This repository contains the implementation of a digital elevator people-counting circuit built using standard digital ICs, IR sensors, logic gates, a 7-segment display, and LED indicators. The circuit counts people entering an elevator (0–9), displays the count, and triggers safety indicators when the capacity limit is reached.
See the demo video below for a quick visual explanation of how the system works.
Full system description referenced from project documentation.
This project implements the assignment requirement for IE2010 – Digital Electronics, Semester 1 (2020).
- The elevator can carry a maximum of 9 people
- A digital IR sensor detects people entering
- Count is shown on a single 7-segment display
- Green LED ON when count < 9
- Red LED + Buzzer ON when count ≥ 9
- Use a 74193 / 74HC93 counter
- Use a 7447 / CD4511 BCD-to-7-segment decoder
- Power the circuit using USB / 5V supply
This repository contains a full working implementation using a breadboard prototype.
Below is the breadboard implementation used for the project: Go see the project on Tinkercad
- 74HC93 – 4-bit binary counter
- CD4511 – BCD to 7-segment decoder
- 74HC08 – AND gate (logic conditions)
- 74HC04 – Inverter (signal conditioning)
- IR sensors × 2 (people detection)
- Buzzer module (over-capacity alert)
- Green LED (safe state)
- Red LED (over-capacity state)
- Common Cathode 7-segment display
- Resistors (for LEDs, pull-down logic, IR modules)
- Connecting wires
- Breadboard
- USB 5V power supply
- 5V supplied via USB
- Breadboard rails distribute +5V and GND
- ICs powered through Vcc and GND pins
- LEDs current-limited with series resistors
- Buzzer triggered via control logic
- IR sensor output transitions from HIGH → LOW when a person passes
- A pulse is fed into the 74HC93 counter
- Counter increments by 1 per detection
- The 74HC93 outputs a 4-bit binary number
- This binary output is sent to the CD4511 decoder
- CD4511 converts BCD to 7-segment signals
- The 7-segment display shows numbers 0 to 9
Using AND gates (74HC08) and inverters (74HC04):
-
If count < 9 →
- Green LED = ON
- Red LED = OFF
- Buzzer = OFF
-
If count ≥ 9 →
- Red LED = ON
- Buzzer = ON
- Green LED = OFF
| Count | Binary (QdQcQbQa) | Display | Green LED | Red LED | Buzzer |
|---|---|---|---|---|---|
| 0 | 0000 | 0 | ON | OFF | OFF |
| 1–8 | 0001–1000 | 1–8 | ON | OFF | OFF |
| 9 | 1001 | 9 | OFF | ON | ON |
- IR sensor properly detects hand/obstacle
- Counter increments correctly
- 7-segment displays correct digit
- LED indicator changes at threshold = 9
- Buzzer triggers when count ≥ 9
- Current draw measured ≈ 50–55mA (safe for USB 5V)
This project is licensed under the MIT License.
See the LICENSE file for details.
If you use or reference this work in academic or technical documents, please cite:
Kasthuriarachchi, S.D., Perera, H.A.K.D., Jayasekera, P.Y.R., and Liyanage, R.S.H. (2020) Digital Circuit for an Elevator.[Online] Available at: https://github.com/sadeep654/Digital-Circuit-for-an-Elevator (Accessed: date-you-accessed).
- Kasthuriarachchi, S.D.
- Perera, H.A.K.D.
- Jayasekera P.Y.R
- Liyanage R.S.H.
Copyright (c) 2020 Sadeep Dilshan Kasthuriarachchi