Vacuum is necessary for all kinds of scientific and practical applications. When doing science, vacuum is useful for everything from boiling at lower temperatures to avoiding contamination. On the practical side, a vacuum chamber can help remove bubbles from silicone molds or even facilitate exotic techniques like vacuum metal deposition. But to measure your vacuum, you’re going to need a vacuum gauge or sensor. Vacuum sensors are relatively affordable, but Advanced Tinkering found that vacuum gauge controllers are not. To save thousands of dollars, he built his own DIY vacuum gauge controller.
There are different scales for measuring vacuum, but ultimately they all indicate the pressure inside a vacuum chamber. That can be anywhere from 1 bar (about the atmospheric pressure on Earth at sea level) down to 0 bar (a perfect vacuum with no gas pressure whatsoever). You’re never going to achieve a perfect vacuum — even outer space doesn’t qualify. That means that you’ll want to know how close you’re getting to 0 bar. Vacuum gauges, like those Advanced Tinkering purchased, output an analog voltage proportional to the pressure level. For some reason, vacuum gauge controllers are very expensive. But all they really need to do is monitor that analog voltage output, so Advanced Tinkering built his own.
In reality, this task was more complicated than simply measuring the analog voltage. These vacuum gauges were designed for use with specific controllers and utilize a proprietary communications protocol. That carries additional information, such as an identifier for each gauge and its status. Fortunately, data on the specifics of that communication is available. Advanced Tinkering was able to accept and decipher the data using an Arduino Nano board, a multiplexer, and an ADC (analog-to-digital converter). After some troubleshooting headaches, Advanced Tinkering was able to retrieve the complete data from the vacuum gauges.
This DIY controller can handle three individual vacuum gauges, though it would certainly be possible to expand that. Each gauge gets its own OLED screen, which shows the status and incoming measurements (in millibars). The status, which is what made this more complex than measuring a single analog voltage signal, tells the controller if a gauge is receiving power, if it is degassing, and so on. Push buttons let the user activate a particular vacuum gauge and the pressure reading will show up on the corresponding OLED screen. Everything fits into a tidy 3D-printed enclosure that looks at home on a workbench.