I have an Uno that is programmed with two IR sensor inputs and a single LED output.
My program and wiring work well when the Uno board is powered by the USB port to the computer.
I want to use an external power source to power the Uno.
I attempted to use a standard 9V battery, like the ones that go in a smoke detector, to power the Uno.
The battery becomes extremely hot very quickly. So hot that I need to use protection to remove the battery.
The program does not work, and the board power light does not illuminate when the 9 V battery is used.
What could be the problem?
I have tried other 9V batteries.
It might be a shortcut, perhaps in the connector, or on the Uno board, or perhaps the voltage regulator is broken.
Do you have a multimeter ?
Can you check the board with a magnifier for shortcuts or solder drops or something else ?
A 9V battery is very weak, if you use a strong power supply, you might smoke the Arduino. Find the cause before you apply a voltage to the barrel jack.
Peter_n:
It might be a shortcut, perhaps in the connector,
That's my first thought. Presumably using one of the connectors like in the pic- if so, which? I'd check across the wire ends with an Ohm meter with no battery connected.
Does the battery get hot simply when you have the connector pushed onto the battery (assuming you're using one of those connectors) or when it's connected to the Arduino? If you're not using one of those, are you sure you have the polarity correct?
If you are using one of those like on the left, is it centre-positive?
(That said isn't there polarity protection through the barrel jack in Arduino?- I can't remember)
we are use a connector like the one on the left. It came with the Arduino kit.
I am connecting the battery to what I believe to be the barrel connector on the Uno board. There are two plugs along the side of the board where the reset button is. One plug is where the USB cable is connected. I am plugging the battery into the other plug adjacent to the USB port.
A battery was connected to the connector, but not connected to the Uno board. It has not become hot.
That battery becomes hot when it is connected to the UNO board.
I do not know what center positive means or how to check this.
Centre positive means that the +ve from the battery is to the "inside" of that connector. I think most are, but it's not a total certainty until you check.
Put the connector on the battery and check the voltage at the plug: with the -ve meter lead on the outside and +ve on the inside, you should read a +ve voltage.
And yep the barrel connector is the one that's not the USB, bottom left if you can read the UNO logo the right way up.
I did the test as described and shown in the picture.
Measured +7.10 Volts.
Checked continuity between outside of barrel and negative battery connection. 0 ohms.
Checked continuity between inside of barrel and positive battery connection. 0 Ohms.
Would the problem go away if I powered the bread board from the 3.3V terminal on the UNO?
Presently the bread board is powered from the 5V terminal.
It seems to be a fault on the Arduino board.
If it is an official Arduino board, you can try to return it.
Please remove all wires from the Arduino Uno. To check it, use the Arduino Uno on its own. Did you accidently connect a wire to VIN ? Perhaps you did shortcut VIN to GND ?
Or did you for example apply a negative voltage to VIN ? I guess not, I think you only used the battery and that connector.
To repair the board, you can measure for a shortcut. You need the schematic (it is on the Arduino Uno page) and test the connector, test for shortcut before and after the protection diode, or maybe remove the voltage regulator. That is for an advanced electro-hobbyist.
Connect the lead to the Arduino without the battery. Measure (ohms) across the battery terminals on the connector.
The only way the battery (obviously an alkaline battery) will overheat is if there is a short circuit across it. It clearly has little or nothing to do with the main circuitry of the Arduino and is very unlikely to be the regulator itself. There must be a wiring (solder) short across something; the regulator or one of the capacitors on the board - which should be obvious to inspection. There are only three components connected to "Vin" after the diode so you need to inspect the soldering to them. If any of these were shorted, the diode would become hot also.
You particularly need to inspect the construction of (both sides of) the power connector for looseness and possible distortion when plugged together.
Diode is the black "M7" block between or next to the jack and the two capacitors.
jtlng:
I have an Uno that is programmed with two IR sensor inputs and a single LED output.
My program and wiring work well when the Uno board is powered by the USB port to the computer.
I want to use an external power source to power the Uno.
I attempted to use a standard 9V battery, like the ones that go in a smoke detector, to power the Uno.
The battery becomes extremely hot very quickly. So hot that I need to use protection to remove the battery.
The program does not work, and the board power light does not illuminate when the 9 V battery is used.
What could be the problem?
I have tried other 9V batteries.
Thank you for your assistance and advice.
You connected it backwards, 90% certainty of that. Did you plug your multimeter
leads the right way into the meter when you made that measurement???
In general using a PP3 sized 9V battery is not reliable for powering an Arduino,
its barely enough and any extra loading will likely cause issues.
I plugged in the battery cable to the UNO board without a battery.
I measured across the battery terminal connections with an Ohm meter.
I got infinity or no reading. I do not know if that is the expected reading.
I will inspect the board next for the shortcuts and loose components.
Any experience with powering the UNO using a 120V to USB adapter, then a USB cable to the USB port on the UNO? I was thinking of trying a USB adapter like the ones that charge iPhones.
Sorry for the mistake in my last message.
There are NO wires connected to Vin terminal of the board.
When you mention the use of the 5V power supply, is this a supply that can be connected to the USB port, the Vin terminal, or the barrel plug?
I disconnected all wires from the UNO board.
The battery cable was connected to the UNO board without a battery.
The measured ohms across the battery terminal connection points was infinity.
The most practical way to connect power to the USB port is of course, just to plug it in to a computer - which you have obviously already done - and stated such - to load your sketch. So that will tell you nothing.
Having confirmed with your multimeter that the polarity of your little power cable with the battery attached, is that the centre of the plug is positive, I think you will just have to try plugging it in again. Perhaps best with a cheap non-alkaline battery - while you check the voltages on Vin and Vcc.
Incidentally, 6,06V from a 9V battery = dead battery. But, that is likely due to the overheat condition. Why not post a couple of photos of your Arduino board? Maybe we can see the problem. Also, make sure it is not sitting on anything metallic when the battery is attached.
I would remove the battery and plug it into the barrel connector and see if the + battery terminal is shorted to the - battery terminal when plugged into the barrel connector but not shorted when not plugged in. It
could be a faulty barrel connector shorting plus to minus when plugged in. that would explain the hot battery.
