How to slow down a float switch cycle?

[Armando]

I replaced a Maxijet 1200 I use for topoff with a peristaltic pump (Aqualifter), which pumps very s-l-o-w.

For this or other reason (there isn't turbulence), the float switch in the sump turns on and off constantly. The clicking noise is really annoying. Could also end up damaging the pump.

I was wondering if there is a way of putting some "tolerance" in the float switch. So it would wait a while before it turns on or off.

 

[denvig]

What brand/model is the switch?

 

[Armando]

it's the Ultralife float switch

 

[NateHanson]

Put a piece of PVC around the float (open top and bottom, but no holes around the side) and maybe it will prevent the switch from being opened and closed by little ripples in the sump. Just a thought. Not sure if it will work.

Nate

 

[denvig]

"This 'reed style' 'Float Switch' will operate in both high-water and low-water applications. The design allows for simply turning over the barrel float to change how it performs. The switch can handle multiple pumps with a combined amperage draw of up to 10 amps. Each switch is equipped with a 6 ft grounded cord and and adjustable suction cup mount for the switch. They are excellent for water top offs or to prevent pump damage from sumps running dry. Very accurate, within 1/8 inch."


1/8? isn?t much but if the water isn't turbulent it should stay off for some time to allow for the 1/8? evaporation. It sounds like you have a very sensitive switch and they don?t look like they are adjustable.

 

[Jim Tansey]

Armondo,

I don't know why this question does not come up more often the way most people install float switches they should cycle on/off at the switch point continuously even when used in a dual high/low setup. The way most switch points are designed in electronic equipment a deadband is used to prevent this rapid cycling, it would work like this to fill a tub the switch would turn off for example at 20 inches and on at 15 inches in between 15 and 20 the switch will not function so small movements in the arm will not cycle the switch.

To do this electronically with a comparitor circuit is not a difficult task for a engineer, I am on my way to NY for a couple of days but maybe some EE could add to this discussion and we could build a little circuit with an adjustable deadband and relay to switch the pump.

Jim

 

[NateHanson]

Or you can use a latching relay. A couple people have built this sort of a setup with a 12V latching relay controlled by a low "on" switch and a high "off" switch. Works for either a solenoid (gravity feed) or a switched outlet (for a pumped top-off system)

 

[Armando]

Nate/Jim, interesting, but i dunno how do i build this relay. Can it be hooked up to the UL float switch?

 

[NateHanson]

There was a thread about building one in the DIY forum a while ago. Do a search for Latching Relay, and I'll bet you can find it.

Basically you need a relay and two $6 float switches. The wiring is simple, and explained in that thread. I think the relays cost about $20.

Nate