Photons, Electrons, and Dirt

In this post, I disassemble a 747 fuel quantity indicator and reverse engineer the electromechanical parts of the indicator. I then apply hardware and software techniques used on previous projects to build a PID controller for a control loop consisting of the AC servo motor and feedback potentiometer in the indicator. This control loop is used to position the dial and counter on the face of the instrument to values entered into a serial terminal.

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In this project, I use a Python script and an updated version of my digital-to-synchro project to replay my mountain bike climbs and descents at 60x real time speed on a vintage aircraft altitude indicator. The updated D2S converter fits on a single board and uses three Microchip MCP4802 DACs and three TI OPA548 power operational amplifiers to produce high-power 400 Hz AC waveforms to power and control the servo loop in the altitude indicator.

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In this post, I take a look at a vintage Kollsman aircraft electric tachometer indicator. I start by disassembling the tachometer to determine how it works then build up a variable-frequency power supply to power and test the indicator. Once the power supply and indicator are working, I measure the speed of the motor inside the indicator to determine the number of poles on the motor. Finally, I repurpose this indicator as a unique CPU performance meter.

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That’s a lot of hardware to rotate the synchro receiver on the right!

In the last project, I built a synchro-to-digital converter to display a synchro’s shaft angle on a small OLED display. In this project, I reverse the process and build a digital-to-synchro converter that sets a synchro’s shaft to the angle entered into a terminal window.

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Can this hardware determine the angle of the fine altitude’s synchro resolver accurately? Read on to find out!

This project uses modern data acquisition hardware to track the shaft angle of a synchro transmitter as the shaft is turned through various angles. How difficult could it be to get the absolute angle of a position sensor from the 1980’s that was originally developed during the WWII era into a modern computer? Turns out, it’s more difficult than it seems, and for most hobbyist applications, more difficult than it’s worth. Read on to find out more.

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The landing gear and flaps indicator, control board stack, and C# .NET Windows Forms app running on the Surface in the background. Everything set for smooth and level flight!

In this project, I convert a WW2-era landing gear and flaps indicator into a USB peripheral using a Raspberry Pi Pico development board and eight channels of programmable current sources. This project is similar to my WW2-era engine cowl flaps indicator project but the gear and flaps indicator requires a different control strategy.

This post starts with a look at the gear and flaps indicator, its theory of operation including its differences from the engine cowl flaps indicator, and some ideas to control it with modern electronics. The post then covers the design of the boards, the software for the Pico dev board, and a Visual Studio C# .NET Windows Forms app for controlling the indicators from a PC.

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General Electric 8DJ4PBV quad engine cowling indicator with PIC16F1459 and MCP41HV31-502 board to its right. A Microsoft Surface in the background is controlling the indicators via USB.

In this project, I convert a WW2-era engine cowl flaps indicator into a USB peripheral using a Microchip PIC16F1459 microcontroller and four Microchip MCP41HV31-502 digital potentiometers. This project is reminiscent of my USB analog panel meters project but the drive circuitry is significantly less complex. This post starts with a look at the engine cowl indicator, it’s theory of operation, and some ideas to control it using modern electronics. The post then covers the design of the board, the software for the microcontroller, and a Visual Studio C# .NET Windows Forms app for controlling the indicators from a PC.

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The complete DIP switch USB stick plugged into my Surface Pro tablet.

Tired of editing XML and JSON files to store configuration settings for your hardware or software? What if we could go back to using DIP switches for configuration settings? Well, with the DIP switch USB stick, you can! No more telling relatives how to fire up vim or emacs and edit a file during those late-night family tech support calls. Yeah, just flip the red switch!

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I first saw a Scramblepad on the door of an office building I worked at while in high school in the late ’80s. I always wanted to own one or to make my own based on seven-segment LED displays but had trouble finding a suitable, transparent touchpad I could use for the buttons. I eventually gave up on building my own.

Luckily I found a few Scramblepads up for sale recently and decided to buy one to see if I could do anything useful with it. With a bit of work, I reverse engineered the communication protocol and can now use my Scramblepad with my own simplified homebrew door controller. Read on to learn more about the hardware, the communications protocol, and building a homebrew Scramblepad compatible door controller.

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