Hi,
I was wondering what is going on here. I have a third party arduino and I am trying to control a mosfet at 10.7 volts. However after a day of messing around with the wiring, I decided to check the voltage on the multimeter of the gate pin. This showed me that coming out of pin 13, there was a negative voltage of about 5 volts coming out compared to the arduino ground. I was wondering what is happening here like if this is a known issue or bug. I haven't been able to find anything on the internet about this so im coming here to ask. With this I switched to using pin out 10 and this seems to work perfectly fine. So with this my initial thinking is that there is a faulty chip that I cant remember the name of that operates the digital output signals, but Im not sure. Any ideas would be greatly appriciated.
One idea is to read and follow the instructions in the "How to get the best out of this forum" post, linked at the head of every forum category.
-5 volts out of pin 13? I really don't think so.
Show us an annotated schematic. And clear, well lit, in focus pictures of your actual wiring.
Without a schematic of your circuitry, we can't be sure what you might have done to see -5 V at that pin, but pin 13 on an Arduino Uno (and most similar clones) drives the onboard LED circuitry thus behaves differently than most of the IO pins.
It's best to only use that pin as a last resort and with full understanding of the onboard LED circuitry.
No way that happens.
You likely twisted the polarity. Arduino GND should connect to multimeter negative and the positive multimeter probe do the measuring.
Hi, @dummyrock
Welcome to the forum.
Can you tell us where you connected the two DMM probes, Red and Black?
Do you get a proper positive reading between gnd and the 5V pin.
Tom.... 
What did you use as a reference for your measurements?
Hi,
Sorry I'm new to this posting thing, I don't really do much with wiring diagrams and don't therefore know how to make a good one, so hopefully you guys can see the image that I have put in here of just simply pinout 13 to positive of led and ground to the ground pin with a 1k resistor like in the image. I had the positive point of the multimeter on the positive side of the led and the negative side to the negative side of the led and it was reading -5 to -4.5 volts across the led. Im out of the house but when I get back Ill take a picture of what I was doing and the reading.
But your image use pin 11 to Led any way it should not be -5V.
You are measuring the voltage across the LED not the voltage output by the Arduino pin. Try measuring that instead
Check that you don't have multimeter probes inverted and that it's set to measure DC voltage.
I didn't create this image I just found it on the internet, I used pin 13 this is just an example of what I did without me creating something that I don't know how to.
I had my multimeter probes in the correct direction and it is measuring dc.
Then your reading across the LED should be 2-3V (LED on).
Anyway measure voltage between your arduino 5V pin and GND
If someone asks you for help, you would like to have the whole picture in front of you and not get a surprise later on.
Give actual info, please. Everything else waste everybody's time.
There are internet sites where you can make a diagram and post, or you could easily have drawn a square that would represent your UNO, write 13, +5V, GND in that square like it's marked on your real UNO, draw wires, resistor and LED. Then upload a photo of it. If you do this diagram with a graphite pen, you can even edit and reuse it with an eraser.
I'm +5V positive you didn't get -5V by not somehow measuring it backwards. An Arduino doesn't deal with -5V.
You don't know how to put pen to paper, draw a diagram and take a picture of it?
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