Powering an Arduino Uno/Micro from a wall socket (or guitar pedalboard)


First thing first: I'm a total noob in electronics, and it's my first project. The project is to create a guitar effect footswitch, that can send out midi signals. So, obviously I need it to be pluggable into a wall socket, or even better, into a guitar pedalboard (USB is out of the question, and batteries are very unsuitable, I only need it to be turned on a couple hours per week, and I'd hate to see the batteries going down at the wrong time, e.g a concert).

So far I have a working prototype on a breadboard with an Arduino Uno, powered by USB, and I have a couple questions I'd like some help on, if you don't mind.

First, I tried to plug this http://truetone.com/1-spot/ into the DC jack, and it doesn't work at all. I have to admit I don't really understand why, it is a 9v DC adapter that works perfectly with pedals... Am I missing something ?

Then I tried to plug in the Line 6 M13 adapter like this one http://www.amazon.com/Line-6-PX-2-Power-Supply/dp/B0002PZEGS . This time it worked, but had some kind of bad contact: it works only when I press on the cable. This might be explained by the adapter though, since Line 6 adapters are a little bit thinner than the "standard" Boss ones. Could it be related to my first issue though ?

Last thing. Ideally i'd like my build to be as small as possible, so I was thinking about getting an Arduino Micro for the purpose. Is there a way to solder a DC adapter on the micro, or even better, to plug some kind of USB/DC adapter ? :)

Thank you very much !

Search amazon.com, there are tons of 120V AC to USB adapters available. http://www.amazon.com/s/ref=nb_sb_noss_2?url=search-alias%3Daps&field-keywords=usb+ac+adapter

Yep, but I won’t be able to plug that into the pedalboard, so it would require another wall outlet and another cable (and believe me, that can get complicated sometimes)…

Ideally I’d need it to be plugged into this: http://cioks.com/index.php?option=com_content&task=view&id=73&Itemid=88

so I really need a DC jack or a usb to DC somehow

Something like this might work, but I live in France, and Amazon.com wont ship it over here: http://www.amazon.com/gp/product/B00EY8IUVA?psc=1&redirect=true&ref_=ox_sc_act_title_1&smid=A1EF9OE38VX40W

Also I'm not exactly sure it's the same jack as the truetone 1 spot thingy...

No, you need something that can plug into the wall. Is there a French equivalent to Amazon you can search at? French Google or something? A cell phone store you can pick an adapter up from?

Well that's what I'm trying to say, the wall is a terrible option for my usage... Why wouldn't it work with a 9V adapter such as the truetone ? It's 9v DC, as said in the arduino doc...

And is there really no way to solder a DC jack to an arduino micro ?

I misunderstood, I thought you were looking for wall power. Check your truetone, is the connector center positive? There is no reason you couldn't bring in 5V thru the USB connector, or the 5V pin on the Power Header, to power the board. Or 9V into the VIN pin to power the board. Or 9V into the barrel jack to power the board. Or connect a barrel jack to the appropriate pins.

If you guitar effects power supply puts out the 9V with a negative center plug (most do) you probably need to just buy a positive center adapter cable. That would be for the Uno.

If your final project uses a Micro or Pro Mini or something like that, you can solder a jack and include a diode to give your board reverse polarity protection. Pay attention to the polarity and use a multimeter to check it.

Aaaaaah, I didn't know about the "center-positive" part :)

Looks like it's not. But i know that there are center positive cable available for my main pedalboard, so I guess i'll figure this out :)

Thank you very much !

One last thing: are there pictures or some kind of tutorials available somewhere about soldering a power jack to an arduino micro ? (I guess i could be able to figure where is the jacks ground or anything, but i'd feel safer if i had some images to make sure i'm not about to burn the whole thing down)

I don't know of any tutorials, but you can probably find some if you google and read long enough. I suggest prototyping your circuit with a breadboard. If you learn about drawing circuit diagrams (schematics) you can post them and ask specific questions here. A picture of a neatly hand-drawn diagram is fine. Photos of your actual hookup may be useful too, if your wiring is neat enough to let us see how it is wired.

Nutshell version

Center pin of 2.1/5.5 barrel jack to anode of 1N4001 diode (Adafruit has both diode and jack) Cathode of diode to VIN of Arduino GND of Arduino to outer sleeve pin of barrel jack

This will make polarity same as the jack built in to Uno

To use a guitar effects cord that has center negative instead of using a positive center cord/adapter, reverse the connections to the jack.

You've probably been applying -9V dc to the arduino external power input and the diode is blocking it. If you have a meter measure the plug to see if it is center positive.

Thank you very much :)

Something like this might work, but I live in France, and Amazon.com wont ship it over here: http://www.amazon.com/gp/product/B00EY8IUVA?psc=1&redirect=true&ref_=ox_sc_act_title_1&smid=A1EF9OE38VX40W

Also I’m not exactly sure it’s the same jack as the truetone 1 spot thingy…

As far as I can see, this one provides a 9V/250mA output, and you can use that to feed power to Arduino boards connecting to the Vin pin.

An UNO board will use something around 55ma, so with a 250mA power source you could connect additional hardware to the UNO which might use up to additional 195 mA without damaging the 250mA power source.