ddl circuit resistor values

[nkgamer1990]

Hey so reffering to my first question, using this circuit, would it be safe to change the current while the circuit is powered?
-Nicholas

 

[Cyparagon]

Yes, if you use a pot with the wiper and one end shorted.

 

[Bionic-Badger]

Hey so referring to my first question, using this circuit, would it be safe to change the current while the circuit is powered?
-Nicholas

You can, but pots are mechanical devices and it might result in a momentary short/open circuit that could cause damage to your laser. Depending on the design of the pot, especially surface mount types which may not have a wiper stopper, it may switch from the highest resistance instantly to the lowest if you pass the end of the range. I always turn off the laser before adjusting and do a quick test of the resistance. It's also a good way to determine if you're at the top range of the output current you want to give to the laser, especially if you don't have a laser power meter to determine the output power.

For the wattage of your resistor/pot, remember that the voltage across the resistor/pot for regulating the current is only (and always) 1.2-1.25V, so if you need 1 amp of output power, a 2W resistor/pot will be sufficient. Download the LM317's datasheet and do the math yourself with Ohm's law to confirm; it's the best way.

 

[Cyparagon]

Or use this site.

 

[nkgamer1990]

the drivers max output would be 1.4 amps with a a130 diode as a load.
im not worried about it jumping to max current. it does have to be adjustable while in use.
-Nicholas