Students are required to design a circuit where the output is isolated from the input by an opto-coupler that is constructed from discrete components (to be supplied), i.e. an infrared light emitting diode (LED) and a phototransistor
The input signal to the circuit is specified as 2 + A sin(2π f t) Volts where 20Hz< f < 20kHz and 1 < A < 4 Volts. Note that this will be the signal that is applied to test the operation of the circuit during the project demonstration.
The design specifications are:
1. The output signal is to be 2A sin(2π f t + θ) where f is the frequency and A is the amplitude of the input signal applied to the circuit.
2. The phase shift, θ, with respect to the input signal, must be as small as possible.
3. The circuit will detect when the specified input signal is applied and indicate this by switching on a green LED.
4. The circuit is to switch on a red LED when the frequency, f , of the output (or input) signal is between 970Hz and 1.03 kHz. 5. The circuit is required to minimise the effects of nonlinearities, due to the ‘optocoupler’, as observed in the output signal.
Each group of students will be provided with,
• an infrared LED,
• a phototransistor,
• a breadboard,
• access to operational amplifiers and ancillary components (e.g. resistors, capacitors, diodes and LED’s),
• a model of the infrared LED and photo-diode for use in LTspice