Circuits & Schematics: power supply - 4

31. 30A AC soft starter (inrush current limiter)
    Hesam Moshiri
    Circuits Arduino Supply Microcontrollers Usage Atmel ATtiny13
    .. this AC soft starter that is equipped with a fail-safe mechanism. During start-up, the inrush current passes through a power resistor, and after a delay (adjustable between 1 ms to 1 s), a 30 A power Relay shorts the resistor and ...
    .. the logic circuit activates the fail-safe Relay that turns OFF the load to prevent any damage. 3 LEDs indicate the Supply, Normal, and Fault conditions. I selected the cheap ATtiny13 MCU as a controller. To design the schematic and ...
    May 20, 2026

32. Over-temperature micro-power alarm
    David A. Johnson
    Circuits Measurement Digital Texas Instruments CD4013B
    The circuit is powered for years by a single 3 volt lithium battery. It sounds an alarm when the temperature exceeds a certain point. With some minor changes the circuit could also be configured for an under temperature (freeze) alarm. The circuit ...
    May 14, 2026
33. Single switch controls sequential operation of multiple power supplies
    Jayapal Ramalingam
    Circuits Supply Texas Instruments LM393
    .. circuits manage multi-PSU powerup and shutdown sequences In projects containing digital and/or analog circuits, multiple power supplies are used, generally 5 V DC for digital circuits and 15 V DC for analog circuits. Some projects also ...
    .. 5 V DC for digital circuits and 15 V DC for analog circuits. Some projects also use 24 V or 48 V DC as the third power supply. In many cases, these power supplies need to be switched on in sequence, commonly 5 V DC first and 15 V DC ...
    May 12, 2026
34. Piezoelectric tap switch
    David A. Johnson
    Circuits Supply Digital Texas Instruments CD4013
    .. box, as a finger tap sensor. With each tap of a finger to the box holding the wafer, the circuit turns on and off AC or DC power to an external device. The circuit is powered by a 9 V battery and drives a single coil 5 V latching relay with ...
    May 7, 2026
35. Infrared remote control decoder & switcher using Arduino
    Hesam Moshiri
    Circuits Arduino Wireless Atmel ATtiny85
    .. programming of the microcontroller, please disconnect the programmer and restart the board (disconnect and re-connect the power). Then you can store the desired remote control keys (by pressing and holding the SW1). You can change any of ...
    .. to reduce the noise. FB1 and C11 block the input noise peaks. IC2 is the TS2937CW-5.0 regulator that prepares a fixed +5 V supply for the U1 and IC1. D8 indicates good supply provision and C8 and C9 have been used to reduce the ...
    May 7, 2026
36. ΔV_BE thermometer outputs 1 mV/°C without calibration or op amps
    Stephen Woodward
    Circuits Analogue Design Measurement NXP 74HC4053
    .. Some of my best friends are op amps. They embrace such a wide range of varied capabilities, including low noise, high power, micropower, zero-drift, RRIO, high speed, etc., that they’re easy to love. They tend to make analog ...
    .. This precision voltage reference converts Kelvin to Celsius. Speaking of variations that don’t spoil accuracy, the V+ supply, for example, can vary from 5 to 6 volts without affecting accuracy. Output impedance is roughly 2k, so ...
    May 7, 2026
37. I built a 100W stereo class-D amplifier using TPA3221
    Sagar Saini
    Circuits Audio Amplifiers Texas Instruments TPA3221
    .. a cliff. I want to drive my TPA3221 amplifier directly from the car battery in this case. So that it can actually push real power into real speakers, with clean audio and proper engineering behind it. The goal was simple: a compact, ...
    .. 4 ohms. 108 dB SNR which is better than most commercial amplifiers in this power class. 90% efficiency at full load. Wide supply range: 7 V to 30 V on PVDD. Built-in protections: undervoltage lockout, overcurrent and overtemperature. ...
    May 6, 2026
38. BJT is accurate sensor for absolute temperature in Kelvin and Rankine
    Stephen Woodward
    Circuits Analogue Design Measurement NXP 74HC4053
    .. and therefore on only the precision of R1 and R2. No other reference is required or relevant and any 2N3904 will do. The V+ supply, for example, can vary from 3 to 6 volts without affecting accuracy. Passive output impedance is roughly 10k. ...
    Apr 30, 2026
39. Battery switch
    Lapo Pieri
    Circuits Supply Texas Instruments LM5050-1 LM5050-2 CSD17501Q5A
    .. it chooses the one to connect to the load based on the voltage measured at their poles. It can also be used to switch DC power supplies. The growing demand for portable devices capable of working where there is no power grid or it is not ...
    .. 3 A. Figure 1. Generators with load. However, even without a load (as shown in Fig. 2), we can already notice that V 2 will supply V 1 with a voltage of: Therefore a good amount of the energy is wasted on the internal resistors of the ...
    Apr 28, 2026
40. Linearly variable two-wire loop current generator
    Jayapal Ramalingam
    Circuits Measurement Interfaces Texas Instruments LM124
    .. the current, and either LOAD1 (source) or LOAD2 (sink) can be connected. How does the circuit work? First connect a 24 V DC supply, a DC ammeter and a load resistor say, 200 ohms at the source or sink side. In field applications, this ...
    Apr 24, 2026

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