The simple 555 Alarm sound circuit that you are seeing. We have many circuits that can make the alarm sound. But IC-555 timer is popular forever. It is easy for a beginner as buzzer sound.
IC-555 is a pulse generator, high frequency. Then, the PNP transistor boosts the current up to output speaker.
How it works
The 555 alarm sound circuit diagram
In the circuit, First, get a power supply, 9V battery to the circuit. IC1 works in A Stable Multi Vibrator mode. It makes high frequency out of pin 3.
Which the output frequency is determined by the value of R1, R2, C2.
Especially C2, If it is high value, the output is low frequency, bass sound.
The sound of pin 3 flows to R3 to limit current for Q1. The Q1 is the amplifier to drive the speakers, 8 to 32 ohms.
Parts you will needs
Q1—BD136,BD140 PNP transistor
C1—100uF 16V Electrolytic capacitors
C2—0.01uF 50V Ceramic Capacitors
C3—0.1uF 50V Ceramic Capacitors
R1—100K 0.5W resistors
R2—4.7K 0.5W resistors
R3—100 ohms 0.5W resistors
R4—33 ohms 0.5W resistors
Speaker 8-32 ohms
We have many ways to build the buzzer sound circuit. We used to build them with the transistors. But now we like to use the IC-555 timer more than. ? Because it easy,small amount,and cheap. We have 3 circuit example below.
Page Contents, Click
Danger beep circuit
This is danger beep circuit. It use 555 integrated number circuits build to are a stable mutivibrator that be valuable duty cycle 5% driver loudspeaker 8ohm 0.25W sizes. By change transistor BD136 will get danger beep use make person penetrate a hole is frightened or call for the interest from a neighbor for asks for help. Because of use part a little , then have small-sized and use current just 50mA from a place turns on the power supply 9Volt only.
Tone Burst Generator
Friends take an interest try build Tone Burst Generator be simple is. Try this circuit like sure because useIC 7555 , highly popular again. Assure that not sure difficult press the the secretariat of the senate S1 a loudspeaker will utter to come out immediately. When liberate S1 already the sound may loud again next many second. The C2 and R4 control time drag. The C1 control the frequency.( Use the integrated circuit IC 7555 use power source a little more IC 555 very )The detail is other see in the circuit request have fun Tone Burst Generator please sir.
Annoying high pitch noise generator
This is a simple high pitch noise generator circuit. It has a timer oscillator with a frequency variable from 15khz – 30khz.
The circuit can be mounted in a plastic box like I have done. The good thing about high frequency sounds is that it is very hard to find where they are coming from. Also, the noise is very annoying and irritating. The crystal speaker is the creamy coloured thing at the bottom of the photo on the left.
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