Free electronic circuit design and schematic diagram
Normally, Theremin works by detecting hand proximity using capacitive coupling method. A Theremin circuit shown in the schematic diagram below use different method to control the pitch. The oscillator of this tone generator, both the volume and frequency are controlled using LDRs, a light sensitive electronic component, so we can call this circuit an optical Theremin. Look at the following […]
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A two tone effect very much alike cuckoo sound is generated by this circuit. We can use this circuit for door-bells or other purposes thanks to a built-in audio amplifier and loudspeaker. Used as a sound effect generator, it can be connected to external amplifier, tape recorder, etc. The built-in audio amplifier and loudspeaker may be omitted and the output […]
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This is a light alarm circuit. This circuit uses Light dependent resistor (LDR). When there is no light fall on the LDR, the transistor driving the speaker is not turned on, because its resistance is high. When the LDR receives light, its resistance decreases and the collector of the second transistor falls. The first transistor turn off slightly, via the […]
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This is a signal injector circuit. Signal injector is important tool for troubleshooting your electronic circuits. As an example, this circuit can be used to test amplifier circuit. Here is the schematic diagram of the circuit: This circuit also a lot of harmonics. By connecting the ground clip to the 0v rail and move through each stage, starting at the […]
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This circuit is a simple buzzer circuit and it called novel buzzer. It only uses a relay in series with a small audio transformer and speaker. The relay will operate via the transformer primary and closed relay contact, when the switch is pressed. The normally closed contact will open as soon as the relay operates, removing power from the relay, […]
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Metronome is very important tool if you studying music playing. There are mechanical metronome device in the past, but today, electronic metronome is much more popular since it can be very simple, compact/small, reliable, and also has the most interesting feature: cheap. Here is one example of the electronic metronome schematic: Parts: C1 1 uF 63V Polyester Capacitor C2 10nF […]
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This alarm siren circuit produce warbling sound, you can use it in your toys or in security alarm. The circuit use two 555 IC oscillator. In this alarm siren circuit, the first oscillator is employed to produce audio frequency. The second oscillator is employed to produce a modulating signal. This modulating signal make this alarm siren generates warbling sound. Here […]
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