[Chris Doble] has high ambitions: he’s making his own scanning-electron microscope, and as the first step he’s built a high-vacuum system. This required its own controller to manage the various electronics involved in the system, which he’s documented and open-sourced.
The vacuum system itself starts with a rotary-vane roughing pump, which can bring a chamber down from atmospheric pressure to about 10-3 millibar. This is still too high a pressure, so the second stage is a turbomolecular high-vacuum pump, which can operate from 18 millibar down to 10-7 millibar. To protect the turbomolecular pump in case the roughing pump suddenly stops, it includes an anti-suckback valve. Connected to these pumps is a pressure gauge which uses a pair of sensors to sense the entire pressure range. All this setup worked well, but the turbomolecular pump and the pressure sensor each used their own interfaces, while [Chris] wanted a single interface for the eventual microscope.
[Chris] therefore designed his own controller based on the Raspberry Pi Pico 2, with firmware written in Rust. The pressure gauge uses an RS-232 interface, which he connected to the Pico’s UART pins using an RS-232 level shifter, with a null modem to swap over the transmitting and receiving pins. The turbomolecular pump used an RS-485 interface, which required a converter circuit and some level-shifting resistors. A custom PCB and 3D-printed case hold the final circuit, which provides a host computer with a single USB interface. When [Chris] tested the controller, the vacuum chamber reached a pressure of 10-6 millibar, and was still slowly falling when he ended the test.
This isn’t the first vacuum chamber controller we’ve seen. Of course, this assumes that the pressure gauge already has a controller; if not, we’ve also covered one of those. To see the inspiration for [Chris]’s project, check out [Ben Krasnow]’s scanning-electron microscope.



Pallets are a wonderful way to package goods and move them around, but especially the wooden ones have a very finite lifespan. This means that many of them are discarded every day, even though there is still good wood on them. Even if it’s not the highest quality wood, you can still use it for some nice wooden items, like the tea tray that [GR Woodworking] 


