Great discussion. My take on it is that some things are better tought with human interaction, at least in the beginning. And we all know teachers who changed our lives and we wonder what made them so much better than others.
I believe good teaching involves some sales and psyhology skill. You need to ask questions of the student, guage their level of interest, see how they learn and what clicks with them. Different methods of learning is why someone can watch 10 videos of something and not understand a word, yet on the 11th or by reading a book they get it.Electronics is a complex branch of physics. It is a layered onion and part of the questions I would ask are to determine how many layers to expose to someone before I tried to answer their question. Before going off for 3 pages in response to "how does a transistor" work I would have to have a conversation. I wouldn't want go into a dissertation on N-Channel and P-Channel doping when all they wanted to know was, "It's like a valve".So "How" something works can be interpreted different ways. Learning theory as a EE helped me even when it bored me because later, I was able to work out problems by knowing at a subatomic level "how" it worked. I didn't need to memorize because I could picture what was happening and work it out. But unless I was designing an integrated circuit, most of the time I just needed to know what a component does in a circuit and were to find the cheat sheet for how to make it work the way I expected.Other people might just want things at the circuit level that they could figure out how to put together for examples. But if someone gave me an hour and a blackboard, I would LOVE to explain everthing I know about how a MOSFET works ;)
Bayfield Transfer RailwayI know, for instance, that when I apply a current to the base of an NPN transistor, a larger current will flow from the collector to the emitter.
greg - Philadelphia & Reading / Reading
gregc Bayfield Transfer Railway I know, for instance, that when I apply a current to the base of an NPN transistor, a larger current will flow from the collector to the emitter. there are other aspects of a BJT that allow it to regulate voltage that make it well suited for a transistor throttle and described by Linn Westcott in his articles on using transistors.
Bayfield Transfer Railway I know, for instance, that when I apply a current to the base of an NPN transistor, a larger current will flow from the collector to the emitter.
there are other aspects of a BJT that allow it to regulate voltage that make it well suited for a transistor throttle and described by Linn Westcott in his articles on using transistors.
gregcthere are other aspects of a BJT that allow it to regulate voltage
Hi Greg and others,
I would like to make a request to everyone who wants to respond to this thread in the future. Actually, I should have done this at the very beginning:
Please explain your abbreviations. I haven't got a clue what a 'BJT' is. Sounds like a variation of a BLT (bacon, lettuce, tomato sandwich). Somehow I doubt that it would help if you ordered your BJT with extra mayo.
Seriously, this thread was started so that those of us who are electronically challenged could commiserate. Using electronic short forms without bothering to define them isn't very helpful.
I mean no offense. Clearly, many of you understand the terms which is great. Congratulations! However, many of us don't understand them, and your using them without explanation leaves us who are challenged still in a fog.
I hope that didn't come across as being too harsh. It wasn't intended that way at all.
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
+1
OvermodYou should discuss those in plain and simple language to add to the 'fundamental' idea that the transistor acts as an amplifier...
hon30critterPlease explain your abbreviations. I haven't got a clue what a 'BJT' is.
bipolar junction transistor (BJT) and Field Effect Transistor (FET/MOSFET)
hon30critter Overmod You should discuss those in plain and simple language to add to the 'fundamental' idea that the transistor acts as an amplifier... Dave
Overmod You should discuss those in plain and simple language to add to the 'fundamental' idea that the transistor acts as an amplifier...
i can try
A BJT controls current. in a common emitter circuit, the current thru the collector (C) and emitter (E) path is some multiple (e.g. 50) of the current thru the base (B) and E path.
using Ohm's law (I = V/R), the BE current is limited by the resistor in series with the base due to a voltage. that BE current allows a proportionally larger current thru the CE terminals and resulting in a proportionally larger voltage across a resistor in series with the C terminal. this is a basic voltage amplifier.
but another common use of this type of circuit is to allow a smaller current thru the BE path to control a larger current thru the CE path.
a digital output from something like an Arduino may not have enough current to drive a relay coil. a transistor can be used where the digital output is connected thru a resistor (~1k) to the base of a transistor and the relay coil connected between the C terminal and power supply (e,g, 12V)
another possible application is to use a (IR) photo transistor connected between power and in series with a resistor to control the base current so that it can control an LED or relay connected between power and the C terminal (see examples).
but the BJT can also be used in a common base circuit to regulate the output voltage. this is described by Linn Westcott in Getting closer to realistic performance (Feb 1962 MR).
