Skip to main content

The Relay Races

Knowing that magnetism and electronics are related is a very important lesson. Just how important will become evident in the next few lessons, as we will be discussing the interaction of electricity and magnetism in greater detail. Let's review some of the things we have learned:

The Law of Poles
    We know that when two magnets are brought close enough to each other, they will have one of two reactions. If their poles are the same polarity, they repel, or push away from each other. If, on the other hand, their poles are opposite, they attract, or pull toward each other. This is called the LAW OF POLES and it applies (to an extent) to electronics as well as with magnetics.

    Note that the electrons from the negative side of a battery will attract toward the positive side, if the two are brought electrically close enough to be allowed to do so. This typically happens by connecting a wire, lamp, or some other electrical device between the two electrical poles.
If we think of electronics from this standpoint, the questions soon arises:

Does electricity move from positive to negative, or from negative to positive? This is a good time to discuss the fact that because we can not truly see the electrons in motion, but can only study their effects, there are 3 differing schools of thought on this subject, all of which have some merit.
    1).According to the CONVENTIONAL THEORY of electron flow, also known as the FRANKLIN THEORY, or the POSITIVE CURRENT FLOW theory, electricity flows FROM POSITIVE TO NEGATIVE.
    2).According to the EDISON THEORY , or the NEGATIVE CURRENT FLOW theory, electricity flows FROM NEGATIVE TO POSITIVE
    3). According to the ELECTROMAGNETIC CURRENT FLOW theory, electricity, like magnetic lines of force, are free floating in space, and PUSH OR PULL WITH EQUAL FORCE IN BOTH DIRECTIONS . This theory, depending on the amounts of negative and positive energy, and the electrical proximity of the components between them, gives merit to either of the two above theories.
Which of the 3 theories you choose to believe is totally up to you, but it would behoove you to remember the fact that there are 3 differing theories. Some writers write books based upon positive flow. Most modern authors choose to assume negative. But there are times when it is convenient to switch sides of the fence, in order to figure out exactly what is going on inside a circuit. The third theory is rare to find in books, however it does have its merits as well. The important point here is to make sure you know which theory your author is using, and try not to get too utterly confused.

    Another fact we know is that we can control the polarity of an electromagnet, by controlling the polarity of the voltage being fed into it. The North pole of the electromagnet is ALWAYS on the positive side of the battery.

Attracting Magnets Repelling Magnets With this thought in mind, we can control the physical movement of a permanent magnet, by controlling the voltage going through a given electromagnet. If we attach a battery to an electromagnet in such a way that it has the opposite polarity of a nearby permanent magnet, it will pull the permanent magnet closer to it. If we then swap the wires going to the battery, the electromagnet will change its polarity, and the permanent magnet will be pushed away from it.

If we physically attach the permanent magnet to a plunger, we can control the movement of the plunger in and out using electrical current. In this way, we use electric current to push a button, pull a lever, open or close a valve, or any number of other tasks.

Because magnets attract ferrite based metals, we can also use electricity to control the physical movement of iron. In the examples given to the right, we are using electric current to move a type of reed switch. These are handy for allowing us to use a small amount of current to, for example, turn on a motor which needs a very large amount of current. Break Contact Relay
    In the case of the break contact relay, the reed switch inside the relay is constantly CLOSED (meaning connected), allowing current to flow through it. The motor is on all the time. When we connect the battery to our circuit via the switch, it will cause the magnet to pull at the iron reed, opening the switch, and turning the motor off.
Make Contact Relay
    In the case of the make contact relay, the reed switch inside the relay is constantly OPEN (meaning disconnected), so no current is allowed to flow through it. The motor is normally turned off. When we connect the battery to our circuit via the switch, it will cause the magnet to push at the iron reed, closing the switch, and turning the motor on.
Relay and Motor Schematic

    Now would be a good time to show a schematic diagram and picture of a relay. The diagram to the left is an exact duplicate of the make contact relay circuit represented by the above picture. The break contact relay schematic symbol would be similar, except the contacts would be connected. Keep in mind, that not all schematic symbols are standard. You may see variations of schematic symbols over the years, but they will all be understandable and descriptive of the function of the component.

    Below is a picture of a relay

Popular posts from this blog

Build a Low Noise And Drift Composite Amp Circuit Diagram

How to Build a Low Noise And Drift Composite Amp Circuit Diagram. This circuit offers the best of both worlds. It can be combined with a low input offset voltage and drift without degrading the overall system`s dynamic performance. 
 Low Noise And Drift Composite Amp Circuit Diagram

Compared to a standalone FET input operational amplifier, the composite amplifier circuit exhibits a 20-fold improvement in voltage offset and drift. In this circuit arrangement, A1 is a highspeed FET input op amp with a closed-loop gain of 100 (the source impedance was arbitrarily chosen to be 100 kfl). A2 is a Super Beta bipolar input op amp. It has good dc characteristics, biFET-level input bias current, and low noise. A2 monitors the voltage at the input of A1 and injects current to Al`s null pins. This forces A1 to have the input properties of a bipolar amplifier while maintaining its bandwidth and low-input-bias-current noise.

High Power Output Amplifier TDA7294

The famous SGS-THOMSON ST Microelectronics has introduced a Hi-Fi DMOS high-power amplifier circuit TDA7294, its sound great taste bile, which due to its internal circuit from input to output are field-effect devices, rounded sound Mild, delicate Rounuan.  However, with its assembly amplifier, only TDA7294 single-output power is only 70 W, BTL access law is 100 W from top to bottom, do not feel that power cushion. The author several tests, used to promote TDA7294-level, direct-drive one to four pairs of high-power transistor parallel, the output of strong currents, the power output of 400 W (mono), and the circuit is simple and no need to debug that can reliably work Basically, the IC has maintained a sound and performance.  Ruzuo The figure below shows, R6 for the feedback resistor, the author of the value in debugging 22 k Ω more appropriate, R6 also decided this circuit gain, the gain value will increase.  Quiescent current depends on the power of R7, R8, when its value…

Full Power Mobile Phone Jammer Circuit Diagram

Full Power Mobile Phone Jammer Circuit Diagram.To day if we are talking about expert Cell phone Jammers we are conversing about this schematic underneath. First off all you should be very very cautious how to use this apparatus. Its completely illegal and so the reason. I post this Circuit is only for educational and testing causes. This type of apparatus is being utilised by security for VIPS, particularly at their limousines to avoid blasting device initiating while the vehicle passes from the goal cell phone-bomb. Off course there are those who use it to make a antic or to make the persons crazy in the rectangle block you are. 
The power of the jammer is currently sufficient to do your thing, but certainly you can place a 30W linear power amp at the RF output and impede a much wider locality. So, Be pleasant individual with that and recall that there are people who may need desperately to obtain or make a call and one of them could be you! And if you can't oppose of functioning …