**Complete Design of 33×33 mm RS485 Smart Fan Regulator Daughter Board for ESPHome – ATtiny1614 \+ 24V Relays**

Project Requirement

I need an experienced electronics engineer to design a complete schematic and PCB from scratch in KiCad for a compact smart ceiling-fan regulator.

The board will be used as a daughter/actuator board for an ESPHome-based home automation system.

A separate ESP32/ESPHome controller will act as the main controller. This daughter board will communicate with it over RS485 and locally control a conventional 230 VAC ceiling fan using relay-switched capacitors.

Target PCB size:

33 mm × 33 mm, 2-layer

The designer is responsible for schematic design, component verification, PCB layout/routing, firmware, ERC/DRC and manufacturing files.

Main Hardware

Preferred architecture:

* ATtiny1614 local microcontroller
* UPDI programming interface
* 24 V DC input
* 24 V to 3.3 V buck converter, preferably LMR51610 or verified equivalent
* SP3485 or equivalent 3.3 V RS485 transceiver
* RS485 protection and selectable 120 ohm termination
* 4 × Panasonic APAN3124, 24 V relays
* Individual MOSFET relay drivers and flyback diodes
* External Norisys 8-speed rotary knob input
* 230 VAC fan input/output
* Fuse and required mains protection

The daughter-board connection to the ESPHome/master controller should be:

* +24 V
* GND
* RS485 A
* RS485 B

The physical knob must continue to operate the fan even if RS485 or ESPHome is offline.

Fan Capacitor Network

Use three switched fan capacitors:

* K1 = 1.8 µF
* K2 = 2.8 µF
* K3 = 3.8 µF
* K4 = direct/full-speed bypass

Preferred existing capacitor types:

* C11 = D185J, 1.8 µF, 250 VAC
* C12 = D285J, 2.8 µF, 250 VAC
* C13 = D385J, 3.8 µF, 250 VAC

Each K1-K3 branch should approximately follow:

Relay contact → 10 ohm / 1 W fusible resistor → AC capacitor → FAN_OUT

Each capacitor branch should also use approximately a 330 kΩ discharge/bleeder resistor.

The capacitor parts must be verified as suitable for continuous 230 VAC ceiling-fan/motor-run use.

Required Speed Combinations

K4 is the direct full-speed bypass.

K4 must never operate simultaneously with K1, K2 or K3.

Relay transitions should use break-before-make operation:

All relays OFF → approximately 200 ms delay → required new relay combination ON

Norisys 8-Speed Rotary Knob

The original Norisys mechanical regulator selector will be reused only as a low-voltage dry-contact encoder.

Available contacts:

* P1
* P2
* P3
* D
* COM

The original mains-voltage capacitor/resistor circuitry will not remain connected to the knob.

Measured Knob Combinations

Important:

At physical Speed 8, the selector produces:

P1 + D

The firmware must interpret the D input as the direct/full-speed request and command:

* K1 OFF
* K2 OFF
* K3 OFF
* K4 ON

Suggested input conditioning for P1, P2, P3 and D:

* approximately 1 kΩ series resistor
* approximately 10 kΩ pull-up
* approximately 10 nF filter capacitor

The knob must carry low voltage only and never 230 VAC.

ESPHome / RS485 Operation

The ATtiny1614 daughter board should communicate with a separate ESP32 running ESPHome.

The RS485 protocol should support at minimum:

* Fan OFF
* Speed 1 to 8 command
* Read current commanded speed
* Read actual relay state
* Read physical Norisys knob position
* Communication/status indication if practical

The RS485 protocol must be simple, reliable and fully documented so that it can be integrated into ESPHome.

The freelancer should provide a working ESPHome-side example/configuration or custom component code for communication with the daughter board.

The designer should also define the interaction between:

Physical Norisys knob and ESPHome/RS485 commands.

Local knob operation must remain functional if the ESPHome controller or RS485 bus is unavailable.

On MCU reset, invalid selector input or abnormal condition, the board should enter a safe relay state.

PCB Requirements

* Target size: 33 × 33 mm
* 2-layer KiCad PCB
* Proper 230 VAC and SELV segregation
* Relay coil side toward low-voltage circuitry
* Relay contact side toward mains circuitry
* No unnecessary GND, 3.3 V or signal copper in the mains section
* Proper creepage and clearance for mains
* Appropriate mains track widths
* Correct switching-regulator layout
* Short SW current loop
* Correct placement of input, output and bootstrap capacitors
* Clean RS485 routing
* Accessible UPDI programming pads
* SMD parts mainly on F.Cu for JLCPCB assembly
* Through-hole relays, AC capacitors and connectors may be hand soldered

If 33 × 33 mm cannot be achieved safely, the designer must discuss the required increase in PCB size before changing it.

Project Scope

The project must be designed from scratch, including:

1. Complete circuit architecture
2. Component selection and verification
3. Complete KiCad schematic
4. ERC
5. PCB placement
6. PCB routing
7. Mains/SELV safety review
8. DRC
9. ATtiny1614 firmware
10. RS485 protocol
11. ESPHome integration example
12. Manufacturing package

Any old schematic or PCB supplied by me should be treated only as a reference for functionality, not as the final design.

Final Deliverables

Provide:

* Complete KiCad project
* .kicad_pro
* .kicad_sch
* .kicad_pcb
* All custom symbols and footprints
* BOM with exact manufacturer part numbers
* ERC report
* DRC report
* Gerbers
* NC drill files
* JLCPCB-compatible BOM
* JLCPCB CPL/Pick-and-Place file
* Schematic PDF
* Assembly drawings
* ATtiny1614 firmware/source code
* Documented RS485 protocol
* ESPHome integration example
* Prototype bring-up and testing procedure

The final project must open on another computer without missing libraries or footprints.

Please apply only if you have practical experience with:

* 230 VAC PCB design
* Relay/motor control
* KiCad
* Switching regulators
* Microcontrollers
* RS485
* JLCPCB assembly

Please share examples of previous mains or mixed-voltage PCB designs and quote a fixed price for the complete project.