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Raspberry Pi Zero – Conserve power and reduce draw to 30mA

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Re: Raspberry Pi Zero – Conserve power and reduce draw to 30mA

#61

Post by geerlingguy »

perlin wrote: post #8

We've actually found that the RPi doesn't draw enough power, specifically to the USB ports. Our peripherals are within the USB spec of a 500ma max pull, but even so we are experiencing sporadic CPU brownouts. The first thought was to double the max_usb_current in /boot/config.txt, but that only lengthened the time between brownouts. We looked into hacks that could increase the current even more, such as this bypass m…

Also, make sure you set the max_usb_current setting to 1 to provide more juice to the ports (see: http://raspberrypi.stackexchange.com/q/27708).

Re: Raspberry Pi Zero – Conserve power and reduce draw to 30mA

#62

Post by geerlingguy »

analog31 wrote: post #6
geerlingguy wrote: post #2

After posting a comparison of power consumption of the Pi Zero vs other Raspberry Pis a couple days ago, I spent another couple hours today testing various methods of reducing power consumption, and was able to get the idle power usage down to about 25-30 mA on the Pi Zero! Thanks to a few suggestions from others on the Raspberry Pi forums, Hacker News, and Reddit, I am able to disable the ACT LED and HDMI, and that…

How much of this applies to the bigger RPi models? Also, can you throttle the clock speed of the microprocessor and further reduce current consumption?

In my testing, underclocking only showed power savings when really stressing the CPU, so it's not as useful to me. I didn't do any GPU-related testing though.

Re: Raspberry Pi Zero – Conserve power and reduce draw to 30mA

#63

Post by StavrosK »

hatsunearu wrote: post #60
StavrosK wrote: post #50

Earlier quoted context omitted.

Wait, how can you break the BBB with a LED? I'm going to use one for a LEGO robot, and I'd like to not fry it :P

Our team has personally blown through three of them through shorting faults. It's our fault, but the BBB is a pretty tender beast.

That's too bad, it's pretty pricy :/ It's no $2 ESP8266, I wouldn't feel very bad shorting that, but at $70, I'm going to be super careful with my BBB.

Re: Raspberry Pi Zero – Conserve power and reduce draw to 30mA

#64

Post by UnoriginalGuy »

danepowell wrote: post #57

To put this in perspective, 30mA costs about $0.15 / year at typical US electric prices. 500mA is $2.50. A tiny draw regardless, but probably a lot more significant if you're running on batteries.

Honestly that 15c/year really puts it into perspective why IoT might make sense. I've always avoided those "smart" light switches and similar because the power draw on them was too high (and it is likely closer to the $3 mark); but if something was drawing 15c/year or similar I doubt I'd care.

PS - I know we aren't going to get WiFi for under a few dollars a year. But physical ye-olde switches are vastly under-estimated I feel. In particular a button to put it into "configuration" mode.

Re: Raspberry Pi Zero – Conserve power and reduce draw to 30mA

#65

Post by geerlingguy »

langarto wrote: post #39
robzyb wrote: post #24

Earlier quoted context omitted.

The Raspberry Pi runs on a fixed 5 volts. At a fixed voltage power will scale linearly with current.

That's a poor excuse for not using the correct terminology or the correct units.

I use Watts on the page where I aggregate my results[1], but since most USB-related projects measure mA (and most battery ratings use mAh), I use the same convention as a default, since 5V can be assumed in all cases.

[1] https://github.com/geerlingguy/raspberry-pi-dramble/wiki/Pow...

Re: Raspberry Pi Zero – Conserve power and reduce draw to 30mA

#66

Post by agumonkey »

moonchrome wrote: post #55
agumonkey wrote: post #37

Earlier quoted context omitted.

I thougth you were thinking of ~dumbphones, but sure enough any smartphone these days is exceptional in most features. Just today I saw a chinese dual core smartphone phone for 34$... The thing is that unless you're already in the know you can't repurpose the board. ps: funny, just an hour ago I was trying to flash an old nexus s with CM*.

