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March 5, Arlington, VA (2025)

09/05/2025

a temperature-controlled automatic fan circuit designed for 12V systems, using an N-channel IRFZ44N MOSFET as a switch. A 3.9kΩ resistor and a 5kΩ NTC thermistor (temperature sensor) form a voltage divider that controls the MOSFET's gate. As the ambient temperature increases, the thermistor's resistance decreases, altering the gate voltage and turning the MOSFET on when a threshold is reached. This allows current to flow to the 12V cooling fan, activating it automatically. The system is powered through a 12V input, making it ideal for applications such as electronics cooling or battery temperature regulation where automated thermal management is needed.

09/05/2025

This diagram illustrates a heavy bass amplifier circuit built around the TDA7388 integrated amplifier chip, powered by a 12V DC supply. The TDA7388 is a quad-bridge amplifier commonly used in car audio systems due to its high output power and low distortion. The circuit includes key components such as 10nF and 100nF capacitors for input filtering and decoupling, along with resistors (10kΩ and 100kΩ) and a 470nF capacitor to stabilize the gain and frequency response. The input section accepts stereo signals (left, right, and ground), which are amplified and routed to four connected speakers labeled OUTPUT L1 and OUTPUT R1 for a robust and deep bass output. This configuration delivers enhanced sound performance suitable for automotive or DIY home audio systems.

09/05/2025

a basic 12V to 220V square wave inverter circuit, which converts low-voltage DC input to high-voltage AC output using a CD4047 IC. The circuit features a center-tapped transformer (12-0-12V, 2A) that steps up the voltage from 12V DC to 220V AC, producing a square wave output. The CD4047 is configured as an astable multivibrator, generating 50/60 Hz oscillations that drive the transformer through switching transistors (not shown but implied). A capacitor (22µF) and a variable resistor (potentiometer) are used to adjust the frequency of the oscillator. This simple inverter design is ideal for low-power applications where a pure sine wave is not critical.

09/05/2025

presents a simple AC to DC power supply circuit designed to convert 220V AC to 12V DC at 3A output. The setup utilizes a step-down transformer (220V AC to 12V AC, 3A rated) to reduce the high-voltage AC input to a safer 12V AC. The stepped-down AC voltage is then rectified using a pair of IN3408 diodes configured in a full-wave rectifier arrangement. Following rectification, a 4700µF/25V electrolytic capacitor is used to filter and smooth out the rectified voltage, resulting in a stable DC 12V output. This compact and efficient circuit is ideal for powering 12V DC devices from a standard AC mains supply.

09/05/2025

a basic single-transistor inverter circuit designed to convert 12V DC to 220V AC, utilizing minimal components. The circuit employs a powerful NPN transistor (C5200) configured in a self-oscillating mode with a 220µF capacitor and a 1kΩ base resistor to drive a 12-0-12V step-up center-tapped transformer. The 12V DC supply from a battery energizes the primary winding of the transformer, and through oscillation created by the transistor switching, it induces a 220V AC output at the secondary winding. This straightforward design is suitable for low-power applications such as lighting and small appliances where pure sine wave output is not necessary.

09/05/2025

the H-Bridge motor control circuit, a widely used configuration for controlling the direction of a DC motor. The schematic shows four switching transistors arranged in an H-pattern, with the motor connected at the center bridge. By toggling the inputs INA and INB, the circuit can control current flow through the motor, allowing it to rotate clockwise, counterclockwise, or stop via electronic braking. The accompanying truth table explains the logic: for example, setting INA = 0 and INB = 1 drives the motor clockwise, while INA = 1 and INB = 0 reverses the polarity, making the motor spin counterclockwise. This design is fundamental in robotics and embedded systems for bidirectional motor control.

