Electric Play Dough Project 2: Rig Your Creations With Lots of Lights!
|Time Required||Very Short (≤ 1 day)|
|Prerequisites||You should understand the Introduction material in Light Up Your Play Dough!—the first project in this series—before doing this project.|
|Material Availability||Kit available for purchase from our partner Home Science Tools. See Materials tab for details.|
|Cost||Low ($20 - $50)|
|Safety||Never connect the battery pack's terminals directly to each other; this is called a short circuit and can make the batteries and wires get very hot. Do not connect the LEDs directly to the battery pack without using play dough; this will burn out the LEDs.|
AbstractHave you tried our first electric play dough project, and now you are looking for more to do? Do you want to learn more about circuits and add even more lights? Check out this project for part 2 of our play dough circuits series!
ObjectiveUse play dough and batteries to create simple series and parallel circuits that light multiple LEDs (light-emitting diodes).
Ben Finio, PhD, Science Buddies
This project idea is based on work done by Dr. AnnMarie Thomas at St. Thomas University.
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Last edit date: 2019-03-06
In Project 1 of our play dough circuits project series, you learned about the basic ideas of closed, open, and short circuits. If you need to review this information, you can always go back to the Light Up Your Play Dough! background section. You can also learn more about electricity in the Science Buddies Electricity, Magnetism, & Electromagnetism Tutorial. In Project 1, you only learned how to hook up one light to your creation. Imagine how cool your creations can be if you hook up lots of lights—this project will show you how!
In order to do this, first you will need to learn about two new kinds of circuits. The examples will explain a circuit that has one battery and three lightbulbs. There are different ways to connect multiple lightbulbs to a battery: in "series" or in "parallel." We will explain what these words mean next.
In a series circuit, the lightbulbs are all connected in a row, and form a single loop. The path the electricity takes from the positive end of the battery to the negative end has to go through each lightbulb. This is shown in Figure 1.
Figure 1. Three lightbulbs connected to a battery in series. Notice how there is only a single "loop," and the path that the electricity takes (represented by the yellow arrows) has to go through each lightbulb in order.
In a parallel circuit, the lightbulbs are connected next to each other, and form multiple loops. Any path electricity takes to get from the positive end of the battery to the negative end only goes through one lightbulb. This is shown in Figure 2.
Figure 2. Three lightbulbs connected to a battery in parallel. Notice how there are multiple "loops," and any path the electricity takes (represented by the yellow arrows) only goes through one lightbulb.
One important thing to know is that the shape the wires connecting the lightbulbs makes does not matter. In other words, you can move the lightbulbs and wires around, but as long as the connections stay the same, you will not change if a circuit is series or parallel. Look at Figures 3 and 4; the lightbulbs have been moved around (and the shapes the wires make have changed), but they are still the same kind of circuit as Figures 1 and 2.
Figure 3. The lightbulbs in this figure have been rearranged relative to those in Figure 1. However, there is still only one path for the electricity to take, which goes through all three lightbulbs, so this is still a series circuit!
Figure 4. The lightbulbs in this figure have been rearranged relative to those in Figure 2. However, there are still multiple paths for the electricity to take, and each path only goes through one lightbulb, so this is still a parallel circuit!
So, now that you know the difference between series and parallel circuits, it is time to apply this knowledge to your play dough circuits! First let us see what happens when we try hooking up first one, then two, then three LEDs (light-emitting diodes, which are a type of tiny lightbulb found in many electronic devices) in series using play dough circuits. This is shown in Figure 5.
Figure 5. (From left) One, two, and then three LEDs connected to the battery pack in series using play dough circuits. The LEDs get much dimmer as each new LED is connected.
Uh-oh! Do you see a problem in Figure 5? The LEDs get dimmer each time a new LED is plugged in. With only three LEDs, you can barely see them light up at all! This is certainly going to be a problem if you want to hook up lots of lights to your creation. So, let us find out what happens if we connect the three LEDs in parallel instead. This is shown in Figure 6.
Figure 6. (From left) One, two, and then three LEDs connected to the battery pack in parallel using play dough circuits. Each new LED is just as bright as the previous one.
That is much better! In Figure 6, all the LEDs are the same brightness. This means that when you hook lots of lights up to whatever you build, you need to connect them in parallel. Now, why does this happen? Because in a series circuit, some electricity is "lost" each time it goes through an LED. So, by the time the electricity has already gone through one or two LEDs, there is not enough energy left to power the rest of them. In a parallel circuit, the electricity goes straight from the battery to each LED without losing energy first. This allows you to light up more LEDs (you'll find a more detailed explanation in the Technical Note section, but only if you are curious; you do not need to understand that information to do this project).
One more important thing to note: even in parallel, your LEDs will start to get dimmer if you make a very big structure or have very long sections of conductive Play-Doh, and use lots of LEDs. This is because some electricity is lost as it flows through the Play-Doh, and there is a limited amount of electricity that the batteries can supply. You can see this in Figure 7; the LEDs that are closer to the battery wires are brighter than the ones that are far away.
