The LED starts glowing as intensity of sound varies. This project can be used to measure the intensity of sound present in the room as sound intensity increase [[wysiwyg_imageupload::]]number of LED glows also increases. Circuit is based on LM324 which is 14 pin IC consisting of 4 independent operational amplifiers. The output voltage of LM324 is many times higher than the voltage difference between the input terminals of an op amp.LM324 IC is used as a comparator and when input voltage rises above the reference voltage, output is attained. When no noise or audio signals are present in the room, output voltage on pin 1 is zero as voltage on pin 2 is lower than that at pin 3. Since, the IC works as comparator, less voltage on pin 2 in comparison to pin 3 will not make the LED glow. Let’s find out the working of this interesting project.
90 Second Timer
This timer circuit project is used to switch on and off the device for a fixed interval of time. In this case, it is taken to be 90 seconds, meaning that the device [[wysiwyg_imageupload::]]periodically becomes on for preset amount of time and remains off for same period of time. It can be set with the help of a resistor and a capacitor.LM324 is able to provide high gains and works in a power efficient mode, thus one can power it using a battery. Using RC components for timing makes the calculations easier and also gives ability to alter the time period to a higher or a lower value. Continue reading to find out how the circuit is connected and how it works.
RF based Fire Alarm (Overheat Alarm)
This project presents another application of RF (radio frequency) communication. The capability of fire alarm circuit can be improved by incorporating an RF [[wysiwyg_imageupload::]]module. This way the temperature sensor and buzzer for alarm can be placed away from each other. This provides flexibility in installing various sensors at different locations in a building and thus overheating at a place (due to fire) would signal the buzzer to go on. This project about fire alarm circuit can be divided into four parts, namely, temperature sensor, comparator, transceiver part (RF module) and the output. In this circuit a temperature sensor (LM35) is placed at a certain place and its output is given to the negative end of a comparator. LM324 has been provided in the circuit for comparator. The positive end of comparator is connected to a preset, to set the reference temperature. As long as the output of temperature sensor is below the set reference, the output of comparator stays high.
Color distinguished using LDR/Color sensor using LDR
This circuit can be used to sense and differentiate between different colors. This project demonstrates the principle and operation of a simple color sensor [[wysiwyg_imageupload::]]using LDR. The circuit is divided into three parts: Detector (LDR), Comparator and Output. In this project, when light of a particular color falls on LDR, its resistance decreases and an output voltage is produced. This voltage is dependent on the intensity and wavelength of different color. For this we need to set reference voltage of comparator according to our requirement. Keep on reading to find out how the circuit is assembled and how it works.
Opamp LM324 as comparator using LDR
This project based on op amp comparator circuit demonstrates the principle of operation of op amp (operational amplifier) as comparator. A comparator [[wysiwyg_imageupload::]]compares two voltages fed to it and gives output correspondingly. This circuit finds application as intermediate circuit in numerous circuits where there is need to compare two voltages. This Op amp comparator circuit project uses opamp (IC LM324) as comparator. The output of the comparator is high if voltage at positive end is more than voltage at negative end and gives low output if voltage at positive end is lesser than negative end. Read more to find out how this op-amp comparator circuit works and how it can be constructed in an efficient manner.