Main > Main Forum
LED control idea
cholin:
Okay, what I plan on doing as of now is to use Trimoor's second circuit.
NoOne=NBA=:
--- Quote from: cholin on February 17, 2005, 05:51:41 pm ---well can't the wires all connect to one diode and then go to the switch?
--- End quote ---
No.
The diodes are there to prevent ALL of the LED's from lighting up when a single button is pressed.
They basically keep all the "connected together" wires from "seeing" each other.
Without those diodes, ALL the LED's would see the connection to ground through the one pressed button, and light up accordingly.
Trimoor:
Adding a global dimmer is very easy. Connect the 5V source to a potentiometer before any of the circuits, and it will control everything.
Using the calculator that LSDiodes links to, the 12,000mcd LEDs equate to 68Ω resistors. If using the dimmer, you want the resistors to be set at the highest brightness when fully illuminated.
Calculator
forward voltage=voltage drop
cholin:
How do you get 68 OHMs? I used 5v as supply, 4 volts as forward, and 20mA as current. It said to use a 50 ohm resistor. I picked 4 volts because it said that's the maximum for the 12,000 mcd white 5mm LED. This way if I use a pot, then the highest will be the maximum which is what you said.
Trimoor:
I used 3.8 "typical" forward voltage. 12Ω won't make much of a difference. Use 50 or 68, whichever is convinient.