Intro: Black Knight Robot
Good news everyone!
Today we're going to learn how to build a black knight robot, using the Hummingbird Duo Robotics Kit, and various cardboard and paper materials. When completed, you will have a Black Knight Robot that reacts to motion! Check out the picture and video above to see the finished product!
Step 1: Supplies!
For this project, you will need (shown top-down, left-to-right in images):
assorted sizes of cardboard boxes, and/or poster board (or card-stock)
1 Hummingbird Duo board (with power and usb cables)
3 distance sensors
2 tri-color leds
2 vibration motors (optional)
hot glue gun, electrical tape, and/or duct tape
Step 2: Design!
To start, you should make some idea sketches of what you want your robot to look like. By doing this first, you can plan the rough size of boxes you may need, or how you will cut and fold the poster board. You should determine basic proportions of the robot and what you want each movement to look like. I will show my sketches, and explain my thought process, but feel free to alter my design, and get creative!
During this stage, you should also experiment with the hummingbird duo and all parts. To learn how connecting parts to the board works, go to this page: http://www.hummingbirdkit.com/learning/tutorials/connecting-electronics. Spend some time working with the sensors, servos, and leds, so you know how they all work! Servos can only move 180 degrees, so be sure you account for this in your design. It can be helpful to work with these things before building your robot, so that you can plan accordingly.
Step 3: Build!
Now that you've planned everything out on paper, it's time to start building! There are many possible ways to build this, but I used a long, skinny box for the body, and rolled up poster board for the arm segments. Each arm pivots at the body, and at the elbow.
Unscrew the white part of the servo that moves and remove it, so that you can glue it to the inside of the arms. Each arm will have one of these on the inside, so that they move securely with the servos. You will have to cut holes for the parts that connect back to the servo. Also, you will have to cut slits in the arms, above where the screws go for the servos. This way you can fit a screwdriver in to tighten the servos down.
Both servos on the right arm should pivot up and down (with both parts of the arm vertical). The top servo on the left arm should move left to right with the arm vertical, and the bottom server should move left to right with this part horizontal.
You can see some pictures above of my building process. Take inspiration from these, but don't be afraid to try something else!
Step 4: Program!
Now, it's finally time to bring your robot to life (some what)! Using if / else statements, you should tell the robot to do a movement when a sensor is triggered. As you saw in the video of my finished robot, I choose to use a sword slash and shield movement. You can see a picture of my code above, but as with anything else, I'm sure there's many ways to approach programing this robot. I used snap, but you can also use a variety of other programming languages.
A few problems to watch out for:
Don't forget to set initial values for all servos and leds! Your robot needs a starting point!
Place all code in a "forever" loop, otherwise your robot will never finish a movement.
If you decide to use 2 sensors for the sword movement (as I did), you will need to place the if / else statement for one sensor, inside the else statement for the other sensor. Otherwise they will contradict each other.
Step 5: Possible Problems...
Be sure to check your servos, before you glue / tape them on. The last thing you want is for your robot's arm to be on backwards, then you have to re-glue the servo!
Your sword may bend, depending on how you build it (poster board is not the most stable). I fixed this by adding a long metal piece inside the sword (I used a skewer type object, not a pointed one though!).
It seems the max weight of servos is somewhere around 1 other servo and the materials I used for the right arm and sword. Initially, I was going to have a motor in the sword, so that it's position could be adjusted. However, with the motor the arm could not rotate the full 180 degrees. So, be careful of the weight of your materials!
Consider the placement of your shield, only after hot glueing mine to the arm, did I realize the arm should be in the center of the shield. Placing the arm at the bottom of the shield creates instability. However, it would have been difficult to move my shield down, due to the placement of my sensors.
Don't be afraid to start over, or change your design after a bad start! The pictures above show my first attempt, before having a better idea of what the robot should look like.
This robot will also most likely be very front-heavy, so you may have to add a counter-weight or support to the back of it.