My driver does not work??? WHY!!???

[jawsykilla]

Okay i purchased one of these laser diodes 808nm 300mW High Power Burning IR Laser Diode DIY Lab . I then created a basic TTL laser driver circuit using some veroboard, the required components and such. Now I tested the circuit with a few high power LEDs. It worked. I connected the laser diode. Nothing. Also i wasn't sure which pins were which on the diode and i didnt know how to test them. Any ideas?

 

[HIMNL9]

Okay i purchased one of these laser diodes 808nm 300mW High Power Burning IR Laser Diode DIY Lab . I then created a basic TTL laser driver circuit using some veroboard, the required components and such. Now I tested the circuit with a few high power LEDs. It worked. I connected the laser diode. Nothing. Also i wasn't sure which pins were which on the diode and i didnt know how to test them. Any ideas?

Uhm, first of all, the 808nm IR band is almost invisible, you will see only a very dim red light, also if the diode is emitting at full power (and being IR 300mW, it's dangerous for the eyes, if you look into it directly, so never do a similar thing)

One of the easiest ways for see if your IR diode is working, is looking through a webcam, or videocamera, cause they see the infrared light.

Second, you said you connected the diode, but you also said you don't know what are anode and cathode ..... this means you have 50% of possibility to have fried your diode, connecting it in reverse (anyway, basically all the IR diodes have case positive, so the pin connected to the case is the anode) ..... also, using the friendly function of the forum called "search" may have pointed you to this thread, that collect almost all the pinouts that we know about laser diodes

Also, there's so much drivers schematics and types, that we can have a better idea about what can be wrong with your driver, if you had posted some pics or schematics, you don't think ?

 

[jawsykilla]

Okay thanks for the swift reply. First off I'm not stupid enough to look directly into any powerful light source. I did use 3 different camera to see if the IR beam existed. I used a crappy webcam. A digital camera (photo). And an IR enabled video camera. Nothing appeared on any of them. I did indeed use the search function and visit the thread you linked me to. However there is no data for my diode on there. I contacted the seller of the diode also and they had no idea what I was talking about. So if the case pin is the anode. Then which is the cathode? This is the exact laser driver circuit I built. Linked to from this forum nonetheless Laser driver - It can be done I didn't post any pics because i destroyed my circuit in anger after wasting hours trying to troubleshoot it. But now I am going to build another circuit and buy a new diode. I just want to make a burning laser and yes I have safety goggles and understand basic physics and electronics. Do you need anymore info?
Cheers,
Jordan

 

[HIMNL9]

The pinout for the IR diodes (is somewhere, in the forum, anyway) is the same as the red ones, just reversed polarity, and is the same for the 99% of the models .....

take the diode and look at it from the leads side, having the middle one (the one electrically connected to the case) up, like this:

          anode (+)
             |
             o
           o   o
          /     \
cathode (-)     n.c.

The upper one, connected to the case, is the positive (anode), the one at your left is the negative (cathode), and the one at your right is sometimes not connected, and sometimes connected to an internal photodiode (this depend from the different models, to have or not a photodiode), but also if there's a photodiode, you don't need it, so this pin can be left unconnected or soldered directly with the central (anode) one, if you need to solder it on a PCB, for the stability.

 

[jawsykilla]

Okay thanks. Ive just found some extra data for my diode. Apparently it has a 2.2v operating voltage and since it has a power output of 300mW doesn't that mean that the circuit will only need to provide roughly 140mA of current? If so then I should only use one 10 ohm resistor? can you verify this for me. This may be why my diode refused to work last time. Too much current?
Cheers,
Jordan

 

[HIMNL9]

Uhm, too much current, usually, means a fried diode (also if i hope not) .....

Can be some "cold" soldering point, or some wrong resistor value .....

Try this circuit, if you want, it's a more safe alternative to that one.

Also, for a 300mW emission, as far as i remember, the operating currents was around 350 / 370 mA ..... at 140mA, it must still lase (usual threshold current for these models is around 100mA), but probably emits between 20 and 40 mW, not more .....

BTW, are you using any test load or dummy load, for set up the current of your driver, before connect it to the laser diode ?

 

[jawsykilla]

I did not use a test/dummy load when i tried it last time as I got too excited and couldn't wait for anymore 1n4001s in the post. So i trusted abilities and plugged it in lmao. Bad choice that was. I think i'm going to stick to the circuit I want to build because I have all of the components available in front of me. So did I supply too much current to my diode last time? Should the schematic for the Red Senkat laser work for my diode?
Cheers,
Jordan

 

[HIMNL9]

As far as it can give 350/400mA on the diode, it must work (only remember that red diodes have reverted polarity, compared with IR ones)

IF you are sure that none of the components was damaged from the previous tests, ofcourse

 

[jawsykilla]

Okay I've just created another circuit, this time I've connected up some LEDs just for now in series so I can see if the circuit works. I turned it on and for some reason twisting the potentiometer does not affect the brightness of the LEDs. Should it?
http://i247.photobucket.com/albums/gg127/Jawsykilla/DSC00042.jpg
Also I took a reading across the LEDs and got a potential difference of 6v? Any ideas?
Cheers,
Jordan

 

[Toke]

One obvious answer is that your power supply cannot deliver enough voltage for the diodes and that your driver is therefore delivering less current than it is set for.

You should try measure the diode drop of your test load before connecting it, if it is too close to your supply voltage the driver will not regulate.

Most multimeters have a diode setting, it will give you the minimum voltage of a diode. The voltage drop over an LED or LD will increase a bit with current.

Or just try with one LED less.

 

[jawsykilla]

Ok thanks Toke, I'll check that out. Thanks for the info
Cheers,
Jordan

 

[Cyparagon]

Apparently it has a 2.2v operating voltage and since it has a power output of 300mW doesn't that mean that the circuit will only need to provide roughly 140mA of current?

Unlike most light sources, lasers are rated on output power, not input power

 

[jawsykilla]

Okay thank you Cyparagon. I've just tested my driver with a dummy load of 4 1n4001 diodes and a 1ohm resistor. Now testing V across all three diodes gave me a pd of about 2.99 volts. Then testing mV across the resistor gave me about 34.5mV. Are these values within the correct range? also my potentiometer does nothing. Why is this? I'm sure i have it wired correctly.
Cheers,
Jordan

 

[Toke]

I'm sure i have it wired correctly.

I am not , but it is quite difficult to do fault finding without diagrams of pictures.

 

[dasraiser]

also my potentiometer does nothing. Why is this? I'm sure i have it wired correctly.
Cheers,
Jordan

hi, it looks like your pot is not connected correctly , it looks like from your pic the outer tracks are connected together, look at this pic

http://www.rog8811.com/1K to 100R.jpg

the wiper (center pin) should be connected to one outer leg and form one side of the pot and the other leg becomes the other side of the pot, think of it like this, current always tries to take the path of least resistance.

hope this helps

 

[jawsykilla]

Thanks dasraiser I can't believe I could overlook that so easily. I was in an excited rush when building the circuit however :crackup: anyways now my pot does work and alters the current greatly. The minimum reading i get across the 1 ohm resistor is 0.10mV which I am told in this Dummy Load it is equivalent to the current supplied so at least resistance i get about 150mA. Now, my laser diode specs say it operates at 2.2v. When I take a reading across the 4 1n4001s i get just over 3v and when i measure across 3 1n4001s i get 2.32v. Is this cause for concern?
Cheers,
Jordan