Hardware documentation¶

Automator – electrical and control system¶

This document describes the complete electrical and electromechanical hardware of the Automator system. It is derived from the system schematic, explicit author clarification, and the authoritative printer.cfg.

Software behaviour, motion planning logic, and mechanical CAD are intentionally excluded.

1. System overview¶

The Automator hardware consists of:

Raspberry Pi (host controller, cameras, web UI)
MKS Robin Nano V3.1 (Klipper motion controller)
Independent AC-powered DC supplies
Stepper-driven X, Y, and Z motion
Plate handling system:
Vacuum pump
Air solenoid valve
Suction cup
Servo-driven suction cup rotation
Imaging system:
LED illumination
USB camera (QR scanning)
Raspberry Pi camera (plate imaging)
Safety systems:
AC-side emergency stop
Door interlock
Axis end-stops

All safety-critical power removal is implemented in hardware.

2. Power architecture¶

2.1 AC input and emergency stop¶

Mains AC feeds all DC power supplies
A physical, latching emergency stop switch is wired on the AC side
Activating the E-stop removes AC power from:
12 V DC power supply
5 V peripheral DC power supply
Raspberry Pi 5 V adaptor

This is a true electrical power cut and does not rely on software. Reference photo of the external E-stop wiring: images/estop.jpg.

2.2 DC power domains¶

Rail	Source	Loads
12 V DC	AC to DC adaptor	MKS Robin Nano V3.1, X/Y/Z stepper motors, vacuum pump, air solenoid
5 V DC (peripherals)	Buck converter	Servo, relay coils, sensors, LED logic
5 V DC (Raspberry Pi)	Separate AC to DC adaptor	Raspberry Pi only
GND	Common	All DC domains

Explicit clarifications:

The buck converter does not power the Raspberry Pi
The Raspberry Pi uses a dedicated isolated 5 V supply
12 V is used only for motors, the MKS board, and vacuum hardware
Both 12 V and 5 V supplies are disconnected by the AC emergency stop

3. Power tree¶

Mains AC
└── Emergency Stop (AC-side, latching)
    |
    |
    ├── AC --> 12 V DC PSU
    │          ├── MKS Robin Nano V3.1
    │          │   ├── X stepper motor
    │          │   ├── Y stepper motor
    │          │   └── Z stepper motor
    │          |   
    │          └── 12 V --> 5 V Buck Converter
    │                       ├── Servo motor
    │                       ├── Proximity Sensor
    |                       ├── Vacuum Pump
    |                       ├── 80 MM 5V fans(2 no.s)
    |                       ├── Small 5v Fan Z motor
    |                       ├── Air Solenoid
    │                       ├── Relay Module
    │                           └── LED Strip light
    │
    └── AC --> 5 V DC PSU (Raspberry Pi adaptor)
               └── Raspberry Pi

All grounds are made common.

4. Controllers¶

4.1 Raspberry Pi¶

Functions:

Klipper host
Camera control
Web UI and scheduler

Power:

Dedicated 5 V adaptor
Power removed by AC emergency stop

The Raspberry Pi does not directly drive motors, solenoids, or other inductive loads.

4.2 MKS Robin Nano V3.1¶

Functions:

Motion control (Klipper MCU)
Step / Direction / Enable outputs
End-stop processing
Servo and relay control outputs

Power:

12 V DC
Disabled immediately by AC emergency stop

5. Motion system¶

Axis	Motor Type	Supply
X	Stepper motor	12 V
Y	Stepper motor	12 V
Z	Stepper motor	12 V

Stepper power is fully removed when the emergency stop is activated.

6. Plate handling and imaging hardware¶

6.1 Vacuum system¶

Functional chain:

Vacuum pump generates negative pressure
Air solenoid valve controls vacuum routing
Vacuum is applied to a suction cup
Suction cup grips and lifts the Petri dish lid

Electrical control:

Vacuum pump powered from 5 V via Air solenoid
Air solenoid powered from 5 V
Relay coils powered from 5 V peripheral rail

Vacuum is enabled only during imaging and is disabled by the emergency stop.

