You can use a photo transistor as a receiver and an LED. Modulate the LED at 40Khz and put a filter on photo transistor. (or you can buy a ready made receiver with filter like the kind used in TV for remote receiver)
we are limited to the specific parts such as there is a pair of IR emitter + IR phototransistor. .....what if we pass the signal from the receiver to the band pass filter designed to filter out 40KHz reflected signal? then we need an amplifier to amplify the filtered signal right?
Added after 44 seconds:
we are limited to the specific parts such as there is a pair of IR emitter + IR phototransistor. .....what if we pass the signal from the receiver to the band pass filter designed to filter out 40KHz reflected signal? then we need an amplifier to amplify the filtered signal right? i think this might take lot of time in calibration.
you will most likely need to amplify the signal. You can use a small op amp for this. Also you need some kind of optical filter in front of the receiver. You can make this from a piece of green and red perspex sandwiched together
You're building a reflective proximity sensor, right?
Modulation and filtering is done to reduce the effects of ambient IR. If your robot is going to operate indoors, you don't necessarily need to modulate and filter, because the intensity of the ambient IR might be sufficiently low.
HI
u can use IR sensor with no sensitivity to light except your transmitter.
it would be practical to use modulated IR transmitter by LM567.It's a Tone Decoder IC.this schematic will help u.
Basically a good idea. I found a similar circuit, that was working quite well, in a previous designs folder. As an interesting
difference, the LED control is derived from LM567 pin 6 (triangular wave) rather than pin 5 (square wave), which was necessary
to achieve optimal demodulator phase and maximum sensitivity.