Power supply for Ardunio UNO project

Other Hardware General Electronics
1

I'm almost past the development stage and looking to power an Arduino UNO from 120V instead of batteries. I'm powering the UNO, some sensors and in one case an Ethernet Shield. No motors, servos, or steppers - fairly low current draw.

I have a collection of wall warts, and a universal PS "replacement" that allows me to set a designated voltage.

I don't want to fry my Arduinos, so I took some readings. What I'm seeing is that these devices will put out close to the rated voltage under load, but open circuit the voltage varies significantly from the listed output.

Also, even when the DC output is within the range I'm looking for (6-12VDC), there is a very significant AC component as measured on the AC range of an older Fluke DMM - sometimes well over the DC rating. For example, 12AC with a 9VDC reading.

Am I safe in using this kind of PS with the Arduino? Will the fact that the PS is unfiltered (to say it mildly) and unregulated be a problem?

If not, can anyone offer a source for a small plug in PS (wall wart style)? If possible, something under 12V so we're not heating up the onboard regulator (I worry about that and long term life expectancy, maybe I'm wrong to do so).

I know I can use a PC power supply, and have done so for development. They're rock solid, but kind of big for the application.

Thanks.

2

I bought a 12V 10A AC adapter (wall wart style) on eBay, and it has worked fine to power my Arduino and LED strips.

3

Why not just use a USB phone charger?

4

I was thinking about that but don't really know how good (eg., regulated and filtered) they are.

I have a couple from old phones, either 0.5A or 1.0A., which should be enough for my needs.

When connecting through the USB connector, doesn't that bypass the regulator? Is this safe - I don't want to fry my Arduinos?

Thanks.

5

Use a decent switching regulator - they are small, have auto-detect & shutdown if shorted, and run cool.
The old phone adapters are merely transformers with a diode bridge, caps and perhaps. Output can be very ripply, and also not very stable.

7.5V if you want to power via the barrel jack
http://www.dipmicro.com/store/DCA-07510

5V if you want to bypass the regulator and power via the 5V/Gnd header:
http://www.dipmicro.com/store/DCA-0510
Add a diode from 5V (anode) to Vin (cathode) to avoid reverse driving the 5V regulator.

USB does connect to the output side of the regulator. Don't get that connection backward.