The cup model
A cup of soil, a cup of water, and the bare electronics. Simple on purpose: it let us test the idea fast and find the real faults early.
LOG 01 · THE PROBLEM
Busy days, thirsty corn.
entry: why we started · dunia sebenar
Our school has a corn garden. Encik, our school gardener, looks after the whole compound: he trims the flowers, cuts the grass, tidies the grounds, and used to water the corn himself. With so many jobs, the corn sometimes gets less water than it needs, and in Miri's afternoon heat the leaves wilt in a day or two. We want to help Encik, never replace him. Our system is built for the next planting season.
🎤
PHOTO: Interviewing Encik about the corn
Real photo coming soon
We asked him ourselves, in Bahasa Melayu.
Three moments from our interview at the corn garden:
"Kalau waktu saya terpaksa tebas rumput, untuk menyiram jagung itu saya terpaksa kasih tinggal."
"When I had to cut the grass, I had to leave the corn unwatered."
"Kalau tanah terlalu kering, dia akan cepat layu, dan jika dia sudah ada buah, buah dia tidak cantik."
"If the soil is too dry it wilts fast, and if it's fruiting, the cobs don't turn out well."
"Di waktu cuti sekolah, memang tidak ada orang yang akan siram dia. Kecuali kalau ada waktu budak cuti, saya yang kerja, saya akan pergi siram dia."
"During the school holidays, no one waters it. Unless I'm working while the kids are off — then I'll go and water it."
1–2 days
without water in Miri's heat and the young corn already droops
850 → 470
our sensor's reading for dry soil vs wet soil, measured by us
16 days
the mid-year school holiday. Encik told us the corn gets watered then only if he happens to be working
LOG 02 · OUR JOURNEY
Five steps, then around the loop again.
entry: the IDEAL engineering loop
I
Identify · Kenal pasti
We saw the corn wilting and asked why, and who it affects.
Empati + Mendefinisi masalahD
Define · Takrif masalah
We interviewed Encik in Bahasa Melayu and defined the real problem: the corn's watering is inconsistent because one caretaker looks after the whole school.
Mendefinisi masalahE
Explore · Teroka idea
We compared four ideas (timer, battery, solar + sensor, rainwater) and chose solar + sensor: the sun is free, and it only waters when the soil is dry.
Menjana ideaA
Act · Bina prototaip
We built v1 (a cup model), then v2 with a bamboo tower, a recycled tank, a sprinkler and an Arduino, and wrote the code over five versions.
PrototaipL
Look Back · Uji lari
We tested and fixed real problems: a backwards relay, a jittery pump, a mis-connected tube. Every fault became a fix.
Uji lariThe build diary, in photos
Or watch the whole journey in 5 minutes
▶
Video coming soon
Our 5-minute project video will be added here soon.
Our 5-minute project video will be added here soon.
LOG 03 · TWO MACHINES
We built it twice, on purpose.
entry: prototype v1 → v2 · uji lari
The field-ready build
Bamboo tower and canopy, recycled tank, misting sprinkler, protected electronics box and a drainage tray. The machine we would put in the cornfield.
Every fault in v1 became a fix in v2
| What we saw in v1 | What we changed in v2 |
|---|---|
| The water came out in single jets instead of spreading evenly | A misting nozzle and canopy spread it much wider. Not a fine mist yet: our pump is small, so a bigger pump is next on our list |
| Nothing held the water above the plant | A bamboo tower and canopy lift the sprinkler over the leaves (recycled, RM 0) |
| The electronics sat bare on the table | A recycled box protects the Arduino and relay |
| A drinking cup was too small to be a real tank | A recycled cylinder tank: no stored power, the tank stores water instead |
| Demo water spilled, and there was no safe off | A drainage tray + a 3-position switch: solar / OFF / spare battery |
How the machine thinks
One machine, two separate circuits that meet only at the relay:
CIRCUIT A The brain · it thinks
🔋
6V battery box (borrowed from RBT)
Steady power for the brain, so it never blinks
↓
🤖
Arduino UNO: the brain
Reads the sensor on pin A0, decides, commands pin D7
↓
🌱
Soil sensor (YL-69): the tongue
Tastes how dry the soil is (reading 0–1023)
CIRCUIT B The muscle · it waters
☀️
Solar panel (6V 1W)
Drives the pump straight from the morning sun · a 3-position switch can swap to a spare battery for indoor demos
↓
🔌
Relay (ACTIVE LOW): the handshake
The only place the two circuits meet · switches on the brain's command
↓
💧
Water pump → sprinkler
Waters the corn only when it is needed
🤝 Why two circuits? When the pump starts, it gulps current. On one shared circuit that gulp restarted the brain — we saw it happen. So the grounds are kept completely separate, and the pump can never crash the brain.
