1. Open/Closed Loop Systems
1/8
Open/Closed Loop Systems
● INPUT: ● You run the mile every afternoon
● You record time with stopwatch
● OUTPUT:● Stopwatch times each mile ● PROBLEM: Your times do not improve
FEEDBACK
● INPUT: You run a mile on track
Coach times your run
Coach gives you ● FEEDBACK (tips)
● OUTPUT: Your mile time improves

2. Open Loop System: 2/8 OUTPUT INPUT
ON / OFF
● One-way connection between INPUT and OUTPUT
2/8
Water ON / Water OFF

3. Open Loop System: 3/8 ● One-way connection between INPUT and OUTPUT
●NO direct connection between OUTPUT and INPUT
INPUT: ON/OFF
OUTPUT: ON/OFF
EXAMPLE: light + switch
●Open Loop System: A control system with no automatic FEEDBACK loop

4. Closed Loop System:
4/8
●A control system with an automatic feedback loop
●A direct connection between output and input
EXAMPLE: a toaster w/light – medium – dark settings
FEEDBACK: setting reached – toast pops up
light
OUTPUT: toast is way you want it
medium
dark
INPUT: set light, medium, dark
●Closed Loop System: A control system with an automatic FEEDBACK loop

5. water temperature control temperature sensor/control
Closed Loop System:
5/8
●A control system with an automatic feedback loop
● A direct connection between OUTPUT and INPUT
“Heat water to 140 degrees”
140 ○
Water heater
+ -
“At 140: Stop heating.”
“Under 140: Start heating.”
water temperature control
feedback
temperature sensor/control

6. INPUT (infrared waves)
Closed Loop System:
6/8
● A direct connection between OUTPUT and INPUT
EXAMPLE: outdoor lights w/motion detector
Electric eye detects infrared
Thief : near home at night
INPUT (infrared waves)
FEEDBACK
Spotlights turn ON. OUTPUT
●Closed Loop System: A control system with an automatic FEEDBACK loop

7. Closed Loop System: 7/8 ● A direct connection between OUTPUT and INPUT
EXAMPLE: daylight sensor controls interior lighting
Natural daylight thru windows
Ceiling-mounted daylight sensor
OUTPUT
low/no natural light: ADJUST lighting
INPUT
high natural light: ADJUST lighting
●Closed Loop System: A control system with an automatic FEEDBACK loop

8. Open/Closed Loop Systems
8/8
Open/Closed Loop Systems
Below: 20 everyday technology systems/sub-systems
Which are Open-Loop Systems? – ‘O’ Which are Closed-Loop Systems? – ‘C’
[1] Electric fan
[2] Foot-operated gas pedal
[3] Cell phone
[4] Thermostat
[5] Door bell
[6] Food processor
[7] Car cruise control
[8] Lawn sprinkler system
[9] Car automatic headlights
[10] xBox /Playstation
[11] ‘Active’ noise-canceling headphones
[12] Volume control on headphones
[13] Window shade
[14] Central Air Conditioning
[15] Electric toothbrush
[16] Car anti-lock braking system
[17] Hair dryer
[18] Traffic lights
[19] Foot-operated brake pedal
[20] Programmable croc pot w/temp probe