Collect a minimum voltage of pulsating DC ? Help

Other Hardware Sensors
1

Hi, I want to measure a pulsating DC voltage. The voltage pulsates slowly and constantly varies its level and speed. for calibration I would like to capture the Mninimum tips. Can anyone offer some help? I´d like only detect these minimum peaks constantly.
Note: The voltage is read by A0 (Mega2560)
Thanks in advance....

2

I´d like only detect these minimum peaks constantly.

That's a little baffling. What information are you expecting to collect? i.e. in your example waveform, what would be the output from the arduino?

3

Would this work?

UIR = analogRead(A0);
if (UIR < lowestUIR) { lowestUIR = UIR;}
4

I will have to try. But how do I save my measurements and it detected my minimum voltage and compare it with the lowest UIR?

5

Thanks for this tip!

here my new code. But it doesnt work. DAC only incements up, when the voltage is to low. But the DAC doesnt decrment , if lowest voltage ist higher my level.

#include <AH_MCP4922.h>
#include <MsTimer2.h>

int IR= 0;
int j=0;
int i =10;
int UIR = 0;
int lowest_UIR=11; // min Level UIR
int UR = 0;
int lowest_UR=11; // min Level UR

AH_MCP4922 AnalogOutput1(51,52,53,LOW,HIGH); //define AnalogOutput1 for MEGA_board, select DAC_A, Gain=1x
AH_MCP4922 AnalogOutput2(51,52,53,HIGH,LOW);
volatile byte counter = 0;

void setup()
{
pinMode(A0,INPUT);
pinMode(A1,INPUT);
AnalogOutput1.setValue(i);
AnalogOutput2.setValue(j);
initTimer2();

}

void loop()
{
}
ISR(TIMER2_COMPA_vect) { // ISR for read every 10 ms
counter = (counter + 1) % 2;
switch(counter) {

case 0:
UR = analogRead(A1); // read A1 make DAC high if UR smaller 11
if( UR <=11){
j++;
}
AnalogOutput2.setValue(j);
UR = analogRead(A1); // read A1 , make DAC loower if UR_lowest voltage ist higher Level 11
if (UR < lowest_UR) {
lowest_UR = UR;
}
if (lowest_UR>11){
j--;
}
AnalogOutput2.setValue(j);

break;

case 1:
UIR = analogRead(A0); // read A0 make DAC high if UIR smaller 11
if ( UIR <=10){
i++;
}
AnalogOutput1.setValue(i);

UIR = analogRead(A0); // read A0 , make DAC loower if UIR_lowest voltage ist higher Level 11
if (UIR < lowest_UIR) {
lowest_UIR = UIR;
}
if (lowest_UIR>11){
i--;
}
AnalogOutput1.setValue(i);

}

}
void initTimer2()
{
// Timer 2 CTC mode, prescaler 1024
TCCR2B = (1<<CS22) | (1<<CS21)| (1<<CS20);
TCCR2A = (1<<WGM21);
OCR2A = 155;
// enable Timer 2 interrupts
TIMSK2 = (1<<OCIE2A);
}