Hardware Specifications - WateringSystem v2.3 (Hardware-Managed LDO Architecture) This document provides complete hardware specifications for the hardware-managed WateringSystem designed for cost-effective greenhouse automation. The system uses LDO voltage converters with common ground and optical signal isolation - optimized for always-on 12V applications with hardware-only power management.
1. Microcontroller - ESP32-WROOM-32E
Specification
Value
CPU
Dual-core Xtensa LX6 microprocessor
Clock Speed
Up to 240 MHz
Flash Memory
4 MB
RAM
520 KB SRAM
Wireless
Wi-Fi 802.11 b/g/n (2.4 GHz) + Bluetooth 4.2
GPIO Pins
34 programmable GPIO pins
ADC
12-bit SAR ADC, up to 18 channels
Power Supply
3.3V
Operating Temperature
-40°C to +85°C
2. Environmental Sensor - BME280
Specification
Value
Interface
I2C (Address: 0x76 or 0x77)
Temperature Range
-40°C to +85°C
Temperature Accuracy
±0.5°C
Humidity Range
0% to 100% RH
Humidity Accuracy
±3% RH
Pressure Range
300 to 1100 hPa
Pressure Accuracy
±1 hPa
Supply Voltage
1.71V to 3.6V
Current Consumption
3.6 μA at 1 Hz
3. Soil Sensor - RS485 Modbus Soil Sensor
Specification
Value
Interface
RS485 Modbus RTU
Baud Rate
9600 bps (default)
Data Format
8N1 (8 data bits, no parity, 1 stop bit)
Device Address
Configurable (default: 0x01)
Moisture Range
0% to 100%
Temperature Range
-40°C to +80°C
pH Range
3 to 9 pH
EC Range
0 to 20000 μS/cm
NPK Range
Nitrogen: 0-1999 mg/kg, Phosphorus: 0-1999 mg/kg, Potassium: 0-1999 mg/kg
Supply Voltage
5V DC (LDO-managed always-on)
Current Consumption
< 50 mA (typical)
Cable Length
Up to 200 meters (adequate for greenhouse)
Modbus Register Map
Register
Description
Unit
Format
0x0000
Soil Moisture
%
Unsigned 16-bit
0x0001
Soil Temperature
0.1°C
Signed 16-bit
0x0002
Soil pH
0.1 pH
Unsigned 16-bit
0x0003
Soil EC
μS/cm
Unsigned 16-bit
0x0004
Nitrogen
mg/kg
Unsigned 16-bit
0x0005
Phosphorus
mg/kg
Unsigned 16-bit
0x0006
Potassium
mg/kg
Unsigned 16-bit
0x0007
Soil Humidity
%
Unsigned 16-bit
4. RS485 Interface - MIKROE-4156 with Optical Isolation MikroElektronika RS485 5 Click (MIKROE-4156)
Specification
Value
Interface
UART to RS485
Transceiver IC
ADM3485ARZ (Analog Devices)
Signal Rate
Up to 12 Mbps
Operating Voltage
5V (LDO-managed)
ESD Protection
±15kV on bus pins
Bus Load
Supports up to 32 transceivers
Interface
mikroBUS™ connector
Dimensions
25.4 x 28.58 mm
TXS0108E Level Shifter (Voltage Translation)
Specification
Value
Type
8-bit bidirectional voltage translator
Input Voltage (A-side)
1.2V to 3.6V (ESP32: 3.3V)
Input Voltage (B-side)
1.65V to 5.5V (RS485: 5.0V)
Data Rate
Up to 110 Mbps
Propagation Delay
10ns typical
Package
20-pin TSSOP
Operating Temperature
-40°C to +85°C
Channels Used
3 (TX, RX, DE/RE)
Verified Timing 50µs DE/RE switching delays (tested July 2025)
Communication Rate 9600 baud Modbus RTU verified functional
Specification
Value
Operating Voltage
12V DC
Current
0.5A - 1.5A (depending on pressure)
Flow Rate
1-3 liters per minute
Maximum Head
2-3 meters
Power Consumption
6-18W
Duty Cycle
30 minutes max continuous operation
Quantity
2 pieces (plant pump + reservoir pump)
6. Power Supply Components LiFePO4 Battery
Specification
Value
Voltage
12V nominal
Capacity
20Ah (240Wh)
Type
LiFePO4 (safe chemistry)
Operating Temperature
0°C to 45°C
Cycle Life
>2000 cycles
LDO Voltage Converters (Always-On Hardware Management)
Component
Input
