# New to this, have a vcc input question

Hi all, I just started messing with this arduino and electronics stuff and I have a project in mind but I have some questions.

Right now the plan is to power the arduino off of a cars 12v power, or up around 14v when the car is running. What I need to figure out is should I limit the voltage using a separate circuit, or will the arduino be albe to handle the 14ish volts in, for extended periods of time while the car is on. I want to box my little project up, so heat is my concern. If I do need to limit the voltage in, what would you recommend to do this, testing with a dc power supply I have seen my output fluctuate if the voltage is less than 6v so I would like to keep it above that. Thanks for the help. I have some other questions about mosfets and solenoids that I will save for another post so if your a pro on those let me know. Thanks again.

Welcome!

Here in the middle of the page you will find the limits of the voltage input is 6V to 20V so you are right, the voltage needs to stay above 6V but 14V will be fine. The voltage regulator on Arduino is just a bit warmer then.

When you crank your car, you may momentarily lose your power so if you don't want that to happen, maybe have a large enough capacitor to stabilize the voltage.

Actually, for larger Vin, the heat buildup in the voltage regulator will be a serious problem, depending
upon the v.reg on the board [eg, tiny smt SOT-223] and the load currents. For Vin = 12v, you can
probably only draw 100-200 mA, and not the 1A usually advertised for the v.reg. See last couple of posts
here,

If you have a couple of bridge rectifiers in your junk box, you can put them in series ( out of the box that you want to keep cool ) and they will get rid of 1.2v each ( just feed the 12v in to the -ve leg - cut off the AC legs - and take the voltage out of the +ve leg )
Its better than a resistor as the voltage dropped is basically independant of the current drawn.

Wouldn't this circuit work? then the heat wouldn't be in the arduino board? My outputs off the arduino will not be driving any motors or anything, they will be sending a voltage to a logging system only, not sure if that makes a difference.

Yes, you can use this ckt in the Vin line to the Arduino bd to drop the voltage. Now the heat will just
be moved to the 2N3055, which are generally huge parts and easy to heatsink if necessary. Try the 7.5V
setting.