Slight power issue: unplugging headphones resets Pi!

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Slight power issue: unplugging headphones resets Pi!

Post by Cannikin » Thu May 26, 2016 11:49 am

So I've run into an interesting power issue...I've got the Adafruit speaker amp and it's ground wire runs through the headphone contact switch: plugging in headphones removes power from the amp completely so that it's not drawing power at all.

The problem is that when I remove the headphones, and the amp suddenly receives power, that surge that happens seems a little high for the PowerBoost: the Pi resets! I've seen something similar when you plug in a Wifi dongle...I guess the power draw is enough that whatever is supplying power can't quite handle that surge fast enough.

Anyone have any advice for stopping this from happening? Or should I just run the audio channel through the headphone contact switch instead: basically the amp will receive constant power even when not amplifying anything, but will only get an audio signal when headphones aren't plugged in.

Adafruit lists that the current draw when not even driving a speaker as "4mA quiescent and 1uA in shutdown mode" according to Adafruit docs. 4mA is a lot more than 0. :(

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Re: Slight power issue: unplugging headphones resets Pi!

Post by Zeke2040 » Thu May 26, 2016 12:37 pm

Having the same issue but had not researched why. Thank you and interested in alternate solutions as well!

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Re: Slight power issue: unplugging headphones resets Pi!

Post by Cannikin » Thu May 26, 2016 12:49 pm

Zeke2040 wrote:Having the same issue but had not researched why. Thank you and interested in alternate solutions as well!
I would imagine a capacitor or two along the lines that power the Pi would be able to provide a little extra juice to cover that power dip while the amp starts up...but unfortunately my raw electronics knowledge isn't quite to the point where I'd be willing to start dropping capacitors in there and potentially fry my Pi. If I had a couple backups maybe, but right now this is my only one!

[mention]Helder[/mention] or [mention]Popcorn[/mention] maybe can help?

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Re: Slight power issue: unplugging headphones resets Pi!

Post by Helder » Thu May 26, 2016 2:16 pm

Maybe a 10uf cap from power to ground to stabilize the power spike, if the 10uf holds out then maybe lowering the value of the capacitor a bit till you find that sweet spot.
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Re: Slight power issue: unplugging headphones resets Pi!

Post by Cannikin » Thu May 26, 2016 2:50 pm

Helder wrote:Maybe a 10uf cap from power to ground to stabilize the power spike, if the 10uf holds out then maybe lowering the value of the capacitor a bit till you find that sweet spot.
So no need for a diode in there, just a cap between PP1 and PP6 on the back of the Pi?

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Re: Slight power issue: unplugging headphones resets Pi!

Post by Helder » Thu May 26, 2016 5:58 pm

A diode protects against voltage flowing back one way and it also lowers the the actual voltage flowing through it so not sure that's what you want.

I was referring to power on the amp but if that's where the amp connects to then yes.
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Re: Slight power issue: unplugging headphones resets Pi!

Post by Cannikin » Thu May 26, 2016 6:31 pm

Helder wrote:A diode protects against voltage flowing back one way and it also lowers the the actual voltage flowing through it so not sure that's what you want.

I was referring to power on the amp but if that's where the amp connects to then yes.
Oh so you'd actually have it on the amp? I was expecting it to go on the Pi since that's what resets when the voltage drops. Figured the cap would take over and make sure the Pi stays stable until the voltage comes back up post-amp-startup...

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Re: Slight power issue: unplugging headphones resets Pi!

Post by Helder » Thu May 26, 2016 6:32 pm

Yes I guess the pi is where to put it, I just read it above as the amp was kicking the voltage up my mistake but try both ways for the hell of it.
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Re: Slight power issue: unplugging headphones resets Pi!

Post by Zeke2040 » Mon May 30, 2016 7:11 pm

@Cannikin Any luck?

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Re: Slight power issue: unplugging headphones resets Pi!

Post by Cannikin » Mon May 30, 2016 7:51 pm

Zeke2040 wrote:@Cannikin Any luck?
Haven't tried yet but I'll see if I can in there this week...

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