This simple component test can be used on the bench to check the state of components and circuits. Simple to use it has three indicator LEDs and the test current is very low.
With this taster we can check the status of diodes, LEDs, transistor junctions, resistors, capacitors, transformers and more.
The reader will be able to learn more about testing other components in our "How to Test Components" book series, volume 1 to 4, where we teach to use testers of this type and of other types as well.
The circuit operates with an alternating signal that applied to diode and other components with junctions causes only one LED to light in one-way driving.
When testing other devices, if there is continuity, the two LEDs light up, and if the circuit is open or has too high resistance, none lights up.
Power is supplied by the power supply through a small transformer, but the test current is too low, which means that the components and circuits tested are not in danger of being burned or overloaded.
All tests must be done with the component out of the circuit or with the power turned off.
In Figure 1 we have the complete diagram of the micro-test.
As the assembly is very simple, it can be made based on a small terminal strip, as shown in figure 2.
In the assembly it is very important to observe the polarity of the LEDs and diode.
The resistors are 1/8 W with any tolerance and any transformer with 5 or 6 V of secondary and current of 100 to 500 mA can be used.
For the tests, two probes or wires with alligator clips can be used.
To check for normal operation, press one end or claw into the other: LEDs 2 and 3 should light up.
The LED is always on, indicating that the circuit is working.
Material list
D1 - 1N4002 - rectifier diode or 1N4004
LED1, LED2, LED3 - Common LEDs of any color
T1 - Transformer - see text
S1 – On-Off switch
R1 - 2k2 ohms - resistor - red, red, red
R2 - 1k5 ohms - resistor - brown, green, red
PP1, PP2 - probes or clips
Several:
Terminal strip, power cable, wires, mounting box, etc.
