Dollar Store Robotics (Building Robots Cheaply)

I am a middle school science teacher who also organizes our Robotics club. Our robotics club got started about 10 years ago with the help of a very generous parent who donated 10 Lego Mindstorm kits and 3 laptop computers. It was because of this donation, our robotics club was able to learn about the field of robotics.

While the Lego Mindstorm robot kits are great for learning and building robots, they are very pricey. They are also very limiting in what you can build. So I started to include other materials such as dollar store foam board to help build the chassis. The combination of this simple addition with lego pieces made fabricating robots much quicker as the foam board was easy to work with and to attach lego pieces to.

However, the weak link became the Lego Mindstorm software and maintaining these three laptops. About 7 years ago, our school went digital with a BYOD chromebook policy. Since I am not aware of any solution to program these mindstorm robots the student chromebooks, I began looking for alternatives. I came across CodeBender and that fit the bill. However, Codebender soon closed down and reopened as a subscription based service that defeated my purpose in saving money. Then came Arduino Create.. while fairly inexpensive, it too was a deal breaker as I had virtually no budget.

Then I found a free resource called Chromeduino that fit the bill. I also learned about micropython and esp8266 basic that did not require compiler software to implement code. These solutions used much less expensive microcontrollers that had wifi built in -- this meant that students had an easy way to program their robots with the chromebooks that they had.

With this expense out of the way, I was then able to source components from Alibaba to further minimize the cost. Currently, I am able to create a fully functional robot for $10-$15, depending on components used.

In order to do this I had to figure out what the bare minimum was needed to create a robot. I came up with these 5 items:

Power Supply
Microcontroller
Motors (and motor controller) or servos to move the robot
Sensors (could be as simple as a couple of wires that complete a circuit when bumped)
Chassis

1) For the power supply, I stuck with AA 6-battery packs. This provides 9 volts.. plenty for motors and microcontroller... I found that using 4 AA batteries... sometimes did not provide enough power to the microcontroller when motors were running at full speed.. this caused erratic behavior.

$4 each at amazon but could be much cheaper if sourced from Alibaba and you have time to wait: https://www.amazon.com/Hilitchi-Thicken-Battery-St...

https://www.aliexpress.com/item/1005001407018430.h...

2) You have several choices for the microcontroller -- some are very pricey while others can be had for a couple of dollars. My current favorite is the esp8266 development board which can be purchased on Amazon for about $4 each and for much less at Aliexpress:

https://www.amazon.com/KeeYees-Internet-Developmen...

https://www.aliexpress.com/item/32817060169.html?s...

However almost any microcontroller works well, such as the microbit but at $20 each, this breaks my meager budget.

3) For movement you have two options: DC motors or Servos... if you use DC motors, then you need a motor driver. If you decide on servos, you can control them with your microcontroller. Servos are more expensive than DC Motor/Motor Driver combinations but are easier to implement with code.

DC Motors with wheels are about $3.50 each at amazon.

https://www.amazon.com/Electric-Magnetic-Gearbox-P...

and are as low as $0.80 each at Aliexpress

https://www.aliexpress.com/item/4000206577910.html...

You will also need an l298n motor driver which might cost a few dollars at amazon or 1/2 that at Aliexpress.

https://www.amazon.com/Controller-Module-Bridge-St...

https://www.aliexpress.com/item/4001228175086.html...

If you decide on servos, make sure you get continuous rotation servos and you can forgo the motor drivers.

This is where the price difference comes in (these can run $5 each and maybe $4 each at Aliexpress):

https://www.amazon.com/Geekstory-Feetech-Degree-Co...

https://www.aliexpress.com/wholesale?catId=0&initi...

4) For sensors you can get by with paper clips or stiff wires as touch sensors or get fancy with ultrasonic and light sensors... both can be purchased relatively cheaply (about $0.25-$2 each)

https://www.amazon.com/Smraza-Ultrasonic-Distance-...

https://www.aliexpress.com/wholesale?catId=0&initi...

https://www.aliexpress.com/item/4000423007932.html...

5) For the chassis this is where you can save the most.. you can spend a few dollars to buy a premade chassis

A simple chassis with motors and battery holders can be bought for about $10

https://www.amazon.com/SenMod-Robot-Chassis-Arduin...

You can buy a full kit for about $25 at amazon or much less at Aliexpress which has all of these components or build you own for about 1/2 that.

https://www.amazon.com/VKmaker-Avoidance-tracking-...

https://www.aliexpress.com/wholesale?catId=0&initi...

This is where the Dollar Store comes in... more details in following steps.

So I have come up with these budget friendly options (using AliExpress Prices - you do have to be patient though... and order in quantity, but for about $100 I was able to purchase enough supplies for 10 robots):

$1.50 Power Supply

$1.60 Microcontroller

$5.00 Motors (and motor controller) or servos to move the robot

$2.00 Sensors (could be as simple as a couple of wires that complete a circuit when bumped)

$0.10 Chassis (Foam board - can be used to make 10+ robots

$10.70 - Total cost per robot

Step 1: Dollar Store Supplies

While visiting my local Dollar Tree... I found a few items that I thought I could use to build a robot with. These include: (not all were used in this particular instructable)

Chassis:

Foam board for the chassis

Magnets on metal disk (Disk could be used for chassis or attaching components.)

Poster Board

Styrofoam circle for a base... chassis

Wooden Planks

Mobility:

a kit to build a toy car for mobility

a battery operated fan (posibile use for mobility or repurpose motor for other action)

Mounting Hardware:

Double Sided foam tape

Wooden cubes

Zip Ties

Tools and other hardware:

Box Cutter

Wire

Step 2: Using Foam Board for Chassis

As stated in the introduction I have used foam boards for robots for many years now. They work well with legos as you can use a pencil to "drill" a hole so that you can connect beams above and below the foam board which happens to be about the same thickness as a beam. However, with zip ties, legos aren't necessary. You can connect many items to foam boards with simple tools that most students have access to.

Step 3: Using Wooden Plank for Chassis

To use the wooden plank, you will need to drill holes.. however, these will be more durable than the styrofoam or foam boards.

Once holes are drilled, then it is simply a matter of attaching components with zip ties.

Step 4: Using Styrofoam Circle As Chassis

Using styrofoam as a chassis enables students to quickly prototype as it is easy to make holes for attaching components, however is more easily damaged than foam boards and wooden planks. However they seem to be much lighter than other solutions.

Another bonus is the ability to carve out niches so that components fit snugly. Combining these circles with foam boards help improve durability.

This robot was built in about 10 minutes from start to finish. I used an ESP8266 board with a NodeMCU motor controller. Since I was using servos, I did not need really need this, but it does take in 6-12 volts and supplies the microcontroller with 3.3 volts that it needs.

I used ESP8266 Basic to program it.

Step 5: Other Alternatives --- BoxBots-- With Cereal Boxes, Etc

If you have access to cardboard boxes, then you might be able to skip the dollar store assuming you already have zip ties and/or hot glue guns to attach parts. You can also poke holes through the box and use mounting screws to secure pieces.

In this case, I was able to use the toy car from dollar store as a front wheel for the cardboard robot.

I've even used cereal boxes as seen in this instructable: https://www.instructables.com/id/Cereal-Box-Robot-...