Circuits & Schematics: power supply

1. Phantom-powered solid-state linear airflow sensor
   Stephen Woodward
   Circuits Measurement Texas Instruments TLV2197 LM7905
   .. Darlingtion transistor pair linearly senses airflow using just two wires for both power in and signal out. Suppose we take a common TO-92 transistor and heat it to a constant temperature differential ...
   .. handy for air flow measurement. Maybe even moreso if it needed only a simple two-wire connection for both (phantom) power supply from, and signal delivery to, the supporting electronics. Please see the Related content listings below for a ...
   Aug 11, 2026

2. Push to increase, decrease a digital potentiometer
   Jayapal Ramalingam
   Circuits Digital Analog Devices AD5220
   .. by one step. Similarly, each “DEC” (decrement) push button press decreases resistance by one step. The power supply and ground pins of the various ICs are not shown in this schematic. This simple design uses only two ICs ...
   Aug 11, 2026
3. An off-line power supply
   Gavin Watkins
   Circuits Supply Texas Instruments LM317
   .. as it is only 50% efficient, and any dropped battery voltage will be dissipating as heat. However, assuming renewable power generation is used as the source, this would prove a more environmentally friendly solution compared to using ...
   .. around an LM317 linear voltage regulator in a nice black plastic enclosure sold by Maplin Electronics as a “power supply” box. The NiCd battery hadn’t been used for over 20 years, so this project would be a repurpose. ...
   Jul 29, 2026
4. Method provides fast, glitch-free isolation of I²C and SMBus signals
   Mark Thoren
   Circuits Interfaces Microcontrollers Usage Broadcom HCPL-2300
   .. 2 C is a popular serial protocol for power controllers, ADCs and DACs, EEPROMs, and other devices. In certain data-acquisition and power-control ...
   .. fight each other and form an oscillator (Figure 3). The characteristics of this oscillation depend on pullup resistance, supply voltage, and capacitance data lines. (Removing one of the 9-pF scope probes stops the oscillation, and ...
   Jul 28, 2026
5. Bidirectional solid state relay
   David A. Johnson
   Circuits Beginners Nexperia PMV30UN
   .. turn on hard from the 1.5 V from the red LED. The bi-directional configuration allows the circuit to switch both AC and DC power. Using quality super bright red LEDs, the circuit will switch on fully with only 5 mA of LED current. Materials ...
   Jul 27, 2026
6. Medium power 12V brush motor speed controller
   David A. Johnson
   Circuits Supply Intersil CA3240 CA3260
   .. many applications, you would like to hold the speed of a motor constant, even as variations in the power supply voltage or mechanical load try to change its speed. In other applications, the average current to the ...
   Jul 27, 2026
7. Build a practical 400 mA linear Li-ion charger with visible CC-CV behavior
   Richard O. Ocaya
   Circuits Supply Texas Instruments LM324 LM431
   .. The circuit offers a practical alternative for engineers who require simplicity, transparency, and predictability in low-power Li-ion charging applications. Materials on the topic Datasheet Texas Instruments LM324 Datasheet Analog Devices ...
   .. particularly for designers who value analytical transparency and first-principles reasoning. It operates from a 5 V supply, commonly found in 5 V/1 A smartphone chargers, delivers 400 mA of constant current (CC), then transitions to ...
   Jul 27, 2026
8. Current converter performs purely on paltry phantom power
   Stephen Woodward
   Circuits Measurement Supply Texas Instruments OPA2244
   .. a 4-20 mA signal to 0-20 mA and deliver it to a grounded load with no additional power supply needed. Recently, EDN kindly published a design of mine for a micropower 4-20 to 0-20 mA current loop ...
   Jul 23, 2026
9. Solid state airflow sensor with linear 4-20mA output
   Stephen Woodward
   Circuits Analogue Design Measurement Texas Instruments LM7905 TLV2197
   .. a self-heated transistor in a TO-92 package and force it to hold a constant temperature differential above ambient, the power input required to keep it stuck to setpoint will be determined by its thermal impedance Z T relative to the ...
   Jul 14, 2026
10. Position sensor gets linear 4 to 20mA current source output
    Stephen Woodward
    Circuits Measurement Texas Instruments SN74HC4066 TLV197-Q1 TLV9051
    .. tolerant, linear 4 to 20 mA, current mode output. Figure 3. Dangling the TLV431 shunt voltage reference Z1 from the 15 volt supply is a shortcut toward implementing a noise- and cable length- tolerant current mode output. Here’s how ...
    Jul 8, 2026

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