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uLCD32-PTu powered by Arduino VIN

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  • uLCD32-PTu powered by Arduino VIN

    my project is a simple setup:
    Arduino Nano
    2 temp sensors
    2channel relay switch
    1 uLCD32-PTu screen.

    My problem:

    I am attempting to use this setup in my car and while it all runs perfectly through the USB cable into a cigarette lighter converter, it will not operate when I put 12 volts to the VIN pin on the Nano.
    Naturally, seeing as how the Nano is designed for 5V input, that makes perfect sense. I added a 5 volt regulator in between the 12v coming from the car and the VIN pin and while the controller works great now, the 5 volt regulator gets very very hot while the controller is on.

    How should I be wiring up power so I am not overloading my regulator?

  • #2
    The Arduino Nano can be powered via the Mini-B USB connection, 6-20V unregulated external power supply (pin 30), or 5V regulated external power supply (pin 27). The power source is automatically selected to the highest voltage source.

    keep in mind the onboard regulator is linear and not a switching psu, therefore the more voltage it drops the more heat it will put out. using a REGULATED 5v on pin27 should bypass the regulator alltogether. if you put 5v on VIN, its understandable it got hot, after the diode circuit in the regulator there is 4.3V left for the nano, and its trying to suck more power than the powersource can apply. 12v will almost always heat it up too as it turns 7volts into heat dissipation, it's recommended to use 6-7volts on VIN or 5v direct on pin27, and dont forget to only run one power source (usb or ext power, not both)
    Last edited by tonton81; 4th March 2017, 10:20 AM.


    • #3
      Dear Gustermaximus,

      You can use a Switch Mode DC-DC converter like a buck converter to convert the 12 V source to a regulated 5V because of their high efficiency. You can use an IC like the MC34063, uA78S40, Maxim ICs or National Simple Switchers to make one by checking their application notes or just buy a 12V to 5V buck converter module. A better alternative but more expensive is to buy an Isolated DC to DC 12V to 5 V converter since the failure mode of the Buck converter is nasty if the power switch is shorted. Attached is a schematic diagram for conditioning the power supply
      since there are some transient in the electrical system of a car.

      Best regards,
      Attached Files