Simple Sump Pump Controller
Simple Sump Pump Controller
Put together a sump pump controller with two float switches and NO electronics
water | electric circuit | electronicsHaving a reliable system to pump out a
sump pit is essential as mistakes and failures can lead to serious flooding and enormous expense. In our article
Sump Pump Control System we introduced a selection of
electronic solutions to the following problems:
1) Identifying when the sump pit is full and automatically turning on the pump.
2) Stopping the pump before the sump pit is empty so that the pump stays submerged (increasing its lifetime) and it
never runs dry.
3) Not letting the pump turn on and off repeatedly (
multiswitching) or excessively frequently.
One common comment from some of our site visitors is that they have very limited
electronics knowledge and no
soldering experience - therefore our sample circuit designs are no practical use to them. What they really want is a system which is foolproof to put together, requires no special tools or experience, and is easy to troubleshoot and maintain. In this article we will present a new
sump pump control system which is economical and simple to build, very reliable, has few component parts, no electronics, and is easy to maintain.
Sump Pump Control System Design
The system illustrated above is designed to work as follows: There are two
float switches, one fixed high in the sump, and one positioned just above the height of the pump's water intake near the bottom of the sump. The upper float switch turns on the
pump when the water reaches the high point. The lower float switch turns it off again when the water has been pumped out of the sump pit.
How Does the System Work
When the
sump pit has water in it
the lower float switch (LFS) is closed (i.e. floating horizontally). As the water level in the pit rises, it eventually reaches the upper float switch (UFS) lifting that float to the horizontal and closing its switch.
With the UFS closed, current flows from the 12V terminal of the battery to the
relay coil energising it. This connects the COM and NO terminals of the relay allowing current to flow along a second path from the battery to the relay coil:
battery 12V -> LFS -> relay COM -> relay NO -> relay coil
Therefore, once the relay has been energised, it will
latch - i.e. remain energised - as long as the LFS remains closed (which it will as long as it remains under water). As the
pump empties the water from the sump pit, the pump stays on even when the UFS stops floating and until the water finally gets down to the level of the LFS. When the water level goes below the LFS, it breaks the connection between the relay coil and the 12V terminal of the battery, and so the relay switch will open
turning off the pump.
Connecting the Pump
The output from the above described system comprises one 0V and one 12V connection. These are to be connected to the coil of a second
relay which will physically switch the
pump.
If it is a
12V pump you simply connect the
COM of the second relay to the battery 12V terminal, the
NO of the second relay to the pump's 12V connection, and the 0V terminal of the battery directly to the 0V connection of the pump.
If this is a
mains powered pump the final connections must be made by a
qualified electrician with everything insulated and earthed according to regulations. (The thick red lines in the above schematic correspond to the mains
live, and the thick black lines to the mains
neutral.)
Sump Pump Control Circuit Board
Pictured below is a small board put together following the main schematic shown at this beginning of this article. The only added component is an
LED (with current limiting
resistor) to give a visual indication of when the pump is on. With a board such as this it is possible to simply screw the float switches into the screw-in terminal connectors and keep everything tidy.
If you would like to have a board such as the one pictured above put together, please contact
neil@reuk.co.uk with details of your exact requirements.
Further Uses for this System Design
This design is also useful in many
irrigation,
rainwater toilet flushing, and
rainwater collection systems, particularly in remote locations where reliability and ease of maintenance are essential.
NEW - Click here to read our article
Simple Well Pump Controller in which we modify this system so that it can be used to automatically
fill (rather than empty) a tank.
Acknowledgements and Thanks
Many thanks to
Nyge for his hard work and vital contributions to this new pump control system.
Article Last Modified: 08:58, 5th Aug 2008Comment on this Article
If you have any comments on this article, please email them to
neil@reuk.co.uk.
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