2 layers160 × 100 mm
Test Board
Alfaa123/Arduino-Thermostat
This is a project to create a Arduino powered home thermostat. Version 1 PCB schematic and design is complete.
41 parts2
2 layers79.4 × 47.2 mm
Adafruit 2.9in eInk FeatherWing
Alfaa123/Arduino-Thermostat2This is a project to create a Arduino powered home thermostat. Version 1 PCB schematic and design is complete.
- Size
- 79.4 × 47.2 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 59
- Nets
- 54
- Pads
- 208
- Tracks, vias
- 334, 48
- Pours
- 2
- Routed
- Yes
- KiCad
- KiCad 5 (file 20171130)
- Created
- 13 Aug 2021
- Updated
- 16 Jul 2022
Overview
Adafruit 2.9in eInk FeatherWing is an open-source printed circuit board by Alfaa123, from the Alfaa123/Arduino-Thermostat repository on GitHub. It is a 2-layer board of 79.4 × 47.2 mm with 59 parts on 54 nets, routed with 334 tracks and 48 vias.
It is built around the 23K256-I/SN, AXP803 and MBR0530, with the IRLML0100 among its other parts. Its parts include 12 capacitors, 5 resistors, 4 diodes, 4 switches and 2 ICs. It belongs with the home automation and IoT and lEDs and displays boards of this library.
Main components
4
23K256-I/SN
SOIC-8-40℃~+85℃ 2.7V~3.6V 256Kbit 4uA SPI SOIC-8 SRAM ROHSMicrochip TechnologySRAMAXP803
QFN-68-EP(8x8)QFN-68-EP(8x8) Power Management - Specialized ROHSX-Powers TechPower Management - Specialized
MBR0530
SOD-1231 Independent 30V 5.5A 500mA 550mV@500mA 80uA@30V SOD-123 Schottky Diodes ROHSJiangsu Changjing Electronics Technology (CJ)Schottky Diodes
IRLML0100
SOT-23SOT-23 MOSFETs ROHShongjiachengMOSFETs
README
README.mdArduino-Thermostat
This is a project to create a Arduino (or Arduino compatible) powered home thermostat. Version 2 PCB schematic and design is complete.
Electrical Design
Version 2 has been updated and upgraded to use many SMD components. The board has shrunk, extra protections added and lots of the lessons learned from V1 were implemented as changes to V2.
Power Section
This takes the 24v AC from the air handler transformer and rectifies it to create a high voltage DC bus. This is then smoothed and an LM2596 is used as a switching regulator to create a 3.3v supply.
Power for the feather is supplied via the 3.3v pin from the onboard voltage regulator.
The regulator can handle up to 3a of current and would be accurately described as "way overkill" for the power requirements of the low voltage section of this board. However, the LM2596 regulators are so simple and easy to effectively use (thanks TI!) that it was worth the extra cost to just have something "easy."
Because the circuitry in the air handler requires the relays to be switched on with the supplied 24v AC, it is routed down the board to supply the common terminal of the three main relays.
Relay Drive Section
In order to drive the relays, small logic level MOSFETS are utilized with the feather board outputs acting as gate drivers for the three MOSFETs. The current requirements for the selected relays are very low and can easily be sunk by the selected MOSFETs.
Inputs and Outputs
An Adafruit Feather HUZZAH ESP8266 will be used to run the thermostat. This was selected because it was cheap, easy to work with and included a WiFi stack (allowing for some internet connected thermostat features in the future). One limitation of the ESP8266 is the extremely limited IO compared to the Arduino Nano of the V1 design. This lead to lots of design challanges, including the use of the onboard ADC for ladder buttons to save IO.
The central feature of the V2 design is the inclusion of a 2.9 inch e-ink display instead of a standard LCD. This high resolution, low power display will be ideal for a thermostat as the display needs minimal updates during normal usage.
Physical Outline
The physical outline of the board was designed to mimic my current thermostat. No mounting holes are included in the V2 design due to the success of the board edge mount that was used on the V1 design.
Lessons Learned for V2
Arduino placement needs to be revised. Currently plugging in the USB cable is impossible without bending a cable and potentially damaging the Arduino. This is the biggest mistake.fixed on V2 design. USB connector points toward the board edge and is easy to accessScrew terminal placement needs to be revised. Currently with the massive spacing, it required me to trim a lot of the insulation off of the 5 conductor cable in order to spread the wires out far enough to reach.fixed on V2 design. Screw terminals were moved much closer together and should make wiring the thermostat much easierMore markings on the front of the PCB to show which screw terminal does what. Currently it requires me to open the schematic and board files to correctly wire the thermostat.fixed on V2 design. Board markings on the silkscreen should make wiring the thermostat much easier.More work should be done to minimize footprint. Currently, the thermostat is physically very large.fixed on V2 design. Board outline has shrunk to around 60% of the original size.A larger screen would be nice to fit more information. A dot matrix or OLED would be best.fixed on V2 design. e-ink display selected as high resolution and low power display.Smaller regulator section and relays would go a long way to making the board shrink.unchanged on V2 design. However, the capacitors were revised with shorter, higher quality parts, the regulator was changed to a surface mount version and the diode and inductor were swapped with physically smaller versions.
