Water Meter with integral 7 Day

2 event timer (ideal for sprinkling)

Solenoid switch (top) flow sensor bottom

How much water do you use to keep the garden fresh, and at what cost? 

This project will keep a tally of water usage in litres or US gallons and  the total cumulative cost. As a bonus it comes with a 7 day ,14 single event, timer for automatic sprinkler setting. An optional extra is a rain detector circuit that will not allow sprinkling if it is raining. 

The front panel status LED is green for standby, red = sprinkler active, and flashing = power outage has occured and the sprinkling event has been bypassed.

With proper safety precautions observed, this could even be pressed into service as a timed shower  controller. No more arguments as to who stayed too long in the shower!

The  project can be built in stages as either a water meter , a timer , or as here a combined water meter and timer.

The controller will measure up to 999.999Klt or gallons before it rolls over to zero, with a maximum currency display of ,$, 999.99, and a maximum unit cost of 9.99 in your favourite currency. The unit cost and totaliser amounts are stored in on board EEPROM. Provision is made for an external eeprom for data logging purposes, though this has not been implimented in software.

The most expensive part of this project is the flow sensor, the one used here is from RS Electronics, others can be used so long as they have a pulsed output and the pulses/ltr(glln) value is changed in the software. A DIY heat based flow sensor alternative is being investigated.

The Pic used in the protoype was a 16F873 and Timer1 is used in compare mode to count the pulses from the flow sensor. When the pulses/ltr match the compare value preloaded into Timer1 (1200 for the sensor used), the counter is reset and the litres variable is incremented by one.

The RTC uses the Bresenham style algorithm as used in the simple event timer, and therefore does not require an external crystal. It is quite likely that if one of the newer Pics are used that has an internal 4 - 10MHz oscillator, this project could be modified to use no external crystals or resonators at all.

The complete project file can be found in the downloads section which includes the C and hex code, schematic and double sided board layout in Eagle format, a front panel template (requires Front Panel Designer) and instructions on use.

A bare PCB can be purchased for 8.00 including P&P to most countries. A preprogrammed Pic 876 (state if US gallons version required) is also available for 5.00 email projects@btech-online.co.uk

Component layout 


Front panel


* Local laws on water and electrical safety should be checked if contemplating this option.  Water and electricity do not mix very well, and connecting to a shower should only be attempted by those constructors who are competant and or qualified in this area. 

This page copyright Colin Barnard 2004