# M1. Bench it: power, one motor, a safe stop

> For agents: start with the [agent guide](https://parol6.build/llms.txt). Every page is Markdown by default; add `Accept: text/html` for HTML.

**Whole task:** take a bare control board and one motor from the box to a live bench rig. It powers on safely, reports its drivers, turns a motor, reads the E-stop and a switch, and stops when you cut the power.

## Parts

- The control board with six TMC5160 drivers, the GX16 power connector and its XT30 lead, the E-stop, one limit switch, and the power button with its JST PH lead. The [bill of materials](https://docs.source-robotics.com/PAROL-docs/1.1/build/bill-of-materials/) lists each one.
- One NEMA 17 motor, loose on the bench.
- A 24 V DC supply of at least 5 A ([Connecting, "The power supply"](https://docs.source-robotics.com/PAROL-docs/1.1/04-installation/connecting/)).
- A USB-B cable, a switched power strip within reach, a multimeter, and a computer with a serial terminal.

[Print timelapses](/lore/timelapses): [Plate 0: wrist and E-stop box](/lore/timelapses#timelapse-plate0-wrist-estop).

## Concepts

- **The robot system.** The arm, the control board and the PC each have a job. Every 10 ms the PC sends the board a packet ([Robot system](https://docs.source-robotics.com/PAROL-docs/1.1/01-overview/robot-system/); [Serial protocol](https://docs.source-robotics.com/PAROL-docs/1.1/board/10-serial-protocol/)).
- **Steppers and drivers.** A motor has 200 full steps per turn. The drivers run at 32 microsteps, so one motor turn is 6,400 microsteps. The motors run open loop, with no encoder ([Drives, ratios and resolution](https://docs.source-robotics.com/PAROL-docs/1.1/03-technical-data/drives-and-ratios/)).
- **Why the E-stop is normally closed.** Open means stop, so a cut wire or an unplugged button also stops the robot ([Connecting, "The E-stop"](https://docs.source-robotics.com/PAROL-docs/1.1/04-installation/connecting/)).
- **Why the mains switch matters.** It is the stop that still works when the PC software has frozen ([What you need](https://docs.source-robotics.com/PAROL-docs/1.1/01-overview/what-you-need/)).

## How-to

Open these official pages at the step that needs them:

- [Stepper drivers](https://docs.source-robotics.com/PAROL-docs/1.1/board/05-stepper-drivers/): the four ways to destroy the board, including a driver inserted backwards and a driver without its heatsink cemented on.
- [Electronics and wiring](https://docs.source-robotics.com/PAROL-docs/1.1/build/electronics-and-wiring/) and [Connecting](https://docs.source-robotics.com/PAROL-docs/1.1/04-installation/connecting/): supply polarity. The GX16 has no fixed +24 V pin, and the board has no reverse-polarity protection.
- [The test firmware](https://docs.source-robotics.com/PAROL-docs/1.1/board/09-test-firmware/): open a serial terminal that sends a line feed, then use `#IO`, `#LIMIT` and `#STOP`.

## Safety facts that shape the task

The test firmware turns every motor at 1000 steps per second from boot until the power goes off, and no command stops it. `#STOP` only ends a printout ([The test firmware](https://docs.source-robotics.com/PAROL-docs/1.1/board/09-test-firmware/), danger box).

So in M1 the safe stop is the switched mains strip, and the motor sits loose on the bench. Nothing is mounted in a joint yet.

## Practice

- Meter the supply output and mark + and −.
- Crimp and solder the GX16 plug.
- Check driver orientation by the DIAG pins. Repeat this on every power-on after touching the drivers.
- Drive the serial terminal until the commands are automatic.

## Done check

On camera, from cold:

1. Polarity is metered and marked.
2. The drivers are checked by their DIAG pins.
3. Power goes on through the switched strip.
4. The power-on report shows six `Connection is: GOOD` lines.
5. The motor turns.
6. `#IO` shows about 24000 mV and follows the E-stop as it is pressed and released.
7. `#LIMIT` names the switch while it is pressed.
8. The strip switch stops everything.

