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mahjongg
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Re: Request for ultra low power pi

Sun Nov 24, 2013 10:26 pm

when I built my own crystal radio, I used an old stainless steel razor blade and the point of an old pencil as the "diode/detector", other "parts" were a plank of wood, some wire from an old door bell transformer and some aluminum foil. In fact the only part I didn't make myself was an old pink piezo earphone. Had to search a long time for a sensitive spot on the razor blade to put the sharpened pencil point on, but I got reception in the end! :mrgreen:

Later I built one with more conventional components (OA91 diode, copper wire around a toilet roll, commercial tuning cap) in a jam jar. A design from a magazine, designed by a "Dr. Blan".

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Re: Request for ultra low power pi

Sun Nov 24, 2013 10:39 pm

vk3pb wrote: The idea I have is a remote controlled boat capable of self steering itself across an ocean and also receiving and sending messages and images.

Solar panels = extra weight + size. The less power I use the smaller I can make the craft.
Take a look at Fish Pi - similar project:

http://www.raspberrypi.org/archives/1479

http://fishpi.org/

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Re: Request for ultra low power pi

Mon Nov 25, 2013 4:46 pm

How about a reptile like a tortoise?
They use very little power. They can go decades without eating.

http://newswatch.nationalgeographic.com ... rs-in-box/
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Re: Request for ultra low power pi

Mon Nov 25, 2013 7:14 pm

solar3000 wrote:How about a reptile like a tortoise?
They use very little power. They can go decades without eating.

http://newswatch.nationalgeographic.com ... rs-in-box/
and (not surprising) they do near to nothing!

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Re: Request for ultra low power pi

Mon Nov 25, 2013 11:20 pm

redhawk wrote:
Why? Think about the crystal sets you used to make when you were a kid. They were able to tune a local AM radio signal and provide enough power to drive a crystal earphone. If the power consumption of a pi could be reduced to these levels then a pi could be run off a simple coil and capacitor and a few diodes. There would be no need for a solar cell.
This is a baseless argument you might as well use a abacus instead of a calculator because it doesn't require batteries.
The Pi's power requirement for the Model A is pretty low as it is but the SD card and the SoC must have 3.3v to function correctly and 5v is required to power USB devices.
I believe you could probably improve power efficiency by replacing the 3.3v linear regulator with a switch mode as long as there is sufficient noise filtering.

Richard S.

"Come on Richard," it's only Pi IN THE SKY
At the moment .The first calculator made was
As big as a house, and cost millions.
Now you can fit them in a watch, or buy
Them in a supermarket for 50p
Time will tell
BoyOh
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Re: Request for ultra low power pi

Tue Nov 26, 2013 1:15 am

vk3pb wrote:Heater

The idea I have is a remote controlled boat capable of self steering itself across an ocean and also receiving and sending messages and images.

Solar panels = extra weight + size. The less power I use the smaller I can make the craft.

cheers Peter
Aha, so, low power, ocean-going. Gotta be wind powered so no shortage of juice for an RPi.
However, digital radio mid atlantic, surely thats going to be satellite. Image uplink from a tiny boat will be the biggest challenge by far.
>)))'><'(((<

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Re: Request for ultra low power pi

Sat Nov 30, 2013 12:51 am

Hi again

Avatar posted

Code: Select all

I'm sure you've considered these, but they're just the questions that sprang to mind when I read this.

How will the boat be powered? Some sort of motor is going to use a lot more energy than the Pi. Maybe you're thinking of wind power?

Power for the steering mechanism? Again, I would guess at higher power consumption than the Pi, though I'm willing to be proved wrong.

Receiving messages may be low power, depending on bandwidth, etc. and assuming a regular transmission schedule - listen for five minutes once a day, for instance, and otherwise keep the receiver powered down.
And assuming the transmitter can be directional and high power.

However transmitting images may be a problem.
The bigger the image, the more data, so either higher data rate or longer transmission time. Either way, more energy
Unlike a balloon, your boat will be at sea level, so after the first few miles you won't be able to see it. Assuming the ocean is going to be the Atlantic, it will be upto 800km away from land, so you'll have to increase either the tx power or the rx sensitivity. Inverse square law and all that!
So it looks like this will eat into your energy budget more than the Pi will.



