For my intensive project at BlueStamp, I decided to make the Tabletop Wanderer Robot based on this Instructable. In the process of making this project, I learned a lot about different hardware and software aspects of robotics. I used to think that building a robot was very difficult and required some genius sorcery. However, by challenging myself to build one of my own, I’ve seen that it is possible to break up the building process into parts and create a great final product.

I’ve also narrowed down the different engineering fields I’m interested in. I’ve enjoyed the mechanical and software aspects of my project, but the electrical part proved to be extremely fickle to troubleshoot, as we couldn’t always be sure if my infrared (IR) issues arose from bad hardware, problems with my circuitry, or something else. As of right now, if I can find a form of engineering that combines math and physics with software, I would be very interested in it.

BOM (Bill of Materials): this is the list of all the materials I used to create my final product

Build Plan: this is my initial plan for building this robot. I switched the order of the first and second milestones, programming my Arduino with the infrared sensors first, and then building my chassis.

Code: a repository of the final code for my robot can be found here.

Schematic: the final schematic of my robot is here.

A presentation and demo of my robot can be seen below.

For this milestone, I finished my Tabletop Wanderer Robot. I assembled my chassis, mounted my infrared (IR) sensors onto the robot, and got my robot to the sensors.

As in milestone 2, I had huge issues with IR in this milestone, and spent another week troubleshooting. I initially put my IR sensors in a breadboard, a small board that can be used to prototype components and circuits. When I tested these IR sensors after milestone 2, they didn’t work. I tried many combinations, checked my wiring, and nothing seemed to work. I then did some research and found out that the IR detectors could require a low-pass filter (a combination of capacitors and resistors that can filter out IR waves from the environment) in order for there to be a solid detection. I used some 22 uF capacitors in parallel with the detector and the resistor I had in previously in order to create the filter, and the sensors started working. However, I had even more issues with IR.

My next challenge was moving the IR sensors from the breadboards to PCBs (Printed Circuit Boards that allow one to create an actual circuit) and soldering the sensors in. This proved to be very difficult for several reasons.

The first issue was creating common ground between the emitter and detector. I realized that the ground levels between the two components could be different (i.e. one at 1 V and the other at 2 V). The instructors told me this would cause issues when I ran power through the circuit. To solve this issue, I initially created solder bridges between the negative terminals of each component. The solder bridges consisted of melted wire that connected one component the other. This method didn’t work, as the solder didn’t conduct the electricity well enough for the common ground to work. Eventually, I started using jumper wires to connect the negative terminals, and connecting these wires to the ground provided by the Arduino. This solution worked, so I kept it in my PCB.

I also had huge issues when soldering in the actual emitters and detectors into the boards. I found that the emitters/detectors worked in the breadboards, but when I moved them to the circuit board, they stopped working. The detectors would consistently read in only 0s (surface detected), or only 1s (surface not detected). I tested many circuits with multimeters and other devices, but I couldn’t find anything wrong.

After several troubleshooting attempts, I finally cut the legs of the emitters/detectors I had soldered in the PCB board and putting these components back in the breadboards to test them. I tried several combinations, testing emitters from the breadboard with the detector from the PCB board, and the detector from the breadboard with the emitter from the PCB board. Through these trials, I realized that the detectors of the PCB boards didn’t work after I soldered them in. I was told that this was likely because I was soldering the detectors at higher temperatures than what they could handle, burning the circuitry in them.

To fix the high temperature issue, I tried heat-sinking the emitters and detectors by using alligator clips to absorb the heat from the iron while soldering the components in. I tested the circuit board, and it still didn’t work.

Finally, I tried soldering in pin connector headers into the circuit. These allowed me to allocate a space for the sensors without having to expose them to the heat of the soldering iron. I could put the emitter/detector in the headers once the PCB board had cooled down after soldering. This method proved to be effective, and I finally got a sensor module that worked.

