Electrical
Two packs in series make a 44.4 V bus. It passes a breaker, a contactor held closed by the E-stop loop, and a distribution block, then splits into four limb chains. Each chain carries 48 V and CAN in one XT30(2+2) connector per actuator. 12 V for the computer comes off the same block.
Power system
| From | To | Voltage | Wire | Connectors |
|---|---|---|---|---|
| Pack 1 − | Pack 2 + (series link) | 44.4 V nominal, 50.4 V full | 12 AWG silicone | EC5 |
| Pack 1 + | Breaker → contactor → distribution block | 48 V | 12 AWG silicone | EC5 at the pack; ring terminals |
| Pack 2 − | Distribution block, ground bar | 0 V | 12 AWG silicone | EC5; ring terminal |
| Distribution block | First actuator of each of the four chains | 48 V | 18 AWG silicone + CAN pair | XT30(2+2) |
| Each actuator | Next actuator in the chain | 48 V | 18 AWG silicone + CAN pair | XT30(2+2), in and out sockets on the actuator |
| Distribution block | 10 A fuse → 48→12 V converter | 48 V | 18 AWG | Ring terminals |
| Converter 12 V | Mini PC, USB hub, servo driver, contactor coil via the E-stop | 12 V | 16 AWG (PC), 18 AWG (rest) | 5.5 × 2.5 mm barrel (PC); screw terminals |
Safety chain
- Breaker: the main disconnect and pack over-current protection. Off whenever anyone works inside the torso.
- Contactor: carries the motor bus; its 12 V coil is fed through the E-stop's normally-closed contact. Pressing the E-stop opens the coil circuit and drops the motor bus; the computer stays powered so logs survive.
- E-stop on the back panel, a second one wired in series on a 3 m lead for the person on the hoist.
- Fuses: 60 A on the pack lead inside the distribution block; 10 A on the 12 V feed.
- TVS diodes across 48 V and ground at the distribution block and at each chain's end, to clamp regenerative spikes when the contactor opens under load.
- A powered-down robot collapses. The E-stop is for stopping motion; the hoist is for not dropping the robot.
CAN bus
Four buses at 1 Mbit/s, one CANable PRO V2.0 each. Every bus is a single daisy chain, adapter → actuator → actuator, with a 120 Ω terminator at each physical end and no stubs. Six actuators per bus at a 500 Hz command rate is about 35 % bus load.
| Bus | Actuators | CAN IDs | Terminator |
|---|
Check: an unpowered bus reads about 60 Ω between CAN_H and CAN_L. 120 Ω means a terminator is missing; 40 Ω means there is one too many.
The actuator map
| Joint | ID | Bus | Model | Joint | ID | Bus | Model |
|---|
IDs are unique robot-wide so a mis-plugged chain is detected, not obeyed. Setting them: Motor ID and config.
USB
| Port | Device |
|---|---|
| PC USB 3, port 1 | Powered hub: four CANable adapters, IMU, gripper servo driver |
| PC USB 3, port 2 | Camera, if fitted (needs USB 3 on its own port) |
Harness fabrication
Every cable on the robot is one of the types below. Red is +, black is −; CAN_H yellow, CAN_L blue throughout. Solder the XT30 cups (iron about 400 °C); never mate or unmate a power connector under power.
| Cable | Conductors | End A | End B | Carries |
|---|---|---|---|---|
| Actuator drop | 2 × 18 AWG + 1 twisted pair | XT30(2+2) female | XT30(2+2) female | 48 V and CAN, actuator out socket to the next actuator's in socket. Pin 1 +, 2 −, 3 CAN_L, 4 CAN_H (Amass XT30(2+2) numbering; verify on your actuator's board) |
| Bus head | 2 × 18 AWG + 1 pair | Distribution block ring terminals + CANable screw terminals, 120 Ω across H–L | XT30(2+2) female | 48 V and CAN into the first actuator of a chain |
| Bus tail terminator | — | 120 Ω across CAN_H–CAN_L in an XT30(2+2) shell | — | Plugs into the last actuator's out socket |
| CAN pair | One pair from Ethernet cable | — | — | Coloured conductor → CAN_H, white → CAN_L; keep twisted to the connector |
| Pack lead, series link | 12 AWG silicone | EC5 | Ring terminal / EC5 | 48 V trunk |
| Computer feed | 16 AWG | Converter 12 V terminals | 5.5 × 2.5 mm barrel | 12 V |
| E-stop loop | 2 × 22 AWG | Converter 12 V | Contactor coil, via the E-stop NC contact | 12 V, a few hundred milliamps |
Check: each finished cable conducts pin to pin, has no short between pins, and is labelled at both ends with its bus.
Routing
| Run | Route |
|---|---|
Leg chains (can0, can1) | From the distribution block down through the bottom-plate cut-outs into the pelvis, hip-pitch actuator first, then hip roll, hip yaw, knee, ankle pitch, ankle roll; terminator at the ankle-roll actuator |
Arm chains (can2, can3) | Waist actuator first on can2, then out through the shoulder mount to shoulder pitch, roll, yaw, elbow, wrist; terminator at the wrist |
| Gripper servo (optional) | Alongside the arm chain to the wrist; three-wire servo bus |
- Leave a service loop at every joint sized for the joint's full travel, not one pose.
- Sleeve limb runs in braided loom; tie to the printed brackets' loom slots, never across a moving edge.
- Turn every joint to both ends by hand before a limb is closed: no cable taut, pinched or rubbing.
Pre-power checks
With no pack connected and the breaker off:
- Every 48 V conductor conducts end to end; + to − on each chain reads open (the drive capacitors charge slowly; no steady short).
- Every XT30(2+2): + on pin 1, − on pin 2, CAN_H on pin 4, checked against the pinout, not the colour.
- Each of the four buses reads about 60 Ω between CAN_H and CAN_L.
- The 48→12 V converter gives 12 V on a bench supply before it sees a pack.
- The E-stop loop: with 12 V applied, the contactor clicks in; pressing the E-stop drops it out.
- Both packs: no swelling, cells balanced within 0.02 V, then the series link.
Then First power-on, robot hanging.