LED driver based on LM317 gives more voltage than required? Answered
Hi, I tried to run a 1 watt led with the LM317 in constant current mode. Since the led required 350ma currrent, I used a 3.3+1 ohm resistor in series across the Vout and ADJ. So my resistor series was about 4.3 ohm which should deliver about 290ma current to the led.
The driver was based on https://www.instructables.com/id/Super-simple-high-power-LED-driver/
When powered up, the current across led was around 290ma but the voltage across the led was 4.33v whereas it should be between 3.0-3.6v according to the led datasheet.
What am I doing wrong? Is it safe to run the led at 4.33v ? It was getting hot.