Made of a simple microcontroller, plastic bottle, and other basic electronic components, this lantern can help moderate battery usage for lighting.

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Build-it: Dimmable LED Lantern
GOALS:
o Paticipants learn to solder.
o Particpants understand how electricity flows.
o Participants learn about pulse width
modulation, a method for controlling the
electric power provided to a device
TIME:
4 hours
PREPARATION:
Collect and distribute materials and tools.
Set up soldering stations.
Make a lantern to discover what participants might find difficult.
Review and/or print Build-It insructions.
The wire can be pre-cut into two 2 inch sections per person, but not stripped, for
practicing soldering. It is possible to use two bare wires as the pushbutton and to not use
a socket to bring down cost and number of materials. Depending on the type of plastic
container used, either a drill or a knife is needed to make holes in the plastic.
Organize the tools into sets to be distributed during the introduction: Make sure the
soldering irons, solder, needle-nose pliers, and wire strippers are distributed around the
room and that the soldering irons are turned on. For each seat, distribute one set of parts
(LEDs, battery pack, microcontroller, socket, pushbutton) and make sure everyone also
has around a foot of wire and a plastic container.
ROOM SET-UP:
Tables with seating distributed so that people can reach the soldering irons.

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TOOLS MATERIALS*
Item Amount Cost
Wire
Strippers Solder ~ 12 mm minimal
Needle-nose
pliers
Wire ~ 300 mm minimal
Drill or Knife
or Box cutter AA batteries 2 $1
Soldering
Iron
AA Battery
Holder
1 $1
Hot Glue
Gun
Microcontroller
1 PIC
10f200 $0.50
(optional) Drill with
various bits
Electrical tape ~5 in minimal
(optional)
Pencils and
Paper Pushbutton* 1 $0.50
(optional) String White LEDs 3 $1
(optional)
Putty for
hanging
things on
walls
Plastic bottles 1 Free
Socket* 1 $0.10
Total cost = $4.10 *optional

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1. What is a Build-It?
A Build-It is a lesson where people make a small technology and learn some workshop
skills. Everyone will build together, step by step. As you build the technology, you will
learn good techniques for handling metal and wood. Each member will have an
opportunity to learn these hands-on skills by using some tools and materials. At the end
of the Build-It, you will have had some practice using tools and also have a technology
for you to take home.
A NOTE ON DESIGN:
These instructions will describe one way to make a lantern. As long as the conections in the
circuit are preserved, you can arrange the components in any way and make them fit in a
variety of containers. Encourage particpants who want to devote more time (an extra two
hours) to choose a container they want and design the circuit to fit inside. Some examples are
shown at the end of the document.
2. What is a dimmable LED lantern?
When a light gives more light, it uses more power from the battery. This means that you
waste power if you only need a little bit of light for the task, but you use a lot of light. By
having different brightness modes, you can increase the battery life. This lantern uses a
microcontroller to manage the different brightness modes of the LEDs.
• Inform participants that the
microcontroller fits in the
socket, so all their soldering
should be to the socket.
• Explain that the LEDs and
the microcontroller/socket
will not work if they are
backwards, so participants
should be sure to pay
attention to the long and
short legs of the LEDs and to
which way is ‘up’ on the
socket, as shown by the half
circle notch.
• Explain that the socket’s pins
are fragile. If you bend,
twist, or pull them, they will
break, and you will have to
start over.

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3. Setting up the Build-It
• Introduce each major part: Batteries, LEDs, microcontroller, switch, container.
• Encourage participants to engage fully. Ask, “Why?” “Where?” “What?” “How?” at
any time during the session
• Work slowly and carefuly, take the time to set up each solder joint with the wall putty,
and double check that you are making the right connection.
• Be careful of the hot glue guns and soldering irons. They can burn you, and will burn
the table if you put them down no in their holder.
• If particapants want to experiment with designing the light to fit in a container other
than a water bottle, encourage them to do so!
• Review how the technology works by explaining how to use it and what the major
parts are.
4. Practice Soldering (15 minutes)
Tools Materials
Steps
1. Strip one end of each 2’’ wire
piece.
SHOW THE PARTICIPANTS HOW TO PROPERLY STRIP WIRE
o Explain that they must use the hole that corresponds to the wire size we are using, and
specify the wire size.
o Explain that you want to strip 1 to 2 cm of wire.
o Demonstrate how you insert the wire into the hole, squeeze, and strip off the plastic
coating.
2. Twist the wires together

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SHOW THE PARTICIPANTS HOW TO MAKE A MECHANICAL WIRE CONNECTION.
o Explain that you can twist the wires together, enough that they hold together on their
own.
o You can also make two hooks with the wire ends, and hook them together. This concept
is easily shown using two fingers.
o As you walk around, make sure everyones wires are secured together, not just touching.
3. Secure the joint to be soldered.
STRESS THE IMPORTANCE OF THIS STEP.
o To stabilize the wires, add some wall putty to the table and place the wires in it
o Explain that you will need one hand to hold the soldering iron and one hand to hold the
solder, so the wires need to already be secured.
4. Solder the joint
EXPLAIN HOW TO SOLDER:
o The first step is to get a little bit on solder
on the tip of the iron.
o Then touch the soldering iron tip to one
side of the joint.
o Touch the solder to the other side of the
joint.
o The solder and iron should not be
touching at this time.
o The solder should flow towards the tip,
encasing the joint in shiny metal.
o Check to see if anyone has a dull joint.
This means the solder was not hot enough
and they need to reheat their wires.

