powering an Arduino through the Vin pin? - Page 1
Forum section: electronics / general

author: dentaku
author_rank: Frequent Contributor
timestamp: November 09, 2015, 02:05:19 am
content: I have an Arduino UNO with a dead USB/Serial chip so I program it using a little USB/TTL device that has a 3.3V and 5V pin on it.like this onehttp://www.geekfactory.mx/wp-content/uploads/2013/06/converdidor_usb_ttl_rs232_pl_2303hx_01.jpgCan I use that 5V output to power the Arduino through the Vin pin and bypas the 5V regulator on the UNO?Right now I'm powering the UNO with 9V into the barrel jack and I'm powering an EasyDriver and stepper motor with a 16V supply PLUS I have the USB/TTL device plugged into a USB and it's a mess of wires. If I can power the UNO through the Vin pin it would make one less wire cluttering things up.

author: Richard Crowley
author_rank: Super Contributor
timestamp: November 09, 2015, 02:44:22 am
content: The question is whether your USB converter gadget can provide enough current to power your Uno.How much current is your Uno (and whatever else is connected) draw? This can be measured with a DMM.How much current can your USB converter gadget supply? Do they publish a spec?If not, do you have the schematic diagram? Does the +5V power simply "pass-thru"?Is the EasyDriver being powered (5V) from the Uno?

author: sleemanj
author_rank: Super Contributor
timestamp: November 09, 2015, 04:09:38 am
content: Quote from: dentaku on November 09, 2015, 02:05:19 amThe short answer is yes, almost certainly, at 5v.The long answer is that the 5v output is almost certainly just passed through from the USB.The 3v3 output however is almost certainly a very low current regulator integrated into the USB-UART IC and not capable of much.

author: obiwanjacobi
author_rank: Super Contributor
timestamp: November 09, 2015, 06:42:21 am
content: I hear a lot of guess-words

author: sleemanj
author_rank: Super Contributor
timestamp: November 09, 2015, 07:18:00 am
content: Quote from: obiwanjacobi on November 09, 2015, 06:42:21 amYeah, we know what the UNO looks like, it's his USB-UART connector we don't.

author: westfw
author_rank: Super Contributor
timestamp: November 09, 2015, 08:22:32 am
content: QuoteVin on Arduino is "before" the 5V regulator. To power with an already-regulated 5V source, connect it to the "+5V" pin.

author: Kalvin
author_rank: Super Contributor
timestamp: November 09, 2015, 08:27:14 am
content: New Uno costs about $5 from eBay.

author: sleemanj
author_rank: Super Contributor
timestamp: November 09, 2015, 08:52:25 am
content: Quote from: westfw on November 09, 2015, 08:22:32 amOh yes, quite right you are. Have also seen the direct power input (output depending on your viewpoint) as Vcc or Vraw depending on the particularly chinese knock-off of the day.

author: dentaku
author_rank: Frequent Contributor
timestamp: November 09, 2015, 04:21:29 pm
content: Quote from: westfw on November 09, 2015, 08:22:32 amAha! I was wondering about that.Also, This is the exact device I'm using.http://www.dipmicro.com/store/PL2303HX-MODI just checked with my meter and it's a direct connection from pin 1 on the USB and the 5V output pin so that's good.

author: dentaku
author_rank: Frequent Contributor
timestamp: November 09, 2015, 09:30:09 pm
content: I've been reading more about this and here's the official word about this.- Vin. The input voltage to the Uno board when it's using an external power source (as opposed to 5 volts from the USB connection or other regulated power source). You can supply voltage through this pin, or, if supplying voltage via the power jack, access it through this pin.-5V.This pin outputs a regulated 5V from the regulator on the board. The board can be supplied with power either from the DC power jack (7 - 12V), the USB connector (5V), or the VIN pin of the board (7-12V). Supplying voltage via the 5V or 3.3V pins bypasses the regulator, and can damage your board. We don't advise it.For anyone else wondering about this, it was explained quite well here.http://electronics.stackexchange.com/questions/65576/arduino-uno-r3-directly-supply-regulated-5v-to-5v-pin

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 14, 2015, 05:59:18 am
content: That's just to cover the case of someone using a poorly regulated "5V" power supply like some old wall wart they found in the drawer.