Wiring & power
OpenDerm includes mains voltage, high-current power supplies, and motorized mechanisms. Disconnect and verify power is off before wiring or servicing the system. Follow applicable electrical codes, and consult a qualified electrician if you are unfamiliar with mains wiring. Use appropriate grounding, overcurrent protection, enclosures, and strain relief, and test the emergency stop before operation. These research schematics are not a substitute for professional electrical design or inspection.
Electrical system overview
The diagram below maps the robotic system’s electrical components and connections. The sections that follow provide detailed schematics and connection lists for each subsystem.
Wiring guide
The wiring guide is organized by subsystem. Each section includes a schematic and lists every connection to and from that subsystem. Hover over a component to highlight its wiring.
- 01 AC input, emergency-stop circuit, and power supplies
- 02 Motion — drivers and motors
- 03 Control — compute, motion, and sensing
- 04 Endstops and homing
- 05 Distance sensors
Switching a 12 V sensor input with a 3.3 V GPIO
The HG-C1100-P’s external input—the pink lead—requires a 12 V control signal. A Raspberry Pi GPIO outputs only 3.3 V and must remain isolated from the 12 V circuit. The two-transistor level shifter shown below allows GPIO 5 or 6 to control the sensor input safely. Build one circuit for each sensor; the wiring diagrams identify them as -T1 and -T2.
How it works
Driving the GPIO high applies 3.3 V to the gate of the 2N7000. The gate pull-down keeps the circuit off while the GPIO is unconfigured or floating.
The 2N7000 turns on and pulls the 2N3906 base toward ground through the 10 kΩ base resistor.
The 2N3906 then turns on and applies 12 V to the sensor's pink input lead.
When the GPIO goes low, the 2N7000 turns off. The pull-up returns the 2N3906 base to 12 V, switching the sensor input off.
Parts
- 2N3906 — PNP high-side switch
- 2N7000 — N-channel MOSFET used as the level-shifting low-side switch
- 10 kΩ resistors, ×3 — Gate pull-down, base-current limiter, and base pull-up
- 12 V and ground — Shared with the sensor power circuit
Safety
Pressing the emergency-stop button opens the contactor-coil circuit. The LC1D25BD contactor then disconnects AC power from both motor supplies, de-energizing the 48 V gantry rail and the 24 V tilt-actuator rail. The control rail remains powered so the computer and controller continue operating.
Pressing the Omron A22E-M button interrupts the 24 V contactor-coil circuit.
De-energizing the coil opens the LC1D25BD contactor and removes AC power from both motor power supplies.
The 48 V and 24 V motor rails turn off, while the always-on control rail remains energized.
Fuse protection
Each AC and DC power branch has dedicated overcurrent protection. The table below lists each fuse, its rating and type, and the circuit it protects.
| Fuse | Rating | Type | Where |
|---|---|---|---|
| Mains → control PSU | 3 A | 250 VAC · time-delay | Wall to HDR-60-24 input |
| Contactor T1 → gimbal PSU | 10 A | 250 VAC · time-delay | To LRS-600N2-24 |
| Contactor T2 → gantry PSU | 15 A | 250 VAC · time-delay | To SE-1000-48 |
| 24 V line → E-stop | 1 A | fast-acting · DC ≥ 32 V | Just before the E-stop |
| HDR-60-24 output | 2 A | time-delay · DC ≥ 32 V | Right after the supply |