It used to annoy me that my tomatoes would split due to a lack of water while i was at work, so i decided to build an automatic watering system so this could not happen! i wanted it to be solar powered so that i did not have to run cables from the house to the green house. the system has been working now for 2 summers (coming up for the third!) so its been proven. so here is my instructable of it! this is my first instructable so i hope its clear and detailed enough, if you have any questions or queries just let me know!
just thought I should add that I went on holiday for 2 weeks last year and the greenhouse looked after itself with no problems! apart from the weeds etc of course!
Step 1: Aquiring All the Parts
the first thing to do is to get all the parts you need, you will need the following components:
a water butt for the greenhouse (i have assumed you already have one)
12v Bilge pump (around £10) (if you didnt want to use a pump you could mount a water butt high up and use gravity to feed the system)
12v solenoid valve (£7)
12v programmable timer (£6.50)
12v solar panel (i used a 15w panel, it cost around £30)
12v solar charge controller (£6.60) (not essential but recommended)
12v battery (£10 each for a 7ah) (1 should be fine, however i used 2)
pipe work, fittings, hose clips, cable etc.
Step 2: Building the Pump Side
connect a length of hose to the pump and run it to the greenhouse and attach the solenoid valve to the end.after this, decide where you want the water to go and lay some perforated soaker hose, or simply cut/drill some small holes in some ordinary hose.
once you have done this attach both ends of the perforated hose to a t-piece pipe fitting and then attach the solenoid valve to the t-piece as well. you do need a solenoid valve really to ensure the system does not siphon from the water butt once the cycle has finished. another note, from my experience it is best to place the t-piece somewhere around the middle of the bed to ensure an even flow of water in each direction.
i think it is better to lay the hose around whatever you wish to grow and then lay more soil on top to ensure it does not evaporate during the day.
Step 3: Building the Electrical Side
first you need somewhere to store the battery/batteries (i think you could get away with just one, but i decided to use 2 as i added a small hose to my system as well). i made a small box out of some old pallets to keep the batteries dry, and to store them outside. i built a small roof which allows ventilation but stops rain from entering the enclosure.
then run a cable from the battery enclosure to wherever you wish to keep the electronics inside the greenhouse, i had an old electrical enclosure kicking around but you could use anything really, it doesn't even need to be enclosed it could just be mounted on a piece of wood! run the cable from the battery to the solar charge controller and connect it as shown in the diagram. (a charge controller is optional really, but for the price it worth it as it will ensure your battery/batteries as kept healthy by not letting them get too flat and not over charging them).
now mount the solar panel somewhere in lots of sun, i attached mine to a pole and mounted it to the water butt. run a cable from the panel to the charge controller and attach it to the solar panel terminals.
then attach some cables to the 'load' terminals on the solar charger and fit them to the programmable timer to the power connections. and finally from the output side of the timer to the pump and the solenoid valve.
now everything is wired up!
my panel looks a huge mess as i used 2 timers i already had and made up a timing circuit, however if you buy a normal 12v programmable timer there will be much less wiring and it will be MUCH neater! also if i did it again i would use smaller pipe for the pump.
Step 4: Programming the System
OK, now everything is connected up all you have to do is let the battery/batteries charge for a while, the charge controller will not allow you to use too much of the battery helping to keep the battery healthy.
so in the mean time plant some tomatoes/chillies/whatever you want and put some soil over the pipes, at least an inch or two i would say!
so once there is enough charge in the battery you can program the timer. set it to whatever you wish, my system usually waters for about 1 - 3 minutes every 3 - 4 hours depending on how hot it is as i change the settings to suit. hopefully you should find that the soil may look very dry on the surface but scratch down a bit and it will be lovely and moist! i hope this works for you!