Bristlebot Science Buddies Bibliography

Difficulty
Time RequiredAverage (6-10 days)
PrerequisitesNone
Material Availability A kit containing all the electronics parts needed for this project can be found in a kit from our partner Home Science Tools. Time required includes estimated time for shipping the kit.
CostAverage ($40 - $80)
SafetyNo issues

Abstract

You have probably heard about using renewable energy sources like wind and solar power to provide electricity to homes and buildings, as well as hybrid or fully electric cars that use less (or zero) gasoline. But what about solar-powered robots? As robots become more common, it is increasingly important to use "green" energy sources to power them. In this project, you will build and test a popular robot called a bristlebot — a tiny robot made using toothbrushes—that can operate on either battery or solar power, and investigate how well it performs in different weather conditions.

Objective

Compare the performance of solar and battery power for a bristlebot in different weather conditions.

Credits

Ben Finio, PhD, Science Buddies

Cite This Page

MLA Style

Finio, Ben. "Build a Solar-Powered Bristlebot" Science Buddies. Science Buddies, 3 Mar. 2018. Web. 14 Mar. 2018 <https://www.sciencebuddies.org/science-fair-projects/project-ideas/Robotics_p026/robotics/build-a-solar-powered-bristlebot>

APA Style

Finio, B. (2018, March 3). Build a Solar-Powered Bristlebot. Retrieved March 14, 2018 from https://www.sciencebuddies.org/science-fair-projects/project-ideas/Robotics_p026/robotics/build-a-solar-powered-bristlebot



Last edit date: 2018-03-03

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Introduction

Many of the devices you use every day require electricity to operate. Electricity can be supplied directly to devices that plug into wall outlets (like lamps and computers), and it can also be stored in batteries for cordless devices like television remote controls, cell phones, and even robots like the one you will build in this project! Modern life as you know it would not exist without electricity, but electricity comes at a cost. The electricity we use has to be created somehow, and creating electricity requires a source of energy.

One very common source of energy for creating electricity is burning fossil fuels, like oil and coal. Fossil fuels are being used up (mined or pumped out of the earth) faster than they are naturally replaced, so eventually we might run out of them. Burning them also creates greenhouse gases that contribute to climate change, and other pollutants that can harm the environment. Renewable energy sources are an alternative to fossil fuels. They get energy from sources that will not deplete, like the sun, the wind, or Earth's super-heated core. They also tend to be much cleaner and cause less pollution than fossil fuels.

Solar panels harness a big source of renewable energy: the Sun! They can create electricity from the Sun's rays, without creating any harmful emissions like fossil fuels do. You may have seen large solar panels on the roof of a house, but tiny solar panels are also used to power smaller devices like USB cell phone chargers or even miniature robots. In this project, you will build a miniature solar-powered robot, like the one shown in Figure 1. The robot is a type of bristlebot, a popular robot that gets its name from the fact that it uses toothbrushes as "feet."


Figure 1. A mini solar-powered robot.

Despite the clean, renewable nature of solar power, it does have some drawbacks. The power output of solar panels can drop dramatically when it is cloudy, and they do not work at night when it is dark out. One of the biggest challenges to wide-scale use of solar power is figuring out how to effectively store energy gathered during the day for use at night, or during bad weather when the solar panels cannot create electricity.

With that in mind, the robot you build in this project will have two different sources of power: solar panels and stored energy in the form of batteries. You will build an electrical circuit—or a loop through which electricity can flow—that lets you toggle between powering the robot from its batteries or its solar panels (the solar panels do not recharge the batteries; you can just pick between the two). The circuit will provide power to two motors that make the robot move. You will investigate how the two different power supplies affect the robot's speed in different weather conditions. As you test your robot and analyze the results, consider some of the challenges that need to be overcome as fossil fuels are replaced with renewable energy.

Terms and Concepts

  • Electricity
  • Battery
  • Energy
  • Fossil fuels
  • Greenhouse gases
  • Climate change
  • Renewable energy
  • Solar panel
  • Bristlebot
  • Circuit
  • Motor
  • Breadboard

Questions

  • Why is renewable energy important?
  • What are some sources of renewable energy?
  • What are some of the limitations of solar power?
  • Do you think your robot will be faster using battery power or solar power?
  • Do you think the weather will have any effects on the robot when it is running on battery power? What about the solar panels?

