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### Topic: Maximum Supply Input Voltage? (Read 72781 times)previous topic - next topic

#### WheelerMDW

##### Mar 02, 2010, 07:26 pm
Hey guys,

I know that 9V batteries are sometimes used to power the Arduinos, but I was wondering about 12V supplies?  Can the Arduino handle a 12V input voltage without damaging the regulator, or should I go ahead and build a voltage divider for the input voltage?

#### digimike

#1
##### Mar 02, 2010, 07:34 pm
12V is fine. Here is a good resource for questions like this.
http://arduino.cc/en/Main/ArduinoBoardDuemilanove

#### Grumpy_Mike

#2
##### Mar 02, 2010, 07:41 pm
Quote
should I go ahead and build a voltage divider for the input voltage?

Never even think for one instant of using a potential divider to power anything. It wastes so much power that it is not practical. As a rule you have to have at least 10 times the current down the divider as you want to tap off. So if you need 200mA of power you will need at least 2A in a potential divider burning all that power in heat.

#### WheelerMDW

#3
##### Mar 02, 2010, 07:50 pm
Thanks for both of your input.

#### RanTalbott

#4
##### Mar 02, 2010, 08:07 pm
Quote
Can the Arduino handle a 12V input voltage without damaging the regulator

That depends on which Arduino you have,  what you have connected to it,  and what you mean by "12V".

Most of my Arduinos have TO-220 regulators on them, which can safely dissipate a lot more heat than the surface-mount regulators on many models.  But I still need to use external 5V supplies for projects involving,  say,  servos,  or lots of LEDs.

Many (probably most) "12V" plug-in supplies are unregulated,  so they could easily be putting out as much as 15-18V when loaded at much less than their rated current (if the rated current is less than 1A,  the odds are very high that it's not regulated).  And the "12V" in cars and trucks is actually supposed to be more like 13-14V in normal operation,  and can have huge spikes from the motors used for wipers,  power windows,  and other reactive loads.  Those spikes can damage the regulator and/or the rest of the Arduino if you don't add protective circuitry.

#### WheelerMDW

#5
##### Mar 02, 2010, 09:35 pm
Thanks again.  It's a Mega with the regulator surface mounted to the board.

The supply will be a regulated 12V supply.  It is a power supply from a PC.  I am working on a project that requires both 12V and 5V, so I thought I would just supply 12V to the Mega from one of the regulated 12V outputs from the PC Power Supply.

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