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12 Stage Neon Sequencer: Circuit Diagram & Build Guide
Circuit Diagram
Description
This design mirrors the neon indicator clock, substituting twelve neon lamps for LEDs. It’s powered by two high-capacity Ni-Cad cells providing 2.5 volts, ensuring continuous operation for approximately two weeks. The required high voltage (70 volts) for the neon lamps is produced by a compact switching power supply incorporating a 74HC14 Schmitt trigger squarewave oscillator, a high-voltage switching transistor, and a 10 mH inductor with high quality. Numerous small PNP transistors, possessing a Collector-Emitter voltage rating of 80 or greater, can be substituted. The inverter stage (pins 5,6) is superfluous and merely an additional component. A tunable low-frequency oscillator, fabricated using two of the inverter stages, generates the clock signal for the 74HCT393 binary counter. To ensure proper charging, the timing capacitor must be non-polarized; consequently, two 6.8 uF tantalum capacitors were connected in parallel, yielding roughly 3.3 uF. The 75K resistor in series with pin 1 acts as a current-limiting measure for the input protection diodes when the capacitor voltage surpasses the supply voltage. This resistor might be omitted when utilizing small capacitors at low voltages, yet it’s included as a safeguard. The binary counts are translated into one of twelve outputs via the 74HCT138 decoders, functioning identically to the 28-LED clock circuit. The sequence can be expanded to sixteen by removing the reset circuit and connecting pins 2 and 13 of the counter to ground.
More about components
The 74HC14 Schmitt trigger squarewave oscillator is a versatile integrated circuit utilized to generate stable, rectangular waveforms. It’s characterized by its ability to produce precise switching thresholds, making it ideal for timing circuits and oscillator designs. Its key features include adjustable hysteresis, allowing for reliable operation even with noisy input signals, and a complementary output, providing two distinct waveforms. This particular IC is frequently employed in applications needing controlled timing and signal generation. It also can be described as an analog switch integrated in a single chip. The 74HCT393 binary counter is a digital integrated circuit designed to count binary numbers. It’s based on a flip-flop structure, capable of storing one bit of information. When combined with other flip-flops, it can count sequences up to 16 bits. The 74HCT138 decoder is a digital integrated circuit that converts binary codes into logic levels. It’s essential for interfacing digital circuits with analog or other digital systems. The IC allows for the interpretation of binary inputs into a single output. Its design involves a series of logic gates that perform the decoding operation. Its implementation is used in applications requiring the conversion of binary data into specific logic states. These ICs are used in many different electronic components that control a flow of electrical currents.