A Quartz crystal tester is needed if you want to know whether the crystal is good or bad (broken). As many circuits use a crystal as an important component to oscillate signals, these signals are the main requirement for other devices in the circuit. If the crystal got damaged means we cannot easily test the crystal without an oscillator circuit, to avoid this situation here we design a simple crystal tester circuit. This simple circuit can be used to check the crystal element whether it is working or not working. This tester gives an LED light indicator. If the crystal under test is good, the LED indicator will light, and stay off if bad.
Hardware Required
| S.no | Component | Value | Qty |
|---|---|---|---|
| 1. | Transistor | BC547 | 2 |
| 2. | Test Push Button | – | 1 |
| 3. | Resistor | 100KΩ,2.7KΩ,270Ω | 1,1,1 |
| 4. | Capacitor | 220pF,100pF,0.01uF | 2,1,1 |
| 5. | Diode | 1N4007 | 1 |
| 6. | Quartz Crystal | – | 1 |
| 7. | Crystal Connector | – | 1 |
| 8. | LED | – | 1 |
| 9. | Connecting Wires | – | – |
| 10. | Battery | 9V | 1 |
Circuit Diagram
Construction and Working
As we can see in the circuit, two BC547 transistors are connected together with capacitor C2. Here the base terminals of these transistors are works as a test terminal for crystals. Now the first transistor is used as an oscillator, and the second one is employed as the detector. The oscillator will produce a high-frequency signal if a good crystal is connected to the tester’s probes. This AC signal will flow through C3 and activate the base of Q2, and cause the Q1 to light the LED indicator, telling us if the crystal is good. The D1 is used to provide the back path of the AC signal.
If the crystal is bad, the oscillator won’t produce an AC signal on the Q1 output, and there will be only a DC voltage on the Q1 emitter. This DC voltage will be blocked by C3, so the Q2 won’t be triggered to light the LED indicator. This means if the LED glows then the crystal under test is working if the LED is not glowing means the crystal might damage or faulty. This circuit can be powered by a 9-volt battery.
Applications
Used to test if the crystal is working or not in electronics projects.
