Pot position measurement

[FFMan]

On my cruise control project, the pedal actuator has a position pot, but strangely I can only find 2 wires, and resistance varies from approx. 0 ohms to 2.8k from end to end travel.

I was expecting a 3 wire pot I could put a voltage across and measure the wiper output but this doesn't seem to be available.

what is the best way to utilise a variable resistance interfaced to a zx40n ?

thanks

[Don_Kirby]

Perhaps it's using a reference to ground via a metal mounting surface?

[FFMan]

there are 3 wires related to this function but I can't work them out. the casing is plastic so no metal surfaces.

I have a spare actuator, so I might dismantled it to see what is going on

I have a wiring diagram for the previous model and it has a standard 3 wire pot.

[stevech]

On my cruise control project, the pedal actuator has a position pot, but strangely I can only find 2 wires, and resistance varies from approx. 0 ohms to 2.8k from end to end travel.

I was expecting a 3 wire pot I could put a voltage across and measure the wiper output but this doesn't seem to be available.

what is the best way to utilise a variable resistance interfaced to a zx40n ?

thanks

If the postion pot is truly analog, not pulsed (used a 'scope on it?)... then a pair of high value resistors would produce a scaled voltage suitable for the A/D in the microprocessor?

[FFMan]

swapped in the other actuator and it behaves as a 3 wire pot - so the 1st one must have a fault on the position pot

maybe why it was on ebay ?

so this should be easier now.

[DocJC]

Probably worth having a look at this link: http://www.avrfreaks.net/index.php?name ... c&t=137489
on AVR Freaks, regarding automotive control software.

JC

[FFMan]

interesting article, and of course there is an important safety aspect to this project.

it should be noted that the only interaction with accelerator is mechanical, there is no interfacing to the engine cpu or control systems.

the actuator contains a safety clutch that is electrically controlled and immediately releases the tension when power is withdrawn. there will therefore will be an override switch in this power line very close to the steering wheel. regardless of what the cpu does, the clutch can be released.

the use of cruise control is somewhat different to general throttle control system. the cruise will naturally only be used on large roads, at a time when a constant speed is required. disengaging the system is usually done as part of the planned deceleration process

it needs care and attention for sure.

thanks