Low-powered DT0811 for a prop (noob-alert)

I'm sure that the general advice regards setting mAs would be to build a, "Test-Load". These kits are available from some members and there are threads describing how to use them.

Personally, I would happily use a 100ohm pot. As it's maximum resistance is higher, it will give more protection but less accuracy when setting current. If it were MY diode, (and I didn't have the luxury of a Test-Load, as with my first Blu-Ray!), I'd just carefully turn my pot until your LD is just lasing nicely. Bit risky but not unreasonably so.

That is where my advice ends at this moment I'm afraid. I'm not an electronics genius like some of the veterans here but if it gets you through, before wiser posts...

Good luck. Would be nice to see some pics of the finished prop when you're done?

M

Icetigris said:

I ended up being able to cut the PCB remnants off with an x-acto knife, though the old solder is still there. Does it need to be desoldered?

Click to expand...

If the "doughnuts" around the pins, from the circuit board. Also called pads, if the pads are still there they could move when you solder the wires to the pins. Causing a short. You might leave them there. But inspect it with magnification after you add the wires to the diode pins to be sure all is well.

Icetigris said:

. How many mA should I give to the diode to get it around 5-10mW?

Click to expand...

You can use the 100 pot. But all your adjustment will be in 25% on one end. That video shows a LM317 set as a current limiter. With a resistor and a pot in series to set current. What they call a DDL driver on this forum. Named for a respected user named Deadel or something like that. You need a 15 ohm resistor(radio shack), to go with your 100 ohm pot. That gives you a range of about 10 mA, up to about 85mA. The 15 ohm resistor limits the upper current. I don't know what current you need for 5-10 mW. But I guess maybe 30-45mA. But the 85mA is said to be safe.

So do this, power the laser and turn it so that the laser is off. You may see a faint violet glow even at 10mA. Slowly turn it up. The dim violet glow will suddenly jump in power. This is where the purple LED becomes a Laser. You can turn the pot back and forth across this point to be sure. Its easy to see the jump in power. When you know you have a laser, you will be around 3-5mW. Just make it 2-3 times brighter for 5-10mW. But remember, with the 100 ohm pot 70-80 % on the pot will be in the dim LED area. And the Laser area will be only 20-30% of the adjustment. Giving maybe 2-50mW. Remember that this circuit needs 9-12 volts for a violet diode. The rectifier diode protects the laser diode from reverse current. I don't even use it. The capacitor can be just about whatever you have, from 4.7 to 47 seems good to me. I have even left it off a few times. But I question my wisdom on that one.

Morgan said:

Would be nice to see some pics of the finished prop when you're done?

Click to expand...

Definitely

--John

So I soldered wires onto my diode today. I built the circuit on a breadboard too. I haven't tested it with the diode yet, but I went to the EE lab and tested the driver itself and it looks like it works. I made sure to short the capacitor before anything else. I'll see if I can test the whole thing later today, but have a picture of my shitty soldering job anyway.

I put a piece of electrical tape around the negative lead because I was afraid the leads might touch.

EDIT: I put a piece around the positive lead too because I'm paranoid.

And don't worry, I'll be posting pictures of the finished product

GREAT SUCCESS

You stuck to it and prevailed. Great job. +1