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Multi-Beverage Dispenser with Linux HMI and Cortex-M Control

Prototype of a coffee machine with hot water and chocolate dispensing, using a Linux HMI with HD display and a separate Arm Cortex-M MCU for machine control.

Advanced Project — This is advanced because it combines a Linux HMI, a real-time Cortex-M control domain, liquid sensing, motor/pump actuation, temperature control, and safety-critical thermal and fluid handling in one system.
Assumptions:
  • The Linux HMI is a separate compute module or SBC, not included in the provided parts list.
  • The machine uses electrically driven pumps/valves and at least one motorized mechanism for beverage dispensing or mixing.
  • Hot water and chocolate imply liquid handling, so flow and level sensing are needed for safe operation.
  • Prototype means bench-top integration is acceptable; industrial certifications, food-grade plumbing, and mains safety hardware are out of scope here.
  • Parts should be purchasable from Digi-Key or Mouser in the Netherlands when possible.

Bill of Materials

Microcontroller
Top Pick NUCLEO-H743ZI2 STMicroelectronics From our database
NUCLEO-H743ZI2 is the best fit here because it gives you a modern Cortex-M7 MCU for deterministic machine control without the bulk and cost of a Discovery kit, and it is a much better prototype starting point than the EV40E67A.
STM32H7B3I-DK STMicroelectronics From our database
Strong MCU-class control platform with an STM32H7 Cortex-M7, lots of performance for real-time pump/valve control, and an included display/touch for local testing. However, it is a Discovery kit, so it is larger and less prototype-friendly than a compact dev board.
EV40E67A Microchip Technology From our database
SAM9X60 ARM926EJ-S MPU board is useful if you want a Linux-capable control platform, but it is not the right choice for the dedicated MCU control role and is also an evaluation platform.
Flow Sensor
Top Pick 114991177 Seeed Technology Co., Ltd From our database
114991177 is the best pick because it is already in the database, has the right pulse-output behavior for beverage volume control, and is a straightforward fit for a prototype coffee/water dispenser.
Mouser $6.90 (80 in stock) Digikey
YF-S201 Generic / various AI suggestion - verify availability
Very common Hall-effect water flow sensor with pulse output, easy to source from major distributors and widely supported in hobby and prototype designs. Good for measuring water dispense volume in a coffee/hot-water path.
FS300A Omron AI suggestion - verify availability
Compact liquid flow sensor option with digital pulse output, useful if you want a more refined flow sensing approach than the very common hobby sensors. Good for closed-loop dispense control and fault detection.
Temperature Sensor
Top Pick HEL-705-T-0-12-00 Honeywell Sensing and Productivity Solutions From our database
HEL-705-T-0-12-00 is the best overall choice because a probe-style 100 ohm RTD is robust and accurate for controlling brew and hot-water temperature in a coffee machine prototype.
Mouser $85.69 (1,088 in stock) Digikey
HEL-705-U-1-12-00 Honeywell Sensing and Productivity Solutions From our database
1000 ohm platinum RTD with good accuracy and a rugged probe package, useful where you want stable temperature measurement and easier wiring than low-ohm RTDs. Good for hot-water and boiler monitoring.
PTS080501B100RP100 Vishay From our database
100 ohm thin-film RTD in 0805 package, suitable if you want a compact PCB-mounted temperature sensor near a heater or pipe. Good for a custom PCB, but less mechanically robust than a probe.
Liquid Level Sensor
Top Pick 13835 SparkFun Electronics From our database
13835 is the best prototype choice because it is simple, robust, and easy to wire for empty/full tank detection, which is often enough for a first coffee-machine build.
Mouser $0.66 (1,335 in stock) Digikey
MTCH9010-E/REB Microchip Technology From our database
Dedicated capacitive liquid level interface is well suited to detecting liquid presence through a tank wall, which is attractive for coffee, water, or chocolate reservoirs. It can reduce mechanical wear compared with float switches.
MPRLS0025PA00001AB Honeywell From our database
Pressure sensor breakout can be used for tank or line pressure monitoring, which helps detect pump faults or blocked lines. It is not a direct level sensor, but it can complement level detection in a liquid system.
Actuator
Top Pick DRV8871EVM Texas Instruments From our database
DRV8871EVM is the best engineering choice here because it is more efficient and practical for driving a pump or auger motor than the older 101277 L298N board, while avoiding the bulk and inefficiency of the MAX14870EVKIT#.
Mouser $66.99 (5 in stock) Digikey
MAX14870EVKIT# Analog Devices Inc./Maxim Integrated From our database
Brushed DC motor driver evaluation kit is useful for quickly prototyping pump or auger control, especially if your dispensing mechanism uses a small brushed motor. It is a complete assembled board, but it is still an evaluation platform rather than a compact final prototype module.
101277 Soldered From our database
L298N dual H-bridge board is easy to use for basic motor control and is widely understood by hobbyists. It is not efficient, but it is acceptable for a prototype if your motors are small and you can tolerate heat and voltage drop.
Power Supply
Top Pick GST60A12-P1J Mean Well
GST60A12-P1J is the best starting point because a 12 V adapter gives you a practical prototype rail for motors, valves, and downstream regulation without forcing you into mains wiring inside the machine right away.
Mouser $19.40 (5,429 in stock)
RS-25-12 Mean Well
Compact 12 V enclosed supply if you are building the prototype into a chassis and want an internal mains-powered supply. Good for powering motors and downstream regulators, but requires proper mains wiring and enclosure design.
Mouser $10.80 (2,926 in stock)
DPS-30-5 Mean Well
5 V supply option if your prototype uses only low-power pumps/valves and a separate heater supply, but it is usually too small as the only supply for a beverage machine. Better as a secondary rail than the main source.
Connectivity
Top Pick ESP32-WROOM-32E Espressif Systems From our database
ESP32-WROOM-32E is the best connectivity option if you want networking, because it is modern, widely supported, and much more capable than the RN-171 for prototype remote monitoring or service features.
Dev Board 102010572 Seeed Studio
Ready-to-use board for prototyping with this chip
Mouser $14.99 (194 in stock)
WIZ850io WIZnet From our database
Ethernet module with hardware TCP/IP offload, useful for a reliable wired connection in a kitchen or lab environment. Good if you want deterministic connectivity and less RF uncertainty than WiFi.
RN-171 Microchip Technology
Simple WiFi module for basic network connectivity, though less modern than ESP32-based options. It can work if you want a small serial WiFi bridge for telemetry or remote control.
Display
Top Pick MDT0700JISC-HDMI Midas Displays From our database
MDT0700JISC-HDMI is the best display choice because it combines a good 1024 x 600 resolution with HDMI and USB touch, which makes it easy to pair with a Linux HMI.
NHD-7.0-HDMI-N-RSXP-CTU Newhaven Display From our database
7-inch HDMI IPS display with capacitive touch, good viewing angles, and simple integration for a Linux-based front panel. Strong choice for a clean HMI prototype.
HTT70G-TPC-BLM-B0-H6-CH-V5 Matrix Orbital From our database
Industrial-grade 7-inch HDMI touch display, suitable if you want a more rugged panel feel. Resolution is lower than the Midas part, but it is still a practical HMI display.

