# Basic electronics theory (response to Layman's issues)

Discussion in 'Architecture & Engineering' started by billvon, Nov 18, 2014.

1. ### LaymanTotally Internally ReflectedValued Senior Member

Messages:
1,001
Take a look at the diagram again.

If the first transistor is activated that would create a relative "short" from the collector to the emitter. That would place ground on the resistor connected to the base of the second transistor. Then the input of the hall senzor has no effect on the activation of the second transistor, and it is actually the voltage divider from ground going through the emitter and collector of the first transistor that creates a voltage divider via the small resistance of the first transistor going up through the inductors to the power supply. Now we have the base going to a resistor that leads to ground in a voltage divider and the emitter directly connected to ground for the second transistor. The resistor would then create a small difference in voltage that would give the base of the second transistor the small negative bias it needs to turn on. Then when the first transistor is on the second will also be on as well. This is a really in depth description of the operation of current flow in this circuit. It seems like you could all make great use of this type of understanding.

3. ### Dr_ToadIt's green!Valued Senior Member

Messages:
1,847
Good lord. It took me longer to parse that than it took to see how the motor control circuit works.

You oughta show up to the gunfight with bullets.

5. ### LaymanTotally Internally ReflectedValued Senior Member

Messages:
1,001
Good thing they didn't have the internet, when the electromagnetic force was discovered. A magnet works by the atoms being arranged so that the negative side and the positive side all point in opposite directions. The negative side is the electrons, and the positive side is the nucleus. If you had a strong enough voltage between two dielectric plates, they would attract each other and come together.

7. ### Aqueous Idflat Earth skepticValued Senior Member

Messages:
6,152
Here "bias" refers to a DC voltage at the base used to set the Q point (quiescent voltage). The Q point is set midway between min and max voltage swings, for low distortion amplification.

8. ### Aqueous Idflat Earth skepticValued Senior Member

Messages:
6,152
Still wrong. Look up "magnetic domain".

9. ### LaymanTotally Internally ReflectedValued Senior Member

Messages:
1,001
It is just that ammunition never seems to help.

Messages:
1,001
11. ### Aqueous Idflat Earth skepticValued Senior Member

Messages:
6,152
Your prior post equated the direction of the electric and magnetic fields, which is wrong. They are orthogonal.

But I encourage you to post from authoritative sources to keep you from falling into mistaken beliefs. Better than Wiki are the academic sites.

12. ### LaymanTotally Internally ReflectedValued Senior Member

Messages:
1,001
A capicitor would create a magnetic field like so...

13. ### TrippyALEA IACTA ESTStaff Member

Messages:
10,890
A capacitor (originally known as a condenser) is a passive two-terminal electrical component used to store energy electrostatically in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors (plates) separated by a dielectric (i.e. insulator).
http://en.wikipedia.org/wiki/Capacitor

Electrostatically, not magnetically.

Electrostatics is a branch of physics that deals with the phenomena and properties of stationary or slow-moving electric charges with no acceleration.
http://en.wikipedia.org/wiki/Electrostatics

No acceleration and stationary charges = electric field only, no magnetic field involved.

14. ### TrippyALEA IACTA ESTStaff Member

Messages:
10,890
No it doesn't.

It creates an electric field like so:

Any magnetic field would be orthognal to the electric field. In this case it would be coming out of the top of the image and going into the bottom of the image - just as it would be for the wires attached to the plates.

15. ### Aqueous Idflat Earth skepticValued Senior Member

Messages:
6,152
You are confusing electric charge and magnetic moment.

16. ### billvonValued Senior Member

Messages:
13,236
You just contradicted yourself. The sensor turns on the first transistor. When the first transistor on there is a close-to-short to ground between the collector of the first transistor and ground (since the emitter is connected to ground.) This brings the base of the second transistor close to ground, turning it off. Thus a high at the output of the Hall effect sensor turns the second transistor off.

Likewise, when the Hall sensor turns the first transistor off, the transistor effectively opens and the voltage on the collector rises to the voltage of the input rail. This turns the second transistor on, since the transistor is now biased on via the current flowing though its base resistor. Thus a low at the output of the Hall effect sensor turns the second transistor on.

