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Hi, I have searched everywhere but can't find an asnwer for this... so my apologies for this basic question:

What sort of DC power adaptor / supply should I use with the USB Arduino?  What Voltage? or other details... any help would be greatly appreciated as I'm an electronics newbie.
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Daniel
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The Arduino USB and serial boards needs a power adapter with approximately these specs:

- a 9VDC to 12V DC 'wall wart' adapter, rated 500Ma or more
- the connector is a 2.1mm dc power plug,
- the connector need to be 'centre pin positive'

A possible part number in North America:

JAMECO Electronics (California)
Jameco 202201PS  $4.90 USD in quantities of ten or more.

That said, you probably have something lying around that will work. Find a plug that fits the jack, with bare wires. Then, find a 9 or 12V DC 'wall wart' supply, and connect its wires to the connector's wires. The centre pin must connect to the positive  side of the power supply. Reverse polarity is not a huge issue, since the Arduino incorporates a blocking diode to protect against this-- but you might want to remove the ATMEGA chip while gettting things right.



Of course, if I have any of this wrong, Massimo will correct me.. Massimo?
« Last Edit: February 04, 2006, 11:09:20 pm by Daniel » Logged

Jon B
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What 'battery/cell' configuration should I use if I want to maintain the portability? Also if there is a bluetooth version coming how is it powered?

Thanks
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Thanks Daniel, I had searched for this information and couldn't find a clear answer, only snippets.  Being an electronics newbie I really appreciate the help as I start to slowly piece together some electrical understanding. Cheers!  smiley
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Daniel
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Sure, you can use battery power easily: just connect a 9 to 12V battery supply to a connector that fits the Arduino power jack. Be sure to observe the polarity: plus goes to the centre pin.

The regulator on the Arduino board will take a minimum of 9V and a maximum of over 25, but it will run a bit hot the higher you go. Don't go below 9v as things will get unstable. I would say that a 12V gel cell is your best bet, assuming you will want to run some peripherals like servos, LCD's or LEDS.

Massimo will know about the Bluetooth version, I think he is over there in Italy working on it right now, although he might be out for coffee, they have very good coffee in Italy.  Either he or David C. will have the answer.  
« Last Edit: February 05, 2006, 04:40:34 am by Daniel » Logged

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I have a couple of new power related questions:

1. When powering the board with USB, what voltage and mA come out of the pins? what about the power pins, the 5V and 9V are these usable?

2. What are the specs when powering from a DC adaptor? eg. 9V 500mA?

3. I have read somewhere that powering devices, sensor / actuators from the board is not the best way to work because microchips like the ATMEGA8 don't like power fluctuations.  Is this true?

I'm probably asking pretty silly questions, but my electrical knowledge is very limited atm so any help would be appreciated.
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Daniel
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Quote
1. When powering the board with USB, what voltage and ma come out of the pins? what about the power pins, the 5V and 9V are these usable?


The USB board and the serial board use a 78M05 regulator for the 5V supply, which gives potentially (sorry for the bad joke smiley-wink ) 500ma of current at 5V. It will run hot at that current, so it's good to use less current if possible. the Arduino uses perhaps 50-100ma, so it would be safe to draw 200ma from the 5V pin, making total consumption about 300ma. See question #3 for why.  

Quote
2. What are the specs when powering from a DC adaptor? eg. 9V 500mA?

yes that will do the trick.

Quote
3. I have read somewhere that powering devices, sensor / actuators from the board is not the best way to work because microchips like the ATMEGA8 don't like power fluctuations.  Is this true?

Microprocessors like the Atmel and the PIC do not like power fluctuations. If you draw a lot of current quickly  from your regulated supply, you run the risk of a voltage fulctuation that will disrupt the delicate task of computing going on inside the chip.  The answer is to use lots of filter capacitors to satisfy anything that uses current in 'spikes', to limit by design the current drawn from the microcontroller's power supply, and to never never never never use inductive loads like motors and relays that take their current from the regulated 5V supply.  For those, you want a separate supply, preferablt diurectly from the main DC source.  

