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Date:         Tue, 26 Nov 2013 16:49:07 -0800
Reply-To:     Brett Ne <brettn777@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Brett Ne <brettn777@GMAIL.COM>
Subject:      Re: Arduino and Vanagons
In-Reply-To:  <5295117B.6060703@gmail.com>
Content-Type: text/plain; charset=ISO-8859-1

I could use some information on the packaging of one of these $190 gems. If someone has one of the ICUs sitting around on a shelf, could you send me a closeup shot of the bottom that shows the metal tabs and the embossed numbering next to the tabs? Also, What are the outside dimensions of the plastic case? And, finally, what is the distance between the middle tabs in the two clusters of tabs. In other words, the bottom tabs look like two relays joined together, and on a relay, a tab in the middle is labelled 87A, what is the distance between the two 87A tabs?

I found a nice Arduino library(a program that someone else has written with the express purpose of other people using parts of it in their own program) that allows 10-bit pwm resolution. This means 1024 different settings for the pwm duty cycle, which allows a resolution of 0.1% . This will give us a nice level of control without having to monkey around with individual timer registers.

Brett

On Tue, Nov 26, 2013 at 1:24 PM, JRodgers <jrodgers113@gmail.com> wrote:

> Brett, > > I am really looking forward to this. I have three vans and the ISCU > doesn't work in all three. > > Thanks for what you are doing and to those who are contributing support in > whatever form. > > John > > > On 11/26/2013 1:26 PM, Brett Ne wrote: > >> A manual pwm idle controller...I love it! I know, I overthink things a >> lot. After all, my first car just had a carb with a manual choke. The >> only feedback mechanism is the driver: "It feels pretty chilly this >> morning, I'll pull out the choke *this* far...hmmmm not starting...I'll >> pull it out *this* much farther and try again..." And the carburetor >> itself was little more than a tiny little straw with one end in a bowl of >> gas and the other sticking out in the middle of a narrowed tube with air >> flowing by. It's amazing that we could actually get a car started and >> running with such a hokey system! >> >> I'm going through these tests and thought processes because I want the >> final design to be plug and play and forget about it. I want it to work >> better than the stock unit. And it should work fine regardless of >> variances between cars; you add an air conditioner to your car & you don't >> have to worry about the idle; maybe someone in Arizona has two air >> conditioner compressors going; maybe someone's idle control valve has a >> weak spring and 40 mA will open the valve wide open; it shouldn't matter; >> the controller just adjusts the current going to the valve until the >> airflow creates the right idle speed. >> >> Yes there are many inexpensive pwm boards available. But the Arduino, >> doing millions of calculations per second, will be spending most of its >> time picking its nose waiting for something to do. There is plenty of >> computing capacity to handle the pwm so there is no need to add a second >> chip to the circuit. >> >> >> Brett >> >> >> On Tue, Nov 26, 2013 at 8:56 AM, Angus Gordon <birdworks@gmail.com> >> wrote: >> >> >>> Brett, great that you're working on this. I haven't had time to follow >>> closely and didn't realize the Arduino has a built-in PWM function. If it >>> lacks the resolution needed, how about using the Arduino to regulate a >>> dedicated PWM controller? >>> >>> When the ISCU quit working on my Syncro I disconnected the ISV and drove >>> that way for a couple of years. The only time I missed the ISV was on >>> cold >>> starts, say below 40-50F. Granted, I have no AC or PS. After a cold start >>> I'd have to hold the throttle open slightly to keep it idling, until it >>> had >>> warmed for one to two minutes. >>> >>> I added a 'manual' PWM controller so the engine would idle while I got >>> out >>> to scrape the windshield. In stock form the PWM control was very >>> sensitive, >>> but after swapping a potentiometer matched to the range I needed it works >>> quite well as a form of manual idle speed adjustment. Once the engine is >>> warmed somewhat I shut