4 ms·

Does this sort of harvesting rely upon some internal accumulator like a capacitor before the energy could be fed elsewhere? Also a question if such harvester n

Does this sort of harvesting rely upon some internal accumulator like a capacitor before the energy could be fed elsewhere? Also a question if such harvester need its own power source to be able to operate? They cite a super wide range of EM freqs from Hz to MHz, and an efficient antenna...

simonbarker87 3y ago
Yes, you need a reservoir to store the charge (energy) which in my case was the limiting factor to deployment in high temperature environments as capacitors get very leaky as temperature increases. Harvesters don’t need their own power supply and ideally the system can come back to life from totally empty (meaning it doesn’t need to be deployed with any charge level) I was doing my thing back before the packaged harvester management chips were available and I made a PIC based microcontroller system that could monitor the charge level in a capacitor fed from a piezoelectric vibration energy harvester and decide when to wake up and transmit a data reading based on the capacitors charge level. The trick was getting the PIC’s sleep current draw low enough that the capacitor was charging even at milli g level vibration levels - from memory you can get a PIC’s sleep current well down in the tens of nano amp range. PICs have a built in voltage reference that is stable (a zener or schotkey diode from memory of 0.6V?) and a way to read what the Vsupply (basically the capacitor) is compared to it. So the PIC would wake up every 30 seconds, check Vsupply to the built in reference and, when high enough fully wake up, take and transmit a reading and go back to sleep. From memory I got it running at 50mg transmitting every few minutes. I got a nice journal publication in IEEE for that work.
- zoomablemind 3y ago
  Cool project. Thanks for sharing the details! So the harvester sustains itself, keeps filling up the bucket, and periodically reports out the progress. I guess it's a balancing game, as the filling up process is probably slow, so the target's draw needs to be low too.
  - simonbarker87 3y ago
    Thanks, it didn’t report back progress of charging, it was connected to a sensor (light sensor in this case but could be anything really) and would transmit that back to a base station. The main use of energy harvesting is for powering wireless sensor nodes, so this was a simple implementation of that.
- biomcgary 3y ago
  Don't be so modest. Citation needed. :-)
  - simonbarker87 3y ago
    Lol, thanks - best link I can find: https://digital-library.theiet.org/content/journals/10.1049/iet-wss.2010.0053 https://digital-library.theiet.org/content/journals/10.1049/... Looks like it was an IET journal, I think my IEEE publications were all conferences.
    - biomcgary 3y ago
      The linked paper made sense once I realized mg is not milligrams. You sound like a former academic like me. All those papers/citations were so important (publish or perish), but now you just have to get things done, not so much writing.

simonbarker87 3y ago

Yes, you need a reservoir to store the charge (energy) which in my case was the limiting factor to deployment in high temperature environments as capacitors get very leaky as temperature increases. Harvesters don’t need their own power supply and ideally the system can come back to life from totally empty (meaning it doesn’t need to be deployed with any charge level) I was doing my thing back before the packaged harvester management chips were available and I made a PIC based microcontroller system that could monitor the charge level in a capacitor fed from a piezoelectric vibration energy harvester and decide when to wake up and transmit a data reading based on the capacitors charge level. The trick was getting the PIC’s sleep current draw low enough that the capacitor was charging even at milli g level vibration levels - from memory you can get a PIC’s sleep current well down in the tens of nano amp range. PICs have a built in voltage reference that is stable (a zener or schotkey diode from memory of 0.6V?) and a way to read what the Vsupply (basically the capacitor) is compared to it. So the PIC would wake up every 30 seconds, check Vsupply to the built in reference and, when high enough fully wake up, take and transmit a reading and go back to sleep. From memory I got it running at 50mg transmitting every few minutes. I got a nice journal publication in IEEE for that work.

zoomablemind 3y ago
Cool project. Thanks for sharing the details! So the harvester sustains itself, keeps filling up the bucket, and periodically reports out the progress. I guess it's a balancing game, as the filling up process is probably slow, so the target's draw needs to be low too.
- simonbarker87 3y ago
  Thanks, it didn’t report back progress of charging, it was connected to a sensor (light sensor in this case but could be anything really) and would transmit that back to a base station. The main use of energy harvesting is for powering wireless sensor nodes, so this was a simple implementation of that.
biomcgary 3y ago
Don't be so modest. Citation needed. :-)
- simonbarker87 3y ago
  Lol, thanks - best link I can find: https://digital-library.theiet.org/content/journals/10.1049/iet-wss.2010.0053 https://digital-library.theiet.org/content/journals/10.1049/... Looks like it was an IET journal, I think my IEEE publications were all conferences.
  - biomcgary 3y ago
    The linked paper made sense once I realized mg is not milligrams. You sound like a former academic like me. All those papers/citations were so important (publish or perish), but now you just have to get things done, not so much writing.