Paddle shift touch sensor

[Jim Blackwood]

So I ran across a neat capacitive touch sensor demo board and got one shipped to me, it's by NXP, part number OM11052:
http://www.nxp.com/demoboard/OM11052.html

As near as I can tell from the specs this thing can have up to 10mm of gap to sense touch and can be wired to an external sense electrode. So naturally I thought it might be useful for paddle shifters. Maybe some of you can take a look and see what you think. The user manual is:
http://www.nxp.com/documents/user_manual/UM10711.pdf

Looks like it runs on 3-9Vdc so a limiting resistor will be needed or maybe a voltage regulator, or it could perhaps run off the 5v supply.

The board itself has no attachment points for external sense electrodes. It has a couple of pads on the board. I plan to power it up and play with it a bit. I think it outputs a 250ms pulse when it detects which I'm thinking should work pretty well for a shifting signal. That big pad on the right is the smaller of the two and the other one is a long one on the back, about half the length of the board. Maybe we could scrape off some insulation and solder a lead on there. It's small enough (about 5/8" wide) that it can be concealed inside the steering column cowling in many cases.

The advantage of course is that the shifter paddles can be hard mounted (with an insulator). No pivots or mechanical switches. That should simplify mounting a bit.

Opinions?

Jim

[Jim Blackwood]

A little more info:
The outputs are high and get pulled low when it switches. [An LED stuck in the OUT and GND holes lights when power is on (I'm using a 9V battery) then goes out when triggered] There are trigger LED's built into the board as well which light during output (low). So it could take the place of a grounding switch possibly. I have not checked if it will sink an external source yet but based on the schematic it looks like it would (10K resistor on the 12v output source on board.) The schematic shows 12v as the source but the specs say 3-9v. It might be worth contacting them to see what the upper voltage limit really is.

The time period looks to me like more than 1/4 second, closer to 1 second. This would limit multiple downshifts. I'm not sure how hard it would be to modify that, a resistor change on the board no doubt but it is SMD. Not terribly dense though so possible. Just have to figure out which one. I'll try to hook a scope up to it later to get an accurate time pulse.

Jim

[Jim Blackwood]

This morning's testing shows it does work with gloves on. I also soldered long leads to the pads, about a foot long and touching those switches it. I clamped one lead in the small vise I'm using and the vise made a good electrode. I think this will work. I haven't heard back from them yet on the max voltage though, so for now a dropping resistor is probably a good idea.

Jim

[Bernard Fife]

Jim,

That's cool that it works, nice find!

Lance.

[Addicted]

I like the look of these, great find, where did you purchase yours from? I can think of a couple of applications..

My only concern with its use as a shift button is any accidental contact will cause a shift compared to a physical switch. Personally I use a membrane switch on the back of the steering wheel spoke and when driving my finger pretty much sits on it, I wouldn't be able to do that..

[Jim Blackwood]

That link above is where I got it, they sent me an engineering sample but you should be able to call and buy them outright. They only had one sample available when I called them.

What I plan to do is make a set of stationary electrodes behind the steering wheel and bolted to the steering shaft cowling so that each one is a half circle (or a bit less) of about a 9" diameter an inch or inch and a half forward. There is a good mounting position for them bolted through the plastic with a plate on the back and the wires can connect inside that way with the board concealed in the cowling. That way upshift is always on the right and downshift is always on the left and being inside the stalks there's little risk of hitting them accidentally but they are still just a finger flick away. I bought some 5/16 titanium rod to make the electrodes with but I'm waiting on a quote for some plate and filler wire to complete them. Not terribly expensive and it'll be cool to be able to say they are Ti but anything else would work too. I guess I just wanted an excuse to play with some of that material.

Also for those of you who are good at engineering, there is a schematic and you can buy just the IC chip, so working up a more compact board with attachment points for the sensor wires and a shorter or selectable pulse (Maybe by mounting different resistors) and built to run on 12Vdc automotive shouldn't be too difficult. I could see that being a moneymaker for someone.

Jim

[Jim Blackwood]

After some thought, maybe that last sentiment wasn't entirely in keeping with the open source nature of the entire Mega community so apologies all around there. I was just thinking it might be a useful thing for anyone wanting paddle shifters. But the circuit is not complicated, the demo board seems to work and I believe it can be purchased though I don't know the price. Certainly the chips are available.

I made up a set of electrodes for it out of the titanium rod I had, 1/4" diameter, not 5/16' as I had said above. What I did was bend the rod into a sort of D or bean shape so each paddle takes up almost half a 9-1/4" circle with maybe an inch of gap at top and bottom between them. I'll weld those to small plates that will bolt to the ends of the steering column cowling, positioning the paddles about 1-1/2" forward of the steering wheel rim. Just have to wait on some material to complete them.

Jim

[Bernard Fife]

After some thought, maybe that last sentiment wasn't entirely in keeping with the open source nature of the entire Mega community so apologies all around there.

Jim,

I don't see anything to object too at all.

Lance.