Moteino R5 and Analog Input for Pressure Transducer

[G550_Pilot]

I am working on my pool project and wanted to add a pressure transducer (http://www.ebay.com/itm/261260635816). It says that is requires 5V, has three leads (+5/- and data) and outputs 0.5V – 4.5V linear voltage output. 0 psi outputs 0.5V, 50 psi outputs 2.5V, 100 psi outputs 4.5V.

Is this something that I could read off one of the analog pins on the Moteino R5 or would I need something else like an MCP3008 to convert it to a digital signal?

Thanks!

[TomWS]

I am working on my pool project and wanted to add a pressure transducer (http://www.ebay.com/itm/261260635816). It says that is requires 5V, has three leads (+5/- and data) and outputs 0.5V – 4.5V linear voltage output. 0 psi outputs 0.5V, 50 psi outputs 2.5V, 100 psi outputs 4.5V.

Is this something that I could read off one of the analog pins on the Moteino R5 or would I need something else like an MCP3008 to convert it to a digital signal?

Thanks!

Greg, yes, you could read this with the Moteino analog input but you'll have to divide the voltage output unless you're VERY sure you'll not have a pressure that goes above 66PSI.  If you want to read full scale output then you'll need to divide to 0.66. 

The simplest method is to use resistor divider but, since there isn't a datasheet, it's not clear what the output resistance is and any resistor will load it.   It is probably safe to work with something >10K so something like 5.1K & 10K gives a reasonably close value (0.66225) without overloading the transducer.  You're going to have to offset and scale the value anyway so you can factor in the slight error into your math.  Don't go too much higher than this however.  The Honeywell PX2 series looks similar to this and has a 2K minimum resistance load specification.

Tom
BTW, be SURE to get the cable/connector as well.  Finding a matching connector for this transducer is a bear!  DAMHIKT!

[G550_Pilot]

Hi Tom -

Thanks for the info. If you don't mind me asking, why would I need to worry about the pressure going above 66PSI? Is this due to a limit on the voltage that can be applied to the analog input on the Moteino ie ~3V?

The max pressure on the stock analog gauge supplied with the filter system is 60PSI, in addition my pool intellipump has a max cutout set at 50PSI that will shut the pump down if I exceed that amount with a "clean filter" message.

So I doubt I would ever go above the 66PSI and if I did, I would have worse problems then a analog pin on the $14 mote!

And I did get the connector, and your right...it looks like it would have been a bear to make work without it!

Thanks Again -

Richard