8051-Based Automatic Water-Tank Level Controller with Sump Dry-Run Protection for Motor Pumps

Automatic Water-Tank Level Controller with Dry-Run Protection is a diploma ECE hardware project that solves an everyday problem in Tamil Nadu homes and small apartment blocks. Most buildings pump water from an underground sump to an overhead tank using a single-phase motor that someone switches on and off by hand. The tank overflows when people forget to switch off, runs empty at night when they forget to switch on, and the pump is often left running when the sump itself is empty, which overheats and damages the motor within minutes.

Our controller uses an 8051-family microcontroller (AT89S52) to read stainless-steel electrode probes in the overhead tank (low, half and full levels) and a float switch or electrode pair in the sump. It switches the pump motor through a transistor-driven relay and contactor, starts the motor when the overhead tank falls below the low mark, stops it at the full mark, and cuts off immediately if the sump runs dry. A second protection, a fill-timeout, stops the motor if the overhead level does not rise within a set time. A 16x2 LCD shows tank level, sump status and motor state, and a buzzer warns of overflow risk and dry-run faults.

Every circuit block is first simulated in Multisim or TINA before being assembled on veroboard and tested on a small demonstration tank. The bundle includes the block diagram, control flowchart, Embedded C logic, bill of materials in rupees and a testing table for the team to fill with their own readings.

Abstract

Manual switching of water pumps wastes water through overflow and damages motors through dry running when the sump is empty. This project designs and builds an automatic water-tank level controller based on the 8051 microcontroller. Electrode probes sense three levels in the overhead tank, and a float switch senses water in the sump. The microcontroller switches the pump through a relay and contactor, displays status on a 16x2 LCD and sounds a buzzer on faults. Two independent protections, sump-empty cut-off and fill-timeout, prevent dry running. The circuits are simulated in Multisim/TINA, assembled on veroboard and tested on a demonstration tank using a small 12 V pump, with the 230 V contactor stage tested separately under supervision.

Introduction

In Chennai, Coimbatore and Madurai, most independent houses and small apartments receive corporation or tanker water into a sump and lift it to an overhead tank. Motor switching is manual, usually done by a family member or the watchman. The result is daily overflow, water shortage at peak hours and frequent motor rewinding bills.

Existing system

• Manual switching: depends on someone remembering; overflow and dry running are common.
• Simple float-switch controllers: start and stop the motor on overhead level only, with no sump check, so the motor can still run dry.
• Commercial controllers: available, but many basic units lack a display, fault indication or a timeout.

Proposed system

• Three-level sensing in the overhead tank with hysteresis (start at low, stop at full) to avoid rapid relay chatter.
• Sump dry-run cut-off that blocks starting and stops a running motor when the sump is empty.
• Fill-timeout protection if the overhead level does not rise, which also catches an airlock or a broken pipe.
• LCD status, buzzer alarm, manual override switch and a fault latch that needs a reset press.

Feasibility

• Technical: uses the 8051, relays and LCD interfacing taught in 34052 and 34066.
• Economic: indicative component cost is about ₹2,400–2,700 including the contactor and enclosure.
• Operational: a family member only needs to read the LCD and press reset after a fault.
• Schedule: fits the 14-week project semester with simulation in the first half and hardware in the second.

Homes and small apartment blocks in Tamil Nadu store water in an underground sump and lift it to an overhead tank with a single-phase pump that is switched manually. When the person responsible forgets, the overhead tank overflows and wastes water, or it runs empty and residents have no water at peak hours. Worse, the pump is often switched on or left running when the sump is already empty. Running dry, the pump loses its water cooling and lubrication, its seal and winding overheat, and motor rewinding becomes a recurring expense.

Existing low-cost float controllers watch only the overhead tank and do not know whether the sump has water, so they cannot prevent dry running. The problem is to design a low-cost, reliable controller that automatically maintains the overhead tank level, prevents dry running using sump sensing and a fill-timeout, clearly displays status and faults, and can be built and tested by a diploma team with standard lab components.

In scope

• One overhead tank (three levels: low, half, full) and one sump (empty or available).
• Control of one single-phase pump through a relay-driven contactor (demonstrated with a 12 V DC pump and, separately, a lamp load on the contactor under supervision).
• LCD status display, buzzer alarm, manual override and fault reset.
• Simulation, veroboard prototype, testing table and cost estimate.

Out of scope

• Three-phase motors, star-delta starters and motor overload relays (mentioned under future scope).
• Mobile app or GSM alerts.
• Continuous (analogue) level measurement; this project uses discrete levels.
• Permanent installation on a real building, which must be done by a licensed electrician.

We follow a design, simulate, build, test method organised as a V-model: every design block has a matching test planned before it is built.

Control logic (truth table summary)

• Sump empty → motor OFF, buzzer ON, LCD "SUMP DRY".
• Sump available and overhead below LOW → motor ON.
• Motor ON and overhead reaches FULL → motor OFF.
• Motor ON and no level change within the timeout (for example 10 minutes) → motor OFF, fault latched, buzzer ON.