1:16 AM
@OYPS I know you are using an external power supply, but I think you missed the point. I would suggest you to read Components 100's short article on 1W LEDs one more time, and then read all the rest references. One more thing is important is the user requirement and functional spec of the UV power LED lamp. Let me casually and randomly scribble something.
Suppose I want to DIY a UV LED lamp for my cat's home. My preliminary cat's requirement and functional spec is summarized below: (1) 350nm, (2) 300mW, (3) 200mA, (4) 15 min daily, (5) 12V Vcc, ...
As told by Components 101, if you use the amateurish one transistor, one current limiting resistor approach, if the voltage across the LED varies by 0.1V, current would vary drastically, perhaps from 200mA by 50% to 400mA (for exact numbers, see my I-V test results), so it is UV overdose problem, which might shorten my cat's life. Or you are using UV kill germs, viruses, or make green fruit to ripe faster, then over UV exposure might make the fruit ripen too soon, ...
2 hours later…
3:29 AM
1 hour later…
4:46 AM
LED Constant Current Source - ElectroSchematics
https://www.electroschematics.com/led-constant-current/
https://www.electroschematics.com/led-constant-current/
The tutorial uses digital control. But we can use PWM control. To make things as loosely coupled as possible for prototyping and troubleshooting/testing/calbration, we can use PWM high/low side switching complimented by with low/high side CCS, also MAX4172 current sense amplifier, and UV sensor for feedback.
5 hours later…
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