IR transmit and receive circuits
| IR: Infrared IR transmit/receive is usually used for applications such as remote control and light barrier. Infrared light is the wavelength located between the visible wavelength area and microwave wavelength area . (i.e inviable) There are some kinds of diodes and transistors which emmit and collect the infrared light. For example : QED 234 Light emitting diode and QSE973 Photodiode. The transmit circuit consists from a power source, PWM generator and light emmiting diode. The PWM generator is required because of 3 reasons: 1. Saving energy 2. Enabling a frequency to be detected by the receiver 3. The diode is supplied with more current then the manufacturer recommends for continuous forward current in order to increase the distance of transmitting, so in order not to burn it we turn it on and off allowing it to receive only peak forward current. The LM555 PWM generator is connected in an a-stable configuration generating pulses in a frequency of about 2KHz and a duty cycle of about 66% f=1.44/((R1+2R2)*C1)=2.1k D.C = R2/(R1+2R2)=0.66 R3=68 --> iIR=120mA The receive circuit block diagram is: And the circuit is: For operational amplifier it is better to use LM324 insted of LM741 because of the voltages used in the circuit C3 and R3 are the High pass filter used for filtering electricity signals from devices in the room. LM324A, R6 and R7 are the amplifier increasing the detected signal LM324B and R8 are the first equator R9 and C4 enhance the signal LM324C and R10 are the second equator which lights a led if it detect transmission. Back to basic electronic circuits for robotics page |
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