Introduction
A simple and at the same time very much utility-oriented best continuity tester circuit is described here for assembling and put to use. There are many circuits available on continuity tester for assembling. But this circuit is unique because it is very simple and used just two silicon transistors that are easily available from one's own shelf for assembling and use readily. It is also easily available and can be procured from any electronics shop in your own town.
For any electronics technician, a simple continuity checker is handy for day-to-day service work. The technical service becomes easier and much simpler and quicker if one uses this simple tester to check most of the electronics items such as electronics components or elements to put in the circuit for assembling work.
Items to be checked
Wherever continuity check should be adopted for confirmation of proper working of the circuit elements, this tester becomes handy to test and get the immediate result.
Circuit elements such as
Fuses
Coils
Transformer windings -Primary and secondary
Relay coils
Low-value resistors
Continuity of the PCB copper track or its shorts in the pattern
With the ingenuity of the user, the tester can be used to test semiconductors like diodes, Transistors and LEDs for their primary status.
Generally, the continuity of any two points can be ascertained with the help of this tester.
The Circuit
Parts List
Q1,Q2 = BC147B NPN silicon transistors
LED1 = Red Light Emitting Diode (LED)
R1 = 22K ohm resistor
R2 = 15K ohm resistor
R3 = 680 ohm resistor
P1 = 10K ohm Potentiometer
SW1 = on/off switch
B1 = 3V Battery
Working
Connect the circuit elements/components under test between the two points A and B. Switch on the circuit. LED glows when the continuity is OK. It may be necessary to slightly adjust the Potentiometer/preset to get the glow of the LED. Dry cells can be used as a power source since the current consumption is low. As such the whole assembly of the circuit is compact and small to carry for the service work. It may be noted that only components whose value is a few hundred ohms will give results. Hence the limitation of the circuit is that it cannot test high resistance components for continuity. One has to be judgemental in selecting the component for the test.
Assembling
In order to assemble the circuit for utility purposes, a ready-made PCB has been designed and given here. One can easily assemble the circuit on the given PCB without any difficulty. The copper track design can be etched on a copper-clad board for fabrication purposes. The PCB full view along with the component layout figure may be useful while assembling the components on the readymade PCB.
PCB full view
Component layout
Copper track
Conclusion
Definitely, this mini continuity tester is an indispensable test instrument for an electronics service technician. Nowadays this becomes students' favorite project. Please give your comments and suggestions for the improvement of the gadget.
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