Thanks for the posts but I have already researched these and other links.

First, I wouldn't go down the road Fishpi has in using electric propulsion. It uses too much energy and there is an issue about reliability. Also the minute you put a motor on a boat you have to get it licensed and it becomes subject to a number of boating regulations. A craft without a motor is not a boat, at least not in Victoria Australia.

You could do it wind powered but again you get into questions of reliability and wind powered sea going objects are classified as yachts and again have their own set of regulations here.

No, the best way to power the craft in my opinion is wave power.

Check out the following two links

https://www.youtube.com/watch?v=rSsZ4tE5VOw
https://www.youtube.com/watch?v=xfJq9nQ_m2A

Liquid Robotics sailed their craft from the US to Australia so the technology works. I like the Norwegian approach however as it is a little simpler to construct.

Power for steering and RPI would be solar although there is probably some way of capturing the wave motion to drive a change in direction for the rudder. By that I mean the wave motion could be captured separately as potential mechanical energy to be selectively released to change the rudder position. Changes to the rudder would be every minute or so so I don't see this as consuming a lot of power.

For communication I would use an Amateur Radio mode called JT-65 which allows for reliable communication (error corrected) of short messages sent over a one minute period. Correct timing for this mode is essential so a GPS (BU-353) is used to ensure the system clock is within 2 seconds of the correct time and also to provide positional information.

I envisage, unlike liquid robotics. my boar having a mast mounted camera. The Pi could then send back an image taken using a number of different radio transmission modes depending on distance and band conditions. For really long distance communication the image data could be broken up into a series of packets of data and then multiple packets of data sent in parrallel on a number of frequencies with a 2.7 khz bandwidth. It would take a long while to still send an image this way but eventually it would get there.

The less power used by the PI and the steering mechanism, the smaller the solar panels can be and thus the smaller the boat can be made.

cheers Peter

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Re: Request for ultra low power pi

Mon Dec 02, 2013 9:45 pm

boyoh wrote: "Come on Richard," it's only Pi IN THE SKY
At the moment .The first calculator made was
As big as a house, and cost millions.
Now you can fit them in a watch, or buy
Them in a supermarket for 50p
Time will tell
BoyOh
yes but those things didn't require breaking any laws of nature, and what you are asking does!

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Re: Request for ultra low power pi

Tue Dec 03, 2013 6:54 pm

mahjongg wrote:yes but those things didn't require breaking any laws of nature, and what you are asking does!
Are you sure?

Pi's power need is in the 2 watt region. There's an MIT project around that seems to get 1W power from existing radio frequencies...

And even the tortoise doesn't sound so ridiculous after you've seen the robot tortoise from a Finnish team, meant to explore ship wrecks. Can't find a link in the blogosphere, though. Funny stuff is always more popular than science.

I've also seen several serious robotic projects that involve ocean crossing robots, driven by wind power or seastreams.

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Re: Request for ultra low power pi

Wed Dec 04, 2013 12:24 am

Yes I know that the model A can be run below 1 watt but I want a reduction in power by a magnitude or more.
So he wants a PI that runs on 100mW or less (and has the same functionality as the current one) let alone works on "potato power" (micro-watts). Its simply not a serious proposition.
If chip manufacturers were able to reduce power use by an 700MHz to 1GHz ARM by an order of magnitude they would have done it by now. But there isn't much hope that better IC processes can result in a tenfold decrease in power consumption. Power consumption in recent history has mainly gone down because of two reasons, lowering the working voltage, and lowering the leaking of "closed" transistors, and for both there isn't much gain to be had anymore, the PI's CPU/GPU already runs on perhaps 1.2 to 1.8V, and with voltages much lower than that transistors will not work (with switching frequencies in the GHz range). The chance that the ARM will use a factor ten less transistors also isn't too great.
Ill buy a factor two lower, but not a factor ten, let alone a factor thousand.

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Re: Request for ultra low power pi

Wed Dec 04, 2013 8:56 am

cyrano wrote:
mahjongg wrote:yes but those things didn't require breaking any laws of nature, and what you are asking does!
Are you sure?

