RS-232 Laser Transciever circuit

Posted on Sep 23, 2012

Laser based projects used to be expensive, until the development of solid state lasers. This project is designed for the entry level laser experimenter. The circuit allows any two computers with serial (RS-232) communication capability to communicate over 200 meters using a laser beam. A low cost transmitter only circuit is also presented here for use in one way communication and other laser based projects. If you are like me and always wanted to buy a laser pointer to play with, but could never find practical uses for one, here are a couple of circuits to convince you to finally make that purchase. Before we begin, however, it is necessary to give a word of warning: Never look directly into the laser beam as eye damage may occur.

RS-232 Laser Transciever circuit
Click here to download the full size of the above Circuit.

I will present the project in 2 sections: the first is a full-duplex transceiver, and the second is a transmitter only. The main reason for separating the design is to offer a cheaper solution if only half-duplex communication is required. For full-duplex communication 2 transceivers and 2 lasers will be required, and for half-duplex communication a single laser, a transmitter and a transceiver is needed. The transmitter can be also used as a stand-alone circuit if you only want to control the laser in other laser experiments. This view shows the assembled transceiver. In this photograph you can see the conductive dummy battery used to reach the negative contact inside the case of the laser. The laser source for this project is an inexpensive laser pointer pen. As well as being readily available, the circuit is designed in such a way so that the laser pointer is not damaged, and can be used for other experiments. Because this is an entry level circuit, costs have been kept to a minimum around $20 for the transceiver and approximately $10 for the transmitter (excluding the laser pointer). Why use a laser? A laser as a communications medium has some unique properties compared to other forms of media. A line-of-sight laser beam is useful where wires cannot be physically connected to a remote location. A laser beam, unlike wires, also does not require special shielding over longer distances. Lasers offer at least an order...

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