project
Here is a complete, portfolio-ready PLC Project: an Automatic Water Tank Filling System with Dry-Run Protection.
This project uses Delta DVP-14SS2 (or similar) and DiaStudio (ISPSoft). It demonstrates Timers, Counters, Interlocks, and Fail-Safe logic.
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Project Overview
Objective: Control a pump to fill an overhead tank from a borewell. The system stops when full, prevents the pump from running dry, and alerts the operator if the pump runs empty for too long.
I/O Assignment:
Tag Address Type Description
Start X0 NO Pushbutton Momentary start command
Stop X1 NC Pushbutton Emergency/Manual stop
Low_Level X2 NO Float Switch Borewell water available (Dry-run protection)
High_Level X3 NO Float Switch Tank is FULL (Top sensor)
Pump_Out Y0 Relay Contactor for the pump motor
Alarm Y1 Indicator Flashing warning light for "Dry Well"
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The Ladder Logic (Text-Based Representation)
Open DiaStudio, create a new project, and build this network by network.
Network 1: Seal-in / Latching Circuit
(Maintains the pump state even after releasing the Start button)
```
|---[X0]----[/X1]----[X2]----[/X3]----[ ]--(Y0)---|
| | |
| |--[Y0]----|
```
Logic: Pump runs if:
1. Start pressed AND Stop NOT pressed.
2. Water is available (X2 is ON).
3. Tank is NOT full (X3 is OFF).
4. The circuit latches itself via Y0.
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Network 2: Dry-Run Detection Timer
(If the pump runs but X2 turns OFF, start a 10-second countdown)
```
|--[Y0]----[/X2]----[TON T0 K100]----|
```
Logic: Timer T0 starts counting only when the pump is running (Y0) but the low-level sensor (X2) is dry. If this lasts 10 seconds, T0 will turn ON.
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Network 3: Alarm & Shutdown Latch
(Traps the fault and flashes the alarm)
```
|---[T0]----[ ]--(Y1)---| (Alarm Light)
|---[T0]----[ ]--(SET M0)---| (Fault Latch)
```
Logic: When T0 times out, the alarm flashes and an internal relay M0 latches the fault state.
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Network 4: Fault Interlock
(Prevents restart until manually cleared)
```
|--[M0]----[ ]---------------[/Y0]---| (Forces Y0 OFF)
|--[M0]----[X1]----[RST M0]---| (Reset fault by pressing Stop)
```
Logic:
· M0 keeps the pump turned OFF even if Start is pressed.
· Pressing the Stop button (X1) resets the fault latch.
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How It Works (Step-by-Step)
1. Normal Fill Cycle:
· Operator presses Start (X0).
· Pump Y0 turns ON.
· Water fills the tank.
2. Stop at Full:
· When water reaches the top, High_Level (X3) turns ON.
· The normally closed contact [/X3] breaks the circuit.
· Pump Y0 turns OFF automatically.
3. Dry-Run Protection (Safety):
· If the borewell runs dry, Low_Level (X2) turns OFF.
· Timer T0 starts (10-second grace period).
· If water doesn't return in 10 seconds, the system shuts down and triggers the Alarm (Y1).
4. Restarting after Fault:
· The pump will NOT restart automatically.
· Operator must press Stop (X1) to clear the fault, then press Start (X0) again.
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Screenshots to Take (Portfolio Images)
Image 1: Main Ladder Logic
Take a screenshot of Networks 1 & 2 in DiaStudio.
Image 2: Alarm & Latch Logic
Take a screenshot of Networks 3 & 4.
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Wiring Guide (For your documentation)
· X0 (Start): Connect to 24VDC (+) via a NO pushbutton.
· X1 (Stop): Connect to 24VDC (+) via a NC pushbutton.
· X2 (Low Level): Connect to PLC 24V Supply and terminal X2.
· X3 (High Level): Connect to PLC 24V Supply and terminal X3.
· Y0: Connect to the coil of a 24VDC relay (which drives the motor contactor).
· COM: Connect to 0VDC (Ground).
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Why This Project Works for Your Portfolio
· ✅ Practical Application: Water level control is used in 80% of industries.
· ✅ Safety Focus: Includes "Dry-Run" protection (demonstrates risk assessment).
· ✅ Complexity: Uses Timers, Latching relays (SET/RST), and Interlocks—not just simple ON/OFF.
· ✅ Troubleshooting: Requires a manual reset after a fault (shows robust design).
Pro Tip: In DiaStudio, use the "Simulation" mode to test the logic. You can force X2 OFF while Y0 is running to see the 10-second countdown in Timer T0.