HP XY Recorder Restoration: Raspberry Pi Retrofit
Breathe new life into vintage technology! This article details the impressive HP X-Y recorder restoration, transforming a classic Hewlett-Packard plotter into a modern marvel. Using a Raspberry Pi retrofit, the project bridges the gap between analog recorders and digital outputs. Learn how the original recorder was adapted to receive modern digital signals, overcoming challenges like a non-functional x-axis by consulting schematics and using practical restoration methods for the axis and pen lifter. The project incorporates digital-to-analog converters (DACs), a voltage divider, and an amplifier. CircuitPython code generates curves, with future plans to translate HP-GL commands for vector graphics. For more tech news, visit News Directory 3. Discover what’s next as this restored HP plotter finds a new purpose!
Restoring a Vintage HP X-Y Recorder Plotter
A vintage Hewlett-Packard X-Y recorder, rescued from an attic, has been given new life as a functional plotter. The project highlights the differences between X-Y recorders, designed for real-time analog data charting, and plotters, which render digital computer outputs.
The key distinction lies in their control mechanisms: plotters use digital commands, while recorders rely on analog voltage inputs. The challenge was to adapt the HP recorder to accept modern digital signals.
After overcoming logistical hurdles, including shipping the device from Ireland, the restorer faced a non-functional x-axis. Troubleshooting involved consulting the recorder’s manual, obtained from eBay, which provided detailed schematics and repair instructions.
The manual revealed the purpose of previously spotted resistors. Instrument oil and silicone grease revitalized the x-axis and pen lifter. Testing with a variable power supply steadfast the recorder’s input ranges: 0 to 1 volt for the y-axis and 0 to 5 volts for the x-axis, achieving approximately 0.2 millimeter accuracy.
An interface was built using two Adafruit MCP4725 breakout boards, 12-bit digital-to-analog converters controlled via an I2C serial connection. These were connected to a Raspberry pi Model B+.
The DACs’ output, ranging from 0 to 3.3 volts, was scaled using a voltage divider for the y-axis (0 to 1 V) and an LMC6484 amplifier for the x-axis (0 to 4.8 V). A 74LS08 AND gate IC shifted the pen control signal from 3.3 to 5 volts.
Code was written on the Pi, using parametric equations in CircuitPython, to generate geometric curves. Future plans include enabling the Pi to translate HP-GL commands,allowing the plotting of vector graphics from software like Inkscape. The restored vintage HP X-Y recorder plotter is now fully operational.