Passive Filters, Data Transmission and Equalization Oh My!

[Shahriar] is back with a new “The Signal Path” video. It has been a few months but it is okay because his videos are always packed full of good information. Some new equipment has been added to his lab and as an added bonus a quick tour of the equipment is included at the start, which is great if you like drooling over sweet machines.

The real focus of the video is high speed data communications, getting up into the GHz per second range. [Shahriar] covers filtering techniques from simple RC low pass filters to pretty complex microwave filters. Explaining frequency and time domain measurements of a 1.5Gbps signal through a low bandwidth channel. He also shows how equalization can be used to overcome low bandwidth limitations.

It is an hour long video jam packed with information, so you might want to set aside some time and have a pencil on hand before going in. It is well worth it though, so join us after the break.

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Dye Mac Dye!

Fabric dye is one of those products where it keeps popping up for unintended uses, we have seen it coloring printed circuit boards, and now a Macintosh computer? [The Brain]’s project to add a little color to his Macbook has been done before, but he chooses to do it in a different way, which comes down to a little bit of sandpaper.

You could go ahead and dye the Macbook plastics as is, but that thick layer of glossy plastic is going to take much more time to penetrate and its going to resist taking the color, so it might end up splotchy. The simple solution to this is to just sand off the gloss, that way the color has much less of a barrier to dye the plastic. Once the protective gloss shell is sanded away and cleaned throughly, Rit brand fabric dye is added to a pan of water and set on the stove to boil.

While most of the case plastics are thick and tough enough to withstand some heat, care does need to be taken when dealing with thin soft parts like the display bezel. After about 45 min the parts are dyed and popping with super bright orange color in record time.

Attiny25 Based Function Generator Causes a Wave

Function generators are a handy bench tool to have around, and while you can usually cobble something together that works, it is much more handy to grab a device when you need it. Thats where this function generator sent to us by [Mohonri]comes in. Based around a ATTiny25 and a rail to rail op amp which is able to replicate frequencies from 1Hz to about 40KHz, in square, triangle, and sinewaves simultaneously.

The function generator also features independent amplitude control on each output. And it’s all on one palm-sized, single-sided PCB. The main part of the code is split into two parts: the main loop gets the inputs and constructs a waveform table in SRAM, and then an ISR reads that table and outputs it to one of the timers, which produces a PWM output, which is low-pass-filtered and then passes through a potentiometer (for amplitude control) and then to an op-amp before landing on a set of terminals.

Though its not 100% perfect, trading speed for a 6 bit resolution, it should be more than enough for most electronic projects. You can pick it up in kit form from the on-line shop, but schematics, software and PCB layouts are also available for download.

Designing a Smarter RF transceiver

Two  months ago we featured a transceiver based on the Microchip MRF49XA, and a lot of feedback was sent to [hpux735] requesting that some brains be added onto the system. [hpux735] decided that if he was going to do it, might as well go the distance and make a make a native USB transceiver.

The prototype model is designed for use with the Atmel AT90USBKey, and uses the LUFA USB framework. The protocol and packet format was revised, and a Hamming Code implementation was built using look-up tables to give error control. Finally once the prototype was ready to go [hpux735] created some awesome little PCB’s that contain the AVR, radio, antenna hookups, and blinky lights (no project is complete without blinky lights) are all ready to go when you are.

This project has come quite a long way, covers 3 blog pages, uses a fair bit of ribbon cable, but you just got to love when a plan comes together.

DIY Solid State Tesla Coil

Tesla Coils are always a blast to see and are relativity simple to build. While there are plenty of sites on the subject, [Michael’s] newest instructable breaks building a solid state Tesla Coil down to 12 easy steps.

Items that should be familiar to anyone who has even looked at a Tesla Coil include PVC pipe, Aluminum ducting, and wire … lots of wire. The PVC pipe is cut to length and a flange is attached to help form a base. From there the pipe is wound with about ¾ of a pound of 30 AWG enameled wire, which takes some time by hand to make sure you don’t overlap or get space between the coils.

Aluminum ducting is then wrapped around the outside of a second flange. Some stovepipe wire is ran though the ducting and twisted to close up the 2 ends, and hot glue is used to attach the two ends together. The assembly is screwed to the top of the pipe now containing the secondary of the massive transformer. All that is left is to attach a primary, which is made out of a few turns of 16 AWG wire, and the control circuitry.

Join us after the break for a shocking video!

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Robotic Etch-a-Sketch Draws Grayscale Images

[Patrick] decided to make a computer controlled etch-a-sketch. While the idea is not that new, there is always a different way to accomplish a goal. An Arduino is used to control a pair of stepper motors which were sourced for pretty cheap, and even came with their own driver. Next a stand was mocked up using foam board, which helps determine where all the parts should live.

Next was a way to attach the steppers to the knobs, gears would be used and a collet meant for model airplanes was sourced to make the mechanical connection between gear and shaft. With everything set in place via foam board and paper printouts, it is off to get some thin plywood. The plywood is sent though a laser cutter creating most of the stand and gears. Now its all software, a program was whipped up for OSX which converts low res pictures into squiggly lines perfect for the etch-a-sketch to draw on its screen.

The results are quite impressive, join us after the break for a quick video.

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DIY Windows 8 Tablet

[hackitbuildit], from instructables, has brought us a a DIY windows 8 tablet. To make the tablet, an old laptop is used that meets the minimum requirements of windows 8 preview, a touch screen conversion kit, and of course the software itself. The laptop is first prepared by removing the casing around the screen, and if you just go by the pictures it kind of looks like he is ripping it apart! Though if you look at the video screws are being removed.

The screen is flipped around and laid on the keyboard with a couple spacers between them, as many laptops use the keyboard area as heat sinking. The touch screen is installed, and some wood strips are hot-glued to the outside to fill in the gap between the screen and base. With a little paint you’re left with a large, but functional windows 8 tablet to get started developing for.