HTTP/2 301 date: Sat, 27 Dec 2025 06:14:31 GMT content-type: text/html location: https://hutscape.com/cactus/ server: cloudflare x-github-request-id: BA30:21D6A4:61469F:6CCB36:694F7947 accept-ranges: bytes age: 0 via: 1.1 varnish x-served-by: cache-bom-vanm7210023-BOM x-cache: MISS x-cache-hits: 0 x-timer: S1766816072.816379,VS0,VE198 vary: Accept-Encoding x-fastly-request-id: c38afe0752b6b59b9b0a1fef18ad22d2e2b1e62c cf-cache-status: DYNAMIC nel: {"report_to":"cf-nel","success_fraction":0.0,"max_age":604800} report-to: {"group":"cf-nel","max_age":604800,"endpoints":[{"url":"https://a.nel.cloudflare.com/report/v4?s=msQspYWMqcrAMdkN%2BhAABk5DV34rK8nVMGtQuQtusyeA55I842sH9qqWfsJ0B0ySMi8NkXYL5uXdrYFOFW0eb85eeFWzB0pmunhMxQ%3D%3D"}]} cf-ray: 9b46ada02bee3c04-BOM alt-svc: h3=":443"; ma=86400 HTTP/2 200 date: Sat, 27 Dec 2025 06:14:32 GMT content-type: text/html; charset=utf-8 server: cloudflare last-modified: Tue, 24 Dec 2024 12:38:22 GMT access-control-allow-origin: * expires: Sat, 27 Dec 2025 06:24:32 GMT cache-control: max-age=600 report-to: {"group":"cf-nel","max_age":604800,"endpoints":[{"url":"https://a.nel.cloudflare.com/report/v4?s=GdLaLNtOqiXuAAbipM160MW%2B95oxUA%2BUwqW1BbJx5PsqU%2BbDwIQBA1XqEQP8KtQU3FEAg%2F5xIc5LYy4rAxSocMecGc%2F5p%2F7UtwA4og%3D%3D"}]} x-proxy-cache: MISS x-github-request-id: 1379:2DDCFF:605029:6BD22B:694F7946 nel: {"report_to":"cf-nel","success_fraction":0.0,"max_age":604800} age: 0 via: 1.1 varnish x-served-by: cache-bom-vanm7210037-BOM x-cache: MISS x-cache-hits: 0 x-timer: S1766816072.092828,VS0,VE219 vary: Accept-Encoding x-fastly-request-id: 250ff9abda94063b5c198daa303e9408a9124673 cf-cache-status: DYNAMIC content-encoding: gzip cf-ray: 9b46ada20d473c04-BOM alt-svc: h3=":443"; ma=86400

Cactus

🌵 An indoor WiFi-connected temperature and humidity sensor 🍶

power LiPO

wireless WiFi

sensor Humidity

mcu ESP8266

battery life 1 month

bom items 36

bom cost USD $26.92

vendors 5

completed May 2019

• Start
• Code
• PCB
• Bill of Materials
• Design
• Power
• CSQ
• Resources

Downloads

Demo Code Schematic Layout ECAD KiCad files Gerber files Bill of Materials

Features

Read humidity and temperature values from the sensor Si7021
Read LiPo battery levels
Display the current humidity value through the on-board LEDs
Wakeup every 6 hours or on button press to read the sensor and send data to the cloud
Sleep after sending data to IFTTT
Check for stored WiFi credentials upon waking up and connect back to the store WiFi
Connect to WiFi with the stored credentials
Setup an AP mode if WiFi cannot be connected
Send sensor and battery values to IFTTT if WiFi is connected
Wait for 5 minutes in AP mode is WiFi is not connected
Sleep after waiting for 5 minutes in AP mode
Charge the LiPo by plugging in the USB cable into the battery shield

Getting Started

Step 1

Setup an IFTTT webhook to receive a POST request with data and add a row to a Google Spreadsheet.

Step 2

Access Point

Connect to the WiFi access point Cactus {UNIQUE_MAC_ADDRESS}.

Go to the web page https://cactus.local to fill in the WiFi credentials and IFTTT webhook key.

Step 3

Update Google Sheets with the data

Press on-board button or wait for the Google Sheet to update with a new row with a periodic update to the cloud.

Maintenance

⚠️ USB Connectors on WeMos D1 Mini vs WeMos battery shield

• Do not plug in the USB cable on WeMos D1 Mini while the battery shield is on the PCB
• Flashing firmware: Remove the battery shield from the PCB and use the USB cable on the WeMos D1 mini

Charge the LiPo by plugging in the USB cable into the battery shield