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Thread: arduino to read car sensors

  1. #21
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    All I can say is that you are wrong. You did not see what you though you saw. If you did, you are in disagreement with many people hereon and elsewhere, textbooks, and the best battery experts on the planet.
    But be careful - I am ONLY talking about NOT having to match batteries when charging in parallel.
    I am NOT talking about matching batteries in series, or when leaving batteries connected in parallel when NOT charging.

    I challenge your instructors to dispute the above. Or provide me with contacts so that I can query them direct.

    If however you wish to continue to allow me to continue my belief by not providing contrary support or theory or resources and are unwilling to help, I guess that's my disappointment and loss.
    If you wish to continue your belief, that is your prerogative. I can only do so much to try to correct misunderstanding and untruths and prevent vested interests making money thru false pretenses.

    But end of this tangent. I now see why I never got a response to my PMs.


    Sorry settra!

  2. #22
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    As I said before, I will refrain from further commenting in this thread. I may decide to start another thread but I am not going to get into a drawn out conversation here in this thread. Lets keep the information in this thread to the topic on hand. All I said was that it was nice for a change to comment on a thread where we both agree... That is all...

  3. #23
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    well, even though i certainly cant seem to get how the parallel battery charging came to the post, i Will say, that ofc i have tried to find the shop manual.do you have an idea how old that car is?? in fact, i got to the audi service here, and we found the manufacturers repair manual. IT WAS CRAP. it hardly helped me find the location of the sensors. but what readings do they give? ha. FYI at the hall effect sensor (rpm) the idea of how to test if it works ok, it was to connect a test light and see if it flashes (which is ok today that we have LED's .. but at 90s with the crappy heat light bulbs i cant seem to see how it would work..)
    i asked if i could get one, but they sed no, because as expected, the manufacturer wants to keep info for himself.. but i really dont see why u think its so hard calibrate the system.. all you need is some testing!!

  4. #24
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    Lie I said, sorry settra. I've been seeing too many replies about how redheadedrod & I disagree and, probably since I think highly of redheadedrod and his replies, I git a bit sick of it. The paralleling of batteries was the only issue I see. But redheadedrod is cool and had other priorities. It's not like the last time I had a similar issue where some Swedish BMW owner with over 20 years of car(?) electrical experience resorted to put downs despite proving himself ignorant of Ohms Law and simple circuit theory. But that was fun - he even went and deleted all his incriminating posts LOL!


    Now, as to your Audi... (yay!)
    An Audi 80, b4 1990. (Is that a model - B4 like A4, or meaning before 1990? I guess I can check...)

    It should be possible to find suitable info, though a line last week comes to mind - "... they changed wiring no less than 17 times in one year..." - or was that sensors, and was it a German of a French car?

    But chances are that sensors will be similar even if changed. And with those vehicles, checking wiring with a DMM and continuity checker is essentially mandatory - even when one has the best correct workshop manual.

    It's usually a matter of getting a ball-park spec for the sensor. Whether a temp sensor is 76 Ohms or 200 Ohms max isn't a big deal. (Remember, an easy interface board where you can easily swap resistors etc.) And if designed for the worst case, it's only if you want better accuracy that resistor swaps matter - ie, changing the sensor range to match the highest Arduino input range.
    And swapping the "sense" of a sensor is usually a mere program change - eg, if the temp sensor is 6R cold and 76R hot, or 6R hot and 76R cold. (Where R means Ω - Ohms. "R" is a common substitute on web forums.)

    And the Hall Effect sensor... They would have tested with a small bulb - eg, a test light using a 2W or 3W bulb. A big bulb or headlight would have blown the sensor, but could have been used to test the ignitor (which the Hall Effect sensor controls, even if via an ECU/EMS) since ignitors switch IgCoils which have currents of up to 10A - 13A etc.
    But yes, hail be our LEDs! A great output with a mere 10mA-20mA loading. Still not to be used anywhere near O2 sensors and some other circuits. In fact NO DMM should be used to test an oxygen sensor - even 1uA can kill them!

