Credit goes to Greig Dempster for the excellent Arduino Plugin for the Homeseer. I’m using an Arduino Mega, with the pressure sensors feeding the analogue inputs. Greg’s plugin creates a device with the resulting AD count.

Been on the lookout for good value pressure sensors for quite a while now and finally found these:

http://www.ebay.co.uk/itm/181110950113

This 80 psi device gives a linear output between 0.5v and 4.5v for the pressure. I subtract 0.5v from 4.5v to get a 4 volt swing for the full range. I divide 4 volts by 80psi to get 0.05 volts per PSI.

5 volts on the Analogue input gives a count of 1023, so I divide 5 by 1023 to get 0.0048 volts per AD count.

I subtract the 0.5v offset from the reading to account for the fact that 0psi on the sensor gives out 0.5v (an ADC count of approx. 100)

They come with a 1/8npt thread, a quick rummage around in my fittings box got it working quickly, then I ordered the correct tap and made a brass fitting on the lathe for it.

Changed the settings for the Analogue device as shown in the pictures so I end up with the raw ADC count for the value. I then created a new virtual device that would receive the water pressure that's calculated from the following script:

Public Sub Main(ByVal Parms As Object)

Dim adc As Double = hs.DeviceValue(338) 'Get the ADC count using the device reference ID

Dim psi As Single

psi = (adc * (5 / 1023) - 0.5) / (4 / 80)

' hs.WriteLog("AD Count=", adc)

' hs.WriteLog("Water pressure PSI=", psi)

hs.SetDeviceValueByRef(339, Math.Round(psi, 0), True) 'Update Virtual Device ID 339 with the calculated pressure

End Sub

On the left is the quick mockup and the right is my custom brass fitting that I made:

You need to modify the homeseer device that the plugin creates to provide the actual ADC count for the device, as the script does all the maths:

Hs.devicevlaue(338) is the ADC count from the device created by the Arduino plug.

I created a new virtual device in Homeseer and called it “water pressure”. It’s device refernce ID is 339, this line then updates that virtual device with the calculated water pressure:

hs.SetDeviceValueByRef(339, Math.Round(psi, 0), True) updates a new virtual

Here’s the event that triggers when the ADC count changes and updates the virtual device with the pressure:

At the moment the event cant retrigger for 5 seconds, but I will probably increase that to 60 seconds once things have settled in. The reason for this is just to keep the CPU load low, as I dont need it performing real-time updates of the pressure.

I use Jon00 graphing tool to track the pressure over 30 days: