Music Maker shield fried when using 12v barrel connect on R3

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sbrown22
 
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Music Maker shield fried when using 12v barrel connect on R3

Post by sbrown22 »

Hello,

I had my Music Maker shield (w. amp) working perfectly on an R3 Uno, powered from my PC USB. However after removing it from the computer and powering the Uno with a wallplug adapater (rated 12v, 1.5A, centre positive) - the shield blew. It now doesn't function and the Uno won't even boot when the shield is connected - however the Uno is fine when the shield is not connected. Any idea what might have happened? I would like to buy another Music Maker shield but I can't afford to blow another one!

Thanks,

Simon

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sbrown22
 
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Re: Music Maker shield fried when using 12v barrel connect o

Post by sbrown22 »

Another bit of info in case it's relevant: i was using a pair of 4ohm 10W speakers - this worked fine with the USB computer power but I wanted to mention in case they are relevant..

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Re: Music Maker shield fried when using 12v barrel connect o

Post by adafruit_support_bill »

You have probably damaged the voltage regulator on your UNO. It may work well enough to power the UNO alone. But it can't provide sufficient power for the MusicMaker & amplifier.

Arduino advertises the UNO as operating from supply voltages as high as 12v. But they don't mention the limitations in doing so.. The linear voltage regulators used on the board become less efficient at higher voltages because they need to literally 'burn off' the excess voltage as heat. With a 12v supply, 60% of the power is turned into waste heat. If you try to power any substantial current loads (such as a music-maker, amplifier and a pair of 4 ohm speakers), you risk overheating the voltage regulator on the UNO.

For best results, you should power you UNO with 5v from the USB. If you need to use an external supply, try to keep it to 9v max.

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sbrown22
 
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Re: Music Maker shield fried when using 12v barrel connect o

Post by sbrown22 »

Ah ok, thank you,that makes sense. I'm going to get a replacement shield, this time without the amp and use an off-board powered speaker.

What would you recommend to power a portable project that uses a Uno and the Music Maker shield? My plan was to use a 12v NiMH battery I had, but it sounds like that would be inefficient. Perhaps a 5v phone battery/power pack that are now readily available would be better (like this: https://www.amazon.co.uk/Posugear-10000 ... 46&sr=8-11 ) and I'll use a separate (also re-chargeable) powered speaker?

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Re: Music Maker shield fried when using 12v barrel connect o

Post by adafruit_support_bill »

I'm going to get a replacement shield, this time without the amp and use an off-board powered speaker.
I doubt that the problem is in the shield. More than likely, it is the voltage regulator on your UNO.
What would you recommend to power a portable project that uses a Uno and the Music Maker shield? My plan was to use a 12v NiMH battery I had, but it sounds like that would be inefficient.
Anything over 5v is just going to be turned into heat. The regulator used on the UNO needs about 2v 'headroom' to efficiently regulate. So a 7.2V NimH pack would be a much better choice than 12v.
Perhaps a 5v phone battery/power pack that are now readily available would be better
Yes. If you connect that via the USB jack it would bypass the on-board regulator entirely.

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diaphone
 
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Re: Music Maker shield fried when using 12v barrel connect o

Post by diaphone »

sbrown22 wrote:the shield blew
Just curious, is your choice of wording here--"blew" rather than "died"--significant, i.e. did some component on the board let its smoke out? I ask because knowing exactly which component failed could give you major insight into the cause of failure. The fact that your Arduino won't even boot with the shield on suggests something on the shield is shorting power to ground. Did you happen to check the voltage on the shield's 5V pin after the failure? If not, you could check that, but by powering just the shield with a 6V supply, not with it connected to the Uno! The Uno still works, you got lucky there, best to keep that shield off it.

These days, a popular way of quickly finding something like a cap that is shorted is to power up the board and look at it with a thermal imaging camera. A non-contact thermometer can also be used to check the prime suspects. Before these tools were commonplace, you could use temperature changing tape, or if you're really brave, a fingertip :-)

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Re: Music Maker shield fried when using 12v barrel connect o

Post by adafruit_support_bill »

The fact that your Arduino won't even boot with the shield on suggests something on the shield is shorting power to ground.
That is one possibility. But the fact that the problem occurred when switching from a 5v supply to a 12v supply makes the blown Arduino regulator much more plausible.

