How to add a water pressure sensor to EmonPi2?

Hardware emonPi
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Hi, I’ve recently had an issue with the UFH circuit leaking. I would like to add a pressure sensor to the system so I can monitor the pressure. Ideally also setup some sort of alarm or notification if the pressure drops below, say 1bar.

I have an EmonPi2, it has spare connections for temperature sensors, and CT sensor inputs. But I have not been able to find a compatible water pressure sensor. I have been looking for one like the temperature sensor DS18B20 that has a built in 12bit ADC. Maybe i’m making things more difficult than needs be. Any suggestions would be appreciated.

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You do of course have an analogue input on your emonPi2, which makes 3.3 V d.c. available to power a sensor and accepts a 0 – 1.024 V input from the sensor.

Some information here emonPi2 User Guide — OpenEnergyMonitor 0.0.1 documentation
and GitHub - openenergymonitor/emonLibDB: AVR-DB Continuous monitoring library: 3 voltage channels and 12 current/power/energy channels

RS list a range of pressure sensors, unfortunately maybe not at “realistic” prices.

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What heating system do you have? Sometimes it’s possible to read the system pressure e.g via modbus, ebus, HTTP or cloud API.

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I bought a couple of modbus sensors from Germany which I read with a RPi and post to emoncms via MQTT.

The Python I wrote will also email me if the pressure drops below a certain threshold.

I’ll try and dig out the part number/supplier.

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Thank you for your reply. It would be brilliant if it was possible to get the pressure from a sensor already built into the HP. The heat pump is a Mastertherm AQ30i, there isn’t anything else in the system that would have a sensor. I know they are not one of the well known ones so I’ll contact the manufacture for more information.

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This sounds like a good way to go if I can’t get the info from the HP. I’m not hopeful I will be able so if you can dig out the sensor info that would be great.

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Having said I got the transducer from Germany, it might have been somewhere else.

I’ve got a GS07381-03 - the 03 I think is important as it signifies the pressure range. This one measures up to 80psi and outputs 0.5 to 4.5V DC.

So it doesn’t use modbus. I run the output to an ADC Pi hat from AB Electonics and use the Python library they supply with my own code to send the data to emoncms.

I can post the code here if you decide to go down this route. Works really well and the pressure measured is accurate when compared to the gauge on the fill loop.