No. If you think this you don't understand how bipolar transistors work. If the base is held below about .5 volts it will not turn on.
You seem like someone who has a little knowledge of electronics who is unaware of how little they really know. There is a name for this effect - the Dunning-Kruger effect. From Wikipedia: "The Dunning-Kruger effect is a cognitive bias in which unskilled individuals suffer from illusory superiority, mistakenly rating their ability much higher than is accurate. This bias is attributed to a metacognitive inability of the unskilled to recognize their ineptitude."

I think you post things like "it seems like you could all make great use of this type of understanding" to make yourself sound smart, like you are sagely advising people to learn what you know. Just so you know you are coming off like a fool, because the statements you make about electronics design are almost invariably wrong and represent the sort of misunderstandings of electronics common in first year EE students. This in and of itself is not all that bad; plenty of EE students with such misunderstandings go on to become quite competent EE's. It is troublesome, though, that you are reveling in your ignorance and making no attempt to learn; if you follow such a path, you will continue to misunderstand electronics design, and come off as foolish rather than learned.

17. ### LaymanTotally Internally ReflectedValued Senior Member

Messages:
1,001
http://en.wikipedia.org/wiki/Electrostatics

"Electrostatic generators
Main article: Electrostatic generator
The presence of surface charge imbalance means that the objects will exhibit attractive or repulsive forces. This surface charge imbalance, which yields static electricity, can be generated by touching two differing surfaces together and then separating them due to the phenomena ofcontact electrification and the triboelectric effect. Rubbing two nonconductive objects generates a great amount of static electricity. This is not just the result of friction; two nonconductive surfaces can become charged by just being placed one on top of the other. Since most surfaces have a rough texture, it takes longer to achieve charging through contact than through rubbing. Rubbing objects together increases amount of adhesive contact between the two surfaces. Usually insulators, e.g., substances that do not conduct electricity, are good at both generating, and holding, a surface charge. Some examples of these substances are rubber, plastic, glass, and pith. Conductive objects only rarely generate charge imbalance except, for example, when a metal surface is impacted by solid or liquid nonconductors. The charge that is transferred during contact electrification is stored on the surface of each object. Static electric generators, devices which produce very high voltage at very low current and used for classroom physics demonstrations, rely on this effect.

Note that the presence of electric current does not detract from the electrostatic forces nor from the sparking, from the corona discharge, or other phenomena. Both phenomena can exist simultaneously in the same system.

18. ### Aqueous Idflat Earth skepticValued Senior Member

Messages:
6,152
Right. And as you and billvon have repeatedly stated, the magnetic field only arises when the electrons are in motion (usually in producing currents in circuits).

Now let's see if he can understand the difference between charge and spin.

Trippy likes this.
19. ### TrippyALEA IACTA ESTStaff Member

Messages:
10,890

I didn't say there wouldn't be attractive or repulsive forces, only that those forces were electrostatic, not magnetic.

20. ### LaymanTotally Internally ReflectedValued Senior Member

Messages:
1,001
There is no contradiction. Voltage is a relative term. The voltage level at the base of the second transistor would just be a little more positive than the emitter, due to the resistor at it's base. Then the base would have a small positive voltage relative to the emitter, hence activating it.
If the first transitor was off, then the second transistor would have the full +12 volts at it's base. That would be too much voltage to activate the transistor! The base would be 12 volts and the emitter would be 0 volts.

Seriously? I would think it would take a little less than that depending on the particular transistor.
Blah, blah, blah, blah, blah... ya, whatever; stick and stones.

21. ### LaymanTotally Internally ReflectedValued Senior Member

Messages:
1,001
Then a 5th fundamental force of nature has been discovered and no one told me about it?

22. ### TrippyALEA IACTA ESTStaff Member

Messages:
10,890
No.

Generating a magnetic field requires moving charges, this is why a wire generates a magnetic field where a battery does not. Stationary, or static electric charges, such as those found in a capacitor generate a static electrical field without the presence of a magnetic field, magnetic fields are only generated when those sources of static electrical fields charge or discharge, because as the charge or discharge they experience moving electrical charges.

This is basic first year electrical engineering or physics we're dealing with here - some of it's highschool level stuff.

23. ### LaymanTotally Internally ReflectedValued Senior Member

Messages:
1,001
Oh ya, like when the teacher rubs a balloon on his head to demonstrate the magnetic field caused by electrons moving more into one object.

http://en.wikipedia.org/wiki/Electrostatics

"In special relativity, electric and magnetic fields are two interrelated aspects of a single object, called the electromagnetic tensor;"

http://en.wikipedia.org/wiki/Electromagnetic_tensor