Sizing accumulator power to run el. solenoid valve

[miloskukoljac]

I want to build el. circuit : arduino, relay, el solenoid valve 12 V ( app. 5 W) for watering garden at my village house.

There is not installed electricity.

Also is needed accumulator to power stated circuit. Please help me by suggesting what is the optimal accumulator capacity ( Ah)?

I would load accumulator once per 2 months.

Or is there any better option ? Goal is the lowest investment.

Solenoid valve (https://www.dx.com/p/electric-solen...mally-closed-golden-white-246864#.VrZ2M08hMp4) has to run app. 1,5 h per week.

 

[cowboybob]

Also is needed accumulator to power stated circuit.

Welcome to ETO, miloskukoljac!

By accumulator, do you mean simply a battery, or a solar panel or both?

Or do you mean something else?

 

[miloskukoljac]

Thanks for welcome.
I mean battery. It could be charged by taking it to my home and connecting it to the el. grid , or as other option it could be loaded with solar panel.

 

[Les Jones]

I think for this situation one of the ready made waterering timers would be a better solution. I have one that runs on a single PP3 battery for most of the summer. It is not quite as versatile as a home made one using a solenoid valve and plug in digital timer as it is limited to a number of fixed watering programs. The one I have is an earlier version of this one.
**broken link removed**
There are many different types so one of the others may suit your needs better. If I was building one using a solenoid valve and 12 volt rechargable battery I would consider modifying a mains timer to run from 12 volts. The backup battery they use is a tiny nimh button cell which keeps them going for several months. This would cost less than the LCD display required with a microcontroller.

Les.

 

[alec_t]

(5W/12V) x 1.5H x 8 =5 AH per 2 months. So a battery with a capacity of, say, 10AH (you don't want to flatten it completely) should do.

 

[Les Jones]

Hi Alec,
Dont forget the power taken by the arduino. I have just measured the current taken by my arduino uno. It is about 50 mA So 0.05 x 24 x 60 (Days) = 72 AH. With the ATmega328P removed from the board it still consumes about 30 mA. So even if the code was written to keep the cpu in sleep mode for most of the time quite a large battery would be required. This could be reduced by building the microcontroller onto a board with only the components required for the timer function.

Les.

 

[alec_t]

Dont forget the power taken by the arduino.

Oops! I had forgotten it. I'm not an Arduino person (more used to PICs which can sleep most of the time on very little power).

 

[Les Jones]

Like you I have mostly used PICs but I have started using Atmel micros. (Mostly the ATtiny4313) I have never needed to use any of the sleep modes. I have just had a look at the data sheet for the ATtiny 4313 and the ATMega328P (The chip used on the Arduino uno.) Both have sleep modes. Although I have an Arduino I do not use it much as it is aimed at being programmed in "C" and I am very poor at programming in "C" I am much more at home with assembler. The Arduino uno uses an ATMega16 as a USB to serial converter and I don't think there is a way to prevent this consuming power. (Other than cutting tracks.)

Les.

 

[miloskukoljac]

Hello All
Thank you all for usefull info
I decided to order some water timer from aliexpress for less than 20 usd It is amasing how arduino is high energy consumer