Power arduino from 12 volts? - Page 1
Forum section: electronics / beginners

author: EEVPiobee
author_rank: Contributor
timestamp: February 07, 2014, 08:39:33 am
content: Hello there!What is the best way to power an arduino chip (ATtiny, ATmega etc.) from a 12 volt (regulated) source? Is this the Classic LM7805 voltage regulator or is there a more efficent way to do so? (less loss of power thru heat dissipation)Thank you!

author: VK5RC
author_rank: Unknown
timestamp: February 07, 2014, 09:28:36 am
content: I have used one of the small switch mode dc-dc converters (one with not too much ripple) with success. Got it from MiniKits in Sth Australia, regards Rob

author: PICmonster
author_rank: Regular Contributor
timestamp: February 07, 2014, 10:06:55 am
content: Using a linear reg is the cheapest and most traditional way and has less noise at the expense of power dissipation, a switcher is more efficient so runs cooler but has more noise as mentioned, this noise could be a significant proble when using ADC, generally the higher the ADC resolution the more power supply noise becomes a problem.

author: EEVPiobee
author_rank: Contributor
timestamp: February 07, 2014, 11:00:32 am
content: Thank you for the hints!Now mentionning the ripple, I guess I'm gonna go for the voltage regulator since I haven't thought of that problem (deh!) ...Maybe on some other project I'll go with a dcdc when I'll need the arduino not to fail on any voltage circumstance (with proper filtering of course!)But... It makes me wonder... If I use a DC-DC to step down from whatever voltage input (let's say 24 for this example) down to 7.5 ( keeping some headroom) and -then- put in a LM7805 to clear the 5 volts would it help? or am I looking only for headaches and trouble?...(Actually, I'm considering the user dumb enough to eventually use the wrong power supply with the module I'm building)

author: sleemanj
author_rank: Super Contributor
timestamp: February 07, 2014, 11:08:47 am
content: Quote from: EEVPiobee on February 07, 2014, 11:00:32 amYes that's a common configuration.Of course, you still need appropriate filtering caps on the 7805 (which you need anyway even if you don't use a DC-DC).

author: VK5RC
author_rank: Unknown
timestamp: February 07, 2014, 12:00:19 pm
content: Bizarrely, I got quite a bit of confidence using some of these dc-dc switchers after using one inside a 3W RF out 10GHz microwave transverter. I was expecting the harmonics to drive everything into overload but it went OK. I have since found several dc-dc converters inside commercial kits for amateur radio microwave transverters (they still have to meet stringent spurious radiation limits, typically harmonics less than 80dB).These in-the-field Ham microwave transverters are a DC power supply nightmare, often 13.8V in, and you need -7, +5,9,12,24V in a single unit!I used an Arduino (with its display shield- I know I am lazy) as a relatively quick way of displaying several bits of useful information at the same time e.g. Supply Voltage and Current draw. You can put in an over-voltage/current shut down routine in the code and help maintain the 'magic smoke' inside! Out in the field it is really easy to mis-connect something (or not) and puff, the smoke is out, HiHi.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 07, 2014, 12:54:10 pm
content: Quote from: VK5RC on February 07, 2014, 12:00:19 pmOdd, I'd be quite surprised if a GHz system noticed a switching converter: there are rarely harmonics beyond 100 or 200MHz (or perhaps more for monolithic converters). If it's a poorly designed system of course (i.e., poor band limiting in any stages), it could be susceptible to lots of sources.Some exceptions include poorly made chips. There's a National chip somewhere that runs its synchronous buck output stage such that the GND side body diode is driven as a step-recovery diode, resulting in a quite reasonable sub-ns blip.Quote from: EEVPiobee on February 07, 2014, 08:39:33 amWhat's the source, how much does power consumption matter? I take it, it's not battery operated? How much do you need at 5V? Just a few mA for the MCU alone, or are there other things attached (say, an LCD with backlight that gobbles a few hundred mA)?Plug-in hardware, with stuff like the latter, I would be fine with a 7805. An LCD backlight is kind of a pain, but a little heatsink on the 7805 and that's plenty. If this is battery powered, you'll probably want to maximize life, meaning using low-power modes in the MCU whenever possible (cuts current consumption from ~10mA flat out, down to perhaps uA if it doesn't need to do much), and a micro/nanopower SMPS chip to furnish the 5V (roughly doubling battery life versus a low-quiescent LDO).Tim