I've been working on a few arduino projects over the past weeks, and have been powering them using USB, with the intent to change to DC power once they are done.
When I initially used a DC power supply I went for a 10V, 1A one I had lying around and it worked perfectly. Later, I bought some 12V, 1A power supplies to use with future projects, however when I tried to use them with my project, the project stopped behaving as expected, with voltages not being expected values.
The only major difference between the two is that the ground pin on the new supply is plastic (I'm UK) while its metal on my old 10V one, so I'm wondering if the ground is floating or something of that nature?
Any advice regarding this would be great, as finding power supplies with a real ground pin is proving difficult/expensive
As long as the power supply is outputting 12V at a sufficient current then the ground pin in the mains (13A) plug is irrelevant assuming, of course, that any peripherals attached to your Arduino are connected properly to the Arduino GND pin if required
Have you measured the output from the power supply whilst it is powering the Arduino ?
If you are powering "other things" through the Arduino's on-board 5V voltage regulator it may be overheating.
The power lost (converted to heat) with a linear regulator is calculated as the voltage dropped across the regulator X the current through the regulator. So, it will get hotter with 12V than 10V and hotter if you power shields or other circuitry.
The difference between 5V dropped across the regulator and 7V dropped across the regulator is not THAT much so even at 10V you may occasionally run into problems in the summer, etc.
If that's not the problem there may simply be something wrong with the 12V power supply.
The only major difference between the two is that the ground pin on the new supply is plastic (I'm UK) while its metal on my old 10V one
That shouldn't be a problem. Earth ground is normally isolated from the low-voltage DC output (so the Arduino ground is not necessarily connected to earth ground).
If you're powering from USB and using a desktop/tower computer the DC power is probably earth grounded. In most cases that won't make any difference but it could make a difference depending on any additional connected circuitry.
...I'm pretty sure a plastic "ground" would be illegal here in the U.S. But it's just for AC power safety and it's only there in case something goes wrong. A ground is not required at all if the device is "double insulated" and 2-prong (no ground) plugs are more common than 3-prong plugs. All modern power outlets have a ground but there are some 2-hole outputs in older homes.
When I use my 10V, 1A, grounded supply, it behaves as intended, but when I switch to my 12V, 1A, ungrounded supply, the Piezo buzzer is constantly giving a signal input to the trinket (you can tell by the Red LED constantly being lit). I also tried using the USB power supply and the buzzer behaves as expected (though the solenoid can't be driven due to the 12V supply not being connected).
So the take-home message is - don't power an Arduino (UNO, Nano, Pro Mini, Leonardo etc.) by the "Barrel jack" or "Vin" pin.
The on-board regulator is simply not usable for powering anything other than the processor on the board itself - largely because it has virtually no heatsink.
Your plug-pack with the plastic ground pin is double-insulated - as it should be. In fact, the other with the metal pin should be double-insulated also.
If you only need to power the Arduino, use a USB "Phone Charger". If you need to use 10 V or 12 V for your electric bolt, get a "buck converter" to provide the regulated 5 V for the Arduino. Plenty on eBay.
I haven't seen a schematic for the OP's circuit.
I've built literally hundreds of arduino circuits that use 12V for something but I never connect it to the
barreljack.
I'm not so sure any of this is relevant without seeing a schematic of the OP's circuit that stopped working.
Who hasn't been distracted by someone calling your name just before you're abouit to plug a wire in and
then you realize the wire moved so some other hole you shouldn't connect to ?
Seriously, anything is possible . Let's see a schematic.
UKHeliBob:
That is only correct if you try to power peripherals beyond a couple of small LEDs from the on board regulator
Which explains my second paragraph/ sentence.
Paul__B:
The on-board regulator is simply not usable for powering anything other than the processor on the board itself - largely because it has virtually no heatsink.
Paul__B:
The on-board regulator is simply not usable for powering anything other than the processor on the board itself - largely because it has virtually no heatsink.
that is IMHO a bit harsh.
The on-board regulator will surely be able to produce 50 mA @5V from 12v down. That 0,3W will not overheat it. Many I2C chips used as peripherals will require far less than that.
Of course it would be better to provide e.g. 7,5V on the barrel connector, that is enough to run the analog regulator safely and not too much to bring it to dissipate too much in energy.
Iain531:
I've been working on a few arduino projects over the past weeks, and have been powering them using USB, with the intent to change to DC power once they are done.
Why stop powering them through USB.
A 5volt cellphone charger connected to the USB socket is an easy/good way of powering your projects.
As long as you don't try to draw more than ~400mA total from the Arduino.
Leo..
RIN67630:
The on-board regulator will surely be able to produce 50 mA @5V from 12v down.
No for a Nano. It will instantly or eventually fry with 12volt at V-in, even without any current drawn.
Yes/maybe for an Uno/Mega.
An Uno will eventually shut down with more than ~100mA total, depending on duration and ambient temp.
A Mega could maybe sustain 120-150mA.
Why power a 5volt device with 12volt anyway.
12volt on the DC socket with 100mA total from any/all pins will generate (12-0.7-5)*0.15= ~1watt in the 5volt regulator. Enough to raise it's temp by maybe 50C above ambient. Not cool :).
Leo..
RIN67630:
The on-board regulator will surely be able to produce 50 mA @5V from 12v down. That 0,3W will not overheat it. Many I2C chips used as peripherals will require far less than that.
And there is the risk. You add something that takes not too much current.
Wawa:
No for a Nano. It will instantly or eventually fry with 12volt at V-in, even without any current drawn...
Please stop writing bullshit!
The LM117 is rated 0,8W when soldered on a PCB.
"The maximum power dissipation is a function of TJ(max) , RθJA, and TA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(max)–TA)/RθJA. All numbers apply for packages soldered directly into a PCB."
At 12V with 50mA additionally drawn by that perpherals, we will be by 65 mA total * 7V = 0,455W that is far beyond the maximum given is a datasheet.
Additionally the LM117 will not "instantly fry" if overloaded, but brown down to less than 5V.
Wawa:
Why stop powering them through USB.
A 5volt cellphone charger connected to the USB socket is an easy/good way of powering your projects.
As long as you don't try to draw more than ~400mA total from the Arduino.
Leo..
A good reason to power your Nano form Vin at 7-8V is to get a real 5.0 Volt for the ADCs.
maybe when powered from the USB, you get less and nothing stable.
Meanwhile I prefer to use AnalogRef=INTERNAL and use a dividing trimming pot.
RIN67630:
Please stop writing bullshit!
The LM117 is rated 0,8W when soldered on a PCB.
Now that's a bit harsh. I know the theory, but theory and practice is not always the same.
There are several unexplained threads on this forum reporting a Nano's regulator going up in smoke when V-in/raw is connected to 12volt. Never had it myself though.
That 0.8W statement is useless if you don't add the size of the PCB.
RIN67630:
A Nano draws 11mA, not 55.
Last time I measured it I think I saw ~30mA.
Leo..
