Rechargeable Flashlight With Hand-Crank Generator




Introduction: Rechargeable Flashlight With Hand-Crank Generator

About: I love making and breaking electronics.

Hey everyone!! It's been a long time since I last posted an instructable. I hope to post an instructable a week or every two weeks from now on, so I'm Back!

Today I am going to show you how to make a Rechargeable Flashlight With Hand-Crank Generator. It is a really simple, and fun project, and if you look carefully you will see that I capitalized the name of the project since it is that EPIC! Maybe not too epic, but the project should teach you some basics of how generators work, how capacitors work, and give you general knowledge about rectifier circuits. Also, after the project is done, you will have steampunk-ish flashlight which runs completely from the energy produced by the hand-crank generator. If you charge the flashlight for about 30 seconds, you could run the flashlight brightly for over 2 minutes, and a bit dimly for a few more minutes. So it could be pretty handy to make one of these flashlights in preparation for that day when everyone around you turns into a zombie or you lose your compass in the forest along with your GPS.

In this instructable I will explaining many things as if I was talking to a electronic newbie just like me. So if you feel my explanations for the circuit isn't adequate or clear, then help me improve them. I am not a professor by any means, I am a junior in High school after all. So help me improve this instructable with your knowledge. Thanks you!

Without further ado, let's get on with the project!! Hope you will find it useful

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Step 1: Watch the Video!

"A picture is worth a thousand words." A wise man said this, and I always tend to believe in wise people. So if you have a thousand pictures captured into one video, the video would be worth a million words! So I suggest you check out the video, since no matter how much I write or how many pictures I post, some instructions can be better understood by watching the video. So yeah watch the video, trust me the background music is cool, and my freakish accent in English might also interest you. Oh, by the way if you watch the video my views on youtube will increase, and it will boost my ego to post more electronic projects on internet.

Step 2: Structure of This Poorly-written Instructable.

So the instructable is going to be divided in a few sections to make it easier for you to navigate or skip steps that you don't need to view.

1) Step 3: Things you will need to make the circuit are discussed there.

2) Step 4: The schematic is given.

3) Step 5&6: Describes the schematic, and how the components work together to make the circuit work. If you are a beginner in electronics, you should look at it.

4) Step 7-16: The structure and how to make the hand-crank mechanism is explained in these steps.

5) Step 17-22: The circuitry and soldering and everything else is in there.

6) Step 23: Putting everything together.

7) Step 24 to the end: Everything about testing the circuit, improving it, troubleshooting and exchanging goodbyes.

Step 3: The Ingredients Needed for the Dish:

To make it you will need:

1) A DC motor with gears. This is definitely the most important, but the hardest part to find out of all. Your options are to either 3d print the gears if you only have the motor. Or you could take apart toy cars, remote control cars, electronics toys with arms that move automatically etc. The reason we need gears is to increase the number of times we can rotate the motor. With our bare hands we could make the motor rotate a few times before we get tired, but the gears help us rotate the motor more than 50 or 100 times with only rotation of our hand. So the gears are essential, since we want to rotate the motors as fast as possible without having to amputate or arms afterwards.

2) 4 General Purpose Diodes. Example : 1N4148.

3) 2 Supercapacitor of around 1 Farad or larger. (The larger the capacity in Farads, the longer it will take to charge to bright light, but the charge will last for a longer time. So it's almost like buying a larger tank, it take more water to fill up a larger tank but more water can be stored in the larger tank.) Capacitors can be expensive, I bought the 1 F capacitors in a pack of 10 for 5 dollars, but that was from ebay. On most websites supercapacitors can go up to 2-5 bucks each, so check out for a good quality one at a reasonable price. Make sure the capacitance is in farads, not uF which are basically a million times smaller than a farad.

4) A switch. Any switch works, as long as you don't go to fancy with all the TPDT or some relay type stuff. Simplicity is the key for switches, because well, switches are simple themselves.

