Thank you so much for all your advise. I will try them. Maybe i can use zener diodes to replace LM7805. I appreciate your effort and time.
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thank you so much
Thank you so much for all your advise. I will try them. Maybe i can use zener diodes to replace LM7805. I appreciate your effort and time.
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Just use a resistor! The input pin is limited to vcc so a resistor works quite well and is very cheap and simple - if the output of your PLC is left floating you may have to tie it down with another resistor. I've used a resistor straight into a PIC from 240Vac for sensing the zero crossing to synchronize firing a TRIAC (I think I used some where in the region of 200k). It seems so wrong I know, but it really works well and is simple.
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Just make sure with yr resistor you don't exceed 20mA - try keep it down to 1-2mA
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