Feb 212023

555 Timer Tester Circuit (PCB)

This 555 timer tester circuit, allows us to make sure that this integrated circuit works properly. This same test can be achieved by operating the 555 as an astable multivibrator, but this test does not allow observing its operation in detail. The suggested manual procedure clearly shows how the 555 IC works.

How does the 555 Timer tester circuit work?

To achieve this, it is necessary that we obtain the correct low or high voltage levels at the output of the 555 timer (pin 3), when a high or low voltage is applied to the trigger input of the 555 (pin 2).

To indicate when pin 2 is in low state and 555 was triggered, LED D1 turns on.

  • When the 555 is triggered (pin 2 has “0” volts), the output (pin 3) will be high, LED D3 will turn on and LED D2 will be off.
  • When the 555 is not triggered (pin 2 is Vcc (Bat)), its output (pin 3) will be low, LED D2 will turn on and LED D3 will be off.

If, for some reason, the previous steps are not met, then the 555 is damaged.

555 Timer Tester Circuit

Pin 7 is not used in this circuit because its state is normally the opposite of pin 3 (the output). Pin 7 is used to discharge a capacitor that is not used in this circuit.

555 timer IC

Suggested Printed Circuit Board for 555 IC Tester (PCB)

Below is a printed circuit Board (PCB) for the 555 IC tester circuit. The image on the left gives an idea of the final appearance of the PCB, and the image on the right shows the copper side of the printed circuit board.

List of components for the 555 IC tester circuit

  • 1 555 IC timer (555 Timer under test) (IC)
  • 1 555 base
  • 3 330 ohms 1/4 watt resistors (R1, R2, R3)
  • 3 LEDs, 2 red, 1 green (D1, D2, D3)
  • 1 two poles switch (SW)
  • 1 9-volt battery (Bat)
  • 1 two terminal connector (for the battery)
  • 1 three terminal connector (for the switch)

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