hi,
im a little confused what is the max v per input pin i take it it will be the same Analog pins as Digital pins, i understand max current is 40ma max
Input Voltage (recommended) 7-12V
Input Voltage (limits) 6-20V
i take it these are the max supply voltages?
thank you
Read the part labeled "Input and Output":
The "Input voltage" in that Arduino specification is indeed the supply voltage, NOT the voltage you can feed to a pin configured as an input pin. The 40mA limit is the maximum current that a pin configured as an output can safely source or sink. The voltage limits of an input pin are about -0.3v minimum to Vcc+0.3v maximum, where Vcc is the microcontroller supply voltage (5v for most Arduinos). However, the Arduino i/o pins incorporate protection diodes, so you can safely feed voltages outside this range to an Arduino input pin through a series resistor provided that the resistor limits the current to a small value (aim for less than 1mA).
The range of voltage you can measure on an analog input pin is 0 to Vref, where Vref is the analog reference voltage, which by default is the same as Vcc.
dc42:
The voltage limits of an input pin are about -0.3v minimum to Vcc+0.3v maximum,
I think you mean -0.5 to VCC+0.5. That is what I remember from the datasheet.
smeezekitty:
dc42:
The voltage limits of an input pin are about -0.3v minimum to Vcc+0.3v maximum,I think you mean -0.5 to VCC+0.5. That is what I remember from the datasheet.
I don't have convenient access to the datasheet right now and I couldn't remember the exact figure, that's why I said 'about'.
It is 0.5, and that's also the "absolute maximum" figure too. Basically don't put large currents through the on-chip protection diodes because they are tiny. 100uA is nice and safe. 1mA might be pushing it a little. 10mA and you get into SCR-latchup territory (avoid at all costs). If you are worried about excursions outside the supply range with significant current the usual protection strategy is to back up the protection diodes with external schottky diodes (which conduct at 0.3V and prevent the on-chip ones from having to take any current).