Spring 2017 Prosthetic Arm: Buck Converter LTSpice Simulation

The Robot Company | CEO Dr. Gary Hill

Blog Post Created by Project Manager | Bianca Esquivel

Project Simulation Executed by Mission, Systems, and Test Engineer | Phuong Tran and Electronics and Control Engineer | Mikael Movsisyan

Preliminary Information

Test Objective

This experiment was performed in response to requirement

L2.2.1 Wrist Rotation: The prosthetic hand shall provide 90 degree rotation at the wrist. (clockwise/counterclockwise)

Problem: Determine if the buck converter can step down the input voltage of 11.1V (from the Li-Po battery) to 5V, the necessary voltage required to drive the servos.

Materials

Software:

LTSpice

Test Set Up

Procedure:

Step 1: Obtain schematic of the LT3971-5 from the datasheet [Fig. 1]

Step 2: Construct circuit with appropriate electronic component values on LTSpice

Step 3: Run simulation until system response reaches steady state conditions

Step 4: Place a voltage and a current probe at the output Vout

Results

Conclusion

The result of the LTSpice simulation satisfies the supply voltage for the servo. The 11.1V input voltage is stepped down to 5V. The current output reaches up to 1.2A at steady-state and is more than enough to power the servo at the wrist (+ hand servo). Hence, this buck converter can be used in our design for the PCB.