The 12 v for max232cpe power supply by 7805, four 105 capacitance,
PC serial port expansion card, pci DB9 answered 2, 3, 5 feet connected to 12 v
Situation A: PCB to electricity, 232 chip is hot hot, can't communication, 232 foot VCC voltage changed repeatedly between the three, four, five V
B: PCB to electricity, 232 temperature has been normal, 232 foot VCC voltage stability in 5 V, command, but as long as the data from a computer 232 hot hot, can't communication, 232 foot VCC voltage changed repeatedly between the three, four, five V
Situation C: PCB to electricity, 232 temperature has been normal, data from a computer command, 232 works and has been normal work
Replace pci serial CARDS, 7805232 chips, but the question remains, and found no rule
Online to solve, thank you
CodePudding user response:
According to problem description, a problem when 232 VCC voltage fluctuation is very big, change between 3-5 v, problems estimate on the power supply in 7805, estimates the total current is too large, your PCB 7805 cannot normal power supply, 232 circuit is very simple and clear, as long as the line do not wrong will not what moth, under the board by the multimeter to total current, to solve the problem of power supply first,I wish you good luck