SenKat's GB LD now an LED :(

Hi Guys,

I think I've just turned SenKat's GB Laser Diode into an LED. Could someone please review my 'steps' and let me know where I've gone wrong? I'll start from the beginning.

Yesterday, I hooked up SenKat's GB LD to DDL's PSU and it produced a bright red beam but was not powerful enough to burn things. I figured it could be caused by the mA being too low.

Today, I unsoldered the LD from the output of the PSU. I then measured the voltage across the output leads and it read 2.9V. I soldered a 1ohm resistor across the leads and measured the voltage across the 1ohm resistor and it showed 290millivolts which translates to 290mA in our case. So I've now got an output of 2.9V @ 290mA

I then unsoldered that 1 ohm resistor, turned the PSU off and shorted the output pins to drain any power left in the output capacitor. Next I re-soldered the LD back but this time with a 1 ohm resistor in series, so it's like this:

PSU(-)-------(1 Ohm Resistor)-----(SenKat's GB Laser Diode)-----PSU(+)

Now I turned it back on and the LD just glowed a very dim red light. I now measured the voltage across the 1 ohm resistor and it reads only 7 millivolts. I think the LD is now shorting coz it's burned??

I'd like to know where my mistakes were before I purchase my next LD. Also, how can I confirm that the current LD is really toast?

Thanks.

Best Regards,

cyclonite.

Ooooohhhh guys here's an update:

I think the LD's still alive because as I cranked the voltage pot up earlier it lit up a bright red again, anyway this is as far as I dare touch it before hearing anything else from you experts out there. Would really appreciate your thoughts on this.

Cheers.

Cyclonite,

It seems the the added resistor is taking some of the voltage, so if you turn the voltage pot up a tad bit you should be able to get the LD to work again, although, I would turn that current pot down a bit...

As it is right now, you can measure the voltage across the load (resistor + LD) and that should give you an idea what the driver is putting out. Also, measuring the voltage across the LD by itself will let you know if the LD is getting enough voltage or not. Measuring the voltage across the resistor allows you to know the current going to the LD.

All can be measured without desoldering anything, and without possibly killing your diode

GL;
DDL

Hey guys,

I've got it working!!!! wohooo.... I'll post more tmr.. It's very late now... lol

Thanks!!!! sorry for drawing all your attention here because of my stupidity...

cyclonite.

Yeah DDL, apparently the best way would be this:

1) turn the current port down to 10%

2) keep increasing the voltage pot while monitoring the voltage across the LD. There will come a point where turning the pot up won't push the voltage higher

3) When that point is reached, increase the current pot by about 5% and then go back to step 2 and repeat... this time the voltage can be increased slightly higher.

Keep looping steps 2 and 3 until the desired voltage and current is reached.

Phew that took a long time and I'm very tired now.... off to bed guys.

Cheers.

I still don't know why anyone thinks they need to control the voltage and the current - the current regulator does control the voltage.
Or is this not the LM317 circuit?

Zarniwoop said:

I still don't know why anyone thinks they need to control the voltage and the current - the current regulator does control the voltage.
Or is this not the LM317 circuit?

Click to expand...

I believe this is the premade PSU Daedal was selling...it regulates voltage and current.

Typically, I only care about current. With a V/A controled supply, you cat set the absolute max voltage to prevent runaway in an OOPS condition.

Mike

In my case, one could never set the output voltage to the intended (2.8V) as it always hit a 'ceiling' unless the current pot was turned up as well.