plus and the other wire to the supply plus. That reading will be what your laser actually draws.

 

[Johnyz]

If the laser turns out to be over 500mA, I would suggest switching over to a to a bigger transistor, too.

 

[Sigurthr]

Aye, 2N222A's are limited to 600mA. The "How to Pulse A Laser" thread has info about higher current transistor options.

 

[ar1999]

Ok, here are some new measurements without the Arduino and the 2N2222:

1) Using just a 3.3 DC Power Supply and the green laser:
result: 180mA ( laser shines)

2) Using just a 4.5 DC Power Supply and the green laser:
result: 530mA (laser shines brighter)

3) Using just the factory supplied recommended battery labeled: "3.7V" (rechargeable) but measuring 4.1 Volts with multimeter:
from 410mA to 440mA (medium voltage with peaks of 480mA) = laser shines bright.

So now I am not sure how much voltage and current I should feed the laser so I dont risk blowing it?

 

[Sigurthr]

Looks like 425mA @ 4.2V (top voltage from a Li-ion cell) will do fine.

 

[ar1999]

Looks like 425mA @ 4.2V (top voltage from a Li-ion cell) will do fine.

Problem is I dont want to use batteries, but a power adapter instead (so I dont have to worry about recharging batteries).

I have an old voltage regulator I built using a 4.5 power adapter.
Now want to use it with a 5 VDC power adapter instead (its smaller and it is what I have at hand now).
Here is the schematics with the 2N2222 to pulse it.
How can I adjust it to fit those 425mA @ 4.2V you recommended?

 

[Sigurthr]

Oh boy, do I hate pictoral schematics. Got a good old line drawing one? Looks like the one you posted is wired up incorrectly (if I'm reading it correctly, anyway the values for your trimpots and caps are wrong).

I'll draw something up for you quickly.

Edit:

I just noticed, you might be referring to an OEM Green DPSS Module, which would have a constant current driver built in. If that is the case you do not need to regulate the current, only supply enough of it. What laser are you using?

You can't use a 5v power supply to power a LM317 based constant current source for a module (or diode) that requires 3.7V input. You would need a 6.7V power supply.

This is not a problem if you are using a module that has a driver. I will draw up what you need to do.

That will drop the incoming 5V to 4.3V for your module, which if it was meant to run off a 3.7V Li-Ion cell, is exactly what it needs. Li-Ion cells supply 4.2V when fully charged, and 3.7V when run down.