5)A perfboard. You could use a breadboard to test out the circuit, but then again I was quite sure I would want to keep the circuit so I soldered it on a perfboard. There are many variations, you could with veroboards, stripboards, surfboards and even the fancy "Printed Circuit Boards" if you have the resources to do so. But I am a simple man, I see a simple circuit, I build it on a simple perfboard.

6) A White LED. I tend to use white LED to look at dark rooms, but if you wish to run a disco with this, then feel free to throw in the multi colored LEDs as well.

7) A piece (sheet) of hard plastic.

8) Plastic refill of a pen.

9) A few screws and nut bolts. I am really unsure of their sizes, but I guess you could estimate or use any size as long as you change a few other measurements according to your needs.

Tools needed are:

1) Pliers.

2) Soldering iron

3) Hot glue gun

4) Scissors

5) Drill machine.

Alright, we have all the stuff we need, now turn on the background music and get to work.

Step 4: So Here's the Recipe!

So here's the schematic of the circuit. And in case anyone doesn't know, a schematic is the basic diagram of the circuit, written with symbols for the electronic components. If any of you don't know a few of the symbols here in the schematic, don't worry since I will also give details on the components in the next few steps.

Step 5: So How Is Our Circuit Going to Work?

There are four main parts of the circuit as shown in the diagram. There is a power or current source, there is a converter to convert the power into usable form, there is a section that stores the current, and then there is the load which uses the stored current.

In this circuit, the power source is going to be a motor. So how exactly can we use a motor to produce electricity? The answer lies in Faraday's law of Induction which states, "The induced electromotive force in any closed circuit is equal to the negative of the time rate of change of the magnetic flux enclosed by the circuit." This law doesn't really help to understand much, so let me give you a simpler version of his words that relates to our circuit. Basically when you have a change of magnetic field near a wire you produce electricity in the wire. The faster the change, the higher the voltage you produce. So you could move a magnet near a wire really fast and you will see some electricity being produced. But the key word here is 'Some' electricity being produced.

So we have a few problems as of now:

1)You need a really tight and large coil of wire to rotate or move near a strong magnet to produce good amount of electricity.

2)Electricity produced by induction or by moving magnet near a wire is A.C. or Alternating current. Most household batteries or capacitors stores D.C. or Direct Current, which is exact opposite of A.C. So we need to convert whatever electricity we make by induction from A.C. to D.C.

3)There are many options to choose from as to what we could use to store electricity. So we have to decide what to use.

Solution to problem 1: So when you were a child, if you ever dreamed of being an engineer then you might have taken apart quite a few motors from toy cars. If you did so, and never managed to put them back together, you would know that motors have a round thingy in the middle and magnet on the side. That round thingy in the middle is called the armature. It is made up of iron plates and many meters of copper wire tightly coiled around it. So we met the solution to the first problem, we found something with wire and magnet, and the best part is that we could rotate the armature or the coil of wire really easily.

Solution to problem 2: So A.C. electricity can be converted into DC electricity by various means. The wall adapters all have to convert AC to DC along with reducing the voltage. So if you take apart wall adapters of wide array of electronics, you will somehow always manage to find four diodes placed side by side. So the solution to our problems would be the rectifier circuit! The rectifier circuit is basically 4 diodes connected together. Also it is very cheap, and easy to make. We could go all fancy by adding capacitors to smooth out the output spikes, but for our simple circuit why bother?

Solution to problem 3: So have you ever used capacitors in circuits? No? Well capacitors can store electricity, and guess what, they can charge up much faster than most batteries! And they make the circuit look somewhat fancy, so we can't go wrong with that.

Step 6: So Let's Introduce Ourselves With the Components!

Motors: So we know a little about motors I hope. You don't really need to know how a motor works to make this circuit. But still it doesn't bother me much to tell a little. The motor has coils of wires and magnets. When electricity is flowed into the coil of the motor, the coil produces a magnetic field which repulses the magnet's magnetic field. If you ever played with magnets, you know opposite ends attract and same ends repel. Well that same repulsion and attraction is used to pull and push the armature and make the motor move. On the schematic the motor is mention as 'M' in a box. Also the polarity of the motor doesn't matter much in this circuit.

