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My research began with the original thread on the Raspi forums: http://www.raspberrypi.org/phpBB3/viewtopic.php?f=63&t=6050&p=291334&hilit=watts+power#p291334
To summarize what we've learned there, the total consumption of a Raspberry Pi is probably not more than:
6 W * 24 h = 144 Wh (I guess that's 518 kJ) (note this is an energy value, not ...
87
Power requirements of the Pi
The Foundation has recommendations for various models which range from 700mA to 3.0A.
These are quite generous, and all models will operate on a decent 1A supply - I can run my Pi3 with WiFi/keyboard/mouse/HDMI from an Apple 5W supply. Extra current may be required by USB peripherals and the recommended supplies make allowance ...
41
It seems that the only concern is that your power supply, if it's not a decent, reliable supply capable of 2A+ of clean output power, might not be able to power the Pi sufficiently, resulting in crashes or frequent rainbows.
See, specifically:
All that max_usb_current=1 does is to set GPIO38 high, which in turn turns on a FET, which connects a second 39K ...
24
Everything for sale is built to a price.
Tha manufacturer wants to make a profit.
There is no need for many USB cables to carry more than a fraction of an amp so they would be built with thin wire. Thin wire is cheaper and lighter than slightly thicker wire. All other things being equal thinner wire has a higher resistance and can carry less current and ...
21
No. The microUSB port is power only -- the other pins are not connected.
You can see that the data pins are not connected on the schematic.
15
These type of enclosed hard drives conform to the USB specification 2.0 specification, even though it's USB 3.0 it must be able to fall-back. USB 3.0 provides lots more power, but since it falls back it must conform to the USB 2.0 500 mA maximum current. The hard drive itself might use more power, but the built-in electronics will detect when to use ...
15
Cables do make a difference once you start to draw hundreds of mA or several A.
You can often tell how much current a cable can carry simply by its looks. Anything thick and stiff is good, thin and overly flexible may cause trouble. Check out these pictures to see what I'm talking about:
VS
Cable length also has a similar effect: Shorter cables are much ...
14
Just noting that the rev 2.0 board no longer has the USB polyfuses, just the input 1.1A polyfuse. So the issues mentioned here should no longer be present in current generation Raspberry Pi boards.
source
12
I am running a Raspberry Pi2 with a 2TB Western Digital element hard disk mounted as root disk (apm set to 254 - effectively disabling standby) via a Y-connector.
Using a USB VA meter (eBay link - LCD USB Charger Current Voltage Detector Tester Monitor Meter For Phone Tablet) I measured (with both the USB HDD and Raspberry Pi2) 5V and about 0.7A.
Measured ...
12
You can use my tool uhubctl, it supports Raspberry Pi models B+, 2B, 3B, 3B+ and 4B - these models have hardware ability to turn USB power off and on.
Use it like this:
Turn off power to all USB ports (must use port 2):
sudo uhubctl -p 2 -a 0
Turn on power to all USB ports (must use port 2):
sudo uhubctl -p 2 -a 1
Turn off power to Wifi+Ethernet (must ...
11
It's possible to power your RPi through your USB hub on two conditions:
the hub does not backfeed: this is easy to test; remove the SD card, connect the RPi's USB port (not micro USB port) to the hub. If the RPi's led doesn't come on the hub doesn't backfeed. If the hub does backfeed you can't use this hub with the RPi.
the power supply of the hub is ...
11
Use a PoE Hat:
Third-party USB-C charging devices can be cheaply wired, potentially destroying connected devices as well as starting fires. A safer alternative is to power your Pi using PoE which beyond reducing these risks, offer additional benefits:
Benefits:
Using a PoE Hat is easy to setup and enables you to:
Emplace a Pi at a much greater distance from ...
10
Good power supply is not enough. USB ports on RaspberryPi are behind polyfuses which limits current that can drawn from it to about 140mA (in practice, it should be even smaller). So no matter how good your power supply is, if your USB device wants more than say 120mA of power, it will fail. Note that USB specification says that enumerated device can take up ...
10
I guess that should not be a problem, for the USB device certainly not a problem. Depending on the USB implementation on the RPi it might not detect your device because it doesn't draw any current. If that is the case you can use a resistor to draw a little current on the USB output. (Put this resistor between the unused 5V and GND outputs on the USB ...
10
there is nothing to handle, as the rpi will not drain more power than it consumes. if you intend to power something hungry from the rpi's usb ports (1.1A max) you may actually need a supply with some reserves. in addition, the board has a polyfuse that should prevent damage to the board on overvoltage conditions.
the rpi wiki has in-depth info on this topic....
