arduino based LED Cube 8x8x8

LED Cube 8x8x8
Create your own 8x8x8 LED Cube 3-dimensional display!

We believe this Instructable is the most comprehensive step-by-step guide to build an 8x8x8 LED Cube ever published on the intertubes. It will teach you everything from theory of operation, how to build the cube, to the inner workings of the software. We will take you through the software step by step, both the low level drivers/routines and how to create awesome animations. The software aspect of LED cubes is often overlooked, but a LED cube is only as awesome as the software it runs.




About halfway through the Instructable, you will actually have a fully functional LED cube. The remaining steps will show you how to create the software.
I made this LED cube together with my friend chiller. The build took about 4 days from small scale prototyping to completed cube. Then another couple of hours to debug some faulty transistors.

The software is probably another 4-5 days of work combined.

Step 1: Skills required

At first glance this project might seem like an overly complex and daunting task. However, we are dealing with digital electronics here, so everything is either on or off!

I've been doing electronics for a long time, and for years i struggled with analog circuits. The analog circuits failed over half the time even if i followed instructions. One resistor or capacitor with a slightly wrong value, and the circuit doesn't work.

About 4 years ago, I decided to give microcontrollers a try. This completely changed my relationship with electronics. I went from only being able to build simple analog circuits, to being able to build almost anything!

A digital circuit doesn't care if a resistor is 1k ohm or 2k ohm, as long as it can distinguish high from low. And believe me, this makes it A LOT easier to do electronics!

With that said, there are still some things you should know before venturing out and building this rather large project.

You should have an understanding of:

• Basic electronics. (We would recommend against building this as your very first electronics project. But please read the Instructable. You'll still learn a lot!)
• How to solder.
• How to use a multimeter etc.
• Writing code in C (optional. We provide a fully functional program, ready to go)

You should also have patience and a generous amount of free time

Step 2: Component list

Here is what you need to make a LED cube:

• 512x  LEDs (plus some extra for making mistakes!)
• 64x resistors. (see separate step for ohm value)
• 1x or 2x large prototype PCBs. The type with copper "eyes", see image.
• 1x ATmega32 microcontroller (you can also use the pin-compatible ATmega16)
• 3x status LEDs. You choose color and size.
• 3x resistors for the status LEDs.
• 8x 74HC574 ICs
• 16x PN2222 transistors
• 16x 1k resistors
• 1x 74HC138 IC
• 1x Maxim MAX232 IC
• 1x 14.7456 MHz crustal
• 2x 22pF ceramic capacitors
• 16x 0.1uF ceramic capacitors
• 3x 1000uF electrolytic capacitor
• 3x 10uF electrolytic capacitor
• 1x 100uF electrolytic capacitors
• 8x 20 pin IC sockets
• 1x 40 pin IC socket
• 2x 16 pin IC socket
• 1x 2-pin screw terminal
• 1x 2wire cable with plugs
• 9x 8-pin terminal pins
• 1x 4-pin terminal pins, right angle
• 2x 16-pin ribbon cable connector
• 1x 10-pin ribbon cable connector
• Ribbon cable
• 2x pushbuttons
• 2x ribbon cable plugs
• 9x 8-pin female header plugs
• Serial cable and 4pin female pin header
• Piece of wood for template and base
• 8x optional pull-up resistors for layers
• 5v power supply (see separate step for power supply)

Step 3: Ordering components

We see a lot of people asking for part numbers for DigiKey, Mouser or other big electronics stores.

When you're working with hobby electronics, you don't necessarily need the most expensive components with the best quality.

Most of the time, it is more important to actually have the component value at hand when you need it.

We are big fans of buying really cheap component lots on eBay. You can get assortments of resistor, capacitors, transistors and everything in between. If you buy these types of assortments, you will almost always have the parts you need in your part collection.

For 17 USD you can get 2000 resistors of 50 different values. Great value, and very convenient.

Try doing som eBay searches and buy some components for future projects!

Another one of our favorite stores is Futurlec (http://www.futurlec.com/). They have everything you need. The thing they don't have is 1000 different versions of that thing that you need, so browsing their inventory is a lot less confusing than buying from those bigger companies.

