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Topic: questions about powering the arduino (Read 1 time) previous topic - next topic


Nov 17, 2008, 03:29 am Last Edit: Nov 17, 2008, 03:35 am by unsped Reason: 1
i have a need to provide power to chips the arduino is interfacing beyond the 500ma the external connector / voltage regulator can provide.

to do this can i:
1) switch the arduino to external power via jumper (im assuming usb power + external power = bad?)
2) provide the arduino power through the 5v and gnd header?

also what is the max current draw through the usb, ive heard 100ma and ive heard 500ma

i notice lady ada says this about her motor shield:
If you would like to have the Arduino powered off of USB and the motors powered off of a DC power supply, set the Arduino power jumper to USB, plug the DC power supply into the Arduino, and place the jumper on the motor shield. This is a suggested method of powering your motor project

is it ok to have chips powered off one vcc, but getting digital input from the arduino on another vcc? as long as the gnd's are connected?


Nov 17, 2008, 06:38 am Last Edit: Nov 17, 2008, 06:39 am by gnu_linux Reason: 1
The motor shield has its own external power terminal connector, so you can attach a large power supply to those terminals ( 4-6A Power supply ) and then power the arduino using USB or another external PSU and attach a common ground if the shield GND pins are not already connected




Nov 17, 2008, 06:54 am Last Edit: Nov 17, 2008, 06:56 am by unsped Reason: 1
here is what i want to do:


power the shield, and provide external power to the idc connectors. the external power supply will have a higher amperage rating that the voltage regulator on the arduino board (i want about 1amp).

if i connected a 5v regulated power supply to the "EXT" connector on top of the shield. what configuration should the arduino be in? ie. jumper to usb or ext?

i would think ext, but ladyada says to have it jumpered for usb power?? when using an external supply.


There is probably a good reason why ladyada says that, I would use the same configuration for starters :)

If you want to power both boards with 1 power supply you will need to check to see if the +5VDC and GND pins are connected together between the shield and your arduino and verify with a decent meter

I don't have a motor shield to play with so I cannot confirm how it's wired



lets pretend i never mentioned the motor shield lol.

is there anything preventing you from powering the arduino via the 5v and gnd pins on the power header?


Nov 17, 2008, 07:56 pm Last Edit: Nov 17, 2008, 07:59 pm by gnu_linux Reason: 1
Nope, I don't think so

Just remember, you must provide Regulated power at +5VDC!

There are 3 ways to power an arduino:

0. USB power

1. unregulated external power ( 6-12VDC ) using the onboard power jack and setting the PWR jumper to EXT PWR

2. regulated power at +5VDC on the +5V pin - not completely sure what the jumper setting needs to be it depends on your board



Nov 17, 2008, 08:24 pm Last Edit: Nov 17, 2008, 08:24 pm by gnu_linux Reason: 1
Also, some boards, like the BBB have a jumper for +5VDC

The RBBB can take a bigger regulator capable of 1.25A

The BBB Ver C can also take a  bigger regulator

BBB / RBBB are available from Modern Device / Wulfden
http://moderndevice.com http://wulfden.org/TheShoppe/freeduino/index.shtml

The Sanguino uses a 7805 which I believe is capable of 2.2A max http://sanguino.cc/


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