visible optical link for RS-232C

Posted on Oct 17, 2012

The design in Figure 1 is a visible optical link for those who need to see the transmitted data. An isolation figure of more than 5000V is a bonus. Tests of the system used the COM input of a data-acquisition system, as well as a standard PC`s COM port. The MC1489 converts the RS-232C data to TTL signals. A 7404 gate then inverts the signal. The output of the 7404 drives Q1, a 2N3055 power transistor.

The transistor drives the set of three LEDs to form a light source. When no data exists on the RS-232C port, the LEDs remain off. When data transmission takes place, the LEDs glow at the rate of the data transmission. Keep the optical receiver 50 cm away

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