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5. Understanding the basic circuit (15 minutes)
Once everyone is done soldering, bring the group back together to hear the explanation of
how the circuit works.
EXPLAIN THE BASIC CIRCUIT
o People will build more carefully when they understand how the circuit works and why
short circuits should be avoided
o Electricity must travel in a circle.
o The electricity begins its journey at the positive end of the battery. It flows through the
wire and arrives at the microcontroller. It exists the microcontroller and goes into the
LED where it makes light.
o Now, the electricity must return to the battery. It travels through the wire and into the
negative terminal of the battery, finishing its circular journey!
LED DETAILS
o Explain again that the LEDs cannot be put in backwards. The short leg must be
connceted to the negative terminal of the battery by wires.
o The two legs of the LED must not touch. If they do, the electricity will flow through the
connection without ever making any light
MICROCONTROLLER DETAILS
o The legs of the microcontroller must not touch eachother
o The microcontroller cannot be placed in backwards, so pay attenetion to the half circle
indent.
POTENTIAL WAYS FOR THE CIRCUIT/CIRCLE TO BREAK:
THESE DETAILS ARE NOT NECESSARY TO SHARE, BUT FOR YOUR REFERENCE
o Short circuit – the circuit is closed before it is supposed to be. This could damage the
batteries, leds, and microcontroller.
o Loose connection – the circuit has simply been broken. This often occurs when the pin
of a socket breaks off. There is no way to repair this, and the participant must begin
again with a fresh socket
o LEDs or Microcontroller are backwards.
o Dead battery – check the voltage of the battery to ensure it is still good.
o Batteries inserted into the holder backwards.

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6. Building the Circuit (3 hours)
All the components except the plastic bottle will be used in this section.
Tools Materials
Steps:
1. Bend the short leg of one
LED
2. Bend both of the legs out.
3. Repeat with the other LEDS and
solder the short legs together.
4. Touch the black wire from the
battery pack to the short leg of
the LED’s and the red wire to
their free leg to test them.
When you are done testing,
remove the batteries
Make sure to insert your
batteries properly- the negative
terminal touches the spring.

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5. Bend the pins on the socket so
they are flat. Cut off pins one
and six on the socket. Pins are
numbered clockwise starting to
the right of the indentation. Pay
careful attention to the
indentation and which way is
up.
You will not be using these pins.
6. Solder the free, long leg of one
LED to pin four of the socket.
Be sure to set up your joint
carefully with the wall putty
before soldering.
7. Attach the free, long legs of the
last two LEDs to pins three and
five of the socket.
8. Strip a section in the middle of
the black wire.
Be careful when stripping the
wire as not to break it. If it
breaks, that is fine; you will just
have to make two solder
connections. In step 10.

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9. Solder the red wire to pin 2 of
the socket.
10. Solder the stripped section of
the black wire to the short legs
of the LEDs.
11. Solder the end of the black wire
to pin 7 of the socket.

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12. Cut a piece of spare wire to
around 2 inches, and solder it
to pin 8 of the socket.
13. Cut a second, 2 inch piece of
wire, and solder it to the short
legs of the LEDs.
14. If you are using a switch, solder
the switch to the two wires you
just cut.
You can also just touch the
metal parts of these wires
together briefly, and it will
work as a switch.
NOTES ON SWITCHES
If the switches have four legs, the participants should solder to legs that are diagonal from
eachother.

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15. Insert the microcontroller.
Makes sure it is not upside
down.
16. Insert the batteries and test the
lantern using the switch.
Make sure to insert your
batteries properly- the negative
terminal touches the spring.
17. Hot glue the circuit onto the
outside of the battery pack.
If hot glue is not available, use
electrical tape to secure the
circuit.
NOTES ON SECURING THE CIRCUIT
The pins on the socket are very fragile. When securing the circuit, we want to ensure that the
pins are fasted down to the plastic battery pack so that they won’t twist or bend if the light is
shaken around.

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7. Preparing the Water bottle (30 minutes)
Ensure that the waterbottles being used are mostly dry on the inside.
Tools Materials
NOTES ON SAFETY
Remind particpands that the knives/scissors being used are sharp and encourage them to point
the blades away from themselves while cutting the plastic. The cut plastic edges can also be
sharp, so particpants should handle the bottles with care.
Steps:
1. Cut the top of the water bottle,
making a hole big enough the
easily insert the circuit.
Please be careful.
2. Have paricipants decide where
in the bottle they want the
circuit to go.
Some examples are shown at
the end of the instructions.
3. Cut a hole for the switch, if
nessicary for your design, in the
bottle.

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4. If they want their circuit to be
secured in a certain place, they
can poke holes in the bottle,
and weave a net of string to
secure it. They can also use
string to hang the bottle up.
Be creative, but remember that
you will have to take the circuit
out to change batteries at some
point.
5. Secure the circuit inside the
bottle and thread the switch
out.
Congratulations, you have
finished your lantern!
TIPS FOR MORE CREATIVE DESIGNS OR CONTAINERS
o If you are using harder plastic, a drill will make things easier.
o Have participants sketch out their design before building it, make sure to keep the
dimensions of their container in mind.
o Check in with them frequently to make sure their connections are following the diagram.
o It is especially important to set up solder joints before soldering.
o Electrical tape can be used to prevent two wires that are close to eachother from
touching.
o They should still encase the base of their socket in hot glue to secure it.
o Remember there are different colors of LEDs you can use
o As you beuild the lantern, be aware that LEDs give light in a particular direction
Build-Its are published by IDIN. The
International Development Innovation
Network (IDIN) is a consortium funded
through USAID’s Higher Education
Solutions Network (HESN) that supports
leading universities to catalyze the
development and application of
innovative science, technology, and
engineering approaches and tools to
solve some of the world’s most
challenging development problems.
The dimmable LED lantern featured here was designed with contributions from participants
in the International Development Design Summit. The document was created by Erin Pierce in
collaboration with IDIN representatives at UC-Davis and MIT.

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Examples of other Lantern Designs