it off. >>> >>> As I'm sure you're aware, dedicated PWM boards are super cheap. A few >>> years back I think I paid $10 for mine. Today you could likely find a >>> suitable controller for $2. >>> >>> Thanks again for undertaking this, a computer controlled (cheap) idle >>> would be a nice thing to have again. >>> >>> >>> Angus >>> >>> >>> >>> On Tue, Nov 26, 2013 at 8:10 AM, Brett Ne <brettn777@gmail.com> wrote: >>> >>> We have some data to work with! One of our members has generously put >>>> in >>>> the time and effort to gather most of the readings we need. Here is >>>> what >>>> we have so far: >>>> >>>> *Duty Cycle Under Various Engine Conditions* >>>> >>>> >>>> >>>> >>>> >>>> >>>> *Condition* *Duty Cycle* *Peak Voltage* >>>> >>>> Engine Cold, Key On, Engine Off 34.0% 9 >>>> Engine Warm, Key On, Engine Off 29.4% 9 @ 157 mA Engine Cold & >>>> Starter >>>> cranking (45 F) 55.0% 6 >>>> Engine Cold & Idling 25.0% 10.5 >>>> Engine Warm & Idling 20.5% 10.5 >>>> Engine Warm & Running 2000 RPM >>>> >>>> >>>> Engine Warm, WOT Signal >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> *Duty Cycle Under Various Load Conditions* >>>> >>>> >>>> >>>> >>>> >>>> >>>> *Load* *Engine Cold* *Engine Warm* >>>> >>>> None 23.0% 20.5% >>>> AT in Gear 25.5% 23.0% >>>> PS 27.0% 25.0% >>>> AT in Gear & PS 30.0% 27.0% >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> *Miscellaneous:* >>>> >>>> >>>> >>>> PWM Frequency constant at 148.2 Hz >>>> >>>> >>>> >>>> >>>> Yellow Wire (11/ST1) PWM Power to Idle Stabilizer Valve >>>> >>>> >>>> >>>> >>>> White Wire (4/ST2) Ground Connection? (Needs to be confirmed) >>>> >>>> >>>> >>>> >>>> >>>> >>>> From this we can conclude: >>>> **The idle air valve is very sensitive. A 7% increase in duty cycle is >>>> able to overcome the combined loads of AT in gear and PS at full >>>> pressure. >>>> The built-in PWM output on the Arduino only has 256 settings, which >>>> would >>>> give use increments of 0.4% in the duty cycle output. This would work, >>>> but >>>> I think that there would be a noticeable unevenness in idle speed. Not >>>> a >>>> big deal, it just means that we will need to use a timer interrupt to >>>> gain >>>> fine control over the duty cycle(the percentage of "on" time of the >>>> pulse) >>>> of the PWM. It's just not as fun and easy as using the built-in PWM >>>> functions. I'll explain interrupts in more detail when we get to the >>>> programming stage, but it basically is just a way to grab the computer's >>>> attention and make it suspend its current operations while it attends >>>> to a >>>> time-critical event, like a new hall sensor pulse coming in. >>>> >>>> **Most of the time, the duty cycle is pretty low, around 25%, but that >>>> changes during starting. While the engine is cranking, the duty cycle >>>> jumps to around 55%. When I first saw this figure I thought, "Wow, it's >>>> really increasing the airflow a lot while the engine is cranking." But >>>> I >>>> don't think that is true because the current draw from the starter motor >>>> drops the available battery voltage considerably. The stock ICU output >>>> voltage drops from 9v with engine not running to 6v with starter >>>> cranking. >>>> I think the dramatic increase in duty cycle is not for increasing >>>> airflow, >>>> but rather to compensate for the expected voltage drop during cranking. >>>> >>>> **The ICU apparently makes no attempt to send a fixed voltage to the >>>> idle >>>> air valve. With engine off, it sends 9v. With engine running, it sends >>>> 10.5v, which matches the increase in voltage from the alternator. With >>>> engine cranking, the output drops to 6v, reflecting the battery voltage >>>> drop under the heavy load of the starter. For running conditions, we >>>> don't >>>> need to worry about the output voltage level because it will be >>>> automatically compensated for by the engine speed feedback. But for >>>> starting, we could have the Arduino measure the voltage coming from the >>>> battery and calculate the appropriate duty cycle change to have better >>>> control over the airflow. >>>> >>>> **The idle air valve draws 157 mA when supplied with a 9v 29% duty >>>> cycle. >>>> This translates to a 535 mA draw @ 100% & 9v or 4.8 W of power. The >>>> final >>>> drive transistor in our circuit should be