uxcellStainless Steel Float Switch for Water Pump Tank Swimming Pool Garden Pond Liquid Water Level Sensor M10 116mm Length

Works like it should.

They work. As they repeatedly warn you, they do not handle large loads - I used mine as a pulldown to an arduino pin and they are fine for that. They'd be fine for switching a 20mA LED, piezo buzzer or triggering a transistor, too. More than that and you're probably pushing your luck with the little magnetic reed switch inside. They claim you can drive a *small* relay with one - I wouldn't, personally. If you need that, a ULN2003 can drive the relay and this can drive the ULN2003; problem solved.Mine was NC with the float down. That's of no consequence when using them to trigger arduino inputs, since you decide what on and off mean in software. For some other applications you might need to install them upside down to get them to turn on when water is present and off otherwise.

Wish I bout one another inch or two longer but works like a dream. I use it to fill a 5 gallon jug for my bottom feed water dispenser. I use a water drop UF filter that only fills half gal a minute and with this part of my setup I can walk away safely and when the float rises quickly signals water shut off.

Not reliable: 400mA through contacts keeps it from opening when bulb lifts. Smaller sense current of 10mA through contacts is reliable. Added blocking diode + capacitor snubber across contacts and solenoid valve to prevent arcing to no avail. Resistance is still under 1 ohm when closed, so, again, as sensing with low current they work just fine.Don't use this to drive a heavy duty coil relay or solenoid directly. Only as an input to a solid state relay or micro controller. Otherwise, the switch won't open. I suspect it's a 300mA reed switch and they are saying it can be used for up to half an amp. But after 2 hours at 0.4A, it reliable does NOT open when float lifts. Purchased two of these and both have same issue.I now only use them to sense with small current to drive SSR and haven't had an issue.

I used this level together with a button battery and an LED to indicate when water levels in the tank of my Rancillio Silvia Espresso machine drop low. Works like a charm! No more aborted espresso draws and waste of precious beans.

bought 6 for a project did not work for us

Great

I was worried for a second bc it was showing a closed circuit with the float down, but removing the snap ring and flipping the float easily changed it to NO.