The Raspberry Pi is a small computer that has become very popular. Lots of applications and hardware hacks have been made for it. You can run various software like web/file/printservers, read out sensors, the possibilities are endless.
I own multiple Raspberry Pi’s, one is a test platform for sensors, and a new one pictured above will be dedicated to audio streaming. I use the software packages darkice and icecast2 to capture the audio from an USB audio card and make it available on the internet.
temporary probe with NaI(Tl) crystal, PMT, socket with voltage divider and BNC socket
Following is a little guide to using photomultiplier tubes in DIY scintillation probes.
Photomultipliers are vacuum tubes that convert light into electrons and multiply the resulting current up to millions of times. They are used to detect the minute flashes of light generated by scintillators, materials that convert gamma and x-rays into visible light.
How to use these tubes? There are some things you need to remember when working with PMTs.
Straks gaat er een ondertekende brief de deur uit en geef ik akkoord voor een behandeling aan mijn linkeroog en medewerking aan een wetenschappelijk onderzoek.
Mijn linkeroog gebruik ik al tijden niet meer door lensintolerantie en ik zou graag weer eens met beide ogen willen zien.
Volgens de oogarts is het voor mijn linkeroog mogelijk om een gedeeltelijke hoornvliestransplantatie (DALK) uit te voeren waarbij het achterste laagje, het endotheel, behouden zal blijven. Dit heeft een aantal bijzondere voordelen, de wond zal beter helen, de kans op afstoting is lager en het resultaat is duurzamer dan de transplantatie van de gehele dikte zoals in mijn rechteroog.
Het wetenschappelijke onderzoek gaat bekijken of een bepaalde methode om laagjes hoornvlies te scheiden voordelen biedt ten opzichte van de traditionele methodes. Dit is belangrijk, want bij DALK operaties komt het bij een vijfde van de operaties voor dat men de laagjes niet goed kan scheiden en dat men toch een ouderwetse transplantatie van de gehele dikte van het hoornvlies moet uitvoeren.
Nu is het dus wachten op de operatie, een groffe indicatie van de arts is een half jaar. Uiteraard zal ik na de operatie weer de gebruikelijke updates geven.
I recently bought a Raspberry Pi to experiment with. The first things I did with it was connecting and reading out Maxim Integrated DS1820 one wire temperature sensor and the cheap Chinese DHT11 temperature / relative humidity sensor.
To connect the sensors, I soldered some female pin headers to a piece of PCB. For the one wire network I soldered a 4.7K resistor between Vcc on pin1 (3.3V) and GPIO4 on pin 7. GPIO4 is the data pin for one wire, I used GPIO2 as the data pin for the DHT11. DHT11 “modules” with a PCB and three pins have their own pull up resistor, the separate 4 pin sensors don’t. Shown below is the quick setup, I soldered the DS1820 directly to the PCB, and connected the DHT11 with some wires for 3.3V, data and ground.
GPIO pinouts differ between the Raspberry Pi versions, I found the following pinout to be correct for my Raspberry Pi, a model A version 2.
Reading out the sensors is easy. For the DS1820, load the required kernel modules which are included in the Raspbian Linux distribution: Continue reading → Post ID 1179
I recently bought a Ludlum Measurements model 2A survey meter on eBay from Obtanium. This is a nice meter which features the well known rugged Ludlum design, adjustable HV and 3 ranges of 500, 5000 and 50000 counts per minute.
Using a scintillation probe the meter easily saturates on the 500 cpm scale, and the 5k and 50k ranges are also overloaded with certain sources.
Ludlum model 2 and 3 offer about the same functionality and basically share the same PCB, circuit, knobs and switches. Depending on age and model there are certain differences, but a lot of the stuff and functionality is the same. Continue reading → Post ID 1165
I have a Cisco 1811 with a Zyxel P2812HNU-F1 VDSL modem connected to it in bridge mode. The Cisco gets the public IP address through DHCP.