Step 4: What is a LED cube

A LED cube is like a LED screen, but it is special in that it has a third dimension, making it 3D. Think of it as many transparent low resolution displays. In normal displays it is normal to try to stack the pixels as close as possible in order to make it look better, but in a cube one must be able to see trough it, and more spacing between the pixels (actually it's voxels since it is in 3d) is needed. The spacing is a trade-off between how easy the layers behind it is seen, and voxel fidelity.

Since it is a lot more work making a LED cube than a LED display, they are usually low resolution. A LED display of 8x8 pixels is only 64 LEDs, but a LED cube in 8x8x8 is 512 LEDs, an order of magnitude harder to make! This is the reason LED cubes are only made in low resolution.

A LED cube does not have to be symetrical, it is possible to make a 7x8x9, or even oddly shaped ones.

This LED cube has 512 LEDs. Obviously, having a dedicated IO port for each LED would be very impractical. You would need a micro controller with 512 IO ports, and run 512 wires through the cube.

Instead, LED cubes rely on an optical phenomenon called persistence of vision (POV).

If you flash a led really fast, the image will stay on your retina for a little while after the led turns off.

By flashing each layer of the cube one after another really really fast, it gives the illusion of a 3d image, when int fact you are looking at a series of 2d images stacked ontop oneanother. This is also called multiplexing.

With this setup, we only need 64 (for the anodes) + 8 (for each layer) IO ports to control the LED cube.

In the video, the process is slowed down enough for you to see it, then it runs faster and faster until the refresh rate is fast enough for the camera to catch the POV effect.

Step 6: The anatomy of a LED cube

We are going to be talking about anodes, cathodes, columns and layers, so lets take a moment to get familiar with the anatomy of a LED cube.

An LED has two legs. One positive (the anode) and one negative (cathode). In order to light up an LED, you have to run current from the positive to the negative leg. (If i remember correctly the actual flow of electrons is the other way around. But let's stick to the flow of current which is from positive to negative for now).

The LED cube is made up of columns and layers. The cathode legs of every LED in a layer are soldered together. All the anode legs in one column are soldered together.

Each of the 64 columns are connected to the controller board with a separate wire. Each column can be controlled individually. Each of the 8 layers also have a separate wire going to the controller board.

Each of the layers are connected to a transistor that enables the cube to turn on and off the flow of current through each layer.

By only turning on the transistor for one layer, current from the anode columns can only flow through that layer. The transistors for the other layers are off, and the image outputted on the 64 anode wires are only shown on the selected layer.

To display the next layer, simply turn off the transistor for the current layer, change the image on the 64 anode wires to the image for the next layer. Then turn on the transistor for the next layer. Rinse and repeat very very fast.

The layers will be referred to as layers, cathode layers or ground layers.
The columns will be referred to as columns, anode columns or anodes.

Step 7: Cube size and IO port requirements

To drive a LED cube, you need two sets of IO ports. One to source all the LED anode columns, and one to sink all the cathode layers.

For the anode side of the cube, you'll need x^2 IO ports, where x^3 is the size of your LED cube. For an 8x8x8 (x=8), you need 64 IO ports to drive the LED anodes. (8x8). You also need 8 IO ports to drive the cathodes.

Keep in mind that the number of IO ports will increase exponentially. So will the number of LEDs. You can see a list of IO pin requirement for different cube sizes in table 1.

For a small LED cube, 3x3x3 or 4x4x4, you might get away with connecting the cathode layers directly to a micro controller IO pin. For a larger cube however, the current going through this pin will be too high. For an 8x8x8 LED cube with only 10mA per LED, you need to switch 0.64 Ampere. See table 2 for an overview of power requirements for a LED layer of different sizes. This table shows the current draw with all LEDs on.

If you are planning to build a larger cube than 8x8x8 or running each LED at more than 10-ish mA, remember to take into consideration that your layer transistors must be able to handle that load.

Step 8: IO port expansion, more multiplexing

We gathered from the last step that an 8x8x8 LED cube requires 64+8 IO lines to operate. No AVR micro controller with a DIP package (the kind of through hole chip you can easily solder or use in a breadboard, Dual Inline Package) have that many IO lines available.

