Recent Posts

Pages: Prev 1 2 3 [4] 5 6 7 8 9 10 Next
31
General Technical Chat / Re: Do you think an LED is a resistor?
« Last post by Sredni on Yesterday at 11:38:36 pm »
Oh new words and definitions to play with. How about we take the IEEE dictionary as the authoritative reference:

static resistance (semiconductor rectifier device) (forward or reverse) The quotient of the voltage by the current at a stated point on the static characteristic curve.

Yes, this is the only one I have used. Did you not realize it?

Quote
small-signal resistance The resistive part of the quotient of incremental voltage by incremental current under stated operating conditions.

small-signal A signal which when doubled in magnitude does not produce a change in the parameter being measured that is greater than the required accuracy of the measurement.

As I said in my opening statement, you're just playing with small signal analysis a well known and entirely un-novel method. There is nothing interesting here as most anything can be described as a small signal resistor (with bounds on some other dimension). So you're still wrong and trying to twist definitions to your liking while ignoring the consensus and the established science.

No, I have not used small signal analysis. Where did you study small signal analysis? You are mistaken. Please seek tutoring from someone you trust to straighten this out.
33
RF, Microwave, Ham Radio / Re: WSJT-X on Pi
« Last post by ZigmundRat on Yesterday at 11:33:56 pm »
You’re in dependency hell due to severely mismatched package dependencies. If you’re trying to do this the simple way, Bullseye (the version you have installed) seems to have a WSJT-X 2.30 package available. If you want to run 2.6.1, then it looks like installing Debian ‘bookworm’ is the way to go as WSJT-X 2.6.1 is available there.

The Bullseye package is wsjtx_2.3.0+repack-2_armhf.deb
The Bookworm package is wsjtx_2.6.1+repack-1_armhf.deb

Both should be available in the standard archive and installable via apt.

Hope that helps.

34
LM317 is not an LDO and therefore is stable with low ESR capacitors such as MLCC. UPJ series have low ESR and high ripple current rating. Therefore they can survive way more load/stress than general purpose capacitors.
35
An assortment of enameled wire sizes (22-32 AWG) from Remington Industries.
36
General Technical Chat / Re: Do you think an LED is a resistor?
« Last post by Sredni on Yesterday at 11:31:38 pm »
To the OP.
Are you sure you are talking about a 'normal' diode, and not a 'special' type of (apparently chaotic) diode?

I am talking about ordinary signal diode, power diodes, zener diodes, tunnel diodes.
Have any of you even opened the Science Direct link I gave before?

From here (a page that is apparently invisible to many browsers)
https://www.sciencedirect.com/topics/engineering/nonlinear-resistor

Nonlinear Resistor
Nonlinear resistors have a common characteristic that their constitutive relationships are described by nonlinear algebraic equations.
From: The Electrical Engineering Handbook, 2005
 

From: A.C. Fischer-Cripps, in Newnes Interfacing Companion, 2002
3.3.7 Log amplifier
A non-linear resistor is connected into the feedback circuit. In practice, this can be a diode, but a transistor connected as a diode is used since the forward biased transfer function is more accurately exponential. The exponential nature of the forward biased diode leads to a logarithmic decrease in gain of the circuit as the input signal is increased.



From: A Gavrilović OBE, in Electrical Engineer's Reference Book (Sixteenth Edition), 2003
32.6.3 Surge arresters
The zinc-oxide non-linear resistor material used in modern surge arresters exhibits a very high impedance at normal applied voltage whilst at a voltage only some 50% higher a very low impedance is provided. The extremely non-linear relationship between voltage and current shown in Figure 32.20, has rendered obsolete the spark gaps which were a feature of previous arresters based on silicon carbide.
 

From: I.D. Mayergoyz, W. Lawson, in Basic Electric Circuit Theory, 1997
EXAMPLE 5.5 A Voltage Regulator Circuit
Consider the circuit shown in Figure 5.31, where a load resistor RL is connected in parallel with a nonlinear resistor characterized by the v1(i) curve shown in Figure 5.32. This curve exhibits “voltage saturation.” In other words, it has an almost horizontal (flat) portion which starts from small current values. We would like to find all currents and voltages in this circuit.



