PCB sensor advice for PICAXE

I

itolond

New Member
Dear Forum,

I seek a pressure (water) sensor which will work with picaxe. Application is reasonably strait forward:

  • Submersible (or at least the sensor)
  • 0-5m water depth
  • small as possible
  • low voltage


calculating the depth via bottom distance will not work in my application, however measuring from the surface would.

any guides would be appreciated


regards,

Ian
 
W

westaust55

Moderator
Is the water vessel elevated?
Do you have access to underside or bottom edge for a pressure sensor?
What is the application ?
Do you just need to know if full or empty or need continuous analog level measurement?

What is your budget or upper price limit?

Any indication available on what is "small"?

What accuracy and resolution are you seeking?

What is you "low voltage"?
In my line of work that is > 50Vac (and 120 Vdc) up to 1000 Vac
Below that is extra low voltage. (refers AS/NZS 3000 )
see also:http://en.wikipedia.org/wiki/Low_voltage

It all gets a bit relative to what one is familiar with. In industry a lot of control equipment is rated for 24 Vdc.

More information will result in better suggestions.
 
Last edited:
I

itolond

New Member
thanks for the replies,

its for a model submarine, so the environment will be variable, i can only say pressure or distance from surface are references. Small in terms of power draw and size, how small is a good question, however the smaller the better.
 
W

westaust55

Moderator
If the inside of the model submarine remains nominally at atmospheric pressure then you could use a differential pressure sensor.

It would need to be open to the interior of the model submarine and the other would need to be open to the water via a port in the hull of the sub.
The sensor needs to be specified to allow contact with water (and typically only more expensive ones are).
You will also need to zero the sensor prior to each dive unless you can balance the interior of the submersible with the current barometric pressure.

Knowing how deep you'll be diving (5 metres) so you need a range of approximately 10 Kpa or 1 psi per metre of depth.

The MPXM2101 can handle 100 kPa with a safety margin of 2 (200 kPA absolute max) and requires a 16 Volt supply.
http://pdf1.alldatasheet.com/datasheet-pdf/view/99846/MOTOROLA/MPXM2102A.html
I have not used on of these so some research by yourself would be required.
Output is 41.5 mV full scale so you will need an op-amp to generate a larger voltage that the PICAXE can monitor with any resolution.
 
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