To get get the required 64 output lines needed for the LED anodes, we will create a simple multiplexer circuit. This circuit will multiplex 11 IO lines into 64 output lines.

The multiplexer is built by using a component called a latch or a flip-flop. We will call them latches from here on.

This multiplexer uses an 8 bit latch IC called 74HC574. This chip has the following pins:

• 8 inputs (D0-7)
• 8 outputs (Q0-7)
• 1 "latch" pin (CP)
• 1 output enable pin (OE)

The job of the latch is to serve as a kind of simple memory. The latch can hold 8 bits of information, and these 8 bits are represented on the output pins. Consider a latch with an LED connected to output Q0. To turn this LED on, apply V+ (1) to input D0, then pull the CP pin low (GND), then high (V+).

When the CP pin changes from low to high, the state of the input D0 is "latched" onto the output Q0, and this output stays in that state regardless of future changes in the status of input D0, until new data is loaded by pulling the CP pin low and high again.
To make a latch array that can remember the on/off state of 64 LEDs we need 8 of these latches. The inputs D0-7 of all the latches are connected together in an 8 bit bus.

To load the on/off states of all the 64 LEDs we simply do this: Load the data of the first latch onto the bus. pull the CP pin of the first latch low then high. Load the data of the second latch onto the bus. pull the CP pin of the second latch low then high. Load the data of the third latch onto the bus. pull the CP pin of the third latch low then high. Rinse and repeat.

The only problem with this setup is that we need 8 IO lines to control the CP line for each latch. The solution is to use a 74HC138. This IC has 3 input lines and 8 outputs. The input lines are used to control which of the 8 output lines that will be pulled low at any time. The rest will be high. Each out the outputs on the 74HC138 is connected to the CP pin on one of the latches.

The following pseudo-code will load the contents of a buffer array onto the latch array:

// PORT A = data bus
// PORT B = address bus (74HC138)
// char buffer[8] holds 64 bits of data for the latch array

PORTB = 0x00; // This pulls CP on latch 1 low.
for (i=0; i < 8; i++)
{

PORTA = buffer[i];
PORTB = i+1;

}

The outputs of the 74HC138 are active LOW. That means that the output that is active is pulled LOW. The latch pin (CP) on the latch is a rising edge trigger, meaning that the data is latched when it changes from LOW to HIGH. To trigger the right latch, the 74HC138 needs to stay one step ahead of the counter i. If it had been an active HIGH chip, we could write PORTB = i; You are probably thinking, what happens when the counter reaches 7, that would mean that the output on PORTB is 8 (1000 binary)on the last iteration of the for() loop. Only the first 8 bits of PORT B are connected to the 74HC138. So when port B outputs 8 or 1000 in binary, the 74HC138 reads 000 in binary, thus completing its cycle. (it started at 0). The 74HC138 now outputs the following sequence: 1 2 3 4 5 6 7 0, thus giving a change from LOW to HIGH for the current latch according to counter i.

Step 9: IO port expansion, alternative solution

There is another solution for providing more output lines. We went with the latch based multiplexer because we had 8 latches available when building the LED cube.

You can also use a serial-in-parallel out shift register to get 64 output lines. 74HC164 is an 8 bit shift register. This chip has two inputs (may also have an output enable pin, but we will ignore this in this example).

• data
• clock

Every time the clock input changes from low to high, the data in Q6 is moved into Q7, Q5 into Q6, Q4 into Q5 and so on. Everything is shifted one position to the right (assuming that Q0 is to the left). The state of the data input line is shifted into Q0.

The way you would normally load data into a chip like this, is to take a byte and bit-shift it into the chip one bit at a time. This uses a lot of CPU cycles. However, we have to use 8 of these chips to get our desired 64 output lines. We simply connect the data input of each shift register to each of the 8 bits on a port on the micro controller. All the clock inputs are connected together and connected to a pin on another IO port.

This setup will use 9 IO lines on the micro controller.

In the previous solution, each byte in our buffer array was placed in it's own latch IC. In this setup each byte will be distributed over all 8 shift registers, with one bit in each.

