It has always been a bugbear of mine that the audio (and cruise control) switches on the steering wheel don't light up on the 75/ZT, as you have to remember which is which when driving at night, this gets even more haphazard when the steering wheel is turned upside down.
So I decided to do something about it and I have redesigned the switch PCBs to incorporate surface-mounted LEDs.
However, there is a major stumbling block on cars with cruise control, this being that the squib (clockspring, or slip ring as sometimes known) doesn't have any spare pins on it, meaning there is no easy way to get the supply to the LEDs in to the steering wheel without tying yourself in knots. So I came to the conclusion that the only way to achieve this is to convert the analogue signal from the switches to a digital signal (serial data), send it through the clock spring, and then convert it back to the original analogue signal for the rest of the car to understand as per normal.
This means I can compress the four analogue wires down to two, freeing up one for a +5v supply to an encoder housed within the steering wheel, and one for the all important illumination supply wire to the LEDs, which works with the dimmer on the light switch pack so the brightness can be adjusted.
This 'digital' version also has the added benefit of dealing with the issue of an incorrect operation occurring when using the audio controls, as they rely on a resistance network which can become confused as the switches age/wear and the contacts become tarnished altering the resistance seen by your headunit. You may have noticed TRK+ occuring when you actually pressed VOL+ etc - somewhat anoying when you go to turn up your favourite track!
Further to this and for a bit of fun I thought I'd add a BMW-style gesture sensor, so you can control the headunit by making simple gestures in front of a sensor, this is demonstrated in my own car in the video below. (Note the prototype PCB in the vent is green in colour, any production one would be black to blend in).
Swipe left for Track-, right for Track+, swipe up will turn the volume up three notches, swipe down will turn it down three notches.
As I've gone to all this trouble, I wondered if this would be something which other owners are interested in as a possible group buy?
I assembled this one myself by hand, but I simply wouldn't have the time to sit and fit all these tiny surface-mounted components on mass, so would have to arrange to have a batch of PCBs made up professionally by machine,
so if there are enough of you interested please let me know by replying so I can judge the numbers and see if it is viable.
I'm guessing here as without even a vague idea of numbers pricing is just a guess, obviously the more there are the cheaper it would be, but I suspect a single switch PCB and required wiring loom for cars without cruise would be around £30-£40, up to around £130-£140 for a full two switch PCB, encoder, decoder and gesture sensor kit, as it involves 6 PCBs for a full kit, including two microprocessors, ambient light sensor device and several connectors and wiring looms which need to be made up by hand, unfortunately I am restricted in which connectors I can use as they obviously have to plug in to the ones already in our cars.
Also, I am only on this forum, so if any of you are members on other ones for our cars please let them know on there too, as I can only see this being done in one go.
Please note: My headunit is an aftermarket one with a steering wheel control learning function, but the signal put out by my decoder is the standard signal that you would get from the original switches, so it works with an original headunit (that had hard-wired steering wheel controls - not infra-red ones) or off-the-shelf steering wheel control adaptor for aftermarket headunits (Pioneer, Alpine, Kenwood etc etc). The decoder simply plugs inline with the original wiring on the steering column.