top of page

INKOGNITO Group

Veřejná·144 členů

The Next To Minimal Infrared Transmitter For Pc !EXCLUSIVE!



Infrared light transmission has been the standard for line-of-sight type A/V remote controls since the early 1980s. IR transmitters use near-infrared light which is just below the visible spectrum [Factoid: remote control IR transmitted signals can be seen with digital cameras and camcorders as appearing to be visible, purple light]. By using near-IR wavelengths, manufacturers can use cheap, plentiful, IR LEDs which are nearly identical to their visible-light counterparts save for emitting frequencies just below what the human eye can detect.




the next to minimal infrared transmitter for pc



IR emitters are small wired transmitters for repeating an infrared signal from your remote to an isolated piece of A/V equipment. They are available in single or dual emitter packages with the latter emitting the same signal through two separate housings. Furthermore, emitters also come in blink or blast-style transmission variations with the former being the most common. Blink-style IR emitters blink visibly as well as in infrared and are used to transmit data to a single component source. Blast-style emitters on the other hand, transmit data into several component sources at once and are used when space is a premium. Blast-type emitters are considered a somewhat less reliable transmission method than blink-type.


These headphones use what is known as line-of-sight technology, meaning you must be lined up with the transmitter (within line of sight) in order to receive sound from your TV. At its core, infrared technology comprises light-emitting diodes that utilize a focused beam of pulsating, invisible light from your TV to the headphones.


An IR transmitter LED, on the other hand, is a device that emits infrared light in order to send signals to other devices. It is typically a small, clear, or translucent device that emits IR light in a specific frequency range. IR transmitter LEDs are commonly used in remote controls and other IR signaling devices.


Consumer IR devices use an infrared LED in the handheld remote and an IR receiver located inside the device. Since sunlight and ambient room lighting would interfere with any IR detector just looking at light levels, the signal modulates (i.e. turns on and off) a high frequency carrier signal. This is called amplitude shift keying(ASK). Typically for IR, the frequency is in the 30-60Khz range with 38Khz being the most common carrier frequency. There are a few early first generation electronic ballasts for fluorescent lights operating this range that can cause interference with IR remotes, but in most cases it works well. This means that the IR LED transmitter must be modulated. On mbed, this can be done using the PWM hardware. The IR detector modules have a built-in bandpass filter and hardware to demodulate and recover the original signal.Sparkfun IR LED transmitter moduleThe Sparkfun IR LED breakout board seen above contains a 50MA high output IR LED and a driver circuit using a transistor as seen in the schematic below. An IR Led can be used instead now that this board is no longer available, but the circuit still needs the correct polarity to control the LED on/off state, since the serial port's internal UART receiver hardware must have a low start bit and a high stop bit to work. A discrete IR LED should have an operating voltage of around 1.5V, so don't forget the series voltage dropping resistor!


Characters typed in PC terminal window echo back using the RF linkThe demo is started on mbed and a terminal application window is started on the PC using mbed's virtual com port. As seen above in the demo, any character typed in the PC's terminal application window is sent out over the serial port, transmitted and received using the RF link, read back in on the serial port, and echoed back in the terminal application window. Keep in mind that any RF link will occasionally experience errors and is subject to interference from other RF sources nearby, cosmic radiation, and thunderstorms. If you happen to have a car key fob that operates at 315MHz (or 434Mhz in Europe and Asia), try holding it right next to the receiver antenna when running the demo and hit a button. Typically, you will see a long random looking string of characters when it generates and transmits the encrypted code for the button. If you disconnect power to the transmitter chip, the receiver's AGC will crank up the gain until it starts sending out the background RF noise converted to random strings of ASCII characters.


I improved Remin's protocol by setting up the link software so that timing constraints on the IR receiver AGC were guaranteed to be met. It turns out that there are several types of IR reciever, some of which are better at short data bursts, while others are better for sustained data. I chose a Vishay TSOP34156 for its good sustained data characteristics, minimal burst timing requirements, and reasonable data rate. The system I build works solidly at 4800 baud over IR with 5 characters of overhead/packet (start token, transmitter number, 2 char checksum , end token). It works with increasing packet loss up to 9000 baud. The receiver circuit is shown to the left. The RC circuit acts a low-pass filter on the power to surpress spike noise and improve receiver performance. The RC circuit should be close to the receiver. The range with a 100 ohm resistor is at least 3 meters with the transmitter roughly pointing at the receiver, and a packet loss of less then 0.1 percent. To manage burst length limitations there is a short pause between characters, and only 7-bit characters are sent, with two stop bits. The 7-bit limit means that you can send all of the printing characters on the US keyboard, but no extended ASCII. All data is therefore sent as printable strings, NOT as raw hexidecimal.


ListenIR is the first infrared assistive listening system to feature expansion radiators, which provide delay compensation to ensure that there are no signal cancellation dropouts. When combining a transmitter with extension transmitters, signal timing features eliminate delayed audio signals. Everyone hears the same message at the same time.


The Quasar 900 consists of a Xenon Flash infrared transmitter and infrared receiver, separated over a line of sight from 23 ft (7m) up to 660 ft (200m) in extremely harsh environments where dust, fog, rain, snow or vibration can cause a high reduction of signal.


The Z-Wave Smart Meter Sensor is a compact sensor designed to read meter values from traditional electromechanical and electronic meters with optical port. The sensor is easy to install and ideal for precise meter reading down to 0,1kwh. Its compact size and external wireless transmitter makes it easy to install in any distribution board. The device is battery powered (will last about 1 year) and reports the meter value once in 15 minutes. If there won"t be a Z-Wave network, the device will store values up to 3 month. This ensures, that the system can even be used in a minimal configuration with a simple Z-Wave USB Stick (Not part of delivery!) connected to a PC.


O nás

Welcome to the group! You can connect with other members, ge...

členů

  • petra
  • ctv04entity
  • David Jay T
    David Jay T
  • Reno Smidt
    Reno Smidt
  • Maruvs Maruvs
    Maruvs Maruvs
bottom of page