[note1: you know what is that curious component represented by a resistor symbol with two lines? It's a zener diode. A special kind of nonlinear resistor]

[note2: the above book as a section titled "Non-linear resistive circuits" where nonlinear resistors are introduced and diode and zener diode are used as examples of nonlinear resistors]

From YIN Jijun, ... LI Peng, in Unified Power Flow Controller Technology and Application, 2017
6.1.1.2.4 Metal oxide surge arresters
Gapless metal oxide surge arresters are used in a UPFC. In the simulation model, they can be replaced by nonlinear resistors. The nonlinear volt-ampere characteristics of valves are shown in Fig. 6.5.



From: Nasser Tleis BSc (Hons), MSc, PhD, CEng, FIET, M-CIGRE, in Power Systems Modelling and Fault Analysis (Second Edition), 2019
10.4.8 Passive damped resonant limiter
Fig. 10.10 illustrates one phase of a three-phase damped resonant limiter circuit that uses only passive components.



The limiter consists of an isolation transformer whose primary winding is connected in series with the ac system and a capacitor is connected across its secondary winding. A nonlinear resistor, for example, a varistor, or a fast-closing triggered switch, is connected in parallel with the capacitor, and a damped tuned filter is connected in parallel with the capacitor/varistor. Under normal unfaulted system condition, the secondary circuit appears as a capacitor at 50 Hz that, when transferred to the primary of the transformer, is equal to and hence cancels out the transformer’s leakage reactance. Therefore, at 50 Hz, the limiter appears as a short circuit except for the resistance of the transformer.
 

So, I hope there will be no more discussion about the usage of the term "nonlinear resistor". It is not a novel invention by Chua alone. It is a well known and estabilished term that encompasses, among others, diodes, transistors connected as diodes, zener diodes, varistors, incandescent lamps, neon lamps, etc. etc. etc.

I think we are left with the doubt if nonlinear resistors are... resistors. No kidding.
37
Looks like one heck of a considence right, but I can't explain how I get a real phase margine from the negative. For instance, do I substract 180 degrees from it? why?
No coincidence, look at the phase difference at say 1kHz, one is +90 degrees the other is -90 degrees, they always are 180 apart, and 180 degrees just means that one signal is inverted with respect to the other, just invert one of the voltage sources and they will agree.
38
Quote
I can install into the immersion heater cap?

Quote
Make a water/pressure proof probe that you can stick into it. Place the sensor inside that.
If theres an immersion heater theres a 99% chance theres already a water tight tube going into the cylinder for the existing  stat
39
EEVblog Specific / Re: EEVblog 1611 - Top 5 Jellybean 7400 & 4000 Logic
« Last post by cosmicray on Yesterday at 11:29:18 pm »
I see so many posts and reports of hobbyists like me burning their microcontrollers or SBCs or at least a few I/O pins on them, by not thinking about this stuff at all.  I wish someone with a wide enough viewership would point this out, because the solutions are so easy and easily available.  Starting from the current-limiting resistor (which relies on the ESD or other diodes to voltage rails), to transistor open collector outputs with pull-up resistors, to level translating transceivers, to digital isolators.

74ls07, buffer, open-collector, very useful for translating voltages.
40
RF, Microwave, Ham Radio / Re: WSJT-X on Pi
« Last post by mag_therm on Yesterday at 11:22:39 pm »
Read the answers here.
https://stackoverflow.com/questions/76696292/libc6-dev-depends-libc6-2-31-13deb11u6-but-2-36-9-is-to-be-installed
Try to do, as root, the package update as described at the end of the answers. Watch the update messages as they flow past.
(I am Fedora here, the commands are different but the o/s is very similar)

You can copy the error lines one by one and paste into your browser as I did above.
Pages: Prev 1 2 3 [4] 5 6 7 8 9 10 Next