I have a project involving a Zero and a Dayton Audio board (KAB-215v2, which is great so far). I saw that there is a 5V pin in one of the headers on the Dayton board, as well as other pins with 3.3V, etc, and I wondered if I could possibly leech power to run the Arduino (I'm using a 24V PSU for the Dayton board that is very much overkill).
Their support was helpful, but didn't know anything about the 5V, how much current it could provide, what kind of regulator IC might be involved, etc., and I couldn't deduce anything from part numbers on the board. So I know that the more reliable thing is just to use a separate PSU for the Arduino, or use the 24V PSU through a step down regulator, etc.
But what I'm wondering is if there is any potential harm in trying it to see how it goes... if I starve the Dayton board or the Arduino for current or voltage, is there anything bad that can happen to either board in the short or long term? Is there a risk that I might burn out a voltage regulator on the Dayton board if I try to vampire too much power? If so, I won't take the risk, but if it's harmless, I'd be curious to know if I could save a component in this setup.
No idea how you will starve a board through a vampire.
If you take more current than the Dayton board was designed for, you may blow a fuse or you may blow some components. The latter will be difficult to repair...
Usb adapters are around for almost nothing. Why not use one of those for your arduino?
Also the arduino may 'inject' a lot of noise in your audio board...
The zero has a Vin pin that produces 3.3v through a regulator, so thats a safe connection.
After that it depends what you intend the arduino to do.
Provided you aren't doint something that would use a lot of current (eg powerful LEDs, motor etc) you should be OK as the zero board uses little power
Yeah I probably will; the idea is just to be able to avoid getting another component involved (cost, e-waste, smaller installed footprint, etc; we'll be making a lot of these so it all kinda adds up). Thanks for the warnings re: the fuse, etc. I wish I knew something about that 5V rail on the Dayton board... I don't want to risk disabling the board so I probably won't be trying this.
Yeah I don't plan to do anything much with the arduino; it's just outputting a sine wave on a couple pins, and reading a rotary encoder on a couple others. And driving one LED through a GPIO. But given build_1971's cautions I think I might skip the attempt.
In which case it makes NO sense to add another power supply. Its a real cludge. If the drayton board couldnt supply a few milliamps why would they have provided a 5V output?
Also you need to be sure the 5V turns off at the same time as the other psu.
I am with johnerrington:
It is very unlikely that the nano will draw too much power. Some measures to prevent noise going into the Dayton would be a good idea (capacitor and choke coil).
So, Dayton doesn't really 'provide' a 5V pin, per se; there is a header on the board marked "Future programming" that isn't for consumer use. There happens to be a 5V pin on it (as well as gnd and RX/TX pair). I do measure 5V on it. I contacted support and asked about it, and their response was that they can't guarantee anything about it (they said they couldn't guarantee that it was even regulated, but surely it's regulated, right?)
Let's say they're using a tiny 5V regulator to provide just enough current for this programming header and a couple other things on the board, and I hang the Arduino off of it and push it over the rated output of the regulator -- is there a such thing as over-drawing current from a voltage regulator and burning it out? Or maybe the voltage drops and things just flake out temporarily and it's harmless?
I'm not trying to be worried over nothing; I just don't know enough to know what I should worry about.
Hmmm... Is there some danger of things being turned on/off not in sync? The Arduino Zero GPIO outputs just go into the line input of the Dayton board...
Basically they tell you that trying is at your own risk.
Can you follow the track from the 5V pin to a three legged component and read some component number from that component? That might give a hint...
It is up to you to take the risk or not...
I tried, but was unable to trace it, and I looked up every component I could read on the board and couldn't track down a regulator. (Edit: I did find a 3.3v regulator but not the 5V)
Yeah that seems like a fine option; the reason I've shied away is mainly ease of assembly; these might be getting put together by people without technical skill and I want to minimize the number of things that can go wrong; in other words, if I have to add a second component for the Arduino, a separate wall wart PSU seems like a simpler solution than a board, but yeah, it's maybe a toss-up overall. It would be nice to have a single plug to plug into the mains.
On that subject -- do you recommend any particular better-quality PSUs? Just, in general? The audio amp is using this, which, though beefier, is probably still "cheap" in the way that the Arduino PSU is (this one).
One issue I have (with this project specifically) is that some of the more serious-looking PSUs I find have open wire screw terminals for the mains (understandably), and these things I'm putting together won't have an insulated/grounded chassis... these will be installed in public places, so I'm not psyched on exposed high voltage wiring (in terms of fire safety, etc). My ideal PSU would have a hardwired mains cable but screw terminals for the low voltage.
