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Combining inputs

PDM Installation & Configuration

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I am working on my AIM Pdm installation and have a query regarding the inputs on the indicator/beam stalk. I was going to ground each switch to use as a digital input but this chews through the available Inputs... Without buying the expansion module could I add resistors to each grounding of these switches that are different and use just 1 analog input then define which each signal does? If so resistors would I use and would I still use the internal 2k pull up resistor?

Thanks Karl

If your stalk switches are independent (like one for pull on stalk, and one for push, you can't do both at the same time), then you can use a different resistor to ground for each one along with the built-in pull-up resistor. The voltage divider equation (R1 resistor to ground, R2 resistor to voltage reference) Voltage Out = Voltage Reference * R1 / (R1 + R2). So for 5v reference, R1 of 500 ohm, R2 of 2000 ohm, you would get a voltage of 1v. Using R1 of 1000 ohms would give a voltage of 1.6v.

Good idea for normal operation.

The high-beam 'flash' may be an issue, though, depending how the lights are wired - or rather the switch?

This is a good idea but there are some tradeoffs:

- you burn through analogue inputs rather than digital which may or may not be a problem depending on what other sensors you are using

- you can group inputs that are mutually exclusive. E.g. if you have three wiper positions we know it can be on both fast, medium and slow all at the same time so all the wipers can go to one analogue input. Maybe another for light switch (parkers, low beam, high beam). Another for left and right signals.

Or you could look at something like the ECU Master CAN switch. It's got 8 digital inputs, 8 analogue inputs and a few digital outs and all that gets to the PDM via CAN taking up no digital or analogue slots. It's small (I think 25x25mm) and is about AUD$240. I'm planning to use one for a race car steering wheel for the various buttons required.

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