Today I am going to show you how to make a joule thief powered adjustable reading lamp. It is quite cheap and easy to build and is a fun way to put your soldering skills to the test. The lamp is not going to be as good as a really great branded lamp, but it is going to have some features and the D.I.Y look to it which you can modify. A few of the features of the lamp are:
1)You could change the brightness.
2)You could adjust the direction of the light flow by adjusting the neck of the lamp which is movable.
3)You have a switch to turn it on and off.
4)The lamp can run on any AA battery, even the ones that are not usable by other devices. The lamp uses very small amount of voltage, which is why the AA batteries that are running low on voltage can be used with this lamp.
Don't be scared by the number of steps. There are a lot of steps, as the steps are divided into small actions at a time to make it easier to follow. If you want to learn how the circuit works, go to step 23. For troubleshooting tips go to step 24.
Also you could watch the video to learn how to make it : https://www.youtube.com/watch?v=sI3R5k6ASxY
Step 1: Watch the Video to Learn How to Make It!
Step 2: Materials
To make the lamp, you are going to need the following things :
1)7 craft sticks or ice-cream sticks.
2) 3 Hex nuts and bolts of the same diameter.
3)A plastic cup 4)A reflective packaging. (Packaging for chips) The electronic components needed are:
1) Any NPN transistor. 2N3904, 2N2222A, BC337 etc are some common NPN transistor. But any NPN transistor should work.
2)A 1 Kilo Ohm potentiometer.
3)A toroid bead. So this might be difficult to find, but if you know where to look for it,you will find it easily. If you take a CFL bulb and take out its circuit, you will find a round bead wrapped in wires. That is the toroid. You could also find these toroid beads inside PC Power supplies. They will always have wires wrapped around them as they are used as inductors in many devices.
4)A 1 Kilo Ohm Resistor. ( Color code - Red, Black, Brown)
5)2 ultra-bright white L.E.D lights.
6)A 1.5 volt battery.
7) A switch
8)Two wires of about 1 foot in length and some extra wires for connections.
9)A bag of chips, or any packaging that has reflective covering.
The tools necessary to make this lamp:
1)A soldering iron.
2)A hot glue gun. (Any strong glue or epoxy could be used.)
3)A perfboard or veroboard for soldering.
4)A driller. I used a hand drill. Use a drill bit the same size as the nut.
6)A Battery holder. (If you don't have a battery holder then you will need- a craftstick, aluminium foil and a spring to make connection.)
Step 3: Preparing the Neck:
First of all take one of the craft sticks and cut it in half. Now take 4 craft sticks and the craft stick we just cut and draw a dot on each of their ends.
Step 4: Preparing the Neck (Part 2)
Now take the craft sticks, and using a hand drill, drill holes through the dots on the craft sticks. It should look like the ones in the picture.
Step 5: Preparing the Neck (Part 3)
Now take two craft sticks, and in between the end of those two craft sticks, put the end of another craft stick. Make sure the holes are lined up. Now take the bolt and pass it through the hole, and on the other end tighten it with the hex nut. It should look something like the one in the picture. You will notice, you can move the sticks freely, if you can not move the sticks, then you have to loosen the hex nut, or if the sticks are moving too loosely, you have to tighten the hex nuts.
Step 6: Preparing the Neck (Part 4)
Now create all the joints like the one shown in the picture. So there should be 3 joints, and 4 separate segments. Now take the end of the last craft stick ,(The long craft stick in the end) and cut the circular end to make the end flat like in the picture.
Step 7: Preparing the Neck (Last One!)
Alright, now take two pieces of craft sticks glue them in the center to make a cross. Now take the other Segments and joints we created before, and glue the flat end to the base or the cross. The neck is finally completed! Now we can move on to the circuit!
Step 8: The Circuit
So here is the basic circuit. You could modify it however you wish. There is the schematic. There is also a diagram provided which has quite a few problems as I did not know how to get the toroid in the diagram. In the next few steps I will show you how I put together my circuit. If you want to learn how the circuit works you could go to step 23.
Step 9: The Transistor!
So when you take the transistor and put it on a table, so that the flat side is facing up and the leads are towards you, the pins starting from the left to right is Emitter, Base and Collector. This format of pin, known as the EBC pin layout, is quite common for NPN transistors. But always check your datasheet to find out whats the layout for your transistor. When soldering the transistor be really careful not to heat it up too much. Transistors can burn down easily, so always be careful with transistors and mind their leads.
Step 10: Winding the Toroid
So first of all, take two wires of about 1 foot in length. Twist one of their ends together and then take the toroid bead and start to coil it. Coil about 6-10 times. Leave about 1 inch of wire on each end. When you are done coiling, you will end up with two pairs of wire. Lets name the black and red wire from one pair as A and B. Name the other two Black and Red wires D and C. Now take wire B and D and twist their ends. So we are basically swapping ends. Refer to the pictures to get a better understanding of the process.
Step 11: Preparing the Board
Take the perfboard or veroboard, and snap it in two little pieces. The pieces should be big enough to hold two leds and wires on one piece and transistors, resistors and a lot more wire on the other piece.
Step 12: The Voltage Booster Circuit
So first of all take the bigger piece from the two pieces of perf-board we broke. Now place the transistor, resistor and the 4 wires with the toroid inside the perfboard. Bend the leads in opposite directions to make them stay in place. Follow the schematic or diagram to do this. Also place two LEDs in parallel in the smaller piece of perfboard. Connect the piece with LEDs to the piece with transistor via two long wires.
