Im confused as a new Arduino owner. I would like a picture showing which pins can output 5V and which output 3.3 volts ?
Can it power a 5Volt device when using the USB as its power sourse ?
Appreciate your help very much.
Mike.
Most Arduino boards run at 5V.
Those boards have digital pins, that can be 0V or 5V if set as output.
The extra 3.3V output is to power sensors and so.
Some Arduino boards run at 3.3V, they don't have 5V at all.
Which Arduino board do you have ?
You can power a 5V device using the 5V pin. If some current is required, the usb voltage might drop a little, and the 5.0V might be 4.8V.
Can it power a 5Volt device when using the USB as its power sourse ?
That depends on what you mean by "device".... powering a sensor is one thing, like the 5V supply to an LM35 temperature sensor, but don't even think of powering a motor, no matter how you power the Arduino.
I'm using an Arduino UNO
Ive used an L298N motor controller to control two motors. I have a seperate battery pack wired into the L298N to power both the Motor Controller and the motors through it.
The logic pins are connected to the Arduino, I can control enabling pin A or Pin B or set both high to enable both motors. Then there are the IN1 to IN4 to control what the motors do. I think the arduino is using 3.3 volts to set all these pins. I used the pis 1 to 13 (obviously not all of them for the 6 pins I need.)
One the other side of the Arduino UNO there are 8 female headers.plus 6 analogue headers.
Here is what is printed beside the female Headers. Only 6 directions so the top two female headers I don't see what they are for ? two blanks ? Its this side of the Arduino I want to understand !!
reset
3.3v
5v
Gnd
Gnd
Vin
So to me it looks like there is only one pin/header where I can get 5V ?
Why are there two Ground pins , one for the 5V and one for the 3.3volt ?
I think the pins I used to control the logic were 3.3volts.
Im using an external power pack of 6.3 volts. It seems to drive the two motors just fine.
Actually, i just read that the Arduino Uno output pins are all 5volt.
Next Im going to try and use a small chip that can also power both motors its tiny compared to the L298N. The little chip is a SN54410NE, but I have to find a simple drawing first 
Why are there two Ground pins , one for the 5V and one for the 3.3volt ?
All the ground pins are the same, in fact there are three, another one is on the other side of the board.
As you get to know electronics better you will see that ground pins are needed more often than power pins.
For a great set of diagrams see:-
http://jobs.arduinoexperts.com/2013/03/02/arduino-atmega-pinout-diagrams/
Thanks for that excellent diagram. I have gathered that the pin numbers of the actual chip are not the same as the pin/headers of the board. There is some interesting stuff going on that will take a bit of experementing and projects to fully understand(if i need to)
Is the Tx , RX meantg for wiring up possibly a UHF setup like the Xbee ? It cant have anything to do with the programming of the board !
There is a lot to learn on that diagram but thank you.
A question totally unrelated but something im curious about.
If I used a 9V battery as a power supply, or had a 9V power pack using AA batteries. Woud the AA 9Volt supply more amps or just last longer ?
If I used a 9V battery as a power supply, or had a 9V power pack using AA batteries. Woud the AA 9Volt supply more amps or just last longer ?
Things only draw the current they need, so a power source with bigger mAh capacity could provide the required mA for longer hours. (edit:.... assuming they can provide the required current in the first place)
I have gathered that the pin numbers of the actual chip are not the same as the pin/headers of the board.
See this:-
http://www.arduino.cc/en/Reference/PortManipulation
Is the Tx , RX meantg for wiring up possibly a UHF setup like the Xbee ? It cant have anything to do with the programming of the board !
Yes it is used to program the board by being attached to a USB / Serial converter chip also on the board. Do not use pins 0 & 1 unless you know exactly what you are doing.