Buck Step Down current too low - help

Hi ,
I have recently bought an IR high power laser (see here http://www.ebay.ie/itm/261007928485...X:IT&_trksid=p3984.m1497.l2649#ht_3122wt_1186). I also bought what I think is an adequate driver for this laser (see here http://www.ebay.ie/itm/251110376844?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649).

So my problem.........I connected a 15V DC 2A power supply to the input of the buck, I adjusted the pots until I got 2V output and 1A output (short circuit) on my multimeter. I connected the IR laser diode and notice that it is not very hot; so I check the current going through it....it reads 0.3A..........so what is happening?

Do I need to use a different power source? Is my voltage too close to the dropout voltage?

Please suggest some solutions....I am at the final stages of building a CNC.

Where to start...

1. You need the laser diode to be in a module.
2. You need that module to be in a heat sink.
3. You need a focusing lens
4. 1W of 808 is not enough power for CNC work to begin with.
5. That is a constant voltage. You NEED a constant current driver.
6. Your diode might now be dead.

Have you done NO research for your project?

Thanks for the reply....I guess I left out some details that I thought you wouldn't need.....

1. You need the laser diode to be in a module. (It is in one)
2. You need that module to be in a heat sink. (It is in one)
3. You need a focusing lens (yes I have that too - glass)
4. 1W of 808 is not enough power for CNC work to begin with. (I am only trying to scorch the wood, not trying to cut anything, also I can go to 1.5W with this diode)
5. That is a constant voltage. You NEED a constant current driver. (Infact it is both a constant voltage and constant current limiter)
6. Your diode might now be dead. (was still working last I checked)

Anyway, I think I have discovered the problem and have a solution......Again I would appreciate your comments.

So, I think the buck converter is unable to deliver a large current at low voltages and this is why I see the drop in current. So the solution then would be to put a few diode (0.7V) in series with the diode thereby allowing me to output a greater voltage (say 2V + 0.7 + 0.7 + 0.7 + 0.7 + 0.7 = 5.5V) whilst only delivering the recommended 2V to the diode)
Your views?

Oops, didn't read the whole auction. I'm not sure I would trust those with a laser diode, but since this diode isn't enough power anyway, might as well try. Follow these steps:

Remove all loads from the driver.
Set the current to zero (all the way counter clockwise I presume?)
Give it a small turn above zero - quarter turn perhaps.
put a voltmeter on the output.
Set the voltage to somewhere around 2.5V.
Remove power from the device.
Short the output to discharge the output filter cap.
Connect the laser diode in series with a multimeter. Be sure there is no chance the electrical contacts will slip, because this will probably pop things.
Apply power to the device while monitoring output current. Turn the current up to an appropriate value.
Test it on wood for yourself and see it is rather poor for your application.

Um, also, you cannot check current levels on smps's by short circuiting the output. That is almost guarentee'd to break the power supply from overcurrent. I'd check and make sure that your supply is still working.

If you want to test the output current you need a proper test load.

Hi Folks, thanks for the replies. I will be getting some diodes and resistors tomorrow and will let you know how I get on (for anyone else that is interested).

One thing that is funny is that the instructions for setting the current states that I should measure in short circuit mode......which I have done and it doesnt seem to be broken yet.......I agree "Le Quack" that I really should have a test load when setting.....will do this and let you know

Well, I tried what Cyparagon said in his last post........the laser did lase and the current did vary from almost zero but only to 0.3 A (not the 3A as specified)...

I am wondering if I misread the "specs" for the constant current driver. It did say 3A output; but it did also say something that I did not understand....i.e. the revolving light current is 3 x 0.1 = 0.3A.......I have never heard of this before... but it does correspond to the max current that I have achieved.

Anyone understand this revolving light current (see link in my first post)

For those that might still read this thread.....quite a time later (5-6 weeks) I tried upping the voltage from 2.1V to 2.4V and hey presto! I was able to increase the current to 1W. I assume that the 2.1V was too close to the cut off voltage specified (2V).......will post more when I get around to it. Thanks everyone for the help so far