# MASTER PROMPT — SINGLE-PUMP DRINK DISPENSER PCB

Act as an expert electronics engineer, PCB designer, embedded engineer, power engineer, and firmware engineer.

Design **ONLY ONE complete drink-dispenser pump channel** as a real PCB using individual components. This will become the repeatable building block for a future 30-pump machine.

## HARDWARE

Control:

```text
MCU → Relay Driver → Relay → 12V DC Pump
```

Include:

* Bare MCU IC
* 1 × 12V DC pump output
* 1 × relay
* Relay driver transistor/MOSFET
* Gate/base resistor
* Pull resistor if required
* Relay flyback diode
* Pump connector
* 12V input connector
* Fuse
* Reverse-polarity protection
* Overcurrent protection
* TVS/filtering where appropriate
* Power/status LEDs
* Test button
* Emergency-stop input
* USB-C 5V logic/development input
* Programming/debug connector
* Expansion header

Do NOT use:

* Arduino boards
* Ready-made relay modules
* Ready-made pump controllers

## POWER

Design:

```text
12V DC
 ├── Relay
 └── Pump

12V
 ↓
5V / 3.3V REGULATOR
 ↓
MCU
```

USB-C provides **5V only for logic/development** and must NOT directly power the 12V pump.

Include proper USB-C protection, ESD, OCP, OVP, reverse protection, and filtering.

Keep high-current pump paths separated from MCU/logic circuitry.

## RELAY/PUMP

The MCU must never directly drive the relay.

Use:

```text
MCU GPIO
 ↓
Driver
 ↓
Relay Coil
 ↓
GND
```

Use the relay's **normally-open (NO)** contact so the pump is OFF by default.

Select relay, connector, fuse, MOSFET/transistor, traces, and protection based on the actual pump current.

If pump current is unknown, **STOP and request the pump's exact model, operating current, startup current, and stall current. Do not guess.**

## MCU

Use the simplest practical bare MCU.

Required:

* GPIO
* UART
* Programming/debug
* Watchdog
* Brownout/reset protection
* Optional I2C/SPI/ADC for future expansion

The default state after power-up/reset/crash must always be:

```text
PUMP OFF
```

## CONTROLS

Include:

```text
TEST PUMP BUTTON
POWER LED
MCU LED
RELAY/PUMP LED
E-STOP INPUT
```

Test button should run the pump for a safe maximum time.

Emergency stop must disable the pump safely and should not depend entirely on firmware.

## FIRMWARE

Provide basic firmware for:

* Pump ON/OFF
* Timed dispensing
* Test button
* Emergency stop
* Watchdog
* Safe startup
* Maximum pump runtime

Example:

```text
BOOT
 ↓
SELF TEST
 ↓
PUMP OFF
 ↓
WAIT
 ↓
COMMAND
 ↓
RELAY ON
 ↓
PUMP RUNS
 ↓
TIMEOUT
 ↓
RELAY OFF
```

## EXPANSION

Add a small labeled expansion header:

```text
3.3V
5V
GND
GPIO
ADC
I2C
SPI
UART
INT
```

Reserve resources for future:

* Flow sensors
* Liquid-level sensors
* Touchscreen
* Additional pumps
* Wi-Fi/Bluetooth
* Camera
* Other sensors

## PCB DESIGN

Provide:

1. Complete schematic
2. Every component and value
3. MCU pinout
4. Relay circuit
5. Pump circuit
6. Power circuit
7. Protection
8. Connector pinouts
9. PCB layout recommendation
10. Trace-width calculations
11. Thermal/current calculations
12. Complete BOM with manufacturer part numbers
13. Test points
14. ERC/DRC considerations
15. Manufacturing recommendations
16. Firmware
17. Step-by-step test procedure

Clearly identify:

```text
HIGH-CURRENT PATHS
LOW-VOLTAGE LOGIC
GROUND
12V
5V
3.3V
PUMP
RELAY
USB-C
E-STOP
PROGRAMMING
```

## VALIDATION

Before connecting the pump:

1. Inspect PCB
2. Check for shorts
3. Test 12V
4. Test 5V
5. Test 3.3V
6. Program MCU
7. Test GPIO
8. Test relay driver
9. Test relay
10. Test emergency stop

Then connect the pump and test timed operation.

## FUTURE 30-PUMP SYSTEM

Design this as **CHANNEL 01**.

Clearly separate:

**PER CHANNEL:**

* Relay
* Relay driver
* Protection
* Pump connector
* Status LED

**SHARED:**

* MCU
* Main power regulation
* USB-C
* Programming
* Communications

The final circuit must be easy to duplicate:

```text
CHANNEL 01 → CHANNEL 02 → ... → CHANNEL 30
```

Do NOT design the 30-channel board yet.

## MOST IMPORTANT RULE

**DO NOT GUESS MISSING ELECTRICAL SPECIFICATIONS.**

Before finalizing, identify anything I must provide, especially:

* Exact pump model
* Pump voltage
* Operating current
* Startup current
* Stall current
* Power supply
* Desired pump runtime
* PCB size

Final goal:

**ONE MCU + ONE RELAY + ONE 12V PUMP + POWER + PROTECTION + SAFETY + EXPANSION**

Create a professional, reliable prototype that can later be duplicated into a 30-pump drink dispenser.