Hello everyone! I am working on an LED project that will go into my car. The project itself is going great, but the only issue i am running into is powering the arduino. How would I power the arduino? I want a dedicated hidden wire, so using a lighter adapter is not an option. Would I need something special for voltage regulation (ebay link would seriously help)? Would i go off a fuse or straight from the battery? Literally have never messed with any wiring in regaurds to cars, so this is a first for me lol. Any help is appreciated!
The problem with a car's electrics is the risk of large voltage spikes from the
starter motor and suchlike - so its wise to ensure a power supply is able to
deal with these. If you can simply use a purpose-made USB charger you save
yourself all the complexity. Simply connecting the battery positive to Vin
is fraught with risk and isn't recommended.
Its normally a good idea to have some RF filtering, a TVS or similar to tame
overvoltage spikes and a good regulator chip or DC-DC converter that will
handle a wide range of input voltages - expect the battery voltage to drop
to 6V or so on starting, upto 14V during charging, and various spikes and noise
can also be present (especially once the battery itself is getting old).
And of course a fuse is mandatory.
^^^ Everything MarkT said...!
MarkT:
The problem with a car's electrics is the risk of large voltage spikes from the
starter motor and suchlike - so its wise to ensure a power supply is able to
deal with these. If you can simply use a purpose-made USB charger you save
yourself all the complexity. Simply connecting the battery positive to Vin
is fraught with risk and isn't recommended.Its normally a good idea to have some RF filtering, a TVS or similar to tame
overvoltage spikes and a good regulator chip or DC-DC converter that will
handle a wide range of input voltages - expect the battery voltage to drop
to 6V or so on starting, upto 14V during charging, and various spikes and noise
can also be present (especially once the battery itself is getting old).And of course a fuse is mandatory.
I know this might be asking a lot, but could you find me a specific DC-DC converter that would be up for it on ebay? Im still a bit new when it comes to this entire arduino/electric engineering world, so I dont want to mess up and buy the wrong item that cant handle the spikes of electricity. I will look into RF filtering and TVS when I get off work. What ever it takes :D!
Try this http://uk.farnell.com/xp-power/iu1209sa/converter-dc-dc-2-1i-p-2w-9v/dp/1435417, will take 9V to 18V input and give you 9V out to go a barrel plug http://uk.farnell.com/multicomp/mp-136/plug-low-voltage-2-1mm/dp/1737256?MER=en-me-pd-r2-acce-con. You may find these on Ebay. 
Billysugger:
Try this http://uk.farnell.com/xp-power/iu1209sa/converter-dc-dc-2-1i-p-2w-9v/dp/1435417, will take 9V to 18V input and give you 9V out to go a barrel plug http://uk.farnell.com/multicomp/mp-136/plug-low-voltage-2-1mm/dp/1737256?MER=en-me-pd-r2-acce-con. You may find these on Ebay.
Would this be alright? LINK. Just want to be sure before i buy and wait on it haha.
You want to go from 12 to 5 so buy a step down converter.
I've used HERE
The converter LarryD lists is ideal.