Oil/Transmisson Fluid Level Sensor

Discussion in 'Automotive Electronics' started by MrAl, Jun 29, 2016.

  1. MrAl

    Thread Starter Well-Known Member

    Jun 17, 2014
    2,439
    492
    Hello there,

    Long, long, time ago there was an article in Popular Electronics that had a project about an oil dipstick level sensor. The basic idea was to connect a line of resistors down the dipstick and test the resistance, and the resistance of the string had a correlation to the amount of oil left in the oil pan. The hot oil would change the resistance.

    With today's SMD resistors this could be even simpler, or at least smaller and fit nicer on the dipstick. Also, it might work for automatic transmission fluid too.

    The idea is to be able to test the oil level and/or transmission fluid WHILE THE CAR is being driven, not just at rest. That would be to prevent damage to any of the systems if the fluid got low unexpectedly.

    Anyone ever try this, or any better ideas now that electronics has advanced so much since maybe the 1960's ?

    This would be a good project for anyone that wants to try to make sure they dont run low on some fluid in the car while driving, which is when the damage occurs.

    Thanks a bunch.
     
  2. #12

    Expert

    Nov 30, 2010
    16,338
    6,824
    Trying to do a resistive divider for any number of different oils, which are normally excellent dielectrics?
    I'd be more likely to try a dozen SMT thermistors for the level sensor.
     
  3. crutschow

    Expert

    Mar 14, 2008
    13,044
    3,244
    I would think you would want to use thermistors to get a significant change with temperature.
    Otherwise you would likely want to use resistors with a relatively high temperature coefficient such as carbon composition.

    One question comes to mind: how much difference in temperature is there between the dipstick and the oil?
    I wouldn't think the temperature would be much different since the dip stick would be basically at the temperature of the engine block, which is also where the oil flows through.

    Perhaps it would work better if you ran sufficient current through the resistors to heat them up.
    Then the oil would cool the resistors that were immersed and you could see that difference.
     
    GopherT likes this.
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,999
    745
    How about E-tape sensor...

    etape
     
    AnalogKid likes this.
  5. Lestraveled

    Well-Known Member

    May 19, 2014
    1,957
    1,215
    My Chevy Duramax diesel has an oil level sensor. If I park it at a high angle, like sideways on a steep hill, it yells at me that the oil level is low.
     
  6. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,061
    3,834

    An optical method could be interesting, oil cleanliness could also be reported via particulate/dispersion.
     
  7. #12

    Expert

    Nov 30, 2010
    16,338
    6,824
    My 1986 Aerostar had an oil level sensor. It was the only leak on the engine, and so, justified its existence by notifying me that it had let the oil escape.:D
    I read on the Internet that if you park a Ford Explorer pointed uphill, the transmission fluid drains to the rear and you must move the car to someplace level or it will never go into gear again.:D Neither of these conditions can be cured by adding an oil level sensor.

    My latest car also has tire pressure sensors which always report that the tires are flat. I don't need a faulty flat tire notification and I don't need a microprocessor to check my oil level, but lots of manufacturers want to load dozens of these options which basically say, "You're too stupid to own a car. We have an app for that." Go for it. There's a sucker born every day.:p
     
  8. Lestraveled

    Well-Known Member

    May 19, 2014
    1,957
    1,215
    @#12 You shouldn't spend so much time on the internet. :D My wife had a Ford Explorer and we have a lot of "up hill" around my house. Never had anything like what you describe happen to her car.

    I agree about the tire pressure sensors. They last a finite amount of time and then they go bad. A gold mine for the part suppliers.
     
  9. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,061
    3,834
    Federal law, all cars have to have 'em since 2008. New cars have to have back up cameras next. Let's see how long those will work - and the repair bill when they don't.
     
  10. #12

    Expert

    Nov 30, 2010
    16,338
    6,824
    It doesn't matter here. We don't have hills in Florida.
    Well, we do, but they are so rare that the only one in this county has a name: Thrill Hill. The only bump in the road where you can get airborne in a 50 mile radius.:D
    But...this Explorer has so much unnecessary crap installed that I would never have got it functioning comfortably without the Internet.
    Fully automatic 4 wheel drive (until I cut the wire to the transfer case). A rear view mirror that controls the headlights (until I pulled the wire out of the control module). An alarm system that goes off at random times (until I pulled that wire out of the control module). Ceiling lights that stay on forever (until I took the bulbs out). Ignition keys that cost over $100 (until I defeated that system). A chime that won't shut up until you buckle the seat belt and shut the door (until I unsoldered it). Sun visor lights that never go off (until I cut the wires).

    If I didn't consult the Internet, I would still be tracing wires.

    I haven't found a way to stop the written flat tire message, but I did paint over the blinking idiot light.;)
     
    Last edited: Jun 30, 2016
  11. Lestraveled

    Well-Known Member

    May 19, 2014
    1,957
    1,215
    I like your style.
     