Figure 7. All ten of these LEDs are connected in parallel. The electricity does not have to travel as far to get to the LEDs that are closer to the battery pack, so those LEDs are brighter. The LEDs on the far right are dimmer because the electricity has to travel much farther to get to them.
Now that you are an expert on series and parallel circuits, you are ready to start making designs with lots of lights!
You may be wondering why the LEDs stay bright when you connect three of them in parallel, but barely light at all when you connect three in series. After all, you are connecting the same three lights to the same battery pack; shouldn't they be the same brightness either way?
It turns out this is because of how voltage works in series and parallel circuits. The battery pack uses four AA batteries, and supplies 6 volts (abbreviated as V). Each LED requires a "voltage drop" of about 2.5 V to fully light up. So, if you connect three LEDs in series, that is 3 × 2.5 = 7.5, which is more voltage than the battery pack can supply! This is why the LEDs are so dim. However, if you connect three LEDs in parallel, they are each connected directly to the positive and negative terminals of the battery, with the full 6 V available to power each one of them. So, you can attach many more LEDs in parallel and they will remain at full brightness.
Terms and Concepts
- Closed circuit
- Open circuit
- Short circuit
- Series circuit
- Parallel circuit
- What is the difference between a series and a parallel circuit?
- Can you draw your own series and parallel circuits, each with four lightbulbs?
- Which type of circuit is better for hooking up multiple LEDs in your play dough circuit: series or parallel?
Here are some additional resources on series and parallel circuits.
- The Physics Classroom. (n.d.). Series Circuits. Retrieved February 8, 2013, from http://www.physicsclassroom.com/class/circuits/u9l4c.cfm
- The Physics Classroom. (n.d.). Parallel Circuits. Retrieved February 8, 2013, from http://www.physicsclassroom.com/class/circuits/U9L4d.cfm
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Electric Play Dough Kit
available for purchase from our partner
Home Science Tools.
- 4xAA battery holder
- Piezoelectric buzzer
- Jumbo LEDs (25 total — 5 each in red, green, white, yellow, and blue)
- White insulating dough (3.5 oz)
- Red, blue, and green conductive dough (3.5 oz each)
- AA batteries (4, not included in the kit).
- Optional: in addition to the dough included in the kit, you can make your own conductive and insulating dough (for example, if you want other colors). See Electric Play Dough Recipes for materials and directions for making your own dough. You can also use store-bought Play-Doh® (replaces conductive dough) and modeling clay (replaces insulating dough).
Recommended Project Supplies
- Optional: if you are making your own homemade conductive and insulating in addition to using the dough in the kit, follow the instructions on Electric Play Dough Recipes.
- Insert the four AA batteries into the battery pack that came with your kit.
- First, do an experiment to see how many LEDs you can connect in series.
- Start by connecting one LED to the battery pack using Play-Doh. Remember from Project 1 in our series that you should use insulating modeling clay between the conductive Play-Doh pieces to prevent short circuits between the LED leads.
- Now, add a second LED in series, like in Figure 5 from the Introduction. Do the LEDs get dimmer?
- Add a third LED in series. Do they get even dimmer?
- Continue this process until the LEDs do not visibly light up at all.
- Now, do an experiment to see how many LEDs you can connect in parallel.
- Start by connecting one LED to the battery pack using Play-Doh. Remember from Project 1 that you should use modeling clay between the Play-Doh pieces to prevent short circuits between the LED leads.
- Now, add a second LED in parallel, like in Figure 6 from the Introduction. Do the LEDs get dimmer?
- Add a third LED in parallel. Do they get dimmer?
- Continue to add LEDs in parallel. Do they eventually get dimmer? Can you make them brighter by keeping them very close together?
- Now, plan out the shape that you want to make (drawing it first is a good idea) and how you want to add lights. Remember that if you want to use a lot of LEDs, you will need to connect them in parallel, and that the actual shape of the Play-Doh does not matter, as long as each LED has its own "loop" formed with the battery. You might need to use modeling clay in some places to prevent a short circuit. Figure 8 shows an example design.
- Build your shape and start adding lights! Remember from Project 1 that LEDs only work in one direction (the longer lead should be connected to the positive side of the battery pack, with the red wire), so if one does not light up, try flipping it around. If your circuit is not lighting up at all, make sure you remembered to turn your battery pack on, and that you do not have a short circuit somewhere. If you are still having trouble, you can refer to our FAQ section.
Figure 8. An example design with four LEDs in parallel. The wings of the butterfly are made from conductive Play-Doh and the body in the middle (yellow) is made from insulating modeling clay.
For troubleshooting tips, please read our FAQ: Electric Play Dough Project 2: Rig Your Creations With Lots of Lights!.
If you like this project, you might enjoy exploring these related careers:
- If you are comfortable with the information in this science project, you can move on to our third play dough circuits science project: Electric Play Dough Project 3: Light Up Your Sculptures!. You will use your knowledge from the first two science projects to build a light-up three-dimensional sculpture.
- Curious about the chemistry behind electric play dough? Research what ingredient or ingredients make the play doughs conductive or insulating, then try changing the recipes to see what it does to the conductive and insulating properties of the play dough. For instance, how much salt do you need for the play dough to conduct electricity?
