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Simple PC Serial Port Buffer Using transistor

2015-01-09 23:58  
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This is a circuit diagram of a simple serial port buffer circuit.? A simple buffer circuit that adds the ability to drive to a PC serial port for the signal to go successfully from PC computer to the terminal server (other direction had no problems). Computer is connected to the connector CON1 and the buffered output is available ar CON2. With this circuit speed RS232 connection to the server could termial successfully raised for 9600 bps to 38,400 bps. The circuit is basically a two consistong buffer transistors Q1 and Q2 transistors that can be pushed up to 1A current pulse, but the current maximum putput circuit is limited by R2. R2 values are chosen to test the experimental values in the range of 22 ohm resistors from 270 ohm to 140 ohm value and the best results (it provides good impedance matching to the cable used). This is a good idea to use at least 1W resistor R2 replaced to ensure that it is not too hot in output short circuit situation (RS232 device must be held that to meet the standards). The following is a schematic drawing:

Simple PC Serial Port Buffer Using transistor1 Simple PC Serial Port Buffer Using transistor

This circuit is designed to be a compact box that is activated by D25 connector as a series of commercial RS232 buffer. The idea is to feed power to the buffer unit through a serial port voltage test pins 9 and 10. Power is taken from an external power supply (cheap universal wall transformer) and the cable to the D25 connector by modifying the cable between the computer and connected to the buffer circuit. The circuit in this configuration the maximum continuous current requires approximately 100 mA.

source: radiolocman.com

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