Switching supplies to 12v would be unlikely to cause damage to the MusicMaker which derives all of its power from the 5v rail. It has no exposure at all to the 12v supply.

On the other hand, asking the Arduino's linear regulator to support an Arduino, MusicMaker and and amp driving a pair of 4 ohm speakers while simultaneously burning off 60% of the input power as heat is a likely scenario for an overload. A 'mortally wounded' regulator might still be able to source the 20mA or so needed to run the UNO. But the Music Maker & Amp would need an order of magnitude more power than that.

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Re: Music Maker shield fried when using 12v barrel connect o

Post by diaphone »

adafruit_support_bill wrote:But the fact that the problem occurred when switching from a 5v supply to a 12v supply makes the blown Arduino regulator much more plausible.
Fair point! I was taking the OP's word for it that the shield was dead, but we don't actually know if it has been tested on another USB-powered Arduino to rule this out. Might not hurt to see what's coming out of the 12V adapter either. I had an issue here with a cheapo "12V 1A" switching type adapter from Amazon that turned out to be putting out 18V under load, with a brief spike to 20.8V at turn on. I suspect it is actually an 18V adapter that got mislabeled as 12V.
adafruit_support_bill wrote:Switching supplies to 12v would be unlikely to cause damage to the MusicMaker which derives all of its power from the 5v rail. It has no exposure at all to the 12v supply.
That makes perfect sense. I wasn't ruling out the power supply swap being just a coincidence either, like if between operating this thing from USB vs 12V, something else changed in the setup, like a component or wire bit fell onto the board, or connections to a speaker accidentally being shorted, etc. Or just the failure of a defective component at power-up.

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sbrown22
 
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Re: Music Maker shield fried when using 12v barrel connect o

Post by sbrown22 »

Hello! Thanks everyone for this, it's really helpful.

Ok so I have tested the wall power supply and it's exactly as per spec. I have another brand new Uno and the shield behaves exactly the same on that - the Uno won't boot (it is not even recognised by the computer) with the shield attached. So something has happened to the shield.

Someone else suggested checking for hot components and I did this (admittedly by touch!) And nothing on the shield seems warm. With the shield attached and plugged into the computer the whole thing is just dead - no heat, no leds and not appearing on the PC. Removing the shield brings the Uno straight back to life.

I will have a go at powering the shield standalone and see if I can measure it's voltage. I'm trying to recall what happened when it blew. I don't recall smoke, I think everything just powered up and then it just all went dead and I got that "ugh" feeling when you know something bad is happened!

Obviously I'd love to bring it back to life this weekend and avoid getting a new one... Thanks again for all the suggestions.

Simon

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Re: Music Maker shield fried when using 12v barrel connect o

Post by adafruit_support_bill »

What happens when you power everything via USB?
With a 12v supply, you are probably overloading the UNO voltage regulator.

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sbrown22
 
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Re: Music Maker shield fried when using 12v barrel connect o

Post by sbrown22 »

So via USB the board and shield are totally dead, the board only works now when the shield is not plugged in.

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Re: Music Maker shield fried when using 12v barrel connect o

Post by adafruit_support_bill »

If you post some photos of the front & back of the shield we can see if there are any visible clues.

As you can see in the schematic, the shield circuits have no connection to the VIN pin. So the 12v would not affect anything on the shield directly - unless you have a short circuit somewhere.

Image

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sbrown22
 
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Re: Music Maker shield fried when using 12v barrel connect o

Post by sbrown22 »

Great idea - photos attached in this post and the next. Looking at the back it does look like the rear of the 5v pin and the ground pin are not too happy..
PXL_20220430_120221694.jpg
PXL_20220430_120221694.jpg (867.11 KiB) Viewed 228 times

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sbrown22
 
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Re: Music Maker shield fried when using 12v barrel connect o

Post by sbrown22 »

Photo of the front...
PXL_20220430_120212433.jpg
PXL_20220430_120212433.jpg (798.39 KiB) Viewed 228 times

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Re: Music Maker shield fried when using 12v barrel connect o

Post by adafruit_support_bill »

Hard to tell from a top-down view, but the ground pins look like possible cold-joints. If you can post a close up of those from about 45 degrees to the side, we can get a better idea of the shape of the joint.

What was connected to the 5v and GND breakout holes next to the headers?

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