torsdag den 29. juni 2023 kl. 23.24.06 UTC+2 skrev John Larkin:
I've seen one inverter in a 74hc14 used as oscillator, then low pass filtered and used to bias the rest of the inverters in the middle of the hysteresis "window" to condition VR sensors, that have output that vary from <1V to +100V with speed
You’d have to be careful not to turn on the protection diodes. Any asymmetry there would move the bias point.
Cheers
Phil Hobbs
Schmitts by design don't have giant shoot-thru currents. Some gates will fry if biased mid-range.
Magnetic coil and eddy-current type speed sensors tend to have voltage linear on speed, so a modified integrator is the ideal thing to put ahead of a comparator. I have a circuit around here somewhere...
A stepper motor makes a nice tach, but can shock you if you twist it fast.
The tuning fork crystals in those clocks aren't good for better than 100ppm over a normal (0 to 70 C) temperature range; temperature coefficient has too much curvature. AT-cut crystals can hold 10ppm over that range.
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** Shame a wall clock experiences no such extreme temp range. ** Per degree C - same as a watch crystal........ Phil
People seem to toss around crystal specs very loosely. There are at least three specs I can think of off the top of my head. One is the initial spec, at 25°C. Another is for aging over time. Then crystals are specified over temperature. AT cut crystals are cut with a double inflection curve, which wavers over the temperature range, while XY cut crystals used mostly for low frequencies have a parabolic shape, with the peak at 25°C.
When people talk about 100 ppm, they are usually referring to the initial accuracy. The aging spec is some ppm/year. The AT cut temperature spec is bracketed over a range of temperature, while the XY cut crystal is described by the parabolic equation, so ppm/°C.
I don't see any shame in that. Cost, to keep the temperature even, yes. Shame, no.
No, that's the whole range 0 to 70C.
See here
By now, we're talking about three discrete ICs, for what should be a simple task.
Sylvia.
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** It completely destroys your false assertions.** +/- 50ppm drift is typical over that range.
Go away fool.
...... Phil
Huh? What 'drift' do you mean? I'm looking at the range of the as-manufactured temperature response curves, none of which is flat, for maximum-over-temperature range of an individual crystal. 'Typical' isn't what I'm looking at, but best-case given that only those temperature curves are possible for AT shear-mode.
The 'typical' that you refer to is just one of the possible manufacturing tolerances, NOT the theoretical best available.
AT cut crystals have a family of curves for the temperature vs. frequency plot, depending on the details of how they are cut. In general, they are cut for a double inflection, crossing the 0 error point three times. This reduces the range of frequency variance over a limited temperature range.
32,768 Hz crystals don't have a ± variance over temperature. They are specified at a temperature they are cut for, then vary only in one direction as temperature changes in either direction. The variance is by the square of the temperature difference... a parabola... fool.Why do you have to be such a jerk about this stuff. Anyone can make a mistake, especially you. It doesn't need to be a huge emotional thing. You seem to get your ego all wrapped up in it, calling people names, then it often turns out you are wrong. WTF is wrong with you? What is your damage???
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** FFS Go away !!!------------------------------
** Yawnnnnnn................... ** Really ?** But only desperate assholes like "whitless" persist in making the same ones over and over. The guy is a troll and so are you.
FYI All trolls are fair game.
.......... Phil
As usual, when you are wrong about something, you will not even consider checking any references. I'll make it easy for you. Here's a 32.768 kHz crystal data sheet. Notice the temperature spec is negative and in units of ppm/°C^2 That makes the curve a parabola, with the peak between 20 and 30 °C (the turnover temperature).
From where? Aren't you posting from somewhere near the Antipodes?
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** From me - you f****ng retard.
That's pretty funny. You can't get much further away. LOL
I feel for people like Phil. He doesn't even know he has an illness.
Cheers
Phil Hobbs
Physical separation from Phil doesn't seem to help much. He was much the same when I was posting from Nijmegen as he is when posting from an adjacent suburb of Sydney.
Sydney is claimed to be the fourth most livable city in the world - Melbourne is third on that list. Vienna and Copenhagen are first and second
Back in the mid 1970s I was able to make 4013 oscillate but that was with the first generation "A" family. Buffered 4013B parts proved impossible to make oscillate.
Sorry to be late to see this thread.
piglet
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