Powering a Raspberry Pi and 5" HDMI/VGA/NTSC + touchscreen +

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michaelmeissner
 
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Powering a Raspberry Pi and 5" HDMI/VGA/NTSC + touchscreen +

Post by michaelmeissner »

I have this Raspberry Pi camera project (putting a pi + camera inside of a Polaroid 95 bellows camera). At the moment, I'm using revision 1.0 of the Rasberry Pi that I got during the initial Pi ordering and the 2.8" PiTFT screen. However, I'm finding the PiTFT screen to be on the slow side, so in today's 12% off sale, I ordered the HDMI 5" display w/touchscreen (https://www.adafruit.com/products/2109) and the 4400ma battery (https://www.adafruit.com/product/1565).

Now, the battery only has one USB port. Do I need to get/make a USB Y-cable to split the power between the two devices, or can I connect the 5v/ground from the Pi, and will it have enough power to power the monitor (i.e. if I have a 1A supply coming into the micro-USB power plug, can I attach a 500mA device directly to the gpio pins without blowing something up)?

In addition, assuming some day I rev up to a B+ model with 4 USB ports, would I be able to power the 5" display through the USB ports (i.e. if I have a 1A power supply to the micro-USB port, can I draw 500mA from the USB port, or do I need to use a GPIO port)?

I've burned out microprocessors and external camera flashes, so I figured I would ask before trying it, and releasing the magic smoke.

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Re: Powering a Raspberry Pi and 5" HDMI/VGA/NTSC + touchscre

Post by adafruit_support_rick »

According to this page, the max current draw on the 5V GPIO pins is USB - 700mA for the Pi (model B) itself. So, with a 1A supply, you can get 300mA from the 5V GPIO
(the B+ uses slightly less power - 650mA).

In any case, you can't get 500mA out of the USB ports. It's limited to 120mA on the Model B. I couldn't find a spec on the B+ USB current, but I don't expect it to be much different.

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michaelmeissner
 
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Re: Powering a Raspberry Pi and 5" HDMI/VGA/NTSC + touchscre

Post by michaelmeissner »

Thanks Rick. I figured as much, so I need to make a Y cable to power both the pi and screen off of a battery with a single USB plug. I was hoping however, that it would be easy to do otherwise.

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Re: Powering a Raspberry Pi and 5" HDMI/VGA/NTSC + touchscre

Post by adafruit_support_rick »

You could use the 5V GPIO pins as well. However, the product page for that battery says it produces up to 1A, which isn't enough for a Pi and the display together.

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michaelmeissner
 
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Re: Powering a Raspberry Pi and 5" HDMI/VGA/NTSC + touchscre

Post by michaelmeissner »

Bummer, it looks like I need to rethink the power options. At least I can use the battery for other projects.

I've measured the Pi + camera + PiTFT + RTC needing about 750mA, which would give me about 4-5 hours of runtime on the battery. The problem is the 2.8" PiTFT is on the slow side, and I hoped to have more resolution and higher speed by going to HDMI.

Ah, well I was tempted by the sale to jump in without doing extensive research.

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Re: Powering a Raspberry Pi and 5" HDMI/VGA/NTSC + touchscre

Post by adafruit_support_rick »

Still worth giving it a try - maybe the battery will put out a little extra.

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michaelmeissner
 
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Re: Powering a Raspberry Pi and 5" HDMI/VGA/NTSC + touchscre

Post by michaelmeissner »

Yep, always worth a shot. And besides I do have other projects that I could use it on that aren't as power hungry. I did want the other battery that is 10000mA capacity, 2A power and 2 USB plugs (https://www.adafruit.com/products/1566), but that was out of stock.

I do have two battery/chargers from Radio Shack that claim to deliver 5v/2A (or 9v/1.5A or 12v/1.3A), so I probably will use those initially, but they are a little bulky.

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