In order to produce an analogue signal for control of for example a wiper, a multistage fan or headlight control you do, according to manual, add resaistors in series including one for the "Off" position. The reason to do this, is to inclode all necessary function within a limited number of inputs.
If you use OEM style switches there are often an open loop at the "Off" position.
Will the system accept an open loop (endless resistance = zero volts) as an operative position, or will you end upp with an error?
Pär Stenberg
Hi Pär,
On PDMs sold in the last year, the inputs all have both a pull up and pull down resistor installed internally. This has the effect of holding the input voltage at approximately 15% of the ignition input voltage. This allows the user to use both 12V and 0V switching on the inputs without any external resistors.
For your situation, you could calculate the effect of these internal resistors on your resistor divider switch, but a better way to do it would be empirically with a small bench test set up.
If you connect your multiple position switch to the input, then each position will produce a different voltage on the input. You can use the input voltage directly in your output functions, but a better way to do it is to make a Maths Channel which divides the Battery voltage by the switch input voltage. The output of the Maths Channel can then be used in your output functions, and the value wont vary with the battery voltage.