Working on first driver for red Sony diode

[gunak87]

Hi folks. I've been lurking for a the past few days trying to read and learn as much as I can, but I've still got a few questions. I have a decent understanding up how the driver supplies and regulated voltage and current. However, I don't know exactly how specifically I'm supposed to dial things in for my diode (Sony SLD1239JL from StoneTek). I've put my driver together based on Daedal's nice guide and I'm attempting to include a photo of it.

I'm feeding it 6V from four AA batteries. I can measure between 45mA and just over 250mA and about 5V with my mulitmeter. I've been testing it with an orange LED for a few hours and it hasn't blown (my orange LEDs usually fry with anything much more than 2V) so it's doing something right.

So my questions are:
1. Do I need to knock the voltage down from 5V to somewhere between 2.5-3V?
2. What amount does the current need to be?
3. Does my wiring look right? (assuming I get my photo attached correctly).

 

[rog8811]

So my questions are:
1. Do I need to knock the voltage down from 5V to somewhere between 2.5-3V?

The LM317 is set up as a constant current source, the voltage will take care of itself, the reason you are seeing strange voltages is that your LED is not a good comparison, load wise, to the LD you will be using.
http://www.laserpointerforums.com/forums/YaBB.pl?num=1197651171/0
Will show the best way to test.........

Question 2....not a clue, cannot remember but I tend to use 5 ohms to set the max.
Question 3....Testing the circuit as suggested in the first answer will tell you that.

Hope that helps.

Regards rog8811

 

[chido]

Also be sure to provide the circuit with more than 4 AAs, the circuit needs a minimum of 6v to work so if you provide it with that exact 6v as soon as the batteries start getting used up your regulator will start dropping out and it'll never send a constant current to your diode and it'll keep getting weaker and weaker.
It's even worse when you're using alkalines because their voltage always drops under a load, so when you connect the 4 AAs to your circuit, right from the start the regulator is going to start dropping out.
It would be better if you could get 6 rechargeable NIMH batteries or 2 rechargeable CR123 batteries. If you can't get one of those two than use 6 AA batteries.

You can get NIMH batteries here. (make sure you order 2 packs as each pack contains 4 batteries.)

But I would prefer the rechargeable CR123 batteries because they're cheaper and take up less space. (order only one pack since you only need two batteries.
And get yourself a charger.

 

[Hemlock_Mike]

Keep the applied LD junction voltage around 3 volts to begin with. Current is the measurement you need to watch. The voltage will be whatever the junction exhibits for your diode. Stay below 400 mA on that LD. Your readings are a little to understand along with the variations.
A colored LED is a bad load. Do you have a "bad" red laser diode to use?
Mike

 

[gunak87]

I found my diode that I burned out before I found these forums ( ) and hooked that up to the driver. It lights up, but it's really dim (because it's burned out, of course). It's seems to work as I expect. It's quite faint when my potentiometer's resistance is high, and brightens up when I turn the pot down.

As far as batteries, I'm going to get at least some NIMH rechargeable ones soon. I just need something cleared up. Is it safe to use alkaline batteries and just a nuisance that they poop out early? Or is it actually bad for the diode to use alkaline batteries? If it's safe, can I get by with a 9V battery for now instead of using like 6 AAs?

Thanks for all the good replies.

 

[chido]

There's nothing wrong with using alkalines, just use 6 AAs so your regulator doesn't start dropping out really soon.
You can't use a 9v battery because its mAh rating isn't high enought to drive the red diode for a long time.