The following pseudo-code will transfer the contents of a 64 bit buffer array to the shift registers.

// PORT A: bit 0 connected to shift register 0's data input, bit 1 to shift register 1 and so on.
// PORT B: bit 0 connected to all the clock inputs
// char buffer[8] holds 64 bits of data

for (i=0; i < 8; i++)
{

PORTB = 0x00; // Pull the clock line low, so we can pull it high later to trigger the shift register
PORTA = buffer[i]; // Load a byte of data onto port A
PORTB = 0x01; // Pull the clock line high to shift data into the shift registers.

}

This is perhaps a better solution, but we had to use what we had available when building the cube. For the purposes of this instructable, we will be using a latch based multiplexer for IO port expansion. Feel free to use this solution instead if you understand how they both work.

With this setup, the contents of the buffer will be "rotated" 90 degrees compared to the latch based multiplexer. Wire up your cube accordingly, or simply just turn it 90 degrees to compensate ;) 

There is another solution for providing more output lines. We went with the latch based multiplexer because we had 8 latches available when building the LED cube.

You can also use a serial-in-parallel out shift register to get 64 output lines. 74HC164 is an 8 bit shift register. This chip has two inputs (may also have an output enable pin, but we will ignore this in this example).

• data
• clock

Every time the clock input changes from low to high, the data in Q6 is moved into Q7, Q5 into Q6, Q4 into Q5 and so on. Everything is shifted one position to the right (assuming that Q0 is to the left). The state of the data input line is shifted into Q0.

The way you would normally load data into a chip like this, is to take a byte and bit-shift it into the chip one bit at a time. This uses a lot of CPU cycles. However, we have to use 8 of these chips to get our desired 64 output lines. We simply connect the data input of each shift register to each of the 8 bits on a port on the micro controller. All the clock inputs are connected together and connected to a pin on another IO port.

This setup will use 9 IO lines on the micro controller.

In the previous solution, each byte in our buffer array was placed in it's own latch IC. In this setup each byte will be distributed over all 8 shift registers, with one bit in each.

The following pseudo-code will transfer the contents of a 64 bit buffer array to the shift registers.

// PORT A: bit 0 connected to shift register 0's data input, bit 1 to shift register 1 and so on.
// PORT B: bit 0 connected to all the clock inputs
// char buffer[8] holds 64 bits of data

for (i=0; i < 8; i++)
{

PORTB = 0x00; // Pull the clock line low, so we can pull it high later to trigger the shift register
PORTA = buffer[i]; // Load a byte of data onto port A
PORTB = 0x01; // Pull the clock line high to shift data into the shift registers.

}

This is perhaps a better solution, but we had to use what we had available when building the cube. For the purposes of this instructable, we will be using a latch based multiplexer for IO port expansion. Feel free to use this solution instead if you understand how they both work.

With this setup, the contents of the buffer will be "rotated" 90 degrees compared to the latch based multiplexer. Wire up your cube accordingly, or simply just turn it 90 degrees to compensate ;) 

Step 10: Power supply considerations

This step is easy to overlook, as LEDs themselves don't draw that much current. But remember that this circuit will draw 64 times the mA of your LEDs if they are all on. In addition to that, the AVR and the latch ICs also draws current.

To calculate the current draw of your LEDs, connect a led to a 5V power supply with the resistor you intend to use, and measure the current in mA. Multiply this number by 64, and you have the power requirements for the cube itself. Add to that 15-20 mA for the AVR and a couple of mA for each latch IC.

Our first attempt at a power supply was to use a step-down voltage regulator, LM7805, with a 12V wall wart. At over 500mA and 12V input, this chip became extremely hot, and wasn't able to supply the desired current.

We later removed this chip, and soldered a wire from the input to the output pin where the chip used to be.

We now use a regulated computer power supply to get a stable high current 5V supply

Step 11: Buy a power supply

If you don't have the parts necessary to build a 5V PSU, you can buy one.

eBay is a great place to buy these things.

