Power supply

Forum 2005-2010 (read only) Hardware Interfacing
1

I have an arduino mini pro board and I plan on running it from a 12v deep cell battery which will also be supplying the power to other components. The recommended input power for the mini pro is 5-12v. I know batteries can at times provide a voltage slightly higher than it's rating. Would the 12v supply from a battery need to be regulated to ensure it does not past 12v or will it be fine with a direct connection.

The alternative is using your standard 9v battery to simply run the arduino and a relay - but I am not sure if it would provide the power needed to run for the 3-4 days required (the coil relay being latched for a total of 12 hrs over the entire period - the arduino - continuous) Any suggestions on the lifespan on a standard 9v to power an arduino and relay? I suppose I could wire two 9v in parallel or a pack of 6 AA.

Thanks for the input

2

Any suggestions on the lifespan on a standard 9v to power an arduino and relay?

About 20 minutes. 9v batteries have the lowest Amp hour rating of any standard battery.

What voltage is the relay? I'd look at powering the relay from the 12V battery, and using a transistor to toggle it on or off, or using a SSR that requires no power except when switching states.

3

problem with most hobby shops is YEA it will handle 16 volts

just like my 7805 will handle 24+ volts, they fail to mention the little details like running linear voltage regulator at that high of an input will produce lots and lots more heat than what is tolerant for the device and package

in my 7805 example, if I just willy nilly dumped 24 volts into it, it would heat up to about 200C (where as like 60C is its max)

Places like SF love to give you a pretty picture and some juicy stats, but most often its totally ignorant of the application / design the part was put in, which IMO makes them a dangerous influence to new, non trained designers, and not much more than someone that will tell you just about anything to get your $$

fact is if your at a regulated 12v your already dropping 7v of it as pure heat, and that thing is a super tiny package with nothing more than a couple solder blobs as a heat sink, it probably runs warm as is, if your battery is super fresh and putting out 14-16 volts its really pushing it

not to mention the load you put on that regulator will multiply that, back to my 7805 @ 12v it starts getting hot to the touch at around 300-400ma, @ 9v its more like near an amp

btw I have some magic beans for sale :smiley:

If you are THAT worried about the max voltage into the Arduino Pro Mini, then throw a couple of diodes in series with the 12V going to the Arduino.

Yea that would work just fine (not second guessing you Richard, u the man) but I would opt for a 9 volt regulator that was designed for battery/mobile/automotive use , which would secure a safe voltage, and give you things like reverse hook up and spike protection all in the IC package

4

Maybe you could use a resistor divider to cut the voltage down.

5

I'm a beginner and am sorta in the same boat. My 12v wall wart puts out 16v. It gets my arduino hot in about 5 seconds. I then wired it to an external larger 7805, takes a little longer but gets to hot. I'm just gonna swap to a regulated 6v wall wart.

Too much power, who knew.

6

6 volt may not be enough depending on what your board has on it, most require 7(.2 or something), I like 9v adapters myself