DIY Homemade laser diode driver

I´m pretty shure. i checked the resistance and it went fron 0.3 to 98.7 OHM.

Name :
MIN POTENTIOMETER CA6 V 100R LIN, 0,1W

i think i got it some how i slightly rased the input voltage by 0.5 V and gota result of 100mv+ i think my batteries are a bit worn out.

I remember seeing a post that said a 10 ohm resistor works great for the PHR, so does that mean that I replace the pot and the resistor with a single 10 ohm resistor? Also for the PHR diode, what batteries should I use for it to have the right output voltage?

This driver is really confusing...

Thanks - Brian

A PHR diode requires about 5.5V to operate. The voltage drop of this driver is about 2.5V

? - 2.5V = 5.5V

? = 8V (approx.)

You can use a 9V battery, but for more lifetime I suggest using two 3.7V LiIon batteries from a website like DX (they offer a combined 8.4V fully charged). They offer them in many formats (labelled by a series of numbers: width in mm, length in mm and then a 0).

exemple:

10440 = 10mm X 44mm = AAA.

It's a format I recommend and that I use often.

I apologize if this has been requested already, or if I missed it, but...

I'd like to make a request for photos of completed DDL's, for those of us who are newer to circuits and soldering. I'd love to see photos of both sides of a completed driver, so I can get an idea of whether I'm doing things right or not. I believe I'd learn better by seeing completed drivers, and seeing a finished working product.

Thank you.

Give me a day, And I'll modify this post with some pictures of a simple one I made... If it helps.

-Tyler

Although there's a lot of wires and the picture's not very clear, the two PCBs here are DDL drivers (one for the LD, one for the TEC)

You can see I've got some big copper heatsinks, the square yellow things with a gray dot in the middle are potentiometers . I'll upload some new pictures with more detail soon.

Hello people. Hope someone tells me what's wrong with my setup. I made this diode driver explained on the first page of this topic. I used LM317T, one 100 ohm multi-turn potentiometer, 47uF 16V capacitor, 4x1 ohm resistors in series and one 1n4002 diode (they didn't have 1n4001 but the only difference is that 1 is 100V max and 2 is 200V max). Also I built a dummy load with 6 1n4002 and a 1 ohm resistor and connections for red and blue diode. I made some tests and I want to know if this is right or I did something wrong on the way. The power comes from 4XAAA alkaline batteries.

At 2.95V input I have an output of 2.28V for the diode and with dummy load i go at max 0.4mA for red diode test and 0 on bluray diode test.
At 4.46V input I have 4.00V and dummy load 13mA for red and 1mA for blu
At 5.93V input I have 5.45V and dummy load 157mA for red and 15mA for blu

I thought that this driver was going to give 2.5-3V for maximum 16V input. Also I tested on 10V input and the output was 8.8V or something.
Did I do something wrong on the way? The measures for the current were taken on the sides of the 1ohm resistor and I transformed from mV in mA. That resistor might be 1.1 because I tested it with a multimeter but still...10% error. I tested some dvd player diodes at 5.93 input and they lit up ok, without heatsink for about 5 minutes. I think current was set for about 60mA. So they got about 5.45V? Shouldn't them have burnt out? The diodes weren't even warm and lit up pretty good. I clearly triple checked the voltage at diode connector before connecting them. Got them from some broken dvd players and thought they are expandable for testing purposes
I've attached a picture of my driver with the dummy load built on the same test board.

Did you measure the voltages with the load attached? It looks like the diver can't get enough current through before it hits it's votlage limit. 6x a 1n4002 probably have about 3.6v drop. With 5.45v output, the 1ohm resistor of the test load takes 1.85v, whoch is 1.85 amps for a 1 ohm. Clearly not correct. So one of the numbers here isn't right.

Measure the voltage drop over the diodes. Measure the load resistor to see if it really is 1 ohm. Make sure you measure the output voltage with a load attached.
what do you mean with "157mA for red and 15mA for blu"? you already attached diodes?

