Lab – Compare Closed-Loop and Open-Loop Control Systems (Answers) Lab – Compare Closed-Loop and Open-Loop Control Systems (Instructor Version)


In this activity, you will compare closed-loop and open-loop control systems.


An open-loop control system does not monitor the output in order to determine what adjustments to make to the input. For example, when using a clothes dryer you might set the timer on the dryer to run the drying cycle for one hour. At the end of the hour, the dryer will stop. The level of dryness of the clothes will vary depending upon their level of wetness at the beginning of the cycle.

In a closed-loop control system, the output is measured to determine whether it is the desired output and adjust the input as appropriate. For example, if the clothes dryer is equipped with moisture sensors, the input may be a level of dryness that adjusts the cycle by extending the drying time until the sensors indicate the clothes are dried to a desired level.

Compare the systems listed in the table and determine if they are closed-loop or open-loop control systems. Briefly explain your selections in the space provided.

Systems Open/Closed Loop Explain Your Answer
Clothes dryer with moisture sensor Closed The moisture sensors provide measured output that is compared to a reference for desired dryness. The controller will extend the drying cycle until the input and output are equal.
Light switch to turn on the light OPEN You turn the light switch on and off. It turns the light on and off directly
Thermostat to keep a constant temperature CLOSED You set the thermostat to temperature you want it then the thermostat uses sensors to drop or lower the A/C or Heat to the desired temperature vou want.
Volume on a radio OPEN You turn the volume up and power is supplied to the radio
Vehicle ignition switch CLOSED It’s similar to the thermostat you turn it on then sensors/computer monitors the engine
and everything
Ceiling fan OPEN It is also like a light switch you directly turn the fan on and off
Clothes washing machine with water level sensor CLOSED The washing machine has sensors that monitors the water and temp you just pick the load, cycle, and what type of load it is.

From the Open Loop systems, select one and describe how you might make it a Closed Loop system:

Maybe for the ceiling fan I could make it to where like the thermostat sensors, so the fan won’t be continuously on until you turn it off.

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