Hi
I'm new to the field of electronics in general, and the Arduino, in particular. I have a basic understanding of what an Arduino does and the components that go into it - this I gleaned from all the youtube videos.
Anyway, my question is: once I connect a 5V power source (via the JACK) to the arduino Uno (R3), are all the pins on the board supplied with 5V?
I'm trying to develop a mental picture of the way current will flow within the board (see attached for a poor example) - I believe this will help me visualize the circuitry required for my personal projects better.
Thanks & regards
I hope you enjoy your new hobby!
In regards to your question, what I think you are asking is if there is going to be a short if you plug in/turn on the Arduino.
Indeed, the potential for a short is there. Since it is an I/O pin, if it became an output it would attempt to drive a voltage into the ground and possibly damage the pin or the entire board. It depends on how the Arduino is programmed. It might be used as an input in which case there would be no problem. If you are worried, a 270 ohm resistor in series should prevent anything permanent from happening and still allow most circuits to work.
Going a bit deeper than needed, that particular pin has alternate functions as an input. According to the ATMEGA8 datasheet:
Port D is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port D output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port D pins that are externally pulled low will source current if the pull-up resistors are activated. The Port D pins are tri-stated when a reset condition becomes active, even if the clock is not running. Port D also serves the functions of various special features of the ATmega8 as listed on page 63
XCK/T0 – Port D, Bit 4: XCK, USART external clock. T0, Timer/Counter0 counter source.
Do not connect 5V power through the jack, it is not designed to do this. If using the jack you have to use any voltage between 6.5V and 12V to allow the internal voltage regulator to make 5V.
I would not go below 7V on the jack because of the diode drop as well. It you want to use 5V, easiest way is to do that via de USB (from a USB charger).
But no, if you power the Arduino you have 5V on the Arduino and the 5V pin (and 3V3 on that pin). All the output pins do what you tell them to do (in code). By default they're inputs so they float (same as a not connected device). If you set them as output and make them HIGH then there is 5V, if you set them LOW they are connected to GND.
Hi,
There are a lot of details on this subject HERE:
The UNO schematic is HERE:
I'm trying to develop a mental picture of the way current will flow within the board (see attached for a poor example) - I believe this will help me visualize the circuitry required for my personal projects better.
It is not clear what your point is. An I/O pin can be either INPUT or OUTPUT. You have specified neither and provided no code so your schematic is irrelevant until you do. An input is high impedance. It draws about 165 nA (less when shorted to GND). An OUTPUT can be damaged shorting it to GND.
I fail to see how drawing a short on an I/O pin will help you visualize the circuitry required for your personal projects. What does a short have to do with the circuitry needed for your projects ?
