top of page
Design
This is the very first block diagram. This model still used a solenoid, and required a power control module to limit the power that would be sent by the supply. In the newer model, this solenoid would be replaced with a servo so that the control of the movement was done by the Metro Mini. Additionally I found that solenoids could not do fine tune movement. The rest of the diagram still remains accurate to the final product.
This is the initial schematic of the controller board and all of its connections. In total there are 10 components with 17 connections to the controller board. This schematic was used to design both the final PCB and guide design on the final housing for the project.
This is the final circuit schematic that was used to design the PCB and control the direct connections between each component. This was generated inside of Eagle CAD.
This is the final PCB design before it was sent off for production. Obviously it was very small, so a housing would be required to hold this board within it. Additionally a few mistakes were noticed after the construction was finished. The only major one was that the OLED had crisscrossed both the VCC and GND, along with the SCL and SDA. This was fairly easy to fix by just flipping the wires connecting the board to the component.
Production
This is the face plate of the final housing. There are three notable features. Firstly the keypad, which controls the pressure that the servos will exert along with gathering user input. Next the OLED display, which shows the user prompt along with the actual pressure that the force sensistive resistors are experiencing. Finally, the button at the top left controls the reset for the control board. To restart the circuit and the code simply press the button.
This is the internals of the final housing. There are three entry points of note. On the bottom is the power input, and received any 5mm input jack, however received 5V. On the left is the micro USB input for programming the control board. The third and final is the 10 pin out connector for the servos and force sensitive resistors on the claw itself. Toward the bottom the keypad back and OLED back can also be seen, wired using colored cables to reduce confusion.
​
This is the final product, with both the claw, housing, and battery pack in frame.
Testing
Pictured above is the final force sensitive resistor readout. As you can see it modulates between 200mV and 500mV, decreasing its voltage as the pressure on the resistor increases.
Pictured Below is the PWM signal that the servo is receiving at 0 degrees (left) and 90 degrees (right). As the angle is increased the duration of the duty cycle is increased to control the servo with a high degree of accuracy
Programming
The code pictured below was designed solely by myself, the only elements that are not my own creation is the libraries that the components use.
bottom of page