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Which is better Input 5 volts to arduino..??

e14 Contributor

Guys, I intend to use arduino 24*7. I'm using it in a small industrial bot. I don't want my arduino to draw a higher current than its capability and get damaged. In my application I use 5 digital pins of my arduino as input n rest as output. To make sure OUTPUT pins does not draw more current, I've conneted it to ULN 2803 which is having further connections. I'm okay in that. I want to ask, would it be better to give the input 5 volts to the INPUT pins in my code from the "5V pin of arduino" or "from my 5 Volt regulator IC 7805". My goal is to make sure arduino works for a long period of time..!!

 

Thanks in advance.. image

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  • 0 in reply to billabott

    Sorry Billabot, I was responding to Dabs and mistaken you alls names. apologies

     

    F/S

  • 0 in reply to fidelsalinas

    I agree with Fidel about supplying your own 5v into the 5v input, and the official site (www.arduino.cc find the products tab) says you should apply 7-12v to the Vin pin instead.

    But sorry Fidel & William I don't agree with the other responses.

    would it be better to give the input 5 volts to the INPUT pins in my code from the "5V pin of arduino" or "from my 5 Volt regulator IC 7805"

    I read this as asking if he should use the Arduino 5v to run through the switch/contact and then control the input pin.

     

    ( I may be wrong here, but until the OP replies ...)

     

    Your approach to ensuring long service life and eliminating damage is very good, and some others could learn from this.

    Your question is also a very good one.

     

    The 5v regulator on the genuine UNO boards (remember the open Source nature does NOT require a manufacturer to do anything) can easily cope with 1A, and an indefinite short circuit (according to a datasheet for the 5v regulator).

    The site specifys the 3v3 maximum current (50mA) but not the 5v, which is a shame.

     

    The general rule is 'never apply a voltage to a IC pin, that is greater than the supply voltage of the IC' (unless specifically designed for such), so if the supply is 4.9v then your input should never exceed 4.9v, no matter where it comes from.

     

    I would suggest you power it from the Arduino 5v, which may also avoid problems if the regulator dies, but the Arduino is still running.

     

    If your concern is that the 5v supply may get shorted out because the input contacts/switch is at a distance, you could use pullup resistors (internal or external) and switch the pin to ground instead.

    Obviously the logic for input detection needs to be flipped, but is a perfectly valid means.

     

    Does this help.?

     

     

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