Electronic Sensor & Component Tester




About: I'm an Electronics Engineer who likes to make Doze Lamps, Lumen Powered Thingamajigs, Almighty Brainy Buttons, Tweeting Weather Stations and share them on Instructables.

Electronic Sensor & Component Tester

This circuit is a low cost Electronic Sensor & Component Tester which is powered by a 9V, 300mA Battery. It does not include any Integrated Circuit(IC), Sensor or Digital Display. This circuit can be used to test any faulty components. Unlike a Digital Multimeter it will not display the values of the component. It can also be used to test the polarity of certain forward biased or reversed bias components. It can test the following components: Resistor, Variable resistor, Diode, Thermistor, LDR, LED, NPN & PNP Transistor, Switch, Buzzer, Motor,Speaker. It can also be used to test the continuity of a wire.


Step 1: Requirements

Components and Parts: 1 X 9V,

300 mA Battery and Battery Holder

1 X Resistors- 22K ohm,

1/4 W390 ohm, 1/4 W

,1 X Dot Matrix PCB (2X5cm)

1 X Led ( Any Colour)

3 X Pin Header/ Pin Holder

1 X Jumper Wire

1 X 8ohm Speaker

Equipments:1 X Soldering Iron and Soldering Wire

1 X PCB cleaning solution/ Liquid Flux

Time and Capital:30 Minutes & $1 to Spend on components

Step 2: The Circuit Diagram

Connect the following components by placing them into the PCB according to the given circuit diagram.V1 = 9V BatteryR1 = 390 ohm resistor, R2 = 22K ohm resistor, L1 = LED,

J1 = Header Pins:There are three terminals in the header pins:

+ / Collector is used as a positive terminal and also a collector terminal of the component.

Base is used as a base terminal of the component.

- / Emitter is used as a negative terminal and also a emitter terminal of the component.

You can also connect a speaker as shown in the second circuit diagram.

Step 3: Soldering

Clean the PCB with the PCB cleanser or Liquid Flux.Solder the components to the PCB with the help of your soldering iron.

Caution & Safety: Use safety glass while soldering.Be careful while soldering. Do not touch the tip of the soldering iron to prevent harmful burns.

Step 4: Final Testing

1. Inorder to test a resistor plug it between the Collector(+) and Emitter(-) terminals of the circuit. If the LED begins to dim then the resistor is working. NOTE: The values of the resistor cannot be determined.

2. Inorder to test a variable resistor plug it between the Collector(+) and Emitter(-) terminals of the circuit. Turn the wiper, if the the brightness of the LED begins to change according to the change in the angle/ direction of the wiper, then only the variable resistor is said to be working.

3. Inorder to test a diode plug it between the Collector(+) and Emitter(-) terminals of the circuit in forward bias. In this case the LED should light up. Now place the diode in reverse bias. The LED should not light up. If and only if the following conditions are satisfied then only the diode is said to be working.

4. For thermistor follow the same instructions as that of the resistor. NOTE: With change in the temperature, the resistance of the thermistor will change and the brightness of the LED will vary.

5. For LDR refer to instructions for thermistor. NOTE: In this case the amount of light incident on the LDR will determine its resistance.

6. For LED, Switch, Buzzer, Motor, Speaker follow instructions for diode.If the LED glows its working. If the switch conducts while in the ON position, its working. If the motor shaft begins to turn, its working. If the buzzer and speaker begin to make sounds, they are working.

7. For NPN and PNP transistors, connect the transistor to the Collector, Base and Emitter pins of the header strip. If the LED lights up, it is working.

If you have followed all the steps and you have connected all the components according to the circuit diagram, your circuit should be fully functional and ready to test.

If you have any questions as to how to test any component using this circuit, leave a comment in the section below



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18 Discussions

techno maker

3 years ago

but how does it work .how the variable resistor work.it usually work with transistor

2 replies

3 years ago

great project

can i place your project on my website.

i'm working on a website which is related to electrical projects.

i also mention your name, link and other info.

plz reply

1 reply

Reply 3 years ago

Yeah Sure. Your welcome to feature any/all of my Instructables on your website.


Reply 4 years ago

Unfortunately I do not have a YouTube link to this instructable. But if you have any difficulties, do share them in the comments section. Don't forget to subscribe!


Reply 4 years ago

Connect the Wire between the collector and emitter. The buzzer should buzz if the wire has no fault.


4 years ago on Introduction

Simple and Good Circuit for quick job.... :-)

Do you have something similar for testing "Capacitors".. ?


4 years ago on Step 4

Good useful device -- well explained. A bit of work to package it and make it an easy to use tool would have been a winner.


4 years ago on Introduction

nice n simple so east to make this i have already make this in my college time


4 years ago

nice and simple. I like it!


4 years ago on Introduction

This is a good circuit for quick and dirty component testing. Good job!