However, I still had to recreate this module three more times. I had issues with the “copies” of the modules, as even though the emitters/detectors worked, sometimes my solder bridges wouldn’t conduct electricity well enough for current to reach the component. Other times, even the instructors couldn’t identify the problem with the circuit, at which point I had to dump the board and try again.

Overall, I went through over 10 attempted circuits, of which I got 5 to work (I created an extra module just in case one the four modules I was using for my robot malfunctioned). I was able to connect these to a common breadboard with my servos and control them well with my Arduino.

Getting the chassis was a problem in and of itself. UPS and the U.S. Postal Office consistently lost my package, or stated that it hadn’t been delivered. They once delivered the package, but took it back because they weren’t able to obtain a signature. This resulted in a delay of about 5 days in getting the chassis.

Once I got the chassis, I found that the screws and other hardware we had at the classroom weren’t the right size/model as the ones needed to put the chassis together. I decided to just use superglue to enhance the friction-fit that the laser cut parts had come with. In this part of the milestone, I also learned how to use a Dremel (a power tool that can cut, drill, and perform other functions on surfaces) to enlarge some of the holes for my servos because they wouldn’t fit in the holes in the laser-cut parts.

Once the chassis was assembled, I was able to mount the circuits onto the arms of the chassis, and connect them to the servos and Arduino. I had to adjust the angle of the IR emitters/detectors so they were perfectly aligned to detect IR. I found that if I cut the heat shrink wrap on the IR emitter down, the span of the IR emitted increased, so the detector could detect IR from farther away, and the angles of the sensors didn’t have to be as precise.

Now that this milestone has been completed, I’d like to get my IR to be more precise so the robot consistently doesn’t fall off the table (right now, the IR is still shaky, and the instructors say that it’s probably just the hardware). I’d like to modify the robot so it has a sensor to detect objects in front of/behind the robot. If there’s enough time, I’d like to try making remote control capabilities for the robot, so you can dictate where it goes.
A Github repository of my code for this milestone can be found here.

A schematic of my circuits can be found here.

For this milestone, I made a cardboard prototype of my robot that responded to the surfaces detected by the 4 infrared (IR) sensors I put in breadboards.

I decided to design and make the cardboard chassis because the Instructables website I was using for guidance didn’t have dimensions for the laser cutter files it provided for the chassis. I measured and cut out the cardboard pieces of the chassis using an X-acto knife. Cutting with the knife was slightly difficult, and I had some issues getting my measurements right. In the end, I designed the base and walls of the chassis, and added four arms to hold my IR sensors. I also designed wheels to attach to my servos (motors that can turn continuously and can be used to make a wheel).

I cut out places for my servos to fit through the walls of the chassis, and fastened the servos in with paper fasteners. I did the same thing with my Arduino, placing it at the center of the base of my chassis. Then I started my breadboard circuits with my IR emitter-detector pairs.

I had IR issues in this milestone, as well. Each emitter-detector pair worked fine on its own, but when I tried to use two at once, one wouldn’t work. I replaced the emitters with regular LEDs, and found out that one would blink at a rate of 38 kHz, but the other emitted a steady light. It took some troubleshooting, but I figured out that this was because I was trying to call the tone() method of Arduino, the function I was using to create a 38 kHz tone, on two different pins, when in reality you can only call it on one pin (unless you use the noTone() method).

To fix this issue, I decided to use a “main” breadboard that would connect to all of my components (all the sensors and the servos), and provide them direct power from the Arduino. I put two emitter-detector pairs on two different breadboards (for a total of four pairs), and connected one pin from the Arduino to the main breadboard. I then connected each emitter from the two side breadboards to the main breadboard, essentially connecting them to one pin. I also connected my servos to the main breadboard, and provided power for each of these components.

Finally, when I tested the robot, it worked, and I was able to see my wheels rotate and move my chassis whenever a surface was detected by all four sensors.

Code for this milestone can be found here. A schematic of my breadboards can be found here.

For my next milestone, I want to assemble my acrylic plastic chassis and solder in all my components in actual circuit boards. I will then mount this circuit on the chassis, and complete my robot.