* Infrared Transceiver for PC (Pc Based Slideshow)

Project code:- E38 Project Cost:- INR:- Rs. 3500/- USD:- 85$

Infrared Transceiver for  PC

This project does more then just describe an IR transceiver that you can use with your PC for remote control and data transfer. It also provides information about the principles of the infrared transfer technique used and interface technology, which you can use for your own projects.
Infrared data transfer is becoming increasingly more important.Television remote controls use infrared light,but so do PC mice, keyboards, printers and other peripherals.Infrared light is also used in fibre-optic cables.

Infrared Transceiver for PC Block Diagram  Infrared Transceiver for  PC Block Diagram

In a sense, the PC infrared transceiver presented here is a practical application Infrared remote controls for television sets,video recorders and other entertainment electronice devices frequently use the philips RC5 standard It is easy to determine whether a particular remote control employs RC5 by using the program described in this project.

This standard employs light signals modulated at a frequency in the range of 30 to 40 kHz.The remote control unit transmits ‘bursts’, which are individual pulse packets.In our case these bursts have a duration of either 0.888 ms or 1.776 ms. At a modulation frequency of 36 kHz,a short burst contains 32 indivdual pulses, while a long burst contains 64 pulses.

A complete data packet has a duration of approximately 25 ms and is repeated every 100 ms as long as a button is held depressed. An infrared remote control unit can easily be used for other purposes. For example, it can be used to control certain functions of your own program.A typical application is controlling a PC slide show.After starting the program, you can sit back and operate everything from where you are sitting.

Transceiver hardware
Thank to the availability of integrated receivers, the reception of standard infrared signals is relatively simple.The well-known siemens SHF506 is available with fixed modulation freqencies of 30 kHz,33 kHz and so on.The filter curve is relatively broad band,so deviations of a few kilohertz csuse only a relatively small reduction in sensitivity.The Vishai / Telefunken TSOP1836 is a similar IC. Both types of IC need only a 5-V supply voltage and draw less then 2 mA.

They can thus be powered directly from the PC serial interface. The IR transceiver described hear has a modulated IR transmitter works with a carrier frequency between 30 and 40 kHz.It can be used for the remote control of devices such as video recorders and television sets, but it can also be used for data transfer between two PCs.

The schematic diagram shown in Figure 1 reveals the receiver IC (IC3) and a 78L05 voltage regulator ( IC1).The supply voltage is taken from the DTR and RTS outputs of the RS232 interface, which are connected together via the isolating diodes D1 and D2.A voltage of around 10 V can be activated here using a program running on the PC.

These two leads also power the transmitter portion of the circuit via D6 and D7.since high pulse currents are needed for transmitting. A large electrolytic capacitor ( IC1,4.7 uF)is used to smooth the input voltage of the voltage regulator. If the IR receiver IC receives an infrared signal modulated at 36 kHz, it produces an output signal on its middle pin with an active-low level. these output pulses are connected directly to the CTS lead, where they must be decoded using software.

A supplementary pull-up resistor is necessary here, since the CTS lead has a relatively low input resistance.The signal is also inverted by a transistor stage ( T1 ) and applied to the RxD inputof the serial interface. This lead serves for the reception of fast data, for example from a data link between two PCs.

The infrared transmitter consists of a modulation stage ( IC2 )and a pulse amplifler ( T2 and T3 ) driving two infrared diodes ( D4 and D5 ). IC2 is a 555 timer IC wired as an oscillator, which generaed narrow negative pulses with a width of around 2 us.The frequency can be set between approximately 30 and 40 kHz using P1. Depending on the application, the trimpot can by used to tune the circuit to the suitable frequency in order to achieve the greatest possible range.

The 555 receives its supply voltage from the TXD lead, which modulates (’keys’) the transmitter by switching it on and off. The energy for the two IR transmitter diodes also comes from the serial interface. The DTR and RTS leads charge a 1-uF electrolytic capacitor (C5) via D6 and D7. The brief pulses on the output of the timer IC ( pin3) force the driver stage consisting of T2 and T3 into full conduction. This results in pulsed currents of approximately 200-300 mA.

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