09/05/2025

This is a simple and effective short circuit tester circuit diagram used for electronics troubleshooting. The setup includes an "ON" LED (green) indicating power status, a "SHORT" LED (red) that lights up when a short circuit is detected, and a buzzer that provides an audible alert in such cases. The system is powered by a battery (not shown) connected through a DPDT switch, and current flows through two resistors (1KΩ to 1.3KΩ range) to limit excessive current and protect the components. A reset push-button allows the circuit to return to its default state after a fault is detected. The compact design and use of basic components make it ideal for electronics enthusiasts and repair technicians to identify short circuits quickly on PCBs or wiring systems.

09/05/2025

a homemade water level indicator system designed to visually monitor the water level in a storage tank using a series of LEDs. The system uses four different colored LEDs to represent water levels at 25%, 50%, 75%, and 100%, each connected in series with 470-ohm resistors and NPN transistors (BC547). As the water level rises, it completes the circuit between the positive voltage and the transistor bases, activating the corresponding LED to indicate the level. The use of transistors allows for current amplification and reliable switching. This simple, cost-effective setup operates on a 5V DC power supply and provides an efficient way to monitor tank levels for household or agricultural applications.

09/04/2025

This circuit diagram illustrates a DC voltage regulator using the LM317 adjustable voltage regulator IC, capable of converting an input voltage of up to 28V DC to a variable output voltage ranging from 1.5V to 24V DC. The LM317's output voltage is controlled by a voltage divider formed using a 270-ohm fixed resistor and a 5K potentiometer, allowing precise adjustment of the output. Two electrolytic capacitors (1000µF at the input and 10µF at the output, both rated at 63V) are used for filtering and stabilization, ensuring smooth voltage regulation and reducing ripple. This setup is ideal for powering a wide range of electronic devices that require a specific DC voltage, offering both reliability and flexibility in various DIY and professional applications.

09/04/2025

This circuit diagram presents a non-isolated capacitive power supply designed to convert 220V AC to 12V DC using minimal components. It utilizes a 105K 400V (0.1µF) metalized polyester capacitor for current limiting, followed by a 1MΩ resistor for discharge protection and safety. The AC input is then fed into a 4A bridge rectifier (BR) that converts the AC to pulsating DC. A 1000µF electrolytic capacitor smooths out the rectified DC output to provide a relatively stable 12V DC supply. This compact and cost-effective solution is ideal for low-power DC applications, but it must be handled with caution due to the direct connection to high-voltage AC mains, and it lacks isolation, making it unsuitable for applications requiring electrical safety and protection.

09/04/2025

This circuit diagram showcases a compact high-voltage DC boost converter designed to power an auto volt tester backlight or similar devices, delivering an output of approximately 90V from a 5V DC input. At the heart of the circuit is a TIP3055 NPN power transistor, driven through a 1kΩ base resistor, which switches current through an EMI filter inductor to generate high-voltage pulses. These pulses are rectified by a fast-recovery diode (FR154) and smoothed by a 160V, 22µF capacitor, while a 220Ω resistor ensures controlled current flow. The system steps up the low voltage input using inductive switching, allowing the connected multimeter or volt tester to be backlit with high voltage, making it ideal for DIY electronics applications requiring compact and efficient high-voltage generation.

09/04/2025

This circuit diagram illustrates a 100-watt DC to AC inverter using the IC CD4047, which is configured in astable multivibrator mode to generate alternating pulses that drive the MOSFETs (IRFZ44N or FDP55N06). These MOSFETs switch current through the center-tapped transformer (12-0-12V, 5A), stepping up the 12V DC input to a 220V AC output. The circuit includes key components such as a 100k potentiometer and a 390k resistor to set the oscillator frequency, along with 220-ohm gate resistors for MOSFET protection. A 1N4007 diode and 0.01µF capacitor offer power input protection, while a 0.1µF/600V capacitor across the output provides noise filtering. A 1N5408 diode ensures back EMF protection. This inverter is suitable for powering small AC devices from a 12V battery, ideal for emergency power or portable applications.

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