Bluefan said:

Did you measure the voltages with the load attached? It looks like the diver can't get enough current through before it hits it's votlage limit. 6x a 1n4002 probably have about 3.6v drop. With 5.45v output, the 1ohm resistor of the test load takes 1.85v, whoch is 1.85 amps for a 1 ohm. Clearly not correct. So one of the numbers here isn't right.

Measure the voltage drop over the diodes. Measure the load resistor to see if it really is 1 ohm. Make sure you measure the output voltage with a load attached.
what do you mean with "157mA for red and 15mA for blu"? you already attached diodes?

Click to expand...

I measured the voltage without the load attached. As I measure a source output before attaching anything to it, I did the same with the laser diode connectors.
I didn't attach any diodes, only dummy load that was set up for emulating a bluray or red diode. That's how I got those numbers. Right now I'm at home and cannot do any more measuring I left the board at work. Tomorrow i'll post the voltage drop over diodes and also I'll measure the output voltage with the dummy load attached. I was thinking...could any of the parts be damaged from the soldering heat? I used a 30W soldering iron. I was a little clumsy at the beginning since I didn't solder for 10 years or more

You're working with a current source here, the voltage just varies as long as the right current is given. Just like a current varies on a voltage source.

So, without any load, the driver will raise the voltage in order to make it's set current run, but it hit's its maximum. With a load, the load conducts the current and pulls the voltage down, as the regulator only needs to give a few volts before it comfortly sits at it's set current without the need to raise the voltage.

Did you use the same pinout as indicated on the schematic? If you did, then you got it wrong. Try a search at Datasheet catalog for integrated circuits, diodes, triacs, and other semiconductors, view for the pinout. Else, make sure you got nothing crossed and that you are not inverting any polarities. You can also try without a dummy load, just plug in the leads with your DDM set at 200mA.

Since the LM317 is in current regulation mode, it is NOT regulating voltage correct? So I couldn't feed a red diode 12v because it would receive something like (12 - 3 - .7) = 8.3 correct?

I made new measurements. This time I decided to "feed" the whole circuit from a disassembled stand-alone dvd player power source. I found a 10V channel
Ok, so: 10V input, about 9V to the diode connectors of the driver without the dummy load, but that's not interesting since I have to measure with the load attached. When I connect the dummy load the 10V channel drops to 8.10V (measured at the connectors for power of the driver). I think the power source is kinda retarded :thinking:
Anyways ... 8.10V input, and about 3.50V at diode connectors of the driver WITH the dummy load connected (dummy load set for red diode emulation - using 4x1n4002). I got about 306mV on the resistor with the DMM. I also measured the resistor and it's 1.1ohm. That would be about 278mA top with the pot set to max. I also connected the dummy load set for blu-ray emulation (6x1n4002) and I got the following: 10V line measured before connecting the driver with dummy load attached (8.13V after), and at diode connectors of the driver WITH blu-ray dummy load attached I got 5.04V and a total of 0.306V at the resistor, that would be the same 278mA max with pot at max since the resistor is 1.1ohm. I have to say that the lm317 got pretty hot, I could barely keep my fingers on it but not more than that. Are these measures correct for the board described at the beginning of this topic? Do blu-ray diodes require around 5V for normal operation? I would really like to know if what I built is reliable for future more expensive diodes to test since right now I'm playing with harvested ones from old dvd-players and such...
Thank you for your time :beer:

Ya, BR diodes use around 4.8V.

And for the LM317, you should use a heatsink, one IC model I used recently had a built-in over-heat shutdown so I had to give it a big heatsink.

Just a note:

I´m pretty shure. i checked the resistance and it went fron 0.3 to 98.7 OHM.

Name :
MIN POTENTIOMETER CA6 V 100R LIN, 0,1W

Click to expand...

Good, you burned your pot...