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Steering wheel button upgrade - 14th Jan 13


Kit Car Electronics

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Thought I'd share the details of my latest unnecessary upgrade...

I decided to change to a carbon dash and ETB Digidash2. This meant new switches, so Savage aluminium ones went on the shopping list.

Then I thought a detachable wheel boss might be nice, but also wanted indicators and main beam switches on the wheel - but how to connect them? Curly lead? No thanks, why take the easy option when I could make it complicated...

This project will probably take me all winter, so hopefully it will work! If so, I'll write up for the club mag, but meanwhile I'll share it here first...

Here's what I've chosen to do:

1) build an Arduino Nano micro-controller based switch interface.

This will allow:

  • Single button for cycling through headlight/ sidelight/ off with MOSFET instead of relay control

  • Single button for cycling through wiper speed low/ high/ off with MOSFET speed control

  • Wireless communication with battery driven transmitter on steering wheel

  • Self cancelling indicator function

So far, I have the wireless part working perfectly in prototype form:

IMG_2168.jpg

Here are the three main bits - a 2.4Ghz Transceiver, Arduino Nano V3.0 clone and 2.4Ghz transmitter:

IMG_2167.jpg

The transmitter is actually a 5 button key fob with conductive switches, but I managed to solder wires on instead (not easy!) to support my steering wheel buttons. The beauty of this method is the tiny current draw - the micro-controller will sleep for a quoted 3 years on the 3V coin battery and just wakes up when a button is pressed, transmits a packet and then goes back to sleep - ideal! I should be able to re-pot in a small case that will hide on the back of a carbon panel attached to the steering wheel:

IMG_2165.jpg

Here's how I soldered the wires to the transmitter - first scratch away the opposite 'fingers' of the conductive switch and a clear ground area at the top:

IMG_2163.jpg

Then solder some CAT5 cable onto the pads (cheap source of wire for electronic projects) before covering with hot glue to protect (and hide the evidence of bad soldering!) :

IMG_2164.jpg

The completed transmitter squeezes snugly into a plastic box internal dim 53 x 28 x 21mm...

Wiring to the steering buttons is pretty straightforward as they share a common earth on one side (soldered at the top of the PCB), then each switch is attached to one of the soldered switch pad wires. I used 4 switches, but the fob supports 5 if necessary. It doesn't matter which pad connects to which button, as this is configured in the Arduino receiving software to match.

Completed steering wheel wiring:

IMG_2173_zps9d22b18a.jpg

More details for basic Nordic Fob/ Arduino communication are here

14/1/13 I found a really good looking version of the fob transmitter here. This version has 3 of the buttons broken out directly to through holes and the other 2 both have small via holes on the PCB that can be used with fine wire. I contacted Brennen at diyembedded.com for more info and got some really helpful replies, so if I make another, I'll definitely use this version instead.

12 Comments


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Dave Eastwood (Gadgetman) - Club Chairman

Posted

Excellent started looking at the Arduino boards after looking at Pi's. haven't got beyond the looking stage yet though, haven't had the time to get my head round what I need to do the outputs.

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Kit Car Electronics

Posted

Arduinos are great for this kind of stuff, there's loads of info on how to drive different outputs... I'm using mosfets instead of relays, but could use a transistor and relay instead. Very easy to drive LED switch lights directly, too

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Kit Car Electronics

Posted

Thanks filfan, prices look reasonable. I buy most stuff on eBay, some from Hong Kong, but most of the electronics come from China anyway...

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just wondering what tx you have used as im liking this and my wiring is now non existant so could do something similar

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Kit Car Electronics

Posted

A Nordic fob http://proto-pic.co.uk/nordic-fob/

I've nearly finished the wiring schematic for the switch controller- will upload later... Just decided to also include the hazard switch and do the whole flasher function with the mosfets :-)

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thanks for that i will get some stuff ordered and joun the wireless club.

 

just wondered though but could someone using the same tx confuse the system or are they paired together

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Kit Car Electronics

Posted

Excellent, i'll post some links! The frequency is set by software which I should be able to update through the serial interface on the fob- could also add a simple encryption if several others join the wireless club... Otherwise we can turn each others indicators on when parked nearby!

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That could be interesting. You could sound another cars horn while passing young ladies :)

  • Like 1
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Kit Car Electronics

Posted

or make them indicate to let you pass on a track day...

  • Like 1
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or make them indicate to let you pass on a track day...

 

Have to keep an eye on you sir!

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any idea of a suitable alternative to the nordic fob as they have been discontinued ?

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