For starters, excuse my noobish questions and excuse my ignorance.
Found this tut, looks awesome, I have all the parts (for the most part) excuse the pun, but have a question in regards to the schematic. I need a laser driver that can output a constant current to the diode, according to the tut the best constant current is 1.25V. The recommendation is to utilize a LM317 with a resistor in order to output ~1.25V/R. Couldn't I just skip the LM317 and the resistor and stick in a buck converter to regulate the voltage? Like this guy:
http://www.amazon.com/DROK-DC-DC4-35Vto1-25-25V-Continuously-Adjustable-Continuous/dp/B00C9XXIHI/ref=sr_1_13?ie=UTF8&qid=1458125273&sr=8-13&keywords=buck+boost+converter
Also, anyone have any tips on creating a master-switch (on/off) that involves opening/closing a box? When the box is closed, the switch is on, when the box is open, the switch is off. I'd like to implement this so that when I do complete the laser engraver, the laser will only turn on if the box is closed, so you know, no one burns out their retina. Thank you in advance.
Additional schematic.
>>962658
>the best constant current is 1.25V
Current is measured in amperes. Your circuit is a constant current source like you said and you can't replace it with a 1.25V constant voltage supply. It uses 1.25V as an internal reference voltage for setting the output current.
Dunno about that buck converter. It might be suitable when used in constant current mode, or not.
A microswitch might be suitable for safety.
>>962663
Thanks for the microswitch tip. Also, thank you for the correction. I always confuse myself with amps and voltage.
Hey, I tried that exact circuit with a LM317 in a TO92 package and it didnt work at all, not getting 1.25V between the resistance leads and the current is not limited. I checked my wiring multiple times. Anybody know why (maybe it's because the TO92 package doesn't allow the power dissipation, idk) ? Thanks in advance.
>>962658
that.. so the pot is powered by three postives?
the pot has two pins bridged?
the resistors are in paralles why?
isnt the thrid pin a photo diode that is supose to be used in a regulator circuit to regulate and extend the life of the laser?
>>964847
1) you will not get 1.25V unless you're at literally below your current rating in terms of resistance (it will only go down to 1.25V if going up meant too much current)
2) This circuit is correct, but the most current you'd put out is 1.25/6 = 208mA. At that you're doing .24W through the resistors, which should be fine.
3) Laser diodes are notoriously breakable. Like even handling them can break them.