This is the build guide's own first check ([Firmware and first run](https://docs.source-robotics.com/PAROL-docs/1.1/build/firmware-and-first-run/), section 1), with only one motor connected.

**Settled: one motor is enough.** The `GOOD` or `BAD` line is an SPI check of the driver module, and the test firmware's open-load printing is commented out ([`main.cpp`, lines 868 to 936](https://github.com/Source-Robotics/PAROL6-Desktop-robot-arm/blob/e76f48d/PAROL6%20control%20board%20test%20code/src/main.cpp#L868-L936)). Swap motors only with the 24 V off.

At power-up you should hear clicks and see about 1.5 A drawn at 24 V. If not, disconnect ([PAROL6 setup and calibration, from 2:30](https://youtu.be/rv8zt6-3rvo?t=150)).

## Terms

- **TMC5160**: the stepper driver module, in the StepStick format, that the board takes six of. The firmware configures it over SPI ([Stepper drivers](https://docs.source-robotics.com/PAROL-docs/1.1/board/05-stepper-drivers/)).
- **microstep**: one of the 32 subdivisions of a full step the drivers run at, so one motor turn is 6,400 microsteps ([Drives, ratios and resolution](https://docs.source-robotics.com/PAROL-docs/1.1/03-technical-data/drives-and-ratios/)).
- **open loop**: control with no position feedback. The motors have no encoders, so the position is the count of steps commanded since homing ([Drives, ratios and resolution](https://docs.source-robotics.com/PAROL-docs/1.1/03-technical-data/drives-and-ratios/)).
- **normally closed**: a contact that conducts until it is pressed. The E-stop must be one, so pressing it, unplugging it or cutting its wire all stop the robot ([Connecting](https://docs.source-robotics.com/PAROL-docs/1.1/04-installation/connecting/)).
- **GX16**: the 2-pin circular connector that takes 24 V into the robot's base ([Connecting](https://docs.source-robotics.com/PAROL-docs/1.1/04-installation/connecting/)).
- **XT30**: the power connector on the control board that the GX16 socket is wired to ([Electronics and wiring](https://docs.source-robotics.com/PAROL-docs/1.1/build/electronics-and-wiring/)).
- **DIAG pins**: the two pins on a driver module that show its orientation. They must point at the red arrows in the official figure ([Stepper drivers](https://docs.source-robotics.com/PAROL-docs/1.1/board/05-stepper-drivers/)).
- **test firmware**: the bench firmware every board ships with. It checks the six drivers, turns every motor slowly and reports the inputs over USB ([The test firmware](https://docs.source-robotics.com/PAROL-docs/1.1/board/09-test-firmware/)).

## Video

[The M1 video](/lore/video-m1) is planned.

## Sources

1. [Robot system, PAROL6 docs 1.1](https://docs.source-robotics.com/PAROL-docs/1.1/01-overview/robot-system/)
   Source Robotics. The arm, the control board and the PC, and the 10 ms packet cycle. Accessed 2026-11-07.

2. [Drives, ratios and resolution, PAROL6 docs 1.1](https://docs.source-robotics.com/PAROL-docs/1.1/03-technical-data/drives-and-ratios/)
   Source Robotics. 200 steps per turn, 32 microsteps, open loop without encoders. Accessed 2026-11-07.

3. [Connecting, PAROL6 docs 1.1](https://docs.source-robotics.com/PAROL-docs/1.1/04-installation/connecting/)
   Source Robotics. GX16 power socket, polarity, the normally closed E-stop and the switch within reach. Accessed 2026-11-07.

4. [Stepper drivers, PAROL6 docs 1.1](https://docs.source-robotics.com/PAROL-docs/1.1/board/05-stepper-drivers/)
   Source Robotics. TMC5160 modules, DIAG pin orientation and the four ways to destroy the board. Accessed 2026-11-07.

5. [The test firmware, PAROL6 docs 1.1](https://docs.source-robotics.com/PAROL-docs/1.1/board/09-test-firmware/)
   Source Robotics. Power-on driver report, the #IO, #LIMIT and #STOP commands and the danger box. Accessed 2026-11-07.