💡 Why solar in the morning? Corn is best watered from 6 to 10am, exactly when the solar panel makes power. So the pump runs straight off the sun: no stored power, the tank is our battery. A small battery box lets the pump run when there is no strong sun, for example indoors during a demo, and the Arduino brain runs on its own 6V battery box so it stays steady.
LOG 04 · THE CODE
One program. Five versions. Five real lessons.
entry: test, fail, fix, repeat
Every version changed because a real test surprised us, not because a plan said so. Tap through the story:
Just read the soil
int m = analogRead(A0);
Serial.println(m);
// probe in air ≈ 1023 · pure water ≈ 390First we only listened to the sensor. We tested air, dry soil, wet soil and water to learn its language before writing any rules.
One threshold
if (m > 600) {
// dry → water it
} else {
// wet → wait
}Then a rule: above 600 means dry, so turn the pump on. Simple, and it worked, on paper.
The relay worked backwards
digitalWrite(relayPin, HIGH);
// we expected pump ON…
// the pump went OFF?!We added the relay, and HIGH switched the pump off, not on. Our relay is wired in reverse: a real part beat our assumption.
Active-low fix
digitalWrite(relayPin, LOW);
// LOW = pump ON (active-low)We checked the relay's datasheet and flipped the logic. Lesson: never trust a template, test the real part.
Two numbers, with a gap
if (moisture > 600 && !pumpState) {
digitalWrite(relayPin, LOW); // pump ON
} else if (moisture < 500 && pumpState) {
digitalWrite(relayPin, HIGH); // pump OFF
}
// between 500–600 → hold, no flickerNear one threshold the pump flicked on and off. Two numbers with a gap between them let it finish the job calmly. We chose 600 and 500 ourselves, from 20+ tests.
Our calibration data (20+ tests)
⚙️ Thresholds: pump turns ON above 600 (dry) and OFF below 500 (wet). The 500–600 gap is the hold zone that stops the pump flickering.
LOG 05 · SIX SUBJECTS
Six subjects built one machine.
entry: integrasi kurikulum · 49 SK/SP mapped verbatim
3 STEM + 3 non-STEM, all from the official Tahun 5 / Year 5 SJK curriculum documents. Every standard below is quoted from the official DSKP. Tap a subject to open it.
SainsThe sun is a source of energy; morning is the best time to water → the solar panel
- SK 1.1 Kemahiran Proses Sains: observing the corn, measuring 0–1023 readings, interpreting our calibration data
- SK 5.1 Sumber Tenaga Elektrik: the 6V 1W solar panel as a source that produces electrical energy
- SK 5.3 Keselamatan Pengendalian Peralatan dan Penjimatan Elektrik: free solar energy, and the system runs only when the soil is dry
RBTMicrocontroller + code + renewable energy + urban farming → the Arduino brain
- SK 5.1 Reka Bentuk Produk Menggunakan Tenaga Boleh Baharu: a product powered by renewable energy
- SK 6.3 Asas Reka Bentuk Pengaturcaraan: writing and fixing our program logic
- SK 6.4 Pembangunan Atur Cara Dalam Mikropengawal ⭐: our Arduino UNO is exactly this standard
- SK 7.1 Reka Bentuk Pertanian Bandar: an irrigation design for a real garden
MatematikWe managed the money (RM 79.58) and drew our data charts
- SK 3.1 钱币的基本运算: adding up our component costs
- SK 3.5 解决问题: making the budget fit RM 79.58
- SK 5.1 长度: measuring tube lengths and tower height
- SK 8.2 众数、中位数、平均数和极差: reading our sensor data
- SK 8.3 解决问题: turning data into thresholds (600 / 500)
Matematik at SJK(C) schools is taught in Chinese; these are the official SJKC DSKP standards.
