How to pulse a laser?

ar1999 said:

You can pulse it using an Arduino and a 2N2222.
it has been discussed in this Forum. Here is the link:
http://laserpointerforums.com/f67/how-drive-green-laser-using-arduino-70770.html
There are some easy schematics down the post.
Also you can program the Arduino to pulse at the rate you want.
I would be happy to help if you want.

Click to expand...

The LM555 is a <$0.50 solution to Pulsing a LD without
the need to program a MCU.

Digi-Key - LM555CMFS-ND (Manufacturer - LM555CM)

It is a simple matter to add an inexpensive potentiometer
to get a variable pulse rate...

There is nothing wrong with going overboard to do a
simple job like pulsing a LD...


Jerry

Thanks Jerry! I like to think my circuit is a simple, versatile, and elegant solution. I always keep K.I.S.S. in mind... "Keep it Simple, Stupid!".

Sigurthr said:

Thanks Jerry! I like to think my circuit is a simple, versatile, and elegant solution. I always keep K.I.S.S. in mind... "Keep it Simple, Stupid!".

Click to expand...

K.I.S.S. has been one of our mottos for as long as I can remember....:beer:

Jerry

I bought a variable speed motor control kit back in the day, and it had a nice pot and was a 555-based PWM generator. Instead of using it to control a motor, I pulled the signal pin from the 555 to the on/off pin of the voltage regulator I was using to power an LED series-parallel array. It had the benefit of coming with a premade board with solder masking and silkscreening.

Ttl

I'm just wondering, because im going to buy a laser module, what would happen if i don't use the ttl intalled in the driver?

Most TTL-ready modules require you to apply 5V to the TTL line in order to turn the laser on. Some are set up to "TTL Blanking" though which turns the laser off when 5V is applied and those you can ignore.

i was thinking of buying the 150mW Industrial Red laser dode module/TTL from o-like.com. if i didn't use the ttl, would it affect the laser.:crackup:

So - I finally got all the parts in to reflow one of johnny's boards (a slight derivative of it).

I used fairly pricey (~$4 each) trimmers.

Before most of the solder paste had liquefied, the trimmers (SMD by the way) had already exhibited plastic warping.

What are you supposed to do with SMD components that can't handle the heat of reflow soldering ?!?

Well, I'm no pro, but things I would try:

Try using a solder paste that will flow at lower temperatures.

I would try "pre heating" the paste a bit once it's in place with a heat gun or a hot plate. The paste I use gets "runny" when it heats up a bit. Try heating it up and then place the component and use a heat gun to finish it off, OR maybe even heat the paste until it flows, place the component, then heat it up a bit more with a heat gun. Get the connections warm and remove the heat.

EDIT: Might even have to use a different component that can stand the heat better. :/

Ghostchrome said:

heat the paste until it flows, place the component, then heat it up a bit more with a heat gun. Get the connections warm and remove the heat.

Click to expand...

I think this suggestion by GC is probably the best option. After the other parts have reflowed properly, put the part on there and immediately cool it. Then, you can go over the joints quickly with a fine tipped iron to redo just those connections and ensure no cold joints.

Click to expand...

I am no expert but N-Channel transistor is for switching the ground connections.

How does that 2N2222 work switching the positive rail?

Shouldn't it be a P-channel one? :thinking::thinking:

like this:



THIS IS TESTED by me and works - you need to invert the pwm signal if necessary for your needs.
this is if you are using common positive rail with the IC, if using voltage for the driver you have to make something like this:

is it possible to get a higher output pulse from a 445 using short pulses? As long as the head is cooled properly.. just wondering if anyone has tried this.



It seems anything over 1800ma returns exponentially less results, but possibly in smaller bursts? or even a single charge burst like a pulse cannon?

foulmist said:

I am no expert but N-Channel transistor is for switching the ground connections.

How does that 2N2222 work switching the positive rail?

Shouldn't it be a P-channel one? :thinking::thinking:

Click to expand...

It works quite well with the NPN, gotta remember a switch is a switch in this application. Sure they may be used in ground rail switching but that certainly isn't a requirement at all. NPN requires the base to be more positive than the Emitter to be turned on, PNP requires the base to be more negative to be turned on, so if you're driving with a squarewave or PWM your transistor choice determines the signal inversion factor. A 20% duty cycle pwm w/ NPN = an 80% duty cycle on PNP. Personally I prefer NPN for just about everything I can work it in to. They're easier to find and there are loads of alternatives.

Hargak said:

is it possible to get a higher output pulse from a 445 using short pulses? As long as the head is cooled properly.. just wondering if anyone has tried this.



It seems anything over 1800ma returns exponentially less results, but possibly in smaller bursts? or even a single charge burst like a pulse cannon?

Click to expand...

You need to remember a main limiting factor in high power diode lasers is not the current but the amount of light produced. Catastrophic optical damage to the cavity is the primary failure mode, not thermal stress. That being said a very fast low duty cycle pulse can be used to produce a higher output power but there are NO gains for our puposes. 10% d/c at 10x output power produces the same energy deposition at the target as 100% on at normal output power. It would also appear to be equally bright to your eyes. The increased complexity of driver design and increased stress on the diode usually negates any thermal benefits. I seem to remember having a chat with one of our vets about this recently as well, hehe.

Sigurthr said:

It works quite well with the NPN, gotta remember a switch is a switch in this application. Sure they may be used in ground rail switching but that certainly isn't a requirement at all. NPN requires the base to be more positive than the Emitter to be turned on, PNP requires the base to be more negative to be turned on, so if you're driving with a squarewave or PWM your transistor choice determines the signal inversion factor. A 20% duty cycle pwm w/ NPN = an 80% duty cycle on PNP. Personally I prefer NPN for just about everything I can work it in to. They're easier to find and there are loads of alternatives.

Click to expand...

hmm I see ... that's why I said I am no expert :beer:
anyway I like the PNP more for switchin the positive rail

Thx for the response, yes I guess I started looking into pulse laser cannons and it seems they discharge a flash from cap bank into a rod? I also have found some 40 amp ~800+nm diodes that push 30 watts (continuously) they seem to be for things like radar and range finder components... That would probably satiate my wants as well.. I'd need like 8 32650's.. maybe 10 hmm..

So I have been follow this thread a bit to see where it may go. Some great ideas for creating a pulsed driver!

I, on the other hand, am not experienced in electronic schematics and creating what I want yet. I'll keep reading threads like this until I do though....and thanks to all that continue to contribute!:beer:

One of my favorite host/flashlights is the TrustFire TR-801. A nice little flashlight with a High, Low and Pulsed setting on the driver.

http://www.bestofferbuy.com/TrustFire-TR801-Cree-P4WC-3Mode-150Lumen-LED-Flashlight-118650-p-13309.html?currency=USD&utm_source=gbase&utm_medium=cse&utm_campaign=gbase_usa
(just a link so you can read a bit...not where I purchased mine....also Thanks to Mohrenbeg for the heatsinks!)

I did (a little) reading and found that it may just work for a 445 build.
With NO testing. A hope and a prayer. I hooked up the stock driver to a 445 that I had and tossed in a battery.

It's not the supper power house that most here may be interested in....NO 2 watts of pulsed power.

Some LPM readings. About 1 min. readings.

High Power...
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Low Power...
[/IMG]

Pulsed Power...
[/IMG]

The Host...
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And a video of the drivers High, Low and Pulsed. My camera does not pick up the faster pulse rate unfortunately.Quality not that great....sorry.


Perhaps this is useful to someone that just want's an easy hook up and go pulsed 445. Good luck and stay safe!