TV Remote Control Jammer
This is a simple circuit that anyone can create for enjoyment. The project originated when there was an attempt to control a TV using the serial port of a computer. It took only a few minutes to grasp the basic functionality of remote controls, and even less time to construct a circuit for entertainment purposes. Due to the simplicity of this circuit, the focus will shift from explaining its operation to exploring how remote controls function. Despite the abundance of manuals, specifications, and tutorials available on remote control technology, a unique approach was taken. By connecting an oscilloscope to the infrared (IR) LED of a remote control and pressing various buttons, the transmitted signal was observed. For instance, pressing buttons 1 and 2 revealed the signal pattern. The transmission begins with a starting bit, followed by five consecutive bits of '1'. This is followed by nine bits of data, with the last two bits serving as end bits. The specific button pressed alters the transmitted pattern, with the numeric keys corresponding to their respective binary values. The first code corresponds to button 1 and the second code corresponds to button 2. If the binary numbers are mirrored and the bits inverted, the values 1 and 2 can be derived. The delay between pulses, or the signal period, is approximately 1 millisecond, which is useful for other projects but not crucial for this one. Upon closer examination of the pulses sent to the LEDs, it was noted that they do not appear as distinct rectangular pulses. This observation prompted further investigation with a faster time base on the oscilloscope, revealing that each pulse is composed of multiple smaller pulses, which represent the carrier frequency of the remote control, approximately 38.5 kHz in this case. Typically, remote controls operate within a carrier frequency range of 25 kHz to 45 kHz. This carrier wave helps differentiate the signals sent from the remote control from other ambient light sources. The receiver is equipped with a filter that permits only frequencies close to the carrier frequency to reach the decoder. To disrupt the receiver's functionality, a practical method involves covering the IR receiver with opaque tape. The concept is to confuse the receiver by continuously transmitting an IR pulse at the carrier frequency of the remote control. When a channel change is attempted using the remote, the IR pulse from the transmitter will interfere with the signals, resulting in a non-accepted signal and preventing any action. The circuit functions as a simple 555 astable multivibrator. Comprehensive details regarding the operation of the 555 timer can be found on relevant resources, along with a calculator for circuit design. The circuit's simplicity is notable, with a 2N2222 transistor utilized for switching the IR LEDs. It is recommended to use 5mm IR LEDs, although any type of IR LED may suffice with appropriate adjustments to the 150-ohm resistor. The output pulses' frequency is determined by the RC circuit of the 555 timer, which is composed of a 1K-ohm resistor.
The circuit described utilizes a 555 timer in astable mode to generate a continuous square wave signal, which is then used to modulate the IR LEDs. The frequency of the output signal is primarily determined by the resistor-capacitor (RC) network connected to the timer. The selected resistor and capacitor values dictate the timing intervals, thus influencing the pulse width and frequency of the output. The 2N2222 transistor acts as a switch, allowing the low-current output of the 555 timer to control the higher current required by the IR LEDs.
In practical applications, the circuit can be powered by a standard DC power supply, typically ranging from 5V to 15V, depending on the specifications of the 555 timer and the IR LEDs used. The design should ensure that the power supply voltage is compatible with the components to avoid damage.
The IR LEDs should be positioned to face the intended target, ensuring optimal transmission of the modulated signal. It is important to calculate the appropriate resistor value to limit the current flowing through the LEDs to prevent them from burning out. This is determined using Ohm's law, taking into account the forward voltage drop of the IR LEDs and the supply voltage.
This circuit can serve various practical purposes, such as creating a remote control jammer for educational demonstrations on signal interference or developing an understanding of how remote control systems operate. The simplicity of the design makes it an excellent project for beginners in electronics, providing hands-on experience with fundamental concepts such as oscillation, modulation, and signal processing.This is a very easy circuit that every one could make and have fun. This project popped out of nowhere, one day that i was trying to control the TV from the serial port of the computer. It took me no more than a few minutes to understand the simple method that the remote controls work, and even less time to make a circuit to have fun with my girlf
riend :) Because this circuit is easy enough for everyone to make, i decided, instead of writing how this circuit works, to get a little bit deeper on how remote controls work. Although there are tons of manuals, spec papers and tutorials on how those remotes work, i wanted to do it my way.
I connected the oscilloscope on the IR LED of my remote control and after some key presses and range selects, voila! The signal revealed. Let`s see for example what happens when i press the buttons 1 and 2. Then we will try to decode the signal transmitted. The signal is transmitted from left to right. A starting bit is first to be transmitted. Then, 5 aces (5x1) follows the signal. From then on, 9 bits will follow, and those bits are considered to be the data bits. The last two bits should be the end bits. According to what key we press, the transmitter will send this pattern, and the code bits shall change.
The buttons that i chose to send are not random. I run some tests and saw that when the numeric keys are pressed, the code bits will have the binary number of each button. The first (top) code was sent when we pressed the button 1, and the second code (bottom) was sent when we pressed key 2.
If you mirror the binary numbers and invert the bits, you will get the number 1 and 2: It should be taken into account that the delay from pulse to pulse, AKA period of the signal is approximately 1mSec. This is good to know for other projects, but for this project is irrelevant. Back to the oscilloscope for a closer look. If you look the pulses driven to the LEDs closer, you may notice that they are not very clear rectangular pulses.
That actually draw my attention and decided to press keys on the transmitter having a faster time base chosen on the oscilloscope. This would actually magnify the pulses. I chose a time division that would actually show one pulse to each screen. And here are the results!: Each pulse when is magnified, it appears to be composed from several other pulses.
