How to stop a battery power at a defined voltage

Using Arduino Programming Questions
1

Hi everyone,

I have a circuit with an arduino UNO, a sound sensor and a sd reader, and I power it with two linked 3,7 V LiPo batteries.

The project is a voice recorder.

What i'm looking for is a way to save the wave file that has been recorded before the circuit has passed a defined voltage, and then to cut the circuit and making the UNO fall asleep.

Two important things would be done with this:
1rst: the wave file will be recorded
2nd: The LiPo will not excessively discharge

I'm currently not sure about what to code to make this happen, and i don't want to do something dumb so i prefer to ask for help!

Thanks by advance.

2

You could use a Voltage Detector such as MCP-100 / 101 or one from the Seiko S-808 family to trigger a flag you would catch in your loop (or ISR) when battery is getting low

3

Hi J-M-L, thanks! But jsut in case do you know if there is away to do it only with coding? I didn't find the right library dedicated to this but maybe you do?

Also, the two individual Lipo batteries needs to be unpluged before reaching 3,2 v two keep them safe. Do the threshold be defined at 6,4 V, or can it go below?

4

you could read this and work your way with INTERNAL1V1 AREF or that one if you want something easier to read :slight_smile:

5

Hi J-M-L, i found a simple way to calculate the voltage: Analogread! (with a voltage divider)
But i don't really know how to insert it into my current code. Could you help me?

Here is the code :

#include <SD.h>
#include <SPI.h>
#include <TMRpcm.h>
#define SD_ChipSelectPin 10
TMRpcm audio;
int audiofile = 0;
unsigned long i = 0;
bool recmode = 0;

void setup() {
  pinMode(A0, INPUT);
  pinMode(A1, INPUT);
  pinMode(6, OUTPUT);
  pinMode(2, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(2), button, LOW);
  SD.begin(SD_ChipSelectPin);
  audio.CSPin = SD_ChipSelectPin;


}

void loop() {
}

void button() {
  
 
  while (i < 300000) {
    i++;
  }
  i = 0;
  if (recmode == 0) {
    recmode = 1;
    audiofile++;
    digitalWrite(6, HIGH);
    switch (audiofile) {
      case 1: audio.startRecording("1.wav", 16000, A0);break;
      case 2: audio.startRecording("2.wav", 16000, A0); break;
      case 3: audio.startRecording("3.wav", 16000, A0); break;
      case 4: audio.startRecording("4.wav", 16000, A0); break;
      case 5: audio.startRecording("5.wav", 16000, A0); break;
      case 6: audio.startRecording("6.wav", 16000, A0); break;
      case 7: audio.startRecording("7.wav", 16000, A0); break;
      case 8: audio.startRecording("8.wav", 16000, A0); break;
      case 9: audio.startRecording("9.wav", 16000, A0); break;
      case 10: audio.startRecording("10.wav", 16000, A0); break;
    }
  }
  else {
    recmode = 0;
    digitalWrite(6, LOW);
    switch (audiofile) {
      case 1: audio.stopRecording("1.wav"); 
      break;
      case 2: audio.stopRecording("2.wav"); break;
      case 3: audio.stopRecording("3.wav"); break;
      case 4: audio.stopRecording("4.wav"); break;
      case 5: audio.stopRecording("5.wav"); break;
      case 6: audio.stopRecording("6.wav"); break;
      case 7: audio.stopRecording("7.wav"); break;
      case 8: audio.stopRecording("8.wav"); break;
      case 9: audio.stopRecording("9.wav"); break;
      case 10: audio.stopRecording("10.wav"); break;
    }
  }
}

The analog entry of the voltage is A1
I want the controller to save the wave file when the sensor value is 640 (3,2v)
Could you help me?

6

Can you write a small program using analogRead to monitor that pin?

What’s that “crap” about ?

while (i < 300000) {
    i++;
  }
  i = 0;