Quote
I'm probably asking pretty silly questions, but my electrical knowledge is very limited so any help would be appreciated.

Not at all! We're all here to learn and share...  
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I bought a DC power adaptor today, from your advice.

I got a 12V, 0.7A Max with what I believe is the correct diameter connector cos it seemed to fit just fine... but the arduino doesn't do anything.  The power LED comes on, Pin 13 LED (only for a 20ms or so) which I have hooked up also comes on and the TX, RX LEDs also turn on.

The program doesn't run though.  What could be wrong?  I'm pretty sure the power supply is center positive, but I can switch it and test it the other way around if it is safe?

The board works fine, I tested again after with USB power.
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Hello Ian

quick question:
there is a jumper between the power plug and the usb plug (called sv1). Is that jumper connected between pin 1 and 2??
this tells the board where to get the power supply from. between 1 and 2 is the external dc plug while between 2 and 3 is the USB plug.

If your power adapter has a selector for multiple voltages make sure it is set to 9v or more..

let me know

massimo
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Yep I changed the jumper for the DC power closer to the DC input jack, but to no avail.  It's also 12 volts already.
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wow that is weird

try to change the code so that it blinks the led when it starts and download it again.

you can still use the USB cable when arduino is plugged into the external DC power


then reset the board and see if the LED blinks after 5or 6 seconds that the board is on

massimo
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Microprocessors like the Atmel and the PIC do not like power fluctuations. If you draw a lot of current quickly  from your regulated supply, you run the risk of a voltage fulctuation that will disrupt the delicate task of computing going on inside the chip.  The answer is to use lots of filter capacitors to satisfy anything that uses current in 'spikes', to limit by design the current drawn from the microcontroller's power supply, and to never never never never use inductive loads like motors and relays that take their current from the regulated 5V supply.  For those, you want a separate supply, preferablt diurectly from the main DC source.  


I'm a bit confused by the 'never never' use inductive loads like motors.  Does that include steppers?  because I took these instructions:
http://www.arduino.cc/en/Tutorial/StepperUnipolar

and made a simple arduino stepper controller.  Did i Just get lucky on amperages and such?  It works just fine on USB..

Along the same lines of the above comments, I've noticed that my own 9v power supply doesn't seem to finish loading programs when i switch it over.  When I check the voltage on the 9v output on the board, I get 8v or so.  I'm assuming this is because my supply's output is 300mA which isn't sufficient?  (I'm an electro-noob as well, so please correct me)
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Daniel
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yes mabe "never never never" is a bit extreme... If your +5V supply is regulated well enough it may work. In my expereince though, you avoid a lot of hassles by not putting inductive loads like steppers and solenoids on the logic supply! What I should have said is that if you use separate supplies -i.e. one for logic and another supply for messy inductive loads- you can pretty much be sure that the indutive will not interfere with the logic supply. It's one less thing to worry about.

Re the second question, you're probably geting 8V or so at the Vin connection because there is a blocking diode (D1) that drops .7V of the supply voltage. Most "wall wart" supplies aren't goign to be exactly 9V either, as they aren't usually regulated.

D
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I'll start with a stupid question:  If USB provides +5V power, why does the DC power input jack need 9-12 V?  Won't the 78M05 voltage regulator burn most of that up?

Next question: I'd like to get an Arduino running off of batteries (efficiently).  Once I had things working on the Arduino USB, I thought I'd pick up an Arduino Mini (aka the Arduino Stamp) and use it with some sort of switching voltage regulator.

If the Arduino USB typically uses 50-100mA (mentioned in this thread), should I expect the Arduino Mini to be much lower?


Thanks!  This little Arduino has my brain spinning in all sorts of new directions!
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Yeah, i'd love to master the battery problem as well.. I want something that puts out 12v, and enough current to run some other hardware (servos, motors etc) and still be rechargeable.  I've yet to find anything like that...

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