SMD Version 4.1 User Manual

SMD(Simple Magnetic Detector) is a magnetic detector for magicians and mentalists, built on the Apple Watch. It offers real-world performance comparable to, and often beyond, dedicated devices, while removing the need to carry, charge, and manage separate hardware. With practical sensitivity control on the watch itself, SMD provides a more convenient and discreet alternative for everyday use and performance.

Updated for SMD 4.1 This manual reflects the current behavior, terminology, and user interface of SMD 4.1. It is intended for end users and is written to match the latest app behavior rather than older documentation.

Starting with SMD 4.2, sensitivity can now be adjusted directly from the Analog Watch View using the Digital Crown. The sensitivity indicator disappears after Crown input ends.
(SMD 4.2 is currently being rolled out via a phased release)

1. Overview

SMD is a watchOS app that uses the Apple Watch magnetic sensor to detect nearby magnetic field changes and notify you through haptic feedback. Its main operating screen is an analog clock display, allowing the app to remain discreet while still providing clear status cues.

Status meanings

• ON = baseline acquisition is complete, and magnetic detection and alerts are active
• OFF = stopped, initializing, or alerts are inactive
• -.-- = magnetic reference is inactive, so no magnetic reading is currently shown

Important: The X / Y / Z display is not the same thing as ON / OFF status. ON / OFF tells you whether detection is active. -.-- tells you that magnetic reference is currently inactive.

2. Important Notes

Recommended environment

• Apple Watch Series 10 or later is recommended

Important precautions

• Do not use magnetic watch bands.
• Very strong magnets may temporarily saturate the Apple Watch magnetic sensor.
• Extremely high sensitivity settings may also pick up environmental magnetic noise or geomagnetic variation.
• If detection becomes unstable after a strong reading, a short reset or re-set may help.

Note: Temporary sensor saturation caused by a strong magnet is a hardware-related effect, not necessarily an app malfunction.

3. Quick Start

1. Launch the app
2. Check the current mode
   • Gray second hand = Manual Mode
   • Red second hand = Motion Mode
3. Move between screens
   • Swipe left to open the Settings screen
   • Swipe right to return to the analog clock screen
4. Choose your mode
   • Long-press the analog clock screen, or
   • Use the mode buttons on the Settings screen
5. Activate the app
   • In Manual Mode, tap the analog clock screen or the X / Y / Z display area
   • In Motion Mode, raise your wrist for sensor start, then briefly hold still to set
6. Confirm ON / OFF
   • Extra long tick marks visible = ON
   • No extra long tick marks = OFF
7. Adjust sensitivity if needed
   • Open the Settings screen
   • Turn the Digital Crown

4. Screen Navigation

SMD uses two main screens:

• Analog Clock Screen – the main operating screen
• Settings Screen – status and adjustment screen

Navigation

• Swipe left from the analog clock screen to open Settings
• Swipe right from the Settings screen to return to the clock

Note: The Settings screen is not just a debug page. It is designed as a user-facing status screen that reflects the actual operating state of the app.

5. Analog Clock Screen

The analog clock screen is the primary operating screen of SMD.

Display rules

• Gray second hand = Manual Mode
• Red second hand = Motion Mode
• Extra long tick marks visible = ON
• No extra long tick marks = OFF

Main actions

• Tap
  • In Manual Mode: start or stop detection
  • In Motion Mode: tap behavior depends on current state
• Long press
  • Switch between Manual Mode and Motion Mode

6. Mode Switching

You can switch modes in either of the following ways:

• Long-press the analog clock screen
• Use the mode buttons on the Settings screen

Mode identification

• Gray second hand = Manual Mode
• Red second hand = Motion Mode

Tip: Both switching methods are valid. If one is less convenient in a given situation, use the other.

7. Manual Mode

Manual Mode is the standard mode for explicit start and stop control.