I wanted to access the modem on it’s local IP address of 192.168.1.254. At first, this didn’t seem possible because all traffic out of the WAN interface is translated to the public IP address. To enable access to the modem I did the following:
First, I added a secondary IP address to the WAN interface, Fastethernet0:
ip address 192.168.1.100 255.255.255.0 secondary
Then I added a nat pool to translate internal traffic with 192.168.1.100:
ip nat pool nat_to_modem 192.168.1.100 192.168.1.100 netmask 255.255.255.0
The global NAT command requires an access list to match traffic that is to be NATted. Here I define that all traffic to 192.168.1.0/24 is to be translated:
ip access-list extended nat_to_modem
permit ip any 192.168.1.0 0.0.0.255
deny ip any any
I spend a lot of time watching video’s on YouTube. Lots of interesting channels about hardware hacking, radiation detection, electronics and stuff.
But lately something has changed. YouTube continually tries to push unrelated or unwanted videos on me. On the right side I used to see only videos that were more or less closely related to the video. But nowadays completely unrelated videos pop up. The recommendations seem to be based on two things:
- Whatever videos you watched in the past. But even with all the history deleted, videos that I watched continue to pop up on the right side, even when they are completely unrelated to the video being watched.
- Random stuff that is supposed to be “fun” but are rehashes of other videos, memes and stuff. It seems that YouTube sells these spots for $$$ to enable people to promote push their videos onto the YouTube audience.
I grew up listening a lot of metal. When you are young you will get easily impressed by all kinds of music. I used to listen to highly accessible and melodic stuff, such as power metal, gothic metal, black metal with lots of keyboards. I don’t listen to much of that stuff anymore. As I got older I began listening to less technical and melodic music. One of the genres I knew but didn’t interest me in particular was thrash metal. Sure, as virtually every young metal listener I discovered bands like Metallica, Megadeth, Sepultura, Slayer etc…
My interest in (hardcore) punk music of more recent years brought me back to listening thrash. Similar to punk it is loud, fast, contains anti-establishment lyrics and usually doesn’t dwell too much on the technical stuff.
Some years ago thrash metal got a revival and showed that there are still a lot of good bands around. Also, some bands decided to use a more humorous approach in the lyrics. Since I like extreme music but often find the lyrics crap (the usual stuff about death, destruction, the apocalypse etc. over and over again) I think this is a good thing because in the end, a lot of people go to gigs to drink some beers and have fun!
So, here some fine examples of thrash
Kreator, one of the big German thrash bands, still raging on after decades:
Municipal Waste is one of the revival bands and is highly influenced by crossover thrash. Also they make funny lyrics and videos which is GOOD!
De laatste tijd gaat het goed met mijn ogen. Ik draag vrijwel de hele dag een lens en kan dus over het algemeen mijn werk goed doen. Oogdruk was bij de laatste meting 12 dus gaat langzaam omlaag zoals verwacht. De baerveldt implant is steeds minder zichtbaar in het oog omdat alles minder rood is geworden.
Het laatste gezichtsveldonderzoek (zie boven) liet geen achteruitgang zien. Continue reading → Post ID 1102
So, I got me a new Samsung phone because my old phone, a HTC Wildfire is rather slow, especially when it comes to websurfing. It also has low crap resolution. I am much happier with the new phone. So, what to do with the old phone? It’s still a small computer with a camera and touchscreen that should be doing something instead of gathering dust in a drawer.
One of the things I thought of was a webcam for my turtle tank. It currently houses two (I think female) red cheeked mud turtles, kinosternon cruentatum. I wanted to observe how often one of turtles gets out of the water to bask and what the general activity in the tank is.
I rooted the phone since I thought it would be handy to have root anyway and installed Cyanogenmod V7, an alternative Android version. This custom ROM does not include the Google Play store to install stuff on Google Play so I had to manually flash it. I am quite unexperienced rooting Android phones and installing custom software but I got it working eventually.
Next I installed IP Webcam, a nice free webcam app. Since it has a webinterface for remote access it is easily accessible with any computer. Being http-based it’s very easy to grab the images over the wireless LAN that the phone is on using a bash script:
This script uses wget to fetch the most recent video frame (the app is capturing video all the time), uses the imagemagick tool montage to visually timestamp the image and outputs a new picture in a publicly accessible folder on my server. Finally, the most recently downloaded picture is renamed with a timestamp in the filename and moved to a archive directory on the server. Continue reading → Post ID 1088