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reorg lesson

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Peli de Halleux 2016-09-29 22:15:04 -07:00
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docs/projects/timing-gates.md
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@ -9,6 +9,28 @@ you will need better sensors such as [Hall Effect sensors](https://en.wikipedia.
### ~ ### ~
## How does it work?
The two gates are connected to the micro:bit and can detect a car passing through.
![](/static/mb/projects/timing-gates/sketchgates.jpg "Sketch of the gates")
As the car passes through the gate ``0``, it sends an event to the micro:bit through the [on pin pressed](/reference/input/on-pin-pressed) block.
The micro:bit records the time in a variable ``t0``.
![](/static/mb/projects/timing-gates/sketchgate1.jpg "Sketch first gate")
As the car passes through the gate ``1``, it sends an event to the micro:bit through the [on pin pressed](/reference/input/on-pin-pressed) block.
The micro:bit records the time in a variable ``t1``.
![](/static/mb/projects/timing-gates/sketchgate2.jpg "Sketch first gate")
The rest is a bit of math and physics. The time taken to cross the gates is computed as the difference of ``t1 - t0``.
By dividing the distance between the gates by the duration, we get the speed of the car!
![](/static/mb/projects/timing-gates/sketchmath.jpg "Sketch math")
## Materials ## Materials
* Carboard * Carboard
@ -37,27 +59,6 @@ control.eventTimestamp();
basic.showNumber(0) basic.showNumber(0)
``` ```
## How does it work?
The two gates are connected to the micro:bit and can detect a car passing through.
![](/static/mb/projects/timing-gates/sketchgates.jpg "Sketch of the gates")
As the car passes through the gate ``0``, it sends an event to the micro:bit through the [on pin pressed](/reference/input/on-pin-pressed) block.
The micro:bit records the time in a variable ``t0``.
![](/static/mb/projects/timing-gates/sketchgate1.jpg "Sketch first gate")
As the car passes through the gate ``1``, it sends an event to the micro:bit through the [on pin pressed](/reference/input/on-pin-pressed) block.
The micro:bit records the time in a variable ``t1``.
![](/static/mb/projects/timing-gates/sketchgate2.jpg "Sketch first gate")
The rest is a bit of math and physics. The time taken to cross the gates is computed as the difference of ``t1 - t0``.
By dividing the distance between the gates by the duration, we get the speed of the car!
![](/static/mb/projects/timing-gates/sketchmath.jpg "Sketch math")
## Building the gate ## Building the gate
The sensor is made by tapping two strips of fail on the cardboard as close as possible. The sensor is made by tapping two strips of fail on the cardboard as close as possible.