Working on a pressure measuring system (up to 50 psi). So far, the pressure sensors I've looked at are all too expensive for a small class project (in excess of $100 or almost Rs. 5000, which is the total budget we've been given). Does any one know of cheaper alternatives.

Something similar to this, hopefully:

ST1510

http://pdf1.alldatasheet.com/datasheet-pdf/view/145477/ETC/ST1510.html

 

I am not sure if you can get something like this unit http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=480-2521-ND, but this is less than $30.00 US....

Or you can create your own using a piezo "speaker" like the ones found in musical greeting cards, the piezo it will output a voltage proportional to the pressure applied to it...... search google for piezo sensors/transducers circuits


Wikipedia says:

A piezoelectric sensor is a device that uses the piezoelectric effect to measure pressure, acceleration, strain or force by converting them to an electrical signal.

here is a circuit I use to buffer the output of the piezo for use in 5 volt TTL circuits, D1-D2 prevent the output voltage from going over 5 volts....

B. Morse

 

Hello,

On this page of the EDUCYPEDIA you will find links with a lot of information on pressure sensors:
http://www.educypedia.be/electronics/sensorspres.htm

Bertus

 

You can always find someone ready to rip you off on a pressure sensor.

An oil pressure sender from any car that has a gauge on the dashboard will be in the range you want; and can be $0 at the wreckyard. Cheaper and simpler I do not know.

 

Just tried a piece of conductive foam for pressure vs resistance, the kind CMOS chips are stored in. Some was conductive, some was not. Used 1 " X 1" between two metal plates. No pressure = 200k ohms, gradually increased pressure up to 50+- lb =300 ohms. Cheap enough?

 

Just tried a piece of conductive foam for pressure vs resistance, the kind CMOS chips are stored in. Some was conductive, some was not. Used 1 " X 1" between two metal plates. No pressure = 200k ohms, gradually increased pressure up to 50+- lb =300 ohms. Cheap enough?

Ummm.. no. My time is worth too much to make that affordable.

Can you ship it to me?

Were the results repeatable? I was wondering if the foam had lost any sensitivity regarding the sensor viability after the first test.

Did the foam seem to return to the initial 200k ohm point after pressure was released?

 

I actually use those kind of homemade pressure sensors for my robotics projects....

B. Morse

 

So it works well?

 

for the most part it does, but it does tend to loose resistance in time.....

The piezo disc sensors on the other hand, have worked for pressure sensors, touch sensor, shock, vibration, etc.... and they are very versatile and can be used in a variety of applications....

I recently just used a hand full of them to make a set of electronic drum triggers for my MIDI drum set

You can check out the work log here >> http://www.morse-code.com/id208.htm


B. Morse

 

Have a look for a digital tyre pressure gauge.

You may well find one at a reasonable price & the sensor should be fine for 0 - 50psi.