Markus’ Blog

A few months ago I stumbled across the very first Reverse GeoCache project by Mikal Hart. I was fascinated by the idea and decided to build one of my own.

What is a Reverse GeoCache?

Like any other GeoCache it is a box that is linked to a certain coordinate on earth. The challenge is to find this coordinate, in order to access the contents of the box.

Other than with ordinary GeoCaches you do not need to find the box at the target coordinate: You will already have it when the puzzle starts. But the box is closed and it will only open when you are near the target coordinate. In order to find the coordinate, the box has a button: When you press the button, the internal GPS receiver will detect the current location and the distance to the target will be displayed. Of course the number of trials is limited. If you press the button too often, the box will be sealed forever.

(continue reading…)

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.

These days some of the coolest ICs are only available in SMD packages, e.g.

• the fast SSP FRAM FM25256B-G and
• the famous USB to RS232 converter chip FT-232.

For me as a hobbyist that’s a problem, because I don’t have the equipment to etch PCBs, and I want to develop my circuits on breadboards.

Fortunately there are some SMD adapter boards available. So yesterday I soldered two SSOP-28 chips on adapter boards. Soldering with a pin distance of 0.65mm is a challenging task – and for me it’s definitely the limit. Using good and thin solder (0.5mm) and a soldering rod with a very thin tip are two of the most important premises. Another one is a tremble-free hand.

What I do not like about the SSOP-28 adapters though, is that there are two rows of pins on each side of the chip. This is not good for breadboards. But hey: it’s still lots better than SMD.

For SOIC-8 however, I am very happy that I found better adapter boards. When assembled, the SMD chip can be used like an ordinary DIL-8. The adapter boards are available in Germany from W2micro. They are cheap, and they come complete with double sided SIL sockets and even with SMD capacitors. Thumbs up for this solution. The guys from W2micro really saved my day.

Do  you know about other great SMD solutions? Let me know in the comments.

I am still not sure what project to use my rgb 7-segment display for. There were some very interesting ideas posted to the Hackaday forum. I like matthiasrs idea most: A 2-digit clock, using the red LEDs for hours, the green ones for minutes and the blue ones for seconds.

In order to get a better idea, rather then implementing it in hardware I wrote a little simulation as Java applet. Have a look and see how hard or easy it is to identify the time

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…)

Today I started my new blog.  I would like to post about my DIY projects, as well as about my software project JavE.