Diodes: The symbol of the diode looks like an arrow being blocked by a wall. That exactly what the diode does infact. It lets electricity flow in the direction of the arrow, but stops it from flowing backwards, in terms of conventional current. You don't need to know what conventional current is, except for the fact that our ancestors in electrical fields screwed up in theory of which direction electricity flows. Anyway, on the diode the end with the stripe is the negative end.

LED: Light Emitting Diodes are basic diodes that produce light when electricity is flowed through them. So the symbol is basically a diode with two arrows pointing outwards (shows flow of light). The longer lead is the positive.

Capacitors: Most capacitors have a longer lead that is positive. The symbol of a capacitor is just two lines placed side by side, the curved line is the negative end. Oh, the symbol of the capacitor also shows what the capacitor is basically. The capacitor is just two conductive plates separated by a insulator. A capacitor can store electricity in those plates, just like a battery. But the problem lies in the capacitance and the breakdown voltage. A capacitor can hold more electricity if the insulation is thinner. The capacity to store electricity is measured in Farads. But if the insulation is thinner, the insulation can easily break down if the pressure of electrons is too much (Voltage). So we have to make sure we do not exceed the voltage limit for the capacitors. The capacitor I am using is a 1 Farad capacitor with a Breakdown voltage of 5 Volt. My motor can produce about 7-9 volts when rotated at full speed with the gear, so it will easily breakdown the insulation of the capacitor. The solution is to use capacitors in series. So basically we will connect the positive of one capacitor of one capacitor to the negative of the other capacitor. Then the breakdown voltage will add up, and it will become 10 volts! So problem solved! Let's get started already!!!!!

But before we get moving, in the next few steps we will be creating the mechanical aspects of the circuit, like the hand crank and base etc. So we will get back to the circuits down the way later on.

Step 7: How Do We Mount the Motor on the Perfboard?

We are going to mount the perfboard onto the motor, so the circuit and the power source stays together, forever and after. The geared motor I had, had a metal plate. I drilled two holes on the metal plate, and then I drilled two holes at the same distance and radius on the perfboard. Now if we want we could mount the perfboard onto to the motor by simply using screws and hexnuts.

Step 8: Start Making the Crank Mechanism.

Take the gear on the top and mark two dots on opposite ends of the gear. Then drill two holes through those dots.

Step 9: How Do I Even Name This Step?

Take the gear and pass two screws of equal length through the holes. Attach two hexnuts to the screw, and tightly secure the screw to the gear by tightening the hexnuts. Use needle-nose pliers and screwdrivers to make the joint as tight as possible. Mark the distance between the screws. Let this distance be X.

Step 10: I Really Need to Name Some Steps.

Take a small piece of hard plastic sheet, and mark three dots in a straight line with distance of X between each of them and make holes through the dots. Refer to the picture for better understanding.

Step 11: Another Nameless Step

Take two hexnuts and insert them onto the screw, so that they reach about 1 or 2 cm from the end. Refer to the picture.

Step 12: Naming Steps Is Harder Than My School Homeworks.

Take the plastic sheet and insert the screws in the hole. Tighten the plastic two the screw using hexnuts.

Step 13:

Take a plastic ballpoint pen refill and cut out a section.

Step 14:

Insert a screw on the opposite ends of the other screws, through the plastic sheet. Tighten it to the plastic using hexnut.

Step 15:

Insert the plastic section we cut out earlier into the screw. Insert a hexnut in the end of the screw to make sure the plastic section doesn't come out.

Step 16:

Insert the top gear back in place, and your crank mechanism is ready!!!

Step 17: Back to the Circuitry!

I glued two capacitors back to back and attached a wire from positive to negative to connect it in series. Then I soldered the connection.

Step 18: Make the Rectifier!

Add four diodes to the perfboard, referring to the schematic for their polarity. Bend the leads of the diodes to keep them in place for now.

Step 19: Add the Load!

Connect the LED and switch according to the schematic.

Step 20:

Add the capacitors according the schematic. Solder the connections made so far.

Step 21: Final Step to Our Circuit!

