Drinking Cola equals to Drinking Toilet Cleaner?

DFRobot Aug 07 2018 2162

I have heard of various adverse cola using methods long since. One of these methods is using as the toilet cleaner. Seriously? In the holiday, our member Mr. Mi with his son Little Mi made an electronic PH test paper with micro:bit. The test paper will tell you the truth!

The introduction indicates the highlight of the DF scientific kit is to upload data to IoT platform. The sample plate test figure above shows that the scientific kit shall include a PH sensor. The experimental design in the figure is to map the PH value into the steering engine and show the test result with pointer.

Required components of the project include:

Micro:bit×1

RGB lamp ring expansion board ×1

PH sensor ×1

RGB lamp ring expansion board was made two weeks ago.

From the front of expansion board, you can see the onboard 24 RGB LEDs and microphone.

From the back, you can see a buzzer, two P1, P0 IO expansion ports and corresponding reuse selection switch.
The kit supports PH2.0 and USB external power supply.
DF always has neat tricks for connection of expansion board and micro:bit.

Micro:mate adopts flexible PogoPin.

For RGB lamp ring expansion board, the nuts are directly embedded into PCB.

Under microspur, you can see nuts are not simply welded on PCB surface but embedded in PCB. The threads run through the board. This process is unclear, not common and simple.

Insulation paper is pasted on the front.

When screwed in, screws will contact the golden finger to achieve circuit connection with expansion board accordingly.

The installation is finished hereto.

Another main component PH sensor is introduced as follows:

Contents: including sensor, connection board and connection line. In this project, the connection line in the figure above needs to be replaced with double-end PH2.0-3pin connection line matched with ring RGB expansion board.

Electrode feature, immersed in protective liquid.

The switchover board was made early, so its version is V1.1 Arduino design. Its operating voltage is 5V. Now, there is new version V2, and its operating voltage is 3.3-5V, so it is more suitable to micro:bit.

The sensor is connected to the switchover board through BNC port.

Connect Sensor to Pi Port

P1 port is also used for onboard microphone, so the microphone needs to be forbidden.

Our program design is to provide prompt sound during operation, so the buzzer switch needs to be turned on (P2 port is forbidden at this moment).

RGB lamp ring is current consuming, so external power supply needs to be connected through PH2.0 or USB port.

Makeshift Program
We took some time in commissioning and improvement. Particularly, the max. input value of mapping module perplexed us, because PH sensor at hand was Arduino design. Its operating voltage is 5V, and we also lacked the technical data on PH sensor applying to micro:bit, so the value 700 is just a relative ideal value after we tested.

Mapping module phMap is used to switch on corresponding number of lamps according to the analog quantity read by P1.

Mapping module rgbMap is used to show corresponding “PH color card” simulated by RGB lamp rings according to the analog quantity read by P1.

Firstly, we selected following common liquid in daily life as the test objects:

Tap water, Coca Cola, rose red vinegar, milk, liquid detergent and toilet cleaner.

At first, test tap water for reference.
The reading is 436. End-point color of RGB lamp ring – light blue.

Then, test Coca Cola.
Only a LED of lamp ring is on (red) and the reading is 32!

For the rose red vinegar, the sensor reading is 71.
Two LEDs of RGB lamp ring are on. The end-point color is orange.

For devondale milk, the sensor reading is 359.
The end-point color of RGB lamp ring is green. Milk belongs to acid food.

For White Cat liquid detergent,
the sensor reading is 364 and
the end-point color of RGB lamp ring is green.

For the toilet cleaner, the reading is 26.
No lamps of RGB lamp ring are on.
It means it has strong acidity.

For baking soda, the reading is 464,
and the end-point lamp of RGB lamp ring is green.

The last test object is soap for cleaning clothes.
The reading is 573. The end-point color of RGB lamp ring is indigo blue!
It will become purple if the concentration is higher.
It conforms to our knowledge on “alkali soap”.

Conclusion: drinking cola = drinking toilet cleaner
This is tenable simply from the perspective of pH value.
I drank up the remaining cola to stay calm.
In device design, the sensor is sensitive to pH value.
Although no true PH value can be converted through a formula,
the analog quantity reading can be quantified
and the color card can be simulated through RGB lamp ring for visual display.

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