Electronic Circuits and Diagram-Electronics Projects and Design

Description. Here is a very useful lamp flasher circuit using the famous adjustable voltage regulator IC LM317T. LM317 can source up to 1A of current and so up to 12W lamps can be used with this flasher. Such a circuit finds huge application in automobiles. The frequency of the flashing depends on the value of resistors R1 to R3 and capacitors C2 to C4.With the given values; the flashing rate is around 5 flashes per second. Circuit diagram. Notes. The circuit can be assembled on a Vero board. Use 12V DC for powering the circuit. Use a proper heat sink…

Description. Many audio mixer circuits have been published here. But I think, this one is the simplest of them. This very simple audio mixer circuit uses only one transistor. The base emitter junction of the transistor is biased by the diodes D1 and D2.The signals to be mixed are directly coupled to the base of Q1.Each input lines are current limited by using a 33K resistor. With the used component values the collector current is around 1mA. Circuit diagram with Parts list. Notes. The circuit can be assembled on a Vero board. The circuit can be powered from 15V DC….

Description. This powerful lamp flasher circuit is ideal for use in automobiles. The circuit is based on IC LM395 (also known as super transistor) which is a very powerful integrated monolithic power transistor with features such as thermal overload protection, current limiting etc. In fact this IC is almost indestructible.The IC can handle currents up to 1A and switch 40V in less than 500 nano seconds. Resistance R1 and capacitor C1 determines the frequency of flashing. With the stated values flash rate is around 1 flash per second. Circuit diagram with Parts list. Notes. The circuit can be assembled on…

Description. Here is the circuit diagram of a simple two transistor alarm circuit that can be operated from a 9V PP3 battery. Here the two transistors are wired to form an oscillator whose frequency increases when switch S2 is pressed and decreases when S2 is released. In order to attain this the base of Q1 is biased from an RC circuit comprising of R2 and C1.When S2 is pressed C1 is charged through the resistor R2.As the voltage across the C1 increases the time constant decreases and this results in an increases in the frequency. When S2 is released capacitor…

Description. The circuit given here produces an alarm similar to the police siren. When you press the push button switch S2 capacitor C1 will charge and this will make the transistor Q1 to ON slowly. When the switch S1 is released the C1 will discharge and the transistor Q1 will become OFF slowly. When the Q1 is switched ON, its collector voltage falls and makes the transistor Q2 ON. The capacitor C2 will be charged almost to full supply voltage. This results in an increase in the collector-emitter voltage of Q2.This change in voltage is coupled to the base of…

Description. The circuit given below is of a simple audio amplifier that can deliver 12W to an 8 Ohm speaker. Op amp IC TL081 is used as the preamplifier here. Actually any opamp with matching power supply ratings can be used instead of TL081.Transistors Q1 and Q2 (TIP125 and TIP120) comprises the power amplifier stage. Output is taken from the collector junction of two transistors. Circuit diagram. Notes. The circuit can be assembled on a Vero board. Heat sinks are recommended for the transistors. A +15V/-15V dual DC power supply can be used to power the circuit. It is better…

Description. This is the circuit diagram of a simple three transistor audio amplifier that can deliver around 100mW power to a 25 Ohm speaker. The diodes D1 and D2 provides a constant bias voltage for the transistors Q1 and Q2.The transistor Q1 works as a preamplifier. Transistors Q2 and Q3 drives the speaker. The type no of the transistor is not very crucial here. You can use any NPN transistor for Q1, Q3 and any PNP transistor for Q2.Any way the minimum collector current capacity of the transistors must not be less than 100mA.The circuit will work well with an…

Description. This simple circuit produces a beeping sound that lasts for around 3 seconds whenever you make a whistle. The CMOS Hex inverter CD4049 is the heart of this circuit. Out of the six inverters in CD4049, U1a is wired as an audio amplifier which amplifies the signal picked up by the microphone M1.The U1b is wired as a band pass filter with center frequency around 2KHz.The filter is necessary in order to pass the frequency corresponding to whistling sound and suppress all other frequencies .If the filter is not there, the circuit could easily get false triggered.U1d is wired…

Description. Here is the circuit diagram of a simple 24W mono amplifier using IC TDA1516.The TDA1516 is an integrated class B power amplifier in a 13 pin SIL package. The IC has many useful features such as short circuit protection, load dump protection, thermal protection, reverse polarity protection etc. Here the IC is wired in BTL mode to deliver 24W of power into a 4 ohm speaker. This amplifier can be operated from a 12V DC supply and this makes it suitable for car audio applications. Circuit diagram with Parts list. Notes. Assemble the circuit on a good quality PCB….

Description. Given below, is a very simple circuit that can be used for charging car batteries. In this circuit there is facility for monitoring the charging current and voltage. The circuit is based on the IC MC78T12ABT from Freescale.The IC is nothing but a 7812 in TO-3 package with 3A capacity. The transformer T1 steps down the mains voltage and diodes D1&D2 does the job of rectification. Capacitor C1 does the filtering and C2 acts as a decoupling capacitor. The ground terminal of IC1 is lifted to 2.1V using the diodes D3 , D4 and D5 . So the output…