Home automation PCB

The story behind this, can be found on my blog

It will hold a series of breakout boards for I2C IO expanders, 1Wire drivers, ADCs. All are controlled with a Raspberry Pi 3B+.

The 220V actuators are controlled by a board with 16 mechanical relays. The board is in turn controlled by PCF8575 chip that takes I2C commands and controls 16 I/O pins. Board is active on low (optocouplers), PCF8575 can sink more current (than it could source). Perfect match.

The 16 relay board is separate, from this PCB, only a pin header connection is made.

The temperature sensors are DS18B20 that work on 1 wire protocol. These are already mounted with Ethernet cables terminated with RJ45. The sensors are read/driven by 4 ds2482s-100 chips (RJ45 terminals and ds2482s-100 are on this PCB). The RJ jacks must be galvanic!

There are some other relays/contactors/voltages that needs monitoring, all done by 2 ADS1115 16-Bit ADC, present on board.

The chips are already sourced and live on their breakout boards. The PCB is mainly THT because of sourcing issues (eg can't find ds2482s-100 anywhere, will reuse existing breakouts). Only SMD are the 3.5 audio jacks (for ADC) again because no THT could be sourced atm.

The Raspberry Pi connector is only 20 pin wide because only the first few are used (5V, 3.3, SDA, SCL, GND)

There is a spurious bug, all relays are ON when the 16 relay board is powered but the Raspberry (that powers the rest of the circuits) is OFF. So, a solid state relay is used to cut power to the relay board when the RaPi is shutted down.

With the exception of ADCs, the schema and design choices follow the existing (4 years old) system.

This repo is mainly for reviewing purposes.

The story behind this PCB is on www.visoft.ro

A list with the devices

Relay board that will be driven:

https://www.sainsmart.com/products/16-channel-12v-relay-module

16 channel IO expander that will drive the board:

https://www.artekit.eu/products/breakout-boards/io/ak-pcf8575-i2c-16-bit-io-expander-breakout/

I2C level shifter (3.3 to 5V)

https://www.pololu.com/product/2595

I2C to differential signals:

https://www.sparkfun.com/products/retired/14589

1Wire drivers:

https://www.artekit.eu/products/breakout-boards/io/ak-ds2482s-100/

ADC:

https://www.adafruit.com/product/1085

Some ADC "watch" only for presence/absence of 5V power but some are listenting to CT sensors. Quasi similar model: https://www.seeedstudio.com/Non-invasive-AC-Current-Sensor-30A-ma-p-519.html

Solid state relay:

https://www.tme.eu/en/details/dmo063/dc-solid-state-relays/crydom/

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