How to start

Tap either of the following:

• The analog clock screen
• The X / Y / Z display area on the Settings screen

What happens next

1. Tap is accepted
2. Baseline acquisition begins
3. ON becomes active after baseline acquisition is complete
4. Magnetic detection and alerts become active

How to stop

Tap the same location again:

• The analog clock screen, or
• The X / Y / Z display area on the Settings screen

Haptic feedback

You may feel haptic feedback at:

• Tap acceptance
• Baseline acquisition complete
• Stop

Note: If the time between tap acceptance and baseline completion is very short, those two haptic moments may feel almost the same.

Magnetic display behavior in Manual Mode

• When magnetic reference is active, X / Y / Z values are shown
• When Manual Mode is OFF, magnetic reference is inactive and the display shows -.--

8. Motion Mode

Motion Mode is a hands-free mode that uses wrist posture changes to control operation.

Basic flow

• Raise wrist = sensor start
• Briefly hold still = set
• Set complete = ON
• Lower wrist = sensor stop

What these terms mean

• sensor start is the user-facing term for the stage where wrist raise is accepted and magnetic reference begins
• set is the user-facing term for the brief stillness used to acquire the baseline
• sensor stop is the user-facing term for lowering the wrist and stopping magnetic reference and alerts

Important meaning of sensor stop

Important: In Motion Mode, sensor stop is a user-facing term. It does not necessarily mean that every internal process has fully stopped. Pose monitoring may still continue internally while waiting for the next wrist raise.

Key point

Raising the wrist does not mean the app is already ON. The app becomes ON only after set is complete and baseline acquisition has finished.

Haptic feedback

You may feel haptic feedback at:

• Wrist raise accepted
• Set complete
• Stop

9. Tap Actions in Motion Mode

Motion Mode also supports tap-based control.

When Motion Mode is OFF

If you tap either of the following while Motion Mode is OFF:

• The analog clock screen
• The X / Y / Z display area on the Settings screen

the app starts set immediately on the spot.

When Motion Mode is ON or processing

If you tap the same locations while Motion Mode is:

• ON, or
• In the middle of processing

the app turns OFF.

Why this matters

This makes Motion Mode easier to use when you cannot comfortably lower your wrist, such as while seated or in restricted posture.

Practical tip: Motion Mode is not wrist-only. Tap shortcuts are intentionally available so you can stop or restart quickly by hand when needed.

10. Settings Screen

The Settings screen provides status visibility and control functions.

Available information and controls

• ON / OFF status
• X / Y / Z magnetic values
• Mode switching
• Sensitivity adjustment
• Version information

Magnetic reading display rules

• When magnetic reference is active, real X / Y / Z values are shown
• When magnetic reference is inactive, the display shows -.--
• 0.00 is not used as a shutdown confirmation

Important: -.-- means magnetic reference is inactive or currently not being shown. It does not mean “zero magnetic field.”

11. Sensitivity Adjustment

Sensitivity is adjusted on the Settings screen.

How to adjust

• Open the Settings screen
• Turn the Digital Crown

Default value

• 60%

General guidance

• Increasing sensitivity makes weaker magnetic changes easier to detect
• If sensitivity is too high, environmental noise may also trigger unwanted reactions

Note: SMD4.0 later does not use a slider for sensitivity adjustment. The Digital Crown is the intended control method.

12. Polarity Detection

SMD automatically determines magnetic polarity based on magnetic field direction.

Features

• Supports use on either wrist
• Compensates for Digital Crown orientation
• Reduces the need for strict wear-direction setup just for polarity reading

This helps simplify practical use compared with devices that require more careful orientation management.

13. Single-Trigger Behavior

SMD uses a single-trigger notification design.

Behavior

• In most cases, one activation produces one alert
• A new alert requires the magnetic field to fall below the release threshold first

Purpose

• Prevent excessive repeated alerts
• Reduce unnecessary vibration during actual use
• Keep response behavior more stable and predictable

Note: If a strong magnetic influence remains nearby, or the surrounding magnetic environment is unstable, the next detection may not occur immediately.

14. Immediate Reset

If you want to reinitialize the current state quickly, use the following methods.