    #12 likes this.
  12. #12

    Expert

    Nov 30, 2010
    16,338
    6,824
    As long as they aren't involved in an ignition interlock, I can defeat 'em.:p
     
    GopherT likes this.
  13. MrAl

    Thread Starter Well-Known Member

    Jun 17, 2014
    2,439
    492
    Hello,

    Thanks for the replies.
    For a quick rundown of how the orignial version worked or was supposed to work, each resistor under the fluid experiences a higher temperature so the resistance of the whole bunch increases. Any outside the fluid gets a lower temperature so the whole string is lower resistance. Dont know the difference in temperature between under the fluid and above the fluid level. The original version was for engine oil, but i was hoping to do trans fluid too.

    I'll reply in the order the replies were posted...


    #12:
    Well the original article used resistors, carbon type. I guess thermisitors might be better, i'd have to do some experiments i guess.

    Carl:
    Yes you're right, carbon was the original article choice.
    I am not sure about the difference in temperature. The difference would come from having some resistors emersed into the oil and some not emersed, that are just attached to the dip stick and just more or less hanging in air, but the air would still be inside the dipstick tube so i dont know.
    Yes, heating them might be better, i'd have to be very careful though, and not sure how heavy the wires could be running to these resistors. That's an idea worth considering though.

    Dodgydave:
    That etape looks interesting, i'll have to look more into that. First time i've seen it.

    Les:
    I am not really too worried about false readings because i would know when i was on a hill or whatever. As long as a get a reading. Also, on a hill would be a good way to actually test it to make sure it was still working.

    GopherT:
    Optical sounds very good. I just have to check if they make opticle sensors that can handle the high temperatures of the oil. I would guess it would get pretty hot.

    #12 (2nd):
    Well i thought it would be good to have an indication of level because that's a very expensive repair.
    I would have to keep up with the maintenance of the sensor and circuit of course, but it seems like a small price to pay.

    Les (2nd):
    I didnt know the tire pressure sensors were so bad. I thought about getting them with my last car, now i dont care anymore :)
    Any idea why they go bad?

    #12 (3rd):
    So how many pairs of cutting pliers have you been through in the last decade then? :)
    You dont get any 'check engine light' coming on?
     
  14. BobaMosfet

    Active Member

    Jul 1, 2009
    109
    11
    Registering oil level during operation is a folly. It's not like it's sitting there all level and placid. It's splashing around rather violently in the crankcase... just saying.
     
    shortbus likes this.
  15. Lestraveled

    Well-Known Member

    May 19, 2014
    1,957
    1,215
    Some of them use a battery which runs down. Others use wireless power induction which solves the battery issue. All of them are constantly subjected to huge g forces and shock. They will only last so long under these conditions.
     
    #12 likes this.
  16. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Oil PRESSURE is more important than the oil LEVEL. If your oil pressure drops below, say, 10 PSI while the engine is under load, you will wind up with severe engine damage in just a few moments, no matter what the level of the oil is.
     
    Lestraveled likes this.
  17. #12

    Expert

    Nov 30, 2010
    16,338
    6,824
    A major factor in defeating unnecessary, faulty, expensive, options is to avoid a, "Check Engine" idiot light.
    All my modifications have accomplished this.
    One I haven't fixed is that the fuel gauge sticks on, "empty" when the tank is very full, and that causes a Check Engine idiot light because a stuck fuel gauge is the same priority as low oil pressure or a dead spark for one cylinder. I'll try another can of Sea Foam brand fuel system cleaner. If that doesn't work, I'll cut through the floor, remove the fuel level sensor, and clean the sliding resistor contact. Meanwhile, I carry a cheap code scanner and reset the fuel level idiot light code as soon as I use a few gallons of fuel and the gauge resumes working.

    The flat tire sensor can not be eliminated because it is checked by the engine control software every time you start the engine. You can not disable it in software, so I opened the instrument cluster and painted over the idiot light with black paint on a Q-tip.

    ps, I'm on my third pair of wire cutters in 46 years. One got lost and one got ruined by a helper trying to cut steel with a copper cutting tool. Once you get that nick in the deep end of the cutter, it becomes very inconvenient to position the wire just right before every cut.
     
  18. MrAl

    Thread Starter Well-Known Member

    Jun 17, 2014
    2,439
    492
    Hi,

    Yes good point. I think having the level check is at least some protection for the transmission though.
     
  19. MrAl

    Thread Starter Well-Known Member

    Jun 17, 2014
    2,439
    492
    Hi,

    You could probably work out a solution where you just ask for a certain dollar amount of gas, so it dosent fill up all the way. That way you dont have to do anything except never fill it up all the way. Once you figure out how much to buy then you got it made :)
     
Loading...