How to determine current if driver is unknown

Hello.

I have been reading a lot in here, but this is my first post I became quite addicted to lasers some while ago when i accidently bumped into C4R0s website and his amazing homemade laser projectors. I wanted to make my own project. I started out buying 3 pointers. A green 50mv, red 50mv and Bluray 100mv. Before I made a driver for them I just ran them off 3v rail from a modded atx psu using each pointers own driver. This worked perfectly until I accidently hooked them up to the 12v rail -Poof 3 dead lasers

I realized how inportant a decent driver is. I went ahead a bought a new green 100mv? And a couple of Aixiz modules, a couple of LPC-815 sleds and also some PHR sleds. The reason I write "green 100mv?" is that since it is of Chinese origin there is no way to be certain how much is IR and how much 532nm actually is emitted. The LPCs, PHRs and Aixiz modules I bought from Modwerx (thanks Drew for excellent service and fast shipping).

I knew the current for the LPC and PHR diodes, but since the green was from a pointer, I had no clue how much current it was setup for. I obviously had to find the exact current so I would'nt kill the LD once hooked to a proper diver.

The following pictures and text describe how I measured the exact current.

The LD + Driver can be seen below from frontside and backside.





Now it was time to remove the LD and prep the driver so it could be hooked up to the testload. The next few images show the driver having wires soldered to it to hook up to the PSU (or batteries).





Now it was time to hook it up to my testload. Below you can see a picture of it, im not going into further details about it, there are plenty of threads explaning all this.



The next picture show how the driver and testload are connected together with the PSU. I measured this driver to deliver a steady 320mA when being fed 3v from my modded atx psu.



After i found out the exact current I hooked it up to a 3-channel rgb(v) driver and everything worked as it should

Below is a picture of the laser(s) in action. I turned the green down a bit since I will be using it in a RGV setup and it was way to bright compared to the red and bluray.




I hope someone will find this info usefull when needed to determine current from an unknown driver / LP.


Best regards

You can also use a Variable bench PS as it will show the current draw of the driver.:yh:

Or for most greens and reds, simply put an ammeter in series with the battery.

HELLO and welcome to the LPF!
That's not half bad for a first post. You've obviously done your homework.:gj:

Cyparagon said:

Or for most greens and reds, simply put an ammeter in series with the battery.

Click to expand...

IIRC if the driver is a boost (boost/buck too?) it will draw more current than linear driver. It should get you pretty close though.

Greens(IR that is) and reds usually have a Vf of <3V , so they don't need boosted voltage.
Unlike 405 and 445.

I am just beginning on electronics as well so after reading a lot of threads in here this seemed like the safest way to do it. I wanted to measure it without the LD to keep it super safe and away from harm