BUFFER, DRIVER & SWITCHING MODULE


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When the user programs the schedule for the automation using GUI [Graphical User Interface] software, it actually sends 5-bit control signals to the circuit. The present circuit provides interfacing with the Microcontroller and the controlling circuitry. This circuit takes the 5-bit control signal, isolates the MICROCONTROLLER from this circuitry, boosts control signals for required level and finally fed to the driver section to actuate relay. These five relays in turn sends RC5 coded commands with respect to their relay position.

Circuit Description:

The Hex Buffer/Inverter IC1’s working voltage of +5V is applied at pin-1 and five control signals are applied at input pins 3, 5, 7, 9 & 11. Thus the signal supplying circuit [i.e. MICROCONTROLLER] is isolated from this Buffer & Driver circuit. Further the grounding resistors R1 to R5 prevents the abnormal voltage levels passing inside the IC1. The buffered outputs are acquired at pins 2, 4, 6, 10, & 12. Thus the varying input is further stabilized and fed to signal diodes [D1 to D5]. As the load is inductive, there is a chance of producing back e.m.f. So to cope with this back e.m.f, signal diodes are used. But this signal level is not strong enough to drive the low impedance relay. So, IC2 Darlington driver is used. Its working voltage is +12 V and only five input/output pins are used. The output signal from the Darlington driver IC is strong enough to actuate five relays.