Circuit design of a common household appliance control module

The common household appliance control module circuit design introduced here is designed to control the power on and off of different appliances through telephone remote control. There are a total of 5 electrical appliances that can be controlled. The specific circuit design principles and circuit diagrams are analyzed below.

Circuit working principle: The purpose of this system is to control the power on and off of different electrical appliances through telephone remote control. There are a total of 5 electrical appliances that can be controlled. The signals that control the action of the controlled object are output from a total of 5 channels P1.3~P1.7. For example, if P1.3=1, T1 can be turned on and the relay J1 will be closed; if P1.3=0, J1 will be released. . If P1.7=1, T5 can be turned on and relay J5 is closed; if P1.7=0, J5 can be released. But as can be seen from the picture, P1.3 is not directly connected to T1. P1.7 is not directly connected to T5, but is separated by an integrated block 74LS273. 74LS273 is an 8D latch, that is, it contains 8 D flip-flops inside the chip. The input terminals are D0~D7, and the output terminals are Q0~ Q7. If the clearing terminal CLR adds a low level, the device will reset to zero, and the Q0~Q7 outputs will all be zero. If the clearing terminal is a high level, then whenever the triggering terminal CLK has a level rising transition, the input terminal The status of D0~D7 will be latched into the device and output from Q0~Q7. As long as the CLK terminal is no longer triggered, this status will be remembered forever. It can be seen that the signal output by AT89C2051 from P1.3-P1.7 is only stored first and then sent out. Its control logic is the same as that directly received. The necessary condition for the input terminal to be able to accept the input signal is that there is a positive transition on the terminal, which must meet two conditions at the same time: one is that the terminal of the decoder must be high level, that is, there is signaling sent to the remote control sending terminal; the other The second is that you must send a by. A transition signal from 0 to 1. Only when these two conditions are met at the same time, the AND gate outputs a positive transition signal and can accept external information. This greatly improves the anti-interference ability of the circuit and prevents malfunction of the controlled object that may be caused by unexpected interference.