Battery Driven Wifi Temperature Sensor

Some notes how to build a sensor that can be driven by 3 AA rechargeable battries for up to 1 year.

Overview

The web is full of examples how to build a temperature sensor. I want a sensor that is connected to my Wifi, can be driven by batteries for months and has an adequate resolution and precision.

This leads me to the following parts:

  • ESP-01
  • DHT 22
  • MCP1700
  • 3 AA rechargeable batteries, should be ‘ready-to-use’ (see below why)
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End-to-End Encrypted Messenger

You always thought that end-to-end encryption in your favorite messenger like WhatsApp is a big deal? Or is it even not supported? Well, here is an example showing how “new” this feature is and it works for 15 years now. Using a Unix system (macOS, Linux etc.) it is a one-liner to send encrypted messages using the commands nc and openssl.

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Raspberry Pi’s GPIO Speed

We all know that the raspi is a small and neat device for controlling our LEDs but sometimes I miss the possibility to add hardware to a “real” bus like a real CPU has. Sure it is possible to imitate a bus what is called bit banging. This way you can control external hardware like LCDs or writing data to external SRAM faster than utilizing SPI. So we were interested how fast the Pi can really switch these pins.

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