Multiple Devices Switching Through PC Abstract: The MAX-232 of PCs is a versatile tool to develop many PC based applications. Controlling of switch on/off the gadgets is done by MAX-232 where the computer decides the sequence of switching. The circuit here uses eight devices through MAX-232 data lines.
The MAX232 is an integrated circuit to convert signals from an RS-232 serial port to signals suitable used in TTL compatible digital logic circuits. The MAX232 is a dual driver/receiver to convert the RX, TX, CTS and RTS signals.
The drivers give RS-232 voltage level outputs (approx. ± 7.5 V) from a single +5V supply by on-chip charge pumps and external capacitors useful for implementing RS-232 in devices. The receivers reduce RS-232 inputs to standard 5 V TTL levels and have a typical threshold of 1.3 V, and a typical hysteresis of 0.5 V.
The circuit is a zero-crossing optically-isolated triac driver MOC3041, triac BT136 and discrete components. Parallel-port from pins 2 to 9 connected to pin 1 of IC1 by IC8 via current limiting resistor R1 through R8, respectively. Pin2 of IC1 through IC8 is linked together and connected Pins 18 through 25 of the parallel port.
The MOC303XM and MOC304XM devices have aAlGaAs infrared emitting diode coupled to a monolithic silicon detector to perform the function of a zero voltage crossing bilateral triac driver. They are designed to use with a triac in the interface of logic systems to equipment powered from 115 VAC lines, like teletypewriters, CRTs, solid-state relays, industrial controls, printers, motors, solenoids and consumer appliances, etc.
Applications are Solenoid/valve controls, Lighting controls, Static power switches, AC motor drives, Temperature controls, E.M. contactors, AC motor starters, and Solid state relays.
This switching device provides the user to operate eight devices simultaneously by serial communication port of the pc. The implementation of micro-controller converts the data from parallel communication to serial communication.
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