No app install. No Play Store. No pairing. Open your phone’s browser, accept a certificate warning, and see live voltage readings with GPS coordinates — pushed over an encrypted WebSocket every 400ms. The path from Bluetooth to this point took 5 iterations, one afternoon, and an AI coding agent that tested every change on real hardware.
A complete Bluetooth voltage monitoring system — ESP32 reads voltage via ADS1115 ADC, broadcasts over BLE GATT, and an Android app displays live readings in real time. Built end-to-end in ~6 hours across 3 platforms.
The goal: measure voltage wirelessly and display it on your phone. Simple enough, but it means touching embedded C++, Bluetooth protocols, and Android Kotlin — all in one session. Here’s how the 6 hours broke down and what we learned along the way.
My next addition to previous projects Battery Powered Wifi IoT - Temperature, Humidity & Soil Moisture Sensors and Battery Powered ESP8266 IoT & Temperature Sensor is to make wifi configuration smooth and fast.
My new project consists of HW with cost under 20€. It is able to accurately measure electric power consumption and sends data via WiFi. Great source of knowledge is openenergymonitor.org which includes also Arduino library.
I have just made a prototype of ESP8266 (ESP-01) IoT temperature & humidity SI7021 sensor and also 2x three pin soil moisture sensors with only 0.006mA (6µA) current drain during the sleep.
I have several IoT sensors at home and now I came to the point that I would like to introduce some solid platform for storing sensor data and visualizing them. This post summarize all platforms that I tried, searched and evaluated.
I successfully run DHT22 battery ESP8266 temperature/humidity IoT sensor so my next project is a simple IoT Door Sensor. It is up and running and sending a simple event to my HTTP server via wifi chip ESP8266 (ESP-01 in my case). HTTP server is serving simple php script, that stores the data locally and also sending events to DWEET.IO and also sending email via Amazon SNS (AWS CLI api).
Since my latest ESP8266 temperature humidity IoT logger project is up and running I have decided to cut the last wire – power. There are more approaches how to make ESP8266 running on a battery, but why not to have a unique one… 😎
The idea is to use only 5µA AtTiny13A (5 microA 2-3V) during the idle time to decouple all other components from batteries! So really 0 power usage from all other components (power regulator, DHT22 sensor,..), since the more components the more idle power consumption. All other circuits should wake up only during limited time and then again turn off.
The sun is shining for free out there so why not to use it at least to charge the cell phone. I’ve searched cheep but usable solar panel for this purpose and tested it.
Specification of the solar panel from eBay for 8€:
The notice is marked:
This device can not store electricity, but only can charge your cell phones in the sun and this item must be under the strong light , otherwise the voltage is very small and many smart phones have battery protection so it can’t charge it.
I’ve bought BMP085 barometric pressure sensor and my goal was to get pressure and temperature data via I2C interface to my Cubieboard running linux (cubieboard2-lubuntu-installation).