Older articles (11/27)

1. Creating a nomogram with Python and Postscript

   At work I needed a suitable way to check the calibration of gelcoat spray equipment. Gelcoat requires an initiator (often called “catalyst”) in the form of a peroxide to cure. The peroxide/gelcoat ratio is important, so it is checked regularly by spraying the separate components into suitable containers and weighing them.

   For those familiar with gelcoat spraying, this is not a system with coupled gelcoat and peroxide pumps. But rather an external mixing spray gun where the peroxide is simply fed from a pressurized container to the spray gun.

   Since we’re handling resins, solvents and peroxide, protective equipment including gloves is a must. That makes it cumbersome to whip out a smartphone to use it as a calculator to check the ratio. Since you don’t want to get gelcoat or peroxide on your expensive phone, you have to take off your gloves to handle it. This would have to be repeated several times.

   So I decided to make a diagram where one could relatively easy read off the peroxide percentage given the quantities of both components. This can be printed and laminated between plastic to make it resistant against stains.

   The whole thing can be found in a github repo.

2. Disable firefox DNS

   Some spam, tracking and ad servers are blocked at the DNS level on my network. For me it is therefore undesirable that programs use their own DNS.

3. Building ports with local modifications

   Sometimes I have to build ports with local modifications. This can be for testing purposes, before submitting a PR or for improvements that only I consider important.

4. Drawing with PostScript

   PostScript (in the form of ghostscript) was for me the first way to generate vector graphics outside of a CAD program. I have several hundreds of figures written in PostScript for inclusion in e.g. LaTeX document.

   Later I’ve started using other programs and modules like asymptote and TikZ. But there are cases (especially if you want a small file) where directly drawing in PostScript is still the best way to go.

   When the book Mathematical Illustrations was mentioned on hacker news, this re-kindled my interest in PostScript. And I learned some valuable lessons from it.

5. TeXLive 2018 update

   Today I updated my TeXLive install to 2018. Although the install went fine, there was a problem with the binaries.

   Both asymptote and xetex were linked to different versions of some libraries than those that are supplied by ports. So I had to rebuild them.

6. Using the FT232 with Python

   In this article I will try to document how to with with the FT232H using Python on FreeBSD. I will be using the Adafruit FT232H breakout board.

   Note that since I’m using FreeBSD, the library provided by FTDI doesn’t work. However, the library provided by Adafruit was written for Python 2, and doesn’t work with Python 3. I tried tinkering with it a bit to get it to work with Python 3, but that did not work out. In the end, I went with pyftdi since it doesn’t require a native library and it just works.

7. Measuring particulate matter with the PMS5003

   This article details how I used the Plantower PMS5003 particulate matter (“PM”) sensor on a PC or laptop, using an FT232H breakout board to make the connection.

8. Storing and graphing time-based data

   In this article we will look into the best way to store time-based data and use it with gnuplot.

9. Yes, please: #DeleteFacebook. But don’t leave it at that.

   Cut facebook out of your life altogether.

10. Video manipulation with ffmpeg

    Serveral useful recipes for manipulation video with ffmpeg.