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Is there a way to allow more power to USB Devices powered by the Pi I have a model B+, and I am unable to power my Webcam plugged into the Pi it has a single USB Connection so there's no way to power it from another medium

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    The best bet may be to use a powered usb hub. It's not necessarily the amount of power provided by the pi but the consistency. Given how little power pi's use typically plugging in a device that requires a large(r) amount of power or causes sudden changes in the amount power needed may be too big a change for the pi to handle which could cause crashes or the device to misbehave. Make sure it's all plugged in before powering the pi may help. Its worth checking the power supply you're using for and making sure its providing adequate power and that you aren't getting under voltage warnings. – rohtua Aug 1 at 19:42
  • @rohtua so what you are saying is use a usb hub plug it into the Pi and then plug the webcam into that? – jonathan connery Aug 1 at 19:48
  • Is it a 2014 model B+ or a 2018 model 3B+? On a 3B+ you get 1200mA. The USB2.0 power limit for any device is 500mA, so you can run two compliant devices without any struggle (as long as you've got a 2.5A power supply). Anything beyond 1200mA drawn from all four USB ports needs a powered USB hub. – Dougie Aug 1 at 20:24
  • @DougieI have no idea I got it as a part of a course in a starter kit – jonathan connery Aug 1 at 20:58
  • Yes, webcam into powered hub. Then the Pi does not have to power the cam. – Tomas By Aug 1 at 21:05
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The Pi requires 5V power to run. The power supplies of the Pi have an Amperage rating. ie RPi3 recommends using 3A, which contributes to the power of the Pi, and subsequently any USB devices connected to the Pi's USB ports. They will feed off this USB Power line...

The Pi draws power from this line, and in itself, the more components utilized the more power it will be drawing..

i.e. running Wifi, Bluetooth, Ethernet will all take from this Amperage.

I like to use the analogy of the Water pipes in the house. Voltage is like the diameter size of the pipe, where as Amperage is like the water pressure applied to that pipe. In order to take a proper shower, you need the pipe to be a certain size (Pi:5V), and with enough pressure (Pi:2-3A) coming though, the shower functions properly. When you get more members of the house taking showers at the same time (i.e. more USB devices plugged in), the overall pressure drops. If that pressure drops low enough, it will no longer allow the household guests to properly take their showers. This is where you start to see components fail on the Pi, or the Pi itself crashes.

There are different methods to powering the Pi (and it's power parasite USB peripherals)...

Aside from reserving the Pi's power supply for Pi use alone, You can implement a Powered USB Hub as mentioned. This will have it's own separate power supply, and typically provides anywhere from 3-4 Amps to the USB Hub peripherals alone.

You can certainly plug the Raspberry Pi straight into this hub and use the hub's power to operate the RPi.

Another solution I've tried recently was obtaining a double-ended USB Type-A cable, plug one end into another wall plug USB brick phone charger, and the other end into a spare USB slot on the RPi... This will parallel the Amperage between the two supplies, contributing to the Pi's existing power bus line, adding more amperage.

One side note: You can actually power the RPi this way without using the small micro-USB power port on the Pi, using the dual ended Type A cable, from power brick to the Pi's USB ports: BUT THIS IS NOT RECOMMENDED! As the power is regulated/protected coming in the micro-USB, and the Pi's USB power line is not.

The USB Hub method is a good method, but adds a bulky hub, Power supply to the equation... The dual ended USB Type-A approach at least eliminates the hub part, but doesn't provide extra USB ports, but takes up one on the Pi.

  • any particular powered USB hub you recommend? – jonathan connery Aug 2 at 19:15
  • Personally, I don't recommend buying anything new or online. Go to your local 2nd hand store. There are TONS of knick-knacks / paddy wacks for the cheap. You might find a USB hub somewhere. Look for a fitting 5V power adapter, and the more amps the better. If it's ~1A it might be ok to charge a phone, but for RPi, I don't bother with anything <2A... hub, no less than 3-4A power adapter. If you are near a major city that has a Goodwill, look for designated clearance facilities where you pay by the weight...Tons of old comp stuff, seen lots of hubs, but power supplies are a bonus. Recyle – mrSidX Aug 2 at 21:23

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