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I'm making an authonomous robot (like Phoenix probe but very simple and cheap and made for Earth, no moving parts, just sensors). It controlled by Raspberry Pi and will live in forest shadowed by trees. So, I guess I can't use the solar panel in this case (or that panel will be extremely huge).

Also, I don't want that my robot sleep during charging. Ideally, if it can record data 24/7.

I need at least 10W output for RPi powering and some additional power for battery charging (for situations when generator can't produce energy).

Which types of generators are available that can produce needed power, silent and compact enough (I don't want to bring petrol generator to forest). Also, I don't want to go to forest often to replace discharged batteries.

And I don't have any rivers and don't have powerful wind here.

I want to record video and audio (when motion is detected), and ideally run OpenCV and TFLite to recognize birds and animals.

Is it possible? Can I found a way to power it for at least a week without human interaction?

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    \$\begingroup\$ If it has no moving parts, it could maybe be redesigned to use 10x to 1000x less power. Then you would have no issue finding a big enough battery, or even running off a small solar panel. \$\endgroup\$
    – DamienD
    Sep 5, 2022 at 14:48
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    \$\begingroup\$ A Raspberry Pi is a poor choice for a low-power application. The Texas Instruments MSP430 series of MCUs is designed for low-power applications, there are also others. \$\endgroup\$
    – Mattman944
    Sep 5, 2022 at 15:06
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    \$\begingroup\$ A "robot" with "no moving parts, just sensors" is not a robot... It's a sensor. \$\endgroup\$
    – brhans
    Sep 5, 2022 at 15:07
  • \$\begingroup\$ @brhans It's a science station, ok? Like devices on Mars and Venus. \$\endgroup\$
    – Robotex
    Sep 5, 2022 at 15:35
  • \$\begingroup\$ Is it possible that you can take a solar panel out to the forest and measure how much power you actually do get? \$\endgroup\$
    – user253751
    Sep 5, 2022 at 15:38

2 Answers 2

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Redesign it with a low-power bare-metal microcontroller. Many microcontrollers use something like 0.05W when active, and 0.00001W when in deep-sleep mode. Then, you can easily power the device with a solar panel even though limited light is available.

Your code needs to conserve power by using the microcontroller's sleep mode as much as possible. For example, if you only want to measure every 5 seconds, the microcontroller should sleep for 4.9 seconds and then use 0.1 seconds to perform the measurement.

I suspect that downgrading to a microcontroller will give you plenty of power even if you leave it running all the time, so you won't need to be too fussy about sleeping.

You indicated you need to do some video processing which really does need the computing power of the Raspberry Pi. Your main goal is still to decrease power consumption as much as possible, but you can't do it by just downgrading the computer. You need the Pi to sleep as much as possible. If it's running Linux, this is probably quite difficult, because Linux will take several seconds to go to sleep and to wake up, unlike a microcontroller that takes a few milliseconds, and this severely limits your ability to make it sleep much.

You could try underclocking and undervolting it.

You could try using a low-powered device (such as a PIR sensor or Arducam) to watch for movement and wake up the Pi when it detects some.

You could do the video processing in batches - with a low-power device recording video all the time (or when there's movement), and a high-power device running every now and again to process the recorded data.

In fact, do you really need to do the processing in the field at all? What if you bring the memory card back home after a week, and then do the video processing on your own computer? If you choose that route, you may find it better to use an off-the-shelf motion-activated video camera, instead of making your own.

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  • \$\begingroup\$ But I want to record video and audio (when motion is detected), and ideally run the OpenCV and TFLite to recognize birds and animals. What low power microcontroller can offer this to me. The ideal variant that I found is Orange Pi i96. Maybe, I can downclock the CPU to save some power. \$\endgroup\$
    – Robotex
    Sep 5, 2022 at 15:30
  • \$\begingroup\$ Hmmm, maybe I can use a pair of Raspberry Pi Pico and Orange Pi i96. \$\endgroup\$
    – Robotex
    Sep 5, 2022 at 15:31
  • \$\begingroup\$ @Robotex okay, then it might not be so simple - processing video does need some processing power. Though I would consider whether you could perhaps use a PIR (passive infrared) motion sensor to activate the Pi. \$\endgroup\$
    – user253751
    Sep 5, 2022 at 15:31
  • \$\begingroup\$ @Robotex I would guess that all of the Raspberry-Pi-style boards use about the same amount of power. But they might have different power-saving abilities. Like maybe one of them makes it easier to turn off the camera. \$\endgroup\$
    – user253751
    Sep 5, 2022 at 15:36
  • \$\begingroup\$ But maybe some powerful generators exist? For i.e. hydrogen power cells or alcohol power cells? \$\endgroup\$
    – Robotex
    Sep 5, 2022 at 15:36
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Raise a solar panel to the top of a tree?

If you have wind, use the movement of the branches to drive a ratchet system connected to them with rope to spin a generator with each stroke

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  • \$\begingroup\$ that seems complicated compared to a windmill \$\endgroup\$
    – user253751
    Sep 5, 2022 at 15:10
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    \$\begingroup\$ Will the windmill work in forest (I don't sure that wind will be strong enough here)? Is the windmills which can give you 50W of power 12 hours a day exist? \$\endgroup\$
    – Robotex
    Sep 5, 2022 at 15:33
  • \$\begingroup\$ no idea, sorry. \$\endgroup\$
    – user253751
    Sep 5, 2022 at 15:36
  • \$\begingroup\$ @user253751 Solutions probably depend on you getting to the tree tops, unless you have some handy geothermal sources about \$\endgroup\$
    – Dirk Bruere
    Sep 5, 2022 at 15:37
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    \$\begingroup\$ @Robotex That's a research project of its own. You're getting fanciful here. \$\endgroup\$
    – DKNguyen
    Sep 6, 2022 at 14:30

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