[Teknynja] was working on a project where he needed to drive a few strips of Adafruit Neopixels – WS2812 LED strips – that were located several feet apart. These LED strips draw a lot of current, and are very timing sensitive; anything more than a few feet of wire between the microcontroller and the LED strip will probably result in missed data, voltage drops, dimming LEDs, and possibly a non-functional strip.
The solution, as in all matters concerning long distance transmission of data, was CAT5 cable. [Teknynja] used RS-422 drivers and receivers to pull this task off, with 75174 line drivers receiving signals from a Teensy 3.0, and 75176 bus transceivers reading everything at the other end of a 20 foot cable.
For the power drop issue, [Teknynja] is feeding 12V into a few of the wire pairs in the cable and using a cheap LM2596 buck converter to step everything down to 5V at the strip.
With a fairly simple circuit, [Teknynja] was able to drive a few strips of WS2812 LEDs through 20-foot lengths of CAT5 cable with ease; it worked just the same as if the pixels were connected directly to the Teensy on a workbench.
[Sprite_TM] was tapped to build a rather large quiz buzzer system. Judging from his past work we’re not surprised that he seemed to have no trouble fulfilling the request. As the system is not likely to be used again (or rarely if it is) he found a way to finish the project that was both quick and inexpensive.
Each buzzer consists of a base, a button (both mechanical and electrical), and a couple of LEDs to indicate who buzzed in first. The mechanical part of the button uses a plastic bowl from Ikea and a wooden dowel surrounded by some pipe insulation. A momentary push switch is glued on the top of that dowel, and the insulation projects above that just a bit. This way it acts as a spring. The Dowel has been sized so that the bowl lip will hit the wooden base just as it clicks the switch.
As you can see, all of the buzzers are interlinked using Ethernet cable. The real trick here is how to read 14 buttons using just one CAT5 cable. This is done with the clever use of a 4×4 button matrix for a total of 16 buttons. The matrix also includes the LEDs for each buzzer. Since CAT5 has four twisted pairs this works out perfectly.
Looking for a more robust system thank this? Here’s a pretty nice one.
Network engineer [Mario Giambanco] recently purchased a cable to move his flash off camera. Unfortunately, it ended up way too short for his purposes. Instead of purchasing a slightly longer proprietary cable, he decided to employ what he had around him: a lot of cat5e cable and ethernet jacks. He cut the cable close to the center in case things didn’t work out and he’d need to repair it. His post on building the custom ethernet flash extension cable goes into heavy detail to make sure you get it right the first time. He’s tested it using both five and 50 foot pieces of cable with no apparent lag.
This isn’t the first time we’ve seen cat5 repurposed: composite video through cat5, vga cat5 extension, and cat5 speaker cables.
[mixadj] needed to run some video cable from one part of his house to another. He was lacking the proper amount of video cable, but had a bunch of cat5 laying around. so he built a converter to run his composite signal through the cat5. He states that he wouldn’t run it more than 70 feet without amplifying the audio somehow. Aside from that, the performance is supposedly decent. This just adds to the multitude of other uses for that Ethernet cable. We’ve seen voice, data, composite video, VGA, and power. What else have you seen run over cat5?
Making a passive network tap can be an easy and inexpensive undertaking as shown in this Instructable. Passive monitoring or port mirroring is needed because most networks use switches which isolate the network traffic and this does not allow for the entire network to be monitored. This example uses a single tap, using multiple taps will provide access to the full-duplex data separately. By using two taps you are able to monitor inbound data that is passed through one tap, and outbound data that is passed through the other tap. Separate taps are desired because most sniffer software handles half-duplex traffic only and requires two network cards for full-duplex.
Continue reading “Passive network tap”
Adding PoE(Power over Ethernet) just wasn’t good enough for [steve]. Not only does he have power running over his Cat-5, he shared the ground wire and used the remaining pair to add a serial console to his rooftop mounted wireless router. Nice.
[Jachin] sent in his network port tester built from a network card, wake on lan cable and a battery holder. Three AAs supply 4.5v DC just like the motherboard would to the card via the WOL cable. Nice trick, I’d consider adding a static bag at the least to keep the card from getting zapped.