Circuits & Schematics: -Wire Barometer 5/10 Volt Design vrs - 4

31. BJT is accurate sensor for absolute temperature in Kelvin and Rankine
    Stephen Woodward
    Circuits Analogue Design Measurement NXP 74HC4053
    .. ΔV BE temperature measurement is aptly described and applied here ( Ref. 1 ) by famed and forever remembered analog design guru Jim Williams (see page 7): At room temperature, the V BE junction diode shifts 59.16 mV per decade of ...
    Apr 30, 2026

32. Linearly variable two-wire loop current generator
    Jayapal Ramalingam
    Circuits Measurement Interfaces Texas Instruments LM124
    .. such as the design described here implement useful tools for a diversity of calibration and testing applications A two-wire loop current generator is a useful tool for the testing, calibration and commissioning of current-to-pressure ...
    Apr 24, 2026
33. Tiny continuity tester
    David Johnson-Davies
    Circuits Measurement Microcontrollers Usage Microchip ATtiny202
    .. I've used a slightly larger battery, the CR1025, and a battery holder which gives a more reliable connection than the wire clip used on the original. The circuit drives the piezo speaker in bridged mode from two outputs, to make it ...
    .. button cell, and automatically switches itself off when not in use, avoiding the need for an on/off switch. Introduction I design many of my projects for my own use, and the original Continuity Tester is one of the ones I use the most, to ...
    Apr 16, 2026
34. Double-duty current loop transmitter
    Stephen Woodward
    Circuits Analogue Design Interfaces Fairchild LM317
    .. (or otherwise)-caused cable cuts, and differentiating them from normal open circuits, is critical. Evolving the circuit design for expanded functionality makes it even more valuable. It’s just part of the job. Every design ...
    Apr 15, 2026
35. Newer, shinier DMM RTDs. Part 2
    Nick Cornford
    Circuits Measurement Analog Devices OP177
    .. the first part ( Ref. 1 ) of this Design Idea, we saw how a cheap op-amp can give remarkably precise readings from an RTD. We also found that it was a ...
    Apr 8, 2026
36. 5-V ovens (some assembly required). Part 2
    Nick Cornford
    Circuits Supply Microchip MCP6002
    .. bad news. With a PNP Darlington, the collector can be at ground, give or take a handful of millivolts. (The fine copper wire used to connect the module to the outside world has a resistance of about 1 Ω per meter.) Q1 drops ~1.3 V and so ...
    .. the first part ( Reference 1 ) of this Design Idea (DI), we looked at simple ways of keeping critical components at a constant temperature using a linear ...
    Apr 7, 2026
37. Laser scanning microscope from Blu-ray player
    Doctor Volt
    Circuits Laser Microchip MCP6004
    DIY Laser Scanning Microscope made from a defective Blu-Ray Player. A Blu-ray player must be able to detect the microscopically tiny pits on DVDs in order to play back a film. Therefore, the question arises: Can a Blu-ray player also see other ...
    Apr 1, 2026
38. 1 MHz 555 VFC
    Stephen Woodward
    Circuits Measurement Texas Instruments LMC555 TLV9051
    .. converters and the 555 analog timer chip, and therefore a double obsession with VFCs based on the 555. In fact, my first Design Ideas (DI) submission (in 1974) was for a 555 VFC. It was not only published but also selected as the best DI ...
    Mar 27, 2026
39. 5-V ovens (some assembly required). Part 1
    Nick Cornford
    Circuits Supply STMicroelectronics TIP42A
    .. as both a sensor and a source of heat, but it is simpler. Figure 1 shows the schematic of a simple version needing only a 2-wire connection, along with two photos indicating its construction. It was slimmed down from a more complex but less ...
    .. ovens in this two-part Design Idea (DI) can’t even warm that leftover half-slice of pizza, let alone cook dinner, but they can keep ...
    Mar 26, 2026
40. 5 decade antilogarithmic PWM current source
    Stephen Woodward
    Circuits Supply Texas Instruments LMC555 LTC2066
    .. pages of Design Ideas (DIs) have recently been awash in a veritable cascade of designs for variable frequency oscillators ...
    Mar 26, 2026

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