Brewing all-grain beer requires precise water temperature management, but the traditional manual approach demands constant monitoring over several hours. I was spending entire afternoons babysitting my hot liquor tank, checking water levels, and ensuring the heating element didn't fire without adequate water coverage.
The Problem
Critical Pain Points
- Manual Water Management: RO water filling required hours of periodic checking to prevent overflow or dry heating element activation
- Safety Risks: Heating elements can be damaged or create fire hazards if activated without sufficient water coverage
- Time Inefficiency: Brewing preparation consumed 3-4 hours of active monitoring before actual brewing could begin
- Temperature Inconsistency: Manual temperature control led to overshooting target temps, extending total prep time
- Scheduling Constraints: Had to be physically present throughout the entire heating and filling process
The Vision: I envisioned a system that could autonomously manage water filling, heating, and safety monitoring while providing delayed start functionality. This would transform brewing from an all-day commitment to a scheduled, predictable process where I could start prep remotely and arrive to perfectly heated water.
Design Process
This project required me to master multiple disciplines simultaneously - from water sensor physics to safety-critical software design. I approached it as both a technical challenge and a UX problem, prioritizing safety and reliability above all else.
Research & Requirements
Understanding Safety-Critical Design
Researched industrial safety systems for water heating applications. Studied failure modes of heating elements and developed comprehensive safety requirements. Key insight: any single sensor failure must default to safe operation (heating disabled).
Hardware Architecture
Designing the Physical System
Designed custom water sensors using stainless steel probes and proper debouncing circuits. Integrated Raspberry Pi with MOSFET drivers for solenoid control and SSR for heating element management. Created isolation layers between low-voltage control and high-power circuits.
Interface Design
Custom Nextion HMI Development
Designed a brewing-specific interface optimized for wet environments and quick status assessment. Created temperature profiles (Mash, Strike, Off), automated countdown timers, and comprehensive system status displays. Prioritized large touch targets and high-contrast visual feedback.
Software Architecture
Safety-First Code Design
Implemented multi-threaded architecture with separate controllers for heating, valve management, and sensor monitoring. Created robust error handling and sensor debouncing to prevent false triggers. Designed fail-safe defaults throughout the system.
Integration & Testing
Real-World Validation
Extensive testing with actual brewing scenarios, simulated sensor failures, and edge cases. Discovered issues with sensor interference, timing race conditions, and the need for more sophisticated debouncing algorithms under varying water conditions.
Refinement & Deployment
Production-Ready System
Implemented advanced sensor fusion, improved safety interlocks, and refined the user interface based on real brewing sessions. Added WiFi monitoring, comprehensive logging, and remote status capabilities for true hands-off operation.
The Solution
The HLT HUD emerged as a comprehensive automation system that handles every aspect of hot liquor tank preparation while maintaining the highest safety standards. The system transforms hours of manual monitoring into a simple "set and forget" experience.
Multi-Layer Safety System
Redundant water sensors with hardware debouncing ensure heating elements never activate without adequate water coverage. Emergency shutoff protocols protect against all failure modes.
Delayed Start Automation
Program heating to begin hours in advance, automatically managing water filling and temperature ramping to have perfect brewing water ready when you arrive.
Precision Temperature Control
Smart temperature profiles (Mash: 154°F, Strike: 175°F) with PID control algorithms maintain precise temperatures without overshooting.
Custom HMI Interface
Purpose-built Nextion display with brewing-optimized workflows, real-time system status, and intuitive controls designed for brewery environments.
Dry Fire Protection
Dual water sensors prevent heating element activation without adequate water coverage
Temperature Monitoring
Continuous temperature monitoring with emergency shutoff at critical thresholds
Valve Interlocks
Automated valve control prevents tank overflow while ensuring adequate heating element coverage
Remote Monitoring
WiFi connectivity enables remote status checking and emergency shutdown capabilities
System Architecture
Raspberry Pi 4
11.9" Nextion HMI
DS18B20 Temp Sensor
Water Level Sensors
SSR Heating Control
Solenoid Valve Control
Hall Effect Flow Sensor
WiFi Monitoring
# Safety-critical sensor monitoring with debouncing
def update_sensors(self, current_time, current_temp):
# Heating element safety with debounced readings
element_sensor_state = GPIO.input(PinConfig.LIQUID_SENSOR)
element_safe = element_sensor_state == GPIO.HIGH
# Multi-point sensor validation for tank filling
tank_sensor_readings = []
for reading in range(5):
tank_sensor_readings.append(GPIO.input(PinConfig.TOP_LIQUID_SENSOR))
time.sleep(0.01)
# Majority vote for state changes (fault tolerance)
tank_full = sum(reading == GPIO.HIGH for reading in tank_sensor_readings) >= 3
# Safety interlock: disable heating if no water detected
if not element_safe:
self.heating_system.emergency_shutoff()
self.nextion.update_element_status(False)
# Automated valve control with safety checks
if tank_full and self.valve_controller.is_intake_open():
self.valve_controller.close_intake_valve()
self.nextion.update_tank_status(False)
Challenges & Learning
Building a safety-critical system as a solo developer meant learning industrial engineering principles while simultaneously designing UX and writing embedded code. Every challenge became an opportunity to deepen my understanding of systems thinking.
