Help with wiring a diode to a dpdt switch...

[perro5151]

Hello everybody,

I'm working on another diy project,and I wanted to use a dpdt footswitch (on-on) to switch between two different resistor values. This is not the problem. The problem is that I want to wire an LED indicator to the one side so when I switch from 'normal' to 'other' I can indicate this transition with an LED. Alas, I am not well-versed enough to do such a thing on my own. Anyone have any idea how this could be done? I'd greatly appreciate the assistance!

Thanks!

[mysticwhiskey]

Hopefully this will do what you want:

DPDT_2LEDS.png

This uses one side of the DPDT to switch the either of the 2 LED's on. They share a common current-limiting resistor, whose nominal value is 4.7K but you can vary this depending on the brightness of the LED's you want.

[mysticwhiskey]

Oops, I think I misread your question - the previous diagram assumes you wanted 2 LED's, when I think you actually asked for 1 LED.

This should do what you want:

DPDT_1LED.png

You will need to check that the other side of the switch is wired such that the LED comes on in the proper position, or if it's wired opposite to how you want it to work you can just move the LED's anode to the other lug of the switch (the lower rightmost lug in the diagram above).

[perro5151]

Hmmm, maybe I'm just lacking in knowledge (which is usually the case here), but the only way I understood to do a basic parts switch with a dpdt was something like this...

Part A >>>>>>>>>>>>>>> * * < Part A
Original spot on board #1 >>> * * <Original spot on board #2
Part B >>>>>>>>>>>>>>> * * < Part B


I'm using a dpdt on-on footswitch (which was kind of difficult to come by) instead of a toggle. Sorry if I didn't explain well enough

[mysticwhiskey]

OK, so you're already using both sides of the DPDT switch - from your question it sounded like you had one side of the switch free to use.

To include LED indication as well as your part switching, you'll need to use a 3PDT switch. I don't think that a DPDT is suitable.

[mysticwhiskey]

Come to think of it, there is a way you can switch in another resistor with an indicator LED using a DPDT:

DPDT_ResistorSubstituteWithLED.png

In the diagram shown, the LED will light when the modified resistor is switched in (Rmod) - the LED doesn't light when the original resistor is selected (Roriginal).

[perro5151]

Hooray! Thank you so much! I'm just about to do the wiring, so I'll test this out. Thanks again!