Coffee Machine Control Board Design
Route the PCB with explicit AC-load trace widths and AC/DC keepout rules.
Re-run DRC after routing and fix any clearance/overlap issues.
Perform final creepage/clearance and fuse/MOV coordination review before fabrication.
Thought for 5 sec
I’ll set routing constraints for the 2A AC load paths and AC/DC separation, run routing, then re-check DRC and document the remaining safety review items.
Thought for 10 sec
I’m blocked because your account has no available ACUs, so I can’t continue routing or running checks right now.
Accomplished this session:
- Acknowledged the routing/safety task.
- Created the routing/check/review task list.
Still to do once ACUs are available:
- Apply AC-load trace width and AC/DC keepout rules.
- Route the PCB.
- Re-run DRC and fix clearance/overlap issues.
- Document final creepage/clearance and fuse/MOV coordination review before fabrication.
Check ACU options
Save requirements note
List manual rules
Find rule settings
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Design Notes — Teensy Coffee Machine Controller
Architecture
- Controller: Teensy 4.1 socket target using 0.1 in female headers.
- Power: external 5V input on J18 feeds Teensy VIN/5V and relay coils; Teensy 3.3V rail feeds MAX31855/MAX31865 sensor ICs.
- Relay outputs: K1-K5 are 5V coil SPDT relays. COM and NO are broken out on J1-J5 for 120VAC 2A switched loads. NC contacts are intentionally unused.
- Relay drive pins: Teensy pins 2, 3, 4, 5, 6 drive Q1-Q5 via R1-R5. Q1-Q5 are low-side MOSFET coil drivers with D1-D5 flyback diodes to 5V.
- Thermocouples: U2-U4 are MAX31855KASA+ Type K converters. J6-J8 break out T+/T- thermocouple inputs.
- RTD: U5 is MAX31865AAP+T. J9/J10 provide a 4-wire-style breakout for PT100/PT1000 wiring options. Final reference resistor/configuration should be verified against the desired PT100 or PT1000 mode before layout/manufacture.
- Analog inputs: J11/J12 feed two resistor dividers into Teensy pins 16 and 17.
- UART: J19 is a 1x4 2.54mm header: 3V3, Teensy pin 7, Teensy pin 8, GND.
Pin Map
Table
| Function | Teensy pin | Net |
|---|---|---|
| Relay 1 | 2 | RELAY1_GPIO |
| Relay 2 | 3 | RELAY2_GPIO |
| Relay 3 | 4 | RELAY3_GPIO |
| Relay 4 | 5 | RELAY4_GPIO |
| Relay 5 | 6 | RELAY5_GPIO |
| UART breakout | 7 | UART1_RX_PIN7 |
| UART breakout | 8 | UART1_TX_PIN8 |
| Thermocouple 2 CS | 9 | TC2_CS |
| Thermocouple 1 CS | 10 | TC1_CS |
| SPI MOSI | 11 | SPI_MOSI |
| SPI MISO | 12 | SPI_MISO |
| SPI SCK | 13 | SPI_SCK |
| Thermocouple 3 CS | 14 | TC3_CS |
| RTD CS | 15 | RTD_CS |
| Analog divider 1 | 16 | AIN1_DIVIDED |
| Analog divider 2 | 17 | AIN2_DIVIDED |
Important Assumptions / Open Items
- The requested “2kΩ / 2kΩ divider with 2/3 ratio” is mathematically inconsistent: equal resistors give 1/2 ratio. I implemented the explicit 2kΩ / 2kΩ values and flagged this for confirmation.
- Mains load switching requires layout creepage/clearance, relay contact spacing, terminal ratings, enclosure safety, fusing, and compliance review before fabrication.
- The 5V supply must be sized for Teensy current plus all relay coils energized simultaneously.
- RTD MAX31865 reference resistor and 2/3/4-wire configuration should be finalized for PT100 vs PT1000 accuracy requirements.
Architecture
Pin Map
Important Assumptions / Open Items
