Using Arduino in car environment

Projects Programming
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EDIT: I posted this in a wrong forum. Moderator, please move or delete. My apology.

My project is to turn an engine cooling fan on/off based on 5 or 6 temperature probes (DS18B20). The sensors will be connected to a project box. All will be located in the engine compartment, and an Arduino Nano will be inside the cabin. I have several electrical questions.

  1. Since DS18B20 has digital output, will I be okay without diligently shielding/grounding the sensor leads and the box?
  2. Is Arduino ground pin floating or tied to battery ground? There are 2 ground pins in Nano, one on the digital side, the other on the analog side. Are they same?
  3. I am going to use a car charger for USB 5V power supply. Is car charger ground same as battery ground?

I am no electrical person. Will I be okay without knowing which ground is floating from or tied to which ground? Any advice will be much appreciated.

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paker:
Will I be okay without knowing how which ground is floating from or tied to which ground?

You have to at least consider that for the cooling fan. If it's part of the car, one terminal is usually grounded to the car chassis. Really, you have to deliberately isolate a circuit such as with opto isolators, or else you don't have the option of floating the ground because the connections of the controller to any part of the car's electrical circuit is similarly referenced to chassis ground. Also, to float ground, the power supplies must be isolated as well (such as with transformers).