[SGVHAK] Arduino power question

[David Flynn via HAK]

I haven’t done it, but yes, you should be able to power the Arduino from the standby power by connecting it to the 5v directly (needs only about 40ma) and turn the main on with it. A real-time clock with a battery would be a good thing to add too.

Sounds like a fun project.

Dave Flynn
Oxford V.U.E., Inc.
office (626) 256-6557
cell (626) 893-6654
dflynn at oxfordvue.com



> On Dec 15, 2017, at 12:59 PM, Claude Felizardo via HAK <hak at sgvhak.net> wrote:
> 
> Anyone have any experience with powering an Arduino (Uno or Mega) with the 5V standby from an ATX Power supply?
> 
> From what I've read on various websites the Arduino boards are designed to be powered using either the barrel connector which is connected to the onboard voltage regulator which outputs 5v, or the USB connector bypassing the voltage regulator. The output of the voltage regulator is available via the 5v pin on the Arduino board and the power from the barrel connector is available via the Vin pin.  There's some circuitry to disable the power from the USB if Vin is high enough as well as a diode to prevent reverse current flow.
> 
> You can also supply power directly via the Vin pin but it has to be greater than 5v.  You can also bypass the regulator and supply power via the 5v pin but then you have to be careful not to plug anything else into the barrel connector and there is a potential to damage a computer connected via the USB cable if the power to the 5v pin goes above 5v.
> 
> I recently ordered the Power Drive Shield kit from SparkFun which is designed to power an Arduino using  an ATX power supply and provide 6 PWM outputs using MOSFETs which I will use to drive a bunch of LED strings.
> 
> https://www.sparkfun.com/products/10618
> 
> Looking at the schematic on their website and from what I can see on the board, Vin is connected to the 12v rail with a diode to offer some protection. To turn on the power supply, there is a slide switch that pulls the PW_ON line on the ATX connector to ground.
> 
> What I would like to do is rewire the shield to power the Arduino using the ATX 5V standby then allow the Arduino to turn on the ATX power supply when I want to turn on the LEDS.  I've experimented with this to a limited extent but after reading about the different ways to fry an Arduino I'm wondering about the best way to do this.
> 
> I thought about plugging in a dummy plug into the barrel connector on the Arduino board to prevent accidentally plugging in another power supply but what about connecting it to the 12v rail?  Would it be okay to connect the 5V standby from the ATX power supply in to 5V on the Arduino board and the 12V into Vin at the same time? I'm assuming no.
> 
> Another idea was to use a DC-DC buck booster board powered by the 5V standby and bump it up to at least 7 V and then send that to Vin but that just seems like a waste.
> 
> Oh, the reason for the standby power is this is for an exhibit that will be powered possibly 24x7 and I don't necessarily want the ATX fan running all of the time.  Also during development, I'd prefer to not have to disconnect the USB cable every time I want to switch to ATX power.
> 
> Any comments or thoughts?
> 
> Claude
>