NodeMCU Esp8266 analog input strange values

[antek]

Hello,

I am trying to build water pressure measure device with Esp8266 NodeMCU, Water Pressure Measure Sensor and in ESPeasy i reads ambigous values. I have find some articles discribing how ADC works on this NodeMCU but it still doesn't explain it fully this problem.

I describe here my build
The esp8266 is sourced by 5 V power source so on VCC pin there is 5V for sensor.
I have connected 5V sensor signal through the 1/5 analog divider to the Esp8266 A0 pin. Sensor is sourced from Esp VCC as i mentioned above. On Esp is ESPmega with VCC installed. So signal voltage of sensor is between 0V-1V but on ESPeasy analog internal device there is value from 2860 for 0V and 3065 for 0,86V on A0 and 3,3V for 1V A0

And question is... Is it normal? I cant relate it to the measures from the analog internal device explaination article where is the similar example of use with water pressure measure. I never gets the measured value like 0V just some strange 2860

[TD-er]

VCC builds are NOT what you need, as those have wired the Vcc that power the ESP8266 to the ADC.
Since that can only be done before even starting the sketch, there is a separate build for it.

So better use a build without "VCC" in the name for ESP8266 if you need to measure via the A0 pin.

[bidrohini]

Hello,

I am trying to build water pressure measure device with Esp8266 NodeMCU, Water Pressure Measure Sensor and in ESPeasy i reads ambigous values. I have find some articles discribing how ADC works on this NodeMCU but it still doesn't explain it fully this problem.

I describe here my build
The esp8266 is sourced by 5 V power source so on VCC pin there is 5V for sensor.
I have connected 5V sensor signal through the 1/5 analog divider to the Esp8266 A0 pin. Sensor is sourced from Esp VCC as i mentioned above. On Esp is ESPmega with VCC installed. So signal voltage of sensor is between 0V-1V but on ESPeasy analog internal device there is value from 2860 for 0V and 3065 for 0,86V on A0 and 3,3V for 1V A0

And question is... Is it normal? I cant relate it to the measures from the analog internal device explaination article where is the similar example of use with water pressure measure. I never gets the measured value like 0V just some strange 2860

Do you see the same problem if you use the Arduino IDE to read the values?

[Ath]

Do you see the same problem if you use the Arduino IDE to read the values?

A complete and resolving answer has already been given, please don't post useless and(/or) redundant replies.

[chromo23]

so on VCC pin there is 5V for sensor

I don´t know which sensor you are using but you should probably but a resistor in series with the sensor output.

This is can be a very helpful guide: https://www.letscontrolit.com/wiki/inde ... ure_sensor

Edit: Not sure if this is in the "new" documentation as well...

[TD-er]

He already mentioned a 1/5 ratio, so I assume he's trying to get 0...5V range into 0...1V range.
Nearly all NodeMCU boards I have seen, have already resistors present to map 0... 3.6V into 0 ... 1V for the A0 pin.
So adding the 1/5 ratio to it, I think it will be enough.

N.B. the resistors present on the NodeMCU typically are 100k + 270k, with the 100k over A0 and GND.

I think the biggest issue here is (as I already mentioned) to NOT use a "VCC" build when trying to measure an external analog signal.