Pi's power need is in the 2 watt region. There's an MIT project around that seems to get 1W power from existing radio frequencies...
"Rectenna" is the key term to search for, but its normally a millionth of a watt from background rf- I doubt they're getting anywhere near 1W without an antenna the size of jodrell bank !

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Re: Request for ultra low power pi

Wed Dec 04, 2013 9:22 am

The answer to this problem may lie in selecting a totally different processor.

I don't have the figures to hand but chips like the STM32 ARMs consume an order of magnitude less power when processing at maximum capacity. However when they have no work to do they can instantly go into a low power mode where they consume less than a milliamp. In that state they will wait for some external stimulus to wake them up and get on with work.

The catch is of course that your control program will have to fit into a hundred K of FLASH memory or so and work in a similar sized RAM area. You will have to give up the luxury of a Linux operating system or perhaps have no OS at all.

I imagine that with some ingenuity and hard work you entire navigation and communication software can fit into such a device. It will spend 99% of it's time asleep and run off batteries long enough to circumnavigate the world!

Clearly this is possible as we navigated man to the moon using computers that were hundreds of times less capable than those STM32s.

As a bonus though such devices have a truck load more I/O possibilities than the Pi.

No idea about the camera. You could carry a Pi and camera that is fired up infrequently or when something interesting happens to take some snaps and then be powered down.
Memory in C++ is a leaky abstraction .

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Re: Request for ultra low power pi

Wed Dec 04, 2013 4:42 pm

Another chip would still use the more or less the same IC production technology, no way a magnitude lower power consumption is possible while it is doing the same work, but yes if its doing nothing, (or much less) it will consume slightly less power.
If it uses far less transistor, (that is, if its a much simpler design), then yes it will use proportionately less current, but that isn't what the OP wants, he wants the same or better performance.

The PI using another CPU is also completely fictitious, but that's another issue.

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Re: Request for ultra low power pi

Wed Dec 04, 2013 5:02 pm

Yes, yes, we all know that.

What I was proposing was a different device, which may well have less transistors, it has no GPU to carry around, it is clocked at a slower rate, it can put itself to sleep almost totally very easily and wake up very quickly when required. Yes my solution includes not computing at full bore all the time which I don't believe is required for the task at hand anyway. The resulting average power consumption will be orders of magnitude less than the Pi.

Now, if such a solution is not acceptable because "it's not a Pi" well. what can we do?

The quest in the title of this thread is for an "ultra low power Pi". There is no such thing, so given the secondary question, the reason for the quest in the first place, we can only suggest alternative solutions.
Memory in C++ is a leaky abstraction .

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Re: Request for ultra low power pi

Wed Dec 04, 2013 7:22 pm

Heater wrote:Yes, yes, we all know that.

What I was proposing was a different device, which may well have less transistors, it has no GPU to carry around, it is clocked at a slower rate, it can put itself to sleep almost totally very easily and wake up very quickly when required. Yes my solution includes not computing at full bore all the time which I don't believe is required for the task at hand anyway. The resulting average power consumption will be orders of magnitude less than the Pi.

Now, if such a solution is not acceptable because "it's not a Pi" well. what can we do?

The quest in the title of this thread is for an "ultra low power Pi". There is no such thing, so given the secondary question, the reason for the quest in the first place, we can only suggest alternative solutions.
yes, there is no such thing (what the OP wanted), in fact the whole thing is absurd.

But obviously if you use a chip containing one tenth as much as the PI's SoC + PoP RAM then the current consumption will decrease as much. especially if you also clock it slower. Such a device might have its uses, but its not "a PI".

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Re: Request for ultra low power pi

Wed Dec 04, 2013 7:55 pm

mikerr wrote:"Rectenna" is the key term to search for, but its normally a millionth of a watt from background rf- I doubt they're getting anywhere near 1W without an antenna the size of jodrell bank !
I'm sorry. Memory failed me. It's not MIT, but Nokia's research center in Cambridge, UK:

http://acre.com/news/article/2013/08/no ... ains-power

It can run indefinitely on standby and charge the battery from power harvested from RF.

Took a while to find. Now let's see if i can find that stuff about the extremely low power ARM processor from... Apple?

