Our assignment is to design an analog parking lot access system. A laser pointer will represent the car, and an ID detector will check if the laser's duty cycle is 20%. I designed the circuit that will give the laser an input voltage in the square waveform with a duty cycle of 20%, and I was planning to design a detector that will detect the average energy of the laser, but since the laser will be a vehicle (which means it will be moving) the light energy that it will send to the detector will change with time, so the detector MUST check its duty cycle, not the average energy.
This is the circuit that will generate a square wave with a duty cycle of 20%
The components we are allowed to use are: +/-25 V output of DC power supply, any types of resistors, capacitors, inductors, diodes, LEDs, LDRs, op-amps, transistors
So, any ideas on how to make a circuit that will be activated with an input that has a duty cycle of 20%?
Just wanted to let you know, thanks to your answers I managed to design something that works perfectly!
The LDR detects the laser and causes the first Op-Amp into positive saturation with the same duty cycle as the incoming laser, then it's low-pass filtered (thanks to @transistor and @helloworld922) and since the duty cycle I'm looking for is 20% I compared this value to see if it's lower than 3 Volts and greater than 2 Volts, and then summed the outputs of the comparators to see if both comparators are in positive saturation. I think this one should do quite well.