My project is powered using the dc power barrel jack instead of usb. I need advice on options for supplying power once the project is enclosed. Drilling a hole for the power adapter and just sticking the cord through doesn't seem ideal. I was looking at using a panel mount barrel plug jack like this one here Panel Mount 2.1mm DC barrel jack : ID 610 : $2.95 : Adafruit Industries, Unique & fun DIY electronics and kits or this one here - DC Barrel Jack - Panel Mount - PRT-10785 - SparkFun Electronics but I wasn't sure how to attach this to the board. I have an extra dc 12v adapter so I thought about cutting the barrel plug off leaving a couple inches of the wire still attached. I would then plug it into the board and then solder the wires to the panel mount barrel plug jack. The problem is there are 3 connections on the back of the panel mount barrel plug jack but there are only 2 wires and I'm not sure where each wire goes. It would be nice if there was a similar panel mount that already had a plug that connected directly to the board. If there is a better way, I'm open to suggestions. Thanks you
The fatter lug connects to the center pin (+).
The two identical other lugs are ground (-), and both are a switch.
They are used to disconnect e.g. a battery (-) when a plug is inserted.
Only one is connected to negative of the plug.
You can measure it, or just solder the negative/ground wire to both.
Connect to the existing DC jack if you want reverse voltage protection.
A 12volt adapter could give overheating problems if you are going to connect other things to your Arduino.
Better use a 9volt (or 7.5volt) regulated adapter.
Leo
Thank you. So if I understand you correctly I should cut the barrel plug off my extra adapter and solder the wires to the + and - connections as you directed and then plug the barrel plug directly into the board?
Thanks for the advice on the 9volt adapter. Here is where I got the idea I could used the 12 volt adapter - http://playground.arduino.cc/Learning/WhatAdapter but what I hear you saying is if I'm attaching things to the board (like a servo) I should go with a 9 volt adapter. Thanks again.
The DC socket on the board has a reverse protection diode in series with the +line.
If you accidently use an adapter with the wrong polarity, nothing bad will happen.
Note that the diode drops ~0.7volt.
But that is not bad if you use a 9volt or 12volt adapter.
That link is not entirely accurate. e.g. some boards can't handle 20volt because of a 16volt cap on Vin.
Vin, which is pre onboard 5volt regulator, needs 6.6volt minimum.
Anything more than that is converted into heat in the regulator. Anything less is instability (e.g. A/D the converter).
The DC jack needs ~0.7volt more than Vin. 7.3volt.
That makes a 7.5volt/1A adapter ideal if you're going to hang a lot of "users" on your Arduino.
A 9volt adapter is still ok for a shield and a few sensors.
A 12volt adapter is ok on a "bare" Arduino,
but it's going to quickly overheat (shut down) the regulator with current consuming extras.
Leo..
This one is what you need. Cutting the wire off a working adapter is not recommended. You may need it in the future.
I prefer the sparkfun barrel because it is rear mount, i.e. you insert the barrel from behind the panel and screw it to the panel with the nut in front of the panel. This way you can easily remove the barrel if needed. The adafruit one is front mount. You will have the soldered wire from the panel to the plug (most of the time you solder wires directly to a board) and it's harder to remove the barrel from the panel.