next topic »

[Reply #15 on:]

The Transistor as Switch section shows setup. Also read the "Connecting a transistor from the output of an IC" for an explanation of what's going on. Heck, read the whole page and you'll be a lot smarter in the end

The current drawn by a laser pointer is very low so pretty much any N-channel transistor you have will work.

[Reply #16 on:]

Something like this?

Yes! Exactly.

Something you might have to play with is finding the right photo-transistor; most are at best sensitivity in the IR region (look at the datasheet), but you can get ones that are sensitive in other bandwidths.

[Reply #17 on:]

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?

[Reply #18 on:]

The Transistor as Switch section shows setup. Also read the "Connecting a transistor from the output of an IC" for an explanation of what's going on. Heck, read the whole page and you'll be a lot smarter in the end

The current drawn by a laser pointer is very low so pretty much any N-channel transistor you have will work.

Why do I need to use a transistor? If the end result is still the laser being rapidly cycled then what's wrong with just using one of the digi out pins?

[Reply #19 on:]

Probably the current drawn is too high.

[Reply #20 on:]

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.

[Reply #21 on:]

Read this for driving a laser:-
http://www.repairfaq.org/sam/laserdps.htm

[Reply #22 on:]

Read this for driving a laser:-
http://www.repairfaq.org/sam/laserdps.htm

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)?

[Reply #23 on:]

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

[Reply #24 on:]

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?

[Reply #25 on:]

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.

[Reply #26 on:]

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.

[Reply #27 on:]

(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"

[Reply #28 on:]

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?   

[Reply #29 on:]

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.