laser driver

Does anyone have a good plan for a driver for a 2W 445 laser running at 4.7vdc 2A

You could use it to make your own circuit boards (on a cnc type setup).

sorry did not word it very well fixed now I have all the movement controls and machine its going on just need a plan for a driver I cant find a decent TTL driver for it

2A constant current source circuit is what you need. And one that doesn't have any current over-shoot on switch on as laser diodes are easily popped. Typical constant current circuits are either linear, using opamp to drive a current-boost transistor, or a switched-mode constant current converter, which will be more efficient, although some might have unwanted over-shoot - one that's specifically designed for powering laser diodes (not just LEDs) is the thing to go for I think.

This guy seems to have it sussed. https://www.youtube.com/watch?v=DvD6nOvD4Fc

I have all the controllers sorted I just need a TTL laser controller that's going to do the job I haven't been able to find a decent circuit that can run a 2W 445 laser. I know I can buy one but I also can make one cheaper if I can find a decent circuit if it was a .5W laser that wouldn't be a problem there are plenty of circuit that size with TTL control that are good

OK I'm not really a hardware man but I've just knocked up something that may be worth messing around with. Don't hook it up to your laser until you've tested it and finished any tweeking it may need.

BTW I don't think it would be too fussy about the voltage of the external power supply. 12v would probably still work but you'd have to change the value of the resistor in the voltage divider. Ideally you'll want to aim at 2v difference between the top rail and the wiper on the potentiometer for your full 2 watts. Moving the wiper towards the top rail will then reduce the current.

Thanks for that I have seen ones like that before the problem I have is there is no spike protection or reverse voltage protection on circuit like that.

I have played with low power laser before I kept blowing them up because of spikes in the control wires until I put in protection to stop it happening. they where only a couple of dollars each so it did not matter to much.

with these higher power laser they cost a lot so I don't wont to run the risk of them being easy to blow up if I blow one up I have to import them as buying one in NZ cost 10 times what it cost to get one from over seas.

so if I cant make something that will work with protection in it I will have to buy a driver, the bits to make one don't cost to much here its when you buy a complete circuit it cost an arm and a leg.

the cost reason is why I am building one as I all ready have a machine I don't use that's worth to much to get ride off so i need to do something with it.

Fair enough and thanks for the thanks :) I hope you find something that's not going to break the bank.

so do I thanks for the help

Hmm... i'd get Arduino to control the current via pwm and a transistor, a 1watt sense resistor rather than source the exact value components a 1watt 1ohm should give enough resolution to control the laser's output.

cjdelphi: Hmm... i'd get Arduino to control the current via pwm and a transistor, a 1watt sense resistor rather than source the exact value components a 1watt 1ohm should give enough resolution to control the laser's output.

I'm not sure how the pwm would sit with the timing of this being used in a cnc type situation. If you're tracking it across a plane, just firing it once for each pixel of an image, as an where required, would pwm still deal with that?

I am using an Leonardo to do all the control of the laser it gets its info from a cnc program that control the amount of laser power required and when to fire the laser it can be controlled ether by TTL or a analogue signal. Its just a decent laser circuit what is required now that has decent reverse power and spike protection. I can make one for a 500mw laser there are a lot out there its just I have not found one for a 2W 445 laser that has all the protection what I require. I probably will do a deep search to find what I require you cant do deep search to often as that's the dark net

Have you got the schematics for the 500mw driver. Surely it con just be modified to take into account the higher current.

KenF:

5Vis too low an input voltage for a 4.7V output. 1 ohm is way too high a shunt resistor, it will lose 2V and 4W.

Its easier to drive a low-side current sink using NPN, since more opamps will drive near the -ve supply than the +ve supply rail. The NPN will need heatsinking. Supply voltage of 6V might be enough, 7V would be more reliable.

there is a almost driect replacement chip for the 500mw laser driver but it does not have RF protection and it uses a lot more parts to get the required currant. I am just playing it safe