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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
* Carboard
@ -37,27 +59,6 @@ control.eventTimestamp();
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
The sensor is made by tapping two strips of fail on the cardboard as close as possible.