SPOT
THE MISTAKES!
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These articles in SPOT THE MISTAKE are the most import discussions l have produced because they teach electronics “IN REVERSE.” They teach how NOT to design circuits and you can learn more in this direction than a 3 hour lecture.
That's the way I learned.  Fixing 35,000 TV's.  You get to know how to design things properly.
I have recently proof-read a number books for beginners in electronics and they are filled with mistakes.
All the mistakes located by other readers concentrated on incorrect lettering or wording.
None of them picked up the overall lack of understanding of the author about circuit diagram layout, selection of component values or descriptions of how the circuit or components work.
“the current goes in the long lead of a photo-transistor” is one absurd description (as all the leads are the same length).
And half a description of how a 555 lC works is no description at all.
A layout diagram is NOT a schematic. A layout diagram helps you wire up a component on a prototype board.
A schematic enables you to instantly see what the circuit does and it needs component values. They are entirely different.
There is not one schematic in any of his books. They are all layout "up-side-down" drawings and l can't figure out how any of the projects work.
If l can't, how do you expect a beginner to?
I have never cluttered a schematic with R1, R2 etc.  . ..  only component values.
And 470 for a resistor needs the designator:  470R. 
Resistors should be rectangles and not zig zag lines. You can put the value inside the rectangle to simplify the diagram.
The whole idea of a schematic is to produce a “picture” that can be analysed instantly.
I can look through a book of 1,200 circuits and determine what each circuit does, instantly.

THE INDUCTOR

This is Make Electronics. The book is filled with mistakes and many are are covered in SPOT THE MISTAKE.

The overall concept of the material in the books is my concentration.
No-one has analysed the actual electronic value of the books and said “what electronic knowledge is the book conveying?"
All the errata from reader has been wrong numbering and missing values.
No-one has identified the major fault.
And the major fault is this.
Layout diagrams are not schematics.
I have absolutely no idea how a layout diagram is behaving and l have been teaching electronics for 50 years.
A schematic is a photograph and just like you can have 20 photographs of identical people and still spot the difference, a schematic with different values will instantly show you the difference in operation.
The author has constructed all the projects on breadboard and some of these are so complex that l would not even want to build them.
Building on breadboard is not learning electronics. The projects should have been presented on a Printed Circuit Board with IC sockets for all the integrated circuits so that you can remove them if you want to build another project.
All that you will be left with will be some sockets and a few low-cost components.
A printed circuit board adds less than$3.00 to a project and saves the time-consuming work of cutting jumper wires and poking them down holes in the breadboard.
Nowhere in the book does the author explain how the circuit works and it would be pointless because the layout means nothing.
In the end, after reading through 4 of the books, l learnt nothing. It was just a jumble of wires and breadboard filled with wire.  l have contacted the publishers with my list of mistakes and improvements. I hope to get a reply within 6 months.

oooooooooo00000000ooooooooo

Here is typical example of the type of mistake and the lack of description of HOW THE CIRCUIT WORKS.
This circuit is one of the most important features to explain how an inductor works. 
If you don't explain it fully, it is just a waste of a page in the book.

Figure 5-33. In this demonstration of self-inductance, D1 and D2 are light-emitting diodes. When the switch is closed, D1 flashes briefly because the coil obstructs the initial flow of electricity. When the switch is opened, D2 flashes as the collapsing magnetic field induced by the coil releases another short burst of current.

The most important part to identify the cathode lead (k) of a LED
is beside the flat spot on the side of the LED (the shorter lead)

Compare the two lines of description above with the following:

The effect is this:
When the switch is pressed, one LED flashes. When the switch is released, the other LED flashes.

The circuit consists of 4 or 5 components and should be easy to describe. But it is very complex and needs a lot of description.
It is the simplest circuit that demonstrates the effect of a COIL - called an INDUCTOR. 

There are two components in this circuit that need to be described in detail. The inductor (the coil) and the LED.
When a voltage is applied to the terminals of an inductor, current enters the inductor and produces magnetic flux from each turn. This flux is called increasing or expanding flux and it cuts or “passes through” all the other turns and in doing so it produces a voltage in each turn that is opposite to the applied voltage from the supply.
This means the voltage entering the coil is opposed by a voltage as high as 99% from the voltage developed by the turns.
This means only a very small effective voltage is present and this produces a very small amount of flux.

The reverse voltage or opposing voltage produced by the expanding flux is initially 99% because there must be some forward voltage to produce the flux. It takes energy to produce the flux and as the flux increases, the energy required becomes greater. That’s why the expanding flux does not produce as much opposing voltage as the time increases.
That’s why the forward voltage gradually increase and so does the current.
Eventually the magnetic flux becomes a maximum and the supply cannot deliver a higher current.
At this point the voltage across the inductor is equal to the supply voltage and the flux is a maximum and is not expanding  - but has a constant value. The inductor is now classified as an Electromagnet.
The circuit remains in this state.
NOTE: The only reason this effect is occurring is due to the flux expanding or increasing. If the flux stops expanding, the induced voltage drops to zero.

However there is a LED across the coil and it has a characteristic voltage, depending on the colour, that is between 1.7v and 3.2v that appears across it when it is illuminated and this voltage never rises above this value.
So we have the situation where the voltage across the inductor is never more than say 1.7v and the inductor produces a back voltage of 1.69v in the beginning. This mean the LED sees a voltage sufficient for it to illuminate. And that’s what happens.
When the power is applied, the LED illuminates. Gradually the effectiveness of the expanding flux does not produce the same back voltage and the voltage across the inductor reduces. As soon as it falls to 1.6v, the LED will not stay illuminated and it goes out. The inductor now turns into an electromagnet with maximum flux that is not expanding. The circuit stays in this state.
When the switch is opened, the current stops flowing and the magnetic flux collapses. This collapse is very rapid and it produces a voltage across the terminals of the inductor that is reverse to the previous voltage. If the second LED was not present, this voltage would be very high and could be 10 times to 100 times larger.
But the second LED also has a characteristic voltage that prevents the voltage across it rising above say 1.7v and when the voltage reaches this level, the LED illuminates.
The collapsing magnetic flux delivers its voltage and current to the LED to produce a bright flash.
Amazingly, the coil would have produced a high voltage and very small current, without the LED. This is called ENERGY. The LED converts this ENERGY into a low voltage and high current. That’s why the flash is so bright.
This simple circuit needs an enormous amount of understanding and a few simple, vague, sentences will explain nothing.
The secret behind understanding this circuit is the fact that the inductor produces a voltage in the opposite direction when the switch is opened.

We have one more important feature to discuss. The inductor is in series with a resistor.
We have said the inductor produces an opposing voltage when voltage is first applied and the current is very small. When a very small current flows through a resistor only a very small “voltage drop” is created across it.
This means the full supply voltage is delivered to the inductor. As the opposing voltage produced by the inductor decreases, the current increases and the voltage drop across the resistor increases. This reduces the magnetism the inductor is producing however the effect still continues and in the end the inductor produces no “back voltage” and now the resistance of the winding in “Ohms” is what the circuit sees. It sees two resistors in series and they become VOLTAGE DIVIDERS. The resistor is 220 ohms and the inductor may be 10 ohms. This will determine how much current flows and it will determine how much magnetic flux is produced by the electromagnet. Obviously it will be much less than connecting the inductor to the supply.

You can see how important it is to have a good description of how anything works and not just a vague few words that don’t make any sense.
Obviously the author has no idea  how the inductor works, neither does any of the technical staff or the proof-reader or any reader of the book over the past 10 years.
The average technical understanding of electronics is minuscule.
If you don’t understand how components work, you will it be able design or fix problems.