The IC is nothing but a small chip containing the very large and complicated circuit. The different circuit components are generated in a semiconductor material with the help of CMOS Technology. An IC (Integrated Circuit) can not be repaired and neither it had to be since they come in very cheap cost in comparison to the circuitry they contain. The Question arises in front of us is that how to test an ic and when should we throw or replace the IC.

There are four ways to Test an IC and if the IC is fine and in proper working condition then it has to pass all the four conditions.

Shorting Condition

The purpose of this method is to test if there is a short circuit inside the IC

  • Set your multimeter to the continuity mode.
  • Connect all of the pins altogether from one of the side in IC to the multimeter cable.
  • Take the terminal-cable from multimeter and connect it one by one to each of the pins of another side separately.
  • If the beep sound occurs of there is a continuity in more than 50% of the combinations then there is a good chance of the IC to be shorted from inside.

Leakage Condition

In this Method you have to test an IC that weather the package is damaged or is blown. Take the observation of the IC from each of the sides possible, if you see even a little crack, burned mark or its broken from either side then the IC is surely to be Damaged or Leaked.

Heating Condition

In the method we test if an IC is getting overheated unnecessarily.

  • Give the voltage supply to the IC as per its operating condition or if its on board then turn its supply on.
  • Touch the IC with your finger just by starting the voltage supply to it.
  • Notice if the IC is getting heat up as it naturally gets or if you are not able to touch it after few 10-12 seconds.
  • If the ic is getting heat up extremely faster then the IC is surely to be damaged.

Input and Output Supply Condition

In this we have to test an IC if the output voltage from signal pins of the IC are as per defined voltage or they differ from the specifications. Just an example of IC 74VHC112 which has Dual JK Flip Flop with Preset and Clear mode. The supply voltage to the ic that is Vcc could be 0.5 V to 7V and the output from the Signal/Data pins could be either +0.5V or – 0.5V.

Connect the Vcc to input Voltage and Ground to the Ground of negative of the supply.

Try the different inputs to the flip flop so that you can get logic “1” at-least once on each of the output pins.

Measure the voltage of the pin when you’re getting “1” as a logic output.

If the voltage is very much different from 0.5V then the IC is not functioning as its best.

If You found any of the above four conditions while testing an ic then there are very much chances that your IC is not functioning as it should be and you may need to replace your IC

Farhan Sheikh is an Electrical and Electronics Engineer passionate about making circuits and digital electronics. He Runs a blog EEE Projects which provides General information about Electrical – Electronics Topics and Projects.


    An electromagnetic relay in its switching principle is a mechanical switch which is operated with a low-power DC voltage. The switch part is used to control high power circuits.
  2. SPDT RelayRelay design
                  The SPDT relay is mainly made up of :1. Movable armature
    2. Control coil
    3. Switch contact points
    4. Coil terminals
    5. Common terminal


    RELAY SPDT (single pole double throw) has a total of five terminals Out of these two are the coil terminals. A common terminal is also included which connects to either of two others. When a voltage is applied to the control circuit, the coil traversed by a current will create an electromagnetic field; this latter is capable of moving a metal element called movable armature.

  3. Experimentation*.Objective:
    Make circuit by using a relay in the DCAClab simulator.*. Equipment:

    • Battery (Electromotive Force E = 1.5 v , Internal resistance r = 1 Ω)
    • Switch K1
    • Coil (r1 = 1Ω)
    • Relay Switch
    • Lamp (r2 = 1Ω)
    • Fan

*. Experiment 1: order a single circuit

  • Experimental mounting
  • Interpretation
    • Level 1
      1st case: Relay at rest
      The switch K1 open ( I1 = 0  ) ⇒K2 at the position (1), consequently  the circuit B is open : I2 = O , so the lamp L is off .
      2nd case: Relay at work
      The switch K1 is closed ( I1 ≠ 0 )⇒Kat the position (2), consequently  the circuit B is close : I2 ≠ 0 , so the lamp L is on .
    • Level 2_ calculating the intensity of the current I1:Ohm’s law: Ue= r1 I= E – r I1
      So  I1  = E/ (r1  + r)  = 0.04838A ≈ 48.38 mA


      _ calculating the power P1:

      P1 = E I1 = 1.5 x 0.04838 = 0.07257 w

      _ Value of the intensity I2:

      By using the characteristics of the lamp we find I2 = 1.456 A

      _ calculating the power P2:

      P2 = E I2 = 1.5 x 1.456 = 2.184 w


      The relay can be used to control a high power circuit by a low power circuit.

  • Experimental verification using the DCAClab simulator

*. Experiment 2 : order 2 circuits 

  • Experimental mounting1st case: Relay at restThe switch K1 is open ⇒K2 at the position (1), consequently:
    • The circuit B is closed, so the lamp is on.
    • The circuit C is open, so the fan is off.
  • Experimental verification using the DCAClab simulator

    2nd case : Relay at workThe switch K1 is closed⇒K2 at the position (2) , consequently  :

    • The circuit B is open, so the lamp is off.
    • The circuit C is closed, so the fan is on.
  • Experimental verification using the DCAClab simulator

the end.


When it comes to experiment with colorful LEDs, students finds it very interesting in using them to build electronics circuits to indeciate current.

Because its a priority to use realistic graphics with DC/AC Virtual Lab, we have implemented the LED component with varius colors to choose from, this would be very interesting for students to start using LEDs and experiment with!


Students can now play with two handly controls, that are TIME/DIV and VOLTS/DIV to set the time base and volts per div in the oscilloscope.

Its easy to add several oscilloscopes that reads the same voltage source, and compare readings while playing with time/div control or volts/div.