Laser diode identification - Page 1
Forum section: electronics / repair

author: duzycinek
author_rank: Contributor
timestamp: March 15, 2023, 01:33:09 pm
content: Hello, I got problem with damaged laser diode. I want to replace but I am not sure what to buy. Good diode is working on 3V and current consumption is about 100mA. Also it has 7LBX B221 markings. It is 5.6mm version. It is part of Leica Lino L2 cross laser. (Red light, 635nm according to brochure of cross laser). Looking for model of diode. Thank you!

author: Swake
author_rank: Frequent Contributor
timestamp: March 15, 2023, 09:45:13 pm
content: Leica is not the brand it used to be. I'd say this is just a fairly generic laser diode. Search for "635nm laser diode" on ebay or ali.Make sure your have the same pins (do I see 3 pins in your pic?) and size (5.6mm).

author: duzycinek
author_rank: Contributor
timestamp: March 16, 2023, 06:11:23 am
content: Hello, thank yours response. How about output power?

author: james_s
author_rank: Super Contributor
timestamp: March 16, 2023, 06:59:33 am
content: It's almost certainly 5mW or less due to safety regulations. 100mA seems very high though, I would expect about half that. How did you measure the current?

author: duzycinek
author_rank: Contributor
timestamp: March 16, 2023, 08:22:34 am
content: I shorted on/off transistor and measured current. There is also control board at top of the diode, maybe it take part of current also. I will buy 5mW 3V diode. Thank you so much!

author: james_s
author_rank: Super Contributor
timestamp: March 16, 2023, 05:02:15 pm
content: You might be reading a much higher current than is present in normal operation, most modern low power laser pointers and such use nothing more than a resistor to limit the current to the diode. Any low power visible laser diode in a 5.6mm can ought to work for this.

author: duzycinek
author_rank: Contributor
timestamp: March 16, 2023, 05:15:44 pm
content: Thank youpurchased 5mW laser diodes.

author: Swake
author_rank: Frequent Contributor
timestamp: March 19, 2023, 11:29:15 am
content: There might be a yellow sticker on the device with the laser class on it. That is somewhat an indicator of the output power of the laser.

author: james_s
author_rank: Super Contributor
timestamp: March 19, 2023, 06:18:44 pm
content: The laser warning label will show the maximum power, but that often is much higher than the actual power produced.

author: Swake
author_rank: Frequent Contributor
timestamp: March 19, 2023, 09:55:02 pm
content: The idea is if the label tells max 1mW (=class2) then you know it is not anything bigger.

author: duzycinek
author_rank: Contributor
timestamp: March 23, 2023, 08:26:42 pm
content: Thank you, sticker says "2 class laser", so diode will be 1mW max?I can't find any diode with less than 5mW output power in this case (TO-18)

author: james_s
author_rank: Super Contributor
timestamp: March 23, 2023, 10:05:10 pm
content: So use a 5mW diode, you can reduce the current if you want lower output.

author: duzycinek
author_rank: Contributor
timestamp: April 21, 2023, 05:33:33 am
content: Hey, do you know how to modify this circuit (it is probably constant current source) to increase output current? I am facing problem with new laser diode. Old one is like 2 times brighter and I want to adjust new one. (New one is consuming about 35mA, old one about 100mA. Looking forward to hearing from you!

author: james_s
author_rank: Super Contributor
timestamp: April 21, 2023, 05:20:57 pm
content: Looks like it's using the photodiode for feedback. You could try replacing the driver with just a plain resistor like you'd do with an LED. Most modern laser diodes are a lot more robust than the earlier ones, they don't require closed loop control.