Simple Squeeze Led Flashlight

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Introduction: Simple Squeeze Led Flashlight

Nearly 200 years ago Michael Faraday has discovered electromagnetic induction. A changing magnetic field produces an electric field in a coil. Today, there is a simple way to gain electricity from a relay and a strong magnet. I call this kinetic generator the RattleGen because, by pressing the lever of the relay quickly (the only moving part!) it makes a rattling noise. This electro generator is nearly solid state and produces enough energy to power a LED. Compared to 100 years of dyna flashlight based on a rotating generator, the RattleGen squeezer is nearly indestructible because of the few mechanical parts. This Ibble is part of an ongoing investigation for smallscale, batteryless energy harvesting.



Step 1: The Circuit

The electronic circuit is very elementary as you can see here. I use a resistor to reduce the LED current. Why do I call it an enhanced RattleGen? Well, doing experiments with a relay and a magnet, early 2013, I discovered on my oscilloscope screen a useful voltage. A ceramic magnet was put agains the relay coil. Pressing the contact lever made energy, as you can see in the video. A bit later I placed a strong neodymium magnet on the contact lever of the relay. As a result, the voltage was peaking 2 times higher on the screen. Then I took a small relay; the output peak voltage of the relay coil was 35 volt, without load. After the bridge rectifier the voltage peaks are smoothed by a condenser. To test the small generator I use an ultra bright LED. Take care; depending on the iron of the relay coil a stronger magnet will not give more flux, this because of the saturation. If you make the gap bigger between the contact lever and the relay coil the output will enhance. The magnet functions also as tension spring. The lever jumps back after pressing. This saves again one mechanical part. Before the LED light up you have to press the contactlever several times. The capacitor of 1000 microfarad 16 volt has to charge first.

Step 2: Some Remarks

Later, I will publish the test data at my website's energy blog. More experiments are necessary to optimize the parts; the results are already promising. This kinetic energy harvester can compete with the output of existing piezo generators and is much cheaper. Soon more applications will follow, with the RattleGen as starting point. My intention is that also people in developing countries can easily build this squeeze flashlight. And don't forget the young makers. Beside de fun of making this project, it shows them also one of the basic principles and needs of our present civilisation; electricity and light.

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    Hi there, I was wondering how frequently would you have to squeeze the lever, for example would it be possible (still functioning well) if it were integrated into the sole of a shoe so with each step the capacitor is charged or are footsteps too slow to charge the capacitor?

    26 Comments

    If you shake the flashlight really fast, Can't it exceed the maximum voltage of the capacitor?

    The Maximum voltage of the capacitor is 16V. No way to exeed that voltage by fast squeezing. The only thing that happens is that the LED is going to light brighter. The voltage of the capacitor stays around 2.5 volt.

    If I create this, I still must put a little battery (CMOS ~ I think it's better for recharged) and IC that can run a little tiny dynamo repeated around 1 minute (we can find that inside a cell phone)

    Already try with Omron 12V but I just got 0.25V... Maybe must using Joule Thief to get enough power..?

    ~ 1 Vote for you :)

    Thanks for voting for me! The most important part for gaining energy is the relay. Use a 24V relay with minimal 1200 ohm coil resistance. The magnet I use is a ringmagnet 10x6mm with a hole of 4mm, power N48 with a holding power of 3kg. A joule thief and a voltage step-up converter like the ZXSC380 pull's min.10 mA. I connected both; they use to much current and make's the LED flashing.

    Thanks for this follow up on your RattleGen.

    I really must try it in a workshop with kids one day.

    For a workshop I would need about 20 relay I'm sure that will work, and scavenging that manny is not really practical.

    So I would have to try an buy them cheap. The cheapest car relays are only around 1 euro and that is right into the ally of my kind of workshops, but I'm not sure if those would be suitable. Any recommendation on which ones to buy and where?

    I would suggest adding a switch as well, to break the circuit when it's not needed, and to keep the capacitor charged up for quicker use the next time.

    So out of my league, but would love to build one...could you provide a parts and tools list?

    Good that you remember me at this point. I place the list in the Instructable. Because the few parts and tools needed, you get it here. Parts: 1 small relay 24V (watch if the contactlever is useful), 1 magnet 8mm diameter 4mm thick, 4 diode's 1N4148 or 1N914, 1 LED, 1 resistor 47 ohm, 1 capacitor 1000 microfarad 16V and a piece of printboard. Tools: Soldering iron, thin solderwire, a wirecutter, an iron saw, mounting wire. That's it. Some relay's you can only open with a saw. Others you can take off the transparant cover. Look for a relay with a minimum of 1200 windings; 1800 is better. Success with building one!

    You could make it bigger and mount the magnet on a spring so that it oscillates more for each push.

    It is a step forward, when pushing results in more repetitious movements of the lever. Using mechanical oscillation or resonation to produce more pulses enhances de efficiency of the RattleGen. Clichej1, I like to tinker with spring's, this wonderfull objects. Maybe a new concept shows up. We keep in touch!