40
  • What's the current draw when the Raspi is at idle (min), and at 100% CPU/GPU (max)?
    (With no peripherals/accessories plugged in)

  • What's the minimum and maximum voltage allowed to run the Raspi stably?

19

Look at:

http://www.raspberrypi.org/phpBB3/viewtopic.php?f=63&t=6050&start=50

It shows that power drainage is variable, depending of the connected devices. Tests never reached 700 mA. Max was 515 mA.

I reordered the metrics in the source article by mA drainage:

  • 322mA at 5.09V - at login prompt on Arch, idle CPU, nothing plugged but power (1.64 Watt).
  • 322mA ~ 323mA - only power, no IO, (peaks at 350-390mA when CPU solicited).
  • 335mA - only a couple PS2 keyboard & optical mouse plugged together on one USB port with an adapter (+30mA when mouse in use, +7mA when num lock LED on!)
  • 375mA - ethernet only.
  • 377mA - ethernet and composite video (compared to 375mA without video composite).
  • 386mA - Mouse&KB + ethernet and idle CPU.
  • 389mA - Mouse&KB + composite video + ethernet at idle CPU.
  • 394mA - CPU idle, LXDE/X11 on!, composite video, ethernet, PS2 KB&Mouse together on one USB port.
  • 435mA ~ 465mA - ethernet only, CPU stress test with ethernet only with 'stress --cpu 8 --io 4 --vm 2 --vm-bytes 4M --timeout 20s'.
  • 440mA (peaks @ 480mA) - Mouse&KB + composite video + ethernet with CPU stress.
  • 475mA ~ 515mA - LXDE/X11 on!, composite video, ethernet, PS2 KB&Mouse together on one USB port, mouse in use + CPU stress, LXDE/X11 on.

Mouse & KB: draw 28mA when idle, to 80mA when mouse in use + 7 to 8mA per keyboard LED when on.

  • Hi there! Although you can leave it as a reference, try and sumarise the information in your link as best you can in your answer. This helps to prevent the information being lost if the link ever changes. Thanks! – Jivings Jul 21 '12 at 13:25
8

My experimentation with Raspberry Pi:

Testing environment (big version)

Voltage is generated by this device and measured by this meter.

I started Raspberry Pi with Ethernet and HDMI connected, with usual Raspbian "2014-06-20-wheezy-raspbian.zip" on SD-card. Nothing is connected to USB ports.

Usual mode

I started from 5.15V and decreased the voltage gradually, checking how the device is working (using UART to starts things there).

5.15V 0.43A
     Normal mode, everything works
5.15V 0.37A (no eth)
     With Ethernet cable plugged out
5.15V 0.33A (no eth, no HDMI)
     After /opt/vc/bin/tvservice -o
5.15V 0.39A (no HDMI)
     Without HDMI, but with Ethernet
5.15V 0.47A (cat /dev/mmcblk0 > /dev/null)
     Ethernet and HDMI active + reading SD card
5.14V 0.50A (yes > /dev/null)
     Ethernet and HDMI active, loading CPU
5.03V 0.43A
4.86V 0.43A
4.12V 0.44A
4.12V 0.52A (yes > /dev/null)
     Without USB devices, it works more or less stably even at 4.1 volts.
4.11V 0.38A (no eth)
4.00V 0.43A 
     The last voltage where Ethernet gets available after booting.
3.97V "Disabling IRQ #32"
     After this messages Ethernet and USB disappears
     and power usages drops. `lsusb` shows only one line.
3.85V 0.20A (no eth)
3.87V 0.25A (no eth; yes > /dev/null)
3.83V 0.20A (no eth)
3.82V 0.17A (no eth, no HDMI)
     I've seen no state where HDMI fails while CPU still works.
3.77V 0.16A (long bootloop)
     It reboots after trying to load USB modules or something.
3.73V 0.17A (short bootloop)
     "Uncompressing Linux..." in a loop

Special mode: bypassing linear regulator

Images of Raspberry Pi with shorted pins and voltage display

  1. Ensure the input voltage is less than 3.5V, not 5V;
  2. Ensure no other input 5V voltage sources are present;
  3. Short conveniently placed 5V pin and 3.3V pins together.