Step 13: Solder!
Now solder the components and trim off excess leads.
Step 14: Adding the Brightness Control!
Now take the wire that is going from the Collector of the transistor to the Positive end of the LED, and split it right in between. Now solder the potentiometer like shown in the picture.
Step 15: Lets Make the Lamp Head!
To start of take the cup and cut it in half. Discard the top half, as we don't need the top half.
Now take the reflective packaging and cut it into a shape like shown in the picture.
Step 16: Lets Make the Lamp Head! (Part 2)
Take some glue, and glue the reflective packaging to the inside of the cup, so that the reflective side is facing inside the cup. This will help reflect light better in a straight direction.
Step 17: Lets Make the Lamp Head! (Part 3)
Now take the piece of perfboard, and measure it, and cut a hole on the bottom of the cup, so that it is big enough to to fit the leds. Now glue the piece of perfboard with LEDs to the cup, so the the LEDs are facing inside the cup.
Step 18: Lets Make the Battery Holder!
First of all, take the craft stick and cut off its round end. Wrap some foil around it and put a wire inside the foil so that wire can conduct electricity through the foil. Now take the spring and solder a wire to it. So now you have two ends of the batteries with two wires. One wire coming from the foil and craft sticks, and the other wire coming from the spring. Solder the wire from the spring to a switch. Solder the other end of the switch to a wire that goes to the perfboard's positive battery connection. Now solder the wire coming from the foil to the perfboard's negative battery connection.
Step 19: Lets Make the Battery Holder! (part Two)
Now on the cross or the base, glue the piece of spring with wires. Now glue the piece of craft stick with foil to the base, so that there's only enough space to hold a battery in between the spring and the foil wrapped piece of craft stick.
Step 20: Lets Put It All Together!
Glue the bottom of the cup to the top of the neck we created in the earlier steps.
Step 21: Lets Put the Circuit Together!
Now lets glue the potentiometer, the switch and the circuit board to the base of the lamp to finish it up. Also glue the wires to the side of the craft sticks so that they don't move around. Also you could make it better in a lot of ways if you want, for example by painting, by adding stronger base. If you want you could add some weight to the base, to make it more stable.
Step 22: So Here It Is All Finished!
This is how it should look once finished! Lets hope it works! Press the button switch to turn the lamp on. Rotate the knob on the potentiometer to increase or decrease the brightness. If this two functions work, then the lamp is working fine!
Step 23: So How Does This Work?
So now if you are interested in learning about this circuit, I will try to explain it in the way I think it works. Please make any corrections if needed, because I am not an expert at electronics and I am certain to make mistakes. So this lamp has the key circuit called joule thief circuit, which allows the 1.5 volt or less from the AA battery to run the lamp. The joule thief circuit has the transistor which does most of the work. The transistor works like a switch. The transistor has three leads, the E, B, and C. In NPN transistor, when a small amount of positive voltage is provided to the B or the base of the transistor it allows current to flow through E and C or Emitter and Collector. Then the toroid comes into play. The toroid core has something called an inductance, which means that it will create opposing magnetic field whenever the existing magnetic field changes. So when current goes through Emitter and Collector, the wire on the toroid tries to resist the change by creating opposing magnetic field which results in a electronic pulse that turns off the power supply to base of transistor. So there are no more current going through Emitter and Base, so the magnetic field collapses, causing the inductor or the toroid and the wires to create another more powerful pulse in the opposite direction, turning the LEDs on. The LEDs turn on for a moment. Now as the there is no supply to the base of transistor, positive voltage can once again go to the base and keep repeating the process, lighting up the led for a small moment each time. This happens so fast we don't even see the LED turning on and off. We just see it turned on.
The brightness controller is just a potentiometer. There are electronics named resistors, which just resist electrons from moving through it. So it is called resistor. A potentiometer is just a resistor with a variable resistance, which means its resistance can be changed. When we decrease the resistance of the potentiometer, it allows more electrons to go through and so the LED lights up brighter. So basically thats how it works. Lets hope it helped!
Step 24: Troubleshooting and How to Improve It?
Problem 1: The transistor is getting way too hot!
Solution: Use a heat sink case. Did you add the 1kilo Ohm resistor correctly? Because the resistor is really important to stop blowing up the circuit.
Problem 2: Well, the lamp isn't lighting up.
Solution: First of all I would check my connections to see if they were shorted somehow. I would then be sure that my transistor was of the right type. Make sure it is NPN, and make sure that the layout of the pin is correctly utilized in the circuit. Also the biggest problem I faced was with the toroid wire. It would only light up for moments when I would shake the wires. I found out it was because I did not swap wires when I was finished coiling the toroid. Be sure to carefully and neatly coil the toroid and also to carefully swap the pair of wires.
Well, I don't know of any other problems, but if you are facing more problems, then let me know, I will try to help up to my ability.
1)You could make a better, more efficient LED driving circuit.
2)You could change the neck and use a better materials and designs for the neck.
3)Make it good enough to accompany you through every book you read.
Also remember to watch the video to learn how to make it :Joule thief powered LampSo thats all! Lets hope you found it useful or fun. I would be more than grateful to receive any suggestions and it would be great if anyone can fix my mistakes. I am really sorry if I was not clear enough. Follow me for more projects. Thanks for reading my instructable! Have a great day! Good luck with the project!