the BE path is effectively a diode. the current thru a diode is exponentially proportional to the voltage across it.
in this configuration, the B terminal sets the desired output voltage at the E terminal. the voltage at E is one diode drop (~0.7V) less than the base voltage.
with the base voltage constant, when the voltage at the output drops, the votlage across the BE junction increases along with the current which usually causes the output voltage to increase. similarly, if the output voltage increases, the BE voltage and current drop, resulting in less output current and voltage. this behavior causes the output voltage at E to track the base voltage.
this circuit is a basic regulator and was described by Westcott to maintain constant voltage to a locomotive while its load changed going up and down grades or as the unregulated power supply voltage varied under load.
today, processors monitor BEMF and efficiently control motor power using PWM and H-bridge circuits
a diode is composed of a single semiconductor junction, NP. a BJT is composed of two junctions, either NPN or PNP, and can be used in various ways to various affects, only two described above.
4265
Thanks Greg,
I think I understood your explanation, or at least parts of it.
i'm curious about which parts are less clear
gregci'm curious about which parts are less clear
I don't think any of the parts were unclear. My problem is that my eyes glaze over when I start to read the diagrams. If I re-read the explanations several times, little things will start to sink in, and I will eventually form a basic understanding of the concepts. For example, your Arduino explanation made perfect sense. What doesn't seem to stick are the precice details of how the circuit is formed.
I guess I'm being lazy. I'm sure if I really wanted to learn things in detail I could do it, but it just doesn't interest me. I don't need the detailed information in order to do what I need to do, which is basically just to follow assembly instructions. I can build a simple circuit. Just don't ask me to design it.
Cheers!!
Dumb dumb speak:
Logic circuits are only designed to allow small amount current out. But our devices like relays and motors take a lot of current.
Most transistors when you apply a small amount of current to the base allow a much larger current through the collector to emmiter legs.
There is a minimum voltage at the base pin before the transistor will work. .7v is common. Once you above this "threshold voltage" the transistor is on and allows a much greater current up to saturation voltage (where increases in base voltage will damage transistor or make no difference in output)
If the emmiter/drain side of the transistor has a voltage higher than the source/ collector or base pin then you will damage the transistor. This is why we put protection diodes to bypass the transistor is there is a voltage backfeed caused by a relay turning off.
There are many types of transistors and logic circuits. This is just the most common and basic concept.
Hope this helps ..from one moron to another. (I say that tongue in cheek)
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
gregc but the BJT can also be used in a common base circuit to regulate the output voltage. this is described by Linn Westcott in Getting closer to realistic performance (Feb 1962 MR). the BE path is effectively a diode. the current thru a diode is exponentially proportional to the voltage across it. in this configuration, the B terminal sets the desired output voltage at the E terminal. the voltage at E is one diode drop (~0.7V) less than the base voltage. with the base voltage constant, when the voltage at the output drops, the votlage across the BE junction increases along with the current which usually causes the output voltage to increase. similarly, if the output voltage increases, the BE voltage and current drop, resulting in less output current and voltage. this behavior causes the output voltage at E to track the base voltage. this circuit is a basic regulator and was described by Westcott to maintain constant voltage to a locomotive while its load changed going up and down grades or as the unregulated power supply voltage varied under load. a diode is composed of a single semiconductor junction, NP. a BJT is composed of two junctions, either NPN or PNP, and can be used in various ways to various affects, only two described above. 4265
I've seen this design on really cheap usb power supplies from China. Voltage regulation is horrid. I mean it's effective provided it's low current regulated. But today's batteries will suck up a lot.
Ive seen designs where they just use the wire enamal on the primary and secondary windings with nothing else between. That's thin enamel wiring protecting your device and your life from 120v ac current.
DigitalGriffinI've seen this design on really cheap usb power supplies from China.
this is referred to as a linear regulator, commonly used in the 78xx series regulator chips (see 7805).
most DCC decoders use this type of regulator to drop track voltage (~14V) down to processor voltage (5V)
the drawback of this design is that whatever power is not consumed at the output is dissipated in the chip. if the input is 8V and 1A were being drawn, 5W (5V * 1A) is consumed by output and 3W ((8-5V)*1A) dissipated by the chip.
most electronics today use switching power supplies
4517
DigitalGriffinThere is a minimum voltage at the base pin before the transistor will work. .7v is common. Once you above this "threshold voltage" the transistor is on and allows a much greater current up to saturation voltage (where increases in base voltage will damage transistor or make no difference in output)
and this is why a series resistor is needed to limit the base current, just like with LEDs
4603
gregc and this is why a series resistor is needed to limit the base current, just like with LEDs 4603
Good lessons Greg. Maybe you could start a series for MRR :)
DigitalGriffinMaybe you could start a series for MRR
gregc i'm told that the editors of MR feel such topics are too technical for the readers of the magazine. they certainly weren't when Linn Westcott was editor
i'm told that the editors of MR feel such topics are too technical for the readers of the magazine. they certainly weren't when Linn Westcott was editor
Yes andno. I would agree that the majority of their customer base is likely older, and therefore likely less technically inclined towards electronics.
