Powering a Arduino Yun from computer power supply

Other Hardware General Electronics
1

Hi,

What is the best way of doing the above please?

Please skip to Post #3

My project will involve a relay to switch power to some 12v computer case fans, so I will already have a computer power supply involved using the molex connectors... So was hoping to power the whole project from the computer power supply so it can all run from one plug socket at the mains.

I'm just not sure how to get the micro USB (which I think Yun needs, it is in the post still) from the PSU... Anyone got any ideas please?

I am going to do some more research later when I'm on the computer, just thought I'd see if anyone has any ideas in the meantime please

Appreciate it :slight_smile:

2

Pin out of ATX connector is here:

Here are some of the other connectors too:

I would have a look at a molex connector (like powers a DVD drive), one that is unused.
Red for +5volt and black for 0volt/ground.

Now you should check and recheck voltage during this, DMM and keep the magic smoke where it belongs!

3

Yeah will probably end up being molex I think. I'll use the other spare molexs for the fans

How do you recommend checking the voltage? I don't have a multimeter. I know a molex gives out 12v or 5v (depending on which positive cable is used) but I'm not sure if it is a nice 'steady' 5v or if it will vary

Then I'm guessing you mean literally just chop one end off a USB cable and wire the ground and positive 5v to the corresponding cables from the molex? EDIT: Sorry I just looked it up and find there are some pins that can be used directly on the board providing the 5V is regulated

Also sorry what is DMM? (EDIT: Ahh googled it, as above I don't have a multimeter.) Seems to make sense getting a decent(ish) one though as that is the second time this week it would have come in handy to have one... Off to Amazon to search for one now...

And yes I'd like to keep the magic smoke hidden away safe and sound in the PSU if possible hahaaa

4

Right I think I've decided to go down the route this guy has taken:

Modifying a PSU

I've done what he's done, just temporarily using connector blocks rather than the binding posts for now.

I've got myself a multimeter now and can confirm the following.

I've now got 4 different connections on my PSU:

12.26v
5.12v
3.4v
Ground

What I'd like to know please... Is 5.12v suitable for powering the arduino directly using the Vin pin? With nothing connected to the PSU other than the multimeter, these voltage readings seem very 'steady' (they don't change at all).

Not sure how close to 5v the supply to the arduino must be though? And I'm not sure how to check if this supply from the PSU is actually regulated?

It mentions on the arduino website that the supply MUST be regulated if using the Vin pin as there is no protection from higher voltages when using that pin.

So what do you all think... Am I okay doing this, or would it be best to use a 3 pin wall plug to USB adapter (like a phone charger)?

EDIT: Is it okay / any better to cut up a USB cable and wire one end directly to the PSU 5v connection (5.12v) and plug the micro USB end into the arduino? Instead of using the vin pin. Just wondering as it says this on the website:

There is no built in 5V regulator. If you power your Yún with more than 5V, you will likely damage it. If you are not powering the Yún from the micro-USB connection, you can apply power to the VIN and 5V pins on the board. If using the VIN pin, you cannot provide more than 5V, it will damage your board. It is recommended to power the Yún from the USB connection whenever possible.

Thanks!