ADC Issues while measuring battery voltage

Projects General Guidance
1

Hello all,
A simple voltage divider circuit used to reduce the voltage down a series of 4 batteries.
Check attached drawing to know the circuit.
Details:
The 1R or load resistor I'm using in the circuit is 18k and the other resistors I'm using there are also 18k.
Another difference is that I grounded the ADC pins with 20k to eliminate any floating pin issue.

When the first pin is connected the ADC reads 1023 even though the voltage is only 4.182 and the second one reads 697. 697 may be an in-accurate but it shows that some sensing is involved at the least.
Any clues as to why it shoots up to 1023? Should I change the resistor value to get a more stronger signal at the ADC?

Device used to power the Arduino: Buck Regulator
I'm using this to avoid loading just a single battery and rather load the entire series of cells which total to around 16V

I know I'm going fundamentally wrong somewhere, just can't figure out where

Also the code is the simple example one from the IDE:

void setup() {
  Serial.begin(9600);
}

void loop() {
  int sensorValue = analogRead(A0);
  Serial.println(sensorValue, DEC);
}

Voltage Divider.jpg
Voltage Divider.jpg960×720 35 KB

2

It would have been wise if you had continued this in your previous post.
http://forum.arduino.cc/index.php?topic=399473.0
I pointed out to 123Splat (who made this diagram) in post#30 that the resistor connected to E1 should be between E1 and A0, not to ground. The diagram you posted now could damage pin A0.
The battery (LiPo?) will phantom-power the Arduino through the pin if you turn the Arduino off.

I would ask a moderator to merge these threads.

vikramnayak:
....I'm using there are also 18k.
Another difference is that I grounded the ADC pins with 20k to eliminate any floating pin issue.

Higher resistor values than 10k could give A/D inaccuracy, unless you add 100n caps from the A/D pins to ground.

Do you mean the unused pins. Not needed.

A sensor value of 1023 means that there is a voltage on the A/D pin that is equal or higher than the Aref voltage(5volt?). Could be that the ground connection is missing, or you have already damaged that pin.
Post a picture of the setup.
Leo..

3

Well the pin is not damaged for sure, since when I leave the pin open it floats random values and when I ground it with 20k, it's going to zero. I checked via multimeter, the first cell reads 1023 even though on the DMM it says 4.13V . Also, the first resistor on E1 I have not connected since I don't require a voltage divider at for the first cell, it being well below 5V at all times

Here's the simple circuit

(-ve)------([-] Li-ion battery [-])------> A0

a0 reads 1023

DMM says 4.13V atm.

Also checked with A1, A2. Same results

4

Forum software makes it difficult to merge topics across sections, so I'm just going to lock this thread, and direct people here.

I'm getting seriously pissed-off with cross-posting.