Great project idea! Let’s firm up the requirements so the schematic and PCB end up exactly how you need them. A few quick questions will help lock-in the architecture:
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Power strategy
- Do you want to keep everything fed from the 12 V adapter plus a small buck converter module (recommended for efficiency), or is the LM7805 linear regulator acceptable despite the heat it will dissipate?
- Any need for a 3.3 V rail (e.g. future I²C sensors)?
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Form-factor and mounting
- Approximate PCB size or shape target? (e.g. fit inside a small box on the coop wall, mount holes aligning to Arduino Nano headers, etc.)
- Do you want the Nano as an on-board module (soldered headers) or as a pluggable daughterboard so you can swap it out?
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Environmental protection
- The coop atmosphere can be humid and corrosive (ammonia). Will the board live in a sealed box with only sensor cables and fan wires coming out, or is conformal coating / other protection needed?
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Connectors and wiring
- For sensors and the fan, do you have a preferred connector type (Dupont, JST-XH, screw terminals) or should we pick low-cost JSTs?
- Will the I²C LCD stay on the same PCB or sit on panel wiring several centimeters away?
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User feedback & controls
- Besides the 20 x 4 LCD and buzzers, do you need buttons or status LEDs on the PCB?
- Any desire for future expansion headers (extra GPIO, UART for logging, etc.)?
Let me know your answers and I’ll suggest the detailed block diagram, parts list (including any little odds-and-ends such as gate resistors, pull-downs, and proper decoupling), and the next schematic steps.