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Resistance ladder circuit

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Keith1054

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I'm not exactly sure what this would be called, so I will try my best to describe what I am trying to do. I just bought a newer style steering wheel for my car so now I have buttons on the wheel for my cruise control as opposed to the stalk coming out of the steering column that I currently have. I thought every button on the wheel would have its own wire and I could simply hook it up to all the appropriate functions and I would be done.
However after a little research (I haven't actually received the wheel yet), I found out that it utilizes a resistance ladder to perform all the controls. Since I don't have the wheel yet to measure the actual values, lets assume they are 50, 150, 300 and 500 ohms for each corresponding button presses (on/off, set/decel, resume/accel, cancel). All I would like to do is come up with a circuit that can "sense" what button was pressed by measuring the resistance and then close the appropriate switch which I could then connect to my existing controls.
Would I need some sort of programmable circuit to enter in the actual resistance values to the circuit I want closed, or is there existing chips that could do this for me?
I know this has to be possible and hopefully it is pretty easy to do. Any help would be greatly appreciated.
 
You need to wait until you have actually measured the resistance values, to see if the resistance values upon button press changes with a certain pattern or just randomly nice round figures.

Depending on the values, the solution might be different. It can be as simple as an LED bar graph IC which turns on its various output depending on the input voltage, or comparator+logic gating to determine which button is pressed. The most elegant solution is to use a microcontroller chip with an ADC pin but hat requires some programming.

Anyway, it is definitely possible to tackle the problem in different ways.
 
You will also have to determine what happens if you press more then one button at a time. Depending on how the switches are wired it you might have to account for more possible resistance values then just the number of switches.

Lefty
 
Thanks for the input so far, once I actually get the buttons I'll have to measure what is actually going on. Thats a really good point Lefty, I didn't consider the possibility of more then one button being pressed at a time, it will be interesting to see what happens.
 
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