Hi, all. I am working on an effects loop pedal (of my own) and I want to add a foot switch that can shunt the input signal to ground. When it's on, though, I want to light up an LED. For maximum headroom in this circuit, I am supplying 24VDC, so I need to add resistors. Ohm's law tells me that I need a 11.1k resistor which seem hard to find, and very expensive when I find them. So, if I run a trace and inline it with a 3.6k resistor (which would be a good value if I ever want to make a smaller version and run it on 9VDC) and then run that trace, in parallel, to all of the switches, and then use a 7.5k resistor at each of the LEDs, should that work? With Ohm's law, what I am not sure about is the current with the other items on the board. It seems like, as long as the other things aren't draining the current so much that there isn't enough left for the LEDs, that it shouldn't matter, and that the values I plugged in are correct, but I just want to be sure.
Help with adding a foot switch and 1.8V 2mA LED to circuit, please
- Thread starter Steve973
- Start date
temol
Well-known member
You don't have to be so exact with led resistor values. 10-12k.
You can use a resistor and trimmer in series with resistor - you'll be able to adjust brightness/current depending on the supply voltage.
Resistor value here is not critical. Anywhere between 2k-4k7. Resistor sets min resistance value in the circuit - it's there to prevent damage to the LED if you set the trimmer to zero R (max clockwise).
You can use a resistor and trimmer in series with resistor - you'll be able to adjust brightness/current depending on the supply voltage.
Resistor value here is not critical. Anywhere between 2k-4k7. Resistor sets min resistance value in the circuit - it's there to prevent damage to the LED if you set the trimmer to zero R (max clockwise).
Thanks -- that is an awesome idea, and I did not even think of using a trimmer! Can you tell that I am new to this? I am curious about the minimum resistance value that you mentioned. Is a 4.7k resistor enough to protect a 1.8V 2mA LED from damage from 24V?
