Electronics and water don't usually mix - which is why liquid level sensing projects can be a little challenging. You can DIY a sensor but keeping it clean and un-oxidized can be a pain. The Optomax Digital liquid level switches are a clever solution for when you need a small sensor to detect liquid/water: super easy to use and very durable too!

Inside the plastic sensor casing is an infrared (IR) LED and matching photo transistor. When in the open air, the IR light bounces back to the sensor so you know its nice and dry. When the sensing tip is immersed in liquid, the IR light escapes, and the transistor turns off. The sensor can detect the presence or absence of almost any liquid type; oil or water based. It is insensitive to ambient light and is not affected by foam when in air or by small bubbles when in liquid.

The microcontroller-friendly logic level output is push-pull type, and can sink and source up to 100mA at a supply voltage range of 4.5 to 15.4VDC - so you can even use it to directly control a transistor or perhaps even a small relay.

Simply connect the Blue/Black wire to ground, the Red wire to 4.5-15.4VDC and look at the output with your multimeter or microcontroller. When dry the output is the same as the red wire. When wet, the output is 0V. Note they're pretty sensitive, any liquid on the sensor (e.g. droplets on the surface) can trigger it.

Comes in a chemically resistant Polysulfone housing material – the standard choice for most applications – for external sensor mounting and for use in standard operating temperature ranges (-25 to 80°C).

Features:

Reverse polarity, ESD and transient over-voltage protected

Wide supply voltage range

Push-pull output, capable of sinking or sourcing up to 100mA, can directly drive small loads

Solid state, fully enclosed, so no moving parts to cause unreliability

Small in size so they can be installed in applications where space is limited

Can detect tiny amounts of liquid when positioned correctly, ideal for leak detection

Fast response time

Repeatable switching point

Built-in output delays available on request for applications where sloshing causes intermittent switching

Very robust permitting use in a wide range of fluids and chemicals

See datasheet in Technical Details for more specs and info! 

Measure liquid/water flow for your solar, computer cooling, or gardening project using this handy basic flow meter. This sensor sit in line with your water line, and uses a pinwheel sensor to measure how much liquid has moved through it. The pinwheel has a little magnet attached, and there's a hall effect magnetic sensor on the other side of the plastic tube that can measure how many spins the pinwheel has made through the plastic wall. This method allows the sensor to stay safe and dry.The sensor comes with three wires: red (5-24VDC power), black (ground) and yellow (Hall effect pulse output). By counting the pulses from the output of the sensor, you can easily track fluid movement: each pulse is approximately 2.25 milliliters. Note this isn't a precision sensor, and the pulse rate does vary a bit depending on the flow rate, fluid pressure and sensor orientation. It will need careful calibration if better than 10% precision is required. However, its great for basic measurement tasks!We have an example Arduino sketch that can be used to quickly test the sensor - it will calculate the approximate quantity of fluid in liters and display on an LCD or the serial monitor.