# Servo motor duty cycle vs. supply voltage

• 280Z28
In summary, the speaker is using a servo motor controlled by a PID controller to generate a square wave with varying duty cycle. The supply voltage is 5.17V with a 1V drop across the low side driver, resulting in an effective 2V source. The controller is set to 50% duty cycle to keep the servo open to position A, but a reference source suggests that a duty cycle of 14-26% is necessary. Based on the speaker's calculations, the servo is built to handle a supply voltage of 9-15V. However, it depends on the nature of the limit, with an instantaneous limit not affected by duty cycle and an average limit in line with the calculation.
280Z28
I have a servo motor that I'm controlling with a simple PID controller for a constant frequency square wave with varying duty cycle. My supply voltage is 5.17V with ~1V drop across my low side driver. The controller sits right around 50% duty cycle to keep the servo open to position A. A reference source states that it should take a 14-26% duty cycle to keep it open to position A. What should the supply voltage be, counting again a 1V drop across the driver?

By my calculation, I've applied an effective (time averaged) 2V source.

2/.26 + 1 = 8.7V
2/.14 + 1 = 15.3V

Is this the correct calculation/conclusion that the servo is built to handle a 9-15V supply?

280Z28 said:
Is this the correct calculation/conclusion that the servo is built to handle a 9-15V supply?

That depends on the nature of the 9-15V limit. If it is instantaneous (unlikely) then duty cycle doesn't matter. If it is average (more likely) your calculation is correct.

## What is a servo motor duty cycle?

A servo motor duty cycle is the ratio of the time the motor is on to the total time of a full cycle. It is typically expressed as a percentage, with 100% being a continuous or always-on operation.

## How does the supply voltage affect a servo motor's duty cycle?

The supply voltage directly affects the duty cycle of a servo motor. As the supply voltage increases, the duty cycle also increases, resulting in the motor being on for a longer period of time during each cycle. Conversely, a decrease in supply voltage will result in a decrease in duty cycle.

## Why is it important to understand the relationship between servo motor duty cycle and supply voltage?

Understanding the relationship between servo motor duty cycle and supply voltage is crucial for proper motor operation. If the duty cycle is too high, the motor may overheat and burn out. On the other hand, if the duty cycle is too low, the motor may not be able to perform its intended function. By adjusting the supply voltage, the duty cycle can be controlled to ensure optimal motor performance and longevity.

## How can I determine the ideal supply voltage for a specific servo motor's duty cycle?

The ideal supply voltage for a servo motor's duty cycle can be determined by consulting the motor's datasheet or by conducting experiments with different supply voltages and monitoring the resulting duty cycle. It is important to note that the ideal supply voltage may vary depending on the load and operating conditions of the motor.

## Are there any risks associated with changing the supply voltage to adjust the servo motor's duty cycle?

Yes, there are risks associated with changing the supply voltage to adjust the servo motor's duty cycle. If the supply voltage is too high, it can damage the motor or other components in the circuit. Additionally, changing the supply voltage may also affect the accuracy and precision of the motor's movements. It is important to carefully consider the appropriate supply voltage for the desired duty cycle and consult the motor's datasheet before making any adjustments.

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