this electronics forum is a good place to ask such questions: both how to do things as well as how they work
Hi Don,
Right now I don’t have a specific project in mind. I started this thread after watching a YouTube video about how transistors work. The video popped up on its own when I was surfing Youtube so I thought I’d see if I could learn anything from it. Unfortunately, when I had finished the very professionally produced video, I realized that my eyes were glazed over and my brain was in a fog. I had learned a bit more than I already knew, which wasn’t much to start with, but don’t ask me to design a circuit unless you want me to let the smoke out![swg][(-D][(-D]
The thread was actually started with my tongue stuck firmly in my cheek. It was actually an attempt at humour, albeit a poor one. I figured that other poor souls who suffer from the same affliction might find some comfort knowing that they are not alone.
I am really gratefull to those who tried to explain things in detail. In fact, one gentleman took the time to send me an email explaining the process. Alas, his attempt didn’t help.
As I said, I have enough knowledge that I can follow an electrical diagram well enough to build simple circuits, and that’s really all I need.
Thanks again everyone.
Cheers!!
Dave
[quote user=“hon30critter”]
DigitalGriffin
Sorry Dave, Sometimes it’s just easier to have someone teach you first hand. What are you trying to accomplish? Maybe one of us can rig up a simple solution for you.
Hi Don,
Right now I don’t have a specific project in mind. I started this thread after watching a YouTube video about how transistors work. The video popped up on its own when I was surfing Youtube so I thought I’d see if I could learn anything from it. Unfortunately, when I had finished the very professionally produced video, I realized that my eyes were glazed over and my brain was in a fog. I had learned a bit more than I already knew, which wasn’t much to start with, but don’t ask me to design a circuit unless you want me to let the smoke out!
The thread was actually started with my tongue stuck firmly in my cheek. It was actually an attempt at humour, albeit a poor one. I figured that other poor souls who suffer from the same affliction might find some comfort knowing that they are not alone.
I am really gratefull to those who tried to explain things in detail. In fact, one gentleman took the time to send me an email explaining the process. Alas, his attempt didn’t help.
As I said, I have enough knowledge that I can follow an electrical diagram well enough to build simple circuits, and that’s really all I need.
Thanks again everyone.
Cheers!!
Dave
[(-D][(-D][(-D][(-D][(-D]
Dave
Electronics are also highly dependent on smoke. When it escapes is when you will start having problems. Fortunately replacement smoke is available for purchase.
[bow] [(-D] [(-D] [(-D]
That is hilarious!!!
Dave
Part of the problem is the blending of different KINDS of information. 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.
I could not care less about WHY it happens that way.
Too many sources, even the simple Howard Zinn booklets Radio Shack used to publish, include much more “why” than I need or care about. Tell me when is the right time to use a transistor, a FET, or a UJT; I really do NOT care what happens on the subatomic level.
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 
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.
You should discuss those in plain and simple language to add to the ‘fundamental’ idea that the transistor acts as an amplifier…
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.[swg][(-D][(-D]
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
+1 [tup]
[tup]
Dave
bipolar junction transistor (BJT) and Field Effect Transistor (FET/MOSFET)
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 termin
Thanks Greg,
I think I understood your explanation, or at least parts of it.
Dave
i’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!!
Dave
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) [;)]