water-meter-hardware.rst

Water Meter Camera Hardware Details

The water meter sits in a below ground box, inline with the water main that brings water to the house and farm. The box cover is removable and has a small "viewing door" that is lifted to see the meter when the utility comes by for regular readings. Since the cover and the meter are already in place, aiming a small Raspbery Pi camera at the water meter is much simpler than getting construction and plumbing permits, doing major construction to dig up the supply line pipe and then cutting the pipe to install an in-line digital water meter.

Here is what the water meter box lid looks like, with a Mason jar lid positioned where the Raspberry Pi will go:

To develop and test a prototype, I placed a Raspberry Pi, a PiCamera and a flashlight in the meter box (below the lid). I learned that any single point light source created a lot of glare and light flares on the water meter glass face. So I built an array of 24 white LED's on a two prototyping circuit boards. The LED's are controlled using RPi GPIO pin 18 and an N-channel MOSFET to control the higher current flow to the LED arrays. The LED array draws too much current to be controlled by the RPi GPIO pins directly. The MOSFET circuit wiring prototype looks like this:

The LED arrays and camera are arranged on the underside of the water meter box cover:

A plastic Mason jar lid is bolted to the top of the water meter box cover. Holes are drilled through lid and the cover to allow the LED control wires and the PiCamera ribbon cable to pass through. The 5V power cable for the RPi is passed out in the space between the Mason jar lid and the box cover.

Finally, the Raspberry Pi and the MOSFET circuit are placed in a glass Mason jar that is screwed onto the lid. The final arrangement looks like this:

This arrangement has been working on our main water line water meter for about 2 years with very high reliability. The power cable is the only physical connection; all the images are sent via WiFi. The LED's are controlled by the imagenode software. Here is the imagenode.yaml file for the Water Meter, which shows the settings for the LEDs on GPIO pin 18:

# Settings file imagenode.yaml for the Water Meter RPi
---
node:
  name: WaterMeter
  print_settings: False
  patience: 30
  send_threading: True
  stall_watcher: True
  heartbeat: 5
hub_address:
  # Edit the line below to point to hub
  # H1: tcp://jeff-macbook:5555
  # H1: tcp://jeff-thinkpad:5555
  H1: tcp://192.168.86.70:5555
cameras:
  P1:
    resolution: (320, 240)
    framerate: 16
    vflip: True   # change to True or False to suit your RPi PiCamera
    exposure_mode: night
    detectors:
      motion:
        ROI: (45,58),(69,79)
        draw_roi: ((255,0,0),1)
        send_frames:  detected event # continuous or none or detected event
        send_count: 3
        delta_threshold: 3
        min_motion_frames: 3
        min_still_frames: 5
        min_area: 2  # minimum area of motion as percent of ROI
        blur_kernel_size:  7 # Guassian Blur kernel size
        send_test_images: False
lights:
  L1:
    name: floodlight
    gpio: 18
    on: continuous

For more details about the settings in the imagenode.yaml file, see the imagenode project documentation.

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