Search for "5v power supply" and limit the search to "Business & Industrial", and you'll get a lot of suitable power supplies. About 15 bucks will get you a nice PSU.
source:http://www.instructables.com/

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Human Detection Robot

Human detection robot is not a new technology. Many types of human detection robots were designed depending on the application. During the natural calamities like earthquakes, it is difficult to rescue the human beings under the buildings. Though detection by rescue team is done, it consumes a lot of time. Detection of human in appropriate time is very important in such situations. This article presents a simple human detection robot that is operated manually using RF technology.

Circuit Principle:

The main principle of the circuit is to detect the human using human detection sensor. The wireless robot is operated manually using PC. The wireless technology used here is Radio Frequency technology. The data is transmitted to receiver through RF. Using the received data, robot is operated and controlled.

Circuit Diagram:

Transmitter Circuit

Receiver Circuit:

Circuit Components:

• AT89s51 microcontroller.
• PIR sensor.
• RF transmitter and receiver.
• L293D IC.
• PC.
• Robot chassis.
• Max232 IC.
• 9V battery.
• Motors.

How to Design:

The circuit can be divided into two sections 1) Transmitter Section, 2) Receiver Section.

Transmitter Section:

The transmitter section consists of PC, RF transmitter, MAX232IC, DB9 connector. The commands for operating the robots are transmitted using Personal computer. PC transmits the data to the RF transmitter through max232.

Max232 converts the logic levels. The logic levels of PC are in the range ± 3v to ± 15V, while the logic levels of RF module is compatible with TTL.In order to convert this voltage MAX 232 is used .This is also called level converter .The T1in pin of the MAX232 is connected to the receive pin of the DB9 which is in turn connected to the PC. The output pins are connected to the RF transmitter.

Radio frequency is the wireless technology used here to transmit the data .Several carrier frequencies were used in available modules such as  433.92 MHZ,315MHZ ,868MHZ,915MHZ,2400MHZ .Here the RF modules uses a frequency of  433 MHZ. The DATA pin of the RF transmitter is connected to the T1out of the MAX232.A Vcc of 5v is applied to the RF transmitter.

Receiver Section:

The receiver section consists of AT89c51microcontroller, L293D motor driver IC, RF receiver, motors of the robot, PIR sensor.

AT89c51 is an 8051 family microcontroller. It is an 8-bit microcontroller. It has 40pins.It has flash memory of 4K bytes.

 The RF receiver module is connected to the port3 of the microcontroller. Data pins of RF receiver are connected to the receiver pin of the microcontroller. The two Vcc pins are shorted and connected to a supply of 5v.GND pins are shorted and connected to ground. The receiver module receives the data and transmits it to the microcontroller.

PIR sensor plays a main role in the circuit. This is used to detect the human beings. The PIR sensor is nothing but Passive Infra Red sensor. These sensors work on the principle that they every human being emits infra red radiations of very low wave length. Thus this sensor senses these radiations and outputs a logic high value. This sensor can sense the human within the range of 20feet. They have an operating voltage of 2.2-5V. PIR sensor is connected to the Port1 of the micro controller.

L293D is a motor drive IC. This IC is required to drive the motor and also eliminates back EMF generated. This IC internally has H-bridge circuit. This has 16 pins out of which four input pins are used to drive two motors. Enables are used to enable these input pins. A supply voltage of 5v is applied at the 16th pin to operate the IC.8th pin is applied with a voltage of 12v required to drive the motors. The L293D IC can drive voltages up to 36v.That is 8th pin can be applied with a voltage ranging from 2.4v to 36v.source:www.electronichub.com

Security Alarm Circuit

This circuit will help you to guard your precious documents as well as jewellery from intruders or theft. All you need is just to place this circuit in front of the locker or below the mat so when any unknown person come and walk over the switch, the circuit will trigger and sound of alarm comes. The main benefit of the circuit is that these can be implied in two places at a time as two different switches produces two different sounds.

