BlueRay successful failure read FYI

I recently purchased a $36 (w/shipping) BlueRay PS3 400A lens assembly from PSXBOY.COM
just barely got it mounted it in a Aixiz module and had it running smooth... but
another one is on it's way because I burned this one out by switching my DMM meter OFF while reading the current, which disconnected the laser diode from the driver circuit I had built, and then I mistakingly switched the DMM back ON, which caused a voltage spike from the CAPacitor, burning the diode.  Then I burned the rest of the diode out for fun ha. The red and IR aren't that powerful anyways and I have plenty of them. it was a good learning experience but I sure hope I don't f#&*K that shit up again because 407nm is COOL
but anyways below is a picture of my setup when it was operational, you can see 57.9 mA (ignore the negative sign) going into the diode, and I am running the popular DDR circuit mentioned here in the forums off a 9v battery partially diminished to ~8v.

I would like to know a couple of things if you have the time & knowledge to answer them:

Why use a voltage regulator (the 317 component)?  does it really matter what voltage the diode is connected to, as long as it's not enough to arc?  is 9v going to be dimmer than 10v at the same current in a blueray? someone told me the diode draws the voltage it requires, so if I connect a bunch of batteries in series, is that going to work, or is that putting too much current into the circuit?
Is a heat sink necessary for the blueray?

how exactly does a KTP crystal work, what does it do entirely?  where can I get one or two?

does the output current from the photodiode in the blueray have a linear (direct) relationship with the optical output of the violet diode?   is this an easy way to see if the diode is losing brightness?

Thanks and happy harvesting

The 317 is set up to regulate the current, not the voltage.
KTP crystals are in green lasers, not Blu-rays, not sure where youd find them for sale other than in green lasers. And not sure on the last question. I love my Blu-rays color, once you see it you get hooked ;D

The 317 does regulate current if it's set up right. BTW it's 405nm
Also, you are right in that the voltage essentially does not matter. This is because of the nature of the diode and the driver. You set the current and the voltage will sort itself out.

A KTP crystal doubles the frequency of laser light (halves the wavelength number). It would be no use to you, as they are only reasonably efficient at doubling 1064nm light (to 532nm green) and furthermore need to be aligned mindbogglingly precisely to do anything.
As far as I know the photodiode should have a fairly linear relationship of output mW to millivolt drop / millivolts it produces.

ah yes 405 nm

another q

say i set the driver pot to a fixed resistance, and then I feed the driver with more voltage while maintaining a fixed maximum current capacity from my voltage source, ie, more batteries in series? is the diode going to see that voltage and get brighter or is it all based on the fixed current still?

how do I eliminate the risk of a voltage spike in the circuit? another cap?

thanks for the info

dang that thing looks powerful, did you use a long exposure to get that beautiful beam shot?

36$ was that INC. the diode :-?

mdw26 said:

say i set the driver pot to a fixed resistance, and then I feed the driver with more voltage while maintaining a fixed maximum current capacity from my voltage source, ie, more batteries in series?  is the diode going to see that voltage and get brighter or is it all based on the fixed current still?

Click to expand...

The LM317 will keep the current constant as long as you give it enough voltage. You can give it more voltage, up to 37V, and the current through the LD will still be the same, but the regulator will heat up more, since it has to discard more power as heat.

So yes, you can give the circuit more batteries. It is best to give it enough batteries, so that their voltage is still above or equal to the minimum required, when they are empty. This way, you have a constant power over the entire battery voltage range, as they discharge..


Oh, and it does matter what voltage you connect a load to. The current through it is directly proportional to the voltage. (I=U/R ... R is LD's internal resistance)..

The LM317 regulates the current by constantly adjusting the voltage in a way, that current stays the same, even if the resistance decreases from heat.

With Blue Rays, this difference is small and unimportant, but with powerfull burners, as they heat up, their resistance drops, and if they are powered by a constant voltage source, the current increases, which can kill them. A current regulator would drop the voltage a little in this case, and the current would remain constant.

how do I eliminate the risk of a voltage spike in the circuit?  another cap?

Click to expand...

A tantalum directly on the LD is the best solution for this. Your LD died, because you had the capacitor on the circuit output, instead of LD, and when it got disconnected, the LM317 tried to keep the current constant, but there was no load, so it increased the voltage to the maximum and only charged the capacitor.

If your cap was on the LD, this wouldn't happen. It is recommended to keep the LD soldered to the circuit at all times.

You don't need to put the multimeter between the circuit and the LD to measure the current. Since this is a linear regulator, you can just as well measure the current between the battery and the circuit, and it will be the same current as the one going through the LD.

Alternativelly, you could solder a 1 Ohm 1% resistor between the circuit and the LD and just measure the voltage drop across it. On a 1 Ohm resistor, voltage drop across it in mV is the same as the current through it in mA. This can be more exact than putting the meter in between, and is also a lot safer.

Due to the voltage drop, the regulator will have to put out a little more voltage, but with a blue ray, this would only be around 40mV, if the current is 40mA. Otherwise, it doesn't change the preformance in any way.

Oh, and your current was rather high. 57mA is a lot for a blue ray.



BTW: You may find, that your BR is not completelly dead yet. It's very possible, that it only lost most of it's brightness, but it's treshold current got way higher..

With two of mine, the treshold current went above 150mA after ESD. But they still lase, and are the brightest at 220mA. Unfortunatelly, they are nowhere close to the original brightness and they get extremelly hot.