Electronic Circuits and Diagram-Electronics Projects and Design

Description. The main part of this doorbell circuit are two NE555 timer ICs.When some one presses switch S1 momentarily ,the loud speaker sounds a bell tone as long as the time period of the monostable multivibrator built around IC1. When the switch S1 pressed, IC1 is triggered at its pin 2 and output pin 3 goes high for a time period previously set by the values of POT R4 and POT R5.When the output ofIC1 goes high it resets IC2 and it starts to oscillate to make a bell sound through the speaker.The IC2 is configured as an astable multivibrator…

Description. This is a compact electronic siren circuit based on three transistors.This circuit is suitable for in corporating with other alarm or siren projects such as burglar alarms, automatic factory sirens etc or a simple push to on alarm. The  electronic siren circuit given here  is  based on a complementary transistor pair consisting of Q2 & Q3 (BC557 & BC 37)  wired as an astable multivibrator oscillator,which directly drives the speaker.The transistor Q1 is used to provide a full charge on capacitor C2 when power is turned ON. When push button switch S1 is pressed , the capacitor C2 slowly discharges through resistor R8.This…

Description. Here is the circuit diagram of a simple yet interesting mini organ based on UJT 2N 4891 (Q1). You can produce the desired sound by pressing each pushbuttons. You have also the option to set each push button to produce the desired tune you want. The circuit is based on a UJT oscillator who’s frequency is determined by the Presets R6 to R13 (one at a time) and capacitor C2. The transistor Q2 drives the speaker to produce reasonable sound output. For each pushbutton press the corresponding preset will be added to the circuit, and the UJT oscillates in…

Multi Tone Alarm Description This is a simple and easy to build multi tone alarm circuit that can be used in burglar alarms or sirens. The circuit is based on dual op amp MC1458 and  LM 380. The two op amps inside the MC 1458 are used to produce square and triangular waves.LM 380 is used to amplify the output.The first op amp IC1a is wired as an astable multi vibrator and second op amp IC1b is wired as an integrator , to make the square wave triangle. The two output square ans sine can be selected using switch S1…

Simple Sound Generator Circuit Description This is a real scream generator circuit suitable for any purpose like alarm or car horn.The circuit is based on two transistors Q1 and Q2.When you press the switch S2 the siren starts up moving to a high frequency.When the switch is released the tone slips down until you shift it up again by pushing the switch S2. Sound Generator Circuit Diagram with Parts List. Notes. Adjustment of tone quality can be obtained by different values for C2. If the alarm oscillates before S2 is pressed.The transistor is leaky, replace it. S1 can be used…

Description. A dual tone train horn simulator circuit can be made using two NE 555 timers connected in cascade.Here instead of using two NE 555 timers a single NE 556 timer is used which is a nothing but two 555′s in one package and each timers work independently.Switch S1 can be used to start the horn.The circuit is simple and low cost but works greatly. Circuit Diagram & Parts List. Notes Use a 9V DC power supply or battery for this circuit. Assemble the circuit on a good quality PCB or common board.Constructing a bread board prototype is recommended. We…

Doorbell Circuit Description Here is a simple and easy to build doorbell circuit using IC UM 66.The  details of UM 66  is given in the older post “Melody Generator using UM 66″. This is a slight modification of that circuit.In the previous circuit you have to keep the switch pressed for making the IC play the full music.Here if once the push button is pressed C1 is charged and the transistor Q2 will keep the IC playing the music till it ends.The time for the IC to play depends on discharging time of C1  which can be set by R1.Set…

Melody Generator Circuit Description Here is a simple melody generator circuit you can make using an IC.The  UM66 series are CMOS IC’s  designed for using in calling bell, phone and toys. It has a built in ROM programmed for playing music. The device has very low power consumption.Thanks for the CMOS technology.The melody will be available at pin3 of UM66 and here it is amplified by using Q1 to drive the speaker.Resistor R1 limits the base current of Q1 within the safe values.Capacitor C1 is meant for noise suppression. Notes Power supply  must be between 1.5V & 4.5V .Do not…

High Power Siren Circuit Description. This article is all about a comparatively strong siren circuit useful for any purpose.A complementary transistor pair (BC 557 & 337) is arranged as an oscillator, directly drives the speaker.Transistor Q1(BC 557) is used to provide full charging of capacitor C2.When P1 is pressed, C2 discharges through R8 and the circuit starts oscillating at a low frequency that increases slowly until a high frequency steady tone is reached and it is kept.When P2 is released C2 starts discharging and and output frequency slowly decreases.When C2 is charged fully the circuit stops oscillations. Tips. Adjust the…

Tone Generator Circuit Description Here we present a simple and low cost tone generator circuit, a ding dong bell suitable for calling bell purposes.It is made around IC 8021. It is an 8 pin IC but only four pins are shown here. 8021 has an in-built circuitry to produce ding dong sound each time its pin 3 is pulled low. The sound is stored in a 4 bit ROM. A complementary-pair, two-transistor amplifier is used to amplify the sound to a fair level of audibility. A piezoelectric tweeter or an 8-ohm, 500mW speaker  can be used at the output. Each…