5 ms·

What chip would you recommend to do IoT which can run on harvested energy? What would be the upper limit which harvested energy could deliver? Do you mean sola

by antocv 10y ago

What chip would you recommend to do IoT which can run on harvested energy? What would be the upper limit which harvested energy could deliver? Do you mean solar cells or harvesting microwaves from satellites, I could get about 1.5V or so from about a 60cm in diameter disk, have not measured the current available. It would be really sweet to run something which speaks wifi even for short durations, if it recieves its energy from ephemeral radio.

porker 10y ago
I was trying to find something that could send a small message via Wifi when a toilet door was locked/opened; and could be powered by the lock motion or harvested energy. I failed.
- IshKebab 10y ago
  For that I wouldn't use WiFi. Use Thread or a custom nRF51 protocol. Both allow very long sleep times (infinite with a custom protocol) and can send millions of packets from a single coin cell.
- raarts 10y ago
  I've been looking for a very similar thing. Any hardware recommendations?
  - wycx 10y ago
    This may be of interest: http://jeelabs.org/2013/09/08/3-years-on-one-set-of-batteries/index.html http://jeelabs.org/2013/09/08/3-years-on-one-set-of-batterie...
jacquesm 10y ago
I think bi-directional WiFi is out when running on harvested energy, the best you could probably do is to send out a single UDP packet. That's why IoT applications tend to use other, simpler and lower power radios and protocols. https://en.wikipedia.org/wiki/IEEE_802.11ah https://en.wikipedia.org/wiki/IEEE_802.11ah Is very interesting but I'm not aware of any SOC that supports it. > It would be really sweet to run something which speaks wifi even for short durations, if it recieves its energy from ephemeral radio. One interesting source of power is a simple coil-and-diode to harvest radio waves, do this for a while until you have enough power to boot your device, take a reading and send off a sample. A few mW for a few seconds every couple of hours or so would be a good target. 100's to 1000's of mWs would take so long to harvest that you'd likely never get there because of leakage. And 'speaking' is the right term, I don't seen an easy way for such comms to be bi-directional without a lot more power to be consumed.
- y04nn 10y ago
  I wonder how much energy you can harvest from FM broadcast radios stations, those signals are pretty strong. Edit: I calculated a power flux density of 2.648µW/cm^2 from 3.16mV/m (70 dBµ) which is the 'city-grade contour' in the US. There seem to exist a patent for that, from a company called Freevolt (http://www.getfreevolt.com/ http://www.getfreevolt.com/).
  - jacquesm 10y ago
    Power law, so it's very much dependent on your distance to the transmitter. In NL some clever person figured out that he could power his fluorescent tubes from the broadcasting tower across the street and promptly got sued for theft...
    - haneefmubarak 10y ago
      Was the case ultimately decided against him? I mean, if they're radiating energy into his property, I'd imagine he could do whatever he wants with it.
      - jacquesm 10y ago
        I think yes, but it's long ago that I read about it. I'll try to dig up some info on this, it's interesting and now I want to know the exact details. I've found another reference to this(dutch): http://www.philipsradios.nl/forum/index.php?mode=thread&id=11835 http://www.philipsradios.nl/forum/index.php?mode=thread&id=1...
- mrb 10y ago
  "Is very interesting but I'm not aware of any SOC that supports it." That's because the 11ah standardization work is still in progress... It should be finally approved as a standard by the end of 2016: http://www.ieee802.org/11/Reports/802.11_Timelines.htm http://www.ieee802.org/11/Reports/802.11_Timelines.htm
teraflop 10y ago
My back-of-the-envelope calculations suggest that solar cells might be usable with something like the ESP32, depending on the environment. For example, under typical indoor lighting conditions, you ought to be able to get something like a hundred microwatts per square inch. That sounds tiny, but 3 in^2 would be enough for a 0.1% duty cycle, which would let you wake up for a fraction of a second every few minutes and transmit a sensor reading. Of course, that depends on having a very low sleep current, and on being able to transition between sleep and active WiFi connectivity very, very fast.
pjc50 10y ago
You can have either energy harvesting or Wifi, it seems. Wifi is quite demanding, hence things like Zigbee and 6LowPan.
semi-extrinsic 10y ago
Why is solar power out of the question? A 2000 mAh 5V solar power bank costs $13 on ebay. You could run an ESP8266 indefinitely on that, assuming you get >8 hours of daylight. That solar power bank weighs 300g and measures 15x15cm (6"x6"). Should be within the spec for most projects.
- antocv 10y ago
  That is so awesome, thanks for this idea! What Im using esp8266 for, is to control a strip of those ws2812b led lights, the chip will not need much energy, only sporadically to change light colors or on/off, so if I place that solar pad close to it - the led lights will charge the chip which controls them!
  - antoniuschan99 10y ago
    I'm working on this part and you'll definitely need to implement deep sleep, but also measure voltage. Right now I'm using ESP.getVcc() but im not 100% that is correct. Basically once the battery packs voltage drop below ~2.5v the user should get a warning it needs a recharge (just as a failsafe even when using the solar pack). Also, I haven't tried to see, but also make sure the battery pack allows the esp to draw current when in deep sleep or it wont wake up :$.
    - semi-extrinsic 10y ago
      I'm not sure you need to measure voltage on one of these power banks; they're made to charge phones over micro USB, so they will have a DC-DC transformer giving 5V all the way down to empty, I believe. Edit: also, I think the ESP8266 draws about 0.2W on average when it's on. If you have a 10 Wh battery, you can run it for 50 hours in theory. Would you then need deep sleep?
  - pjc50 10y ago
    Why not just power it off whatever powers the lights?!
  - unwind 10y ago

by antocv 10y ago

porker 10y ago

I was trying to find something that could send a small message via Wifi when a toilet door was locked/opened; and could be powered by the lock motion or harvested energy. I failed.

