23-02-2013, 01:07 PM
IC Tester
IC Tester.docx (Size: 122.29 KB / Downloads: 67)
INTRODUCTION
Although ICs 741 and timer 555 are rare and expensive these ICs are frequently used ICs even by an average hobbyist and electronics students. They are very versatile and damage resistant too. Therefore we have designed the IC tester for timer IC 555 And Op-Amp IC 741
The tester described here test both the ICs [Timer 555 and Op-Amp 741] instantly. The circuit here uses only a few resistors, switches, sockets and capacitors which cost around $3 including the PCB and the 7-segment display. The tester we design is equally useful for a factory and the student of electronics.
Circuit Description
Form the circuit diagram it is clear that the heart of this tester is the astable multi vibrator formed around 1C 555 which is approximately 2 Hz frequency. So, the output LED D1 (connected through link a and b snow in the circuit) blinks at a rate of 2 Hz if the IC 555 inserted in the socket works well.This output at pin 3 of IC 555 is also given through a DPDT (Double Pole Double Throw switch) to the pins2 and pin3 of IC 741 op-amp. The switch S2 selects the inverting or non-inverting input of the IC 741 . In this way the LED D2 ( connected through link c and d snow in the circuit) also blinks at of 2Hz rate if the IC 741 inserted is OK. If S2 selects inverting mode, then D1 and D2 blink alternately and if S2 selects non-inverting mode then D1 and D2 blink simultaneously. You may use 3V to 12V DC supply voltage safely. However, 9V DC is recommended.
More About circuit
As an interesting feature which gives a digital display without any confusion, you may use a common anode seven segment display. With op-amp IC 741 in inverting mode, the display shows 7 and 5 alternately. In the non-inverting mode it shows 9 and 0 alternately.
Both, the two LEDs and digital display options are given circuit diagram. You may use a common anode display having a damaged decimal dot and / or segment ‘e’ which are not used here
You may also use a common cathode display here by just interchanging the connections of common cathode from positive to the negative of the supply on the PCB near the switch S2. Similarly, interchange the connections of R7 and R8 from negative to positive of the supply.
PCB Layout
PLEASE NOTICE
It has been noted that when both IC 741 and 555 are faulty or in non-operating condition, the display shows 7 (but there is no change in the display while changing the switch S2), and when IC 555 is working and 741 is in non-operating condition the display shows 5 and 7 alternately and when IC 555 is not working but 741 is alright, then display shows 7 in inverting mode and 7 in non-inverting mode, but does not flash.
Versatile Digital Teste
It is difficult to detect the fault and troubleshooting digital circuits. Here is a simple and versatile circuit of digital tester for detection of condition of the components and also indicates the nature of defect.
Circuit description of versatile digital tester
This whole circuit of versatile digital tester is designed and fabricated around CMOS hex inverter buffer CD4049 containing six independent inverters (a – f). Where inverter (a) form basic integrator. Inverter B and C form the Schmitt trigger. Preset VR1 & VR2 is used to controls the frequency of the square wave oscillator and adjust the duty cycle to 50% respectively. The output of each inverter is fed to another inverter. Inverters d with e produce complementary output. A.C. output is obtained from complementary pair (inverter d and e) used to drive two LEDs (LED1 and LED2) where resistor R6 is used as current limiter of LEDs.
Inverter f is designed to detect logic state where LED3 and LED4 indicate high and low logic state respectively and is depends upon logic condition at probe P5 with respect to probe P6. Transitional point (where the LEDs just switch off) is adjusted by preset VR3.
Generated frequency from versatile digital tester is taken from probe P1 and P2 and is set by preset VR1 where frequency range of 10 Hz to 1 KHz in LF position and 1 KHz-70 KHz in HF position. The LF and HF position is decided by switch SW1¬.
Probe P3 and P4 is used to test semiconductor and its direction (forward bias and reverse bias). The forward bias of semiconductor is decided with LEDs direction. Either glowing LED indicates functional order and polarity. Resistive component can also be tested through probe P3 and P4, glowing both LEDs indicate component is functioning.
Probe P5 and P6 is used to test logic state where probe P6 is connected to ground of the circuit under test. Supply voltage must be 6V.