Any problems for my circuit design?

Need Help With My Project
1

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WhatsApp Image 2019-02-20 at 09.23.15.jpeg1600×1200 126 KB

Above is my circuit diagram to connect with NodeMCU ESP8266.
What I am doing is, various independent 24V signals will be converted into 3.3V zenor diode, then connect into different DI/O on the board.

For, D0, if status is HIGH, then value0 = bit(0), else 0
For, D1, if status is HIGH, then value1 = bit(1), else 0
…etc until D10

The program will combine all value automatically by a time interval (1),
VALUE = value 0 |= value 1 … |= value 10
and Email will be sent out with VALUE as content by a time interval (2).
The program has tested and success do what I want, However, the hardware problem occurs.
I used the BUTTON at Blynk, the board can sense the status of its pin HIGH or LOW
I used the 3.3v supply from the board and connect to different DI/O, the board can still sense the pins HIGH or LOW

BUT, when I used above circuit to connect my designed 3.3V signal, the board cannot sense,
(i.e. values are always zero)
My questions are:

  1. Why both the supply are 3.3V (from MCU board / my designed circuit), but the board only recognize the previous one, it just sample, just put a 3.3v signal into a pin.
  2. When the Resistor (Ra/Rb/Rc) is used 330 ohms, the resistor starts to burn and have burnt smell, but Vout measured on the board fulfill 3.3V, but if I used 1K ohms, the resistor will not burn and no smell, but Vout only supply 1.x V (sorry my meter cannot read decimal places)
    So, How to calculate the correct value for the resistors?
    Thank you
2

you can shift leveling the 24V signal down using voltage divider.
i suggest test the output voltage using multi-meter before connecting it to your MCU

here is calculation to roughly get it down to 3.3 V

image

or use such optocoupler isolator for better result more safely

image
image.jpg750×700 227 KB

3

Thank you your suggestion.
It seems it will be more stable but only cost some money than zenor diode, but it is acceptable!
Let me order some to test first.

4

BTW, I know that Blynk http restAPI can read the status of a specific pin,
in my case, how can i read the variable in my program and shown it on webpage?
Is it possible?
[e.g. Variable byte {VALUE} = 1010, inside my program now, can I just input a URL and the webpage show 1010?]