🔧 Sensor Interference & Reliability
Challenge: Water sensors triggered false positives due to electrical interference from heating elements,
causing erratic valve behavior.
Solution: Implemented sophisticated debouncing algorithms, majority voting across multiple readings,
and proper electrical isolation. Added state confirmation requiring consistent readings over time.
⚡ Real-Time Safety Requirements
Challenge: System must respond to dangerous conditions (dry heating element) within milliseconds
while maintaining responsive UI updates.
Solution: Designed multi-threaded architecture with priority-based task scheduling. Safety monitoring
runs on fastest update cycle, independent of UI rendering.
🎯 Complex State Management
Challenge: Managing interactions between delayed start timers, temperature profiles, valve states,
and safety interlocks created complex state dependencies.
Solution: Implemented state machine pattern with clear transitions and fail-safe defaults.
Each component maintains its own state with well-defined interfaces.
🖥️ Custom HMI Development
Challenge: No existing interfaces designed for brewing workflows - needed to create everything
from scratch while learning Nextion's proprietary development environment.
Solution: Studied industrial HMI design principles, created paper prototypes first, then iterated
through multiple interface versions based on actual brewing sessions.
Results & Impact
The HLT HUD has fundamentally transformed my brewing preparation workflow, eliminating hours of manual monitoring while significantly improving safety and consistency. The system has operated flawlessly through dozens of brewing sessions without a single safety incident.
89%
Reduction in Active Monitoring Time
±1°F
Temperature Control Accuracy
100%
Safety Incident Prevention
∞
Maximum Delayed Start Window
Key Achievements
- Autonomous Operation: Complete hands-off water filling and heating from empty tank to target temperature
- Zero Safety Incidents: Redundant safety systems have prevented dry firing and overflow situations across 50+ brewing sessions
- Scheduling Flexibility: Delayed start functionality allows brewing preparation to begin hours before arrival
- Precision Control: Temperature profiles maintain exact mash and strike temperatures without overshooting
- System Reliability: Robust sensor debouncing and fault tolerance handle real-world brewery conditions
User Experience Transformation
What was once a 4-hour commitment requiring constant attention has become a simple setup process: select temperature profile, set delayed start time, and walk away. The system handles everything autonomously, sending status updates via WiFi and ensuring perfect brewing conditions upon return.
Reflection & Next Steps
The HLT HUD project pushed me to think like a systems engineer, safety engineer, UX designer, and embedded programmer simultaneously. This holistic approach to problem-solving has fundamentally changed how I approach complex challenges across all my work.
What I Learned
- Safety-First Design: In critical systems, safety requirements must drive architectural decisions from day one
- Hardware-Software Integration: Understanding physical constraints makes you a better software designer
- State Machine Thinking: Complex systems require formal state management to prevent dangerous edge cases
- Sensor Fusion: Single points of failure are unacceptable - redundancy and validation are essential
- User Context: Brewery environments demand interfaces optimized for wet hands and quick status assessment
Technical Evolution
This project taught me to think beyond traditional UX boundaries. The most elegant interface means nothing if the underlying system isn't reliable, safe, and fault-tolerant. True user experience encompasses the entire system - from sensor reliability to error recovery to emergency shutdown procedures.
Future Enhancements
- Predictive Analytics: Machine learning to optimize heating curves based on ambient conditions
- Recipe Integration: Direct connection with brewing software for automated water preparation
- Advanced Monitoring: Additional sensors for water quality, pH, and mineral content
- Energy Optimization: Smart scheduling based on time-of-use electricity rates
- Modular Expansion: Framework for adding additional brewing automation components
Design Philosophy
The HLT HUD embodies my belief that automation should eliminate tedium without removing control. Users can intervene at any point, but the system provides intelligent defaults and handles the routine tasks that don't require human judgment. Safety is never compromised for convenience, and transparency in automated decisions builds trust and understanding.