Switching bicolor led using DPDT

[GREEN FUZ]

I`ve been mulling this over for a while, wondering what is the best way to do it. Using a DPDT to switch between the normal and notch settings of a Superfuzz while simultaneously changing the colour of a bicolour led. The 3PDT switches between led off or led on, as per usual.

Does this look right? Any reason why it wouldn`t work?

[GREEN FUZ]

Damn!!! I`ve just spotted my own (deliberate) mistake. Back to the drawing board.

If anyone knows how this can be done, please pipe up.

Looking at it again it might be alright.

[jakehop]

I did something like that in a Roland AP-5 Phase Five. I used bi-colored leds, as they were always on to show the rate of the LFO. A low-green showed it in bypass, a stronger red showed that the effect was engaged, as well as the rate of said LFO.

In your case, you can suffice using one resistor to the DPDT. Only problem I can see, is that one pole with two throws might not be enough to change settings - but I don't know the effect in question.

Hope this helps. Kind regards, Jake

[GREEN FUZ]

As each side of the LED has differing forward voltages the seperate resistors are to compensate for the variance in brightness. That said, the difference is probably negligible so I`ll probably follow your suggestion and just use one resistor. I`m just using one side of the DPDT to change settings and the other to switch the LED so hopefully it will work.

One way to found out.

[Andi]

I've done it in the past just switching which LED gets the ground, then the main footswitch controls the 9v feed. I found the brightness comparable with the same resistor for both. Hope that helps.

[Al Heeley]

I'm trying to do exactly this but with a two - pin Bicolor LED, wired to a dpdt mini switch so i can get it to display the status of the switch. Is it possible with a 2-pin bicolor LED?

[Al Heeley]

Aha! Just found this on AMZ Musique website:



Here is a way to use a 2-pin bicolor LED in a guitar stompbox. The 3PDT footswitch will pull one end of the LED alternately high or low and cause it to change color.

When the switch is connected to the top poles, the current flows from the 9v of the switch through the upper LED (green) and through the lower 10k resistor to ground. When the switch is toggled so that the center lug is connected to ground, the current flows from the upper 10k resistor through the bottom LED (red) to the switch and ground. Stomping the switch will alternate the LED between red and green.

If you want the red and green to change which switch position activates them, just rotate the LED 180° in the circuit putting the flat side to the right.

[ashcat_lt]

Mr Heeley, you sure do get around.

[Al Heeley]

Heh! A familiar name from another place. 

[ashcat_lt]

Yeah, I was actually wondering if anybody around here could answer the question I asked on that other forum, since nobody over there commented:

Would it be possible to use an existing 4.5V V_ref for this, rather than creating a whole new voltage divider?

[slacker]

You can't just use an existing Vref because the LED will mess with the voltage. When the LED is connected to ground by the switch it will pull the divider voltage down to what ever the forward voltage of the LED is, when it's connected to +9 it will pull the voltage up. It would probably work if you put a resistor between the LED and the divider, but you still might pull more current than the divider can provide which again will mess with the Vref voltage. Probably a risk of pops as well caused by sudden changes in current.

[ashcat_lt]

Thanks slacker.