Bibliography

  • Woodford, C. (2014, May 14). Electricity. Retrieved August 22, 2014, from http://www.explainthatstuff.com/electricity.html
  • Grusin, M. (n.d.). What is a Circuit? SparkFun Electronics. Retrieved July 31, 2014, from https://learn.sparkfun.com/tutorials/what-is-a-circuit
  • Science Buddies Staff. (n.d.). How to Use a Breadboard. Retrieved June 23, 2016, from http://www.sciencebuddies.org/science-fair-projects/breadboard-tutorial
  • U.S. Energy Information Administration. (n.d.). EIA Energy Kids — Solar. Retrieved August 25, 2014, from http://www.eia.gov/kids/energy.cfm?page=solar_home-basics

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Materials and Equipment

  • Advanced Bristlebots Robotics Kit, available from our partner Home Science Tools. You will need the following materials from the kit:
    • Mini breadboard
    • 2xAAA battery holder
    • AAA batteries (2)
    • Mini vibration motors (2)
    • Toggle switch
    • Mini solar cells (2)
    • 1 inch red jumper wire
    • 1 inch black jumper wire
    • Note: This kit also contains materials for the Build a Light-Tracking Bristlebot project, a robot which will automatically drive toward a light source.
  • You will also need the following materials, not included in the kit:
    • Identical toothbrushes (2); be sure the longest bristles on the brush are all slanted in the same direction. See Figure 3 in the Procedure for details.
    • Scissors or wire cutters
    • Double-sided foam tape
    • Optional: Craft materials to decorate your robot (such as googly eyes, colorful pipe cleaners, etc.)
    • Outdoor area with direct sunlight. This project will not work with artificial light.
    • A smooth surface you can take outdoors, or outdoor furniture, on which to test the robot; for example, a smooth piece of wood, plastic, or glass, or a large textbook. The robot will not travel very well on rough surfaces (like sidewalks or dirt) because the toothbrush bristles might get stuck.
    • Objects to create walls to make the robot go straight; for example, two rulers or two textbooks you can place side by side.
    • Stopwatch
    • Lab notebook

 Recommended Project Supplies

Get the right supplies — selected and tested to work with this project.

Get the right supplies — selected and tested to work with this project.
Project kit available at Home Science Tools.

Project Kit: $59.95
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Remember Your Display Board Supplies

Remember Your Display Board Supplies

Experimental Procedure

Assembling Your Robot's Body

Follow the steps in this slideshow to build your robot's body. Make sure you read the captions below each image for important notes about each step.

').appendTo('head');

Assembling Your Robot's Circuit

If you have never used a breadboard before, you should refer to the Science Buddies resource How to Use a Breadboard before you continue. Build the circuit on your robot's breadboard by following along with the slideshow. Make sure you read the captions below each image for important notes about each step.

').appendTo('head');

Comparing Solar and Battery Power

  1. Use household materials to set up a "chute" to force your robot to go straight, like the one shown in Figure 2. Make sure you use a smooth, flat surface (the bristles will get stuck on rough surfaces like carpet).

