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ArcticMyst Security by Avery

ddl circuit resistor values

Joined
Apr 23, 2009
Messages
463
Points
28
Hey so reffering to my first question, using this circuit, would it be safe to change the current while the circuit is powered?
-Nicholas
 





Joined
Oct 26, 2007
Messages
5,438
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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.
 
Joined
Apr 23, 2009
Messages
463
Points
28
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
 




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