Markus’ Blog

Recently I decided to buy a new soldering station, mostly because I wanted to have more power for larger solderings. Being quite happy with my old one from Ersa, I decided to go for the current model RDS 80. It seemed to have a very good price/performance ratio, and I was pretty sure to get an upgrade in all regards.

So I was very disappointed when I realized that the cable to the soldering iron RT 80 is made from PVC. It’s not heat-resistant, quite heavy and most of all its flexibility is not much better than that of a steel cable … How can Ersa risk their good reputation by installing a cable as bad as this one? Especially when the former products had very good silicone cables …

Searching the web, I found many people complaining about that cable but no report of someone who had successfully replaced it.
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A while ago I got my hands on some old split-flap displays from a train station. Yesterday I finished driver circuits for 8 of the segments. It was only just in time to also quickly implement a clock algorithm for an extraordinary clock to display the turn of the year. Don’t miss the movie at the end of this posting.

The original driver circuits consisted of a Zilog processor, an EEPROM, an optocouppler for driving the 42V synchronous motor, transistors, two reflective IR-sensors for segment position and a few passive components. Since I do not have any information about the original interface and protocol, I decided to implement my own driver circuit and directly connect to the sensors and motor.

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Until yesterday I was not happy with lighting when drilling PCBs: It was either too dark or there were cast shadows (of my fingers or the drill itself). So I had to concentrate hard on drilling all the holes correctly centered where they belong.

But now my problem is solved: I built a ring of 20 sunny-white SMD LEDs. It can easily be attached to my multi-tool and – as you can see on the photos – it always assures perfect light for drilling.
The first version last week was built with 10 LEDs only. I was not happy with the result then: the cast shadows of the drill were still distracting.

The LEDs are driven with constant-current of 20mA. 2 x 10 LEDs are connected in series. I built the power-supply some time ago for a different project. I plan to report on this 70-LEDs-Macro-Ringlight project (along with its power supply) in this blog soon, so I won’t go into more details now.

You can download the KiCad project files and the board layout as PDF. The layout should fit various LED package sizes, but works best with 3020. The board has a diameter of 46mm, which I consider a good compromise of good illumination and small size.

RGB 7-segment display

7-segment LEDs are available in red, green, yellow and blue (maybe even in white?). There don’t seem to be any in RGB though, so if you want to dynamically use different colors in your project you either have to use multiple devices or use a different technology.

So this seemed like an opportunity for a nice DIY project: Why not take an existing 7-segment display, remove the original LEDs and add some RGB ones? (continue reading…)