Logic Gates — AND, OR, NOT

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AND Gate — All Conditions Must Be True

Home geyser example:

Geyser should turn ON only when ALL of these are true:

Someone is in bathroom (occupancy = TRUE)
AND water tank is not full (level = FALSE / space available)
AND time is between 5AM and 11PM (schedule = TRUE)

All three must be true. Any one false → geyser stays off.

BMS example — AHU start:

Fire alarm = Normal (TRUE)
AND Smoke detector = Clear (TRUE)
AND Schedule = Active (TRUE)
AND Emergency stop = Not pressed (TRUE)
────────────────────────────────────
All TRUE → Fan starts
Any FALSE → Fan does not start

OR Gate — Any One Condition Is Enough

Home alarm example:

Alarm sounds if ANY of these happen:

Front door opens OR
Back door opens OR
Window sensor triggers OR
Motion sensor detects movement

Any ONE is enough. All false → no alarm. Any one true → alarm sounds.

BMS example — general fault alarm:

Chiller 1 trips OR
Chiller 2 trips OR
Primary pump fails OR
Cooling tower fan faults
────────────────────────
Any one → Alert to engineer immediately

NOT Gate — Reverses the Signal

Garden light example:

Light sensor gives TRUE = daylight present.
Garden light should be ON when it is DARK = sensor is FALSE.

NOT gate flips the signal:

Sensor TRUE (daylight) → NOT → FALSE (light stays off)
Sensor FALSE (dark)    → NOT → TRUE (light turns on)

BMS example:

Valve closed feedback = TRUE
NOT gate → Valve open = TRUE (valve is NOT closed)
Used constantly to match signal polarity with control intent

Logic Gates — AND, OR, NOT

AND Gate — All Conditions Must Be True

OR Gate — Any One Condition Is Enough

NOT Gate — Reverses the Signal

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