The DST1020 targets the market for inexpensive digital thermostats, the most popular being the STC1000. There are two novel features to the DST1020:
uses DS1820B digital temperature sensor (well probably a Chinese clone);
two line display shows PV and SV simultaneously.
The DS1820B should be considerably more accurate and overcome the significant error in the conversion of NTC resistance to temperature in the other thermostats (experience is that the approximation used for the NTC characteristic is simple and inaccurate).
It is sold with brief and inadequate / incorrect user instructions.
A friend referred me to a ‘replacement’ for the HC-05 Bluetooth module, a JDY-31.
Above is a JDY-31 bluetooth module with header pins fitted. The physical design is poor, the header pins can be fitted from only one side (not plated through holes, no pads on the other side, probably to suit the base board below), and the black plastic part obscures the board labelling of the pins. Continue reading JDY-31 Bluetooth SPP module
Above is the HC-SR04 ultrasonic ranging sensor, it was purchased for around $6 from a local eBay seller and delivered within days. Note that there are somewhat similar looking things with a second board on the back and a different interface, the basic HC-SR04 as pictured suits this project.
Several of my projects use Bosch BME280 sensor chips for measuring temperature, pressure and humidity.
Some correspondents have expressed problems using BME280 modules that they bought online, and it is usually because they have been cheated by online sellers misrepresenting BMP280 as BME280.
My projects that include code to initialise and read BME280 humidity will fail on a BMP280… check to see if the humidity results returned look sane. A driver may read the ChipID and fault on the ID returned by a BMP280.
The Bosch chips are usually visually different, and most clones likewise.