Water Detector With Sump/Bilge Pump Controller

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This moisture detector with pump controller is built around the special purpose LM1830 IC. The LM1830 is designed to detect moisture by passing an AC current through a set of probes. An internal comparator compares the resistance of the probes to an internal reference. When the resistance between the probes is low (indicating the presence of water or other conductive liquid) then the IC triggers it's output. An AC signal avoids electroplating and corrosion problems that are common when DC is used. To provide an adjustable delay hysteresis to avoid cycling the pump, a timer based around the 555 is used a range of about 5 seconds to two minutes. In this way the pump will stay active for a set amount of time even if the fluid level is below that of the probes.


Scheamtic of the water detector with pump controller


Total Qty.
R11470 Ohm 1/4 W Resistor
R2, R4110K 1/4 W Resistor
R316.8K 1/4 W Resistor
R511 Meg Linear Taper Pot
R6151K 1/4 W Resistor
C11470uF 35V Electrolytic Capacitor
C210.001uF Ceramic Disc Capacitor
C310.05 uF Ceramic Disc Capacitor
C4120uF 35V Electrolytic Capacitor
C516.8uF 35V Electrolytic Capacitor
C6, C820.01uF Ceramic Disc Capacitor
C71100uF 35V Electrolytic Capacitor
U11LM1830 Fluid Detection IC
U21555 Timer
Q112N5305 NPN Power Transistor
D1, D221N4148 Signal Diode
D311N4002 Rectifier Diode
K11Relay With 12V Coil (See Notes)
S11SPST Switch
PROBES1Stainless Steel Probes (See Notes)
MISC1Case, Knob, Board, Wire, Sockets For U1 and U2


  1. The probes should be made of stainless steel and mounted in a non-conductive fixture. Stainless steel nails, bolts or welding rod will make ideal probes. Good non-conductive materials are Lexan, plexiglass or plastic. The probes are to be placed at the liquid level at which you wish the pump to turn on.
  2. K1 should be chosen according to the requirements of the pump. If you are running a 12V pump then common automotive relays will work fine. If you are running a mains powered pump then you will need to make sure the contacts are rated accordingly.
  3. S1 provides a manual pump switch.
  4. R5 adjusts the on-time of the pump once moisture has been detected. It is adjustable from approximately 5 seconds to approximately 2 minutes.
  5. The probes should be cleaned periodically to assure reliable operation.

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Water Detector With Sump/Bilge Pump Controller
Friday, November 12, 2010 2:06:15 AM
In 2009 I bought some LM1830's for 2.50 each from Mode components in the UK, after my purchase there was one left in stock. The 1830 data sheet offers circuits to use the IC either to fill or to empty a tank, downloading this sheet might be helpful. The LM1830 is obsolete, and, as is usually the case most remaining stocks have been bought up by traders who demand greedy prices. I would question the wisdom of relying on an obsolete semiconductor for a new circuit, particularly when numerous alternative circuits are available on the internet .
Water Detector With Sump/Bilge Pump Controller
Tuesday, July 20, 2010 12:29:04 PM
I just looked at the LM1830 IC on eBay... The cheapest price I could find was $42.00 each! Is there an alternative chip that is cheaper? Thanks
Water Detector With Sump/Bilge Pump Controller
Tuesday, September 01, 2009 2:46:21 AM
hi there..i choose this circuit as my project..can i use AC pump instead of using 12Vdc pump and replace 1 meg linear taper pot into 1 meg log taper pot.. is it ok? thnx ..pls reply
Water Detector With Sump/Bilge Pump Controller
Saturday, May 23, 2009 1:46:51 AM
Why do you put a 470 ohm res. at Pin 14 that is +Vcc. The mfgr cites +16V operating voltage and direct connect to Vcc.
Philippe Tremblay
Water Detector With Sump/Bilge Pump Controller
Friday, October 17, 2008 12:53:15 PM
This circuit works very well !!! I used it to start a sub-pump in the basement in case of water distribution malfunction. Easy, inexpensive and secure !!!! Thanks !!!!
Water Detector With Sump/Bilge Pump Controller
Wednesday, October 08, 2008 9:41:34 AM
i want to combine this water detector with sump/bilge pump controller with bluetooth.thats means i want to connect in handphone that it will detect the water.can u give an idea?
Water Detector With Sump/Bilge Pump Controller
Wednesday, September 10, 2008 1:58:31 AM
i would like to construct an operational one that includes a level sensor, analogue to digital & digital to analogue interfacing circuit & an operational monitoring software.
nilesh kashid
Water Detector With Sump/Bilge Pump Controller
Saturday, September 06, 2008 1:16:17 AM
its a interesting circuit!!! will u give me the details about IC1830 equivalent?
Water Detector With Sump/Bilge Pump Controller
Wednesday, May 21, 2008 5:17:00 AM
Is there a replacement for the LM1830? i cannot source one in England.
Water Detector With Sump/Bilge Pump Controller
Sunday, May 04, 2008 5:10:10 AM
Just like chris I need a circuit for refilling a tank. Could you please send me the circuit or instructions on how to modify this one to do it. I know how to make a detector and refill for a single probe. But it wouldn't do much good because it would need a few seconds after the initial low point to get the fluid back up to a suitable level. If anyone knows how could please email me.
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