Emergency Stop Schematic Circuit Diagram

The big fear of every developer of a microcontroller or computer-driven control system is that the computer or controller could crash while it is in the middle of controlling something and that the output signal will remain on ‘full throttle’. In this scenario, motors could continue to spin faster and faster or a heating element[…]

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Crystal Pulling Schematic Circuit Diagram

In microcontroller circuits, quartz crystals provide the highest accuracy for keeping everything on frequency. With frequency and time measurement (and for commissioning master clocks) fine adjustment of crystal oscillators may also be necessary, so we will now investigate in detail how crystal frequencies can be ‘pulled’. Although we have taken the ATtiny25 AVR microcontroller from[…]

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Wideband Waveform Generator Schematic Circuit Diagram

This circuit is designed to provide a wideband digital sine wave signal source. Its main feature is that because it synthesizes the signal in 32 steps, no low-pass filter is required to suppress the odd harmonics. A well-known method for synthesizing a sine wave under control of an input frequency is to apply a low-pass[…]

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±5-V Voltage Converter Schematic Circuit Diagram

Asymmetrical ±5 V power supply is often needed for small, battery-operated operational amplifier projects and analog circuits. An IC that can easily be used for this purpose is the National Semiconductor LM 2685. It contains a switched capacitor voltage doubler followed by a 5-V regulator. A voltage inverter integrated into the same IC, which also[…]

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Noise-Driven Sound Generator Schematic Diagram

Noise-Driven Sound Generator Schematic Circuit Diagram

The sound generator shown here uses its built-in loudspeaker as a microphone when it is in the standby state. As soon as it detects a noise that exceeds an adjustable threshold level, it becomes active. This small, clever circuit can be used as an alarm generator that reacts to noises. You can also use it[…]

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