Can someone help me with running two LEDs in a pedal?

B

bigcountry

New member
I have a design on an enclosure that would look really awesome if when the pedal is engaged two LEDs came on simultaneously. I’m assuming it’s possible, just curious how I would go about figuring out if I need to put a resistor in line, how to calculate the resistance needed, etc. I’m relatively new to pedal building, any help would be appreciated. Thank you.
 
the "best" answer is to breadboard it. 2 LEDs can share a single current limiting resistor. In terms of the resistance amount that depends if you've got the superbrights or not. Start with 1k and work your way up from there. Don't be surprised if using superbrights that the resistance goes up to 20k+.

If you don't have a breadboard you can always use alligator clips.
 
I also just found out the hard way, the two LEDs in parallel need to be the same color / have a similar forward voltage to work without adding a secondary branch resistor. I had a blue LED and red LED in parallel, red came on but the blue didn't. Red has a lower forward voltage (approx. 1.9V) than blue (approx. 3V). Someone else can probably explain better than me and/or there may be a good reference on this site, but the red's lower forward voltage is controlling in parallel at about 1.9V so the blue doesn't have enough voltage to turn on. For this case, there is a solution/calculation to put a resistor in series with the red LED's branch. In my case, I found that an orange LED has a similar forward voltage as red (by testing on my handy breadboard), and I just substituted that for the blue LED.
 
It's usually easiest just to give each LED it's own current limiting resistor.

Then you can adjust the resistance for each separately depending on color / brightness.
 
Instead of pedal-building websites...
If you go to the DIY electronics websites, you'll find more info on "how to and why" running LEDs in parallel vs in series.
 
gtfields13 said:
Y’know, I started messing with electronics in the 70’s and have burnt out more than a few LEDs, but earlier this fall I actually had LED explode when I unintentionally shorted the resistor. First time that’s ever happened to me…
Click to expand...
Oh wow, that’s gotta be a little bit exciting.🤣
 
When I use two status LEDs of the same type and color, I connect the anodes together, connect the cathodes together, then treat them as a single LED with a single CLR. Like others have said, I work out the value of the CLR by trial and error on a breadboard or with alligator clips. Occasionally, I also like to put a trimmer in series with the CLR to make the brightness adjustable for different situations or preferences. If you have trouble matching the brightness of two different color LEDs each with their own CLR, I might consider using a trimmer, each leg to a CLR and wiper to ground, for example.
 
moosapotamus said:
When I use two status LEDs of the same type and color, I connect the anodes together, connect the cathodes together, then treat them as a single LED with a single CLR. Like others have said, I work out the value of the CLR by trial and error on a breadboard or with alligator clips. Occasionally, I also like to put a trimmer in series with the CLR to make the brightness adjustable for different situations or preferences. If you have trouble matching the brightness of two different color LEDs each with their own CLR, I might consider using a trimmer, each leg to a CLR and wiper to ground, for example.
Click to expand...
I do the Annie’s and cathodes together as well. Particularly when giving your rat glowing eyes.
 
As others mentioned, giving each LED its own current limiting resistor is the cleanest approach. For the actual calculation: R = (Vsupply - Vf) / I

For a typical 9V pedal supply with a red LED (2V forward voltage) at 10mA, you'd need around 700Ω - so a 680Ω or 1k works great.

Here's an LED resistor calculator that makes it quick: https://www.schemalyzer.com/en/tools/led-resistor-calculator - just enter your supply voltage, LED color, and desired brightness. It also shows the nearest standard resistor values.
 
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