After finally getting my Cetus3D MkII 3D-printer I was eager to start to print. When I started through the steps to calibrate the printer by adjusting the build plate height, but the print head/nozzle refused to get close enough to the build plate to finish the calibration! The cables on the motor came in contact with the chassis of the printer! So the injector was 5mm from the build plate and couldn’t get any closer by increasing the step values. But there is an easy fix for the problem.
ITEAD contacted me about testing some new equipment and write an unbiased blog post about it. I usually reject all such offers, but this one worked for me. Why? Well, all the stuff they offered was on my shopping list anyway! And my home is quite literally chock full of Sonoff relays, lamps, etc.
So the first thing I started to play with was the SONOFF RF BRIDGE 433. The bridge makes it possible to control switches, doorbells, curtain openers, etc. that uses 433MHz communication frequency. I’m not interested in using the original firmware because I prefer to do my home automation setup in Node-RED. Here’s how it works.
Over the years I’ve been reading about a way of restoring old computers and other equipment where the plastic has turned yellow and how some bright guys developed a method called Retr0bright to reverse the process.
The reason for the yellowing of the plastic is the flame retardant bromide that is infused in the plastic to prevent fires. When exposed to UV-light, the bromide comes to the surface of the ABS plastic, and the yellowing begins.
Unfortunately, even after treating the item with Retr0bright, the yellowing returns after 3-4 years, looking worse than your grandfather’s underwear.
Here’s my attempt at a fix to that problem.
Part 1 – Checking the Velocity Factor of the Coax Cable
I have a homebuilt Collinear Antenna on one of my two ADS-B receivers. It’s an eight element antenna, built without any real effort of making sure that all the elements where the right length. So it’s about time to try to do it properly. The easy way is to get Flightaware’s great ADS-B antenna and filter, but it’s fun to build your own as well.
To build a good antenna, you would preferably use a Vector Network Analyzer so you can do proper measurements of your antenna design. With it you can quickly check stuff like SWR and optimize the impedance of the antenna at the frequency it’s intended to be used. In my case 1090MHz for ADS-B. But if you don’t have the money to spend, you have to improvise. I’m going to build a 12 element Collinear Antenna out of cheap RG-58 coax cable. But to calculate the right length of each element, we need to know the Velocity Factor, or the signal speed through the cable compared to light traveling in a vacuum. So let’s do the measurements.
If you are on the lookout for a sub $30 Multimeter (or $15 on eBay) for working with low voltages, the best one right now in my opinion is the cute and tiny Aneng AN8008 TrueRMS Multimeter or the newer model, the Aneng AN8009 with NCV and temperature measurement. They have a lot of functions and can measure µA current, and both are a 9999-count meter. The continuity tester is reasonably fast, but there is one little problem that bothered me. It takes 5 to 10 seconds for it to settle on a correct voltage reading. When it finally ends, it’s spot on, but the waiting is annoying. But fortunately, there is a simple fix for this problem.