I built this to automate the plotting of camshaft profiles.

30 years ago I sat with a piece of graph paper, a dial indicator, and a degree wheel for several days plotting camshaft profiles for a race engine. After gaining some experience with stepper motors and microcontrollers I decided to make a tool to do this automatically.

The design is my own, there are a few existing variations of Arduino camshaft measuring tools on the web and I did get inspiration from several of these as well as using modified code from GitHub and and other sources.

I posted a video of this in operation.

The Hidden Dial Indicator Protocol

Building a race engine requires measuring cams down to the ten-thousandth of an inch. A standard micrometer can't map a sweeping curve. The Arduino Camshaft Measurement Tool mathematically intercepts real-time displacement telemetry from a digital dial indicator, plotting an infinitesimally precise, 360-degree lift graph directly onto your laptop!

A cheap $25 digital dial indicator looks completely standalone, but hidden under a plastic flap are 4 microscopic metal pads (VCC, GND, CLK, DATA).

1. The Logic Level Trap: These generic indicators run on a tiny 1.5V button cell battery. The Arduino is 5V. If you plug them together, the Arduino will instantly obliterate the dial indicator.
2. You must utilize an NPN Transistor Level Shifter or a dedicated 4-channel 3.3V-to-5V logic level converter circuit.
3. The data does not stream; it bursts. The dial is the "Master." It sends a clock pulse (CLK) every few milliseconds, followed by 24 bits of pure, raw binary (DATA).

Intercepting and Plotting the 24-Bit String

The Arduino must listen passively and act as a high-speed data catcher.

• attachInterrupt(digitalPinToInterrupt(CLOCK_PIN), readBit, FALLING);
• Every time the clock dips, the Arduino instantly reads the DATA pin (1 or 0).
• It shifts this data mathematically into a massive long integer representing inches or millimeters.
• The Graphing Execution: The Arduino is physically connected to a Rotary Encoder attached to the camshaft's spinning centerline.
• At 0 degrees, the lift is 0.0000".
• At 90 degrees, the lift is 0.4560".
• The Arduino serializes BOTH numbers (90, 0.4560) into the Serial Monitor, allowing the PC to literally plot the mechanical "profile curve" of the massive metal lobe!

Precision Machining Needs

• Arduino Uno/Nano (Sufficient for capturing standard dial protocols).
• A Harbor Freight or generic Digital Dial Indicator (With the secret access port exposed).
• A 3.3V to 5V Bi-Directional Logic Level Converter Module (Non-negotiable; you will fry the tool without it!).
• High Resolution Optical Rotary Encoder (To track camshaft rotation degrees).
• A heavy, magnetic metal measuring stand (Absolute physical rigidity is required; any vibration destroys the micro-level readings).