Earlier this week I recieved a PAC SWI-3 steering wheel interface that I'm sure many of you are aware of. Basically what it does is sample a given IR remote and then play that sample based on steering wheel button pushes. The "-3" that I have is for the switched resistance type steering wheel buttons. Well, I installed the thing and it worked marginally well for single event functions like track advance, but for continuous output like a vol +/- it was laughably slow. I'm not sure if the duty cycle of the sample rate is what was slowing it down or if there was a problem with the kenwood transmit frequency.

I believe it was the sample rate... so I went about building my own that I could interface directly to the supplied kenwood remote and my Honda steering wheel. I built a small card that would essentially "push the buttons" of the kenwood remote via a standard analog switch (4066). The resistor switches in the wheel provide variable gain to an op amp circuit (741) which is then decoded by way of a bank of six comparators (339). It's an extremely simple design, and one which you can add functions too.. I added a single button to serve as a bank select to up my wheel functions from 3 to 6.

I've attached a pic of the board for grins (please note the sloppy addition of some pull-ups on the ctrl outputs, oops), but I have yet to wire it to the kenwood (I'm deciding on the best functions to have on the wheel). If anyone is interested, I can provide them with schematics or other helpfull hints as how to duplicate the setup.

I'll post an update when I'm done testing and have it installed...

Thanks

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looks like the pic didn't make it.. here's a lower res ver.

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Very interesting! Looking forward to seeing more details about the project. Thanks for showing it to us!

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Tony Fabris

I connected the thing to the kenwood remote and installed it using the wires from the SWI-3 along with the IR LED on a 3ft cord. I taped it up, tied it in, and it works flawlessly. Unfortunately my gf took the camera earlier today so I have no pics. However, I still need to add the fourth switch to the accord steering wheel button assy. I'll take a couple then of the switch and the IR LED placement.

This was really an easy project with radio shack parts execept I used some odd resistor values to make the comparators and reference voltages very precise. A small digikey order would be a good bet.

Due to the use of voltage dividers everywhere, temperature tracking shouldn't be an issue. However, the resistors in the steering wheel may be a bit different. I attempted to make the comparator windows as large as possible to compensate. If someone tried one with 12-16 functions I'd be curious about the temperature stability.

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I didn't realize it was for an Accord. Now I'm really interested.

How many buttons have you got going there? What functions do you have on the steering wheel now? Did you wire directly to the accord buttons or plug into their harness inside the dash?

My car didn't come with radio buttons on the steering wheel (it was the next model up), but I think I could order the button assembly from Majestic if I wanted to.

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Tony Fabris

I noticed some anomolies today when I drove around enough to give it a good test... looks like I forgot to compensate for the resistance of the rotary joint. Oops. Well I had measured it to be <5 Ohms, but apparently failed to realize that this can peak much higher when rotated. So, I had to pull it out and scale some resitors up a bit, a chance to take the attached (blurry) pic.

Tony, I have vol+, track inc, and vol- as the default three buttons. I will soon add a fourth button (all of the circuitry required is there) when I find a good switch for the application. This will allow me to select another bank of three buttons which I have wired to menu (*), track dec, and OK. I think this will be a good choice in practice, as all I generally do is thumb through the menu, pic a playlist, and skip the tracks I don't feel like listening too. Now I can do it all from the wheel.

And yes, I pull the remote wire from the factory stereo harness. This gives me the rotary joint connection to the wheel buttons, and I replaced the factory resistor values as well. In the pic you can see the green remote wire, the fused ACC wire, and gnd. In the back by the volume knob you can see a thicker black wire which was used to remote mount the IR LED as well. The card from the Kenwood can almost be seen mounted to the back of the card I did.


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