Electrical Engineering microcontroller circuit design

I am looking for an electrical engineer to design a complete electronic control system for a portable device powered by either an external power supply or a 20V DeWalt rechargeable battery. System Requirements Power Sources * Operate from a 20V DC power supply when available. * Operate from a 20V DeWalt battery when external power is unavailable. * Automatically switch between power sources without user intervention. * Prioritize external power when connected. * No battery charging circuitry is required. Loads to be Controlled 1. One 12V DC fan rated at approximately 80 watts. * Operate at 50% duty cycle using PWM control. 2. Four UV LEDs. * Include proper driver circuitry and current regulation. 3. Two piezo transducers. * Operate at 44 kHz. * Target output of approximately 80 dB. * Include appropriate oscillator and driver circuitry. Control System * Use a microcontroller-based design. * Single Start button preferred. * Run all loads for 1 hour. * Automatically shut down after 1 hour. * Monitor battery voltage and shut down safely if battery voltage becomes too low. * Include status LEDs if practical. * Allow for future firmware modifications and feature additions. Battery Requirements * System will use a standard 20V DeWalt battery pack. * No charging functionality is required. * Engineer should recommend an appropriate low-voltage cutoff to protect the battery. * Engineer should estimate expected runtime based on typical DeWalt battery capacities. Deliverables * Complete schematic. * Bill of Materials (BOM). * Wiring diagram. * PCB layout recommendations. * Microcontroller firmware source code. * Programming instructions. * Power consumption calculations. * Runtime estimates using common DeWalt battery capacities. I will provide technical specs and components later. Thank you JP