As with many digital control circuits, things are not modulated but rather
turned on or foo with the "on time" or ratio of on to off time achieving the
required results. The injectors are the primary example of this. They turn
on once every engine revolution. The ECU changes the length of this "open
time" to control the fuel delivered. If they were on all the time the duty
cycle or pulse would 100%. Thing of dwell back in the ignition points days.
There we used the angle to set the points. The longer the dwell, the better
the coil could charge before we opened the circuit to make the spark.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
JRodgers
Sent: Saturday, November 16, 2013 11:13 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Arduino and Vanagons

Uh, I seemed to have missed something in this discussion What is a/the PWM?
It just doesn't come to me.

Thanks,

John

On 11/15/2013 10:03 PM, Brett Ne wrote:
> GoWesty emailed back and declined to share their information, citing
> "that data is proprietary".  It really isn't, just as knowing the
> expected output voltage range of a healthy voltage regulator isn't
> proprietary.  Oh, well, it was worth a try...it just means a little more
work on our part.
>
>
> So, here's what we need to know:
> * The PWM duty cycle being feed to the idle air valve when:
>       --the engine is cold, the starter is engaged, and the coil is
shorted
>       --the engine is cold & running
>       --the engine is fully warm & running
>       --the engine is fully warm & running with PS operating
>       --the engine is fully warm & running with AC on
>       --the engine is fully warm & running with PS operating and AC on
> *  The current draw from the idle air valve at a known duty cycle.(or
> feed it straight 12v and measure the current draw.)
> * The base voltage and the peak voltage coming from the Hall sensor
> The above items will need to be done by someone with a scope and a
> healthy ICU & idle air valve(and PS & AC).
>
> *  Which connector, 4/ST2 or 11/ST1, supplies the PWM power to the
> idle air valve. (and confirm that whichever supplies the PWM power,
> that the other is a ground connection.)
> *  What is the voltage at the coolant temperature sensor when cold and
> when
> 160 F.
>
> I think that this would provide all the information needed to design
> the circuitry and program the microcontroller to drive the idle air valve.
>
>
>
> And once a prototype is built, we will need a vict-- I mean
> volunteer-- to connect it to their rig for testing & fine tuning.
> Preferably in the Portland, OR area.
>
>
> --
> Brett in Portland, OR
> "Albert" '82 VanFox I4 Riviera
> .
>