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Finished build

LED speedometer gauge

A round gauge-face circuit board I designed in Altium Designer at Specialized Solutions, after doing the wrench for the 2018 DEF CON Car Hacking Village badge. A radial array of hundreds of small SMD LEDs sweeps around a printed 10 to 100 speed scale, driven by two microcontrollers and six 74HC595 shift registers, powered over micro-USB. The boards were fabricated as a four-up panel, and I assembled them. It was not an official Car Hacking Village badge: I designed it, the owner of Specialized Solutions liked it, and we built a small run, I assembled them, and we sold about 20 at DEF CON 2019. Its SDK appears in the public 2019 Car Hacking Village repo as the “gauge”.

Public repo on GitHub ↗

  • Altium Designer
  • 4-layer: top, solid ground plane, power, bottom
  • Round board, hang hole
  • Hundreds of SMD LEDs
  • NXP microcontroller driving the LEDs
  • STM32F205 handling CAN to the car's OBD port
  • Six 74HC595 shift registers
  • Micro-USB power
  • Fabricated 4-up panel
  • ~20 sold at DEF CON 2019

Running

Assembled boards

Assembled white speedometer board with LEDs, microcontrollers, buttons and a micro-USB connector
AssembledOne assembled board: two microcontrollers, six 74HC595s, two buttons, micro-USB and the edge pads.
Panel of four assembled speedometer boards
PanelAll four boards on the panel, assembled.
Two boards on a panel partly populated with parts, showing assembly in progress
AssemblyAssembly in progress on the panel.
Close-up of the LED array and printed speed numbers on the board
DetailClose-up of the LED array and the printed scale.

Fabricated boards

Panel of four bare white speedometer PCBs with the numbers 10 to 100 printed around the dial
BoardsBare boards as received from fabrication.

Design

3D render of the speedometer board in blue with components and a connector below
3D render3D view of the board with its components.
Component footprints in the centre of the board, shown in pink and yellow
PlacementFootprint and placement layout: the central ICs and the ring of LEDs.
Close-up of the upper left of the board showing all layers
LayoutClose-up with all layers on.
Fully routed board with all layers displayed
RoutingRouted board, all layers.
Top copper layer in red
LayerTop layer.
Bottom copper layer in blue
LayerBottom layer.
Inner power layer with short LED traces in light blue
LayerInner power layer, with short traces for the LEDs.
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