B. MelayuWe interviewed Encik in Bahasa Melayu to understand the real problem
- SK 1.1 Mendengar dan memberikan respons semasa berkomunikasi dalam situasi formal dan tidak formal
- SK 1.2 Bertutur untuk menyampaikan maklumat dan idea bagi pelbagai tujuan
- SK 1.3 Bercerita, dan menceritakan perkara yang didengar, ditonton dan dibaca dengan sebutan dan intonasi yang betul
EnglishOur report, this website, and presenting to you today
- CS 2.1 Communicate simple information intelligibly
- CS 2.2 Use appropriate communication strategies
- CS 2.3 Communicate appropriately to a small or large group
- CS 4.2 Communicate basic information intelligibly for a range of purposes in print and digital media
- CS 4.3 Communicate with appropriate language form and style for a range of purposes in print and digital media
P. MoralCare for the people who care for our school: help Encik, never replace him
- SK 2.0 关注社区的需求和福利: noticing what our school community needs
- SK 3.0 身为社区成员的责任: taking responsibility as members of the community
- SK 4.0 感谢社区成员的功绩与贡献: thanking Encik for what he does every day
- SK 12.0 社区生活里的合作行为: working together: two builders, six subject teachers, one gardener
Pendidikan Moral at SJK(C) schools uses the SJKC DSKP with community-themed standards.
LOG 06 · COST & GREEN
We managed the budget ourselves.
entry: wang · masa · sumber lain
ItemRM
- Arduino UNO R3 + cable the brain38.61
- Solar panel (6V 1W)12.51
- Pump, soil sensor & relay10.17
- Jumper wires (3 packs)9.99
- Misting nozzle + silicone tube7.40
- Mini breadboard0.90
- Tank, tower & containers recycled!0.00
TOTAL funded by our school PIBGRM 79.58
⏱ Masa · what we put in
- Build sessions at school, wiring step by step
- 20+ sensor tests to calibrate dry, wet and water
- Interview and field visits to the corn garden
- 5 code versions, each fixed after a real failure
- August: putting Version 1 back together, testing both machines and rehearsing — the dates are in this logbook
♻ Sumber lain · borrowed & recycled, RM 0
- 2 battery boxes borrowed from Panitia RBT
- Recycled containers: water tank, electronics box, soil tray
- Bamboo sticks for the tower and canopy
- Long wires and soldering help from an elder brother
- Cable ties and tape from home
☀️
Renewable energy
Runs on solar, no mains electricity.
💧
Water saving
Waters only when the soil is actually dry.
🎋
Recycled build
Bamboo, recycled containers, borrowed parts.
🌍
Bigger picture
Supports SDG 6, 7, 12 and Sarawak's PCDS 2030 push for renewable energy and growing more food.
Anyone can rebuild this for RM 79.58 in parts plus recycled containers. That was the point: a real fix a school can actually afford.
LOG 07 · TRY IT YOURSELF
Be the sensor 🎛️
entry: our real logic, in your hands
Drag the slider to change how dry the soil is. Watch the pump turn on and off using the exact thresholds from our real Arduino code.
Soil-Moisture Pump Simulator
Higher reading = drier soil. Two thresholds with a hold zone keep the pump from flickering.
Sensor reading (A0)
720
PUMP OFF
// our real Arduino logic
if (moisture > 600 && !pumpState) { pump ON; }
else if (moisture < 500 && pumpState) { pump OFF; }
// between 500-600 → hold its last state
Your turn · Giliran anda
Test what you learned
Eight quick questions about our system. Finish to earn your own certificate, by email, QR or PDF. It takes about a minute.
▶ Start the quizLOG 08 · VISITORS' PAGE
Sign our logbook 🙋
entry: written by you
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Guru Pembimbing
Cikgu Davin
SJK Tukau, Miri, Sarawak