Hello, I just bought a 9 volt power supply that plugs into the arduino jack and electrical outlets. When I ran my program off of the 9 volt power supply I noticed that the analog input to digital output signals were very noisy compared to when I was using my usb to run the program. I tried a smoothing filter(http://arduino.cc/en/Tutorial/Smoothing), but the signal was still quite bad compared to just using the usb. Any advice on what to do?
Any advice on what to do?
Did this power supply come in a white box that said "9V Power Supply" with no other text, or is there a manufacturers name/web site/other details that you can share?
You should read the value of the Vin pin while the external power supply is powering your board. Also did you make sure the 9V supply was a DC and not a AC module? Also what was the output current rating for the module.
I'm sure somewhere in those questions is the root of your problem symptoms.
Lefty
It is a AC/DC adapter. The input is 100-240v AC 50/60 hz
The output is 9VDC 650mA. I'm not sure about the brand.
How can you not be sure about the brand? Is there not a label on the device?
Are there not any Agency Approval stickers on the device? Is this more cheap
unapproved, electronics crap from CN?
Here is your advice:
If the answers to these questions are unsatisfactory, then throw the friggin thing
out and buy something that is approved. The approval sticker(s) will be obvious.
We just had another overly long and totally wasteful thread about plugging cheap
junk into the power mains. If you're smart, you won't do it.
One way to address your issue is to use a reference, either internal or external, for the adc.