I've created this to have easiest way to establish environment monitoring across the house
the idea is to have a wall outlet type plug with everything on board
and I like to do small things
The board is less than 50 x 50 mm
It contains AC-DC power supply with resettable fuse, 3.3V LDO, arduino based on atmega328, radio, LED, and two slots, one for DS18B20 and the second one is for DHT11/DHT22

The real consumption measured by RMS wattmeter is just 0.3W

Working prototype:

A LEGO set:

Everyone is need some kind of power supply for the project. Some time AC-DC is needed.
From a few years of hobby I did a following list for myself:

1. list item isolated AC-DC
   1.1 purchased as adapter
   1.2 purchased in separate box
   1.3 purchased to be put on PCB
2. nonisolated AC-DC
   2.1 soldered capacitor based
   2.2 soldered switching inductor less
   2.3 soldered switching with inductor

More or less a coprehensive listm, with proc and cons depending of the project.
I prefer to solder things, but you see that I put all isolated as purchased. It is all about transformers.
I'm scared about transformers - you need to properly design it, you need to wire it and build.

Now I can tell that I do not scared any more)

But to simplify start I ordered transformers build for the 5/12V output at power up to 3W. It is best sutable for most of my applications.

A testing board was created:

soldered and tested:

result of test as expected. at 13V output I coould get 3W of power with moderated heating

schematic is based on LNK364

By next step I will order PCB for my DIN Rail LEGO project:

esp8266 based thermostat for heating system

It was an idea a year ago to test an idea of simple and smart clock
this clock will need no attention because it will be set and synchronized by MySensors support.

The previous version a year ago was running my port to Plain C MySensors 1.3 and able to fit into atmega8
Now it is upgraded to arduino + Mysensors 1.4.1 but for this I had to also upgrade to atmega328p (same as in arduino UNO)
(google translated article is here https://translate.google.com/translate?sl=ru&tl=en&js=y&prev=_t&hl=ru&ie=UTF-8&u=http%3A%2F%2Fradiokot.ru%2Fcircuit%2Fdigital%2Fhome%2F176%2F&edit-text=)

Simple - means simple. MCU itself is driving 7 segment display. I'm not using any external RTC clock but I'm using a special asynchronous mode of atmega328 and external 32768 so called clock crystal.

DS18B20 and light sensor are on board.

Display driver contains a software PWM with 0-15 level of the light intensity.
Intensity is adjusted by light.

schematics is here http://radiokot.ru/circuit/digital/home/176/01.png

ready

I need to have 4-5 ethernet gateways for my two installations (one for the apartment and one for the house)

for this I'm developing a custom hardware
it is a PCB with AC power supply, atmega128A, step-down for 5V (for atmega128), step-down for 3.3V (for radio and ENC28J60) ,
4 leds (powe, error, TX, RX), ISP connector, 3.5mm jack to connect Serial, connector for NRF24L01 and connector for ENC8J60

to use atmega128A a have to adjust Arduino configuration using some presets from the Internet.
currently I'm running a standard Ethernet Gateway 1.4.1

The plan is to add menu style configuration from the Serial connection for ethernet network parameters and for MySensors parameters.
The plan is to propose a patch to MySensors to support Gateway ID - this will add support to the project to have multiple gateways without need of a hack. Otherwise devices from different gateways will conflict on the air.

if you can recognize the marking on xtal you will find 5v with 16Mhz and 3.3V with 8mhz

assembled for particular applications

I'm opening this topic for the discussion of the Mysensors board.
We are very close to production this why an open discussion is very important to fix critical things and to understand your interest on the board.
The price will very depends on volumes. But lets come to that later.
Preliminary characteristics:

50x50 mm size
on board AAA battery holder
very efficient step to power up at 3.3V from any single AAA (alkaline or Ni-MH/CD)
atmega328p running at 1MHz from internal oscillator with ability to speed up to 8MHz on the fly
NRF24L01 with antenna
solar power switch, connect external solar panel 0.8-5.5V and solar will be the main power while solar voltage is higher than battery
one I2C GROVE connector which can be used as a connector to A5/A4
one GROVE analogue connector to A0/A1
one GROVE digital connector to D2/D3
high precision very low power I2C temperature sensor with ability to wake up MCU at temperature alertt
one red LED

to program you will need an external USB<->UART like you need to program pro-mini

@scalz thanks a lot for comprehensive recommendation. Will take a look, all is new for me

My iot network is requiering development a management console based on web interface
To control, analyse and configure

Access to network is throuth webservices

Any ideas of simple to start platform for this project?
My basic idea is php with some libraries
But may be a specially designed framework exists

@jeremushka I do have this footprint in altium but the library is big. do you know how to export a single element?

Linux Router https://github.com/axillent/swi_appserver

just published my libraries
anyonw is welsome on review and comments https://github.com/axillent :

• list item stavrp C++ multiplafrom suport library, platforms are at different level of support

• list item smartletsp C++ smart devices network

• list item swilib and integration of above two libraries with arduino framework

also from last
byteorder handling is build in
library allows to choose any order
I select bigendian because this is natural to my major MCU - STM8
on little endian platforms (like STM32, ESP8266 and ARM64) data is automatically translated

for esp8266 i made an universal bridge application
it can be used for both:

• single node, esp8266 is running a final application. on the photo above my thermostats to measure room temperature, report it and to send ON/OFF commands to heaters

• bridge. can be used to connect other type networks wirelessly to application server. UART is used for this + json translation. currently this is implemented to connect heating controllers located on each floor

main and failover servers can be configured
also each node is configured to handle from one to a few network segments. this allows simple routing from application server back to node
esp8266 is using ArduinoOTA and zero hardcording.
after fresh programming esp creates AP and smartphone can be used to preconfigure a node
any updates are keeping configuration except major updates there stored structure can be affected

application server is also support MQTT translation
etc. it looks like a routing between my network and MQTT server
RX/TX adresing are mapped to MQTT topic while message is translated into JSON:

made a few steps forward

launched ESP8266 node & bridge and STM32 bridge and TCP/IP router based on linux (orangepi)
bellow is my working example
list of supported platforms:

• STM8S/IAR
• STM32F0/Keil - draft
• ATMEL/Atmel studio - draft
• Arduino ESP8266
• Arduino STM32
• Linux/g++

i;m working on 2 libs. first is to handle platform dependant things. second is platform independant smart devices network
regardless platform and regardless communication hardware the framework allows to transfer messages using RX/TX notation with 16 bit global addressing.
Addressing is organized as 4096 segments where 4094 are 15 node segments each and 2 segments are for broadcadsting

framework allows to connect potentially absolutelly different communication hardware
currently i'm running:

• simple one wire (1 wire signal + 2 wire power) network
• wifi based nodes
• twisted pair connected ethernet devices

bridge between different types of network is organized on TCP/IP application server running currently on linux
etc. potentially allows to connect network segments regardless physicall location, only internet connection is required

why i'm doing this? mostly for fan but also to implement 2 principles:

• application layer to be independant from hardware and transport. message format is universal and is the same regardless platform and communication hardware. Addressing is also universal. Application should not take care about intermediate specific, this is handled by other components
• avoid a central unit. each device can communicate with each device. the only central component is application server. but is is very simple, robust and reliable. failover is supported

My example:

bridge from single wire (my w3p manchester based) to UART. will be used to bridge single wire network with Ethernet throuth ESP8266 or STM32 + Wiznet

second photo - development stand with w3p bus

esp8266 based thermostat for heating system