Problem usin 5V pin and Serial on COM8 at the same time?

I have an UNO and can't use the 5V pint and read from serial on COM8 at the same time? whenever I try to nothing happens with Arduino and the IED says something else is using COM8. Is Arduino able to handle both at the same time or am I doing something wrong?

There should be no problem at all using the 5v pin and the serial monitor at the same time. I don't know about the 5v pint!.

Mark

show some code, please. also how are you using the 5v pin? my guess is that you are drawing too much current, but more details are needed.

When I use the 5V pin to power a Temp/Humidity sensor the Arduino says COM8 is in use so I can't read the serial, but when I am using the 3.3V pin it works. Problem is I need both for this project so I have to unplug things then unplug the Arduino and mess around and wait a while before I am able to see COM8 as an option again to read from it. My code is pretty simple andI am using the DHT library to read from the sensor which is the RHT03.

I have also had this problem long before I was using the sensor. Anytime I plug something into the 5V of the Arduino my computer makes the babum sound and I have had trouble uploading to the Arduino before because of this COM8 problem that I am pretty sure is associated with using the 5V pin.

masterwigglestin:
When I use the 5V pin to power a Temp/Humidity sensor the Arduino says COM8 is in use so I can't read the serial, but when I am using the 3.3V pin it works. Problem is I need both for this project so I have to unplug things then unplug the Arduino and mess around and wait a while before I am able to see COM8 as an option again to read from it. My code is pretty simple andI am using the DHT library to read from the sensor which is the RHT03.

I have also had this problem long before I was using the sensor. Anytime I plug something into the 5V of the Arduino my computer makes the babum sound and I have had trouble uploading to the Arduino before because of this COM8 problem that I am pretty sure is associated with using the 5V pin.

That is usually an indication of what you are trying to wire up to the 5V pin is either drawing too much current or is a short circuit to ground. There is a 500ma current limit when on USB power and the PC will bitch if you try and draw more then that. There is a 500ma thermofuse on the arduino board to help protect the PC but it's somewhat slow reacting.

Bottom line is be very careful with what and how you wire stuff up to the 5V pin. Post your wiring drawing here first if you have an doubt on if it's correct or not.

Lefty

Can I use a higher amperage is I power the Arduino from a battery or other source?

masterwigglestin:
Can I use a higher amperage is I power the Arduino from a battery or other source?

Not really you don't gain much, the 5V pin will always have a current limit, either 500ma USB limit or the heat dissipation rating on the on-board 5 volt regulator if powering the board via the DC connector (Vin).

However there is nothing preventing you from using an external voltage source power supply to power your external stuff, just be sure to add a wire from the external power supply negative terminal to a arduino ground pin.

Lefty

Anytime I plug something into the 5V of the Arduino my computer makes the babum sound and I have had trouble uploading to the Arduino before because of this COM8 problem that I am pretty sure is associated with using the 5V pin.

Again reaffirms my guess that you are drawing too much current from the 5v usb rail, but it is still a guess. We need details.
What exactly is plugged into the arduino? (A datasheet would be helpful as well as a diagram/schematic)
And what else is plugged into your usb ports? mouse, keyboard, webcam, coffee cup warmer...? Have you double checked your connections?

Thanks I think you were right about it being too much current. I added a 100 ohm resistor to the 5v pin and it works fine now. What were you guys saying about grounding the Arduino to the external power supply though? I am going to power the Arduino with a 9VDC transformer connected to my 120 VAC wall outlet.