Figure 2. An example course for the robot to drive on. The lid of the plastic container provides a smooth, flat surface, and the rulers act as walls to help the robot go straight.
  1. In your lab notebook, set up a data table like Table 1. You will use the data table to record how long it takes the robot to go from one end of the course to the other in seconds (sec).
    1. The exact weather conditions you are able to test may depend on the time of year and the climate where you live. However, remember that you need to test the project outside, in natural sunlight. The solar panels will not work under artificial light.
    2. The order in which you do the following steps might also depend on the weather. For example, if you build your robot on a cloudy day, you can do the cloudy day trials first, and then the sunny day trials later.
Power SourceWeather ConditionsTrial 1
(sec)
Trial 2
(sec)
Trial 3
(sec)
Average
(sec)
BatteryFull sunlight    
BatteryCloudy    
BatteryNighttime    
Solar panelsFull sunlight    
Solar panelsCloudy    
Solar panelsNighttime    
Table 1. Example data table to record how fast your robot can drive through the course.
  1. Take the robot and your test course outside on a sunny day.
    1. Get your stopwatch ready.
    2. Slide the power switch "down" (toward row 17 of the breadboard) to set the robot to battery power.
    3. Set the robot down on one end of your course. As soon as you do, start the stopwatch.
    4. Watch your robot as it goes down the course. If it gets stuck against one wall, quickly give it a gentle nudge to knock it loose. If your robot consistently turns sharply to one side and always gets stuck as a result, see the Help section for suggestions.
    5. As soon as the robot reaches the other end of the course, stop the stopwatch.
    6. Record the time in your data table in the row for "battery power" and "full sunlight".
    7. Repeat step 3 two more times and record the data in the appropriate trial columns.
  2. Switch the robot to solar power by sliding the power switch "up" (toward row 1 on the breadboard). Important: Make sure the robot's solar panels are aimed directly at the sun, as shown in Figure 3. This will ensure that they receive the maximum amount of solar power possible. The wires connected to the solar panels are flexible, so you can bend them slightly to aim the panels toward the sun.

Figure 3. Make sure the solar panels are pointed directly toward the sun.
  1. Repeat step 3 with the robot set to solar power instead of battery power.
  2. Wait for a cloudy day, and repeat steps 3–5.
    1. Optional: If you live in an area with a lot of sunlight during certain times of the year, it might not be feasible for you to wait for a cloudy day. Instead, try doing your test very early in the morning or very late in the evening, when the sun is low in the sky and not as strong as it is during the middle of the day. Adjust the labels of your data table if necessary (for example, from "cloudy" to "early morning").
    2. Do your best to aim the solar panels directly at the sun through the clouds. You can guess where the sun is based on the time of day (ask an adult if you need help).
    3. Make sure you record all your results in the appropriate row of your data table.
    4. If the robot does not move at all, write "did not move" in the appropriate cell of the data table.
  3. Take your robot and test course outside at night, and repeat steps 3–5. Remember to record all your results in your data table and write "did not move" if the robot does not move at all.
  4. Analyze your data.
    1. For each row of your data table, calculate an average for the three trials. For example, if the trials were 8 s, 10 s, and 12 s, the average would be (8 + 10 + 12) / 3 = 10 s. Do not include "did not move" data points in an average, since they do not have a numerical value. If the robot did not move for all three trials, also write "did not move" for the average.
    2. Make a graph for the battery-powered data with the weather condition on the x (horizontal) axis and the average time to complete the course on the y (vertical) axis.
    3. Make a second bar graph for the solar-powered data with the weather condition on the x (horizontal) axis and the average time to complete the course on the y (vertical) axis. If the robot did not move for all three trials for a certain data set, write "N/A", which stands for "not applicable," meaning you could not record any times.
    4. Answer the following questions:
      1. Did weather impact the robot's speed using solar power? If so, in which weather condition did the robot move fastest? What about slowest?
      2. Did weather impact the robot's speed using battery power? If so, in which weather condition did the robot move fastest?
      3. What are the advantages and disadvantages of running the robot on solar power compared to with the battery?
    5. Now, it might be tempting to think about which power supply is "better" just based on the results of your experiment, but remember, there are some other factors to consider.
      1. Which power supply is renewable? (Note: You did not use rechargeable batteries in this project, but even if you did, such batteries are not considered renewable because they need electricity from a wall outlet to be charged, and that electricity likely came from a power plant using fossil fuels.)
      2. What challenges would you need to overcome to use different energy sources at night or when it is cloudy? Could you build a robot with rechargeable batteries that can store energy for later use? See the Make It Your Own section for more details.
      3. In this project, you are restricted to using the solar panels and battery pack that comes with the kit, but do you think you could use larger solar panels or battery packs to make the bristlebot run faster? How could this change your results?

