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Is this solution not a little overengineered? Surely a simple mechanical on/off switch to detect when the door is open or closed would be enough?Algorithm:Door open: Trigger 'occupied'.Door closed: If 'occupied', keep status and light red lamp.Door open: Trigger 'unoccupied'.Door closed: If 'unoccupied', keep status and light green lamp.
What I do to measure an internal dimension is use two lengths of thin aluminium strip, clip them together with a strong spring clamp, release the clamp slightly while adjusting the strips to exactly fit inside the space, then finally measure the total length using a normal steel ruler.
Big wheels for suitcaseView Instructable »