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I have an project which control a heat exchanger.

I read 4 temperature sensors DS18B20, a distance with HC-SR04 Ultrasonic Sensor, and a flow with YF-S201 (with attach interrupt). I can turn on and off a monophasic motor with Arduino too.

I have many interference problems with i turn on my motor, the readings of temperature fail with big frequence and i have many errors with interrupt counter.

I read many posts about interferences, and one most important factors are high impedance of floatings pins.

I use Arduino Due, then many pins are floating. I have to put a pull-down resistors in all pins?

My project looks like the architeture in the image link bellow: https://i.stack.imgur.com/glo5L.jpg

The code of my project can be found in : https://github.com/felipefonsecabh/ArduinoCode/blob/ArduinoNoNavigation/ArduinoCode.ino

Any opinion?

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    The motors are connected directly to the Arduino? Or do they contain their own driver circuitry...?
    – Majenko
    Nov 15, 2017 at 14:02
  • I used SSr (Solid State Relay) to turn on and turn off my motor. Nov 15, 2017 at 15:04
  • Why doesn't your diagram show the SSRs then? Nov 15, 2017 at 15:16
  • Don't use the weak internal pullup, use external pullup resistors. For example with 4k7 for the 1-Wire bus, the buttons, and perhaps the flow meter as well. Check your grounding thoroughly, and after that check it once more. Don't let the returning current of the motors reach the GND of the Arduino Due board. A LM35 is never accurate, unless your voltage is perfectly accurate and stable. I'm sorry to say, but the usage of millis is totally wrong. Rewrite that. Use the blink without delay example: arduino.cc/en/Tutorial/BlinkWithoutDelay The temp[0...3] is used for different things.
    – Jot
    Nov 15, 2017 at 18:19
  • I disagree about usage of millis ... i try to use the same way of this example (blinkwithout delay) ...what's wrong? Nov 16, 2017 at 13:38

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