I just recently became the owner of a pair of Zumo bots and a pair of Arduino Yun (officially Yún, but future searchers are sure to spell it one way or another). They’re great little bots - I had the pair running around the house within minutes, though using Arduino Uno’s and not the Yun.
That’s because the Yun is quite clever aside from one glaring detail - it requires 5V and has no built in voltage regulator.
Is it safe to say that using the Yun on the Zumo shield without adding a regulator is bad idea? The Zumo user guide says that it outputs 7.45V to power an Arduino - is this accurate?
Maybe the answer to this question will help my problem go away: is there a way to power just the Arduino and have the Zumo shield and motors work? The Yun has a regulator on its mini USB connector, and I have a bunch of those “iPhone battery backup” bricks that basically are USB rechargeable regulated 5v out lipo packs. If I could plug that into the Yun and fully power the Zumo, that’d work.
I haven’t used a Yun, and I’m pretty new to the Zumo as well. From what I can tell, the Zumo uses the 5v and 3.3v regulators on a normal arduino (uno/leo) to power some of it’s components. That said, I’d GUESS that you could probably just cut the ‘VIN’ pin on the Zumo shield (or wrap it in electrical tape/coat it with nail polish), and power the Yun via the USB port. The Yun would get it’s 5v feed, the grounds would all be connected between the shield and the yun, and the zumo would get a 5v and a 3.3v feed.
But, this is just a rather uneducated guess, and the zumo and the yun are both pretty expensive so I’m guessing it’s not something you really want to chance!
It is not safe to use an Arduino Yun with a Zumo without an additional voltage regulator. Like you mentioned, the Yun does not have any kind of regulator on its power input and is only meant to be used at 5V. Cutting the VIN trace on the Zumo shield and powering the Yun separately might work.
I came up with a decent solution. Instead of standard headers I mounted extended headers. The headers populated the holes for the normal Arduino footprint and the holes just outside of the footprint. This allows me to use the Arduino pins when one is mounted on the Zumo shield. The taller headers also make it possible for the Yun’s Ethernet and USB connectors to fit without touching the shield.
For the voltage, I simply cut the headers for the VIN pin right above the board (giving me access to the holes, and right below where they enter the Arduino. I left the plastic cube that holds the pins in place, leaving a bit of room to be able to solder a wire below them. Even though the new VIN pins are “floating”, they remain sturdy since they’re connected to the other neighboring pins.
I then made a simple voltage regulator circuit on a tiny perfboard using a L7805 regulator, a 10uF cap on the input and 1uF cap on the output. Now, instead of having the VIN go directly to the Arduino, it goes to the regulator’s input. The regulator’s ground is wired back to the Zumo shield common ground, and the regulator’s output goes back to the “floating” pin, supplying the Yun with 5V.
It’s a clean setup, and allows me to use any other Arduino (assuming it accepts 5V).
I’ll be doing this again on my second Yun and will take some photos. I’ll probably figure out a way to make the regulator portion easily removable as well.
I am glad you were able to figure out a good way to use the Arduino Yun with the Zumo shield. Thanks for sharing your solution. I would love to see pictures or video of your Zumo with the Yun.
Well, a bit of not so great news. After testing a pair of Zumos + Yuns using the L7805 regulator, it was clear that it’s not an ideal solution. The L7805 gets way too hot. This was discovered the hard way when one of my kids picked up the bot and touched the heat sink on the L7805. It was hot enough to be dangerous.
So, for now, my Zumos are running on plain old Unos. It’s a shame, really. The Yun is packed full of great stuff - ethernet, wifi, a real linux OS, but adding a 5V regulator was just too much.
My new plan is to try to see if I can power the Zumo with an external 5V regulated source. With that in mind, is there a reason that the Zumo shield puts out 7.45v on its 5V pin when powered by internal batteries? Is it possible to modify the shield so that it puts out 5V (like, swapping out the existing regulator)?
I was about to post asking you about the heat dissipated and I, sadly, saw your reply.
During the past days I spent some time in search of information about 5V regulators and I was planning to build a shield to take the 7.45V from the zumo shield (from a side soldered VIN pin) and give back 5V to the Yun using your circuit, but now you’ve confirmed my dubts.
I’d like to ask you how many extra device (reflectance sensor, distance sensors, etc.) are powered by the Yun in your setup, or if you have an idea about the current drown by the Yun and other devices.
Now I’m searching info about swithing power regulators (like this eleccircuit.com/simple-5v-1a … lm2575-50/) to try to understand if they are a better choice to power up the Yun.
I can measure the current draw a bit later. I’ve been using the RC example in addition to data logging with the magnetometer and reflectance sensor array (the one that comes with the fully assembled bot).
So basically: standard motor stuff + mag sensor + RC receiver + reflectance sensors + Yun.
The Yun, I’ve heard, isn’t very power hungry. But it must be more than just an Uno since in addition to running Arduino stuff, it’s running a Linux system with WiFi (which I was using to post mag data to a website).
I think that it’s likely that the regulator I used just isn’t that good. I have some very small micro controllers with regulators that can accept between 3v to 30v that don’t seem to get hot. I’ve considered, for example, using a Digispark just for it’s regulator. I’d pass the 7.45V to 5V pin, and use its VIN to power the Yun. If that works at all then I’d guess that some of the regulators that Pololu sells would work well - certainly better than the L7805 from RadioShack.
I forgot to mention that I might also trying using an external BEC as well. They can usually handle a lot of current (I don’t have it in front of me, but I’m guessing at least 2A to 3A). Pololu carries one that steps anything up to 23V down to 5V and can handle 3A. Hobbyking also has tons of them.
The Zumo shield should only be outputting 7.45V on the VIN pin, and not on the 5V pin. The Zumo shield also does not have a 5V regulator; the 5V pin directly takes power from the regulated 5V pin that is on most Arduinos. If you still want to try adding a regulator, you might consider our D15V70F5S3 and D15V35F5S3 switching step-down voltage regulators.