I started with 3.39V and checked what works and what fails as I decrease the voltage:

3.39V 0.45A
    Works like usual, although if you want USB you'll 
    need lucky undervolting-friendly devices (or probably a powered hub).
3.39V 0.54A (yes > /dev/null)
3.39V 0.50A (cat /dev/mmcblk0 > /dev/null)
3.25V 0.45A
3.10V 0.45A
3.10V 0.39A (no eth)
2.95V 0.44A
    Probably near the lowest voltage where USB and LAN may still work.
2.85V 0.22A "Disabling IRQ #32"
    LAN goes down.
2.75V 0.22A (no eth)
    Unstable operation.
2.75V 0.31A (no eth; cat /dev/urandom > qqq;)
    Loading CPU: still works...
2.75V 0.18A (short bootloop)
    Writing to SD card (typing "sync" command): reboots and 
    even can't load the Linux kernel back.
2.80V 0.2 A (long bootloop)
    Still can't boot, probably rebooting instead of initializing USB.
2.79V 0.22A (no eth)
    Decreasing voltage after the boot has finished.
2.79V 0.18A (no eth; no HDMI)
    HDMI is turned off explicitly by tvservice -o
2.79V 0.29A (no eth; no HDMI; yes > /dev/null)
2.72V 0.18A (no eth; no HDMI)
    Gradually decreased voltage to this after fully booting.
    Short bootloop on attempt to load CPU with "yes > /dev/null".
2.66V 0.16A (lowest voltage to receive "Uncompressing Linux...")
2.64V 0.10A (no messages to UART, but it attempts to start)
2.56V 0.06A (no messages to UART)

Note that protection fuse is also bypassed in this mode, so the risk of rendering the board nonfunctional is higher in this setup.

  • 2
    If somebody wants, I may do additional tests (for example involving GPU, h264 or over/underclocking). – Vi. Jul 23 '14 at 17:07
  • 1
    This is a great answer, thanks for writing it. It seems that RPi designers were penny wise and pound foolish by using a cheap voltage regulator instead of an LDO (which would allow stable CPU operation down to 3.3V power supply voltage). Half of the PSU-related questions here would never be written then... – Dmitry Grigoryev Mar 3 '17 at 8:55
4

The model B requires 700 mA at 5 V. That's the maximum for the overall board. The A is 300 mA. USB is +/- 5% so 4.75-5.25 V. Since this includes 2 x USB; the board itself is 500 mA.

While USB can be up to 500 mA, a device must request that; otherwise it gets the default 100 mA.

  • Why the downvotes? – Brian Carlton Jul 18 '12 at 16:54
  • idk, accurate answer – Alexander Jul 21 '12 at 2:50
  • 5
    Because it's variable with usage, not constant at 700mA. 700 takes into account 100 for each USB port, and is a maximum safe value. The answer shows no understanding of electronics and is already common knowledge – Alex L Jul 21 '12 at 11:08
4

The RPi Performance wiki page has some sample readings:

  • Booting: 120-400mA (that's 0.6-2W)
  • Idling: 320mA without network, 370mA with (that's 1.6-1.85W)
  • 1080p video playback: 750mA (that's 3.75W)

With the exception of 1080p playback, I took the measurements myself with a lab power supply, so I can verify their accuracy. No USB devices (keyboard/mouse) were connected. Neither was HDMI, but I suspect the HDMI output was still running.

Interestingly my PS/2 keyboard (connected via a USB adapter) was rated at 75mA but only increased the power draw by 10mA.

2

If you don't want to click links, the Raspberry Pi can handle 4.75v to 5.25v.

As for the current draw/power consumption, here are some numbers:

All of these are bare-bone (does not have any peripherals/accessories attached)

*** Fun Fact (Tested on Pi1 B+) ***
Any turned-off Raspberry Pi that's still plugged in: 75 mA

*** Idle ***
Raspberry Pi 2 B:  420mA
Pasberry Ri B+:    230-240mA
Raspberry Pi B:    320-330mA
Raspberry Pi A+:   100-110mA
Raspberry Pi A:    120-140mA
Raspberry Pi Zero: 60-70mA

*** Under Load/Max ***
Raspberry Pi 2 B:  1200mA
Pasberry Ri B+:    330-600mA
Raspberry Pi B:    480-600mA
Raspberry Pi A+:   200-250mA
Raspberry Pi A:    320-400mA
Raspberry Pi Zero: 140 mA

Take note that some of them have a bit of give-or-take.

Backlink

-2

Current:

The model A and B require 300 mA and 700 mA (respectively) maximum for the board on it's own.

Voltage:

The board requires USB power, which is 5v ± 5% - 4.75-5.25 V.

  • The RPi has limited voltage regulation so do not go outside this threshold!
  • Many power supplies advertised for the RPi are actually 5.25v, so that the voltage drop endured during use will balance out with the higher voltage to produce the desired 5v

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