Low Power Usage?

[pullbangdead]

So you mean, all i need for a pointer is a Microboost or Flexdrive, and i desolder its original pot, and replace it with a 25-turn one; plus a resistor in series, for setting current to max? (in the fridge, as winter)

Honestly, I would say to try it with an LM317 driver first. LM317 chip, resistor, pot, and a 9V battery is enough to mock it up and see what happens. If you have a diode and can try this, you can at least see what kind of output power you get. If it looks good with this <$5 arrangement, then you can look into getting a microboost or other and setting the current properly on it.

Yeah, you're right... it's the driver, but at those low powers I have noticed (on my 90-200mA driver) you can't get the full diode powered and the output doesn't look very multimode.. weird stuff. The weakest beam is probably 100mW I can manage without sputtering on the high power module. still plenty hot enough to smoke dark coloured materials.
driver consumes a lot of current and seems like it's fighting the diode for current.

I am replacing this driver with a Die4lasers 445nm addition driver.

That makes perfect sense, one mode will "turn on" before the others. Several other users have reported the diode being single-mode at low powers, and then more modes "turning on" as the current/power is increased. So that makes sense to me, at least.

 

[Xer0]

Does anyone know a multiturn-pOT small enough to fit in a AAA host?

 

[BShanahan14rulz]

Plus, many electronic kits use the 555 timer as a motor speed control. And they're good soldering practice. Comes with a circuit board, parts, and sometimes instructions lol.

FK804 DC Motor Speed Control
I used this one (though I don't remember if I actually bought it from Bakatronics) in a project of mine to send a PWM signal to my voltage regulator for my interior car lights. IIRC, I took the signal from pin 3 on the 555 and put it to the on/off pin of my voltage regulator (nifty feature)

As it comes, the PWM is at a pretty low frequency, and duty cycle has some limits (20%-99% or something like that), so be forewarned that you will see flickering if you use this to control your driver.

 

[LSRFAQ]

:wtf:

How did we get from PWM is a bad idea, thread closed, to lets speculate how to do this???

Or do we have two different threads?


Guys, I've been working with lasers as a hobby since 1986 and professionally since 1992. In lab and show environments. I've taken mini-courses in audience scanning laser safety. I was responsible for laser safety for a major university laser lab.

I make my living with lasers.

When I say PWM is NO improvement in eye safety for a fixed beam, I MEAN PWM is no improvement in safety for a fixed beam.

100 mW of "ON" power is 100 mW. The eye focuses it down, by a factor of 100,000.

So if you have the slightest malfunction of the driver or the PWM, you have a major issue on your hands.

And a 555 is about the worst PWM modulator possible, They skip cycles and exhibit jitter like crazy.

Your talking microsecond or sub microsecond pulses. Not the norm for the slow 555.

And none of you has yet mentioned how to make the safety circuits failsafe.

There is a reason why European jurisdictions require scanfail on audience scanning systems, and why the US spec is less then 200 nanoseconds to detect a fail. That 200 nanosecond spec is why there are only a handful of legal audience illumination systems, using lasers, in the US.

The only way to go about this with minimal resources is the ND filter, and reduced power while greatly expanding the beam. Glass ND filters, properly chosen for thickness and dopant, with the adsorption distributed along the thickness, do NOT bleach at these powers. The medical devices use chromium coated filters rated for the power and certain glasses like the BG series. They have things like multiple interlocked filters, and extra shutters on entirely different controllers, with individual power supplies on the safety.

The most complete treatment of this, on line and free, is here:

http://www.army.mil/usapa/med/DR_pubs/dr_a/pdf/tbmed524.pdf


Its power density per unit area entering the eye that you are concerned with, not just overall power. Big difference!


Steve

 

[ossumguywill]

LSRFAQ-that's another reason I wasn't in support of the 555 timer... to slow and unstable... but keep in mind these will NOT be audience scanning, just pointing.

 

[BShanahan14rulz]

Just for the record, I agree that 100mW is 100mW, whether it is only for a nanosecond or 10 minutes. PWM will make the beam appear to dim, though. APPEAR being the key word.

 

[ossumguywill]

If you have a 1 watt beam PWMing at a few dozen khz, it's probably no different to the eye thermally than a CW beam of the apparent power level.... and I'm pretty sure that's what matters.

 

[Xer0]

darn. is manages to get my 445 in a pointer and down to a reasonable looking current. but the threshold movement by temperature is bigger than i thought. i set it in room temperature... power rises exorbitant when outside in the cold, and falls noticeably in a warmer room.

So... back to the PWM thing?
Whats the lowest overall stable, effective power level? 100, 200mW?
Pulses at ~10kHz PWM shouldn't be really that problem, since i read somewhere, eye damage begins at 25mW/1ms...?

 

[leftkidney]

I think someone should make a better driver for the lasers - a digitally controlled one that used the 3rd pin on the diodes that is never used and use it for what I think it can be used for - that is to read the current draw and adjust accordingly

isnt the 3rd pin a feedback loop or whatever is used on IR doides to pulse them? - couldnt that be used to determine the output of the laser and make adjustments for temp so it would stay a low MW all the time

 

[Cyparagon]

These 445nm diodes do not have a photodiode as far as I know. It wouldn't matter anyway because threshold is rather high.