Using an SPDT to change a Bi-colour LED

Sibob · Post by **Sibob** » 16 Dec 2013, 20:27

Hi guys,

I've just put this together and it works great:

However, I thought it would be great to have a Bi-colour LED so that I know when it's in feedback mode as opposed to just true bypass mode.
How do I go about wiring that up?

, I've got the LED ready to go, and it works just on and off, but I can't get my brain into gear to get it to change colour via the SPDT?

Thanks
Si

Nocentelli · Post by **Nocentelli** » 17 Dec 2013, 09:59

You'll need to use a DPDT instead of the SPDT. One pole will do the feedback/normal, the other the LED colour.

Use the left hand column of lugs to do the feedback/normal switching as per your attached picture, and use the right-hand column to switch the LED colour: Connect the centre (common) lug to your current-limiting resistor, and then on to +9v, connect the red anode to the upper lug (red for feedback) the green anode to the lower lug (green for normal bypass). The LED should have a common single ground connection, which you should connect to the on/off (bypass) footswitch via the top right lug where the original single LED cathode was previously connected:

: Bicolour LED switch.PNG (2.23 KiB) Viewed 2304 times

Sibob · Post by **Sibob** » 17 Dec 2013, 10:21

You're a star thanks. I actually did one of those *wake up the morning after and realise the issue*, so ordered some DPDT's this morning

But thanks for the diagram too, massive help

Cheers
Si

Nocentelli · Post by **Nocentelli** » 17 Dec 2013, 12:44

No problem, I often start to post questions then realise the answer as I'm typing. Maybe putting it down in words helps analyse the problem. Two further bits of advice - The 10k resistor specified may be too big and the LEDs too dim - you can go as low as 2k with no issues to brighten it up. Also, if the red seems too bright, and the green too dim (or vice versa) you can use separate resistors tailored for the ideal brightness: Omit the 10k, and connect the separate resistors between the outer lugs and the respective LED posisitve (shown entering the flat of the LED on that diagram).

Sibob · Post by **Sibob** » 17 Dec 2013, 15:36

Yes I've already got a 2.2k in there, which I seem to have settled on for all my standard brightness LEDs.
Currently the LED is Red & Yellow, they seem about equal in brightness, but we'll see

Cheers for all your help
Si

Sibob · Post by **Sibob** » 20 Dec 2013, 00:55

So my switches arrived, but having wiring it exactly as above, I've got no LED at all, let alone switching from one colour to another.
I've re-checked the LED in a test circuit and it's fine, but wired as above....nothing

. Can't think what I'm doing wrong?!

Si