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Variations

  • How does the robot's speed change if you change the angle of the solar panels relative to the sun (e.g. to the positions labeled "wrong" in Figure 4)?
  • How does the robot's speed change if you test the solar panels at different times of day, or different times of year? Does this have to do with the sun's position in the sky?
  • Look up the difference between series and parallel circuits. In the circuit for this project, you connected the solar cells in series. What happens if you connect them in parallel? Does the robot's speed change?
  • Can you make a rechargeable solar-powered bristlebot? The goal is to make a circuit with solar panels and rechargeable AAA batteries. In direct sunlight, the solar panels can run the motors and charge the batteries. When sunlight is not available, the robot can run on backup battery power. This eliminates the need to manually select one of the two power supplies with a switch. See this page for a circuit design (requires extra components not included in your Advanced Bristlebots Kit).
  • What happens if you remove the batteries from the robot to make it lighter, and only run it on solar power? Does that make the robot faster?
  • Can you build a larger solar-powered robot? For example, check out the Build a Brushbot activity or the Art Bot: Build a Wobbly Robot Friend that Creates Art project. You will need to purchase bigger solar panels to build a bigger robot.
  • Use a multimeter to measure the open-circuit voltage and short-circuit current of both the AAA battery pack and the solar panels. How do the two power supplies compare in terms of the maximum voltage and current they can provide? How do the supplied voltages and currents change when they are "under load" (driving the motors)? Refer to the Science Buddies reference How to Use a Multimeter if you need help using a multimeter.
  • How long does it take for your batteries to die if you leave the robot on continuously? Do an online search to look up the prices of AAA batteries and tiny solar panels. Use that information to calculate the payback period for the solar panels, or the amount of time it takes you to start saving money if the solar panels are initially more expensive than the batteries.

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Recent Feedback Submissions


Chakal4568 said:
2018-02-11 21:43:32

What was the most important thing you learned?
That tiny solar panels are weak.

What problems did you encounter?
Literally impossible to find toothbrushes with bristles slanted in only one direction.

Can you suggest any improvements or ideas?
No

Overall, how would you rate the quality of this project?
Poor

What is your enthusiasm for science after doing your project?
Very low

Compared to a typical science class, please tell us how much you learned doing this project.
About the same

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Frequently Asked Questions (FAQ)

Q: Can I do this project using artificial light?

A: No. Make sure you use direct, natural sunlight for the solar-powered version of the robot.

Q: Why are my motors not spinning on battery power?

A: If your motors do not spin when you push the power switch "down" to set the circuit to battery power, check the following items. For an overview of some other common mistakes you can make when using a breadboard, see the Common Mistakes section of the breadboard tutorial.
  • Make sure you properly inserted the two AAA batteries into the battery holder, so the "+" symbols on the batteries line up with the "+" symbols inside the battery holder.
  • Make sure the red and black wires from your battery pack are pressed all the way into the correct holes of the breadboard.
  • Make sure the red and blue wires from your motors are pressed all the way into the correct holes of the breadboard.
  • Make sure the spinning weights on the ends of the motors are not getting stuck against the double-sided tape.

Q: Why are my motors not spinning on solar power?

A: If your motors do not spin when you push the power switch "up" to set the circuit to solar power, check the following items. For an overview of some other common mistakes you can make when using a breadboard, see the Common Mistakes section of the breadboard tutorial.
  • Make sure you are outside in direct sunlight, with the solar panels pointed toward the sun.
  • Make sure the orange and black wires from your solar panels, and the red and black jumper wires, are pressed all the way into the correct holes of the breadboard.
  • Make sure the red and blue wires from your motors are pressed all the way into the correct holes of the breadboard.
  • Make sure the spinning weights on the ends of the motors are not getting stuck against the double-sided tape.

Q: Why does my robot always turn to one side?

A: Since the robot does not have a "brain" to help it steer left and right, it may tend to drift off in one direction. This is normal and does not mean there is anything wrong with your robot. It is actually pretty difficult to build a robot that will drive perfectly straight, due to small misalignments when you attach parts like the toothbrush heads and motors. For your experiment, you can use walls to help guide the robot along a straight path.