Add the motor and solder the wires and done!!!

Step 22: Make the Landscape Cleaner!

Take a pliers or scissors or wire clippers and cut off excess leads since they might cause shorts. Now hotglue the capacitor in place, and apply a bit of hotglue to the bottom to avoid shorts.

Step 23: Let's Put It Together!

Remember we made holes in the motor plate and perfboard so that we could mount them? Now is the time for them to shine! Inset screws through those holes and tighten the motor and perfboard using hexnuts to hold the screw in place. We are done!

Step 24: Test It Out!!!

Now take the hand-crank and rotate it for a few times. Then turn on the switch and booommmm. It lights up. The light is actually brighter than my future.

Step 25: Trouble-shooting!

So in the next few paragraphs I will try to solve a few of the problems you might be facing while making it.


Solution: Calm down because I don't have either the patience or the sadistic nature in me to make someone waste hours of their youth to make a fake circuit. Let's slow down and get along with the rest of the problems. ( This happened to me countless times on youtube, people blaming me for their circuit not working.)

Problem 2: The Circuit doesn't work, would you help me fix it?

Solution: Now this is a better way to express your opinions and needs. Alright the circuit may not be working due to several reason.

Did you make your connections properly according to the schematic? Check it. If the connections are right, check whether you made soldering bridges. (accidentally connecting more than one connection by solder overflow). Did you insert the capacitor of proper polarity? Check with a multimeter to see the continuity of each capacitor, if there is continuity between the poles of one of the capacitors, then that capacitor needs to be replace, since the capacitor broke down upon reaching the Breaking Voltage.

Is the motor big enough for the purpose? Most small motors tend not to work, since they produce less electricity due to their lesser amount of coils.

Problem 3: The light doesn't stay lit for long or the light is too dim!

Solution: Is the capacitor's value over 1 Farad? The lower the farad rating, the less the charge it can hold.

Are there shorts in the bottom of the circuit? That could be leaking excess energy from the circuit.

Also choose a bigger LED to make it brighter. The motor can be switch for a bigger motor for higher voltage output and also brighter light.

Problem 4: My light keeps flickering, and works only when I rotate the motor!

Solution: May the lord be on your side to help you out through tough times. Amen.

Step 26: Can I Make It Better?

Of course you can! Believe in yourself, your imagination is your own limit!

Alright now that we are done with the inspirational speech, lets begin on the improvements you can make.

1) Make a case to make it look decent.

2) Add a stepper motor instead of the DC motor.

3) Use a better crank mechanism.

4) Use capacitors of higher value.

Alright guys, that's it from me for this instructable. I hope you find the instructable useful in making your own rechargeable flashlight. Watch the Youtube video and subscribe to support me. Also leave any comments or thoughts on what you thought about the project. Let me know if you want me to build something. See you in my next instructable! Thanks for viewing this instructable.

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    8 Discussions


    Question 10 months ago on Step 26

    sir, I really appreciate that you posted a step by step procedure of this kind of flashlight. But I want to improve ours by adding a blinking feature in your Rechargeable Flashlight With Hand-Crank Generator. how can we do it? is it possible sir ?


    Question 11 months ago

    How much time this will turn the LED on ? Love the project !


    2 years ago

    How do you count 2 to

    argha halder
    argha halder

    Reply 2 years ago

    I didn't quite understand what you meant. Sorry :(


    3 years ago

    I love huge capacitors!


    3 years ago

    Even if a Led seems to have a "zener" behaviour, a resistor is needed in serie with it or it will be rapidly destroy due to the overcurrent. Two capacitors in serie divide by 2 the overall capacity and multiply by 2 the eligible voltage. As yours are 5.5V, and a white Led forward voltage around 3.5V, you could put them in parallel which will double the lighting time without any issue but you'll have to limit the voltage with a regulator. Anyway, you must add a regulator to protect the components.


    3 years ago

    Very good instructable.
    Awesome job w the super caps.
    It could sustain longer 'on time' with this peak detector circuit.


    Reply 3 years ago

    This was just found and it may help others with their cicuits.