BMW uses a capacitive sensor for both oil condition & level (in the same pa=
ckage). I believe they digitize the analog reading and send it out to the E=
CM. A BMW factory manual should outline the waveforms.

-MK.

-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of=
 Bob Blick
Sent: Tuesday, February 17, 2015 1:27 PM
To: Microcontroller discussion list - Public.
Subject: Re: [EE] Sensing oil level

My RX-7 has an oil level sensor, but I've never had it out to see what make=
s it tick. But it only reports when the oil level is low, not multiple leve=
ls.

I've used these sensors for water level, don't know what the upper temperat=
ure limit for them is. They use a magnet and a reed switch:
http://www.ebay.com/itm/-/311231357646

Cheers, Bob

On Tue, Feb 17, 2015, at 09:39 AM, Neil wrote:
> I looking into making an oil-level sensor as a general indicator of=20
> oil level.  It does not need to be super accurate, and really just=20
> needs to indicate a minimum of 5 levels -- too low, low-side of=20
> normal, average normal, high normal, or too full.  Space for the=20
> sensor is tight -- approx 1" dia and about 6" to 8" deep.  I've found=20
> this page, which shows some general ways this is done...
> http://www.machinerylubrication.com/Read/23921/oil-level-sensors-autom
> otive-industrial
>=20
> What I'm thinking is a small donut-shaped float around a 6" tube, with=20
> magnets in the donut and reed or hall-effect sensors in the tube.  Or=20
> vice versa -- a tube with the sensors in the tube wall, and a magnetic=20
> ball floating in the center.  Any better (simpler) ideas?  Or anyone=20
> know if I can do this with some type of capacitive sensing?

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