@▷ LED Component Tester with Torch | Diagram for Schematic

LED Component Tester with Torch

Here is a simple tester for Hobbyists. This LED Component tester can test the integrity of electronic components from resistors to ICs before soldering. It reduces the job of testing the components using multimeter. The tester gives LED indications about the Good or Bad conditions of the components. A White LED torch is added to verify the value of the components if light is not sufficient.

The circuit layout is straight forward. Two bipolar NPN transistors are used to drive two LEDs based on their base bias. When the tester is switched on through S2, Red LED lights because T2 gets base bias through R2. At the same time, Green LED remains off because the base of T1 is floating .

When a component is placed between the Probes, electrical continuity establishes and T1 gets base current through R1. When T1 conducts, Green LED turns on and Red LED turns off since the base of T2 is grounded when T1 conducts. This indicates that the component under test is good. In short Green LED lights only when a good component is connected to the probes. If the component is bad, probes will not get electrical continuity and T1 remains off. In this state only Red LED light indicating that the component is bad. Test procedure is given below.

LED Component Tester Circuit diagram

Test Procedure

  • 1. Polarity
    Connect Red probe to positive track of circuit board and Black probe to test point. Circuit board under test should be ON
    Green LED ON – Positive supply. Green LED OFF and Red LED ON – Negative supply or No power
  • 2. Continuity
    Connect both Red and Black probes across the test points
    Green LED ON- Continuity. Green LED OFF and Red LED ON- No continuity
  • 3. Resistor. 1 Ohm to 500K
    Connect Red and Black probes on either side of Resistor
    Green LED ON- Resistor OK. Green LED OFF and Red LED ON-Resistor burned
  • 4. Capacitor Electrolytic
    Red probe to positive and Black probe to negative of capacitor
    Green LED ON and gradually fades and then Red ON- Capacitor Good. Red LED always ON- Capacitor bad
  • 5. Capacitor Disc
    Same as above.Probes can be connected either way round
  • 6. LED, Diodes, Photodiodes, Infrared diodes
    Red probe to Anode and Black probe to Cathode
    Green LED ON – Good diode and LED. Green LED OFF and Red LED ON- Diode or LED bad
    Change the direction of Probes. If the Green LED ON diode or LED is Open
  • 7. LDR
    Red and Black probes at the leads of LDR
    Green LED ON and Red LED OFF. Mask with hand. Green LED turns OFF-LDR good

Probes with Crocodile Clips