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The Music of the Protons

Paul Horowitz performing the nuclear procession experiment.

I just stumbled across this gem of an old video from MIT. It was made between 1983 and 1984, and stars Sidney Coleman, Ed Purcell, Paul Horowitz, and Isaac Silvera.

I’m a huge fan of Paul Horowitz, his Art of Electronics books have taught me much of what I know about electrical engineering. There isn’t a lot of info about him online, he seems to mainly keep to himself despite being a celebrity among electronics nerds.

The experiment they are performing is described in more detail at the bottom of this page: http://hyperphysics.phy-astr.gsu.edu/hbase/Nuclear/nmr.html

A large magnetic field is applied to a sample of hexane (a straight chain hydrocarbon with 6 carbon atoms and 14 hydrogen atoms) which causes 1 in $latex 10^{7}$ of the protons to align with this strong magnetic field. Once the field is turned off, the protons precess around the earth’s magnetic field. They do this at the Larmor frequency of approximately 2-3kHz (https://en.wikipedia.org/wiki/Earth%27s_field_NMR).

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Dusting off my Radio Telescope

Got out my little radio telescope that I built but never used.

I’m using a raspberry pi 4 now. For testing, using RealVNC is very nice. It let’s you view the desktop remotely. Eventually I’ll probably want automated collection/pointing/recording data for which a Python script would be best. But for now just logging in with RealVNC works well.

To install the rtl-sdr stuff, it is actually really easy. I started building from source, then realized you just need to do $ sudo apt-get install rtl-sdr

pi@raspberrypi-tx:~ $ rtl_test
Found 1 device(s):
Using device 0: Generic RTL2832U OEM
usb_open error -3
Please fix the device permissions, e.g. by installing the udev rules file rtl-sdr.rules
Failed to open rtlsdr device #0.

Likewise to install GQRX you can just just go to add/remove software and search for it.

You can search packages by name with

pi@raspberrypi-tx:~ $ apt-cache search gqrx
gqrx-sdr – Software defined radio receiver

The driver from Adafruit has changed for the accelerometer. I’m still using the old depreciated one.

I installed Cheese, then could hook up a USB webcam to verify the dish pointing.

Would be cool to allow other people access, need to figure out a safe way to do that. VPN?

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Jim Williams’ App Notes Are Getting Hard To Find

If you are an electrical engineer and haven’t checked out any of the app notes written by Jim Williams you are missing out!

Unfortunately, Linear Technology was bought out by Analog Devices in the last year or two and his app notes are much harder to find! The old Linear Technology website had a page with links to every app note written by Jim, the Analog Devices website has no such page. They still appear to be available on Google though, and Kent Lundberg has compiled a bibliography of his works.

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Mapping Radiation with a Raspberry Pi GPS Scintillation Detector

I just posted a new YouTube video about I project I’ve been working on for some time. It’s a scintillation detector coupled to a Raspberry Pi that lets you make maps of background radiation levels. You can leave it in your car as you drive around town and then upload the data over WiFi when you get home.

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Bob Wildar’s Introduction to Semiconductor Devices

I recently came across the PDFs of Bob Wildar’s Introduction to Semiconductor Devices in the Computer History Museum’s digital archive. I haven’t read them yet, but from glancing through chapters 1 and 2 I’m really excited. I’ve been looking for a text that explains how transistors work, not just how to use a model to predict their behavior. While having a model is important for designing circuits, I really want to have an intuitive understanding of what happens inside of a transistor that allows it to act as an amplifier. I love “The Art of Electronics”, and while it tells you pretty much everything you need to use a transistor, it doesn’t really get into what is happening inside of a transistor (other than the famous transistor man).

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Beagle Bone Black Static IP

Static IP Address under Debian

According to Derek Molloy’s website it is easy to set a static IP under Debian: http://derekmolloy.ie/set-ip-address-to-be-static-on-the-beaglebone-black/

[Updated April 2015] To set the IP address to be static under Debian is quite straightforward. You can simply alter the /etc/network/interfaces configuration file to manually specify the address (e.g., 192.168.1.80 in this case), the network mask, and the network gateway. Use an editor, such as nano, to edit the /etc/network/interfaces file and For example, the settings for my network, which has a common configuration, are as follows:
molloyd@beaglebone:~$ uname -a
Linux beaglebone 3.8.13-bone70 #1 SMP Fri Jan 23 02:15:42 UTC 2015 armv7l GNU/Linux
molloyd@beaglebone:~$ cd /etc/network
molloyd@beaglebone:/etc/network$ sudo nano interfaces
[sudo] password for molloyd:

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