12v dc 1000mA regulated mega power supply
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12v dc 1000mA regulated mega power supply

by dl_evans on Thu May 30, 2013 1:22 am

I bought this power supply

http://www.adafruit.com/products/798

in hopes of powering my Arduino Mega. It works for awhile and then the program freezes and the Mega gets hot.

Some more information about my project:

I have two of these:
http://www.adafruit.com/products/306

One of these:
http://www.adafruit.com/products/823

And one of these:
https://www.sparkfun.com/products/10306

Also connected to the Mega are two NES controller ports so I can plug an NES controller or Zapper Gun into the board as inputs.

I've searched online on Adafruit's forums as well as arduino.cc and Google. The only thing I can find is that the power supply takes 5 - 12v dc or up to 20v at the max.

Is 1000mA too much? Everything works flawlessly connected to USB power.

What exactly is the difference between regulated and unregulated power supplies? Should I use unregulated with the Arduino?

Thanks for any and all help.
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Re: 12v dc 1000mA regulated mega power supply

by adafruit_support_bill on Thu May 30, 2013 6:18 am

The only thing I can find is that the power supply takes 5 - 12v dc or up to 20v at the max.

The processor and other circuitry on your Mega all runs at 5v. There is an on-board regulator that takes your 12v supply and regulates it down to 5v for the processor.

The problem is that the type of regulator used on the Mega is not very efficient.. To get from 12v to 5v, it has to burn off more than half the power as heat. That is not a big deal if you are running the Mega by itself, since the Mega doesn't use a lot of power. But when you start adding a lot of other circuitry, the amount of power that has to be dumped as heat increases as well. At some point, the regulator will overheat and shut itself down.

LED strips are pretty power hungry and they run off 5v too. I would recommend giving them their own supply to ease the burden on your Mega's regulator. This would be a good choice: http://www.adafruit.com/products/276
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Re: 12v dc 1000mA regulated mega power supply

by dl_evans on Thu May 30, 2013 6:50 am

Would I need two of those then? Or if I got the 5v power supply would I be okay since the LEDs run off the 5v rail on the Mega?
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Re: 12v dc 1000mA regulated mega power supply

by adafruit_support_bill on Thu May 30, 2013 7:09 am

Would I need two of those then?

That depends on how hard you are driving your LED strips. With all LEDs on full brightness white, the strip will need close to the full 2A, so 2 would be advisable. We also have a 5v 10A supply which would be enough to power both strips, plus all your other circuitry. http://www.adafruit.com/products/658 Unfortunately, they are out of stock at the moment.

would I be okay since the LEDs run off the 5v rail on the Mega?

Don't connect your leds to the 5v rail on the Mega. To wire these up, connect all of the grounds together (Arduino and both LED strips). But keep the 5v lines separate.
A couple of these adapters will make your wiring a bit easier: http://www.adafruit.com/products/368
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Re: 12v dc 1000mA regulated mega power supply

by dl_evans on Thu May 30, 2013 7:53 am

Ok, so a 5v for the Mega and a 5v for the LEDs.

Can I run the Nintendo controllers off the Mega or should I add those to the LED power supply as well? I have no idea the current draw for them but I can look it up. As long as the LEDs and the controllers are less than 2 amps I should be ok yes?

The power to the LEDs goes to the power supply and then a ground pin on the Mega correct? I think I understand now.
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Re: 12v dc 1000mA regulated mega power supply

by adafruit_support_bill on Thu May 30, 2013 8:10 am

To power the Mega from 5v, you will be bypassing the on-board regulator, so you do not plug it into the normal DC barrel jack. Connect the 5v (regulated) power supply directly to the 5v pin.

You should be able to power everything but the LEDs from the second supply.
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Re: 12v dc 1000mA regulated mega power supply

by dl_evans on Thu May 30, 2013 8:52 am

OK. One power supply just for the LED strips and one for everything else. Wire the Mega power supply to the 5v pin and ground on the Mega.

"Don't connect your leds to the 5v rail on the Mega. To wire these up, connect all of the grounds together (Arduino and both LED strips). But keep the 5v lines separate."

The second power supply power line goes to the LEDs and the negative goes to the Mega with the first power supply and the LED negative also goes to the Mega, correct?

Thanks so much for you help. I'd really hate to fry all of the electronics. :) I'll order two of those power supplies and those connectors you showed me.
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Re: 12v dc 1000mA regulated mega power supply

by adafruit_support_bill on Thu May 30, 2013 9:14 am

Sounds good!
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Re: 12v dc 1000mA regulated mega power supply

by dl_evans on Thu May 30, 2013 9:28 am

Just googling some more to make sure I have this whole thing correct and I found this

5V. This pin outputs a regulated 5V from the regulator on the board. The board can be supplied with power either from the DC power jack (7 - 12V), the USB connector (5V), or the VIN pin of the board (7-12V). Supplying voltage via the 5V or 3.3V pins bypasses the regulator, and can damage your board. We don't advise it.

From http://arduino.cc/en/Main/arduinoBoardMega2560

Should I be worried? Would it hurt to plug it into the barrel jack just to be on the safe side?
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Re: 12v dc 1000mA regulated mega power supply

by adafruit_support_bill on Thu May 30, 2013 9:41 am

Supplying voltage via the 5V or 3.3V pins bypasses the regulator, and can damage your board. We don't advise it.

The only way it would be a problem would be if you were powering it via the DC jack at the same time.

Would it hurt to plug it into the barrel jack just to be on the safe side?

The on-board regulator needs about 2v of 'headroom' to regulate properly. Feeding 5v to the DC jack will get you less than 5v to the processor.

I have done many many projects powered by the 5v pin with no problems at all.
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Re: 12v dc 1000mA regulated mega power supply

by dl_evans on Thu May 30, 2013 10:56 am

Sounds good, Bill. Thanks a heap for your help once again.

The team at Adafruit is nothing short of stellar. Keep it up!
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