This blog will keep to a simple theme of my tinkering with electronic and computer related toys, gadgets, projects and the like. I do hope from time to time there is something for someone to find when they are exploring these things for themselves. From an early age, I was always attracted to electronic gadgets an I continue to enjoy myself with my hobby. Unfortunately with a busy life, time becomes short an I can not indulge myself like in the past.
This experiment uses the same oscillator circuit as used in the previous experiments. Here, a switch is used to form a telegraph. Telegraph's where widely used in the last half the the 19th century before telephone systems. Telegraph's have only two states on and off. A code called Morse Code was developed by Samuel F. B. Morse of dots and dashes (long or short transmission burst) to send message in the form of electrical current along wires for communication.
This experiment is an oscillator circuit with a trip wire. The alarm is turned on by disconnecting a wire and turned off by connecting the wire (trip wire). The trip wire creates a "short circuit" across the transistor base, so no current flows into the base of the transistor and it stays off. When the "trip wire" is disconnected, the short is removed, and the circuit works sounding an alarm.
In this experiment, a speaker, a transformer and an oscillator circuit (made up of a transistor and varying resistors and capacitors) is used to create sound. A speaker converts electrical energy into sound (mechanical vibrations). In order for the speaker to work, energy from an AC electrical signal is needed. This is achieved with the transformer (converts high-voltage/low-current to low-voltage/high-current) and an oscillator circuit made up of one transistor and varying capacitors and resistors.
In this experiment, the LED blinks at a constant rate. This is because the transistor is being turned on and off. This circuit is called an oscillator and it uses a feedback signal. Feedback is when the input signal is based on the output signal. In this case, the collector signal (part of transistor) is feedback to the base (part of transistor) through a coil (part of transformer) and the 100 microfarad capacitor. The rate at which the transistor is turned on and off is called the frequency and is controlled by the resistor, capacitor, and coil in the circuit.
In this experiment, the left LED blinks when the switch is pressed and than the right LED blinks. When one presses the switch, a sudden surge of current (AC) goes through the inductor that magnetically creates a current on the other side of the transformer, lighting the left LED. The current from the battery settles after the initial surge (becomes DC) and the magnetic induction stops because the current is no longer changing, hence no current flows through the LED even though there is current on the battery side of the transformer. When one releases the switch, the sudden drop in current through the transformer magnetically creates a new current on the other side of the transformer, but this time in the opposite direction so the right LED lights instead of the left LED. Again, this current is brief and the LED only blinks. The transformer has many more turns (more inductance) on the LED side than on the battery side; this boosts the voltage to the LED's (though it also lowers the current). If the transformer was in reverse, there would not be enough voltage to turn the LED's on. The transformer is functioning as a magnetic bridge in electronics, since we use magnetism to cross a barrier that electricity cannot cross by itself. Transformers are mainly used for isolating and buffering different circuits from each other.
This experiment uses the same circuit as in experiment #8. But instead of a capacitor, an inductor is used. An inductor passes stable current (DC) and blocks unstable current (AC). In the video, when I turn the switch on, the LED lights then goes out (blinks). Next, I disconnect and reconnect the wire to show that less inductance produces a dimmer (blinking) LED light. Lastly, I introduce a diode into the circuit to stabilize the current (AC to DC). Because the inductor, part of the transformer, is passing the stable current and blocking the unstable current, the LED only blinks when the button is on. When the diode is introduced to the circuit, the circuit loses the AC frequency rate and stabilizes into DC.
This is an experiment to show how to design a circuit immune to a voltage drop (weak battery). In the video, when one LED is lit, the circuit is connected to a modified 4.7 volt supply. When both LED's are lit, the circuit is connected to the 9 volt supply. The LED that lit both times is representing a circuit immune to voltage drops.
