Arduino UNO is sensing two temp sensors and when the difference is greater than a certain value pin 13 goes high to turn on a mosfet. The mosfet is driving 2 12volt 0.25 amp muffin fans. The setup works fine when the arduino is connected to the computer and receiving power from the computer. The 12v positive is hooked up directly to the positive of the motors, and the ground from the 12v supply is along the same common "rail" as the arduino so all grounds or negatives are the same.
If I take the very same circuit that was just working, disconnect the usb, supply the Vin pin of arduino with a jumper to the 12v positive, then feed the arduino 5V out to the rest of the circuit to power the temp sensors, etc, it doesn't work and pin 13 onboard arduino led is very dim. Any ideas what might be going on? Thanks.
I will try testing the 5v out with 12v in. Will also test it with no connections to the arduino other then power.
I have an external 5v regulator that I had in the system and I got the same results. Output of regulator was tested independent of any other connections and it was outputting 5v. I then connected Vout to Vin of the arduino (which I now realize isn't good as UNO board needs at least 7v in to be stable??). Can I use an external 5v regulator in this setup or does it need to 7v or higher? Thanks.
To keep all data regarding this project in one post, I'll ask this here. I want to output via the serial port data that can be imported into excel. CSV is common and is what I'll be using. I need to include the time, any code suggestions to output time? I researched this and found the arduino time library: Arduino Playground - Time but I get compile errors and I don't know if this code is overly complex for my needs. It highlights "import processing.serial.*;" and says "import does not name a type". Do I need a library somewhere that it can't find? Thanks for any suggestions.
PS I haven't figured out the power issue but for now it's working with the pc connected and power supply running the 12v fans so I'll just leave it be and fix it later.
You are right. I found that out afterwards. I got it worked out now just outputting csv formatted code, adjusted time intervals in excel, and got my data. Thanks.
Ok, I'm back on this project and the serial port/power supply issue is on my mind again. I would like to try and figure out this mystery problem. I've done some reading and searching. Could this be the issue:
Could the voltage from the 12 volt supply be feeding back into the USB and turning off the USB connection at the computer? I consistently have this USB no com port issue found when I use an external power supply the I feed into the UNO via the header pins grnd and Vin. On the pc the com port is greyed out and it won't communicate between the pc and arduino UNO.