Arduino Forum

Using Arduino => General Electronics => Topic started by: Stoil on Nov 18, 2018, 12:52 pm

Title: 12V power supply.
Post by: Stoil on Nov 18, 2018, 12:52 pm
Hello,
Would this transformator work to power the arduino ?
(https://scontent-sof1-1.xx.fbcdn.net/v/t1.15752-9/46493672_2071898582871871_5276654948505878528_n.jpg?_nc_cat=100&_nc_ht=scontent-sof1-1.xx&oh=3152ed44df79c83ccd7c4cbbae80d9e3&oe=5C68B7E6)
I think the current is too high ?
Regards
Title: Re: 12V power supply.
Post by: Paul__B on Nov 18, 2018, 01:54 pm
No, an Arduino requires regulated 5 V.

If you feed 12 V to "VIN" or the "barrel jack", the internal regulator can supply only about 100 mA or so which is really only enough to power the microcontroller and a few LEDs at 10 mA each.

You also have to be careful with LED drivers.  That one appears to actually provide a regulated 12 V at any current up to 3.2 Amps so you can use it to power 12 V devices, but many are constant current drivers which will deliver anything up to their maximum rated voltage in order to deliver the specified current - they are not voltage regulated as such, but current regulated.
Title: Re: 12V power supply.
Post by: ElCaron on Nov 18, 2018, 02:41 pm
I think the current is too high ?
If a single voltage value is given, the current is NEVER too high. For a given voltage, the current is always automatically determined by the effective resistance of the circuit by Ohm's law. Any given current value is only the max that can be supplied.

As Paul__B said, there are also constant current supplies. They will state a current and a voltage range. Within this range, the voltage will be adjusted to the effective circuit resistance to yield the specified current.

As I said be quite a few times before, there should be a Basics forum with stickies like this. This question has come ob SO often now ...
Title: Re: 12V power supply.
Post by: MarkT on Nov 18, 2018, 03:42 pm
Constant voltage supplies don't control the current, they provide as much current as is needed, upto some maximum limit, while actively controlling the voltage.
Title: Re: 12V power supply.
Post by: Wawa on Nov 18, 2018, 09:20 pm
What do you mean with "the Arduino".
There are many shapes and sizes in that family.

An Uno/Nano/Mega is best powered with a 5volt cellphone charger, connected to the USB socket.
Leo..
Title: All that said,
Post by: Paul__B on Nov 19, 2018, 05:13 am
Mind you, I am a bit concerned about the blister in the middle of the label on that power supply.  It is new and working properly, isn't it?  Not from some rubbish you found?