which type of connection will yield more output from peizodiscs

SujithZis · Jan 26, 2014

I'm planning to connect 23 peizo discs in some way so as to get max volt and current

I am current able to get 2.5V 0.02mA of current from a single peizo discs

Calculations for the types of connection

Also could you tell me what type of connection is given in this pic

audioguru · Jan 26, 2014

Why do you have this second thread? You should continue in your original thread.
Your piezo film transducers produce only 0.02mA for only the moment that they are flexed then they produce nothing until they are flexed again during the next footstep.
So the average current might be only 0.001mA. The very high current rectifiers you use might have a leakage current more than that. You should use 1N914 or 1N4148 low leakage signal diodes instead.

Most of the piezo transducers in your schematic have 3 wires but I think they all have one of their 2 wires connected to the two capacitors. Then you need only two rectifier diodes and connect the piezo film transduces directly in parallel. Then the LED will dimly blink for a moment each time the piezos are flexed and unflexed and the battery will have no charging current.

Notice that the tiny amount of power is produced for very short time durations, not continuously like a generator.

SujithZis · Jan 30, 2014

i have done all that

i know about the rectification part and all

i just need to know .... which type of connection to be used for connecting peizos

Misterbenn · Jan 30, 2014

well I'd say a solder joint would probably do the job ....

audioguru · Jan 30, 2014

When the 23 piezo transducers are connected together then their polarities must be correct so that they add instead of cancelling each other.
In series then their voltages add but the total current will be extremely low.
In parallel then their currents add but the voltage might not be high enough to be rectified.

I do not know how you will mount the transducers in a shoe so that they flex (bend) and unflex with each footstep. If they flex too much then they might fracture.

JimB · Jan 30, 2014

At the risk of appearing to cast a cloud of negativity across the thread...

This energy harvesting scheme will never be a success, it is just a fools errand which has been tried before and failed to live up to expectations.

Having said that, please feel free to waste your own time and money.

JimB

alec_t · Jan 30, 2014

As a school project there may be some value in demonstrating that this method of harvesting energy simply cannot provide enough output to charge a phone, even enough for one phone call, in any reasonable time.

audioguru · Jan 30, 2014

Like the kid who made a windmill generator for his bicycle made from a little computer fan. It charged a battery all day to light an LED at night for only a couple of seconds.

JimB · Jan 30, 2014

As a school project there may be some value in demonstrating that this method of harvesting energy simply cannot provide enough output to charge a phone, even enough for one phone call, in any reasonable time.

Thinking back many years, I remember that there was some kind of imperitive with school pupils to "Get the right answer", otherwise you will get poor marks.
In the real world of engineering, often a pilot study is done to verify if something stands a chance of working. A "proof of concept" if you like.
When the result from the proof of concept study shows that the thing does not stand a hope in hell of doing anything useful, the idea is dropped and hopefully everybody learns not to do things like that again.

Maybe this should be the lesson learned from this study, energy harvesting from piezos in your shoes is a bad idea.

JimB

ChrisP58 · Jan 30, 2014

Well, not to throw more cold water on this idea, but I think there is a problem with the idea of stringing them in series.

I am assuming that the Piezo elements will be distributed across the length of the shoe. So, normal walking will stress each element at a different time. Although there will be some overlap, only a few will actually be in their positive phase at any one point in time. Worse, is that some of the elements will be in their negative phase during the step, which will tend to cancel out some of the positive voltage.

Now, if you hop down the street instead of walk, so that all of the elements are in phase, you might get some series adding of the voltage.

SujithZis · Jan 31, 2014

ChrisP58 said:
Well, not to throw more cold water on this idea, but I think there is a problem with the idea of stringing them in series.

I am assuming that the Piezo elements will be distributed across the length of the shoe. So, normal walking will stress each element at a different time. Although there will be some overlap, only a few will actually be in their positive phase at any one point in time. Worse, is that some of the elements will be in their negative phase during the step, which will tend to cancel out some of the positive voltage.

Now, if you hop down the street instead of walk, so that all of the elements are in phase, you might get some series adding of the voltage.

