Circuits & Schematics: frequency meter - 4

31. Seven-octave linear-in-pitch VCO
    Stephen Woodward
    Circuits Oscillators Texas Instruments LMC555 SN74HCT74
    .. 2 ( Ref. 2 ) A pitch-linear VCO: Part 1 ( Ref. 3 ) and Part 2 ( Ref. 4 ) The linear in pitch function, which makes output frequency proportional to the antilog of voltage, is interesting because it provides a better perceptual ...
    May 21, 2025

32. Another PWM controls a switching voltage regulator
    Christopher Paul
    Circuits Supply Texas Instruments SN74LVC2G14 SN74LVC14A TLV333
    .. beyond a certain level of accuracy. This design proceeds with a PWM having 12 bits of resolution in mind, operating at a frequency of approximately 4900 Hz. It’s easy these days to find microprocessors (µPs) that can ...
    May 20, 2025

33. Revealing the infrasonic underworld cheaply. Part 1 - Seeking a solution
    Nick Cornford
    Circuits Analogue Design Audio Oscillators Microchip MCP6002 MCP6022 MCP6024
    .. I had to hand were very similar to those shown, being 10 mm in diameter by 6 mm high. Some experiments to check their frequency response practical details later showed a steady 6 dB/octave roll-off below about 15 Hz, implying that ...
    .. (usually bulky, static, and power-hungry) is too obvious to mention, so we won’t. A cheap 50 0 50 µA meter connected between the output and common via a suitable resistor worked, but its response was 50% down at ~2 Hz. ...
    May 20, 2025
34. A simple circuit to let you characterize JFETs more accurately
    Cor van Rij
    Circuits Analogue Design Measurement Texas Instruments TL071A
    .. was that the output voltage range for both measurements needed to be the same: 0 5 V. This was so that a moving coil meter readout could be used with a single range. See Figure 4 for the implementation. Figure 4. A circuit with the ...
    May 15, 2025
35. Fast response 1 Hz to 2.5 MHz V-F converter
    Jim Williams
    Circuits Measurement Analog Devices LT1004 LT319A LTC1052 LT1056
    .. at 2.4 V. Now the 50 pF capacitor receives charge, while A1 again integrates negative, and the entire cycle repeats. The frequency of this action is a linear function of the input voltage. Figure 2. Fast response V-F waveforms. D1 and ...
    May 14, 2025
36. Circuit delivers constant power to a load
    Kiril Karagiozov
    Circuits Supply Texas Instruments NE555
    .. let us generate pulses with constant energy E PULSE , independent of the resistance of the load R L . Then by changing the frequency f of the pulses we can conveniently and precisely control the load power (P = f E PULSE ), from 0 to a ...
    Apr 29, 2025
37. LM4041 voltage regulator impersonates precision current source
    Stephen Woodward
    Circuits Supply Analog Devices LM4041
    .. The C1 and C2 values shown are scaled for F PWM = 10 kHz to provide an 8-bit settling time of 6 ms. If a different PWM frequency is used, scale both capacitors by 10 kHz/FPWM. A hot topic is that Q4 can be called on to dissipate ...
    Apr 27, 2025
38. Reduce EMI by sweeping a power supply's frequency
    John Betten
    Circuits Supply Texas Instruments TL331 UCC3813N-0
    .. the noise, the greater the size, expense, and difficulty of the filter design. Power supplies that operate at a fixed frequency have their largest EMI emission at this fundamental, fixed frequency. Emissions also occur at multiples ...
    Apr 22, 2025
39. A negative current source with PWM input and LM337 output
    Stephen Woodward
    Circuits Analogue Design Supply ON Semiconductor LM337
    .. accuracy is insensitive to supply rail tolerance. The asterisked resistors are 1% or better and R S = 1.25 Ω. The PWM frequency, F PWM , is assumed to be 10 kHz or thereabouts, if it isn’t, scale C 1 and C 3 appropriately ...
    Apr 18, 2025
40. Water-leak detector uses 9V batteries
    Yongping Xia
    Circuits Measurement Analog Devices MAX934
    .. which lets you use a smaller value for C 2 . R 10 and R 11 increase IC 1D ’s hysteresis to improve the sound frequency's stability. All capacitors are ceramic, ensuring low leakage current. Reference Tregre, Jeff, ...
    Apr 18, 2025

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