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Author Topic: Voltage input on digital pin (Arduino Uno)  (Read 1383 times)
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Hello all smiley

What is the lower limit of voltage, the Arduino Uno will register on one of the digital pins?

For example, a curcuit is connected trough Arduino 5V and GND and have a output at only 0,5 volt. Will the digital input pin register that?

Thanks smiley
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... 0,5 volt. Will the digital input pin register that?
As a LOW, yes.
I wouldn't expect anything < 3V to be a consistently reliable "HIGH".
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So if I go below 3V on a digital pin, the Arduino Uno would not register it as HIGH.
Thank you smiley-grin
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Hello all smiley

What is the lower limit of voltage, the Arduino Uno will register on one of the digital pins?

For example, a curcuit is connected trough Arduino 5V and GND and have a output at only 0,5 volt. Will the digital input pin register that?

Thanks smiley

Those values are best defined and explained in the Atmel ATmega329p datasheet along with all the other electrical specifications for the chip.

Lefty
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So if I go below 3V on a digital pin, the Arduino Uno would not register it as HIGH.
Thank you smiley-grin
Well, I didn't "say" that, but you asked about "0.5V"
In fact there's a point at which a voltage "must be" a HIGH and a similar point where some voltage "must be" a LOW, but there's a window of uncertainty between the two, a sort of no-man's land which should be avoided.
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Those values are best defined and explained in the Atmel ATmega329p datasheet along with all the other electrical specifications for the chip.

Lefty
Unfortunately, that didn't help me  smiley-confuse

Well, I didn't "say" that, but you asked about "0.5V"
In fact there's a point at which a voltage "must be" a HIGH and a similar point where some voltage "must be" a LOW, but there's a window of uncertainty between the two, a sort of no-man's land which should be avoided.

What voltage is that between? The uncertainty about "HIGH" and "LOW".
If you should say a voltage, were it would not anymore register a value as "HIGH" or the highest voltage you can think off, were it not at all would read it as "HIGH". (at least theoretically?)
Sorry... But I really need some sort of number, since I have made an error with an operational amplifier...
Hope there is some kind of possible answer  smiley-sad
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Unfortunately, that didn't help me
It's all there in the data sheet.
In what way didn't it help you?
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For an input to be seen as a logic low it must be below 0.3 * Vcc so at 5V Vcc this is below 1.5V

For an input to be seen as a logic high it must be above 0.6 * Vcc so at 5V Vcc this is above 3V
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