I have a couple questions regarding it: the power supply has a +V and -V as well as ground. does it matter what V i use? I have planned to run things off of 12V but does it matter if i plug into +12V or -12V? Also if i were to connect the +V and -V through a load, would i get a voltage difference of 24V then?
And if i want to use it to power the Arduino when there is no computer do i have to wire a special plug to the PSU so can get it in the Arduino's power port or can I put a wire directly to the Vin pin on the board and connect the grounds? (i was going to link everything a common ground anyway)
You should use V+ and GND to power the Arduino. Using V- will be like connecting it backwards. You may also be able to use V- and GND if you use V- as GND and GND as Vin, but only if the Arduino isn't connected to a computer, or Magic Smoke™ will escape.
You can apply the V+ direct in to Vin, yes, but make sure it's a good secure connection - a 12V wire slipping out and touching something it shouldn't is nasty. A proper plug is better.
Remember that the Arduino is 5 volts only. Do not connect anything above +5Volts to the Arduino, except 12 volts can go to the power jack.
Use +12V and ground only. Do not use -12Volts anywhere on the Arduino or sensors that connect to it, for now.
I would agree with Fungus. "V-" is the DC negative return path which is probably isolated from earth ground . Earth ground should be connected to mains grounding system for safety. In any case Probe it to be sure. Rarely, these cheap SMPS power supplies are dual voltages unless specifically marked. If you use Vin, you best be absolutely sure of your polarity.
omgnames:
I have a couple questions regarding it: the power supply has a +V and -V as well as ground. does it matter what V i use?
I think it's just weird labeling and "V-" really means "GND".
Looking at the spec sheet:
-V is the negative terminal of the 12V supply,
+V is the positive terminal of the 12V supply.
PE is the protective earth connection.
There is no "ground" connection, you are free to choose ground.
Note that this is an isolated supply, but the output terminals mustn't go too far from
earth (the input-output isolation is tested to 3kV, but output-earth isolation is only
tested to 500V)
The leakage current is under 1mA, which means the outputs could be floating
at mains voltage levels if not tied to PE somewhere - recommended unless you have
a genuine reason not to.
The first thing you should do when it arrives is probe it with a multimeter.
Definitely - your multimeter is invaluable all the time, check everything
you can and fewer expensive mistakes will happen. In particular you can
verify voltage and polarity.
The leakage current is under 1mA, which means the outputs could be floating
at mains voltage levels if not tied to PE somewhere - recommended unless you have
a genuine reason not to.
I would get shocks from my bench supply because i leave Jumper wires sticking out of the Ground rail on the breadboard. Every now and then my elbow would brush across one and i would feel a sharp stinging sensation. It took a few times to realize what was going on. Probing V- wrt ground shows about a 30 volt difference :/.
MarkT:
Note that this is an isolated supply, but the output terminals mustn't go too far from
earth (the input-output isolation is tested to 3kV, but output-earth isolation is only
tested to 500V)
Unlikely to be a problem ... but it might be worthwhile tying "V-" to the ground terminal with a little wire jumper - give it a solid reference point.
(ie. The screw terminal for earth will have two wires in it, one to mains ground and the other to "V-")
This trick can also save you from pain if you're using multiple power supplies and you forget to connect all the grounds together (although it shouldn't be a substitute for doing that - belt+braces...!)
seanz2003:
I would get shocks from my bench supply because i leave Jumper wires sticking out of the Ground rail on the breadboard. Every now and then my elbow would brush across one and i would feel a sharp stinging sensation. It took a few times to realize what was going on. Probing V- wrt ground shows about a 30 volt difference :/.
This trick will help with that, too...
I've seen differences of much more than 30V. In theory you're safe to grab the wire because it's floating but yes, it will tickle you if you brush it lightly.
nb. Connecting V- to GND will take away some of that safety. If there's bare V+ wires lying around you might be better off not doing it. I don't think it's a problem for 5V/12V supplies but ... it's your decision...
The GND of Arduinos is usually connected to mains ground via your PC and I suspect you've touched Arduino 5V wires many times.
