I have made this project to demonstrate that electricity can be generated using piezoelectric generators in sidewalks and roads.Few pictures of the project are attached along with the readings of multimeter as i stepped on it. I've added diodes to piezo transducer to convert AC to DC and to prevent the energy produced by one crystal being used by the other to produce sound. Now I want to use this energy to light up some LEDs and have no idea how to do that. I connected one Led directly to the voltage produced and it lighted up but very dimly.
Please help me to figure out the solution.
This is very cool, but I'm not certain how you were hoping an Arduino would help when you got the LED to light with the power produced already? From the results you're getting there's not a steady or large amount of power there to run the LEDs more, unless you're hoping to charge a big capacitor or similar and discharge that to run them brighter for a time?
What's the end result you're looking for with a bit more detail and we should be better able to help?
You might try using a standard old-time AC power supply circuit, meaning half-wave or full-wave
bridge rectifier feeding into a large capacitor, to store the energy generated. The rectifers
[ie, simple diodes] prevent the capacitors from being discharged as the input voltage drops
below the stored level on the cap. 1N4004 diode should probably work, and maybe use
500-1000 uF electrolytic cap.
As piezos can generate voltages in the 100s of volts range, you'll probably want some sort of
voltage clamping circuit to keep the output within reasonable limits, eg 5.1V zener diode.
Then, use a current-limiting resistor in series with the Led so the Led forward voltage [about 1V]
doesn't pull down the output voltage. It may take several knocks on the piezo before getting
much Led output.
If you put a smooth round tube in moving fluid, it will generate a street vortex:
It can be a string and the force will vibrate the string. At each end there will be vibrating pull.
It can be a tube, the tube will experience vibrating force.
It can be cables on a suspension bridge and at least one big bridge fell apart because of it.
I understand that at least one car company tested piezos inside a car muffler and generated useful current so that the alternator had to work less, thus saving gas.
Faster vibrations are better. You only need a source. The less moving parts like axles and bearings to maintain, the better. Suppose it is raining hard and you seal the unit into a card or plate? Would a monsoon just hold it down unless it was small?
Piezo disc here costs $1. How long to generate $1 worth of electric?
The US Army experimented with piezos in boot soles to help charge batteries. They did, but they also slowed the soldiers down just a little in tests. Conservation of energy at work, no free energy. A road or sidewalk would have to take away from what travels on it.
I have added a rectifier and capacitor for smoothing as suggested by @oric_dan but still LED is not lighting up
Now you need to run the same experiment as in your video of post #1, and see if you are able to
accumulate a voltage on the cap - ie, without the Led connected.
Chances are the Led and series resistor [you do have one ???] are bleeding off the charge before it builds
up enough to noticeably light the Led, meaning you may need a trigger circuit to hold off Led turnon until
the charge is high enough.
The first step is building up energy in the storage device [capacitor]. the second step is being able
to use it effectively.
The "old" way to tell if a cap is charged up is to short its terminals together. Usually good for a really
nice spark and crack! If you're getting that, you ought to have enough energy to light an Led, if only
briefly.
I have made the one in the second video I posted link to and it works when hooked up correctly.
I had used that as the basis for piezo touch sensor too but it takes a transistor to bump the signal up to read HIGH (3.4V) on a digital pin. I keep from overloading the pin by supplying limited (5V through 22k ohms) current to the collector.
I had used that as the basis for piezo touch sensor too but it takes a transistor to bump the signal up to read HIGH (3.4V) on a digital pin. I keep from overloading the pin by supplying limited (5V through 22k ohms) current to the collector.
I think that's the question... Do you need to get the energy from the piezo, or can you use an external power supply/battery and just trigger the LED from the piezo signal?
If so, how much energy can you get from the piezo?
If you connect a capacitor, without the LED or other load*, (several microfarads, at least) you can charge it up and calculate the energy. With a larger capacitor, it may take several "hits" to charge-up a measureable voltage. (If it needs more than one hit, you'll need to count the hits and, you'll need the rectifier to charge the capacitor with DC.)
Once you have that, the energy stored in the capacitor is proportional to the capacitance x voltage, so a 1000uF cap will take 10 times as long (10 times as many piezo hits) to charge up, as a 100uF cap, but the total energy stored will be 10x as much (at the same voltage).
You can look up the formula which will probably give you energy in Joules, and you'll have to convert that to watt-seconds or milliwatt-seconds to see if you are getting the power you need.
I wouldn't even hook-up the meter. Charge the cap without the meter connected, and then hook-up the meter and the cap will start discharging through the meter. But you don't want to over-voltage the cap, so give it a few hits with the piezo and see how it's going before you go too far...
Getting power from leds, you want frequent hits. A piezo lighter generates a 1500V spark, with very little current -- low ohms can tame it. Get a string or cable vibrating and you can get useful though small power out of even just one piezo. Imagine a bunch of piezos in a circle with a windmill driving something bumpy over them. Sure, it would make noise but it would make power too.
Look at a piezo as a capacitor with mechanical coupling. If you stress the material, it charges the plates, therefore the leads! If you put a potential across it, it tries to bend.
So when you connect the leads to resistors you have an R-C circuit and yes you can measure tap strength by how long it takes to bleed. I know I have!
BTW, a bare piezo disk as a speaker sounds tinny but pressed/2-side taped to a card or a number of objects sounds a lot better.
There was some problem with the wiring.
After i fixed it, I hopped over it for quite a while. When the multimeter reading showed 3.5 V , I connected a LED it lighted up for a second then the power drained probably because of low current. What could I do for boosting up the current ?
I put one edge of a disk up on a pen and tapped the center, it made the led shine brighter.
You can keep a led lit this way, but it's the frequency of taps/stressings over time that makes a difference. Like 1000's of taps per minute maybe can burn a led out, depends on how hard the piezo is hit.
I hope you're not expecting to run a motor off a piezo?
I was able to produce 7V by hopping over the slab, capacitor used .
after that I tried with the zener diode rectifier .
Even after hopping for quite a while the voltage doesn't cross 2V . Is it because of the regulater?
I have used 1000uf 10 V capacitor
40 ohms resistor
5.1 V zener diode
1n4007 Diode
You saw the circuit for the Mark II in the video? No transformer, no zener, every diode takes some toll, the least is best.
Shottkey diodes eat less of your power than the regular kind, .3V instead of .7V.
Jumping up and down gets more V in a pulse, yes, but the thing that flexes the disk 100 times a second at 2V will fill the capacitor quicker than 1 7V hit 2x per second or so.
I put 1 edge of a disk up on a pen and the other on the table so the center was not supported. Taps on the center then did make the led light brighter even though they were no harder than taps made when the disk was flat on the table. It is a matter of flex.
Still the electrons only flow a short time per flex so you want to get 'frequent flexer current' so to speak. That's why wind vibrating a string or cable or other way to get fast constant vibration is how people are doing it. Just be aware that people from MIT and other schools are not only doing these things but also have patents (or patents pending) on some designs or parts of designs. Make your own but do research before selling anything!
