Tank Level control & Drain valve closure

[dan]

Hi Ben,

It has been a while.
I wanted to let you know about some progress I have made with the tank level plugin.
I have re-written the code for the ultrasonic distance sensor using the pigpio library.
http://abyz.me.uk/rpi/pigpio/

The library is included with the latest full versions of Raspbian OS. If you are using the light version you can install it with:

Code:

sudo apt-get update
sudo apt-get install pigpio python-pigpio python3-pigpio

and enable it to start at boot up with:

Code:

sudo systemctl enable pigpiod
sudo reboot

The new version of the ultrasonic code is much more accurate than the original and has fewer lines of code. The pigpio
library uses a C program running in the background and does timing in micro seconds.
Here is some output from the new code without averaging multiple measurements:

155.2
155.3
155.2
155.2
155.2
155.2
155.2


If you get a chance, try it out and let me know what you think:

Code:

#!/usr/bin/python

from __future__ import print_function, division
import pigpio
from time import sleep

pi = pigpio.pi()

# Define GPIO pins to use on Pi (BMC numbering)
pin_trigger = 23
pin_echo = 24

start = None
distance = None

# Speed of sound in cm/ms at temperature (changed from cm/s)
temperature = 24
sound_speed = 33.1 + (0.0006*temperature)

#  Set pin modes and output level
pi.set_mode(pin_trigger, pigpio.OUTPUT)
pi.write(pin_trigger, 0)
pi.set_mode(pin_echo, pigpio.INPUT)

def calc(gpio, level, tick):
   """
   Callback function to handle distance calculation.
   """
   global start, distance
   if level == 1: #  Start of echo pulse
       start = tick
   if start and level == 0: #  If start has a value and echo pulse ended
      echo = pigpio.tickDiff(start, tick) # Length of echo pulse in microseconds
      distance = round(((echo / 1000) * sound_speed)/2, 1)
      print(distance)
      start = None

def measure():
   """
   Send a pulse and time the echo.
   """
   pi.gpio_trigger(pin_trigger, 10, 1) #  Send a 10 microsecond pulse on the trigger pin
   cb = pi.callback(pin_echo, pigpio.EITHER_EDGE, calc) #  catch the echo and pass timing to calc callback function

while True:
   measure()
   sleep(1)

I will be working on the plugin over the next few days. The rainy season has started here and I have time for coding.

Dan