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Topic: How to Power Arduino Externally ? (Read 9851 times) previous topic - next topic

Akshaysarraf

Sir, I Tried to power my Arduino Externally with a 9V battery... as  adapters mentioned by you are not available in my area.
But Sir, my Board still doesn't start...

As asked by you earlier I measured AC voltage across the battery Ends (Arduino Not Connected), They are -

19 or 20 when Multimeter Range is 750V
19.7 when Multimeter Range is 200V

And DC Voltage across Battery Ends are 9.37 (Arduino Not Connected)

This is close to the ones i was getting through my adapter.

zoomkat

Your old modem power supply should be ok for external power. I consider the arduino board power splitting between the external and USB power supplies as somewhat suspect. I have an old arduino that using an external 12v power supply connected to the barrel jack produced ~8v on the board 5v pin. I had to use a 7805 regulator chip connected between the 12v and the board 5v pin to get the arduino properly externally powered.
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engr_junaid22

contact me i will teach you........ :P

Akshaysarraf

@zoomkat

I guess Arduino Duemilanove already have a  onboard 7805 Voltage Regulator Chip.


UnoDueTre


Your old modem power supply should be ok for external power.

Did you forget that it's an AC power supply giving out 22V with no load?
Even rectifying and smoothing will be very close (if not over) the max input for the Arduino.

UnoDueTre


@zoomkat
I guess Arduino Duemilanove already have a  onboard 7805 Voltage Regulator Chip.


Yes it has, but the more differential voltage it has across it, the quicker it will heat up plus you can't just go feeding it any voltage, it has a limit which is probably around 18V for light loads and dropping down to around 10V for heavy loads.
It's called de-rating.

Akshaysarraf

Ok i get that..

So what do you suggest I must do now ?

As My Arduino isn't starting with a 9V Battery.

UnoDueTre

You say your Arduino starts with USB power but not when you add the extra shields.
So why not power the Arduino with one USB port then get another USB lead, use only the red wire (+5V) and the black wire (GND) and connect the one end to another USB port and use that to power the Ethernet shield you mentioned?

First make sure that your Ethernet shield does run from 5V and not some other voltage like 3.3v, also make sure you separate any pin/s that the Ethernet shield is using to get it's 5V power from the Arduino as now it will be powered from the second USB port.
Lastly be careful as to not short the USB supply.

I still think it's easier to go buy a DC adaptor (9 - 12V) though.

zoomkat



Your old modem power supply should be ok for external power.

Did you forget that it's an AC power supply giving out 22V with no load?
Even rectifying and smoothing will be very close (if not over) the max input for the Arduino.


Your statement does not make much sense considering the below.

http://forum.arduino.cc/index.php?topic=205728.msg1514156#msg1514156
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UnoDueTre


Your statement does not make much sense


Have you forgotten that he also measured the same power supply with the DMM set to AC volts and got a reading of around 22V?
The DMM will give an erroneous reading on DC if one connects it to an AC source and since he got 10.5 V DC and 22V AC which one would you be more inclined to believe?

Let's assume that the PSU is giving out 22V AC, this is then fed to the Arduino where the input series diode will half wave rectify the AC and the puny capacitor after that will attempt to smooth it out but will not do a very good job as it's only a 100uF so the resulting voltage will be a partially smoothed DC with lots of ripple.
A great power supply that will make.

zoomkat

Quote
Have you forgotten that he also measured the same power supply with the DMM set to AC volts and got a reading of around 22V?


The data plate on the power supply is 220vac in and 9vdc out. In the photo his multimeter is on the appropriate settings and he gets an expected reading for a 9v wallwart.  I'll let you ponder the readings when the multimeter is not set appropriately.  ;)
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UnoDueTre

#41
Dec 21, 2013, 04:01 pm Last Edit: Dec 21, 2013, 04:13 pm by UnoDueTre Reason: 1

The data plate on the power supply is 220vac in and 9vdc out.

Really? why don't you have a closer look at the second photo where it says "AC -AC Adaptor".
It also says that it's a 9V 1A 9VA output, when last did you see the term VA being used for DC?

Quote

In the photo his multimeter is on the appropriate settings and he gets an expected reading for a 9v wallwart.  I'll let you ponder the readings when the multimeter is not set appropriately.  ;)

Exactly, it applies both ways.

zoomkat

Quote
Exactly, it applies both ways.


Maybe, maybe not. The D-Link adapter seems to be the adapter in question (the Beetel seems to be straight forward). I found an AC/AC adapter that has 7.5VAC output. Using an almost identical multimeter as the op is using, I checked the adapter output on the multimeter 200 ACV setting and I got 9v. I checked the adapter on the multimeter on the 20 DCV setting and got essentially 0.0v. This type of multimeter  (by design or not) does not seem to output a DC value when connected to a 60hz AC source. The op should be able to perform the same test with the D-Link adapter and confirm it has an AC output. 
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UnoDueTre


Using an almost identical multimeter as the op is using......

Let's assume your meter and the OP's meter are the same, I find it quite strange then that he got a reading of 22V AC.
We can disagree ad nauseam but the fact remains that unless the OP has access to a scope and can post a screen shot, we ain't going to know for certain what that power supply is really giving out.
It could be AC, it could be DC it could even be that it's got a real crappy circuit in it and it gives out DC with loads of AC ripple.

Akshaysarraf

Images of my Output of AC Voltage reading of my BEETEL Power Adapter. Both Images are included having different Multimeter range.


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