Batteries and typical power consumtion?

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JustSomeGuyTN
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Batteries and typical power consumtion?

Post by JustSomeGuyTN » Wed May 01, 2019 6:23 pm

Is there any documentation yet on typical power consumption? Specifically what I am looking at is recording 3D to a USB thumb drive on the StereoPi for 8 hours. There will potentially be some bluetooth transmission because I want to control the StereoPi with an Android app on my phone. I will have to do my own app rather than the SLP because I want to add an e-ink panel on the GPIO of the StereoPi.

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Realizator
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Re: Batteries and typical power consumtion?

Post by Realizator » Wed May 01, 2019 7:00 pm

JustSomeGuyTN wrote:
Wed May 01, 2019 6:23 pm
Is there any documentation yet on typical power consumption? Specifically what I am looking at is recording 3D to a USB thumb drive on the StereoPi for 8 hours. There will potentially be some bluetooth transmission because I want to control the StereoPi with an Android app on my phone. I will have to do my own app rather than the SLP because I want to add an e-ink panel on the GPIO of the StereoPi.
We conducted power consumption experiment.

Setup 1:
SterepoPi
CM3+ Lite
MicroSD
2 x Waveshare wideangle cameras
Connection: Ethernet
Settings: 1280x720 at 3MBit with 30 FPS

While livestreaming stereoscopic video and recording to MicroSD, all system consumes 0,7A (at 5V), using our SLP Raspbian image.

Setup 2:
All from Setup 1 + WiFi dongle Alfa Awus 036NEH (1 Watt!)
Systems consumes 0,9 A (at 5V) under the same conditions.


Notice
This is our results for described setup and load. Raspberry Pi recommends to use power source, able to provide at least 2,4A (@ 5V). If you will use other operating mode (like 3D games with GPU load, etc.), your power consumption may be different. We will be pleased if you will share your results with us!
Eugene a.k.a. Realizator

davidheiserca
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Joined: Sun Sep 22, 2019 7:07 pm

Minimum power requirement

Post by davidheiserca » Sun Sep 22, 2019 7:43 pm

I want to get a light weight power bank for a portable StereoPi camera to attach to a small quadcopter.

Several small 1A units are available. Would it harm the StereoPi to connect it to a 1A battery?

Can anyone suggest a good power bank for this purpose?

stereomaton
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Location: France

Re: Batteries and typical power consumtion?

Post by stereomaton » Sun Sep 22, 2019 9:04 pm

The amperage is what the boards (processor, cameras & co) will try to get from the power source. It can be almost 0 if the components do not consume and grow when you compute (get video frames, encode video, write to the SD, and do on).
If your power source can feed it (its rating is superior), all is fine.
Note that, on the other hand, the voltage is most of the time a limited range to respect (here around 5V).

If your source cannot feed the requested current (amperage), the usual effect is a drop in its voltage.
When small and furtive, the drop might be small enough to stay in the needed range and it is fine.
However, if there is a big consumption your battery is not able to handle, it will drop under the range and then strange things can happen. It is very unlikely that it would destroy the components but data may be corrupted. On some systems, this triggers an emergency halt of the processor (I do not know it the raspberry module has that, it very probably has) to avoid false results in computations. However if such interruption occurs during a writing on the SD, the written data can be corrupted but it can perhaps be partially recovered on PC. Whatever, after a reflash of the SD and correct power input, all restart fresh and normal (and it can even recover without intervention if the corruption is not too bad).

With the numbers provided by Realizator, if you do not use wifi dongle, do not stream the video and only record it on the SD card, you should be perfectly fine with the 5V/1A battery pack if it does not go out of charge.
When I worked on a quadcopter several years ago, we had BEC (Battery Eliminator Circuit) which allowed to have 5V auxiliary outputs with quite high ratings. It was far before the wide availability of the commercial drones so I have no idea if such 5V outputs are still available. If they are, you can possibly use it to gain the weight of an additional battery.
Stereophotographer and hacker
StereoPi Standard Edition + CM3Lite module

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Realizator
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Re: Batteries and typical power consumtion?

Post by Realizator » Mon Sep 23, 2019 7:47 am

Stereomaton, thank you for detailed answer!
BEC is the first thing I suggested. It is the best option for DIY drones, but on mass-produced drones (like Mavic of Phantom) it might be not available and hidden deep inside the case.
As for 1A power bank, you need to test it before installation. There are lot of cheap crappy powerbanks, which actually can not provide you with 1A declared. So try to run "on the table" experiment.
Eugene a.k.a. Realizator

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