Circuit Components:

• Resistor
• R1, R2 (100K) – 2
• R3 (1.2K) – 1
• R4 (47E) – 1
• T1 (BC547) – 1
• T2 (BC558) – 1
• D1, D2 (1N4007) – 2
• C1 (. 1uf) – 1
• S1, S2 – 2
• Speaker – 1

1. Resistor: Resistors are the passive device with two terminals. They are mainly used in the circuit to restrict the flow of current across any of the circuits. The current flow from the resistor is directly proportional to the voltage that is given across the terminals of the resistor. In the market resistors are mainly available in two broad categories:
   1. Fixed resistor–  It actually means that the resistor whose value cannot be change and remain what its mark on it.
   2. Variable Resistor-  It means that the value of resistance can vary within the range marked over it. For e.g. If the value of 5k is marked on it then it implies that the value of the resistor can vary from 0-5k.
      • The value of the resistor can be calculated either with the help of multimeter or with the help of color code over the resistor.
2. Diodes – It is a device with two terminals and have a asymmetric attribute which means that it permit the flow of current in one of the directions while the flow of high resistance is from another direction. Hence in it flow of current is in one way only and block the other way for the current flow. The two terminals in diode named as anode and cathode. AC current can be converted into DC with the help of diode unidirectional behaviour.
3. Transistor – transistor is a three terminal electronic device used to amplify weak input signals. A transistor consist of two PN junction diode connected back to back. Transistor are of different type such as bipolar junction transistor, Field effect transistor and photo transistor. They are mostly used in electrical appliances due their smaller size and light weight. In addition they posses less power hence have greater efficiency.
4. Speaker- it is a transducer which creates sound in reaction of the electrical auditory signal given in the input.
5. Capacitor– Electric charges are being stored by these two terminal components which is passive by nature. A dielectric medium is used which is used to separate two conductors. It started at the time when the potential variation occurs in the conductors polarizes the dipole ions to hold the charge in the medium which is dielectric. There are two varieties of capacitor available in the market –
   1. Polarized capacitor- Capacitor marked with – and + sign. They are mainly used to hold the charge. And before troubleshooting these capacitors carefully discharge them as they hold charges there is a risk of shock.
   2. Non polarized capacitor –  Capacitors which do not have any polarity marked over it. They are mainly used to remove the noises appeared while converting AC into DC.

Important Post: Pull Pin Security Alarm Circuit

Working of Security Alarm Circuit:

S1 and S2 are the two switches that are used in the circuit so that both can be put in two different places i.e. one of them can put in front of the locker while another one can be placed on the front door. When the switch S1 is pressed diode D1 which is linked with it starts conducting as the transistor T1 and T2, which is attached with the resistor begin its conduction. For the oscillation purpose Transistor T1 and T2 gets a positive feedback which is provided by capacitor C1. The presence of any intruder is indicated by the low tone frequency which is generated when switch S1 is pressed.

Same kind of condition occurs when switch S2 is pressed. Diode D2 which is linked with the switch S2 begin its conduction and offers power supply the transistor T1 and T2, which is in the waking state and as a result sound comes from the speaker attached to it. But in this instance a high frequency tone comes out which is a sign that there is some intruder present around the locker. The sound that came from the speaker can only be stopped by cut off the power supply.source:http://www.electronicshub.org/

Bike Turning Signal Circuit

We know the use of bike indicators. These are used to indicate left turn or right turn. Have you ever tried to design bike turning indicators. This article explains you how to design these bike turning indicators.

Bike Turning Signal Circuit Principle:

The objective of this circuit is to indicate left or right turn for bike/vehicle. Two identical circuits are needed, one is for left and the other is for right. The main heart of this circuit is 555 timer. Here, this 555 timer acts as an astable multi vibrator. It generates the pulse signal with variable width. Using this variable width of the pulse, we can set different time delays for the LEDs (ON and OFF for LEDs).

The circuit consists of two 47k resistors, which are connected to 555 timer and these are used to set the time delay for LEDs. 1n4148 signal diode is connected in reverse bias at the output to maintain constant current at the output. BC547 (NPN) Transistor switches the LED’s ON and OFF based on the base currents. 330 ohm resistors are used to drop the voltage otherwise LEDs may get damaged. Here we can vary the time width of output pulse by varying the resistance or capacitance value.

