Crystal Oscillators
This uses a piece of quartz that is cut and polished to vibrate at a certain frequency, a crystal oscillator is a piezoelectric (a strain generates a voltage and vice versa). The microcontroller has an on-chip oscillator, which must be run by an external clock signal. A quartz crystal is configured into an oscillator with capacitors to provide the clock signal. A quartz crystal emits a pulse at a fixed frequency when energy is applied to it.
The use the clock signal provided by the crystal to synchronize its operations. They operate using what are called “machine cycles”. A single machine cycle is the minimum amount of time in which a single instruction can be a machine cycle is 12 pulses of the crystal executed. A 6 MHz crystal was used in this work.
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Bluetooth Enabled LED Display Board. Ep13.
5 days ago
ghost69 in science
Crystal Oscillators
This uses a piece of quartz that is cut and polished to vibrate at a certain frequency, a crystal oscillator is a piezoelectric (a strain generates a voltage and vice versa). The microcontroller has an on-chip oscillator, which must be run by an external clock signal. A quartz crystal is configured into an oscillator with capacitors to provide the clock signal. A quartz crystal emits a pulse at a fixed frequency when energy is applied to it.
Diagram of crystal oscillator
The use the clock signal provided by the crystal to synchronize its operations. They operate using what are called “machine cycles”. A single machine cycle is the minimum amount of time in which a single instruction can be a machine cycle is 12 pulses of the crystal executed. A 6 MHz crystal was used in this work.
The number of instructions per second the will perform is then the quartz crystal is connected Cmos input XTAL (pin 19) of the microcontroller. Two capacitors. 30pf each are connected to the crystal to make it impossible for frequencies other than that generated by the crystal to penetrate (Tocci . R.J et al 2003).
Resistors
A resistor is a passive component. It is essential to the function of almost every electrical circuit. It provides a means of controlling the current and for a voltage presents in the circuit, it is fixed. A resistor is a component that opposes or restricts the flow of electrons (electricity) through it or otherwise shows electrical resistance. An ideal resistor obeys Ohm's law V= IR that is the voltage across a resistance is directly proportional to the current through it. Resistance being constant of proportionality. Where I, is in Amperes. (A), V is in volts (v) and R in ohms (Ω). There are mainly two of resistors (a) fixed value resistors (a) variable type resistor.
Micro-Controller Card
The card is the major circuit of the design. It is made up of ROM, RAM and CPU etc. it has register memory locations where the software that runs the system is contained. It has four standard ports (port 0-3) and all the ports can be used, unlike the INTEL micro-controller which only two of its ports can be used to interface the processor to an external memory device usually EPROM through a latch (MAX7219). This makes it easier such a complex design whereby port 2 & 3 are connected to the LED Drivers respectively and port 0 is connected to the transistors to the display board. The serial number of the LED driver IC used is MAX7219.
This is the final module where the information from the micro-controller finally displays itself for the view. The display module is made up of eleven characters is containing 8 x 32 dot matrix array. This array is achieved with a red light emitting diodes (LEDs). In each column, the positive pins are connected together throughout the while in each row are connected to the LED driver IC MAX7219. Note that in the L emitting diodes (LEDs). In each column, the positive pins are connected together throughout the while in each row are connected to the LED driver IC MAX7219. Note that in the switching, each of the LED driver IC is responsible for switching, each of the LED driver IC is responsible for the information that is displayed on a given 8 x 32 dot matrix screen while each of transistor is responsible for switching all the corresponding columns of the screen. All these sections/modules work as a group through individual to enhance the overall design. The maximum current needed by the LEDs = 25MA (for data sheet). The voltage entering the LEDs from the transistors is 5v. The transistor that may in turn damage it, a resistor of the value 1000Ω is used as a biasing resistor (Balmer, S. 2000).
The LED current can be calculated by the formula:
V =IR (ohm’s law).
Where
R = 220Ω V = 5
So that
I = V 5 = 2; R 1000
This current is still enough to make the LED show even brighter and last longer.
Capacitor
Capacitor of various types are used in electronic circuit for storing charges as element of frequency selective circuit and filter, for compiling A.C signals from one circuit to another and for shunting unwanted signal to ground capacitors can be divided broadly into two types: those that have a solid electric of ceramics or polymer and those that have a thin metal oxide film as dielectric (Tharaja, A.K. (1999).
They are called non-electrolytic capacitors respectively. Non-electrolytic capacitors non-electrolytic capacitors used in electronic engineering projects fall into many groups such as Mica, ceramic, and polymer film etc.
Electrolytic capacitors – they are used in circuit operation requiring a large value of capacitance, such as power supply circuit where they find use as reservoir capacitor, low-frequency filter, and timing circuits with a long time constant. In this project work, the capacitors find their way in filter resonant, timing and storing charges. Both electrolytic and non-electrolytic capacitors were used in this project design.
