[quote author="arupbsk"]Do you have slow (I mean normal) speed video with sound?[/quote]
I'm afraid not as it is not actually a video, but in fact 1,743 photos stitched together into a video! They were taken at between 5 and 10 second intervals and dumped occasionally to my computer and the point of view changed. Also seeing as the timelapse is of ~8 hours, I think it might make for quite boring viewing at normal speed!
[quote author="asteadman"]Does it work well with Analog input signals? What is the functional Bandwidth?[/quote]
I have now updated the spec above, so should answer your questions. It supports analogue input signals but only up to +/-0.4V to work without the gate clamp diodes playing havoc! The bandwidth isn't great currently (~50-200Hz), but it was working a lot faster, about 100Hz-20KHz.
[quote author="arupbsk"]You've to post comments in some 10 random forum posts[/quote] This differs from what the rules state here, perhaps you are thinking of some other site?
An FM modulation, demodulation and transmission system using CMOS 4000 logic.
Functional Description: An input waveform enters the Voltage Controlled Oscillator (VCO), resulting in a FM modulated waveform. The VCO works by altering the voltage the capacitors charge to in a NOR astable circuit. The higher the input voltage, the shorter the charge time, therefore a higher frequency. The lower the voltage the longer it takes for the capacitor to charge therefore a slower frequency. The input signal cannot be very large otherwise the CMOS gate protection diodes will clip the signal. This FM signal is then sent to an IR LED (through a buffering MOSFET) and is received by a photo-transistor at the other end. The phototransistor is used in switch mode (see Fairchild App Note) so the output is nicer to work with (vaguely resembles a square wave). The output signal from a photo-transistor resistor network is then fed through a Schmitt trigger to clean the waveform further. The signal is then demodulated by using it to trigger a short-pulsed NAND monostable. This results in a charge build up on the end capacitor which is proportional to the trigger frequency, thus recovering the original waveform.
Schematics attached below.
Specs: Input: +/-0.4V wave of any form (currently up to 200Hz) Astable: Created using NOR gates (4001) Monostable: Created using NAND gates (4011) IR LED Current: ~60mA (max transmission distance is a few centimeters currently but could increase current for larger range) Power Rail: 5V DC (from USB port) Bandwidth: Using current astable and monostable frequencies, 50-200Hz
The maximum frequency of the circuit was much higher but due to the unstable nature of the NOR oscillator it stopped working and had to be reduced to the current 200Hz. It used to operate at up to 20KHz.
If the circuit is modified to modulate higher frequencies again, the astable and monostable frequencies have to be increased and the output RC filter also has to be adjusted. If it were to work at the 20KHz mark again, it could be used for MP3 player audio transmission.
Equipment Used: Gwinstek GFG-8020H Analog function generator Amprobe 34XR-A Industrial DMM 2 PicoScope 4MHz digital oscilloscopes Nikon D3100 for timelapse and project photos 2 Laptops for Picoscopes and research!