Suggesting vedios of our previous project ..... these are the test vedios

**broken link removed**
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in one of those we are getting as much as 14V ..... we used 20PEizos in paralllel ....
But bad luck we forgot to measure the current generated

SujithZis · Jan 31, 2014

audioguru said:
When the 23 piezo transducers are connected together then their polarities must be correct so that they add instead of cancelling each other.
In series then their voltages add but the total current will be extremely low.
In parallel then their currents add but the voltage might not be high enough to be rectified.

I do not know how you will mount the transducers in a shoe so that they flex (bend) and unflex with each footstep. If they flex too much then they might fracture.

Im using PEizo disc .... and soo not costly
they are pretty durable ... i have made atleast 5 Peizoelectricity MODs in the past and i know they last .....

SujithZis · Jan 31, 2014

JimB said:
At the risk of appearing to cast a cloud of negativity across the thread...

This energy harvesting scheme will never be a success, it is just a fools errand which has been tried before and failed to live up to expectations.

Having said that, please feel free to waste your own time and money.

JimB

But where is the fun in doing things that everyone is doing

audioguru · Jan 31, 2014

First you said you used 23 piezo FILMS that I have never seen then now you say you are using some cheap piezo DISCS that might be from a beeper. You forgot to say their size.
To make a tiny amount of power a piezo must flex (bend) and unflex very quickly, not simply slowly stepped on.

The videos showed a meter in the dark and we do not know if it showed AC or DC (volts?). We do not know if somebody (who?) in the video had 23 piezo discs in a shoe or if the discs were under a mat. You measured 14V from 20 paralleled piezo discs but you forgot to measure the very brief length of time. I doubt your meter can make an accurate measurement for such a short amount of time and it probably cannot measure the extremely tiny current.

This thread and your other threads have been going on and on for almost one week. Can your piezo discs in a shoe charge a huge capacitor or a battery for a few hours then light an LED with 10mA for longer than a couple of seconds?

SujithZis · Feb 16, 2014

Actually my original question in my first post ....
I just Need another circuit diagram

audioguru · Feb 16, 2014

SujithZis said:
Actually my original question in my first post ....
I just Need another circuit diagram

Didn't you try it? Your piezo discs will not produce enough power to do anything unless you continuously strongly vibrate them.
I recommended replacing your very slow high leakage rectifiers with very fast very low leakage signal diodes.

SujithZis · Feb 16, 2014

low leakage signal diodes!! can you give me a few examples

and also ... how should i conncect them to the output from peizos

audioguru · Feb 16, 2014

SujithZis said:
low leakage signal diodes!! can you give me a few examples

I gave two examples in post #2.

how should i conncect them to the output from peizos

Piezos directly in parallel might not work because some will be trying to produce a positive voltage and the rest might be trying to produce a negative voltage then they cancel.
Also if some piezos are not producing a voltage then they will be flexed by the ones producing a voltage which reduces the voltage.

You used a diode in series with each piezo which isolates them if some have reversed or no voltage. But it is half-wave so you miss half of the action. Full-wave bridges might work better but need extra voltage and use many diodes.

SujithZis · Feb 16, 2014

yes ... i was also planning on connecting it directly to the peizos

according to the info i found

full wave bridge are bigger (four legged )
so i have decided to stick with halfwave bridge rectifier like

[Also can i use zenner diodes , also will using half wave bridge rectifier affect the current output]

audioguru · Feb 16, 2014

A zener diode regulates voltage by wasting power. You have extremely low power so you do not want to waste any. You do not need voltage regulation anyway.
A half-wave rectifier does nothing half of the time. A full-wave rectifier produces voltage and current when the piezo voltage is positive AND when it is negative.

You might connect the piezos so that a quick footstep produces a negative voltage pulse. Then if you use half-wave diodes and their polarity will produce a positive output they will do NOTHING.
But if you use a full-wave bridge rectifier the output will be positive if a footstep produces positive OR negative pulses.

Before making any more replies you must put some piezos in a shoe feeding signal diodes that charge a capacitor when you walk for 1 hour. Measure the starting voltage at the charged capacitor then load it with a resistor. Time how long it takes for the voltage to drop to half then calculate the average current.

which type of connection will yield more output from peizodiscs

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