Custom Wireless Battery-Powered Radio Design

I am looking for an expert in electronics design to bring a unique radio concept to life. The primary purpose of this device is to meet customer demands, so creativity and understanding of consumer needs are essential.

Key project details:
- Design will involve creating detailed schematics and PCB layouts.
- The radio needs to be able to connect wirelessly.
- It should be battery powered, necessitating efficient power management for longevity.
- High durability is a key requirement, so the design must consider the ability to withstand potential rough handling or environmental challenges.

The ideal freelancer for this project will be skilled in electronics design, with experience in designing for consumer products. Understanding of wireless technology and power management will be key, as will the ability to create designs that can be manufactured at scale. Most importantly, I need someone who can deliver a high-quality, durable product that meets the needs of the end customer - myself.



*********** IMPORTANT NOTES *********************************
The whole project must be design in EasyEDA

The freelancer have to provide the project with schematics and PCB

******************************************************************

I need to build two devices,
on remote controler with 8 buttons able to control from one up to 8 receivers.

I'm going to use LORA protocol in low frequencies so i can achive long range control.
The Chip I'm thinking is SX1276/78 chips / RFM95W/96W/98W modules (direct implementation of the SX127x)

**************************************************************************************************
The first step is the transmiter.
--------------------------------------------------------------------------------------------------
You could keep the main MCU and LoRa chip in a deep sleep mode OR powered off.

Complete power-off is necessary for battery life, you might need to implement a small capacitor
to provide power during the brief startup sequence.

For the user experience, you should add an LED that blinks immediately when the button is pressed
to indicate transmission, even if the actual LoRa transmission takes a few more milliseconds to complete.

Circuit Design

The circuit uses an ATmega328P microcontroller connected to an RFM95W/SX1276 LoRa module.
The power management system is crucial for battery life - it keeps the LoRa module completely powered off when not in use,
while the microcontroller stays powered off and powered on when a button is pressed.

Key Features
Instant Response: When a button is pressed, the microcontroller power on instantly.
Power Efficiency: A MOSFET power control only enables the power-hungry LoRa module when actually transmitting.

Power options
2× AAA batteries (or 3)
9V battery


Parts
## Microcontroller
U1: ATmega328P-AU (TQFP-32 package)

## RF Module
U2: RFM95W or compatible SX1276 LoRa module

## Crystal
XTAL1: 8MHz crystal (HC-49S package)

## Transistors
Q1: BSS138 N-Channel MOSFET (SOT-23 package)
- VDS: 50V
- RDS(on): 3.5Ω
- Logic-level gate

## Capacitors
C1: 0.1μF ceramic capacitor (0603 or 0805 package)
C2: 10μF electrolytic capacitor (SMD size B or C, 4V or higher)
C3, C4: 22pF ceramic capacitors (0603 package)


## Switches
SW1-SW8: It is a keypad 4x2 common ground.

## Antenna
U.FL connector for external antenna
## Connectors
- Programming header: 2×3 pin header (2.54mm pitch) for ICSP
- Optional: Battery test points

*********************************************************************************************
Receiver Design Considerations
----------------------------------------------------------------------------------------------
Power fron 12-14V battery or transformer (molex connector should be used)
RFM95W/RFM98W LoRa Module - Same as in your transmitter for frequency compatibility
ATmega328P-AU - Same microcontroller as transmitter for code compatibility
8MHz Crystal - For microcontroller clock
22pF Capacitors (2) - Crystal load capacitors
0.1μF Capacitors (2-3) - Decoupling capacitors

Relay Components:
30V 10A+ Relay - Options include:
Omron G5LE-1-E - 10A/250VAC, 10A/30VDC
SRD-05VDC-SL-C - Common 5V relay rated for 10A/30VDC
Panasonic JW2SN-DC5V - Industrial grade 10A relay

2N2222 or 2N3904 Transistor - Relay driver

1N4148 Diode - Flyback protection diode for relay

1kΩ Resistor - Base resistor for transistor

Screw Terminal Blocks - For relay output connections (30V/10A rated)

LED and 1kΩ Resistor - Status indicator

10kΩ Resistor - Pull-up for reset line

2x3 Header - ICSP programming header

PCB Antenna or SMA Connector - For LoRa reception
*****
Automotive Power Supply (11.5-14V DC)
For receivers powered from a car/vehicle battery:
Components Needed:
Voltage Regulator Options:

LM2596 Buck Converter Module (Better efficiency)
Adjustable output, set to 5V
Can handle wide input range (7-35V)
Higher efficiency than linear regulators (85% vs 50%)
****
Protection Components:

TVS (Transient Voltage Suppressor) diode rated for automotive use
Polyfuse (resettable fuse) rated 500mA-1A
1N5408 diode for reverse polarity protection
****
Noise Filtering:
LC filter for automotive electrical noise
100μF capacitor for input buffering
Ferrite bead on input

****
The automotive option needs to handle voltage spikes, load dumps, and electrical noise common in vehicle electrical systems.
Recommendation
For both options, I recommend adding:

A power indicator LED with current-limiting resistor
A dedicated ground plane for the power circuit
TVS diodes on relay contacts to suppress arc-induced voltage spikes

For the automotive application, choose components with wider temperature ranges (-40°C to +85°C)
to handle the harsh environment.