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DIY a pH Meter Using DFRobot pH Sensor and Transparent Display

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Background

On a hot summer day, nothing better than drinking an ice-cold glass of lemonade when you’ve been playing in the heat for several hours. We know that a fresh lemon itself doesn’t taste quite the same as it does when you mix it with sugar and water, but, how sour is a lemon exactly? Well, the face below may tell the truth. Just kidding! Never try that on your kids. As a maker, I choose to figure it out scientifically---detect its pH.  

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                                                                            (Image from Mashed.com)

Design Idea

This pH sensor I just got from DFRobot has a lab-grade probe with measurement accuracy of ±0.1 at 25℃, which is perfect for my project. Also, I want the sensor readings to be showed on a screen. Since lately I’ve been trying a new Transparent Display from DFRobot, I decided to use it for data display here. Besides, a RGB LED strip is used to indicate pH values with different colors according to the pH vs Color table. Put all hardware into a cool shell, and start detecting!

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The transparent screen will display the pH of the object detected and a pH-vs-Time Chart.

HARDWARE LIST
1 Beetle ESP32-C3
1 Analog pH Sensor Kit V2
1 1.51” OLED Transparent Display with Converter
1 RGB WS2812 LED Strip
1 3.7V Battery
1 Shell

Hardware Connection

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pH Adapter (to) ESP32-C3

pH Probe (to) pH Adapter

Transparent Display (to) Display Adapter

Display Adapter (to) ESP32-C3

RGB LED Strip (to) ESP32-C3

3.7V Battery (to) ESP32-C3

 

Assembly

1. Drill a hole on the front side of the shell to install power switch

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2. Drill a hole at the bottom of the shell for connecting the pH sensor cable.

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3. Pass the pH adapter connector through the hole and fix it.

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4. Place the transparent display into the shell window, put a thin plastic film onto it and apply some hot melt adhesive to the edges.

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5. Connect the transparent display to the display adapter, and connect the adapter to the C3 converter board.

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6. Fix the C3 converter on the case. Solder wires for connecting the pH adapter, battery and RGB strip on it.

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7.  Plug ESP32-C3 onto the converter board.

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8. Connect a 3.7V lithium battery.

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9. Drill three holes at the top of the shell for RGB LED strip.

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Oops! Two LEDs broken. Replace them with new ones.

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Eh, the lighting effect disappointed me and the transparent display is not transparent.

Redesign a structure to let the content on the transparent display can be viewed on both sides.

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Cut the acrylic plates with laser.

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Cut a square on the back cover and fix the acrylic plates onto them as shown below.

Be careful when using laser cutting machine.

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Organize the wire and hardware inside the shell, and put the back cover lid on the shell.

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Stick some black sticky paper on the shell to beautify it.

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Connect the pH probe to it.

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Then all done.

The pH of the lemon detected is 2.3, which is quite sour. And I also detected several other stuff.

 

The article was first published in dfrobot.com.cn, 2022/06/30

URL: https://mc.dfrobot.com.cn/thread-313523-1-1.html

Author:派大星ym

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