zoomkat:
Chagrin:
I've driven a cheap laser pointer using a transistor without issue. No problem switching it at 38KHz for use with an IR receiver.
Interesting. How sensitive are the IR receivers to the visible red spectrum of the cheap laser pointers?
That's a tough question to answer; given the nature of the coherent beams of lasers it should be sensitive at "any" distance. I quickly got a signal at ~12 meters distance (the longest clear span in my house) without tweaking the laser focus, frequency, or power and didn't take it any farther. My goal was only to build a laser tripwire and I wasn't attempting long distance communication.
Grumpy_Mike:
Read this for driving a laser:-
Sam's Laser FAQ - Diode Laser Power Supplies
That's too much info. Why can't I buy some cheap, green laser from eBay and rapidly turn it on/off using a digi out pin (assuming the voltage is not more than the required amount for the laser)?
Why can't you? Lol try it or search online if someone did before, I haven't tried it(couldn't get it open) and don't know of anyone who did
David82:
Why can't I buy some cheap, green laser from eBay and rapidly turn it on/off using a digi out pin (assuming the voltage is not more than the required amount for the laser)?
It's not the voltage, in that case - it's the current.
Do you have a laser pointer or a similar, simple laser module (5V or 3V) at hand?
Getting something done with a low-power module will be a lot easier than something "high-power".
There's not a PnP, "one-size-fits-all" solution for you.
That's too much info.
That makes me sad.
You can't be bothered to read this simplified web page. What ever makes you think you are going to understand what to do.
Why can't I buy some cheap, green laser from eBay and rapidly turn it on/off using a digi out pin
Well that page would have told you.
(assuming the voltage is not more than the required amount for the laser)?
Hint:- it is.
Grumpy_Mike:
(assuming the voltage is not more than the required amount for the laser)?
Hint:- it is.
If the laser wants 3v, then I just add the appropriate resistor right? Problem solved. Is there something I'm missing or is it not that simple? If I am missing something, why can't it be mentioned in one or 2 sentences? Like this, "That won't work because X, Y, Z"
That's a tough question to answer; given the nature of the coherent beams of lasers it should be sensitive at "any" distance. I quickly got a signal at ~12 meters distance (the longest clear span in my house) without tweaking the laser focus, frequency, or power and didn't take it any farther. My goal was only to build a laser tripwire and I wasn't attempting long distance communication.
Did you use a modular IR receiver like is used in typical home IR remote controlled electronics? If so, which particular one did you use?
If the laser wants 3v, then I just add the appropriate resistor right?
Wrong.
why can't it be mentioned in one or 2 sentences? Like this, "That won't work because X, Y, Z"
This won't work because a laser presents a varying impedance to the thing driving it and so a simple resistor will not be able to give it the constant current it needs.
Grumpy_Mike:
why can't it be mentioned in one or 2 sentences? Like this, "That won't work because X, Y, Z"
This won't work because a laser presents a varying impedance to the thing driving it and so a simple resistor will not be able to give it the constant current it needs.
ok, then I figure you would just use a transistor in between the laser driver and the laser diode. That way the driver always has power applied to it and the diode would just be rapidly swtched on/off. Would that work?
I have used this exact circuit
to control a low-power 3V laser module (inset).
Cool. Did you just use that circuit simply for powering it or did you use it to rapidly flip it on/off over and over?
It was in a blinking application of sorts, a "low" frequency with a narrow pulse "on" (low duty) - a great success.
I have used this exact circuit
Interesting circuit. Did the laser module require any external current limiting?
I got the modules from ebay, they have circuit boards already (you can sort of see it stuffed in in the picture up there). So, all they need is a supply voltage.. and you can run around and be irritating.. or do something constructive.. as the spirit moves.
and you can run around and be irritating.. or do something constructive.. as the spirit moves.
Bad day at the Pancake House?
[quote author=Runaway Pancake link=topic=105616.msg793298#msg793298 date=1336944454]
It was in a blinking application of sorts, a "low" frequency with a narrow pulse "on" (low duty) - a great success.
[/quote]What was the actual reason why you couldn't you just use a digi out pin and the appropriate resistor to switch the laser on and off? What would've been the result if you tried to do it the way I just described?