Cool!! Explains a lot.

Thanks,

John

On 11/16/2013 10:33 AM, Brett Ne wrote:
> Good question.  PWM (Pulse Width Modulation) is a way of controlling
> electrical power digitally.  Let's say you want the idle air valve
> partially open.  It's actually kinda hard (re: expensive) to limit the
> current flow to the valve.  So instead, we just switch it on-off-on-off...
> very quickly.  Since it's only switched on part of the time, the amount of
> current reaching the valve is limited, and if we do it quickly enough, the
> valve acts like it's getting a controlled amount of constant current fed to
> it.  Typically in PWM applications the frequency of the pulses remains
> constant and the width, or length of time the voltage is on is varied.  So,
> for example, suppose one on-off cycle is 10 milliseconds.  If we want to
> limit our output to 50%, the voltage is switched on for 5 msec and off for
> 5 msec, and repeated over and over.  if we want 80% power, we switch
> voltage on for 8 msec and off for 2 msec.  This allows us to digitally
> control an analog output very easily.
>
>
> On Sat, Nov 16, 2013 at 8:13 AM, JRodgers <jrodgers113@gmail.com> wrote:
>
>> 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
>>> .
>>>
>>>
>
>
> --
> Brett in Portland, OR
> "Albert" '82 VanaFox I4 Riviera
>