Raspberrypi and the TS2012

[guyomne]

I'm trying to convert my Rpi as dlna radio.

Up to now, I pluged a alamode (http://wyolum.com/projects/alamode/) to the Rpi so that I can decode button/plug a Xbee shield. So, I have the Rpi that do all the software and the alamode all the "hardware" both tall with serial. This works without problem and it was just to describe the full project.

As the sound was quite weak, I bought a TS2012 to boost it. It draws its power from the Rpi/alamode. But when the sound is too sharp or too powerfull, the TS2012 drawn to much and powers off the Rpi. So currently I feed the Rpi with a 1A and the the Alamode with 1A but still I can not benefit fully from the audio Amp.

[adafruit_support_mike]

It sounds like you're running into a limit that's built into the RasPi.

The power system on the PCB is fairly limited. Any power that enters through the mini-USB port immediately flows through a polyfuse that's guaranteed to trip if more than 1.1A flows through it. The RasPi itself uses about 300mA when it isn't doing anything special, and up to 780mA when the microprocessor is working hard. That only leaves you about 250mA of current to play with.

On top of that, a RasPi's output pins can only supply about 16mA of current individually, and the whole GPIO bus is limited to about 55mA. There just isn't enough current on the board to power a 1A external device.

You can bypass the polyfuse by connecting your 5v supply to the 5v pin in the GPIO header, but when you do, you have to make sure your supply is at least as smooth and well-regulated as a straight USB port.

[guyomne]

Thanks you for such a great answer !

So I'm looking how to solve that power issue. I found a blog post about a CNC based on the Rpi/Alamode. They supply the Rpi and alamode with a Meanwell P/N NES-50-5 so 5V and 10A. Sadly they does not decribe how they did so.

I know that Adafruit does not supply Alamode but do you have any idea how that possible ? They just plug every on the NES-50-5 and the Rpi draws 1A and the Alamode up to 10 A?

Thank a lot for the help anyway !!

[adafruit_support_mike]

Looking at the specs, I think it's safe to say the Meanwell power supply lives at the opposite end of the scale from the RasPi's power system. It's a thoroughly engineered PSU whose specified output and ripple figure is 80mV at 20MHz.

You should be able to connect it directly to the 5v pin of the RasPi's GPIO header. That bypasses the RasPi's input protection polyfuse, and I usually give warnings when people consider that, but that specific PSU has far better specs than the average randomly-selected wall wart.

Send the folks at Meanwell a note and ask for their suggestions. Explain what you want to do, mention that the RasPi has minimal onboard regulation, and ask if they'd suggest anything like a BFC (http://www.adafruit.com/products/1589) for additional spike protection.

[guyomne]

Thanks a lot for you response, I will do so.

Adafruit forum is really helpful