Reply To: [MAXI Automation] Analog IN and internal 5V supply deviation

[Friedl_AP]

Dear Jarda!

I’ve now tried the following:

1. Switched ADC to external reference as first command of setup()
2. After loading the code I switched on a lab supply (4.500 V) connected to GND/VREF on X2
3. AI12 is driven by another lab supply with 4.500 V (GND=screw terminal of Controllino, measured versus GND of Controllino)
4. ADC value: 602 (expected (1024/2-1)=511)
5. reduce VREF till ADC value gives 1023
6. VREF measured: 2.653 V (expected 4.500V/2 = 2.25V)

The internal reference is off and connecting an external reference does not really work either.

Code:

#include <Controllino.h>

/*
 * CONTROLLINO MAXI AUTOMATION - using analog VREF input
 * 
 * Reads out converted analog values from a screw terminal input AI12
 * of CONTROLLINO using VREF on X2 as reference.
 *                               
 *                             ------------------------
 * 24V ---------o--------------| 24V                  |  
 * external     |              |                      |  
 * supply       |              |                      |        
 *       --------------        |   CONTROLLINO MAXI   |        
 *       | Lab Supply |--------| AI12                 |        ---------------
 *       |   4.500V   |        |              X2-VREF |--------| Lab Supply  |        
 *       --------------        |                      |        |  4.500V     |               
 *              |              |                      |        ---------------
 *              |              |                      |               |
 * GND ---------o--------------| GND           X2-GND |---------------o
 *                             ------------------------
 * remark: AI12 = internal divider 2:1
 * ATTENTION: Only switch on the lab supply on VREF after you've downloaded the code the first time!
*/

void setup() {
  analogReference(EXTERNAL);
  pinMode(CONTROLLINO_AI12, INPUT);
  Serial.begin(115200);
  delay(300);
}

void loop() {
  int val = analogRead(CONTROLLINO_AI12);
  Serial.print(F("raw value: ")); Serial.println(val);
  delay(100);
}

• This reply was modified 3 years, 1 month ago by  Friedl_AP. Reason: stray DIV tags removed