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Topic: Car oil/water pressure sensors (Read 3851 times) previous topic - next topic

pgmartin

Jan 12, 2012, 03:24 pm Last Edit: Jan 12, 2012, 03:36 pm by pgmartin Reason: 1
I'm working on a garden-bot project, and one of the problems I have, is that water pressure, from the water lines, changes considerable during the day. Since I don't want to use an additional pump, I was looking for a cheap water pressure sensor.
I found that the water sensor I can get in electronics stores (like the ones from Motorola or Freescale) are quite expensive. On the other hand, there are oil and water pressure sensor for cars that cost just a fraction (at least around here, about 1/8 of the price). Trouble is, is not easy to get a datasheet for this car sensors.
Since I'm just looking for an input of "high pressure" vs "low pressure" thought that these devices can come handy. Doing some research, I found that oil pressure sensors in cars have a digital output (just yes or no  :smiley-mr-green: ) and have a threshold of 0.3 to 0.5 bar, which seems enough for my needs.

Does anyone have experience using this devices? I'm not proficient in auto mechanics, so I don't know what the usual pressure they measure is, or if oil sensors can work with water too?

Regards

robtillaart

just a warning : Car electronics is often 12Volt oriented, and the standard Arduino cannot handle that well ....

Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

kerimil

I've been looking for exactly the same thing as you are... and I got exacctly the same results - it's almost impossible to find datasheets and many products labeled as 'pressure sensors' are in fact pressure switches... I hope you understand the difference between pressure switches and pressure sensors/transducers ??


Anyway... why do you really need a sensor ?? I assume you want to implement a system that keeps the valve/valves open longer when the pressure is lower, right ?? Well have fun calculating flow as a function of pressure ;-)

If you think that challanging stuff is cool go for it... but personally I'd just get a pressure reducing valve to keep the pressure more or less constant



tytower

Oil switches are devices that connect to ground if the pressure drops below 5 lbs /sq ft.
Oil sensors look the same but change resistance with pressure so high pressure is low resistance . Look for cars  in the wreckers or manuals that have an oil pressure gauge but no plastic line to the back of the gauge.Those will have an electronic pressure sensor.

Both of these will work with oil or water or any liquid under pressure
Governments should do what they were designed to do only.
Manage the larger issues best done by Government.
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pgmartin

Thanks tytower for your answers!

Actually, I was looking for pressure switches (thast was lost in the translation) ;)
A pressure sensor will be even better.

I need a sensor, because if there is not enough water pressure in the line, the sprinklers won´t reach as far as I need, and just will flood their surroundings. So, I just need a pressure switch to decide if I can do the task, or wait till pressure gets better (usually later in the night here).

kerimil

well then you should be able to find pressure switches with no problem... they are usually fairly cheap too

If by any chance you can't then you might as well build your own pressure switch... it's not that difficult you just need a spring loaded piston and a typical switch

if you don't know what a spring loaded piston is....
see this
you need to build a device that will have a piston held in one position by a spring... the piston moves when as the pressure increases.... when a set pressure is reached the piston actuates the switch and closes the circuit... as soon as the pressure drops the piston retracts to the original position because of the spring


jdpp44

Hi,
Perhaps am i late, but i am new on arduino's forum (just beginner), but i have been interested by your topic
An answer could be in the wasing machines : you have a mechanic pressure detector inside (quite simple)
I have no shot under the hand, but i think i can find one in my stuff
Don't take in your wm (your wife could not be happy  :D), there is plenty of washing machines in trash
Jacques
just keep it, it can be useful one day ...

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