On the higher end you have last gen quad core Intel Atom Tablets with Windows 10, 2gb ram, USB, bluetooth, wifi and 8'' touch screen for 80$ [1]. The price of hardware in China is beyond amazing - honestly I could run a laptop off those specs with a slightly larger better screen (assuming I don't need to compile C++ :D) [1] http://www.banggood.com/Cube-iWork8-Ultimate-32GB-Intel-Cher...

And even compiling C++... synthetically this thing is 50% faster than my current laptop. In 2008 this would have been a great machine to program in C++.

Re: Raspberry Pi Zero – Conserve power and reduce draw to 30mA

#67

Post by geerlingguy »

joosters wrote: post #30

Does the PI have any kind of 'deep sleep' support? If you could put the system into something like ACPI S3/S4 sleep state (suspend to RAM) and make it periodically wake up every n seconds, you might be able to save a lot more power. The PI would still be usable for many tasks, e.g. data sampling every few seconds.

I've been looking into this; besides people calling me a 'noob' for not knowing how to do this (but not offering any suggestions as to how it' stone), I haven't seen any way to put the Pi in an official sleep mode, short of buying a Sleepy Pi hat that basically runs a lite Arduino as a hardware power management layer on top of the Pi.

Re: Raspberry Pi Zero – Conserve power and reduce draw to 30mA

#68

Post by dfox »

david-given wrote: post #53
Andrenid wrote: post #28

Earlier quoted context omitted.

For someone like me who has only just started playing with microcontrollers thanks to the Arduino and RasPi and has never touched/played with anything else.. could you give any suggestions/links on what I should consider using for sensors? I have a bunch of "nodes" I need to make, each one has a single sensor (temperature, moisture, light, or distance using a sonic sensor) that will send back to a Raspberry Pi base s…

The MSP430 is renowned for low power and will idle (i.e. suspended waiting for interrupts) at microamps. Architecturally it's a 16 bit Von Neumann architecture at up to 16MHz with a remarkably elegant ISA and extensions to let it address more memory. Most interestingly, some devices have 64kB or 128kB of FRAM --- non-volatile RAM which operates at SRAM speeds! And because it's a Von Neumann architecture you can load…

Another argument for MSP430 as a replacement for arduino and such is that even the smallest devices support reasonable debugger.

As for external devices: at least G-series need external components to generate reset pulse to reliably boot (it mostly works with reset left floating, but whether it reliably works is function of how quickly the power ramps up, I got burned by this on last project).

Re: Raspberry Pi Zero – Conserve power and reduce draw to 30mA

#69

Post by geerlingguy »

teraflop wrote: post #21
markbao wrote: post #12

That's really cool - with those settings, you could run it on a single charge of one of those cheap 20,000 mAh portable batteries for a month.

It might require a bit of hardware hacking to get that to work. I have one of those battery packs, and according to the manual, it will shut off automatically when the output current drops below 50mA.

Same here. I actually can't run it in this configuration, I have to have something plugged in to draw a little more power and keep the battery active. Most of those batteries are designed for 1A+ power draw of a charging tablet or smartphone!

Re: Raspberry Pi Zero – Conserve power and reduce draw to 30mA

#70

Post by weland »

chatman wrote: post #23

Why are you referring to the units of mA for "power", as opposed to current draw? The power consumed would be measured in watts or milliwatts.

When studying power consumption for this type of devices, it's extremely common to measure the current being drawn, rather than to put out values in watts.

For one thing, it's the current that you usually measure in these cases anyway. For the other, power consumption in watts is not what you generally want to know when you design a battery-powered circuit. And, last but not least, it's more useful to have a figure in (m)A than (m)W when batteries are rated in mAh.

It's not correct terminology, mind you, but then neither is that of energy in your energy bill, so I guess this can be forgiven.

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