Programming
No V2 programming has been written yet.
Required Libraries
TBD once V2 programming is underway
Planned Future Development
- PID control or other method for better temperature control.
- Humidistat control mode
- Adjustable circ fan frequency
- Better menu system
- Filtering on the temperature sensor to prevent rapid cycling
- Cycling time limit to prevent compressor damage
Parts
59| Qty | Value | Footprint | References |
|---|---|---|---|
| 13 | TPTP15SQ | Adafruit 2.9in eInk FeatherWing:TP15SQ | BUSY1, TP1, TP2, TP3, TP4, TP5, TP6, TP7, TP8, TP9, TP11, TP12, TP13 |
| 4 | 100K | Adafruit 2.9in eInk FeatherWing:0603-NO | R1, R6, R7, R8 |
| 4 | 1uF/25V | Adafruit 2.9in eInk FeatherWing:0805-NO | C3, C4, C22, C23 |
| 4 | MOUNTINGHOLE2.5 | Adafruit 2.9in eInk FeatherWing:MOUNTINGHOLE_2.5_PLATED | U$3, U$4, U$5, U$6 |
| 4 | SOLDERJUMPER_CLOSED | Adafruit 2.9in eInk FeatherWing:SOLDERJUMPER_CLOSEDWIRE | SJ1, SJ2, SJ3, SJ4 |
| 4 | SWITCH_SPST_TACT_RA | Adafruit 2.9in eInk FeatherWing:SPST_TACTILE_RA | SW1, SW2, SW3, SW4 |
| 3 | FIDUCIAL_1MM | Adafruit 2.9in eInk FeatherWing:FIDUCIAL_1MM | FID1, FID2, FID3 |
| 3 | MBR0530 | Adafruit 2.9in eInk FeatherWing:SOD-123 | D1, D2, D3 |
| 2 | 1uF | Adafruit 2.9in eInk FeatherWing:0805-NO | C16, C24 |
| 2 | 1uF/10V | Adafruit 2.9in eInk FeatherWing:0805-NO | C2, C6 |
| 1 | Adafruit 2.9in eInk FeatherWing:THINKINK_1.25IN | U$8 | |
| 1 | Adafruit 2.9in eInk FeatherWing:ADAFRUIT_TEXT_20MM | U$17 | |
| 1 | Adafruit 2.9in eInk FeatherWing:PCBFEAT-REV-040 | U$9 | |
| 1 | .47ohm | Adafruit 2.9in eInk FeatherWing:0805_10MGAP | R4 |
| 1 | 10uF/10V+ | Adafruit 2.9in eInk FeatherWing:0805-NO | C15 |
| 1 | 10uF/25V | Adafruit 2.9in eInk FeatherWing:0805-NO | C5 |
| 1 | 10uH | Adafruit 2.9in eInk FeatherWing:INDUCTOR_4X4MM_NR401 | L1 |
| 1 | 10µF | Adafruit 2.9in eInk FeatherWing:0805-NO | C21 |
| 1 | 1N4148 | Adafruit 2.9in eInk FeatherWing:SOD-323F | D4 |
| 1 | 1uF | Adafruit 2.9in eInk FeatherWing:0805_10MGAP | C1 |
| 1 | 23K256-I/SN | Adafruit 2.9in eInk FeatherWing:SOIC8_150MIL | U4 |
| 1 | AXP803 | Adafruit 2.9in eInk FeatherWing:SOT23 | IC5 |
| 1 | EINK_24PIN_290IN | Adafruit 2.9in eInk FeatherWing:EINK_290IN | EINK1 |
| 1 | FEATHERWING_SMTDUALNOHOLES | Adafruit 2.9in eInk FeatherWing:FEATHERWING_SMT_NOHOLES | MS1 |
| 1 | IRLML0100 | Adafruit 2.9in eInk FeatherWing:SOT23-3 | Q5 |
| 1 | MICROSD | Adafruit 2.9in eInk FeatherWing:MICROSD | X1 |
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Questions
How big is the Adafruit 2.9in eInk FeatherWing PCB?
It measures 79.4 × 47.2 mm and has 2 copper layers, 1.6 mm thick.
What parts does the Adafruit 2.9in eInk FeatherWing use?
59 parts, built around the 23K256-I/SN, AXP803, MBR0530 and IRLML0100. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the Adafruit 2.9in eInk FeatherWing KiCad files?
From the Alfaa123/Arduino-Thermostat repository on GitHub, at the commit this page was made from: the board is Board/Adafruit Eink Display/Adafruit 2.9in eInk FeatherWing.kicad_pcb and its schematic Board/Test Board.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Adafruit 2.9in eInk FeatherWing design in my own project?
Its repository states no licence, so its author keeps all rights: ask Alfaa123 before reusing the design.