Switching 2 LEDs with only 1 controller output

147

02:35:27

The left side simulates a microcontroller output. Sometimes there is only one controller pin left, but you need two pins for e. g. two LEDs. In this case you can use this trick. You can switch the output pin between high (+3.3V), low (0V) and tristate (high impedance). Now you can switch on the red or the green light. If you change between high and low quite fast, you can even switch both LEDs on. And now a question for our experts: Why don't the LEDs light, if the right switch is open (tristate)? 

published 12 years ago

faceblast

12 years ago

because your microcontroller output pin just burnt out

Secuture

12 years ago

Because a banana skin runs out and LEDs are on come down ?? Or just ninja LEDs ( they try not to catch attention shhhhhh!!!!)

eljaf

8 years ago

They do, it's just that they are not very bright. 3.3V < forward volt drop of 2 LEDs at required brightness. Increase source voltage and you will see what I mean.

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