6.2 Servo – suction cup rotation¶

Purpose:

Rotates the suction cup by 0 or 90 degrees
Moves the lid away from the base plate during imaging
Prevents obstruction of the raspberry camera field of view

Electrical details:

Supply: 5 V (buck converter)
Control: Software PWM
Positions: 90° (over plate), 0° (rotated away)

6.3 LED illumination¶

LED strip powered from 5 V peripheral rail
Switched via relay
Enabled only during image capture

7. Sensors and inputs¶

7.1 Door interlock¶

Property	Value
Type	Proximity sensor
Logic	Normally open
Wiring	GPIO to GND
Pull-up	Enabled

Opening the enclosure door triggers a controlled halt and park.

7.2 End-Stops¶

Axis	End-stop
X	Present
Y	Present
Z	Present

All end-stops are normally open and ground-triggered.

7.3 Proximity sensor¶

Powered from 5 V peripheral rail
Digital output
Used to detect door open/closed state for the door interlock

8. Pin Mapping (from printer.cfg)¶

Controller MCU: STM32F407 (MKS Robin Nano V3.1)

8.1 Stepper motors and End-Stops¶

Axis	Function	MCU Pin	Notes
X	STEP	PE3
X	DIR	PE2	Inverted
X	ENABLE	PE4	Inverted
X	ENDSTOP	PA15	Pull-up enabled
Y	STEP	PE0
Y	DIR	PB9
Y	ENABLE	PE1	Inverted
Y	ENDSTOP	PD2	Pull-up enabled
Z	STEP	PB5
Z	DIR	PB4	Inverted
Z	ENABLE	PB8	Inverted
Z	ENDSTOP	PC8	Pull-up enabled

8.2 Actuators¶

Device	Function	MCU Pin	PWM Type	Notes
Servo	Suction cup rotation	PA0	Software PWM	0–90°
Vacuum pump	Vacuum generation	PE5	Software PWM	Drives relay
Solenoid valve	Vacuum routing	PB0	Software PWM	Drives relay

8.3 Raspberry Pi interfaces¶

Function	Interface	Notes
Klipper host	USB serial	`/dev/serial/by-id/...`
Pi camera	CSI	Plate imaging
USB camera	USB	QR scanning

No Raspberry Pi GPIO pins are used for motion control.

8.4 Raspberry Pi connections¶

8.4.1 GPIO¶

GPIO	Function
GPIO 4	LED relay pulse output
GPIO 13	Buzzer output (physical pin 33)
GPIO 17	START button input
GPIO 23	Relay control for 5 V LED strip
GPIO 26	Door sensor input
GPIO 27	STOP / pause button input

8.4.2 Cameras¶

Interface	Device
CSI	Raspberry Pi camera (plate imaging)
USB	USB camera (QR scanning)

8.4.3 USB interfaces¶

USB Connection	Purpose
USB --> MKS Robin Nano V3.1	Klipper serial communication
USB --> Camera	Imaging input

9. Detailed hardware references and datasheets¶

This section provides manufacturer-level documentation for all major electronic components used in the Automator system.

9.1 Raspberry Pi camera module 3¶

Function:

High-resolution plate imaging

Interface:

MIPI CSI-2 (22-pin ribbon cable)

Power:

Supplied directly from Raspberry Pi CSI connector

Image: Raspberry Pi Camera Module 3

References:

9.2 Raspberry Pi 4 model B¶

Role:

Klipper host
Camera acquisition
Web UI and system orchestration

Processor:

Broadcom BCM2711

Power:

Dedicated 5 V AC adaptor
Power removed by AC emergency stop

GPIO usage in Automator:

GPIO 4 – LED relay pulse output
GPIO 13 – Buzzer output (physical pin 33)
GPIO 17 – START button input
GPIO 23 – LED relay control
GPIO 26 – Door sensor input
GPIO 27 – STOP / pause button input

Image: Raspberry Pi GPIO Pinout

Datasheets:

