Free electronic circuit design and schematic diagram
This simple circuit shown int the schematic diagram actives the switch using sound. We can use this circuit for various applications, such as automatic (sound-controlled) disco light or car’s LED light show. The Q1 amplify the audio from mic. The R1 is used to adjust the peak of signal to greater than about 0.7 volts, act as sensitivity adjuster. A […]
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This is a relay circuit that detect the presence of sound to activate the relay. You can use this sound-controlled relay as voice operated switch, light control, toys, or any other application that can be controlled by a switch. Just replace the switch with this relay and now you have a sound-controlled device. This circuit uses a 741 operational amplifier […]
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This is a audio-controlled lamp circuit. This circuit requires low voltage input such as pre-amplifiers, tone control, or general audio line level output. It’s also possible to feed the input with signal from small power amplifier output, or high power amplifier witk low volume level. The characteristic of lamp dimming (incandescent lamp) will look like coming from proportional controller since […]
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This is a Single-cell microphone amplifier circuit. This circuit produce a voltage gain of 60 dB at 500Ω load with bandwidth 5kHz. This circuit can provide a 60dB gain up to 10kHz if it is unloaded. This circuit has a 10 kΩ input impedance. This circuit cannot neither produce an output swing closer than 800mV or below 150mV to the […]
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Microphone can’t be directly connected to a power amplifier because the signal is too weak. Standard audio power amplifier accept about 1 Vrms to give a full volume (maximum power), and off course there’s such microphone has such high level output. To provide signal with high enough amplitude, we can use a pre-amplifier circuit shown in the schematic diagram below: […]
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Door intercom is very useful for home security. If you receive a door knock or door bell/alarm, you can push this intercom knob and ask the guest to identify his/her self, before deciding to open the door to welcome. Here is the schematic diagram of the circuit: To install this door intercom, except for right side speaker, you should place […]
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Microphone pre-amp is a very simple circuit, most all low noise op-amp will be sufficient for this circuit (TL071, TL082, OPA371, NE5534, etc). This circuit will be suitable for dynamic microphone, electret microphone (or a condenser microphone with active circuit inside). A condenser microphone (without voltage bias source) won’t work for this circuit. If you want to use it, you […]
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