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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AltSoftSerial looks to speed up Arduino software UART

So let’s say your using an Arduino in your project. You already have the hardware-based serial interface working with one portion of the project and need a second serial port for unrelated hardware. The obvious solution is to write one in software. But this is a place where working in the Arduino environment gets really hairy. Since there’s a layer of abstraction between the code and the hardware interrupts, it can be difficult to know if you are going to have timing problems. But there’s a new library available which seeks to reduce the latency of software-based serial communications so that you don’t have to worry about it.

It’s named AltSoftSerial because it is a software-based serial library that is an alternative to the NewSoftSerial package. The former can function with just  2-3 microseconds of latency, while the latter has as much as a 174 microsecond hit. If it functions as advertised that’s quite an improvement. It’s not hard to put together a hardware test platform, and the example program is only about a dozen lines of code (which is the beauty of working in this environment) so give it a try if you have a free hour here or there.

Connecting a dumb scale to your smartphone

[Casainho] wanted to track his body weight using an app on his Android phone. He just needed a way to get the weight readings onto the device automatically. He ended up adding Bluetooth to a bathroom scale and hacking the app to grab data from it.

The scale which he hacked is a digital model, which makes it possible to read the weight data if you know what you’re doing. [Casainho] already completed a weight logging scale hack which stored the data on an SD card. So this was a recreation of that project but with a Bluetooth module for the output rather than the card for storage.

Now you can buy WiFi enabled scales, but that’s not nearly as fun as a hack like this. Plus one of those will cost you around $200 and the hardware for this version came it at only $75. It includes an LPC2103 dev board, $6 Bluetooth module, character display, batteries, and misc. supplies. The software end of the hack was helped greatly by the fact that the Android apps which [Casainho] is using are both open source.

Fill in the bass on your PSP

[Michael Chen] felt the sound his PSP was putting out needed more dimension. Some would have grabbed themselves a nice set of headphones, but he grabbed his soldering iron instead and found some space where he could add a bigger speaker.

Mobile devices tend to cram as much into the small form factor as possible so we’re surprised he managed make room. But apparently if you cut away a bit from the inside of the case there is space beneath the memory card. [Michael] cautions that you need to choose a speaker rated for 8 ohms or greater  in order to use it as a drop-in replacement for one of the two original speakers. But he also touches on a method to use both stock speakers as well as the new one. He suggests grabbing an LM386 op-amp and a capacitor and hooking them up. Yep, there’s room for that too if you mount it dead-bug-style. We wonder how the battery life will be affected by this hack?

Wireless controllers for all your retro systems

Remember those old wireless controllers made for the consoles of our youth like the NES and Super Nintendo? They didn’t work well, mostly owing to the fact they were built using the same infrared technology that is found in a remote control. Now that all the modern consoles are wireless, [micro] over at the nftgames forum decided to update his classic systems for wireless control.

The transmitters and receivers are built around an nRF24L01+ radio module that operates in the 2.4 GHz band. [micro] has the process of converting his controllers down to a science. He cuts the cord and wires the controller up to an AVR running at 16 MHz. The AVR sends this to the receiver where the button presses are sent through the original controller port. Basically, [micro] recreated a WaveBird controller for his NES, SNES, Saturn and N64.

The controllers are powered by internal lithium batteries, but the charging ICs are too expensive to put in each controller. To solve this problem, [micro] crafted a small external charging circuit that plugs into a 3.5mm jack on each controller. Check out [micro]‘s controller demo after the break.

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Gold leaf circuit board

Ah, the glitter of gold… or fake gold, we’re not really sure. But [Mike Hogan] and [PJ Santoro] have been working with faux gold leaf as a conductor on circuit boards. The device you see above is mounted on metal-covered paper substrate and it really works.

They started by applying spray adhesive to heavy paper to make the gold-clad they needed. This was cut down into hexagons in homage to their hackerspace, Hive76 in Philadelphia. From there the shape of the microcontroller (an MSP430 G2211 in this case) to prevent shorts under the chip. The leads were flattened to interface well with the gold contacts, and a hobby knife was used to score the traces. Some careful soldering made up the final connections, and they were in business.

Oh, wait; chip on board but nothing on chip. They forgot to program it first! Since there’s no header they needed an easy way to interface with the board. The clever guys used the power of magnets to hold alligator clips in place. See how they did that in the demo video after the break.

They’re also working on some boards that use conductive ink similar to this hack but we haven’t seen a write-up from these two about those experiments… yet.

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See in the dark with this bracelet build

Even though she’s only in 8th grade, [Hannah Prutchi] is turning into a very respectable builder. She designed SharkVision, a wearable distance sensor that is meant to help the blind find objects they might bump into.

The SharkVision gets its name from shark’s ability to ‘see’ prey in their surroundings by sensing the local magnetic field. Instead of building her own Ampullae of Lorenzini, [Hannah] decided to take the easy route and use a few infrared sensors mounted to a bracelet. Whenever something is picked up by the proximity sensor, a voltage is applied to a pager motor telling the wearer they’re about to run into something.

[Hannah] and her classmates have successfully tested the SharkVision bracelet by walking around their classroom with eyes closed. They didn’t bump into anything, a fact [Hannah] attributes to neuroplasticity. We think it’s a neat build, but we’re wondering if this could be given to a population of blind people.

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