moesciphish
Newbie level 5
lm2575 constant current regulator
Hello all, I'm VERY green to electronics, but after reading some information on small circuits, I'm trying to design one that will power 20-30 3.6v 20ma LED's for around 9-12 hours. I'm orgininally was thinking about using 7.2v batteries with a LM137 circuit, something like:
**broken link removed**
However, since this requires about 3v of headroom, I'm a little worried about the battery voltage dropping during use. My main problem is that I ABSOLUTELY need the current (and voltage?) to stay constant in the LED's because it is a certain wavelength that it really needs to be at or extremely close to. So I guess I need something to regulate the voltage as it drops from the battery and keep it at a constant voltage and then use resistors to keep the LED's at a constant current? Again, this is my first electronics project and first time I've ever dealt with anything electrical, so please excuse my ignorance, but any help would be GREATLY appreciated.
Thanks![/img]
Hello all, I'm VERY green to electronics, but after reading some information on small circuits, I'm trying to design one that will power 20-30 3.6v 20ma LED's for around 9-12 hours. I'm orgininally was thinking about using 7.2v batteries with a LM137 circuit, something like:
**broken link removed**
However, since this requires about 3v of headroom, I'm a little worried about the battery voltage dropping during use. My main problem is that I ABSOLUTELY need the current (and voltage?) to stay constant in the LED's because it is a certain wavelength that it really needs to be at or extremely close to. So I guess I need something to regulate the voltage as it drops from the battery and keep it at a constant voltage and then use resistors to keep the LED's at a constant current? Again, this is my first electronics project and first time I've ever dealt with anything electrical, so please excuse my ignorance, but any help would be GREATLY appreciated.
Thanks![/img]