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Optical 2 way radio

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Electricman2K5

New Member
I need to create a "through the air" optical
communications system to transmit speech. Like an optical walkie talkie for 10m range.

1) I want to simply do this without a microcontroller. Using a microphone a Analogue To digital converter and then a transmitter IR LED section. To decode at the other end I will use a Phototransistor to a DAC then a speaker.

I need a serial ADC/DAC device can anyone think of one which will be suitable also what other stuff will I need.

2) Also I was thinking of using a LM565 PLL chip and an FM system instead of the ADC/DAC method but it isnt sold anymore is the LM567 the same/equivalent???

Does anyone know which system is the best to choose 1 or 2?????

Any help would be appreciated!!!
 

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guzzimac

New Member
Use a CMOS PLL, can't remember the part no. but I did this years ago when building a fibre optic talk set and it worked a treat.

Rob.
 

pebe

Member
Simpler to use an FM system (2) than digitising it (1). You could use a 555 as an voltage-to-frequency convertor at the transmitter. At the receiver a phase locked loop or pulse counter as demodulator.
 

tansis

New Member
Here' a link to a rather poor Infra red headphone circuit,
will keep an eye out for a better one.
 

Russlk

New Member
Trying D/A and A/D won't work, but PWM would be easy to impliment. Check out National Semiconductors's application notes: AN-74, figure 40 and AN-31 figure 31. You only have to filter the PWM at the receiver to recover the audio.
 

stevez

Active Member
You might look for amateur radio publications or journal articles on the subject. Some amateurs are using lasers for communications. I'd think that some have done a good job explaining their efforts.
 

panic mode

Well-Known Member
what is purpose for all of this? why it has to be optical?
is the room divided by some glass window?
is this is something like a radio station or maybe bank teller?
what kind of signal quality do you expect?
 

Electricman2K5

New Member
Optical system

its for audio speech like a walkie talkie intercom between 2 people for about 10m range -( 2 cyclists). The quality needs to be good enough to hold a conversation. It was chosen as an optical system just to try to use the technology available because radio systems are very popular.
 

audioguru

Well-Known Member
Most Helpful Member
So the IR communicator is for bicycles. Very impractical.
If you mount the IR transmitters and detectors on the front of your helmets, you would need to point them at each other (like your TV remote) and crash off the road!
I guess you could use an array of transmitters and detectors surrounding your helmets, like used for language translation in seminars, but you would need to carry around car batteries to power them. Well, maybe a bunch of AA cells might last for a while, certainly not 9V batteries.

Use efficient low-power RF like everyone else.
 
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