Piezoelectric sensors - Energy harvasting - Page 1
Forum section: electronics / projects

author: Nikos A.
author_rank: Regular Contributor
timestamp: January 16, 2020, 06:30:04 pm
content: Hi everyone, I am designing a smast insole and I want to include energy harvasting from piezoelectric sensors (probably PZTs) as an auxiliary charging system. I want to ask if anyone has experience with piezo energy harvesting and how should I connect the sensors (I am not sure for the quantity) with the ic ( I am looking for the BQ25505 of Texas Instrumenrs)Thanks in advanceNick

author: moffy
author_rank: Super Contributor
timestamp: January 17, 2020, 11:00:40 am
content: Where are you getting your PZT material from? I looked a while back and found it hard to source at a reasonable price.

author: Nikos A.
author_rank: Regular Contributor
timestamp: January 17, 2020, 05:30:39 pm
content: There are available PZT disks on Amazonhttps://www.amazon.com/Prewired-Elements-Buzzer-Sounder-Trigger/dp/B01N5HN94S/ref=mp_s_a_1_8?keywords=piezoelectric+sensor&qid=1579282176&sprefix=piezoe&sr=8-8

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: January 17, 2020, 06:04:01 pm
content: PZTs are great at generating impressive voltages into high impedance loads, but absolutely terrible at energy conversion. IOW, they don't produce much actual power. Expect charging anything useful to take a very long time.

author: Twoflower
author_rank: Frequent Contributor
timestamp: January 17, 2020, 07:03:45 pm
content: In a newspaper I found a link to some commercial products:https://piezo.com/collections/piezoelectric-energy-harvesters?_=pf&pf_t_quantity=Quantity__1Not really cheap as it looks like. Especially if you check the output power: 26mW for $60.

author: moffy
author_rank: Super Contributor
timestamp: January 18, 2020, 06:28:33 am
content: The amazon PZT's appear quite reasonable. Pity they are only round.

author: Nikos A.
author_rank: Regular Contributor
timestamp: January 18, 2020, 11:10:00 am
content: I am trying to figure out how to connect/combine the piezoelectric sensors since the output voltage of each one would not be the same ( it is proportional to the applied pressure and since they are intented for insole application the output of each one will differ according to the pressure applied by the foot)Any help?

author: Marco
author_rank: Super Contributor
timestamp: January 18, 2020, 10:00:39 pm
content: Wouldn't dielectric elastomers be much better for energy harvesting in a sole? (ie. a charged capacitor with a compressible dielectric.)

author: Nikos A.
author_rank: Regular Contributor
timestamp: January 18, 2020, 11:15:57 pm
content: Maybe.. I do not know how this technology works but at the moment I want to proceed with piezoelectric..

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: January 19, 2020, 04:41:38 am
content: If you distribute them it's almost certain they will be working at cross purposes. No doubt one could use diodes to steer the charge, with the associated losses of course. I'd find one location that moves in a predictable fashion and put the device(s) there. Not sure if it's best to go parallel or series.

author: Marco
author_rank: Super Contributor
timestamp: January 19, 2020, 02:56:24 pm
content: You should probably prestress the piezo discs, they are meant to bend likethisalong the entire edge of the disc, not compress or bend along just one axis.So put a tiny bit of rubber in between two discs and then clamp/glue the edges together. That way when you compress the rubber they bend like they are supposed to.

author: soubitos
author_rank: Frequent Contributor
timestamp: January 19, 2020, 03:52:46 pm
content: Might be aware of this, might not, i found it very interesting read though.https://www.researchgate.net/publication/326905148_Experimental_Evaluation_of_Piezoelectric_Buzzers_as_Devices_for_Energy_Harvesting

author: Nikos A.
author_rank: Regular Contributor
timestamp: January 30, 2020, 09:16:25 am
content: Thank you, I am going to conduct some experiments and will come back with a feedback!!