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.
(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!
The transparent screen will display the pH of the object detected and a pH-vs-Time Chart.
Hardware Connection
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
2. Drill a hole at the bottom of the shell for connecting the pH sensor cable.
3. Pass the pH adapter connector through the hole and fix it.
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.
5. Connect the transparent display to the display adapter, and connect the adapter to the C3 converter board.
6. Fix the C3 converter on the case. Solder wires for connecting the pH adapter, battery and RGB strip on it.
7. Plug ESP32-C3 onto the converter board.
8. Connect a 3.7V lithium battery.
9. Drill three holes at the top of the shell for RGB LED strip.
Oops! Two LEDs broken. Replace them with new ones.
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.
Cut the acrylic plates with laser.
Cut a square on the back cover and fix the acrylic plates onto them as shown below.
Be careful when using laser cutting machine.
Organize the wire and hardware inside the shell, and put the back cover lid on the shell.
Stick some black sticky paper on the shell to beautify it.
Connect the pH probe to it.
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
