A
Andrew
- Jan 1, 1970
- 0
Hi all
I've been trying to design an infrared receiver, but have several grey
areas. My transmitter signal is a simple 10us pulse with a period of
2ms (500Hz)- it's just a remote 'on' switch. The system needs to work
in bright ambient conditions over at least 40m from a mobile hand-held
Tx.
No off-the-shelf products are available becuase they all have a BPF
tuned to, say, 36KHz. (Plessey SL486 used to do this exact job). The
output will connect to a microcontroller so the software can detect
the signal.
Using my limited knowledge I've come up with a circuit where the
signal is processed as follows:
1) A photodiode connected to a wideband transimpedance amplifier (this
works well)
2) A voltage controlled gain amplifier (AD602 or similar)
3) A Peak Detect that is connected to the VCG amp to detect the peak
voltage of the incoming signal and adjust the amp's gain to avoid
saturation if the Tx is too close. And increase it if it's far away.
4) A comparator to output to TTL
5) A pulse stretch (555) to interface with microcontroller
Am I barking up the right tree?
I'd love to know what it is I really need in this circuit. Do I need
an AGC to stop my amp saturating? Do you think I should include
filters into my design? Is a peak detector the best way of controlling
the gain of the amp in this case?
Any help at all that anybody can offer will be very much appreciated.
Andrew
I've been trying to design an infrared receiver, but have several grey
areas. My transmitter signal is a simple 10us pulse with a period of
2ms (500Hz)- it's just a remote 'on' switch. The system needs to work
in bright ambient conditions over at least 40m from a mobile hand-held
Tx.
No off-the-shelf products are available becuase they all have a BPF
tuned to, say, 36KHz. (Plessey SL486 used to do this exact job). The
output will connect to a microcontroller so the software can detect
the signal.
Using my limited knowledge I've come up with a circuit where the
signal is processed as follows:
1) A photodiode connected to a wideband transimpedance amplifier (this
works well)
2) A voltage controlled gain amplifier (AD602 or similar)
3) A Peak Detect that is connected to the VCG amp to detect the peak
voltage of the incoming signal and adjust the amp's gain to avoid
saturation if the Tx is too close. And increase it if it's far away.
4) A comparator to output to TTL
5) A pulse stretch (555) to interface with microcontroller
Am I barking up the right tree?
I'd love to know what it is I really need in this circuit. Do I need
an AGC to stop my amp saturating? Do you think I should include
filters into my design? Is a peak detector the best way of controlling
the gain of the amp in this case?
Any help at all that anybody can offer will be very much appreciated.
Andrew