Controlling 24 VDC pump with a float switch

Thread Starter

Rayan Perera

Joined Nov 2, 2020

I'm a beginner in the electronics field. Can someone help me advising how to control 24 VDC water pump controlled with level switch (also VDC) with 230 VAC?

Thanks in advance!


Joined Jun 22, 2012
Are you wanting to detect minimum water in the tank and maximum too, or just maximum?

What current will the pump take?


Joined Apr 4, 2016
Normally you need two float switches. One to start, one to stop.
If it's water you can get conductive devices with usually 3 probes. 2 long, 1 short. cut to length for the start and stop levels.

For example: Probes like this and using a controller like this.

If it's a non-conductive liquid, such as oil, then float switches or ultrasonic sensors are needed.


Joined Sep 17, 2013
You will need a power supply which converts 230VAC to 24VDC, can cope with the start-up current of the pump (which could be several times the normal running current), and provides isolation from mains voltage for safety.
Conductive probes for level sensing won't work in pure water, so you do need at least one float-switch.

Thread Starter

Rayan Perera

Joined Nov 2, 2020
Hello, thank you, everyone, for your replies!
Here's a rough scheme of my setup. I have two pumps and one level switch. Additionally I have an Arduino uno as well. I need to control P-2 (refering the scheme) just ON/OFF according to the level signal. WhatsApp Image 2020-11-02 at 15.04.20.jpeg


Joined Sep 24, 2015
Welcome to AAC.

We ask for more information because there are likely so many different possible solutions which depend on the equipment you want to control and how you are able to control it. In this case a simple switch setup will not need an Arduino or any other micro controller. You also mention two different voltages. This also must be cleared up. From your drawing it would SEEM you have a 230VAC source of power and you want to run (a) 24VDC pump(s). One answer doesn't fit all situations.

I've seen a rod with a float and two settable rings that can be adjusted to different heights. When the float rises it flips on a light switch, which can easily control 24VDC as well as 230VAC. As the water level falls the switch is flipped off, shutting the pump off.

Making assumptions here, but I'm guessing the second pump (controlled by the float) pumps water out faster than it can come in. If that's not the case then you need a float valve to limit the incoming water. Again, we need more information and a detailed explanation of what you want to accomplish. I know it seems like you've given us sufficient information, however, we still need more detail. Power supply for the 24V; how much amperage it can carry. Pump motor start and run amperages as well. How much difference in water height may also be important as well.

If you only want to drain a tank there's a device called a Bell Syphon. Have a click on the bold lettering to see a video of that.


Joined Oct 7, 2019
This is what I am using. The end of the cord floats on the water. The cord is tied to the wall of the tank. Length of the cord and the position sets the on and off points. It is designed for 110vac 10A but I think it will work at DC. (you have 24V at 1/2 amp) Cut the end off the cord for DC. "sump pump switch" There are many types but this one works well and lasted 20 years and counting.


Joined Sep 17, 2013
With only a single simple float-switch there is a risk that the outlet pump will be repeatedly switching on and off rapidly, which may not be good for the pump or the power supply. Ideally you want some 'hysteresis' in the system, such that the float levels at which the switch changes state are well spaced vertically.