Hi all,

I'm a struggling to do a project in less than 1 week for a charity and wondering if the www can help. I'm a complete electronics/Arduino beginner so please break any suggestions down, thanks!

The challenge:
I need a little water pump to run for 3 seconds with a 10 minute pause completely off the grid 24/7 from a battery. I need the battery to be charged using a solar panel and hold enough storage to run 2 days without sunlight. An Arduino is also needed to change the duration and interval of the pump.

What I know:

The pump requires ~12v @ ~270mA (5W)
and 64.8mAH (for 2 days of operation)
(pump runs for 18s per hour = 0.05h per hour
0.05h x 270mA = 1.35mAH
1.35 x 48hrs = 64.8mAH)

I also need to be able to take the battery on a flight so please recommend a suitable battery for the system (I was thinking maybe the Li-ion 18650? http://www.ebay.co.uk/itm/311727421481?_trksid=p2060353.m2749.l2649&ssPageName=STRK:MEBIDX:IT).

Pump: http://www.ebay.co.uk/itm/222223864810?_trksid=p2060353.m2749.l2649&ssPageName=STRK:MEBIDX:IT

What is the simplest way to wire & code everything up? (Please also recommend any required components)
Any help is much appreciated!

 

My first concern would be the solar panel. Choosing the size you need requires some guessing about the conditions versus your requirements. I mean, it's a different scenario if you want the device to never fail. If it can fail a time or two due to weather, your panel an be smaller. Maintaining the battery during the depths of winter in a cloudy location is very different than during summer in the desert. You can obviously oversize the panel, but you still need an estimate. I'd want a battery with at least double the nominal capacity that I need to run the pump.

Don't forget to add in the power requirements of your Arduino.

Whatever panel and battery you choose, you'll likely need a charge controller so that the battery is kept in peak form and not overcharged by the panel.

Your Arduino will not control the pump directly, so you'll need a transistor to switch the power to the pump. I'd use a MOSFET such as IRF540N (just because I have some on hand) but just about any MOSFET will work for your smallish pump. You may need a logic-level MOSFET to interface with the Arduino output. (Sorry, can't help you with anything Arduino.)

You'll want to wire a reverse-biased diode around the pump. This diverts the inductive spike that might occur when the motor is switched off. Without the diode, the spike can damage the transistor.

 

Your Arduino is going to consume 10-20 ma while running code, 10 X your pump power budget.