Archive for category: electronics

A 4 Bit Computer, built from TTL chips

June 10, 2010 | electronics | By: Mark VandeWettering

I am always on the lookout for people who build interesting computers from scratch. Here’s another nifty one: a 4 bit CPU called the Duo 128 Elite by Jack Eisenmann. It’s a pretty obscure little architecture, but is cool enough to play pong on a 8×8 LED display. DUO 128 Elite

Gutenberg Gem: Letters of a Radio-Engineer to His Son, by John Mills

December 20, 2009 | Amateur Radio, electronics, Gutenberg Gems, Public Domain Resources | By: Mark VandeWettering

I love old books, even  on technical subjects like radio.  Often, by looking at the books of the past, we find them more accessible (because there was less knowledge, they assume less as a precursor) and also possess considerable historical interest. Letters of a Radio-Engineer to His Son is a nice little book by John […]

An Active Filter Design

December 12, 2009 | Amateur Radio, electronics | By: Mark VandeWettering

Eldon, WA0UWH pointed out WA4DSY’s website that features an active filter design applet. I was just waking up this morning, so I thought I might give it a try. I used LTSpice’s universal op-amp node, and wired it for positive and negative voltage feeds. I specified a 2.2uH value for the caps, and a 800hz […]

Tank Circuits…

December 7, 2009 | electronics | By: Mark VandeWettering

Okay, time to work my way through some more complicated (but stll simple) examples. First of all, let’s consider a simple parallel LC circuit. Here is one with a 10uF capacitor and a 10mH inductor in parallel with an AC source: We can compute the resonant frequency using the classic formula: 1 f = ———— […]

Simple Temperature Sensing IC

December 3, 2009 | Amateur Radio, electronics | By: Mark VandeWettering

A couple of projects that I’ve been pondering could make use of a little temperature sensing chip. Microchip makes this little gadget, the MCP9700A, which could be quite useful, and can be had for about $.35 from Digikey or Mouser. It comes in a simple TO-92 package, or smaller surface mount chips. MCP9700A-E/TO-ND.

Homemade Thin-Film Transistor Experiments

November 18, 2009 | Amateur Radio, electronics | By: Mark VandeWettering

Another link to some interesting experiments on building your own thin-film transistors. And a Quarter Gets You Coffee » Homemade Thin-Film Transistor Experiments Addendum: Of course any mention of building your own transistors would be remiss if it didn’t mention hacker-savant Jeri Ellsworth. She did an amazing job fabricating her own semiconductor devices, and in […]

TEMPEST: A Signal Problem – Hack a Day

January 27, 2009 | electronics, Security | By: Mark VandeWettering

I’m not 100% obsessed (more like 98%) with radio topics: this morning, I found this link on Hack a Day which provided a link to several articles having to do with TEMPEST. I’ve blogged about TEMPEST before, but for those who haven’t heard of it before, it’s a way of eavesdropping on electronic signals by […]

All About Circuits on Feedback

January 21, 2009 | Amateur Radio, electronics | By: Mark VandeWettering

I was digging around information on common emitter amplifier design, and encountered this link which seemed quite helpful. Digging around the All About Circuits webpage, which seems to be a very useful online reference. It helped me understand the presentation that I’ve been reading in my copy of Hands-On Radio Experiments. More on that soon. […]