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  • Infrared Extender with Microchip Op-Amp

  • Created: Sep 03, 2014

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Summary

This schematic allows the extension of range or coverage of infrared-controlled devices. Many consumer electronic devices such as television sets, DVD players, and many others employ infrared remote control system. It is ideal to cover a larger distance as possible to allow the control of the device even when the user is at a considerable distance from it.


In this circuit, the photodiode (D4) is connected to the inverting input of a 741 operational amplifier (op-amp) via the resistor R2 and capacitor C1. The photodiode needs to be reverse-biased thus it is connected to the positive supply through R1; this allows the photodiode to convert light energy to a corresponding voltage level. The non-inverting input of the op-amp is fed with half the supply voltage through the resistors R3 and R4 that has equal values. After the op-amp stage, the after-burner transistor, BD240, supplies high current pulses through the IR LEDs (D2 and D3). To limit the pulse currents, a fixed resistor is connected in series with P1; this prevents the pulse current to exceed 100mA. The diode D1 is an ordinary LED, which gives a flash if an infrared signal is sent to the receiver.


This project has a lot of potential for applications that are using infrared as a remote control system. Further improvements in the project will allow additional functionalities that will benefit the users who rely on remote area control.

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