Do-it-yourself projects and technology updates

Communicate with laser via serial port

Matthew, from superpositioned.com, and I have been discussing in DIY Live Forums the possibility of of sending video signals over a laser. A laser is capable of transmitting terabits per second. Of course this is limited to gigabits because of the lack of response in sensing circuits. Regardless, we discussed that if you could multiplex a DVI signal together, you could send it via a laser to your home projector.

Matthew did some more research and found a link to a site that sent information from a serial port over a laser. As he mentioned, serial ports are hard to come by these days. I actually had to pull out my old desktop because I needed a serial port for a microcontroller production board that was given to me.

From the tutorial:

“The transceiver is based on the MAX232A IC for generating and receiving RS-232 compatible voltage signals. The receiving sensor is an NPN infrared photo-transistor (OP505A). I chose an infrared photo-transistor to minimise ambient light interference. Although the laser wavelength is in the visible spectrum (~670nm) the photo-transistor�s broad response band (550nm to 1050nm) is wide enough to sense the intense laser beam. The signal from the photo-transistor is buffered via a pair of Schmitt trigger buffers to clean up and square the signal. The output of the second buffer is then directly converted to a RS-232 standard signal via the MAX232A.

The MAX232A generates +10V and -10V voltage swings using a dual charge-pump voltage converter from a single +5VDC rail (see RS-232 standards below). Several different versions of the MAX232 chip exist. The A version requires only 0.1 uF capacitors for the charge-pump and inverter, whereas the MAX232 requires 1uF capacitors. The advantage of the A version is that it has faster response times, and allows for faster data rates. ”

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This entry was posted on Wednesday, February 15th, 2006 at 9:55 am and is filed under Uncategorized. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.