IshKebab 10y ago
For that I wouldn't use WiFi. Use Thread or a custom nRF51 protocol. Both allow very long sleep times (infinite with a custom protocol) and can send millions of packets from a single coin cell.
raarts 10y ago
I've been looking for a very similar thing. Any hardware recommendations?
- wycx 10y ago
  This may be of interest: http://jeelabs.org/2013/09/08/3-years-on-one-set-of-batteries/index.html http://jeelabs.org/2013/09/08/3-years-on-one-set-of-batterie...

jacquesm 10y ago

I think bi-directional WiFi is out when running on harvested energy, the best you could probably do is to send out a single UDP packet. That's why IoT applications tend to use other, simpler and lower power radios and protocols. https://en.wikipedia.org/wiki/IEEE_802.11ah https://en.wikipedia.org/wiki/IEEE_802.11ah Is very interesting but I'm not aware of any SOC that supports it. > It would be really sweet to run something which speaks wifi even for short durations, if it recieves its energy from ephemeral radio. One interesting source of power is a simple coil-and-diode to harvest radio waves, do this for a while until you have enough power to boot your device, take a reading and send off a sample. A few mW for a few seconds every couple of hours or so would be a good target. 100's to 1000's of mWs would take so long to harvest that you'd likely never get there because of leakage. And 'speaking' is the right term, I don't seen an easy way for such comms to be bi-directional without a lot more power to be consumed.

y04nn 10y ago
I wonder how much energy you can harvest from FM broadcast radios stations, those signals are pretty strong. Edit: I calculated a power flux density of 2.648µW/cm^2 from 3.16mV/m (70 dBµ) which is the 'city-grade contour' in the US. There seem to exist a patent for that, from a company called Freevolt (http://www.getfreevolt.com/ http://www.getfreevolt.com/).
- jacquesm 10y ago
  Power law, so it's very much dependent on your distance to the transmitter. In NL some clever person figured out that he could power his fluorescent tubes from the broadcasting tower across the street and promptly got sued for theft...
  - haneefmubarak 10y ago
    Was the case ultimately decided against him? I mean, if they're radiating energy into his property, I'd imagine he could do whatever he wants with it.
    - jacquesm 10y ago
      I think yes, but it's long ago that I read about it. I'll try to dig up some info on this, it's interesting and now I want to know the exact details. I've found another reference to this(dutch): http://www.philipsradios.nl/forum/index.php?mode=thread&id=11835 http://www.philipsradios.nl/forum/index.php?mode=thread&id=1...
mrb 10y ago
"Is very interesting but I'm not aware of any SOC that supports it." That's because the 11ah standardization work is still in progress... It should be finally approved as a standard by the end of 2016: http://www.ieee802.org/11/Reports/802.11_Timelines.htm http://www.ieee802.org/11/Reports/802.11_Timelines.htm

teraflop 10y ago

My back-of-the-envelope calculations suggest that solar cells might be usable with something like the ESP32, depending on the environment. For example, under typical indoor lighting conditions, you ought to be able to get something like a hundred microwatts per square inch. That sounds tiny, but 3 in^2 would be enough for a 0.1% duty cycle, which would let you wake up for a fraction of a second every few minutes and transmit a sensor reading. Of course, that depends on having a very low sleep current, and on being able to transition between sleep and active WiFi connectivity very, very fast.

pjc50 10y ago

You can have either energy harvesting or Wifi, it seems. Wifi is quite demanding, hence things like Zigbee and 6LowPan.

semi-extrinsic 10y ago

Why is solar power out of the question? A 2000 mAh 5V solar power bank costs $13 on ebay. You could run an ESP8266 indefinitely on that, assuming you get >8 hours of daylight. That solar power bank weighs 300g and measures 15x15cm (6"x6"). Should be within the spec for most projects.

antocv 10y ago
That is so awesome, thanks for this idea! What Im using esp8266 for, is to control a strip of those ws2812b led lights, the chip will not need much energy, only sporadically to change light colors or on/off, so if I place that solar pad close to it - the led lights will charge the chip which controls them!
- antoniuschan99 10y ago
  I'm working on this part and you'll definitely need to implement deep sleep, but also measure voltage. Right now I'm using ESP.getVcc() but im not 100% that is correct. Basically once the battery packs voltage drop below ~2.5v the user should get a warning it needs a recharge (just as a failsafe even when using the solar pack). Also, I haven't tried to see, but also make sure the battery pack allows the esp to draw current when in deep sleep or it wont wake up :$.
  - semi-extrinsic 10y ago
    I'm not sure you need to measure voltage on one of these power banks; they're made to charge phones over micro USB, so they will have a DC-DC transformer giving 5V all the way down to empty, I believe. Edit: also, I think the ESP8266 draws about 0.2W on average when it's on. If you have a 10 Wh battery, you can run it for 50 hours in theory. Would you then need deep sleep?
- pjc50 10y ago
  Why not just power it off whatever powers the lights?!
- unwind 10y ago