Reference: https://www.raspberrypi.com/documentation/computers/processors.html#bcm2711

9.3 MKS Robin Nano V3.1 motion controller¶

Role:

Motion control (Klipper MCU)
Step/Direction outputs
End-stop processing
Servo and relay control

MCU:

STM32F407

Power:

12 V DC
Disabled by AC emergency stop

Image: MKS Robin Nano v3.1

Hardware repository: https://github.com/makerbase-mks/MKS-Robin-Nano-V3.X/tree/main/hardware/MKS%20Robin%20Nano%20V3.1_001

9.4 USB camera¶

Function:

QR / code scanning

Interface:

USB 2.0 (UVC compliant)

Power:

5 V supplied from Raspberry Pi USB port

Image: USB Camera

Reference: https://www.amazon.co.uk/gp/product/B0BL77FXPV/

10. Parts list (electrical)¶

Controllers¶

Raspberry Pi 4B 8 GB RAM, 64 GB Storage
MKS Robin Nano V3.1

Power¶

Latching emergency stop switch (AC rated) Emergency stop switch:
12 V AC to DC power supply
5 V AC to DC power supply (Raspberry Pi)
DC buck converter (12 V to 5 V, peripherals)

Motion¶

Stepper motors (X, Y, Z)

NEMA17: NEMA 17 Stepper motor

Plate handling¶

Vacuum pump (12 V)
Air solenoid valve (12 V)
Suction cup and vacuum tubing

Vacuum Apparatus: Vacuum

Servo motor (5 V, PWM)

MG995 SERVO: Servo motor

Switching and isolation¶

Relay modules (5 V coil) Relay:

Imaging¶

LED strip or LED module
Raspberry Pi camera
USB camera

Sensors and safety¶

Mechanical end-stop switches (X, Y, Z) End stop switch:
Proximity sensor Proximity sensor:

Miscellaneous¶

Wiring and connectors
Fuses (via Emergency Stop)
Grounding hardware

11. Safety notes¶

Emergency stop removes power at the AC level
Motors, solenoids, and logic do not rely on software for shutdown
Software safety features are supplementary only

Path	Description
hardware/	Schematics and wiring
config/printer.cfg	MKS Pin configuration
documentation/	Network configuration
mechanical/	CAD and assemblies

13. Disclaimer¶

This hardware design is provided as-is for research use. Users are responsible for electrical safety, compliance, and validation.

Refer to main project repository for disclaimer, License and use¶

Document updated 30/06/2026 Rohan R
The Sainsbury Laboratory, Norwich

Hardware documentation¶

Automator – electrical and control system¶

1. System overview¶

2. Power architecture¶

2.1 AC input and emergency stop¶

2.2 DC power domains¶

3. Power tree¶

4. Controllers¶

4.1 Raspberry Pi¶

4.2 MKS Robin Nano V3.1¶

5. Motion system¶

6. Plate handling and imaging hardware¶

6.1 Vacuum system¶

6.2 Servo – suction cup rotation¶

6.3 LED illumination¶

7. Sensors and inputs¶

7.1 Door interlock¶

7.2 End-Stops¶

7.3 Proximity sensor¶

8. Pin Mapping (from printer.cfg)¶

8.1 Stepper motors and End-Stops¶

8.2 Actuators¶

8.3 Raspberry Pi interfaces¶

8.4 Raspberry Pi connections¶

8.4.1 GPIO¶

8.4.2 Cameras¶

8.4.3 USB interfaces¶

9. Detailed hardware references and datasheets¶

9.1 Raspberry Pi camera module 3¶

9.2 Raspberry Pi 4 model B¶

9.3 MKS Robin Nano V3.1 motion controller¶

9.4 USB camera¶

10. Parts list (electrical)¶

Controllers¶

Power¶

Motion¶

Plate handling¶

Switching and isolation¶

Imaging¶

Sensors and safety¶

Miscellaneous¶

11. Safety notes¶

12. Related files¶

13. Disclaimer¶

Refer to main project repository for disclaimer, License and use¶