VeloSwing strapped into a racket throat, its screen lit and its diffuser glowing violet

VeloSwing

A swing, read back as speed and light.

Beginners feel a swing. They cannot measure it.

VeloSwing turns it into a number and a colour.

Fits one hand.

A hand holding VeloSwing upright by its narrow lower end against a pale grey background, the screen lit and the diffuser glowing violet
116 × 88 mm
An open hand carrying the device flat on its fingers and palm, the whole device in view
26 mm thick
  1. VeloSwing by itself on a pale grey surface, seen from the front: a matte black shell in a wide V, the screen lit, the diffuser glowing violet
    Front
  2. The device standing on its narrow end, seen from the side: a slim slab made of two shells with one seam between them
    Side
  3. The device standing on its narrow end, seen from behind: a plain rear shell with a second diffuser glowing green
    Rear
88 × 116 × 26
mm, outside
≈ 45 g
two shells, as PLA, from CAD volume
5
printed pieces
128 × 32
pixel OLED, 26 × 11 mm window
8
addressable LEDs, WS2812B
100 Hz
6-axis motion sensor
Close view of the upper face: the screen reading about 45 km/h, two raised strap loops under it and the frosted diffuser glowing violet

Graphite, matte.

Shell
Two halves, one seam
Screen
Speed, stroke, count
Diffuser
Eight LEDs, one colour
Strap loops
Two straps to the throat
Button
Reset · 2 s kcal · 5 s sleep
Four devices standing side by side on a pale grey surface: red, off-white, pale blue and graphite
Four colourways
The device in the racket throat seen from three quarters, its shell curving with the frame, two pale straps across it
Two straps
A hand holding the racket at the throat on an indoor court, the device lit yellow after a slow swingThe same hand and racket, the device lit violet after a fast swing
Slow, yellow. Fast, violet.
VeloSwing pulled apart along one axis: front shell with its button, diffuser cap, display, the Nano 33 BLE with its USB lead, the carrier board with its buffer chip, the strip of eight lit LEDs, rear shellVeloSwing pulled apart top to bottom: front shell with its button, diffuser cap, display, the Nano 33 BLE with its USB lead, the carrier board with its buffer chip, the strip of eight lit LEDs, rear shell
  1. Front shell
  2. Diffuser cap
  3. OLED, 128 × 32
  4. Arduino Nano 33 BLE Rev2
  5. Carrier, 74AHCT125 buffer
  6. Button, tactile switch
  7. 8 WS2812B LEDs
  8. Rear shell

Five printed pieces, two identical caps.

Nine versions to one.

CAD capture of V1, same camera and scale as every other version
V1 Sep 6. First block-out, 2 mm hollow shell.
CAD capture of V2, same camera and scale as every other version
V2 Sep 10. Central light guide, side grip.
CAD capture of V3.1, same camera and scale as every other version
V3.1 Sep 14. LED optics, button, 1.6 mm boards.
CAD capture of V3.2, same camera and scale as every other version
V3.2 Sep 17. Curved to the throat, fitted from my own photos.
CAD capture of V3.3, same camera and scale as every other version
V3.3 Sep 20. Thin hollow triangular diffuser.
CAD capture of V3.4, same camera and scale as every other version
V3.4 Sep 20. Front facets, three rear ridges.
CAD capture of V3.5, same camera and scale as every other version
V3.5 Sep 22. Flat shell, strap mounts, display opening.
CAD capture of V3.5.1, same camera and scale as every other version
V3.5.1 Sep 23. Diffuser cut down to 22.9 × 18.1 mm.
CAD capture of V3.5.2, same camera and scale as every other version
V3.5.2 Sep 25. Two identical closed caps.
A hand and racket meeting a tennis ball against a pale curtain, VeloSwing lit violet in the racket throat
A racket lying on a blue indoor court beside a white line and a tennis ball, VeloSwing lit violet in its throat

Every swing, answered.

Slow, mid, fast, serve, then a 2 s hold.

300+ swings on a real court.

  1. [0381] Forehand 94.76% 34.0
  2. [0382] Forehand 91.29% 43.0
  3. [0383] Forehand 91.26% 28.0
  4. [0384] Forehand 96.66% 33.0
  5. [0391] Forehand 88.32% 37.0
  6. [0392] Backhand 94.02% 45.0
  7. [0393] Backhand 98.10% 37.0
  8. [0394] Backhand 92.75% 38.0

Three strokes, three shapes.

−0.45 sImpact+0.45 s

Named at 0.70, or not at all.

0.62

Unknown. Speed counts, the stroke does not.

00.701
544
windows, open dataset
87.68%
correct, all windows

Every wire, redrawn.

NANO 33 BLE REV2NINA-B306RSTzyxVINGNDRSTVUSBA7A6A5A4A3A2A1A0AREF3V3D13TX1RX0RSTGNDD2D3D4D5D6D7D8D9D10D11D12VUSBSDASCLVCCGNDSN74AHCT125N1413121110981234567104100 nF330 Ω10 kΩButton+5VDINGNDWS2812B × 8DOUT NCUSB-C to Micro-USB NANO 33BLE REV2NINA-B306RSTzyxVINGNDRSTVUSBA7A6A5A4A3A2A1A0AREF3V3D13TX1RX0RSTGNDD2D3D4D5D6D7D8D9D10D11D12VUSBSDASCLVCCGNDSN74AHCT125N1413121110981234567104100 nF330 Ω10 kΩButton+5VDINGNDWS2812B × 8DOUTNCUSB-C toMicro-USB
  • Joined
  • Crossing, not joined
  • No connection
Wiring, net by net
5VNano VUSB, AHCT 14, 13, 10, 4, 100 nF to pin 14, Strip +5V
3V3Nano 3V3, OLED VCC
GNDNano GND, OLED GND, AHCT 1, 5, 7, 9, 12, 100 nF to pin 7, 10 kΩ low side, Button contact, Strip GND
SDANano A4, OLED SDA
SCLNano A5, OLED SCL
D2 BUTTONNano D2, Button contact
D6 DATANano D6, AHCT 2 (1A), 10 kΩ to GND
DINAHCT 3 (1Y), 330 Ω in series, Strip DIN
Not connectedAHCT 6, 8, 11. Strip DOUT. Nano VIN.

Process

  1. Flowchart: the emitter column on the left, the sensor column on the right, from ready to sleep
  2. A CAD section through the shell: the board, the display and the light guide each in a pocket of their own
  3. A CAD cutaway of the same shell seen along its edge, the diffuser in the middle of the face
  4. A bench with a laptop showing the wiring plan, a soldering kit and the board wired up
  5. The Arduino Nano 33 BLE Rev2 board on a white desk
  6. An SN74AHCT125N chip held on two fingertips
  7. The Nano on a white desk with the first jumper wires and a resistor soldered in line
  8. A printed shell on a wood floor, wired by hand to the Nano and a loop of LED strip, the display lit
  9. The printed device strapped into a racket throat, its screen on and its diffuser lit yellow
  10. The device in the racket throat in a dim room, the screen showing estimated calories and the diffuser lit violet
A racket leaning against a wooden courtside bench on an empty indoor court, the device in its throat lit violet

No phone. No internet. Only light.

Family of Form

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