Output
Current
Efficiency
Type
AMS1117-3.3 (ESP32 domain)
12V
3.3V
1A
>85%
LDO
AMS1117-5.0 (Field domain)
12V
5V
1A
>85%
LDO
Key Features:
Hardware-only power management (no software control)
Always-on operation with low dropout voltage
Common ground design eliminates ground loop issues
Thermal protection and current limiting
Stable output voltage regulation
Pin Assignments - Hardware-Managed LDO Architecture with TXS0108E | GPIO | Connected To | Description |
GPIO
Connected To
Description
GPIO 21
I2C SDA
BME280 Data Line
GPIO 22
I2C SCL
BME280 Clock Line
GPIO 17
TX2
RS485 TX (via TXS0108E A1)
GPIO 16
RX2
RS485 RX (via TXS0108E A2)
GPIO 25
DE/RE
RS485 Direction Control (via TXS0108E A3)
GPIO 26
Plant Pump Control
Main Water Pump MOSFET Gate
GPIO 27
Reservoir Pump Control
Reservoir Filling Pump MOSFET Gate
GPIO 32
Reservoir Low Level
Water Reservoir Low Level Sensor
GPIO 33
Reservoir High Level
Water Reservoir High Level Sensor
GPIO 2
Status LED
System Status Indicator
GPIO 5
Button 1
Manual Mode Button
GPIO 18
Button 2
Configuration Button
Pin Configuration Updates (July 2025):
CRITICAL FIX: GPIO 16/17 pin assignments corrected for proper RS485 communicationPrevious configuration had TX/RX pins swapped causing communication failures
Now matches verified working test configuration: TX=GPIO17, RX=GPIO16
TXS0108E timing delays optimized to 50µs for reliable level shifting
All RS485 communication now fully functional with Modbus soil sensors
Power Architecture - Hardware-Managed LDO System
Domain
Voltage
Ground
Control
Components
ESP32 3.3V
GND_COMMON
LDO Always-On
ESP32, BME280, Control logic
FIELD 5V
GND_COMMON
LDO Always-On
RS485 module, Soil sensor
12V LiFePO4 Battery
├── LDO 3.3V → ESP32 Domain (control, WiFi, sensors)
└── LDO 5V → Field Domain (RS485 + soil sensor)
└── Common Ground (GND_COMMON) - No isolation required
Hardware-Only Management Strategy
Always-On Design: Both LDO converters provide continuous regulated powerNo Software Control: Power domains managed entirely by hardwareCommon Ground: Single ground plane simplifies design and eliminates ground loopsLevel Shifting: TXS0108E provides fast bidirectional voltage translation for RS485 signalsSafety Level: Practical for enclosed 12V systems in ASA IP65 box
┌─────────────────┐
│ │ │ ESP32 │
│ (3.3V LDO) │
└─┬───┬───┬───┬───┘
│ │ │ │
│ │ │ │
┌─────────────┐ │ │ │ │ ┌────────────┐
│ │◄──SDA─────┘ │ │ │ │ TXS0108E │
│ BME280 │ │ │ │ │(3.3V↔5V) │
│ │◄──SCL─────────┘ │ └───TX────►│ A1 B1 ──┼──►
└─────────────┘ │ │ A2 B2 ──┼──◄─RX
└───DE/RE─────►│ A3 B3 ──┼──►
│ OE←VCC │
└──────┬─────┘
┌─────────────┐ │
│ Reservoir │ ┌─────▼─────┐
│ Low Level │◄──GPIO32───┐ │ │
│ Sensor │ │ │ MIKROE │
└─────────────┘ │ │ 4156 │
│ │ (5V LDO │
┌─────────────┐ │ │Always-On) │
│ Reservoir │ │ └─────┬─────┘
│ High Level │◄──GPIO33───┤ │
│ Sensor │ │ ┌────▼─────┐
└─────────────┘ │ │ │
│ │ RS485 │
┌─────────────┐ │ │ Soil │
│ 12V DC │ │ │ Sensor │
│ Battery ├──12V───────┼───────────────┬────────┤ (5V pow) │
│ (LiFePO4) │ │ │ └──────────┘
└──────┬──────┘ │ │
│ │ │
│ │ │
┌──────▼──────┐ │ ┌────▼────┐
│ 3.3V │ │ │ │
│Buck Convert ├──3.3V──────┼──────────┤ Plant │
│ LM2596 │ │ │ Pump │
└─────────────┘ │ │ Control │
│ │ │
┌──────▼──────┐ │ └────┬────┘
│ 5V │ │ │
│Buck Convert ├──5V────────┼──────────┌────▼────┐
│ LM2596 │ │ │ │
└─────────────┘ │ │Reservoir│
│ │ Pump │