In Manual Mode

• Turn OFF
• Turn ON again

In Motion Mode

• Raise the wrist
• Briefly hold still
• Perform set again to reacquire the baseline

Refresh tip

If magnetic values remain unusually elevated after a detection, lightly moving the watch or gently rotating the forearm may help the sensor settle before the next use.

15. Full Shutdown

If you want to fully stop operation and avoid unnecessary battery use, use the following method:

1. Switch to Manual Mode
2. Turn detection OFF
3. Open the Settings screen
4. Confirm that the app shows OFF
5. Confirm that the X / Y / Z display shows -.--

16. Best Magnet Position

The easiest and most stable magnet position is usually:

• Close to the Apple Watch body
• Roughly level with the Digital Crown side
• Passing near the side of the watch rather than far above or below it

Practical guidance

Although response depends on sensor axes internally, the most practical approach is usually to keep the magnet at roughly the same height as the watch body.

Note: For optimal detection, the ideal position minimizes distance along all three axes (X, Y, and Z) relative to the watch body.

17. Troubleshooting

No response or weak response

• Reacquire the baseline
• Increase sensitivity slightly
• Move the magnet closer to the watch body
• Keep the magnet closer to the height of the watch body
• Check whether X / Y / Z values change on the Settings screen

Too sensitive or too many false triggers

• Reacquire the baseline
• Lower sensitivity
• Remove magnetic bands or magnetic accessories
• Avoid strong magnetic environments

Next detection is hard to trigger

• Lightly move the watch
• Gently roll or rotate the wrist
• Reinitialize with OFF / ON
• In Motion Mode, perform set again

Motion Mode does not behave as expected

• Make the wrist raise clearer
• Briefly hold still after sensor start
• Make up/down posture changes more distinct
• Check for nearby magnetic interference
• Use tap-based OFF / set if posture control is inconvenient

X / Y / Z shows -.--

• Magnetic reference is currently inactive
• This is normal when the app is not actively referencing magnetic values
• Check whether the current mode and state match what you intend

18. Pre-Use Checklist

Before practical use, confirm the following:

• The mode is what you intend
• The second hand color matches the intended mode
• Sensitivity is appropriate
• The watch is not using a magnetic band or magnetic accessory
• You understand how to turn OFF / ON or re-set quickly
• In Motion Mode, you understand the difference between:
  • sensor start
  • set
  • sensor stop
• ON / OFF status is clearly understood from the analog clock markers

19. Version Notes and Update Highlights

This manual reflects the SMD 4.1 behavior and terminology.

Main current points

• The analog clock screen is the main operating screen
• Swipe navigation is used between the analog clock screen and the Settings screen
• Manual Mode and Motion Mode are both supported
• ON becomes active only after baseline acquisition is complete
• The X / Y / Z display uses -.-- when magnetic reference is inactive
• Motion Mode supports tap-based OFF and on-the-spot set
• Sensitivity is adjusted with the Digital Crown
• Single-trigger behavior is used for more stable notification control

Recent update highlights

• Improved clarity of state-based UI behavior
• Reorganized the Settings screen to match real operating states
• Replaced old inactive-value behavior with -.--
• Added practical tap shortcuts in Motion Mode for OFF and re-set control
• Improved Frontmost operation stability
• Refined the overall flow so ON, OFF, magnetic reference, and user actions are easier to understand

20. Final Notes

SMD is easiest to use when you clearly separate three ideas:

• Mode — Manual Mode or Motion Mode
• Status — ON or OFF
• Magnetic reference state — numeric X / Y / Z values or -.--

Once those three states are understood, the app becomes much easier to operate reliably and consistently.

Recommended habit: For the clearest daily use, always confirm:

1. current mode
2. ON / OFF status
3. whether the magnetic display is active or showing -.--

Privacy policy

[Acquisition and use of user information]

This application does not acquire or use the user's personal information.

[Provision of user information to third parties]

This application will not provide the user's personal information to any third party.

[Contact]

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