Creating a regulated 5v DC voltage from piezo disc

Thread Starter

bboy2311

Joined Mar 7, 2023
5
Hi, quite new to electronics and anything that would help would be very much appreciated.

I am currently designing a circuit for some piezo disc to be able to produce a regulated dc 5v.
as of the moment, all i have is a bunch of piezo disc, connected to a full bridge rectifier each in order for each disc to work individually even if the other do end up being damage, all the rectifiers are then connected parallel to each other, then this goes to a capacitor.

I have thought and tried connecting a voltage regulator to the capacitor in order to produce a regulated 5v voltage and found that this would not work as the voltage regulator component requires certain amount of current to work.

On the other hand, i am currently trying to figure out how a buck converter works and have this component https://shop.pimoroni.com/products/mpm3610-5v-buck-converter-breakout-21v-in-5v-out-at-1-2a at hand to use but cant seem to get any output.
I know the current im producing are quite low therefore the use of the buck converter with low operating current.

anyone have any suggestion as to how i should connect the components and what components i may need to have a regulated 5v? The regulated 5v output would go in a microcontroller where it processed or just read as a signal.

current system at the moment would be like this

1678229319047.png
any improvement on the system suggested would be much appreciated.
 

sagor

Joined Mar 10, 2019
910
How much current can the piezo disc actually produce? What is the voltage on the capacitor? Try a small load resistor on the cap to see how the voltage changes with current draw.
A linear regulator will draw in the order of 5mA to 10mA (maybe) when idle. I suspect a buck converter will use even more.
Unless your piezo disk can produce in the order of hundreds of mA, no way you will be able to power the Micro, regardless of regulator...
Most piezo, unless some commercial unit, give only a few mA of current. You cannot power a regulator with that little current, you would need dozens or hundreds of them in parallel to provide "power".
 

Papabravo

Joined Feb 24, 2006
21,225
The immutable rule of any power conversion system is:

The power out will always be less than the power in, sometimes it will be much less.
From your block diagram I count 4 conversion processes. Let us assume for the sake of argument that each process is 85% efficient. Some will be better, and some will be worse. The efficiency of the overall process will be 52%. If the output power required by the microprocessor is, for example, 25 milliwatts, then the piezo disc would need to produce approximately 48 milliwatts. Can a piezo disc product that power level? If not what power level is it capable of producing?
 

Audioguru again

Joined Oct 21, 2019
6,693
What is vibrating the piezo discs? What frequency? Do your rectifiers work at that frequency?
Please attach the datasheets of the piezo discs and the rectifiers.
 

Thread Starter

bboy2311

Joined Mar 7, 2023
5
What is vibrating the piezo discs? What frequency? Do your rectifiers work at that frequency?
Please attach the datasheets of the piezo discs and the rectifiers.
well the idea is to put the piezo into an insole of a shoe so walking would be what's going to put mechanical stress into it which would roughly about 2hz? and yes the rectifiers working using a full bridge rectifier and here are the spec i could find for the piezo disc.
Specifications:
* Drive Type: Piezo Discs
* Resonant frequency(kHz): 3.0~5.0+/- 0.5 KHz
* Resonant impedance (ohms): 300 max
* Diameter: 35mm/ 1.38 inches
* Thickness: 0.7mm/ 0.02 inches
* Cable Length: 100mm/ 3.94 inches
* Material: Brass
 

Thread Starter

bboy2311

Joined Mar 7, 2023
5
How much current can the piezo disc actually produce? What is the voltage on the capacitor? Try a small load resistor on the cap to see how the voltage changes with current draw.
A linear regulator will draw in the order of 5mA to 10mA (maybe) when idle. I suspect a buck converter will use even more.
Unless your piezo disk can produce in the order of hundreds of mA, no way you will be able to power the Micro, regardless of regulator...
Most piezo, unless some commercial unit, give only a few mA of current. You cannot power a regulator with that little current, you would need dozens or hundreds of them in parallel to provide "power".
Hi thank you, the purpose of the piezo is not to power a microprocessor. the microprocessor will be powered by an external source and will only read the regulated voltage from the piezo. Ive tried using a voltage regulater and seem to draw quite alot of current for it to work. however the buck converter mentioned above has a 200µA Low Quiescent Current however when i tried it, the voltage can im producing can only reach up to 2.5v in to the capacitor.

Im thinking if theres anyway i can put an automatic switch in between the buck converter and capacitor which would allow the capacitor to charge up, then a switch would turn on and allow current to flow to the buck converter and produced a regulated 5v.

I am currently looking at 555timers and cant seem to figure out how i would wire it to be like an automatic switch.
 

Papabravo

Joined Feb 24, 2006
21,225
Hi thank you, the purpose of the piezo is not to power a microprocessor. the microprocessor will be powered by an external source and will only read the regulated voltage from the piezo. Ive tried using a voltage regulater and seem to draw quite alot of current for it to work. however the buck converter mentioned above has a 200µA Low Quiescent Current however when i tried it, the voltage can im producing can only reach up to 2.5v in to the capacitor.

Im thinking if theres anyway i can put an automatic switch in between the buck converter and capacitor which would allow the capacitor to charge up, then a switch would turn on and allow current to flow to the buck converter and produced a regulated 5v.

I am currently looking at 555timers and cant seem to figure out how i would wire it to be like an automatic switch.
That won't help. The evidence suggests that the system equilibrium point is reached when the capacitor is being discharged at the same rate that it is being charged. You seem to be trying to find a free lunch, and this quest is doomed because there is no free lunch – anywhere.
 

Audioguru again

Joined Oct 21, 2019
6,693
I have a Murata piezo transducer the size of yours.
When I scream or whistle very close to it my expensive digital meter measures 0.02VAC for a moment.
When I hit the center of it with a stick it measures 2VDC for a moment but with no current.

Overall pressure does nothing, You need it to flex somehow in a shoe. Then its output power is almost zero.
 
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