┌─────────────┐ │ │ Control │
│ User │ │ │ │
│ Interface │◄───GPIO5/18┤ └────┬────┘
│ (Buttons) │ │ │
└─────────────┘ │ │
│ ┌────▼────┐
┌─────────────┐ │ │ │
│ Status │◄───GPIO2───┘ │ Water │
│ LED │ │ Pumps │
│ │ │ (12V) │
└─────────────┘ └─────────┘
Bill of Materials (BOM) - Simplified v2.2
Item
Description
Quantity
Unit Price (SEK)
Total (SEK)
Notes
1
ESP32-WROOM-32E Module
1
120
120
Main microcontroller
2
BME280 Sensor Module
1
50
50
Environmental sensing
3
RS485 Soil Sensor (NPK)
1
600
600
Soil parameters measurement
4
MIKROE-4156 RS485 5 Click
1
200
200
RS485 transceiver
5
TXS0108E Level Shifter
1
8
8
3.3V↔5V voltage translation
6
12V DC Water Pump
2
150
300
Plant + reservoir pumps
7
IRLZ44N N-Channel MOSFET
2
10
20
Pump control
8
1N4007 Diode
2
2
4
Flyback protection
9
Water Level Sensor
2
25
50
Reservoir level detection
10
LiFePO4 12V 20Ah Battery
1
800
800
Main power source
11
AMS1117-3.3 LDO Regulator
1
25
25
3.3V always-on power
12
AMS1117-5.0 LDO Regulator
1
25
25
5V always-on power
13
Capacitors (various)
15
3
45
Power filtering
14
Resistors (various)
20
1
20
Current limiting, pull-up/down
15
Status LEDs
3
5
15
Status indication
16
Push Buttons
2
10
20
User interface
17
Terminal Blocks
8
8
64
Connections
18
PCB (2-layer)
1
150
150
Custom designed
19
ASA Enclosure IP65
1
200
200
Weather protection
20
Water Tubing (silicone)
3m
20
60
Food-grade
21
Shielded Twisted Pair
5m
15
75
RS485 connection
22
Water Reservoir
1
100
100
Storage container
23
Misc (screws, wire, etc.)
1
100
100
Assembly materials
TOTAL 2998 SEK
Component
Voltage
Current (Peak)
Power (W)
ESP32
3.3V
250mA
0.8
BME280
3.3V
1mA
0.003
TXS0108E
3.3V/5V
2mA
0.007
RS485 Module
5V
100mA
0.5
Soil Sensor
5V
50mA
0.25
Water Pump (active)
12V
1.5A
18
Total (pump off) 1.56W
Total (pump on) 19.56W
Battery Life Calculation:
Normal operation: 240Wh ÷ 1.56W = ~154 hours (6.4 days)
With 30min pumping/day: ~140 hours (5.8 days)
Fast level shifting via TXS0108E (110 Mbps capability)Voltage translation between ESP32 (3.3V) and field domains (5V)Bidirectional communication with minimal propagation delay (10ns)
Always-on LDO design provides continuous regulated powerNo software power control eliminates complexity and failure pointsCommon ground design prevents ground loop issues
IP65 enclosure for outdoor installationsOperating temperature: 0°C to 50°CStorage temperature: -10°C to 60°C
Mount in ASA IP65 enclosure
Position away from direct sunlight
Ensure adequate ventilation
Waterproof all external connections
Use twisted pair cable for A and B signals
Maximum cable length: 200m for greenhouse applications
No termination resistors needed for short runs (<50m)
LDO regulators provide stable voltage regulation
LiFePO4 battery safe for indoor/greenhouse use
Always-on design eliminates startup delays
Solar charging capability (MC4 connectors planned)
Solar charging controller (10W panel)
Additional soil sensors (up to 8 on RS485 bus)
Weather station integration
LoRa communication for remote monitoring
Spare GPIO pins for expansion
Extra power capacity for additional sensors
Modular PCB design for easy modifications
This simplified 2-domain architecture provides cost-effective greenhouse automation while maintaining essential safety features through optical isolation. The design prioritizes practical implementation over complex isolation schemes.