Thursday, November 28, 2019

A mind experiment into the world of Electro - Magnetics. Part 2

A wire with no current flow will have its charges in random directions.
They could be in the four compass points and an infinite number of other directions.
The electron spin producing the fields.
Charges in motion create field in all directions. Now we send a charge down the wire and it creates a unifying effect.
We can determine the direction using the right hand rule. A wave can travel at near the speed of light BUT the electrons are basically stationary. The electrons orient with respect to the wave and the magnetic field is strengthened (it is already there just in random orientation.). More later.....

A mind experiment into the world of Electro - Magnetics. Part 1

Einstein would use real world examples to study the invisible world. I am not the genius he was but I will attempt a simple analogy. First the item I selected to demonstrate the principle is a level gauge. The sight gauge is made of a series of magnetic rollers.
Here we have a datasheet for one.
The flappers are white on one side and red on the other. As the level increases a magnet on a float causes the roller to flip over.
In this system we see two possible positions.
In the invisible world we can have an infinite number of positions. If the red is the north pole we can determine the position using the right hand rule.
Point your finger in the direction of the motion (spin) and the thumb points to the north pole. So if we know an electron has spin and we can determine its magnetic polarity using the right hand rule we can examine a crystal which is in caous and see no magnetic property. Applying a field to establish an orientation of the spins will produce a magnetic polarization.
First installment more to come..............

Sunday, November 17, 2019

Another look at the Transistor Universal (Amp) P or N

We start with a general purpose transistor and 4 resistors. The resistors I'm using are 100k, 10k, 4k7 and 511. I use these because they are what I have on hand you could use what you have within a reasonable amount. As we look at the circuits you will see how critical the values are.

First we establish the DC bias. R3 and R4 set the base bias. R2 sets the emitter bias. R1 is the collector load resistor. Connecting the Vcc completes the DC circuit.

Adding the capacitors provides the AC circuit. I marked the possible circuit connections. The The base cannot be the output and the collector cannot be the input. We connect the signal to the input and the load to the output. The third capacitor goes to ground (-Vcc).
Completing the circuit we have a battery and signal source. Time for some sim's.
Input base, output collector and ground emitter.
Input base, output emitter and ground collector.
Ground base, input emitter and output collector.

You may see the circuits drawn differently. Compare these three. In all three the base is grounded and the input is on the emitter. I downloaded these next three to show other variation.

So all we need is 4 values of resistors and a general purpose transistor to establish a basic amp stage with DC bias. Three capacitors to set the AC circuit response. The 2N3904 is a good general purpose transistor for hobby work. It will work in circuits up to 100 Mhz. You can look at the post on TUN and TUP circuit to see the tables of transistor you can use.


Saturday, November 16, 2019

Built an amp using the TUN design to see how it performed.

A piece of formica counter top and some copper tape can be used as the circuit board.

The back of the board will take glue better but the circuit shows better with the white background.

It is just a matter of leaving a little space between the strips.

Use an exacto knife to cut pads for the components to tie to. The two bigger strips are the power connections.

The white back ground helps you see the desired results.

It's just a matter of matching the pads and power connections as displayed in the diagram.

Here I used a piece of wood. I coated the wood with some glue befofe mounting the copper tape.

This is the amp with all the parts mounted. I used surface mount parts except for the transistors. You can use wired components if you like.

I connected power and set the input to produce 1 volt on the output. The input was about 40 mv.

The sim shows the schematic and the expected results. The circuit produced a little higher output than the sim predicted.

If I can do it anyone can.