# How can I turn off an LED in parallel without affecting the other LEDs?

#### aschneider19

Joined Oct 7, 2019
3
If I have multiple LEDs in parallel and individual LEDs can be turned on/off, how can I make it so I can turn one LED off without affecting the current going to the other LEDs?

#### ci139

Joined Jul 11, 2016
1,666
you turn off the led by disconnecting it's anode or cathode from the supply rail resulting the disconnection point having the "opposite" to it's "ON" - state polarity ← that very fact can be utilized for control of the total supplied power - - tough the more led's you got the higher the precision requirement goes -- -- as well as the more immediate response you need the more demanding the design will be

you could use digital control for such by sensing the no. of LED-s ON:OFF or an analog one by summing the mentioned sense point voltages using some "op amp transfer function" (yet to be defined ...)

#### crutschow

Joined Mar 14, 2008
25,242
If I have multiple LEDs in parallel and individual LEDs can be turned on/off, how can I make it so I can turn one LED off without affecting the current going to the other LEDs?
LEDs in parallel depend upon close matching of their forward voltage drop so their currents are roughly equal
Don't offhand see how you can easily remove one without affecting the other LEDs' currents.
You would have to reduce the total current to the LED array by exactly the amount of current taken by the LED(s) removed.
The easiest way would probably be with micro control of both the switching and the LEDs' current total current, by having the micro controlling a constant-current source to the LEDs.

#### TeeKay6

Joined Apr 20, 2019
572
If I have multiple LEDs in parallel and individual LEDs can be turned on/off, how can I make it so I can turn one LED off without affecting the current going to the other LEDs?
@aschneider19
More detail (how many LEDs are in parallel? how is LED current limited? how will you disconnect/remove an LED? how many LEDs can be removed at one time? etc) might get you a better answer.

#### ci139

Joined Jul 11, 2016
1,666
if you have the "blocks of LED-s" to switch - the situation is worse because of the significantly higher current to redirect on block switch-off
in such case supplying each of the blocks with it's own current limit/regulation would likely be the better way to this