    But using the Hall as an example. I'll be the instruction was to clip the test light to +12V and the other end to the Hall output. Then (with IGN on) rotate or crank the engine and the light should flash.
    If so, that proves it's an Open Collector or "grounding" output. It's probably the same test for the ignitor which is exaclty the same OC/grounding output except it handles far more current and will give a heck of a big kick (like ~200V) when the ignitor turns off.
    There can be exceptions to the above - especially "ignitors" for CDI systems, though the signal to the CDI ignitor is probably still ground switching.
    And some Hall Effects modules can be +12V or +5V output, but they are not commonly used. Many used the Siemens HKZ101 or similar HKZ family which AFAIK are all OC outputs.


    So where now? A list of the sensors you need to interface to?
    And trying so search those sensors through sparts catalogs for specs, or comparing to other VAG (German) vehicles of similar vintage?

    It might be easier doing all you own wiring. My suggestion is to leave the standard wiring as is (unless it would need to be replaced with a new loom anyhow) since you probably only need thin wires to sensors, and since they have to be connected to the Arduino boards anyhow...
    That does depend on what connectors are used for the sensors, and if you want to cut or tap into them.

  5. #25
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    What I am talking about is a true factory shop manual. Not an aftermarket attempt at a shop manual. While chiltons and similar fix it books have helped me in the past I have never regretted spending the money for the actual shop manuals the dealers use. I posted a link to one that was available for the electrical system for your car that was cheap. It should go over where every wire is located and what every sensor range is. These are trouble shooting manuals for dealer mechanics to figure out if the sensors are working correctly and will contain all information for them.

    When I did a search for your car they had like 6 different manuals available for them for different things such as electrical, engine, body etc. The one I listed was singly listed on its own.

    I have used Ford and GM manuals and they tell you the torque for every bolt and part numbers to replace components. Along with the expected sensor range so they can test the computer inputs as well.

    As I also mentioned you can likely search for the sensor part its self and find out by checking its specs what the computer will be looking to do. But you should do something to determine what each sensor specifications are instead of guessing. I am just trying to save you some work and possibly you breaking stuff but you are more than welcome to not follow my advice. I have done what you are doing and have broken some pretty expensive components which led to my finding the true factory shop manuals. Of course since the modern GM cars all come on DVD now so it is easy to get a copy. But that won't do you much good since all of the older audi stuff I found was all printed format. And some of the manuals I saw were around $150 apiece.

  6. #26
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    So was I.
    It's VAG, not Jap nor GM.

    Did you look in any of the Audi factor manuals that you saw?

  7. #27
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    so, some feeback. after all, the hard part is the resistive sensors! for all the others, now that i got some experience, you where right oldspark. voltage divider is the simplier think to do!!

    but the resistive sensors are a problem for many reasons. mainly because, since their resistance changes, you cant use a diode to isolate the grounds, because diode drains voltage depending on the ampere that flows through it. witch in turn, depends on the resistance... so unless you want to solve differential equations, you cant use a diode ... arduino has 3 isolated grounds so you can only measure three resistances... which insist a problem since temp and fuel are the only important (++ a photo resistor maybe ?? )

    THE HARD part, is that, the fuel and temp sensors, are wired to the car's electronics, and after all, grounded at the same point... so if you try to measure the resistance , the voltage from arduiono, go the other way (not through the resistance) ... i have solved it in fuel, by just cutting the wires from the sensor to the car (didint used them anywhere else anyway). for the temp, i am thinking of buying an extra temp sensor to put only for the arduino!

  8. #28
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    Perhaps I am missing something and if so then I am very very sorry but why not use the OBDII interface to read all the data?

  9. #29
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    what do you mean? this post is prety old, but as i have staded before, the car did not have any kind of diagnostics , on it...

  10. #30
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    Sorry, I didn't see anywhere that it did not have any Diag Ports, I seen mention that the dash was messed up, but the old Audi that I worked on for a friend had them, should say he used my tester all the time.
    Again sorry

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