Miniature crystal tester with the possibility of measuring frequency.
The following crystal tester allows fast testing of crystals from a frequency of about 0.5MHz. In addition to the connector, it is all designed for SMD mounting and allows the connection of a counter to measure the frequency.
The following figure shows the wiring diagram.
The tester circuit consists of two separate parts. The first, formed by transistor T1, is a crystal oscillator. The crystal is of course connected externally to pins J3 and J4. When a functional crystal is connected, the transistor oscillator oscillates. After passing through capacitor C3, this frequency is rectified on diodes D1 and D2 and filtered by capacitor C4. The voltage rectified in this way is subsequently amplified by transistor T2, which lights up the LED D3.
If necessary, it is possible, preferably again, to connect a counter to the emitter of transistor T1 via a small capacitor and read the frequency on it.
The crystal tester was designed for SMD design.
The connection was, of course, set up and its correct function verified.
Partlist R1 33k 0805 R2 1k 0805 R3 470R 0805 C1 1n 0805 C2 100p 0805 C3 1n 0805 C4 10n 0805 D1 BAT48 SMD D2 BAT48 SMD D3 LED 3mm red T1 BC817 T2 BC817
Original link: http://pandatron.cz/?586&tester_krystalu