Data transmition using lasers?

[Acetronics2]

Hi, Chris

one of our french Magazines, called Radio-Plans, had published such a project ...

yeah ... more than 25 Years ago ...

Magazine has disappeared at least 20 years ago ...

So ... U can do it !!!

Alain

[chrisshortys]

Awesome i was hoping it would be the case as the two run on very similar wavelengths!

Any suggestions on this one? I dont need to transmit much code probaly just the standard 2,# or somthing.

I had a look on the forum earlier but couldnt find any examples of IR circuits, is it possible to take the Tx and RX straight from the chip to zero volts or does it require extra components?

Cheers Chris

[Charles Linquis]

http://www.scribd.com/doc/6539201/Wi...aceFinal-Model

[ardhuru]

But why specifically laser, Chris?

Whats the range you're looking at?

IR LEDs can give you a pretty good range, especially if you use optics and are careful with the alignment (which you'd have to be with anyway, with lasers)

You could ramp up the IR by using multiple LEDs.

Regards,

Anand

[b1arrk5]

We sent Morse code using a laser pointer a few years ago. Shoot the laser beam through a running 'muffin' fan. This chops the beam into a frequency that will be in the audio range. The beam then travels through the air, and hits a Radio Shack solar cell. The output of the solar cell was run into a small audio amplifier. You can then hear the audio tone, the frequency of which is determined by the speed of rotation of the fan. Using a simple shutter to open and close, blocking the beam, allowed sending Morse code to the user. The laser pointer was set up on a tripod and a spotting scope was used to align the beam onto the target solar cell. We achieved a half mile range, and were going to try going from one mountain top to another, but my helper got a job out of town, so we never went any further with it.
A Google search of laser chopper beam will show you lots of other ideas.

Jerry

[chrisshortys]

Well the idea of the project is for a local paintball site. They are planning a MILSIM event in august and they wanted somthing to simulate a laser designator for their "airstrikes". So the idea was to use the laser as they can see where theyre pointing the thing and have a reciever at the other end which the laser must hit directly.
I decided against IR Tx as you dont get a idea of where your pointing the thing and its more of a general pasting of an area than a laser which will give you a smaller target.

Ive started playing with IR Tx and Rx to get started but im having troubles with the reciever, the transmit works and ive viewed this on an ossciloscope but i dont get alot out of the Rx. In the example above there is no amplification, is this needed before the chip?

But why specifically laser, Chris?

Whats the range you're looking at?

IR LEDs can give you a pretty good range, especially if you use optics and are careful with the alignment (which you'd have to be with anyway, with lasers)

You could ramp up the IR by using multiple LEDs.

Regards,

Anand

[Charles Linquis]

Any kind of data speed will require a phototransistor (or photodiode) and some kind of amplifier.

Check out Figure 7 of
http://www.physics.csbsju.edu/~awhit...otodevices.pdf

This circuit would have to be followed with an op-amp or (preferably) a comparator to convert the analog output to digital.

Also -
http://www.aptechnologies.co.uk/PDF/...20Circuits.pdf

[Jumper]

Hi,

Most cheap laser pointers are too slow to modulate but by using the idea of a mechanical beam chopper will take care of that.

Then you need an OP-amp or 2. Make sure they are AC coupled and have a decent amplifiation. After this you put a LM567 which is a tonedecoder that will give a logical signal if the tone is present.

They ar cheap, easy to use and detect small signals. If you can modulate teh laser and have a HWPM you can connect the - side of the laser to the HPWM pin and the + side of the laser to the USART tx pin or the opposite if you like to use inverted mode.

Then from the tone detector's logical pin straight in on your usart RX in the other end.

Or as mentioned before... use an already made audio amplifier and put the tone detector after it. That will work if you have a low enough baudrate becuse you need some carrier FQ cycles per bit to give the LM567 enough to work with.

/me