Compatibility Notes

  • The Linux HMI and the Cortex-M MCU should communicate over UART, USB, or Ethernet; keep the control boundary clear so the MCU handles all safety-critical dispensing logic.
  • The recommended flow sensor and float sensor are MCU-friendly digital devices, but the RTD will need an analog front end or RTD interface circuit because the MCU cannot read it directly.
  • The display is HDMI plus USB touch, so it belongs on the Linux side, not the MCU side.
  • If you use 12 V as the main rail, you will still need local 5 V and 3.3 V regulation for logic, sensors, and any module that does not accept 12 V directly.
  • Motor and heater loads can create electrical noise; separate power routing and flyback protection are important to keep the MCU and HMI stable.

You'll Also Need

  • Linux compute module or SBC for the HMI, since no suitable Linux board was provided in the database.
  • RTD signal conditioning or an RTD-to-digital converter IC/module.
  • Flyback diodes, snubbers, fuses, TVS protection, connectors, wiring harnesses, and terminal blocks.
  • Pump, heater, solenoid valves, and any mechanical dispensing hardware.
  • Food-safe tubing, fittings, tank, boiler/thermoblock, and enclosure.
  • If chocolate is dispensed as a heated liquid, you may also need a stirrer or auger mechanism and anti-clogging design.
Estimated BOM Cost: $345-405 (based on live distributor pricing)

Design Considerations

Thermal Control
Coffee and hot-water systems need tighter temperature control than most hobby projects. A probe RTD like the HEL-705-T-0-12-00 is a good start, but you should expect to add a proper RTD front end and implement closed-loop control with hysteresis or PID. For a prototype, validate temperature at the outlet, not just at the heater, because plumbing losses can be significant.
Dispense Accuracy
Use the 114991177 flow sensor to measure delivered volume rather than relying only on pump run time. Hall sensors are good for repeatable pulse counting, but they can drift with viscosity, bubbles, and partial clogs, especially with chocolate. Add timeout and minimum-flow fault detection so the machine can stop if the line is blocked or empty.
Reservoir Safety
The 13835 float sensor is a simple and reliable empty/full interlock for a prototype, and it is often better than trying to infer level from pump behavior. If you later move to a capacitive approach with MTCH9010-E/REB, test it with the actual tank material and liquid because wall thickness and residue can change sensitivity. For safety, treat low-level detection as a hard stop for heater and pump operation.
Motor and Pump Drive
For beverage machines, motor drivers need to survive stall current, startup surges, and frequent on-off cycling. Add flyback protection and keep motor wiring physically away from the RTD and MCU analog traces.
HMI Architecture
Keep the Linux HMI focused on recipes, status, and user interaction, while the MCU owns all real-time control and safety interlocks. That split prevents UI crashes from affecting heater or pump control. Use a watchdog and a heartbeat between Linux and MCU so the machine can fail safe if the HMI freezes.
Prototype Power Budget
A 12 V supply like GST60A12-P1J is a sensible prototype backbone because pumps, valves, and motors often need more current than a USB-powered setup can provide. Budget separate rails for logic and actuation, and assume the motor rail will be noisy. If you later add a heater, its power will dominate the design and may require mains-rated switching and thermal cutoffs.

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