awlego
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- Oct 9, 2009
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I have a LM317 based DDL driver set up with two 1/2 ohm resistors in parallel to set the current to 500mA. Problem is, no matter what resistor(s) I use, the output is always ~160-170mA. Even if I take off all resistors it still outputs at 168mA... which is really weird. I have double and triple checked that I set the circuit up right, including checking the resistors for the correct resistance with my DMM and making sure I have the LM317 pinout correct.
Any ideas what's going on? My only guess is that my LM317 chip is not working correctly and I need a new one, but if anyone has experienced this or has insight into what might be going on, I would love the information.
In case this helps:
Using a test load of 3 1N400X diodes with a 1 ohm resistor.
Powered using 4 AA alkaline batteries. (4x1.5v = 6 v in) (lm317 takes 2.25 + .7 for the reverse polarity protection diode which leaves plenty for the 1.82 forward voltage my the diode.)
Ultimately going to drive a 100mW green module.
Any ideas what's going on? My only guess is that my LM317 chip is not working correctly and I need a new one, but if anyone has experienced this or has insight into what might be going on, I would love the information.
In case this helps:
Using a test load of 3 1N400X diodes with a 1 ohm resistor.
Powered using 4 AA alkaline batteries. (4x1.5v = 6 v in) (lm317 takes 2.25 + .7 for the reverse polarity protection diode which leaves plenty for the 1.82 forward voltage my the diode.)
Ultimately going to drive a 100mW green module.