The Cozy has a manual landing light that drops out from the belly of the aircraft. The bulb had blown, so I started looking at LED alternatives. They’re more energy-efficient, and much, much brighter.

AeroLEDs has created an interesting light, the Sunspot 36 Equinox.

The AeroLEDs Sunspot 36 Equinox LED light

Source: aeroleds.com

If you push 12v through it one way, it illuminates the taxi light (more spread, less distance). Push 12v the other way, and it illuminates the landing light (less spread, more distance).

The question is… how to wire this?

Using an On-Off-On DPDT switch is pretty easy:

On-Off-On wiring diagram showing how to reverse polarity

Source: VogMan

However, that puts the off position in the centre, unlike all the other switches where off is down. I’d prefer to have Off be in the down position, then have the middle position be for taxying, and the top position for take-off/landing. I couldn’t think of a way to get a DPDT switch to do this, though.

The other change I wanted to make was to have the light automatically deploy when switched on, and retract when switched off.

After more head-scratching than there should have been, I worked out a way to use a 4PDT On-On-On switch to do both these things.

Honeywell TL-Series Switch Circuitry

Source: Honeywell

Proposed wiring diagram for a progressive AeroLEDs Equinox light, Off-On-On, with reversing polarity