Hi guys -- I'm working on a small instrument that uses arduino mini pro - and am producing several of them. I want them to be powered with a usb cable, so you can plug it into your computer, or into a 5v wall outlet. I've got one FTDI chip that I used to program all of them, but it was fairly expensive, so it wouldn't be cost effective to buy one for each mini pro to attach USB cable and power it. My usb wall outlet adapter says 5V on it, and I've read that computer USB output is also 5V, so I'm wondering if it wouldn't be a bad idea to cut a USB cord open, and attach the voltage and ground parts directly to Arduino Mini Pro's VCC and GND pins. Or if it would be necessary to attach to the RAW pin instead to protect the board?? Couldn't find anyone else who'd done this with mini pro 5V -- if you have I'de love to hear about your experience!
Ignore what the supply says and actually measure the output voltage with a multimeter
on both AC and DC. The DC reading ought to be 5.0 +/- 0.1V and the AC reading less than
0.1V. If not then is not a regulated supply and mustn't be connected to Vcc.
Having said that USB supplies ought to always be good regulated 5V, but it costs nothing
to check.
Vraw needs 6.5V or more IIRC correctly to guarantee the on-board regulator has enough
headroom. Something like a 9V wall-wart can conveniently power the DC jack (which feeds
into Vraw via a diode)
ryanvh22:
My usb wall outlet adapter says 5V on it, and I've read that computer USB output is also 5V, so I'm wondering if it wouldn't be a bad idea to cut a USB cord open, and attach the voltage and ground parts directly to Arduino Mini Pro's VCC and GND pins. Or if it would be necessary to attach to the RAW pin instead to protect the board?? Couldn't find anyone else who'd done this with mini pro 5V -- if you have I'de love to hear about your experience!
All supplies with a USB connector have to be regulated 5V supplies. You should be fine if you cut the USB plug off and connect the 5V wire to the Vcc pin of the pro mini (and GND to GND of course).
I do this all the time becaue USB sockets are all over the place. You can connect the gadgets to computers, phone chargers, an AA battery pack with a booster glued to it, whatever...
The RAW pin won't work because it has a regulator on it so you'll lose a bit of voltage if you go that route (which may be fine, the Pro mini will be perfectly happy with less than 5V but I don't know what the rest of your "instrument" needs)
OTOH ... I don't know if you got the power supplies for $1 from a Chinese importer. If you're selling them to other people then measure the output and make sure you get 5V from them.