If your robot turns very sharply to one side, check the following:

  • Make sure the battery holder is centered under the breadboard. If the battery holder is too far off to one side, this could cause the robot to turn excessively.
  • Make sure the two toothbrush heads are mounted straight and parallel to each other. If one or both toothbrush heads are crooked, this can cause the robot to turn to one side.
  • Make sure you are using two identical toothbrushes. If you use two different toothbrush heads, this could cause the robot to always turn to one side.
  • Make sure both motors are spinning. If only one motor is spinning, this can cause the robot to drive in very tight circles.

Q: Why does my robot not go forward at all?

A: If your robot does not move forward at all, meaning it just goes sideways or even backwards, this is likely caused by the type of toothbrush head you used. It is very important to use a toothbrush where the longest bristles are all slanted in one direction. If you used toothbrushes with straight bristles, or toothbrushes with bristles slanted in both directions, the robot will not be able to drive straight.

Q: What is the circuit diagram for this robot?

A: Note: This question is intended for advanced users who are already familiar with circuit diagrams.

The circuit for this robot is relatively simple. The circuit diagram is shown in Figure 4. The two motors are connected in parallel. A single-pole double-throw (SPDT) switch lets you toggle between solar power or battery power. The two power supplies are never connected at the same time, and the solar panels do not charge the batteries (for ideas on making a rechargeable solar circuit, see the Make It Your Own tab).


Figure 4. Circuit diagram for the solar-powered bristlebot.

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By Amy Cowen on August 30, 2013 11:30 AM

As this mom discovered, with a bag of toothbrushes and some basic electronics supplies, you can give a group of kids a fun introductory robotics experience—no prior robotics expertise necessary!

Since the BristleBots robotics project first appeared at Science Buddies, I have wanted to try these little toothbrush-head bots with my kids. The light-tracking robot project appeared shortly after the more ubiquitous brush bot. The light-tracking bot is more complicated, but I marked it, pinned it, and put it on my to-do list of hands-on science projects for my kids.

The regular BristleBots were first up.


Hacking for Parts

Initially, I thought I might be able to scrounge up motors from old phones for the BristleBots, giving our robotics exploration a healthy dose of recycling, upcycling, and reuse mentality. I was especially keen to do that when I realized the required motor wasn't readily available. (Note: Science Buddies is working to put in place a reliable source for these motors to make acquiring the parts easier.)

With the best of green intentions, I fished an old phone from the kitchen junk drawer to see if I could salvage a motor. Getting my old clamshell apart was far more complicated than I expected. As I started dismantling, I quickly realized I don't have the all-important Torx (star) tool! Given that, my methods were substantially more crude, but layer by layer, I got the phone apart. I finally unearthed the vibrating motor only to discover it had no wires. I needed wires, and I don't have a soldering iron (and wasn't planning to use one for the project with the kids).

After a surprising amount of brute force to break my old phone, I was back to square one with the motors and glad I had tackled the phone well in advance as I sorted out what I needed to order for our summer science.

I compiled a list of parts needed for the two robotics projects, ordered what I could, and stopped in at a local Radio Shack to pick up one final electronics piece (x3).


Shopping for Tootbrushes

Finding the toothbrushes ended up being almost as complicated as gathering the electronics supplies. I spent a lot of time scouring online sites and comments on blog posts to try and figure out what kind of angled brush heads were commonly used. For a full independent student science project, a student might explore the effectiveness of different types of heads and bristles. But as a parent coordinating two separate toothbrush-dependent, hands-on robotics activities for three kids, I needed nine toothbrushes. I was on a budget, and I wanted to try and get toothbrushes that would "work" so that the focus of our activity was on the electronics and basic wiring rather than on evaluating brush heads. I didn't want the type of brush to be an experimental variable. I went with slanted bristles.

If you plan to make toothbrush bots with a bunch of kids, make sure you note ahead of time that angled brush heads are not the cheap ones! Angled brushes may run, on average, several dollars a piece, so while BristleBots can be fun for a sleepover or a birthday party, you may need to buy in bulk, or else experiment with other brush heads before you buy for a crowd. Will a straight head work well or well enough for your purpose? (If you look carefully at the photos above, you will see the slanted bristles and the row of rubber tips on the outer edge of our bots—pretty common BristleBot fare!)


