Powering a Sanwu 650nm 250mW laser

[seb2010]

Hello everyone,

I just bought some more or less noname 250mW 650nm laser diodes (de.aliexpress.com/item/4000826011161.html). I removed the heatsink and at the back of the driver I can see the "SANWU" tag. The circuit-board in the shop-images does not match the one I can see with the heatsink removed.
Ultimately I am looking for the proper way to power and switch the diode with an arduino board. The laser then will fire atclover, identified by a camera and KI sitting on a hexapod robot, moving around in my lawn.

I am not realy sure, which components I need. At first I though, that I need a MOSFET to switch and regulate the current to the laser, because I did not trust the internal regulation in the bought diodes. But since I found quite some articles about Sanwu and their lasers here, maybe someone can tell me if I can rely on the internal regulation or not?
Either way, I then need to have a small ciruit to switch the laser on and off. At best with the possibilty to regulate the current somehow (two steps high/low would be sufficient), to first try it on a lower power level. The external power-source will be a USB-Charger-pack with 5V DC.
Although I have electrical background, I would like a simple circuit, as I do not have much experience or equipment for circuit boards and soldering and need to buy them explicitly for this project.

Looking forward to your help!
Cheers
SEB

 

[FireMyLaser]

That's a tall order. It's good that you explain all which you want, but you basically ask anyone here to make it all for you from scratch, and then you review it and say if easy enough for you to make. You should show a circuit that you designed and think is simple enough, and people here can give notes on what to change. As a start, I think using a mosfet to switch the power input of the laser driver is a good idea.

 

[seb2010]

Hi FireMyLaser,
ok, I did not think about it like that, but you are right. I thought there are some basic circuits that are always valid but "just" have to be parametrized a bit.
I'll give it a go:
- I understand, that MOSFETs do limit the current. They do not set the current to a constant output, correct? So as the Laserpointer itself has a regulation circuit, I only want and need to switch the power supply of the laser with a high enough maximum input current.
- as the specs of the laser are rather undetailed (SANWU gives a 0.5-1A current @ 3.7V, the seller of the laser-module itself gives <300mA current) I might need to measure the actual current without the switching circuit? I think so, right? So when I got the actual current, I can calculate the MOSFET to match that maximum current.
- when I then have the maximum current and I have my output voltage of the Arduino PIN to connect to the Gate of the MOSFET, I can calculate the voltage divider (R1 and R2) for the Gate-Source-voltage driven by the Arduino switching PIN. If i use a potentiometer in devider, I can fine tune the target current level.
- Then I connect the 5V Suplly to the laser-diode, the laser diode-out to Drain and connect the Source of the MOSFET both to the 5V-supply GND and the Arduino switching PIN GND to have them on the same voltage-level.

                    --------------------
----------         |                    |
|          |       O <-Laser (???mA)    |
|         R1       |                    |
|          |      /|D                   |                  
|          |----G| |                    |
|          |      \|S                   |
U_switch   |       |                    5V power supply
5V       R2_pot    |                    |
|          |       |                    |
|          |       |                    |
|          |       |                    |
----------------------------------------

So i basically need a MOSFET with the right specs and a resistor and a potentiometer for the Gate-Source calibration. Is this understanding right? Or do I need filtering or something in any case?

Cheers
SEB

 

[FireMyLaser]

The lasers you linked to already have a current regulating driver. You'd use the mosfet as an electronic power switch controlled by the arduino to turn the later on and off. You can find lots of examples on how to use a mosfet for this purpose.

 

[seb2010]

Thank you for the confirmation. I was not realy sure.