Steering Wheel Audio Controls

[Matt.]

Since installing my Autome sat nav head unit, all of my steering wheel controls remained working except the Prev/Next buttons. These buttons do still work... the head unit just can't tell the difference between the two buttons (so they either both skip to the next track or both skip to the previous track, depending on which way you program them).

I have pulled apart the controls and measured the resistances of each of the different buttons:

Volume Down: 3.11 kOhm

Volume Up: 1 kOhm

Prev Track: 330 Ohm

Next Track: Short Circuit (no resistance) <-- I did not expect this...

My plan is to cut one of the wires and put a resistor in series in this circuit, essentially raising all the resistances by a constant value (I'm thinking a 330 Ohm resistor should do it), in the hope that the head unit will then be able to tell the difference between all of the buttons.

Before I do this, I was just wondering if anyone else has had a go at fixing this in the past, and if so, what did they do??

On a side note... I'm also going to replace the dodgy dull green LEDs that light up the steering wheel buttons with some brighter white LEDs. These are quite small surface mount style LEDs, so they might be a bit fiddly. We'll see how I go. I'll take some pictures and post a bit of a guide if anyone is interested.

[HAMSTA]

Yes please dear! :-) Surface Mount walk through would be just grand!

[Steven]

Does your autome headunit have the option to change the resistance values for the steering wheel button functions? If so you'll probably find you can get them working by altering these digital values rather than attempting to replace the SMD resistors on the circuit boards themselves.

Also I think I used 1056 type smd leds on the circuit board as, even though theyre smaller than the factory type they still output more than enough light. They're still a pain to solder though as you need to be quick to ensure you don't overheat them and obviously their size makes them fiddly. It's not something I recommend if you haven't much experience soldering.

[Matt.]

I'm fairly sure the autome unit allows you to reprogram the function of the buttons, but not change the expected input resistances associated with them. I was more thinking of cutting a wire and putting a resistor in series to effectively raise the resistance of all buttons by the same constant value as it seems that the unit struggles to distinguish between small resistances - so hopefully bumping them all up a bit will move them into a better range (it's really just a big guess...).

As for the LEDs, I've done a reasonable amount of soldering with PCBs (student electrical engineer) and I intend on doing it using the awesome equipment in the labs at uni. I'm considering either "borrowing" some LEDs from uni or even desoldering some off some spare T10 style SMDs that I have lying around. It'll just be a bit of an experiment I suppose :)

[Steven]

I'm fairly sure the autome unit allows you to reprogram the function of the buttons, but not change the expected input resistances associated with them. I was more thinking of cutting a wire and putting a resistor in series to effectively raise the resistance of all buttons by the same constant value as it seems that the unit struggles to distinguish between small resistances - so hopefully bumping them all up a bit will move them into a better range (it's really just a big guess...).

As for the LEDs, I've done a reasonable amount of soldering with PCBs (student electrical engineer) and I intend on doing it using the awesome equipment in the labs at uni. I'm considering either "borrowing" some LEDs from uni or even desoldering some off some spare T10 style SMDs that I have lying around. It'll just be a bit of an experiment I suppose :)

I've tried desoldering LEDs before, it's very risky as about half of them end up getting killed by the heat before the solder on the pads reflows enough to remove the led.

As for putting a resistor in series to raise the overall values, you will still have the same small difference in button values and further if the autome unit doesn't allow you to change the expected input resistances then in all likelyhood you won't be able to get any of the buttons to work as then they will all be out of range.

[DJKOR]

I've tried desoldering LEDs before, it's very risky as about half of them end up getting killed by the heat before the solder on the pads reflows enough to remove the led.

I have confidence that Matt should be able to tackle the task at hand with no issues. It will probably be easier for him because his uni would have a set of SMD soldering/desoldering tweezers.

On a side note, it's quite funny because after meeting Matt in person, he reminds me (looks wise) of a lab partner I had when I went to QUT.

[Matt.]

I've tried desoldering LEDs before, it's very risky as about half of them end up getting killed by the heat before the solder on the pads reflows enough to remove the led.

There are a few things that can make things a bit easier. Firstly, FLUX IS YOUR FRIEND! This helps spread the heat from the point of contact with the soldering iron to the entire "blob" of solder. But secondly (and probably most importantly) adding fresh solder on top of the old solder helps a lot! The fresh solder melts much more readily, and once it is molten it then provides a much larger spread of heat to the old solder.

In any case, it's going to be a bit of fiddling around to see what works. Experimenting is half the fun anyway, right?

On a side note, it's quite funny because after meeting Matt in person, he reminds me (looks wise) of a lab partner I had when I went to QUT.

What did you study at QUT? I used to study there...

Edited March 9, 2011 by Matt.

[Matt.]

Just an update for anyone interested... I finally got around to replacing the surface-mount LEDs for the steering wheel controls. I changed them from the dodgy and barely visible dull green lights (left image) to a nice crisp white light (right image). If anything they're now a little too bright, but these were the least bright LEDs I could get. Looks pretty good at night :)

[DJKOR]

Those were the white ones I used on my last Aurion. Lasted half a night before I took then out and tinted the inside plastic because they were to much of an annoyance while driving.

[Matt.]

That's exactly where I am at the moment... I'm just trying to come up with a good way of tinting the inside of the buttons. I've tried a few things, but I want a nice even colour rather than bright/dull spots. What did you use?

[DJKOR]

What did you use?

A black marker pen