Today my kids impressed me by repurposing/hacking/misusing the toilet-occupied-light to send (morse-like) signals across a railway car. Their fingers were thin enough to press the micro-switches in the doors which normally would signal a locked door (i.e. occupied toilet). Not sure if someone noticed the strangely flashing lights… 😀
Last weekend I had to replace a 230 V fan (120 mm), a Sunon DP200A, that ‘smelled’ strange and also made strange noises. Better safe than sorry…
Well: I ordered a slightly less powerful Sunon DP201A (at Reichelt Elektronik) to replace the possibly dangerous fan. Although they look similar their connectors are completely different. So I’m now wondering if the first one (the DP200A) wasn’t an original fan at all…?
A few days ago I was able to get my fingers on, and under, an infrared camera. I had already heard before that the thermal signature of fingerprints is visible for quite some time — but what surprised me was that we were still able to see them for over a minute…
This short post is to document Sharp PC ROMs I’ve come across so far. I’ve used MD5 and SHA1 checksums to allow their comparison. It would be nice if you could notify me of any ROMs out there that do not match the ones documented here… In an earlier post I’ve described a simple way to dump the ROMs.
- Sharp CE-150
Memory Area A000-BFFF (8 kB)
- Sharp PC-1500
Memory Area C000-FFFF (16 kB)
- Sharp PC-1500 / Sharp PC-1500A
Serial 20011xxx (Sharp PC-1500)
Serial 31070xxx – 57012xxx (Sharp PC-1500A)
Memory Area C000-FFFF (16kB)
Feel free to contact me and provide me with ROM file I do not (yet) have in my collection. I will also try to make the ROM files available in the next weeks.
Half a year ago I’ve started to use KiCad for new PCB designs I’m working on. I already wanted to try out KiCad for quite some time. Its release 4.0 and the latest changes in EagleCAD (annoying ads and recently being bought by Autodesk) were enough pressure to switch. And what should I say: after dealing with the rather unhandy library management and some cryptic error messages I really now enjoy KiCads workflow.
This post is about my experience with the transition to KiCad as my new PCB designer. It is based on the newest version 4.0 of KiCad and its daily builds via the respective Ubuntu PPAs. Continue reading
I know I’m sounding like a moralizer and the suggestion should be a no-brainer. But the flood in Simbach a few days ago once again showed me how important backups are – and how even more important it is to keep them in separate physical locations. I’ve helped friends to remove mud from CD/DVD backups. I’ve extracted hard drives from computers and USB cases, removed mud and water as best as I could. The drives are currently drying at 40°C in an oven. Hopefully they will be readable again…
Oh, I nearly forgot: I’m also currently failing at making backups on a regular basis and even more: my backups are all in one place. 🙁
Yesterday evening I spontaneously made a photo of Jupiter with my Canon DSLR, a (300 mm) zoom lens, and a tripod. 🙂 I was really surprised that I was able to identify the four Galilean moons Europa, Io, Ganymed, and Callisto.
I did not expect much as I made the shot from my balcony with room and street lights on. Here in Munich we have a lot of light pollution. At first I thought the small spots were lens flares. Also chromatic aberration is pretty visible due to the manual focus, but I’m still proud of the photo because I did not expect anything special: I first had to compare it with the software-rendered constellation of the moons around the time the photo was taken (see below) to be sure.
Exactly 30 years ago a great disaster struck the region of Chernobyl: a nuclear accident occurred that released a large quantity of radioactive particles into the atmosphere. And it is only five years ago that, with the Fukushima Daiichi nuclear disaster, a second similar catastrophic event has taken place.
These anniversaries did not directly let me build a PIN Photodiode based Geiger Counter, it is more or less a coincidence. The main drive to build such a device was my curiosity and (please forgive me) a fascinating green glow I’ve seen on various fluorescent Uranium minerals under UV light. But in this context it should not be forgotten that at present there still is a significant increase in background radiation in some regions and some agricultural products due to these events.
There are lots of descriptions of how to build such a device; even cheap commercial products (e.g. the Smart Geiger) use such a design. Especially two sites caught my attention: OpenGeiger.de and Das Gammastrahlen-Mikrofon (German). The design I’ve chosen is based on these sources but I’ve begun to further modify it. In this post I’m showing the design I’ve started with. It mainly relies on two BPW34 (Vishay Datasheet) photodiodes connected in parallel, and two transistors to amplify the voltage fluctuations of beta and/or gamma rays striking the diodes. A 9 Volt battery was added to increase the pulse height.
The common approach to protect the photodiodes from light is to use one layer of tin foil and connect it to ground. This should also protect the circuit against electromagnetic radiation. I’ve started with something different and dipped the diodes three times into liquid rubber (Plasti Dip). My hope was to at least allow some beta particles to reach the semiconductor material.
So far I’ve tested the basic design shown above and had mostly noise on my microphone input. I’d say that sporadic crackling has more to do with the 1 hour hacked together design than beta or gamma rays. The liquid rubber seems to block of light, but the simple design is sensitive to electromagnetic radiation. Waving your hand or even movements in about 1 m distance is visible in the sound profile. An additional tin foil shield connected to ground did not change the noise profile, although the EMR influence was reduced. I’ve tested it with two different sound cards (microphone inputs).
I’m currently redesigning the whole approach and expect better results. So stay tuned…
To make it clear from the beginning: this is a (possibly) destructive method of reading ROM chips. The process of extracting and possibly a resoldering of the memory chip might fail. In my case I’ve tested it on two Sharp CE-150 PCBs I’ve declared to be spare parts. It is only a proof of concept as there are simpler non-destructive ways of ROM extraction on a Sharp PC. I was just curious and so I’m describing my experiences.
Well… At first I did not want to desolder the ROMs: I started with the intention to use a set of probes attached to the individual pins of the chip to read the content of the Sharp PC / CE ROM chips. This did not work due to the narrow leg distance of the QFP chips (0.8 mm).
Desoldering QFP chips can be done rather quickly with a hot air gun. At least that’s the most comfortable way I know of. I usually add some flux and in some cases larger quantities of leaded solder. The latter decreases the melting point and speeds up the process. I don’t care about solder joints as the chips and the pads can easily be cleaned after the removal. Excessive amounts of solder can be removed with flux and a clean soldering iron tip.
This was a little test out of curiosity… I’m currently playing around with an amplifier circuit for the Sharp CE-150 audio output (CMT-OUT) and wanted to see if the signal I’m getting is already distorted when leaving my Sharp PC, or if my circuit and/or sound card is causing the distortions.
The CE-150 uses Frequency Shift Keying (FSK) to transfer binary data via audio signal (e.g. to a tape recorder). It sends four pulses of 1.27 kHz for a binary “0” and eight pulses of 2.54 kHz for a “1”.
To test the circuit I’ve taken the original design and simulated the circuit in LTspice (running under Linux with Wine). This tool allows the simulation of various analog (and digital) circuits – perfect for my test.
The result was – to be honest – pretty surprising for me. The upper screenshot shows the LTspice simulation of the output signal, the lower screenshot was taken from a WAV file in Audacity. I was not only able to simulate the circuit but also to use the resulting signals as a good approximation for my amplifier circuit (not shown). 🙂 One minor fix (also not shown) left was to adapt the transition time between a “0” and a “1” to better fit to the original curve.