raspberry pi --> power consumption + battery design

Hi to all.

I need to create one off grid IP video intercom with RSP model 2 B.

In this project i will use

- wifi connection ( usb )

- 12V DC doorlock

- two relay board

- button for triggering call and doorbel

- USB video camera ( 320 x 240 )

The whole system is set but now i want to make the offgrid version with some small solar panel.

Real time scenario:

- call will be triggered on button press

- at the same time, wifi connection should be activated

- camera will start to stream "low" quality stream.

- voip will be started

- automatic disconnect in 10 seconds ( or until next button click )

- trigger DC lock ( 12V, 20ma ) for 5 sec.

- dc lock will be triggered 3 times per day and that's max.

- shortly, I'm planning to use rsp in lowest possible power consumption mode

- daily power consumptions : up to 600mA ?

The idea is to set some small 10W solar panel +rechargeable battery set but i dont know if this should do the job because it's not quite sunny this days :-)

Suggestions ?

Reply to
gm
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It helps when you can keep it powered off until the button is pressed, but of course then have to wait for Linux to be booted. You could try optimizing the boot to have your system functional as fast as possible but it depends on your requirements if it is possible to get it fast enough.

Reply to
Rob

I don't know the exact power usage, but my RPI was constantly rebooting with a 1A wall plug, until i replaced it with a better 2A plug. So, 0.6A might not be enough.

Reply to
edward.ming.lee

During boot it draws considerably more power than once it is up and running!

Reply to
Rob

With the 1A plug, it finishes booting but reboot after several minutes. This is with just hdmi and a USB cellular plug. Perhaps drawing too much current with the cellular modem kicking in.

(OP's) USB camera will probably draw even more current.

Reply to
edward.ming.lee

I build systems using Raspberry Pi boards, ranging from the Pi Zero to the Pi 3.

(1) The low-power mode for the Pi is powered off. The way you put a Pi system in this powered off state is through software (e.g. sudo poweroff from the Linux command line). There is no clean way in the existing Pi hardware to tell if your Pi is powered off. Powering it up via external hardware is easy - ground the Pi reset pin. If you want a hardware indication your Pi system is up and running, you'll need to do that in software such as by using one of the Pi GPIO pins. There is no ACPI or power management hardware in the Pi. It's either running or it's not.

(2) activating and deactivating a WiFi connection on the fly can be exciting (some would say it's a bad thing to do and difficult to do reliably). Most of this excitement comes from Linux WiFi support.

(3) both your USB camera and an external WiFi dongle (assuming you're not using the Pi 3) if connected to the Pi will be powered all the time. The Pi doesn't give you a reliable way to switch power to USB devices on and off. Unless you have a real jones for USB webcams, you'd be better off using a Pi 3 with its built-in WiFi and a Raspberry Pi camera, either the regular one or the Noir with much better low light (and IR) response). That's going to be lower operating power than a Pi plus external WiFi dongle plus external USB webcam. Yes, you can do it on a Pi 2B with USB WiFi and webcam; it all depends on how much development and support pain you're interested in.

(4) you could probably get a stripped down kernel (such as Raspbian Jessie Lite on the Raspberry Pi website) to boot and connect to WiFi in

15 to 20 seconds. In our neighborhood the folks who deliver for Amazon don't tend to hang out on the porch that long (more like drop and run).

(5) Building a UPS for a Pi is actually fairly simple. You can start with the PowerBoost 1000 from Adafruit and one or more LiPo cells (such as quality 18650 cells, or LiPo cells from places such as Adafruit). Feed the PowerBoost 1000 +5 VDC at up to 2A and it will run your Pi and keep the LiPos charged. Sensing LiPo state is an exercise for the reader. If you put the INA219 high side current sensor board (also from Adafruit) between the LiPo and the charger, you can sense Lipo voltage and current (charge or discharge).

(6) The PowerBoost 1000 wants +5 VDC in. You can run your solar panel output to a +5 VDC buck-boost converter, and feed that to the PowerBoost. Pololu Electronics makes some nice buck-boost converters for just this kind of thing. Putting a buck-boost converter in front of the PowerBoost may sound funky, but it's a building block approach that works. It also gives you a system you can power from +3 to around +20 VDC (the limits on the Pololu buck-boost board). You can run the resulting package from a solar panel, car, car battery, crummy wall wart (if it can deliver the current), or other fun power sources.

Have fun and let us know what works and what doesn't!

Reply to
artie

the Pi doesn't support the gpio-poweroff driver?

