Circuits & Schematics: 10 - 4

31. Design an RTD interface with a spreadsheet
    Robert S. Villanucci
    Circuits Analogue Design Measurement Analog Devices AD633 OP177
    .. precision specification. The combination of C 1 and R 5 implements a lowpass filter with a pole at approximately 10 Hz to remove power-supply noise. The following term describes the performance of IC 2 and its accompanying circuitry: ...
    Feb 25, 2025

32. A precision digital rheostat
    Stephen Woodward
    Circuits Analogue Design Supply Microchip MCP4131
    .. G A2 is A2’s gain. Further, Voltage across R1 = Current through R1 = Then, since V A is lightly loaded by A1’s ~10 picoamp (pA) input bias, so R1 can range from hundreds of ohms up to multiple megohms as the application may dictate. ...
    Feb 25, 2025

33. Tracking preregulator boosts efficiency of PWM power DAC
    Stephen Woodward
    Circuits Supply Fairchild LM317 2N3906
    .. U2 I/O headroom differential to improve efficiency. As described in the earlier DI (Ref. 1), switches U1b and U1c accept a 10-kHz PWM signal to generate a 0 V to 11.25 V “ADJ” control signal for the U2 regulator via feedback ...
    Feb 17, 2025
34. 1-A, 20-V, PWM-controlled current source
    Stephen Woodward
    Circuits Supply ON Semiconductor LM337
    .. 1-A PWM current source. (* = 1% metal film). I OUT = 1.07(D 0.07), I OUT 0. ACMOS inverters U1b through U1f accept a 10 kHz PWM signal to generate a 50 mV to +1.32 V “ADJ” control signal for the U2 current regulator ...
    Feb 7, 2025
35. Flip ON flop OFF
    Stephen Woodward
    Circuits Digital Texas Instruments CD4013B
    .. for the RC network and other curious connections surrounding the F1a flip/flop. When S1 is pushed and the circuit closed, a 10 ms charging cycle of C1 begins and continues until the 0/1 switching threshold of pin 4 is reached. When that ...
    Feb 6, 2025
36. Metal detector uses single IC
    Rachel Hageman Steve Hageman
    Circuits Measurement National Semiconductor LM389
    .. amplifier, whose gain is approximately 26 dB, easily drives a set of 8 ohm headphones. If you need more gain, you can add a 10 µF capacitor between pins 4 and 12 of the LM389. The prototype detector uses some polyvinyl-chloride sprinkler ...
    Feb 5, 2025
37. Microvolts to kilovolts in milliseconds with one I/O pin
    Stephen Woodward
    Circuits Measurement Microcontrollers Usage Texas Instruments LMC555
    .. 1’s silly-simple voltage-to-time ADC is an exercise in dynamic range. Assuming that it is used with a 10-MHz counter/timer, its resolution is roughly 10 µV per count for inputs around 0 V and 100 mV per count at 1 ...
    Jan 24, 2025
38. Practice safe dc/dc converter
    Eugene Kaplounovski
    Circuits Supply Texas Instruments LM2675
    .. a function of the length of the start-up pulse from the µC. This pulse should be long enough usually, approximately 10 msec to allow the normal load (with its own input capacitors and power converters) to start. The LM2675 with a catch ...
    Jan 22, 2025
39. Motor-control scheme yields four positions with two outputs
    Jean-Bernard Guiot
    Circuits Power ON Semiconductor 1N4937 BDX33C BDX34C
    .. If you activate neither Control 1 nor Control 2, Q 3 and Q 5 conduct, receiving base current through R 7 and D 1 and R 10 and D 2 , respectively. This action short-circuits (brakes) the motor. In this case, Q 4 and Q 6 are turned off. ...
    Jan 21, 2025
40. Power source is insensitive to load changes
    Ken Yang
    Circuits Supply Maxim MAX427 MAX4372H
    .. reference power. IC 6 and Q 1 form a voltage follower that drives the load. The following formula sets output power: V PC = 10 × P × R SENSE , where P is the desired output power in watts, R SENSE is the sensing resistor in ohms, ...
    Jan 20, 2025

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