chosen to handle 1A of current >>>> to >>>> assure durability. Lots of options here. >>>> >>>> >>>> >>>> What we're still looking for: >>>> >>>> What happens above idle speed? Does the idle air flow shut down, or >>>> stay >>>> at some predetermined level? >>>> What happens at Wide Open Throttle? >>>> What does the Hall sensor output signal look like? I haven't found >>>> anything definitive on the internet. There are hints that it is a >>>> square >>>> wave and that the peak pulses are up near battery voltage. I would like >>>> to >>>> know peak and base voltages and confirm that it's a clean square wave. >>>> Also, has anyone taken apart an idle air valve? Is it just a motor >>>> operating against a spring? >>>> >>>> >>>> Brett >>>> >>>> >>>> >>>> >>>> On Wed, Nov 20, 2013 at 1:41 PM, Brett Ne <brettn777@gmail.com> wrote: >>>> >>>> Before we can go any further with this project, we need those >>>>> measurements. I'm not interested in investing time, materials, and >>>>> >>>> money >>>> >>>>> into a project if it's based on assumptions and guesswork. My Vanagon >>>>> can't be used because it doesn't have the Digifant injection system. >>>>> >>>>> So, we need either: >>>>> >>>>> Someone with an oscilloscope or a digital multimeter w/pwm functions >>>>> who >>>>> has access to a Vanagon with Digifant FI that has a healthy ICU as well >>>>> >>>> as >>>> >>>>> power steering and AC. Bonus points if it's an automatic. >>>>> >>>>> Or, >>>>> >>>>> Someone in the Portland Metro area with a van that fits the above >>>>> description who would be willing to work with me for a couple of hours. >>>>> >>>> I >>>> >>>>> do have an oscilloscope and could take the measurements. >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> On Wed, Nov 20, 2013 at 1:23 PM, Brett Ne <brettn777@gmail.com> wrote: >>>>> >>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> Assuming a properly functioning engine and IS system, if one measured >>>>>>> current draw at the ISV, loads on and off, at idle, cruising speed >>>>>>> and >>>>>>> WOT, could they get a really good idea of when the ISV is used? >>>>>>> (valve >>>>>>> changes position). Maybe a graphing meter would be useful in this >>>>>>> regard? >>>>>>> >>>>>> >>>>>> >>>>>> Current draw or voltage measurements would be kinda okay. They should >>>>>> >>>>> be >>>> >>>>> proportional to the duty cycle, but again, knowing the duty cycle >>>>>> >>>>> tells you >>>> >>>>> exactly what the control unit is doing and is much preferred over >>>>>> >>>>> indirect >>>> >>>>> measurements. >>>>>> >>>>>> >>>>>> >>>>>> My guess is that at idle, no loads (PS, AC) the valve is >>>>>>> closed. Or..... >>>>>>> >>>>>>> >>>>>> ...or partially open. We can all guess until we're blue in the face, >>>>>> >>>>> but >>>> >>>>> if we want to create a re-engineered control unit that solidly >>>>>> >>>>> replaces the >>>> >>>>> old one, we have to establish the behaviors of the old one first >>>>>> >>>>>> >>>>>> >>>>>>> Isn't the ICU basically taken out of the picture any time the >>>>>>> throttle >>>>>>> is just off idle or at WOT? (throttle enrichment switch activated or >>>>>>> not). >>>>>>> >>>>>>> >>>>>> Maybe, maybe not. Maybe the idle throttle opens fully under full >>>>>> throttle to help the engine breathe better. I just don't know. >>>>>> >>>>>> >>>>>> >>>>>>> Did you find the correct "Vanagon" Digifant pro training manual >>>>>>> online? If not, can send more images. There may be some useful in >>>>>>> there for your needs. >>>>>>> >>>>>>> >>>>>> No, I haven't, though to be honest, I haven't been looking. Typically >>>>>> training or repair manuals may give enough info to identify a faulty >>>>>> >>>>> part >>>> >>>>> but don't give all the details on how that part interacts with all the >>>>>> other parts of the system. >>>>>> >>>>>> >>>>>> >>>>>> -- >>>>>> Brett in Portland, OR >>>>>> "Albert" '82 VanaFox I4 Riviera >>>>>> >>>>>> >>>>> >>>>> >>>>> -- >>>>> Brett in Portland, OR >>>>> "Albert" '82 VanaFox I4 Riviera >>>>> >>>>> >>>> >>>> >>>> -- >>>> Brett in Portland, OR >>>> "Albert" '82 VanaFox I4 Riviera >>>> >>>> >>> >>> >> >> -- >> Brett in Portland, OR >> "Albert" '82 VanaFox I4 Riviera >> . >> >>

-- Brett in Portland, OR "Albert" '82 VanaFox I4 Riviera


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