Week 09: Output Devices

Assignment

• Measure the power consumption of an output device.
• Document your work on the group work page and reflect on your individual page what you learned.

Measuring Power Consumption of Servo Motors

Servo motors are electromechanical devices that can rotate to a specific position within a range, typically used for precise control in applications like robotics, RC toys, and automated systems. In this assignment, we aim to measure and compare the power consumption of two different servo motors: the DF9GMS 360 Degree Micro Servo and the MG996R Hi-Torque Servo.

Equipments, Setup, and Workflow

To accomplish this task, we will use a USB Digital Tester Meter capable of measuring voltage, current, or power draw of a device. Additionally, for controlling the servo, we will utilize a Servo Driver and Tester, a device that allows us to manually control and test the operation of a servo motor.

Equipments

• USB-powered Digital Tester Meter
• Servo Driver & Tester
• DF9GMS 360 Degree Micro Servo
• MG996R Hi-Torque Servo
• Jumper cables

Setup and Workflow

This is how we’re going to physically setup the components:

USB Digital Tester Meter <–> Servo Driver <–> Servo

We’re going to do the measurement methodically, connecting one component at a time.

1. Connect the digital tester meter to power source (USB port)
2. Connect the USB digital tester meter to the servo driver
3. Read the power (W) draw of the servo driver
4. Connect the servo driver to the servo motor

5. Read the power (W) draw of the servo from the USB digital tester meter in the following state:

   • Idle (no movement)
   • Active (moving to some angles)

Power Consumption of Servo Driver & Tester

  1. Connect the digital tester meter to power source (USB port)
  2. Connect the USB digital tester meter to the servo driver
  3. Read the power (W) draw of the servo driver

Result:

Device	State	Power (W)
Servo Driver	Idle	0.10

Power Consumption of Micro Servo DF9GMS

  1. Connect the micro servo to the servo driver
  2. Read the power (W) draw of the micro servo in the following state:
     - Idle (no movement)
     - Active (rotated to some specified angles)

Idle state : 0.035 watts (0.135W - 0,1W)

From the video, we can see that when we first attach the micro servo, the power draw increases from around 0.1 watts to approximately 0.135 watts. Since this measurement includes the power consumption of both the servo motor and the servo driver, then the power consumption of the micro servo in its idle state is about 0.035 watts.

Active state : up to 0.45 watts (0.55W – 0,1W)

As we rotate the driver’s knob to its maximum, the power draw jumps from 0.135 watts to about 0.25 watts, reaching a peak of 0.55 watts. This means the operating power consumption of the micro servo ranges from 0.035 watts (idle) to 0.25 watts and up to 0.45 watts (peak performance).

Result:

Device	State	Power (W)
Micro Servo	Idle	0.035
	Active (peak)	0.45

Power Consumption of MG996R Hi-Torque Servo

  1. Replace the micro servo with the MG996R servo on the servo driver-tester.
  2. Read the power (W) draw of the MG996R servo in the following state:
     - Idle (no movement)
     - Active (rotated to some specified angle)

without load

Idle state : 0.05 watts (0.15W - 0,1W)

From the video, we can see that the power intake of this high-torque servo when not operated is around 0.15 watts, which means the power consumption in its idle state is approximately 0.05 watts.

Active state: up to 0.3 watts (0.4W - 0,1W)

As soon as we rotate the driver’s knob to its maximum, the power reading rises from 0.15 watts to about 0.32 watts, peaking at 0.4 watts. This means the active power consumption of this servo ranges from 0.15 watts (idle) to 0.22 watts and up to 0.3 watts (peak performance).

with load

Now, we want to compare how applying load or torque to the servo affects its power consumption, using the scenario from our Week 10 Machine Design assignment where we’re utilizing this servo to control the movement of plier arms. To do this, we will measure the power consumption in its idle state at different positions where varying torque forces are applied.

Idle - no torque: 0.05 watts (0.15W - 0,1W)

The idle state power consumption is consistent with the previously observed idle state, as no torque is applied yet at this point.

Idle - low torque: 0.26 watts (0.36W - 0,1W)

Even though the servo is still idle at this point, the power intake shows an increase because we have connected a rubber band between the pliers arm and the servo arm. This connection applies torque force, causing the power consumption to increase by 0.26 watts.

Idle - hiqh torque : 3.5 watts (3.6W - 0,1W)

Now, when we rotate the driver’s knob to move the pliers arm, the power intake jumps significantly to 3.5 watts. This increase occurs because, even though the servo is stationary, it still requires energy to maintain the position of the pliers arm, which results in higher power consumption.

Result:

MG996R Servo	State	Power (W)
(no load)	Idle	0.05
(no load)	Active (peak)	0.3
(low load)	Idle	0.26
(high load)	Idle	3.5

Result Summary

Power consumption comparison:

1. DF9GMS 360 Degree Micro Servo:

   • Idle State: Consumes approximately 0.035 watts.
   • Active State: Peaks at around 0.45 watts.

2. MG996R Hi-Torque Servo:

   • Idle State: Consumes about 0.05 watts when unloaded.
   • Active State: Peaks at 0.3 watts when unloaded.
   • Loaded (High Torque) State: Consumes significantly more power, up to 3.5 watts.

These data indicate that the micro servo has a relatively low power consumption even at peak performance. Meanwhile, the MG996R servo demonstrates higher power consumption, especially under load conditions.