Trouble with homemade DDL

Hey guys. I have made a DDL, i'll attach the picture further down.

The problem I am having is, for starters, the lasers are either very weak, or don't work at all.

The laser I purchased: LASER

I know I have the circuit done correctly because I had to etch 4 times to get it right. Sometimes i'm too impatient.

I hooked up 4 diodes and a 1 Ohm resistor. The voltage accross the resistor was good (260mv with 5Ohms, 370mv with 3.33 ohms)

The first sign of trouble is that the reference voltage (between Vout and Vadj) is 0...

The second, well, the lasers are all burning up. Note that I am running the diodes for less than a second. Just lightly tapping the positive terminal with the appropriate wire.

The circuit lights up a regular LED... albeit with a LOT of heat...






I forgot to mention that I AM shorting the pins where the potentiometer should go...

matthew798 said:

The second, well, the lasers are all burning up. Note that I am running the diodes for less than a second. Just lightly tapping the positive terminal with the appropriate wire.

Click to expand...

That setup looks OK, and should give you 380mA or so.

However, this line here is a worry. Which wire are you tapping? Because if you're leaving the driver powered and tapping the wire to the diode, the capacitor will be charging up and dumping a high current pulse into your diodes, a sure fire way of killing them.

well shiite...

I'm tapping the positive output of the circuit to the positive terminal on the LD...

What you say makes sense. I hope that's not the case.

At 250mA, my LD is hardly bright enough to illuminate the floor 1 foot below.

Is that a sign that my LD is kaput?

Sure sounds like it

Also make sure that your input voltage to the driver is at least 1.5V over the Vf of the diode, which for a red diode is around 3.2V or so. So powering the driver with at least 5V.

im powering it at 7.2V. Basically, I followed this guide

Then yeah, it should be fine. Sounds like the capacitor has popped your diode

I've never hated such a small object so much...

You're not a true laser hobbyist unless you've killed at least a few diodes

I've probably killed at least 30 of them in the time I've been in this hobby, from IR, red, violet and blue diodes.

It's alright i feel better now. I took out my frustration on the last remaining DVD burner in my apartment building and the LD works like a charm.

Would you happen to have any tips on removing an LD from an ugly metal housing? It seems glued in...

Got any pics? The usual method is to try and snap the heatsink off it, they're usually made from a metal soft enough to break off with some pliers.

For the harder metals, one way is to clamp the heatsink in a vice, and very carefully saw a little slit in one side, then you can use pliers to try and snap it where you made the cut. Just be careful you don't get any metal filings in the diode/on it's window.

Make sure you have a module to put the diode in once you've removed it, as it'll overheat quickly without one.

I got it. Nicked the sides but no biggie.

I have to wait now (remember what I said about me being impatient) for my aixiz housing. This is all going to become a laser paint remover controlled by an arduino to make etching a more automated process.

If I may add,

Make sure your diode isn't connected with some alligator clips or through breadboards.

MAKE SURE it's soldered on. The connection has to be permanent, otherwise even nanoseconds of open circuit will result in capacitor building up enough charge to kill your diode - which happens upon reconnection, aka after those few nanoseconds.

Also, traces on your board look way too close for comfort - in future, make sure you leave bit of space between traces or pins.

If you're using the standard sharpie method, one cool trick is to grab a sharp-ish metallic object like a key, screwdriver, knife, whatever, and run it between the critical connections. Just scratch the copper real hard, or the sharpie's trace if needed. It'll make sure the acid eats away that part bit faster than others, so by the time your board is done you should have some comfortable clearance between traces.

This way, even a tiny leftover strand from cutting wires or some metal shavings (abundance of both are found in working environments like worktables ) is going to cause you even more headaches.