Hey,
I'm using infrared sensors instead of RF for cost issues but I am a bit confused about the whole concept.The idea is to tag vehicles with d infrared transmitter and place the receiver at the gate.The receiver is further interfaced with a micro controller.What i wanna know is whether i can get unique tags by just using IR RX-TX of different frequencies?Say 38Khz (TSOP1738) for small and 40Khz(TSOP1740) for heavy vehicles?Can the 38khz receiver accept 40Khz by mistake?How do i produce these two different frequencies(for IR transmitter) with 555?Can i get a range of about 2 feet?Thanks

 

You can get a range similar to your TV remote control.

No you can't normally use different IR modulation frequencies, as the 3pin IR sensors have internal "brains" that require a particular modulation frequency.

What you need to do is the same as your TV remote, ie; modulate the 39kHz signal on/off in a pattern, and use a different pattern for each device.