Water flow switch

For low flow setups, like to K40 tube cooling water, you really want a flow switch that disables the laser when the water isn't flowing. A visual indicator is fine but you may not be watching it all the time.

Flow switches are available online but don't operate at low flowrates (under 1 l/min) or cause a severe restriction that an aquarium pump can't overcome or will reduce the flowrate. Float switches are available online but don't indicate flow is happening.

Other flow switches use a paddle wheel and need to be powered for the detector that detects pulses.

This Thing uses a float to indicate that water is flowing by monitoring the level in a leaky bowl. When flow stops, the water level decreases as it leaks out and the flow switch (reed relay) opens.

This Thing is attached to the side of the cooling water container and water flows through it before spilling back into the main volume. It won't work on the inlet side of the flow system.

It needs no power or additional ci