Krupski:
Hi all,I recently did a small project that needed an LCD display with an LED backlight. I wanted to use a regulated current source so that the display wouldn't flicker with power supply voltage changes.
Here's what I came up with, and it worked nicely.....
The microcontroller circuit itself only used about 20 mA, so I just used a 22 ohm resistor for R and supplied the LCD backlight with a constant 230 millamps.
Nice thing is, the LCD backlight current stays constant whether the input power is 9 volts, 12 volts or whatever. Of course, suitable heat sinking for the 7805 may be necessary, and Vin has to be at least 7 to 8 volts.
Hope this helps someone......
Your drawing show you grounding the center pin of the 7805. I don't think that is the proper way to wire up a 7805 as a constant current source.
Lefty