Micro Servo- Tower Pro MG90S Current Test

By Nhan Nguyen (Electronics)

In order to figure out the uSpiderbot battery size and power requirements we need to know how much power the uSpiderbot will consume. To figure this out we performed a current test on our servos. Because our uSpiderbot utilizes 18 servos we needed to use breakout boards. We chose to go with the Adafruit Servo Driver to use as our breakout board. The test was performed based off PWM adjustments instead of angles. The following image shows how the servos were wired up to the breakout boards.

Hook Up:

The 18 servos were split up between the two breakout boards, meaning there are 9 servos on each board. This implementation will be used on the final uSpiderbot to split between the left and right side of the uSpiderbot to reduce clutter. The first breakout board was connected to the Arduino micro via 5V, GND, SDA, and SCL. The second breakout board was then daisy chained to the first board. We were able to hook up a multimeter in series with the power supply connected to the breakout boards in order to read the current.

Fritzing1

Results:

We performed two current tests on the servos, the idle current test and the stall current test. Idle current is the current that the servos use up when they’re not in motion. The stall current is the maximum current draw of the servo. After performing the current tests on the servos, it was observed that the servos utilize the average amount of current between idle and stall.

Idle current:
The idle current at 6V turned out to be 250 mA.

Torque vs Current:

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In conclusion, the graph displays the current consumption increasing as the torque increases ranging from 1 to 1.6 kg.cm. The current consumption increases approximately 40 mA per increments of 0.15 kg.cm.