This project for Digital Display AC Line Tester Circuit is a small electronic tester used to detect the presence of mains AC voltage without direct contact.
It is a wireless mains voltage tester.
When the sensing probe comes near a live AC wire then the circuit detects the field and shows the count on a 7-segment display.
The main IC used here is CD 4033 which is a Johnson decade counter and display driver.
It directly drives a 7 segment display without needing a decoder.
Circuit Working:
Parts List:
| Component | Specification | Quantity |
|---|---|---|
| Resistors | 100k 1/4 watt | 2 |
| Capacitor | Ceramic 0.1uF | 1 |
| Semiconductors | IC CD 4033 | 1 |
| 7-Segment LED Display Common Cathode | 1 | |
| ON/OFF Switch | 1 | |
| Battery 9V PP3 | 1 | |
| Sensor Probe 10cm insulated wire | 1 |
The sensing probe acts like an antenna.
When the probe comes close to a live AC wire it picks up the AC electric field.
This signal is very weak but enough to provide small triggering pulses to pin 1 of the CD 4033 IC.
The CD 4033 IC advances its counter each time it receives a pulse at pin 1.
The output is decoded internally and shown on the 7 segment display.
When no voltage is sensed then the display remains steady.
When the probe detects mains the counter increases and the 7 segment and shows a digit.
In this way the tester confirms the presence of mains voltage wirelessly.
Note:
CD 4033 IC advances by one digit for each input pulse the formula for display count is just simple:
Count displayed = Number of pulses sensed by pin 1
How to Build:
To build a Digital Display AC Line Tester Circuit follow the below steps for connections:
- Gather all the parts as shown in above circuit diagram
Connection of CD4033 IC:
- Pin 1 goes to sensing probe as it catch weak AC signal.
- Pin 2 goes to ground with resistor R2 so clock not stop.
- Pin 3 goes to Vcc so display work normal.
- Pin 8 goes to battery negative GND.
- Pin 15 goes to ground with resistor R1 so counter does not reset by itself.
- Pin 16 goes to +9V battery positive.
Connection of 7 segment LED display:
- Pin 6 goes to segment f.
- Pin 7 goes to segment g.
- Pin 9 goes to segment d.
- Pin 10 goes to segment a.
- Pin 11 goes to segment e.
- Pin 12 goes to segment b.
- Pin 13 goes to segment c.
- Pin GND of segment connect to the GND
- Capacitor C1 connect between pin 16, pin 3 and switch side other end of C1 goes to ground.
- Switch S1 connect between capacitor and +9V battery as it turn circuit ON or OFF.
Conclusion:
Digital Display AC Line Tester Circuit is a very simple and low cost project to detect mains voltage wirelessly.
It is safe because no direct connection with AC mains is made.
The sensing probe only picks up the electric field.
The CD 4033 IC makes it easy to directly drive the 7 segment display.
This project is useful for electricians, students and hobbyists to check live AC wires without risk.