Water Level Sensor

I'm using ATMEGA 328. What is the cheapest and easiest method to detect the water level? Condition: If the mini tank is empty,refill it by opening the main water tank.

Hi Attach a floating object to a switch, use whatever lever system to keep electricity out of the water :) That is if you are looking for a cheap solution. You can also make a floating ball in a tube (parallel to your tank and communicating with it a the bottom) interrupt a LED/Phototransistor couple once it reaches a certain level, to use as a trigger (absence of current triggers action). Then there probably are devices for pressure sensing and whatnot.

check this - http://mechanical.poly.edu/faculty/vkapila/ME3484/Readings/NV27-Measuring%20Water%20Level.pdf -

Not quite what you need, but I had to make something similar recently for an oil filtering system to use for filtering old cooking oil to reuse in a truck.

Since we needed to work out when the level was both full and empty, and also keep track of blockages (detect when the flow has slowed down), we used a ultrasonic range sensor, which can detect the level of oil up to 1 meter away. It's simple and easy, and needs no moving parts.

You could always just use a couple wires as your sensor. I've use that approach in several projects. It triggers when the water level drops below the ends of the wire pair. You could use multiple pairs at different points so you know different levels.

gabenix: You could always just use a couple wires as your sensor. I've use that approach in several projects. It triggers when the water level drops below the ends of the wire pair. You could use multiple pairs at different points so you know different levels.

might cause electrolyses and can draw quite some current (can be switched on e.g. once a minute for the time to take a measurement to minimize these two)

might cause electrolyses and can draw quite some current (can be switched on e.g. once a minute for the time to take a measurement to minimize these two)

Correct.. The current draw and corrosion from electrolysis will be nearly non-existent (negligible) when simply "pinging" a signal at timed intervals and checking for the response. It only takes about 100 microseconds (0.0001 s) to read an analog input. This is how I've always applied this technique.

Check this out https://www.sparkfun.com/products/10221

2007jingz: Check this out https://www.sparkfun.com/products/10221

Cool sensor, however I guess it does not meet the cheapest criteria of the OP (OriginalPoster) What is the [u]cheapest[/u] and easiest method to detect the water level?

the OP had two requirements.

1) cheapest

2) easiest

the two wires seems to meet both of those. the disadvantage is they are make/break readings. the level has to fall below the threshold before the signal to fill. also, a second sensor is required at the upper level to signal when to stop filling.

blowing way past the cheapest and also past the easiest, a capacitive sensor would offer a reading of tank level.

so, having to open the wallet and buy a Schmidt trigger and a resistor..... the costs would be orders of magnitude over that of just wires.

as for the easiest.... that too goes bye-bye. this will take time to make and calibrate.

http://soulysolar.mudventions.com/?p=681

aprilmay11111: Condition: If the mini tank is empty,refill it by opening the main water tank.

Sounds like on/off.

It depends on the size of the mini tank but there is a swag of different-size float+reed switches on eBay. Average price is about $1.