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.. _1.12_scratch:

1.12 Water Lamp
================

Today, we will use LED Bar Graph, Raspberry Pi and scratch to make a Water Lamp.

The LED Bar Graph will light up in order with the direction of the arrows on the stage.

.. image:: img/1.12_header.png

Required Components
------------------------------

In this project, we need the following components. 

.. image:: img/1.12_list.png

It's definitely convenient to buy a whole kit, here's the link: 

.. list-table::
    :widths: 20 20 20
    :header-rows: 1

    *   - Name	
        - ITEMS IN THIS KIT
        - LINK
    *   - Raphael Kit
        - 337
        - |link_Raphael_kit|

You can also buy them separately from the links below.

.. list-table::
    :widths: 30 20
    :header-rows: 1

    *   - COMPONENT INTRODUCTION
        - PURCHASE LINK

    *   - :ref:`cpn_gpio_board`
        - |link_gpio_board_buy|
    *   - :ref:`cpn_breadboard`
        - |link_breadboard_buy|
    *   - :ref:`cpn_wires`
        - |link_wires_buy|
    *   - :ref:`cpn_resistor`
        - |link_resistor_buy|
    *   - :ref:`cpn_bar_graph`
        - \-

Build the Circuit
-----------------------

.. image:: img/1.12_image66.png

Load the Code and See What Happens
-----------------------------------------

Load the code file (``1.12_water_lamp.sb3``) from your computer to Scratch 3.

By clicking on **Arrow1**, the LEDs on the LED bar are lit in sequence from the left to the right (one at a time) and then off. Click **Arrow2** and the LEDs light up in the opposite order.

Tips on Sprites
----------------

Delete the default sprite and choose the **Arrow1** sprite.

.. image:: img/1.12_graph1.png

Here we will need 2 **Arrow1** sprites, which can be done with the duplicate button.

.. image:: img/1.12_scratch_duplicate.png

Click on the **Arrow 2** sprite and change the direction of the arrow by selecting costume 2.

.. image:: img/1.12_graph2.png


Now let's make a variable.

.. image:: img/1.12_graph3.png


Name it as **num**.

.. image:: img/1.12_graph4.png


Follow the same method to create a list called **led**.

.. image:: img/1.12_graph6.png


After adding, you should see the **num** variable and the **led** list on the stage area. 

Click **+** to add 10 list items and enter the pin numbers in order (17,18,27,22,23,24,25,2,3,8).

.. image:: img/1.12_graph7.png

Tips on Codes
--------------

.. image:: img/1.12_graph10.png
  :width: 300

This is an event block that is triggered when the current sprite is clicked.

.. image:: img/1.12_graph8.png
  :width: 300

The initial value of the **num** variable determines which LED is lit first.

.. image:: img/1.12_graph9.png


Set the pin corresponding to **num** in the led list to low to light the LED, and then set the pin corresponding to **num-1** to high to turn off the previous LED.