6. [Electronics and wiring, PAROL6 docs 1.1](https://docs.source-robotics.com/PAROL-docs/1.1/build/electronics-and-wiring/)
   Source Robotics. The GX16 socket to the XT30 on the board, polarity checked twice. Accessed 2026-11-07.

7. [Firmware and first run, PAROL6 docs 1.1](https://docs.source-robotics.com/PAROL-docs/1.1/build/firmware-and-first-run/)
   Source Robotics. The build guide's first bench check, which this milestone's done check follows. Accessed 2026-11-07.

8. [PAROL6 setup and calibration](https://youtu.be/rv8zt6-3rvo)
   Source Robotics on YouTube. The power-up clicks and current draw to expect, at 2:30. Accessed 2026-11-07.

## Lore on this page

- [The PAROL6 milestones](/lore/milestones)
- [M3. The whole arm moves](/lore/m3-whole-arm)

## What links here

- Agent guide → Joel builds a PAROL6 robot arm, one sourced and filmed milestone at a time. → [Read page](https://parol6.build/llms.txt)

- Build steps by milestone → The official how-to pages for each milestone, in build order, gathered from the milestone pages. → [Read page](https://parol6.build/lore/build-steps)

- Change log → What changed in the files served here, newest first. → [Read page](https://parol6.build/log)

- Concepts by milestone → The mental models each milestone teaches, gathered from the milestone pages, with the glossary for single terms. → [Read page](https://parol6.build/lore/concepts)

- Full agent guide → Joel builds a PAROL6 robot arm, one sourced and filmed milestone at a time. → [Read page](https://parol6.build/llms-full.txt)

- M1 video: Bench it → The video for milestone 1 is planned and not yet recorded. → [Read page](https://parol6.build/lore/video-m1)

- M2. One joint end to end: the wrist and joint 6 → The second milestone prints, assembles and wires the wrist, proves its homing sensor triggers, then jogs joint 6 to a commanded angle and measures the result. → [Read page](https://parol6.build/lore/m2-one-joint)

- M3. The whole arm moves → The third milestone builds the rest of the arm from the wrist down to the base, tests the wiring, then homes the arm, jogs every joint and checks the witness marks. → [Read page](https://parol6.build/lore/m3-whole-arm)

- Milestone videos → Each milestone ends in one video, and every video is planned until Joel publishes it. → [Read page](https://parol6.build/lore/videos)

- PAROL6 build → Joel builds a PAROL6 robot arm, one sourced and filmed milestone at a time. → [Read page](https://parol6.build/)

- PAROL6 wiki | PAROL6 build → The PAROL6 build wiki: the milestones, their videos and the official sources behind them. → [Read page](https://parol6.build/lore)

- Parts by milestone → What goes on the bench at each milestone, gathered from the milestone pages and the official bill of materials. → [Read page](https://parol6.build/lore/parts)

- Print timelapses → Every PAROL6 print plate as a sped-up video from the printer's camera, with its parts, material, layer count, print time and milestones. → [Read page](https://parol6.build/lore/timelapses)

- Source change history (log.md) → The generated change log as Markdown. → [Read page](https://parol6.build/log.md)

- The PAROL6 milestones → Seven milestones take the build from a bare control board to a robot arm that plays a Eurorack skiff. → [Read page](https://parol6.build/lore/milestones)

## Unlinked mentions

- [M2. One joint end to end: the wrist and joint 6](https://parol6.build/lore/m2-one-joint) → The motor turns freely on the test firmware, so keep fingers clear (The test firmware).¶

- [M3. The whole arm moves](https://parol6.build/lore/m3-whole-arm) → Open loop and lost steps.

- [Parts by milestone](https://parol6.build/lore/parts) → The control board with six TMC5160 drivers, the GX16 power connector and its XT30 lead, the E-stop, one limit switch, one NEMA 17 motor loose on the bench, and a 24 V DC supply of at least 5 A.