-Lasse

Reply to
Lasse Langwadt Christensen

PCs can go into hibernate mode where everything is saved to disk and the PC will restore to operation much more quickly. Isn't there anything like this for Linux on the rPi?

BTW, I've cross posted to the rpi group.

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Rick C
Reply to
rickman

That depends entirely on what it is doing. There is nothing magical about boot. It is just a bunch of programs which tend to use the CPU fully. If your app has any code that ends up using the CPU fully you will see periods of the same heavy power demand.

Maybe the OP intended 600 mA to be an average power draw?

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Rick C
Reply to
rickman

On Mon, 9 Jan 2017 17:28:54 -0500, rickman declaimed the following:

Considering how much power is consumed to write to flash memory, and that you'd basically need enough spare flash memory to write the entire RAM contents along with various processor registers (all the GPIO states, for example), I wouldn't hold out much hope

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	Wulfraed                 Dennis Lee Bieber         AF6VN 
    wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/
Reply to
Dennis Lee Bieber

Is physical size the constraint? If not, i would just go for 20W or 30W panels and forget about the efficiency. Price should not be a problem, with average price below $1/W nowadays.

Reply to
edward.ming.lee

What does the power of writing to Flash have to do with anything???

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Rick C
Reply to
rickman

That would have been a poorly designed embedded system (i,e, Windows) in the first place. All *nix (going back to the first ?nix) have separate prog and data spaces. Absolutely no reason to save prog space and data space is usually much smaller.

A little bit more power and time. Yes, insignificant.

Reply to
edward.ming.lee

Don't exclude the possibility that your 1A charger cannot actually supply 1A to the load. You will have to verify this as there is a lot of junk on the market.

Reply to
Rob

The Pi will draw less power when it is doing less (like a PC) but I think there is no real "hybernate" mode from which it can be woken up without fully restarting. That is why I mentioned booting it at the time the button is pressed.

Of course when you have a task for a Pi that does not need a full-fledged OS to be running it would be possible to run a simple OS or even a single program stored on the flash card. However, it looks like the poster requires networking, camera driver, audio streaming etc and it could be a lot of work to code all that on the bare hardware.

Reply to
Rob

I agree with that. It is junk, really. I have a Pi that is "permanently" connected to my home WiFi but when I restart the AP the Pi does not re-connect reliably and I have to restart it as well.

Reply to
Rob

Hibernate is not really a "mode". It is just a matter of shutting the processor down after saving an image of the RAM and other details to mass storage. The idea is that restoring from hibernation is faster than booting from scratch. I know on the PC restore from hibernation is much faster than booting from scratch.

I found mention of OpenELEC which is intended for home entertainment systems and a version for the rPi exists. I read that it boots much faster than raspian.

Here is something else I found. An add-on board that lets the pi power down cleanly and back up automatically. I am sure this can be configured to bring the pi back up with a button push, but this may be more useful when waking up on a timer.

formatting link

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Rick C
Reply to
rickman

If you count the infinite number of PSUs sold on eBay, of which 110% are crap, then the amount of junk on the market is rather large indeed.

I looked on eBay for the minimum priced PSU I thought might actually work with the rPI. I never got through the low end junk that all had the same image of the unit. One device I had for charging my cell phone crapped out and when I took it apart found the regulator circuit was just a transistor... that was it. Not such a great circuit for powering a CPU.

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Rick C
Reply to
rickman

Maybe "suspend" would be a better possibility. It means the processor is stopped and peripherals are turned off but the RAM is powered (and supposedly refreshed). It should be quick to recover from as the "only thing" required is re-powering and re-initializing the peripherals (not easy at all when not foreseen in the drivers...) and the execution can just continue where it was suspended.

However, the Pi does not offer that.

OpenELEC is just a stripped down Linux with Kodi installed. It is in the category "make the Linux start as fast as possible by omitting unused services and doing as much as possible in parallel".

However, the WiFi is really slow to initialize so I don't think this will ever bring down the startup time enough for good user experience on a doorbell (say 3 seconds max).

With wired ethernet, maybe it is possible. But even there it depends on driver details, used switch, is DHCP used and what server, etc.

Reply to
Rob

Then why do you say it would be a "better" possibility? If it doesn't have that feature, it is *not* a possibility.

Yes, that is the point.

Yeah, wifi sucks. But 3 seconds should be adequate. I have a hard time finding my phone or getting to the computer faster than 3 seconds or even 10. How long does it take to get to the door to open it?

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Rick C
Reply to
rickman

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