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Frequently Asked Questions (FAQ)
This guide contains answers to some frequently asked questions for the "Squishy Circuits" project idea series:
If you are making a new batch of dough, the best way to prevent these problems is to follow the directions carefully and measure the appropriate amount of each ingredient. Some steps require you to slowly add small amounts of water until the desired consistency is formed, instead of adding the entire amount all at once.
- Make sure you properly inserted the batteries into the battery pack. Each battery is marked with a "+" symbol on one end. Make sure these symbols line up with the "+" symbols on the inside of the battery pack.
- Make sure you turn the switch on your battery pack to the "on" position when you are testing your circuit.
- Make sure your conductive dough is tightly secured around the metal leads for your battery pack. If you wiggle them around a lot and they come loose, then they will not be in good contact, and it will be difficult for electricity to flow.
- If you have a multimeter, you can use it to measure the voltage from your battery pack. Four AA batteries should provide about 6 volts (V). If the voltage is lower than 6 V, your batteries might be dead. Consult the Science Buddies Multimeter Tutorial if you need help using a multimeter.
- Remember that LEDs have a polarity, meaning they only work in one direction. The longer LED lead should be connected toward the positive side of your circuit, which is the side with the red wire protruding from the battery pack. If one LED in your circuit is not lighting up, but others are, you probably just have that LED plugged in backwards. Try reversing its direction and see if it lights up.
- Make sure your conductive dough is tightly packed around the metal leads for your battery pack. If you wiggle them around a lot and they come loose, then they will not be in good contact, and it will be difficult for electricity to flow.
- Make sure you do not have a short circuit. For more information about short circuits (including pictures and diagrams), refer to the Introduction of the first Squishy Circuits project.
- If your circuit has two or more LEDs, make sure they are wired in parallel and not in series. Wiring multiple LEDs in series will quickly cause them to become very dim. For more information about the difference between series and parallel circuits (including pictures and diagrams), refer to the Introduction of the second Squishy Circuits project.
- Make sure you are not using very long pieces of conductive play dough to connect your battery terminals to your LEDs. The conductive play dough has a fairly high resistance, which causes the voltage to drop as electricity travels through it. If you use very long pieces of conductive dough, the voltage might drop so much that the LEDs will not light up. To learn more about voltage and resistance, check out the Science Buddies Electronics Primer Introduction.
- Never connect your LEDs directly to the battery pack leads without using conductive dough in between. Connecting LEDs directly to the battery pack will cause them to burn out; too much current will flow, permanently destroying the LED. If you have LEDs that do not light up at all despite trying all the steps above, you might have accidentally burned them out at some point.
- In general, follow the same steps as in FAQ 3. For a big circuit, it is possible to have a short circuit in only part of the circuit; some LEDs might light up, while others stay dark. You might have also accidentally wired some LEDs in series, and some in parallel. Remember to always avoid short circuits, check the direction your LEDs are plugged in, and make sure your LEDs are wired in parallel.
- You can test individual parts of your circuit, one at a time. You can do this by breaking them away from the rest of your circuit and connecting them to the battery pack separately, or by sticking the battery pack leads into different parts of your circuit. This will let you identify problem areas in your circuit.
- Remember that it is possible to burn out LEDs by connecting them directly to the battery pack. If nothing else works, try swapping in a new LED.
- Both types of homemade dough (conductive and insulating) should be stored in air-tight plastic containers or plastic bags. You can put it in the refrigerator to make it last even longer.
- The conductive play dough contains salt, so will last for several weeks or months if kept in an air-tight container. Eventually, you may still see spots of mold or bacteria growing on it.
- Insulating play dough contains sugar, which bacteria and other microorganisms thrive on. You may start to see mold or bacteria growing on it after several days or a week, but it will last longer if refrigerated.
- If your play dough develops spots of visible mold or bacteria, you should throw it away and make a new batch.
- Make sure you use short, thick lumps of Play-Doh to connect the buzzer to your battery pack. The buzzer requires much more electricity to operate than the LEDs. Long, thin strips of Play-Doh have a higher electrical resistance, making it difficult for enough electricity to flow through them.
- The buzzers have polarity, just like the LEDs. Their red wires need to be connected to the battery pack's red wire, and their black wires connected to the battery pack's black wire.
Ask an ExpertThe Ask an Expert Forum is intended to be a place where students can go to find answers to science questions that they have been unable to find using other resources. If you have specific questions about your science fair project or science fair, our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.
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Contact UsIf you have purchased a kit for this project from Science Buddies, we are pleased to answer any question not addressed by the FAQ above.
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Good Question I'm trying to do Experimental Procedure step #5, "Scrape the insulation from the wire. . ." How do I know when I've scraped enough?
Good Question I'm at Experimental Procedure step #7, "Move the magnet back and forth . . ." and the LED is not lighting up.
Bad Question I don't understand the instructions. Help!
Good Question I am purchasing my materials. Can I substitute a 1N34 diode for the 1N25 diode called for in the material list?
Bad Question Can I use a different part?
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