Simple 555 ICs tester circuit


Most IC-555 is used to generate frequency, and sometimes we need to know. Is it good or bad© But normal multimeter cannot check it. Thus, I make a simple 555 ICs tester circuit. Which is tested correctly and faster.

How it works
Resistors R1-R3 acts as limit current and reduce voltage to LED1-LED3. Which is LEDs show state on “Trigger” or “Low” or “High”. The Diode D1 is set voltage to pin 2 less than 1/3 VCC (0.7 volts). When slide switch S1 at position 2 (Trigger IC).

Simple 555 ICs tester circuit

Before apply voltage to this circuit, we must put the test IC to socket completely. When enter voltage to the circuit and switch S1at position 3 (no trigger) will see LED1 (low) glow show that the output in state ” low” voltage at the B point about 0.2 volts.

Next, trigger at pin 2 by slide S1 come to position 2 cause voltage at pin 2 about 0.7 volts. Thus the output voltage will change state is “high” voltage at point B about 3.5 volts. The LED2 ( High) and LED3 (Trigger) glow and when switch S1 come to position 3 will cause LED2 and LED3 go out.

In this case above will show that IC-555 is good. But apply the power supply to this circuit, then switch S1 to position 2. The LED1 will glow but after that slide S1 come to position 3 but LED1 still glow up. If when apply voltage to this circuit then LED2 will also still grow (S1 at position 2). And slide S1 come to position 3 also still not change state show that this IC-555 bad.


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