I need a solution to automatically turn on and off a pump based on a water level on a tank. problem is, the tank and pump has quite a distance, they are pipe connected but running wire between them is kind of impossible.
Is it possible to use Arduino to achieve this. maybe, having two Arduino boards each with a wireless shield, and somehow connect one boards to the sensor and the other to the relay.
It occurs to me that the device that turn on or off the pump, doesn't really have to send any information back. So if you kept that as a fairly dumb device, it could sit and wait for orders to either turn on or turn off the pump. Maybe even with a fail safe that if it hasn't heard anything within a pre-set time frame, it will make sure that the pump is off anyhow.
In the mean time the device at the tank could monitor the tank level and send signals to the pump controller as and when required. Under these conditions you could have just a RF sender (for the tank end) and an RF receiver (for the pump end). This comes in even cheaper.
For measuring the level in the tank there are LOADS of possible solutions. A simple float switch, a wet/dry sensor (basically a piece of PCB with parallel tracks) and I've even seen someone using an ultrasonic transducer (to measure the distance to the water level).
Whichever way you go, the programming should only take a few minutes.
I don't think those basic / cheap 433Mhz devices are going to have the range that is required
You could probably attach them to a home made yagi antenna, but I'd be a bit concerned about overloading the receiver with other signals, as they are really cheap and only have a very very basic receiver
I suspect that the OP would be better off using a FM transmitter ./ receiver combo or may be forced to use an expensive XBee solution with proprietary antenna to get the sort of range they are looking for
Personally I'd attach whatever transmitter / receiver module used (e.g 433mhz FM ) to a directional antenna like this one
They are for the ham radio 70cm band which is basically the same frequency and will give loads of gain and also directionality so that there would be less interference
For a setup like that where good comms is a relatively critical need I would use two of the XBee units operating at 900 MHz with a wire antenna on the module. I am assuming the range is line of sight, if not you could use additional XBee units to hop around obstructions. The XBee can be had for less than $40 and with Faludin's book as a design aid this is not a hard problem.