Cross Talk in Node Mcu analog Pin

Using Arduino LEDs and Multiplexing
1

Hello Community,
I am using an array of sensor(15 sensor) interfaced with 16*1 Multiplexer (CD4067 MUX BOARD) with ADC pin of node MCU along with filter circuitry .
I am getting crosstalk meaning data from one channel is getting transferred to another channel even after switching.
How to remove crosstalk in this circuit ?

mux
mux1040×780 62.6 KB

2

are you aware that the ADC on an ESP8266 takes a voltage between 0 & 1 ?

Could it be that you should wait a small amount of time between switching and reading ? There is a capacitor (very small one but still) on the signal line.

3

Thanks for the fast response.

I am providing values between 0 to 1 volt , with reference voltage of 0.5 volt...when pressures sense it is 0.8 and pressure removed 0.3. volt....but still cross talk is there …analog pin is not able to clearly distinguish between the channel where the pressure is applied and the channel which pressure is not applied..

Can i know the process to solve the problem?

4

Yes, but not a NodeMCU (as in the picture).
A NodeMCU board has a built-in 220k:100k voltage divider, that changes the 0-1volt range of the ESP8266 into an analogue voltage range of 0-3.2volt.

15 piezos?
You might need an opamp buffer for each piezo (high impedance source),
and connect the muxer output directly to the NodeMCU.
What is your project.

Which opamp are you using. Is it fully rail2rail (in and out).
A split supply (negative voltages) could be dangerous to muxer or ESP.
Leo..

5

I am using 15 piezo sensors across MUX and at signal pin using charge amplifier circuit along with filter circuit which is passes to ADC pin of NODEMCU...

TL074 opamp is used as a charge amplifier.

6

I would buffer each piezo (15 x charge amp), so the muxer switches low impedance sources.
I would swap the CD4067 for a 74HC4067, which is a better match for your 3.3volt MCU.
I would use a single 3.3volt supply (from the NodeMCU) for muxer and op-amps.
And op-amps that can work on a single 3.3volt supply and are rail2rail in/out (the TL074 is not).
Leo..

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