I live in Boston and my family lives in Utah. I have been looking for a fun project to do, and so I thought it would be a good exercise to try to create a little robot that can drive around remote controlled through skype holding someone's cellphone in a selfie stick. This way, I could call my family and control while I move inside the house virtually. The car will be drived with servo motors and battery powered (this is an area for improvement) and will be controlled through skype through interfacing on Arduino. There will be a sensor for the car to know when there is a cliff/step and it will be coded to stop to protect itself if it sees the jump.
Tools: Arduino, drill, solder
First things first, I went and made myself a schedule of when I will make my robot, and made an excel sheet of all of the costs of the robot to make sure I could afford it. I wrote down the risks, objectives, and functions and then I decided I had enough to go off of and I ordered my parts.
The first step in making my robot was to get the wheels together. First, I drilled two 1/8'' holes in each of the servo motor's turbines so that I could fit a zip tie through them.
Once I had the holes, I then drilled through the wheels and then connected the turbine to the wheels
I then connected both of the bodies of the servo motors with zipties, and then screwed on the turbine of the servo motors connected to the wheels to the body.
The plan was originally to place the wheels in the middle of the box, but I decided that I wanted to make the robot more stable, so I had put in a wheel that I got from an old office chair at the head of the box. I attached the wheel by making a hole in a block of wood that is slightly smaller than the wheel top, and then forced it in.
Then, there was the trick of cutting the holes in the plastic container. My access to tools was limited, and scissors, pliers, tree cutters, box cutters, knives all didn't work. So, I took apart a coping saw and threaded it through a drilled hole to cut the square holes for the wheels to go through.
Once I had the square holes cut, I attached the servo motors to the box using zip ties and made a hole for both of the wire leads to come out of
And that was it for the wheels! I could then hook this up to an Arduino and the wheels would spin!
Selfie Stick Contraption
I bought a selfie stick and immediately realized it wasn't going to work how it was. I needed the phone to be able rotate up and down, while also having a stable base. The selfie stick I bought didn't rotate at all.
So, I cut off the part sticking off of the phone holder and one of the sides of the stick. I went to Home Depot and scoured around until I found these two plates used for plumbing. I connected a plate to the side of the selfie stick, and then put two bolts in the bridge to make it so that the other side of the plate had enough room to rotate freely while the other side was locked in place.
I forgot to take pictures of all of the next steps I did, so here is a summary below
I connected the phone holder to the rotating metal plate using zip ties
I got an old hanger from my closet to use as pullies I could put in the continuous rotation motor.
I cut off two of the turbines of the servo motor so they wouldn't get in the way
I measured the length needed to connect the selfie stick head and the servo and then bent the hanger to keep it in place
Then I also attached the servo to the selfie stick. This was harder than I thought it would be. The selfie stick was round and made out of metal so it was difficult for my drill to go through it. I made two holes, but I accidentally made them in line with the servo, so I ended up making a complicated zip tie pattern to attach to motor.
Then I connected the selfie stick to the base using zip ties and that was the end of this step
Fixing Problems
I realized I didn't consider how some actions would affect the robot. Two problems presented themselves:
When I made a hole from the wheel holes to the center of the box so that I could get out the servo motor wires, the stiffness of the box was compromised. One side of the box was drooping down on the ground because of this cut.
The zip ties holding the selfie stick up were not enough. There was nothing stopping the stick from rotating, and the box wasn't perfectly rectangular so that made the selfie stick rest on the box at an angle, so the view from the phone would always be tilted downward. Also, the weight of the stick made problem 1) much worse as well.
So! Opportunities for advancing my robot.
I went to Home Depot and found some inspiration
For problem 1 I got a metal plate used for door hinges and just completely covered the cut. Then I drilled a small hole for the wire to go through, and this simple mechanism fixed this problem!
For the selfie stick, I did a few things to ensure it would be straight, stable, and supported. I got two U shaped parts to put one at the bottom and one at the top. I connected the Us to the box with two large washers and a washer that fit the screw stacked on top of each other to try to even out the stress on the box. Then I layered a lot of duct tape on one side of the stick to account for the angle of the box.
Circuitry and Sensors
Next, it was time to create the circuitry. To control the sensor, I made a circuit of a photosensor and some LEDS and resistors that also attached to a switch to turn on and off the sensors/motor. The switch was essential for prototyping the spinning of the wheels and that the sensor worked correctly
I then mounted this onto a CD (if it works it works) with the sensors attached. The sensors are in the front of the car so that if it hits anything it will stop instead of ramming straight into a wall. I had to make the PCB higher off the CD to protect the wiring I did underneath the circuitry. Stacking bolts works, but I'm sure there is a cleaner solution with access to more materials.
This was then attached to the frame of the car by being wedged between the connection of the front wheel and wooden block. The tension of the screw of the wheel going into the block was enough to keep the CD steady and the touching surface area of the block-container-CD distributed the load of the circuit and touch sensors enough that the CD didn't snap form the front heavy load, and I added extra two screws on the side as well to ensure that this load was distributed.
I realized that the placement of the Arduino would be better at the top of the box in the center because the weight on one side of the box it a bit lopsided, so I then attached to the ceiling of the box with zip ties, and the code was uploaded!
What I'd do Differently
Get a different container for the components. The plastic casing was too big, too hard to drill through, and too wide which created problems for the wheels
More planning, I'd do one part and get it really perfect and be satisfied with it, then I'd bring it back to the base and have no idea how it's going to fit or be constrained. The hardest part was attaching the components. Zip ties work, but with planning I could take advantage of all the piece's locations and make them fit together
Some problems were due to lack of access to a mill and limited materials. I'd make more of the components workable and safe.
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