BUT I will say electronics have come a long long way since the early days. Things have been standardized and put into modules like IR detectors. The old days of building your own power supplies, and IR sensors from SCRATCH are long gone. Today it's as simple as a USB wall wart, an Arduino, and an IR module and knowing how to load up code.
While such adventerous activities are a small part of the audience, for some, the lessons are invaluable.
Simple lessons:
1. How to tell a block is occupied: IR, Light, or CT Current-3 ways to do it using Arduino
2. How to get points to automatically flip for an approaching train.
3. How to get lights to simulate morning/daytime time tables, or random lighting.4. How to get faschia push buttons/switches to control a layout
5. How to use JMRI-the basics
All basic stuff that can be taught in three pages or less.
This all looks very suspicious. It's a rewording of Dave's OP from a year ago, and only thinly disguised. Is this an AI experiment?
Returning to model railroading after 40 years and taking unconscionable liberties with the SP&S, Northern Pacific and Great Northern roads in the '40s and '50s.
This is about the strangest thing I've seen on the forum in quite a while.
Join the forum, pick out an old thread, copy the first post and post it again. Someone having too much time? Some electronic phishing?
York1 John
I really think it looks like artificial intelligence [sic]. The phrases "but man, was I wrong" "same deal", "not in the cards" and "wrap my head around it" seem sort of effortful, trying too hard to sound the way we carbon-based units talk. Dave's post sounded like Dave. This sounds like an experiment in rewording and phrase replacement.
-Matt
When did Quora acquire Kalmbach Media? Mods? MODS???
crossthedogI really think it looks like artificial intelligence [sic]. The phrases "but man, was I wrong" "same deal", "not in the cards" and "wrap my head around it" seem sort of effortful, trying too hard to sound the way we carbon-based units talk. Dave's post sounded like Dave. This sounds like an experiment in rewording and phrase replacement.
Hi Matt,
That's an interesting explanation for the apparent plagiarism of my lead post. The possibly good thing that that implies is that AI is still following my lead. The absolutely horrible thing is that AI will soon learn how to put things in apparently independant terms.
I read an artical today that said that the 'grandfather' of AI who is a professer at the University of Toronto now regrets his past work because he believes that AI will become a very dangerous thing in the near future. Numerous people including Elon Musk have called for a temporary stop to AI research so that we can develop ways to control it. Scary!!
"I'm sorry, Dave. I'm afraid I can't do that".
Amazing, sometimes, how prophetic some movies can be
This was 55 years ago!
Cheers, Ed
AI like block chain has been arround forever, it has just gotten better over time. People think this stuff is new, it is not but it keeps on improving. The scary think is all those movies obout AI can come true and in some cases already have. Read how close we have come to war already because of this stuff with things apearing on screens that were not there. Anything out there that can recive an outside signal can be messed with, period and you can put AI in control of most things now, period, but not to worry, a good solar flare will wipe out all electronics in seconds once it hits.
rrebellAI like block chain has been arround forever, it has just gotten better over time.
forever ?
my understanding is Marvin Minsky coined the phrase artificial intelligence in the 50s while working on a program to translate russian to english.
i don't believe there was much progress until about ten years ago when machine learning became successful and i believe is the basis for the intelligence behind what today is called AI which also includes language generation among other things.
listening to a description (warning) by AI experts on PBS recently described things like ChatGPT as essentially block boxes based on the information used to create them without anybody truely understanding their underlying logic and capabilities/liabilities
i don't believe the AI Minsky describes has yet to be achieved, could today's AIs create a better AI?
7166
Chat GPT and its near-clones aren't "artificial intelligence", they are massively trained neural networks that have been taught to return phrases in context from the 'hive mind' that is searchable information on the Internet.
It shouldn't surprise you that, sometimes, the 'context' in an early hit is going to be a quote from these forums. And that it's going to get passed through something that more or less disguises the exact language of what was lifted from the Internet...