pull up resistors, pull down resistors

[Escort Paul]

Can anyone explain these to me ( the dummy version will be ok ) as I need to understand them a little better.
Im doing alternator control via EMS PWM output, so I need to understand this a little bit better, Im just convinced Im going to cook my ECU.
And before anyone says it its a cast bracket so the alternator is not easily replaced with a 1 wire Alt.

regards Paul

[mk e]

Can anyone explain these to me ( the dummy version will be ok ) as I need to understand them a little better.
Im doing alternator control via EMS PWM output, so I need to understand this a little bit better, Im just convinced Im going to cook my ECU.
And before anyone says it its a cast bracket so the alternator is not easily replaced with a 1 wire Alt.

regards Paul

Here’s the for dummies follow…are you trying to use the ECU as a voltage regulator or are you just trying to send an “engine turning” signal? In the case of the latter I personally would use a relay of some kind and not worry about anything bad happening to the ECU….there is a lot of juice and noise at the alternator. In the case of the former…..I would buy a voltage regulator at the auto parts store.

[Fred]

PM AbeFM about this as I believe he has an alternator control circuit that functions for his Miata.

Pull up and pull down are there to bring a floating signal to one end of the spectrum when it is floating such that when the input signal drags it the other way it is clear that there was a transition.

EG you have a pull up to 5v on a switched input such that its always at 5v and when the switch closes it gets grounded and reads 0v. if you didn't have the pull up the voltage would be all over the place including 0v and would produce false readings.

Does that help? :-)

Fred.

[Escort Paul]

yeah the ECU is acting as the regulator, but I am open to any alternative so I will contact abeFM

regards Paul