LEAP#354 PissOff Mutant Offspring
Somewhere in my travels (Five Below?) I picked up a cheap SpiderBot robot kit mainly to see how they drive the legs. OK, interesting for about 15 minutes then I guess I started channeling Sid and decided to hook it up with the BoldPort PissOff.
So now I have an angry sentry dog that scuttles about like a spider.
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub
The motor in the SpiderBot is really dirty and I had real trouble controlling it without interference, even with extreme isolation. But perhaps imperfect crazy action is better after all..
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LEAP#353 D Flip-Flop with NAND Gates
The D Flip-flip is the synchronous (clocked) sibling of the D latch.
There are various ways of constructing a D flip-flip from fundamental logic units, here I’m using only NAND gates. And there we have it - 1 bit of memory in a clocked register! It’s nice to see it work, even if this circuit is no longer of any real practical use.
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub
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LEAP#352 Decoding ACARS
Aircraft Communications Addressing and Reporting System (ACARS) is a short message digital datalink protocol transmitted around 129-137 MHz in different regions. As well has assisting air traffic control, it is (I gather) how services like flightaware get their data.
For a quick test, I’m using the open-source rtl_acars_ng. It built and ran on MacOSX without trouble, connecting to an R820T2+RTL2832U dongle.
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub
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LEAP#351 SDR with cheap R820T2/RTL2832U dongles
Cheap SDR dongles? Apparently it all started when a bunch of folks (Antti Palosaari, Eric Fry and Osmocom) found that the signal I/Q data could be accessed directly from the Realtek RTL2832U digital TV tuner chip, allowing it to be turned into a wideband software defined radio receiver with just a little extra hardware and softare.
Combined with a tuner front-end (commonly the Rafael Micro R820T2) in a USB dongle package with dinky antenna, these now show up in droves online for under $20.
I picked a random RTL2832U+R820T2 USB2.0 device from a seller on aliexpress. Like most, it is marketed primarily as a DAB/HDTV receiver, but first thing I did was throw away the Windows-only software provided, as I was more interested in the device as a broad-spectrum SDR receiver.
I’ve tried two MacOSX-compatible open source packages - Gqrx SDR and CubicSDR. Success with both! I’m liking CubicSDR in particular.
The other thing I learned is that the dinky 5” aerial provided with the dongle (and where I put it) is on the one hand surprisingly capable, while also having very little chance of picking out weaker signals!
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub
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