Osram PL520 50mW 520nm Laser Diode

[Alaskan]

Thanks for all the info right here! I'm planning on using one of these diodes with one 4.2v 6000mAh Li-ion battery and a fixed current driver set at 220mA. Heat sinked diode of coarse. My question is; is that to much voltage? Should I just stick with one 3.7v?
Thanks for taking the time to help.

That particular diode/PL520 runs nicely at 8.0~8.1 all the way down to 7.0 VDC without a current regulator, believe it or not, but at 8.2~8.4 VDC it will dim and not come back until the voltage drops down to somewhere between 8.1 to 8.2 VDC. However, it must have a good heat sink if you are running it without a current regulator as it will put out about 100mw which is twice its rated output power. For best single mode TEM00 output, best to run it closer to its rated output power.

If you are going to use it with a constant current regulator, you need a boost driver for it to increase the voltage from a single 4.2 VDC battery to the voltage it needs. Here's a spec for the diode:

http://www.dpss.ro/datasheets/PL_520_2012-10-23.pdf

This is the only laser diode I know of which will run without a CC regulator, my diodes have not died from such abuse, but I cannot guarantee every PL520 will act the same. The specs say 7 to 8 VDC is the operating voltage at 200 ma for 50mw output, you can increase the current to get more power out but I am not sure how high you can increase it without shortening its expected operating life.

 

[Pikletreestem]

That particular diode/PL520 runs nicely at 8.0~8.1 all the way down to 7.0 VDC without a current regulator, believe it or not, but at 8.2~8.4 VDC it will dim and not come back until the voltage drops down to somewhere between 8.1 to 8.2 VDC. However, it must have a good heat sink if you are running it without a current regulator as it will put out about 100mw which is twice its rated output power. For best single mode TEM00 output, best to run it closer to its rated output power.

If you are going to use it with a constant current regulator, you need a boost driver for it to increase the voltage from a single 4.2 VDC battery to the voltage it needs. Here's a spec for the diode:

http://www.dpss.ro/datasheets/PL_520_2012-10-23.pdf

This is the only laser diode I know of which will run without a CC regulator, my diodes have not died from such abuse, but I cannot guarantee every PL520 will act the same. The specs say 7 to 8 VDC is the operating voltage at 200 ma for 50mw output, you can increase the current to get more power out but I am not sure how high you can increase it without shortening its expected operating life.

Thanks for the help! I think I've got the set up I want to use figured out;

1 PL520 50mw diode (from DTR).
1 Fixed current diode driver set @ 220mA (from Survival Laser).
2 16340 3.7v Li-ion batteries in succession.
1 BAMF'n stainless steel host w/ extended copper heat sink. (Survival Laser)

I think that should do it! But if I'm missing something, please let me know.

 

[Alaskan]

I think you would be better off with a single 3.7 to 4.2 VDC (4.2 when fully charged) battery and using a boost constant current driver, problem is when the batteries drain down, with the voltage drop of a non-boost driver with two batteries, you might run out of enough voltage to power the laser to a full 50mw output too early or before your batteries are really drained. It really depends on how much voltage drop that driver causes, find out how much.

 

[Pikletreestem]

I think you would be better off with a single 3.7 to 4.2 VDC (4.2 when fully charged) battery and using a boost constant current driver, problem is when the batteries drain down, with the voltage drop of a non-boost driver with two batteries, you might run out of enough voltage to power the laser to a full 50mw output too early or before your batteries are really drained. It really depends on how much voltage drop that driver causes, find out how much.

I've purchased this driver from Gary at Survival Laser. He says these drivers have a 92percent efficiency. I believe it should work well. Unfortunately I don't have a LPM to do a proper test:yabbem:
Thanks for all your help.

 

[DTR]

View attachment 47691

I've purchased this driver from Gary at Survival Laser. He says these drivers have a 92percent efficiency. I believe it should work well. Unfortunately I don't have a LPM to do a proper test:yabbem:
Thanks for all your help.

Yea it is not the efficiency rate of the driver but that these diodes have a near 7V forward and say it has a 1V dropout which is very common then that is a minimum of 8V you need to drive the laser diode. Two Li-ions in series are 8.4V and you always get some sag from any battery under load which means it will start dropping power near immediately and may even just go dim with the batteries still 2/3rds charged. Some drivers have a 1.5V droput which would mean fully charged you may be half power and just dim out quickly. It may be really a great regulator and have only a 0.5V dropout but you will still be 1/2 to 2/3rds fully charged when the diode fades. Unless you go with a three Li-ion in series configuration a buck or linear are just not good options for the PL520. A boost on the other hand is a perfect fit.