Pulsed driver ideas

GooeyGus · Jun 19, 2008

In the last installment of "driver ideas", the great minds of this forum came up with a pretty easy to use boost driver. This time, I was wondering about making a pulsing driver. It can be based on a simple LM317 current regulator, I'm just not sure how to go about pulsing the output. Can a 555 timer be used for this? I'm not even sure on which frequency to use. Something with an adjustable frequency from slow (strobe-like) to fast (not visible with the eye, unless one uses large sweeping motions) would be VERY cool.

Ideas?

lamborgini8 · Jun 19, 2008

It's a good idea, it does of corse open up the possibility of running diodes at 300mW or such without worrying about burning it out.

woop · Jun 19, 2008

I would use a microcontroller and a FET. simply because its easier
but if analogue is your thing...
if you use a 555 also have a schmitt trigger to drive the fet, because you want to drive it with a square wave, not whatever comes out of a 555...
just hook up the fet between the driver and the battery.

search the net for 'adjustable frequency strobe 555' or something

diachi · Jun 19, 2008

I can draw you up the pulsing circuit if you want, and you can build it then attach it to a LM317 driver, You'll need to wait till I get home though.

Diachi

diachi · Jun 19, 2008

heres that pulsing circuit, it should work, if you use a small resistor with a low resistance and capacitor thats small 200uF or less, it should pulse fastest.

Diachi

Sorry about the quality and CCD burns

Kenom · Jun 19, 2008

Dude, this has actually been tried and isn't that far back in this very section. We had about 3-4 people building individual pulsed drivers with 555 timers. I'll see if I can find it.

http://www.laserpointerforums.com/forums/YaBB.pl?num=1187540489/0

Maelstrom · Jun 19, 2008

DOnt know much about capaciters, only had a day or two on it in my physics class, but could you build a pulsed unit by using a capacitor? The charge would build up, be released, pulse the laser, and another would be building at the same time...

diachi · Jun 19, 2008

If you use that pulsing circuit I drew up and connect it to an LM317driver that will work, just need the right components at the right votlages .

Diachi

toked323 · Jun 19, 2008

As woop said it would be best to use a micro controller because its easier, you can program it to how many pulses per second. i think 30 pulses per second would be good enough?

woop · Jun 20, 2008

you could look into the picaxe, it is programmable in basic. it even has a PWM command. (its like a basic stamp but all in one chip, and cheaper)
you could have 2 pots connected to its ADC ports to control the freq and on/off times

otherwise here is a circuit for adjustable frequency
http://www.tkk.fi/Misc/Electronics/circuits/strobocontrol.html
I made it last night. it seems to work from >1Hz to above 20kHz by adjusting the resistor (I hooked up a speaker, it went above my hearing range)
to simplify that circuit, get rid of the Vreg and run it off a 9V battery, the output circuitry is not really required, just put a resistor in series with the base of a power transistor, that can switch your LD + driver on and off

GooeyGus · Jun 20, 2008

awesome! good work, guys.

So, details on this microcontroller setup?

woop · Jun 20, 2008

ah screw it just use the 555 in that circuit i linked to. its simple, and it does what you want.

here is some good info on setting up a 555 and how to play around with duty cycle and freq
http://www.kpsec.freeuk.com/555timer.htm#astable
its always fun playing around with analogue circuits anyway. who knows you might learn something

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