10
This qualifies under category circuit rework.
The "best" solution, if the pads are still usable, is to purchase the replacement part and re-attach it. The part is about $1 USD but this does not include shipping Vendor Link (Part Number Found in Schematic)
It is generally a good idea to repair something to its original state. Most things can be repaired if ...
9
It should be possible to run power over this distance, but you should use heavier gauge wire. CAT5 uses 24/26 AWG; a 50' loop of 26AWG would have a resistance of 4Ω; drawing 700mA would give a voltage drop of 2.8V - this would almost certainly cause problems.
8
The Pi should not be powered from it's own USB ports. It's not a safe way of supplying power. The correct way is to use either the micro USB port or the correct GPIO pins.
The hub you have is at fault here - it shouldn't be supplying power upstream along the data feed cable. You may have to take it apart and cut a wire.
Powering the Pi from two places is ...
8
The amp is the maximum current a charger can supply, not the amount drawn by the board. It does not make a difference if the board does not use all 2.1 amps, however it will make a difference if the board draws more than the charger can supply. And the pi can use more than the 700mA, say if you plug in stuff that draws on USB power, therefor more amps are ...
8
There are a few factors to consider here:
The power input to your Pi is probably through a wall adapter or PSU. You should check the rating of the adapter/PSU. If it is in the range of 1.5A to 2A, then your problem is partially solved.
Next in play, is the polyfuse and regulator on board the Pi. As per specifications on Adafruit, the B+ can handle upto 2A ...
8
The Pi 2 should be able to run that HDD directly. However, by default the power to USB is limited to 600 mA, which is not enough (I've had the same issue with an external drive).
To make 1.2 A available -- which is fine if your power supply is up to it -- add the following to /boot/config.txt:
max_usb_current=1
And reboot. Your HDD should now light up ...
8
Popular things like the Raspberry Pi surround themselves with Urban Myths.
One such is the USB cable Myth.
That is not to say there is some grain of truth, there usually is, but people jump to conclusions.
USB2 is specified to supply 500mA max.
USB power is 5V ±0.25V
To remain in spec there should be less than 0.25V drop which corresponds to loop ...
7
As far as I know, you can't.
But by using some very simple electronics you can. The most simple and straight forward option is to use 2 GPIO pins as input (one for each power supply).
Connect both power supplies (besides to their normal connection to actually supply the power) through some resistors (for safety and voltage level adjustment!!) to these GPIO ...
7
From my personal experience, WD Blue HDD (WD10JPVT/WD10JPVX with 0.55A average current) might work more or less reliably (== require about 1 reboot / month) connected directly to RPi without any powered hub.
Your particular HDD requires much higher currents, so it's very unlikely you'll be able to do anything reasonable without an external power.
7
It is acceptable to power the Pi via the GPIO pins, however to comply with the guidelines you should implement a power isolation circuit (as in the B+ or Pi 2 schematic). Direct connection bypasses the overvoltage protection but is acceptable with a well regulated supply (which most mobile chargers aren't).
7
According to the Raspberry Pi FAQ on Power requirements ( which can be found here --> https://www.raspberrypi.org/help/faqs/#powerReqs ):
Maximum draw from USB = 1.2A
Recommended Power Source = 2.5A
Now, according to USB specifications power output for USB works like this:
USB 1.x and 2.0 specifications provide a 5 V supply on a single wire
to ...
7
The spec specifically states that:
A good quality 2.5A power supply can be used if downstream USB peripherals consume less than 500mA in total.
Using a 2.4A power supply with the Pi 4 and a 2.5" HDD is going to be borderline assuming a typical power rating of the 2.5" drive of about 1.8W to 2.7W (see here). From the above statement - after all it really ...
7
Not without voiding your warranty. An RPi4 can deliver a maximum of 1.2 A to all the USB ports together. This is done to protect the USB-C connector which is rated for 3A maximum.
The disks you have in mind consume up to 1 A each.
Without touching to the Pi, you'll need to use a powered USB hub or a bigger-capacity single disk. If you don't care about the ...
6
It should be fine. You should connect the grounds together though.
If the wires are really long, you may have problems with earth loops
6
The best way to power an HDD is trhough a powered hub.
I've bought a 5V 2A power adapter (~9$) and powered both the hub and the Pi as shown in the diagram below:
5V2A ------+--- USB HUB =--- HD (USB Y-cable from HUB to HD)
| |
(power) | | (USB from RPI to HUB)
| |
+----- RPI
2A is enough to power ...
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