You'll build the slider crank assembly from three craft sticks. The mechanism consists of these key parts:
- Crank shaft
- Connecting rod
- Slider (also known as a piston in some mechanisms)
We'll drive the crank shaft with the servo motor, and the slider will translate back and forth along a guide block made of cardboard.
Prep the Linkages
Here, they've been marked 'CS' for crank shaft, 'CR' for connecting rod, and 'P' for piston (this is the same piece as the slider).
Next, we'll join the linkages using the brass paper fasteners.
Fasten the Pivots
Use hot melt glue to adhere the A pivot end of the crank shaft to the large, round servo horn. Once it cools, press it onto the servo's splined shaft.
Use the horn to rotate the servo shaft to the far left and then remove, rotate, and reattach the horn to the shaft so the linkages are in a straight line to the left as shown.
You can secure the servo horn to the servo shaft with the small screw and a screwdriver.
You'll power and control the servo with the Circuit Playground Express. Plug the three alligator clip jumper wires into the servo cable housing:
- Black to Brown
- Red to Orange
- Yellow to Yellow
Connect the alligator clips to the Circuit Playground Express pads:
- Red to 3.3V (or, you can connect to VOUT for more power!)
- Black to GND
- Yellow to A1
Next, we'll program the Circuit Playground Express using MakeCode.