Lawn Sprinkler Timer

[VegasMonkey]

I am trying to design a one time programmable lawn sprinkler controller to trigger on/off 24V 750ma lawn sprinkler valves. A set and forget sprinkler timer that once the time/date are set, it does the rest.

The project needs to allow for programming on/off time for 7 days per week during summer months and switch to a "winter" program during fall/winter months. Once the timer program is set, it will never change for the life of the sprinkler system (so I need a calendar of 10-20 years).

Any ideas on what ICs to start with to get the calendar, 24 hour timer, and triggers?

Has anyone done this already and willing to share circuit design?

Thanks

 

[ljcox]

Have you done a search in this forum for "water timer", "sprinkler system", etc.?
I think the subject has been raised before.

I intend to do one in a year or 2 (once I'm free of other jobs) using a PIC.

I may also include a burglar alarm and garage door opener.

 

[Mike - K8LH]

Would you also require calculated sunrise and sunset times based on location (lat/lon) data? How many individual 24v/750ma sprinkler valves, or, could the controller drive a single relay which would turn on/off all sprinkler valves? Program it via built-in push buttons and LCD display or via connection to a PC?

 

[mneary]

Typical sprinkler controllers only turn one valve on at a time. Not only does it save current but often the zones are configured so that there's only enough water flow for one zone at a time.

You don't need a calendar, you need a photocell. Winter is easily distinguished from summer (assuming a latitude where there's a difference) by the difference in the average daylight times. Similarly, since cloudy (and rainy) weather should influence the watering schedule, the photocell will also help this. If you need a schedule with a weekly synchronization (i.e. never water on Sundays) then divide by seven. A thermistor and/or humidity sensor might help with the watering algorithm.

User would select increase/decrease per zone to compensate for water requirements.

Chip suggestions: ATTiny15, ATmega48/88, LPC2101.