Those pulses are actualy the carrier frequency of the remote control. In our case this carrier signal is about 38. 5KHz. In general, remote controls have carrier waves from 25KHz to 45KHz. This carrier wave is used to distinguish pulses sent from the remote control from other random and ambient light. The receiver has a filter that will allow only frequencies near the carrier frequency to be driven to the decoder.
If you have already read the previous section on how remote controls work, you may have already understand the trick yourself. The goal is to confuse-blind the receiver. A simple way would be to place some non transparent tape over the IR receiver. dooooh. Ok, the idea is to confuse the receiver by sending a constant IR pulse with the carrier frequency of the transmitter.
When someone tries for example to change a channel with the remote, the IR pulse from the transmitter will be combined with our pulses. The result will be a non-accepted signal from the receiver and therefore no action shall be taken. That`s all. The circuit is a simple 555 astable multivibrator. You can find detailed theory of the 555 timer operation in the pcbheaven pages, as well as a 555 timer calculator for your calculations.
There are not much to say about the circuit. The 2N2222 transistor is used for switching the IR LEDs. It would be better to use 5mm LEDs. Any kind of IR LEDs would fit but you may need to change the 150 Ohms resistor accordingly. The output pulses will have a frequency according to the RC circuit of the 555. This RC circuit is composed by the 1K resistor, the 🔗 External reference
The circuit described utilizes a 555 timer in astable mode to generate a continuous square wave signal, which is then used to modulate the IR LEDs. The frequency of the output signal is primarily determined by the resistor-capacitor (RC) network connected to the timer. The selected resistor and capacitor values dictate the timing intervals, thus influencing the pulse width and frequency of the output. The 2N2222 transistor acts as a switch, allowing the low-current output of the 555 timer to control the higher current required by the IR LEDs.
In practical applications, the circuit can be powered by a standard DC power supply, typically ranging from 5V to 15V, depending on the specifications of the 555 timer and the IR LEDs used. The design should ensure that the power supply voltage is compatible with the components to avoid damage.
The IR LEDs should be positioned to face the intended target, ensuring optimal transmission of the modulated signal. It is important to calculate the appropriate resistor value to limit the current flowing through the LEDs to prevent them from burning out. This is determined using Ohm's law, taking into account the forward voltage drop of the IR LEDs and the supply voltage.
This circuit can serve various practical purposes, such as creating a remote control jammer for educational demonstrations on signal interference or developing an understanding of how remote control systems operate. The simplicity of the design makes it an excellent project for beginners in electronics, providing hands-on experience with fundamental concepts such as oscillation, modulation, and signal processing.This is a very easy circuit that every one could make and have fun. This project popped out of nowhere, one day that i was trying to control the TV from the serial port of the computer. It took me no more than a few minutes to understand the simple method that the remote controls work, and even less time to make a circuit to have fun with my girlf
riend :) Because this circuit is easy enough for everyone to make, i decided, instead of writing how this circuit works, to get a little bit deeper on how remote controls work. Although there are tons of manuals, spec papers and tutorials on how those remotes work, i wanted to do it my way.
I connected the oscilloscope on the IR LED of my remote control and after some key presses and range selects, voila! The signal revealed. Let`s see for example what happens when i press the buttons 1 and 2. Then we will try to decode the signal transmitted. The signal is transmitted from left to right. A starting bit is first to be transmitted. Then, 5 aces (5x1) follows the signal. From then on, 9 bits will follow, and those bits are considered to be the data bits. The last two bits should be the end bits. According to what key we press, the transmitter will send this pattern, and the code bits shall change.
The buttons that i chose to send are not random. I run some tests and saw that when the numeric keys are pressed, the code bits will have the binary number of each button. The first (top) code was sent when we pressed the button 1, and the second code (bottom) was sent when we pressed key 2.
If you mirror the binary numbers and invert the bits, you will get the number 1 and 2: It should be taken into account that the delay from pulse to pulse, AKA period of the signal is approximately 1mSec. This is good to know for other projects, but for this project is irrelevant. Back to the oscilloscope for a closer look. If you look the pulses driven to the LEDs closer, you may notice that they are not very clear rectangular pulses.
That actually draw my attention and decided to press keys on the transmitter having a faster time base chosen on the oscilloscope. This would actually magnify the pulses. I chose a time division that would actually show one pulse to each screen. And here are the results!: Each pulse when is magnified, it appears to be composed from several other pulses.
Those pulses are actualy the carrier frequency of the remote control. In our case this carrier signal is about 38. 5KHz. In general, remote controls have carrier waves from 25KHz to 45KHz. This carrier wave is used to distinguish pulses sent from the remote control from other random and ambient light. The receiver has a filter that will allow only frequencies near the carrier frequency to be driven to the decoder.
If you have already read the previous section on how remote controls work, you may have already understand the trick yourself. The goal is to confuse-blind the receiver. A simple way would be to place some non transparent tape over the IR receiver. dooooh. Ok, the idea is to confuse the receiver by sending a constant IR pulse with the carrier frequency of the transmitter.
When someone tries for example to change a channel with the remote, the IR pulse from the transmitter will be combined with our pulses. The result will be a non-accepted signal from the receiver and therefore no action shall be taken. That`s all. The circuit is a simple 555 astable multivibrator. You can find detailed theory of the 555 timer operation in the pcbheaven pages, as well as a 555 timer calculator for your calculations.
There are not much to say about the circuit. The 2N2222 transistor is used for switching the IR LEDs. It would be better to use 5mm LEDs. Any kind of IR LEDs would fit but you may need to change the 150 Ohms resistor accordingly. The output pulses will have a frequency according to the RC circuit of the 555. This RC circuit is composed by the 1K resistor, the 🔗 External reference
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