Bike Turning Signal Circuit Diagram:

Circuit Components:

• Resistors       –  3 (47 k ohm)
• Resistors       –  5 (10 k ohm)
• Resistors       -5 (330 ohm)
• Capacitors    – 2 (100uF)
• Transistors   – 5 (BC547)
• LED’s              – 10 (5 mm)
• IC                    – 1 (NE555)
• Diodes           – 2 (1n4148)
• Battery          – 1 (12V)
• wires

Bike Turning Signal Indicator Circuit Design:

In this circuit, 555 timer produces pulse signal with variable width. The pulse width is varied by varying resistance or capacitance value (R2, R1). 2 and 6 pins are shorted to allow triggering after every timing cycle. Fourth pin is reset, it is shorted with VCC (8th pin) to avoid sudden resets. 7th pin is discharging pin, it is connected to 6th pin through a 47k resistor. The below figure explains you the operation of 555 timer. In this circuit capacitor C charges through resistors Ra and Rb. Now because of internal op-amps, capacitor C discharges through resistor Rb. 555 timer internally consist of 2 operational amplifiers, one D flip flop and one NPN transistor.

In the above circuit, the pulse is generated at the 3rd pin of the 555 timer. By varying the values of Ra, Rb, C we can vary the pulse width. The total time period of the pulse is given as

T = THIGH + TLOW = 0.693 (RA+ 2RB) C

 Frequency of the pulse is given as

f = 1/T = 1.44/ (RA+ 2RB)C

percentage of duty cycle is given as

% duty cycle, D = tc / T * 100 = (RA + RB) / (RA + 2RB) * 100

The obtained pulse from the 555 timer is applied to the transistors to switch the LEDs ON and OFF with some delay. Here the operating voltage of LEDs is around 2 to 3v but from battery, we get 12v supply. So, we need to drop the remaining voltage. To drop this voltage, we are using resistors in series with LEDs. 

How to Operate the Circuit?

• Initially feed 12v power supply to the circuit.
• Now observe the LED’s they will glow with some delay.
• If you want, set the different time delays for LEDs, and then vary the resistance or capacitance value.
• Now you can see the change in time delay.
• By varying the capacitance value also you can see the in time delay of LEDs.
• source:http://www.electronicshub.org/

TV Remote Jammer Circuit

We have already seen in the earlier posts about how to jam the mobile signals using simple mobile jammer circuit. Now, In this post, we are going to know about another interesting concept i.e. TV Remote jammer circuit. It is designed using NE555 Timer IC.

This proposed TV jammer circuit confuses the infrared receiver in a TV by producing the constant signal that interferes the remote control signal. If you switch on the circuit once, the TV will not receive any command from the remote. This allows you to watch your own program without anyone changing the channel or volume.

The fundamental technology used in TV Remotes is Infrared light. This infrared light is invisible to the human eye, but we can see these IR rays through camera.

TV Remote Control Jammer Circuit Principle:

The idea behind TV remote control jammer is sending a constant IR pulse with the carrier frequency of the transmitter. Hence the result will be non-accepted signal from the receiver and therefore no action will be taken.

Basically the TV remote emits a sequence of pulses when you press a button. IR transmitter is fixed to the surface of the TV remote. This IR transmitter emits the pulses in unique configuration for each button.

IR receiver which is arranged to TV will receive these sequence of pulses that are transmitted by TV Remote and identifies which button is pressed in TV remote.

Generally Philips TV remotes follows RC5 (Remote Control) protocol. This protocol was developed by Philips in the late 1980s. According to this protocol, for each button, Remote transmits 14 bits. The below figure shows the frame format of RC5 protocol.

The first two pulses are start bits, and both are logic 1.

The 3rd bit is toggle bit. This bit toggled every time when a button is pressed or released. Using this bit, we can identify weather the button is pressed or not.

The next 5 bits represent the device address. Bit 4 is the MSB of the device address and bit 8 is the LSB of the device.

Last six bits in the frame format are command bits. These command bits varies for each button in the remote. Using these command bits, we can identify which button is pressed in IR remote.

Features of RC5 protocol:

1. Bi-phase coding (Manchester coding)
2. 36Khz or 38Khz carrier frequency
3. Constant bit time of 1.778ms
4. 5 bit address and 6 bit command length

Modulation: The RC5 protocol uses bi – phase modulation. All 14 bits are equal length of 1.778ms.
source:electronicshub.org