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Re: Request for ultra low power pi

Wed Dec 04, 2013 8:24 pm

And this board is comparable to a Pi, a bit more hardware, less speed, pricier at 150 US$, but 0,25 W power consumption. Available now.

http://www.embeddedarm.com/products/boa ... ct=TS-7260

I'm not saying the foundation should develop a very low power Pi, just that it is feasible. In fact, it's what a lot of the others are doing. Battery life is everything, after portability.

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Re: Request for ultra low power pi

Wed Dec 04, 2013 8:40 pm

cyrano wrote:And this board is comparable to a Pi, a bit more hardware, less speed, pricier at 150 US$, but 0,25 W power consumption. Available now.

http://www.embeddedarm.com/products/boa ... ct=TS-7260

I'm not saying the foundation should develop a very low power Pi, just that it is feasible. In fact, it's what a lot of the others are doing. Battery life is everything, after portability.
Not really comparable at all.

No GPU, just a straight slow ARM CPU. 32MB RAM (max 128), No video... It might suit the OP's purpose though.

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Re: Request for ultra low power pi

Wed Dec 04, 2013 9:00 pm

cyrano,
I'm not saying the foundation should develop a very low power Pi, just that it is feasible
You say that whilst holding up as an example a machine that is many times less powerful and feature full than the Pi whilst being many times more expensive. With not that a significant saving in power consumption.

We are not there yet.
Memory in C++ is a leaky abstraction .

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Re: Request for ultra low power pi

Thu Dec 05, 2013 12:28 am

cyrano wrote:
mikerr wrote:"Rectenna" is the key term to search for, but its normally a millionth of a watt from background rf- I doubt they're getting anywhere near 1W without an antenna the size of jodrell bank !
I'm sorry. Memory failed me. It's not MIT, but Nokia's research center in Cambridge, UK:

http://acre.com/news/article/2013/08/no ... ains-power

It can run indefinitely on standby and charge the battery from power harvested from RF.
Thats apparently 5mW (still impressive from rf) but way short of 1W
http://m.fastcompany.com/1292415/forget ... cell-phone

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Re: Request for ultra low power pi

Thu Dec 05, 2013 11:23 am

Years ago, I saw a report about a guy who did something similar.
Since he lived not far from Crystal Palace, he had oodles of free power available, so he put up an aerial, rectified the output, and fed it to his house-lights.
It wasn't very long before he got the knock on his door, with a request that he appear before the local magistrate.

RF power not actually being free - someone has to radiate it - taking it means someone else isn't getting it. Which could annoy them, if there isn't enough left for them to watch the footie, or log on to twitter.

Of course, if you've got a handy street light outside your house, you could gaffer-tape a solar panel to it. Just hope no-one notices it's a bit dark in the steet at night.

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Re: Request for ultra low power pi

Thu Dec 05, 2013 1:49 pm

Unfortunately there's a simple relationship between speed and power. Every single switching operation in a device uses a small amount of charge (Coulombs), so lots of operations inevitably mean more power is used.
If you want really low power try looking at a microprocessor like a PIC. You could probably make a "crystal set clock" run off the radio four signal, but you won't be able to see what the time is!

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Re: Request for ultra low power pi

Thu Dec 05, 2013 5:57 pm

Burngate wrote:Of course, if you've got a handy street light outside your house, you could gaffer-tape a solar panel to it. Just hope no-one notices it's a bit dark in the steet at night.
The results might be disappointing. LPS lamps emit all their light just shy of 600 nm, and crystalline silicon is pretty far off its efficiency peak at that wavelength. You might be able to squeak a watt or so out of a panel.

For really low power, some of the TI MSP430s can be clocked very slow, and can sleep at µA currents between wakeup cycles. I wouldn't expect many MIPs out of them, though.
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Re: Request for ultra low power pi

Sat Dec 07, 2013 3:18 pm

we already have an "ultra low power" (factor ten less power) PI, its called an "Arduino".

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Re: Request for ultra low power pi

Sat Dec 07, 2013 3:41 pm

Well the obvious solution to this is a peltier cell dehumidifying (freeze drying) a turd, while another peltier gets heat from burning said dry turd later to create work, and the excess can run a pi. Twerk that funky by product! :D Ok, don't listen, and just wet flush all the trace minerals off the land, as I see not much falling from the sky.
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