LASER Voice Transceiver

[Ayne]

I am not expert,
But i use my tiny brain for making some thing.
Will this work???
OR
There is any mistake in it???
Some improvement???

And second,
I make this circuit in "ExpressSCH" now i want to make it's PCB in "ExpressPCB" but i don't know how can i open this circuit in "ExpressPCB"...
Plz guide in..

 

[audioguru]

The high current from the 555 will probably destroy the laser and the 555 without a current-limiting resistor.
Your photo-transistor is an emitter-follower without any gain. Use a collector resistor and ground the emitter to get some gain out of it.

 

[Ayne]

With some improvements

Thanks to "audioguru"

I made some changes, plz check it and guide me for more improvement.
And plz tell me the easiest way of making it's PCB from it's Schamatic???

 

[audioguru]

I made some changes

That's better, but you should add a resistor in series with VR1 to limit the laser's max current.

I notice that the laser is frequency modulated (FM) but your receiver doesn't have an FM demodulator so its output will be zero.

 

[Ayne]

Laser is Pulse width modulator
and in the receiver side "Butterworth Low Pass Filter" is a demodulator.

 

[Hero999]

To be pickey it's pulse position modulation and you can't easilly frequency modulate a laser. Only pulse frequency modulation is easilly possible. Frequency modulation requires a special type of laser and reciever and is at the cutting of technology at the moment.

 

[audioguru]

Sorry, I stand corrected. It does use pulse-position-modulation and its average level will be audio after the carrier is filtered out.
It will pickup AM interference like AC lamp buzz.

A laser or anything else that can pulse can have its carrier frequency modulated with FM. It is difficult to modulate the colour of a laser with direct FM modulation.

 

[Ayne]

I check this circuit in Circuit Maker and it is working,
But the problem is it's PCB.
I want to convert Circuit diagram to PCB but i don't know how.

 

[Hero999]

It will pickup AM interference like AC lamp buzz.

That can be minimised by filtering, a 50/60Hz filter might help but then you'll still have the harmonics. A comparator with some hysteresis might help but that will effect the sensitivity of the circuit. The best way to remove the interference is to use a higher frequency like 38/44kHz and a TV remote control IC for the reciever.

 

[Nigel Goodwin]

I check this circuit in Circuit Maker and it is working,
But the problem is it's PCB.
I want to convert Circuit diagram to PCB but i don't know how.

You sit down and design it! - although I would suggest you breadboard it first, rather than waste the time and effort making a PCB.

 

[audioguru]

The best way to remove the interference is to use a higher frequency like 38/44kHz and a TV remote control IC for the reciever.

TV remote receivers have a data stream, I don't think audio can be used.

Infrared language translation and wireless headphones and wireless speakers use FM.

 

[Ayne]

Output Wave forms

Below are the wave forms in circuit maker,
Now i am making it's PCB in PCB123.

 

[Ayne]

Another Problem,
PhotoTransistors are not available in our local market.
Only the PhotoResistors(LDRs) are available.
I want to replace PhotoTransistors with PhotoResistors... Plz guide me in this way
Thanks

 

[Dr.EM]

I'm quite confident it will not work with LDR/CDS cells (photo resistors). They are too slow. Order phototransistors online, catalogue shop, from eBay etc, they are generally common.

 

[Paul Obrien]

One other thing, it could probably use some additionalcapacitors for the power supply. To stop oscillations and help with power regulation.