Home Robotics 101

Parts in hand, we settled in to make BristleBots. Having read the Project Idea several times, written about it several times, and watched the Evil Mad Scientist Laboratories video, I fully expected this to be a project the kids would whiz through in about five minutes. Part of me was worried that it might be anticlimactic precisely because of the low-level of difficulty, but I wanted to do these BristleBot explorations back to back, the easiest one as a stepping stone into the more sophisticated light-tracking one.

I am not sure now what happened when I was ordering... but as we sat down to make the BristleBots, and I sorted out the supplies, I realized we had a pack of pancake motors but none of the oblong ones that the procedure specifies. This was definitely a parental "oops" moment on the supplies front, but working on a project like this with kids requires flexibility.

We plowed ahead.

Less than an hour later, we had three BristleBots that worked, on and off. We had to continually fidget with them to get them to stay on or come on. I was doing more of the tweaking than they were, but it gave us a chance to talk about what the problem was (not enough constant pressure on the battery with the wire on each side) and brainstorm ways to address it. We tried tape. We tried more tape. We tried pressing harder. We found that sometimes very light pressure worked best. These bots were a bit finicky. There was a lot of trial an error. We would get one working, let it loose on the table, and the next one would stop!

We finally tried something that worked wonders—a twist tie from a plastic bag. This helped us maintain consistent pressure on the contacts. Other solutions could also work, and finding your own is part of the challenge and the fun of a robotics or engineering project!

About the time we got our twisty ties solution in place, the first battery died. And then the second. Two brand new batteries died in under a half hour. Chalk that up as one less than happy parent with a bulk battery purchase!

But, the bots worked. The kids had fun. And, in the end, I was far more appreciative of the off-the-shelf bugs these bots simulate. I always thought they were overpriced, but there is a reality to the fact that when flipped on, they run!

Even so, making our own BristleBots was an awesome first-time, non-kit robotics experience with kids of differing ages and with varying levels of hands-on tinkering and electronics experience.


Tips for Your Own Robotics Activity

Here are a few pointers gleaned from our BristleBot building:

  • Big scissors. Snipping off toothbrush heads isn't easy! We ended up using some rather giant hedge shears. Plan ahead. Be fearless.
  • Trim with care. Be careful trimming your bristles. (Say this over and over to your young engineers, especially eager ones.) While some trimming can change the way your bot moves, you can trim too much and cause your bot to not be able to stand up.
  • Get hands on. Experiment before taping anything in place to see how the vibrating motor works. This is the basic electronics lesson of your activity! Put one wire on each side and press. It should vibrate. Don't worry, it won't hurt or shock you! Feeling how the wires get pressed to the battery to make the motor work will help your students better understand what to tinker with to make the right "contact" when the battery is on the bot.
  • Tinker. Test. Tinker again. If you are having trouble getting the motor to work on the bot, experiment with the placement of the wires on each side of the battery. You can tape and re-tape them as many times as you need to. You might also try securing them differently or more tightly. Just remember, to turn the bot "off," you will need to be able to "undo" the connection easily.
  • Keep the conversation going. Talk about what the bot does as it moves around and why. This is a pretty low-key and not overly-smart bot. But when it runs into something, it does gradually adjust and work its way to a clear path. Talking about what you observe helps your students practice articulating what they see and encourages them to think about and apply what they know.
  • Create a race path. How smart and how fast are your toothbrush-head bots? After the building is over, have the kids build a maze or race course to test and race the bots. Cardboard, recycled tubes taped together, wooden sticks, straws, even LEGO® can all be used to develop a cool pathway for the bots to navigate. As you and your students watch the bots move, you will find you have new things to talk about!
  • Personalize and customize! Once your bot works, it is easy to personalize it and make it your own. Add eyes! Add antennae! Add this or that to give your BristleBot your own style.

Have fun!


Share Your Family Science or School Science Project

What did your recent science project or family science activity look like? If you would like to share photos taking during your project (photos like the ones above or photos you may have put on your Project Display Board), we would love to see! Send it in, and we might showcase your science or engineering investigation here on the Science Buddies blog, in the newsletter, or at Facebook and Google+! Email us at blog@sciencebuddies.org.



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