Fantastic Tach Is Strangely Called Tachtastic

tachtastic diy tachometer

We all have projects from yesteryear that we wish had been documented better. [EjaadTech] is fighting back by creating a project page about a tachometer he built 3 years ago while in college. He’s done a great write-up documenting all the steps from bread-boarding to testing to finished project. All of the code necessary for this tachometer is available too, just in case you’d like to make one yourself.

At the heart of the project is an AVR ATMega8 chip that performs the calculations and controls the LCD output screen that displays both the immediate RPM as well as the average. To hold everything together, [EjaadTech] etched his own custom PCB board that we must say looks pretty good. In addition to holding all the necessary components, there is also an ISP connector for programming and re-programming.

There are two attachment options for sensing the RPM. One is a beam-break style where the IR emitter is on one side of the object and the receiver is on the other. This type of sensor would work well with something like a fan, where the blades would break the IR beam as they passed by. Then other attachment has the IR emitter and receiver on one board mounted next to each other. The emitter continually sends out a signal and the receiver counts how often it sees a reflection. This works for rotating objects such as shafts where there would not be a regular break in the IR beam. For this reflective-based setup to work there would have to be a small piece of reflective tape on the shaft providing a once-per-revolution reflection point. Notice the use of female headers to block any stray IR beams from causing an inaccurate reading… simple and effective.


Talking BeagleBoard with [Jason Kridner]

[Jason Kridner] is a member of the i3 Detroit hackerspace and during the Hackaday meet-up we were able to spend a few minutes talking about what’s going on with BeagleBoard right now. For those of you that don’t know, BeagleBoard is a non-profit foundation which guides the open hardware initiative of the same name. This includes BeagleBone which is the third iteration of the platform. [Jason's] a good guy to talk to about this as he co-founded the organization and has been the driving force in the community ever since.

Right now the organization is participating in the Google Summer of Code. This initiative allows students to propose open source coding projects which will help move the community forward. Students with accepted proposals were paired with mentors and are paid for the quality code which is produced. One of the projects this year is a 100 Megahertz, 14-channel Logic Analyzer which [Jason] is waving around in the video. It’s the GSoC project of [Kumar Abhishek] and you can learn more from his proposal.

Also of interest in the video is a discussion about the power of the BeagleBone’s PRUs, or Programmable Real-Time Units. They’re basically unused microcontrollers that have direct access to a lot of the processor’s features and are just waiting for you to bend them to your will. Having these is a huge boon for hardware hackers. If you haven’t played with them before, check out our earlier article on what PRUs are all about and then give it a whirl yourself.

After the break there’s a brief table of contents which maps the topics in the video above.

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PIC Up a NeoPixel Ring and C What You Can Do Using This Tutorial

lit ringAs [Shahriar] points out in the introductory matter to his latest video at The Signal Path, Arduinos are a great way for a beginner to dig into all kinds of electronic excitement, but they do so at the cost of isolating that beginner from the nitty gritty of microcontrollers. Here, [Shahriar] gives a very thorough walkthrough of a 60-neopixel ring starting with the guts and glory of a single RGB LED. He then shows how that ring can easily be programmed using a PIC and some C.

[Shahriar]‘s eval board is a simple setup that he’s used for other projects. It’s based on the PIC18F4550 which he’s programming with an ICD-U64. The PIC is powered through USB, but he’s using a separate switching supply to power the ring itself since he would need ~60mA per RGB to make them burn white at full brightness.

He’s written a simple header file that pulls in the 18F4550 library, sets the fuses, and defines some constants specific to the ring size. As he explains in the video, the PIC can create a 48MHz internal clock from a 20Mhz crystal and he sets up this delay in the header as well. The main code deals with waveform generation, and [Shahriar] does a great job explaining how this is handled with a single pin. Before he lights up the ring, he puts his scope on the assigned GPIO pin to show that although the datasheet is wrong about the un-delayed width of the low period for a zero bit, it still works to program the LEDs.

[Shahriar] has the code available on his site. He is also holding a giveaway open to US residents: simply comment on his blog post or on the video at YouTube and you could win either a TPI Scope Plus 440 with probes and a manual or a Tektronix TDS2232 with GPIB. He’ll even pay the shipping.

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800+ LED Wall With Diffuser Panel is a Work of Art

LED Wall

What happens when you take over 800 individually addressable super bright RGB LEDs and house them in a giant diffused panel? You get awesome. That’s what you get.

[Epoch Rises] is a small electronic music and interactive technology duo who create cool interactive projects (like this wall) for their live shows and performances. They love their WS2812B LEDs.

The cool thing about this wall is that it can take any video input, it can be controlled by sound or music, an iPad, or even generate random imagery by itself. The 800 LEDs are controlled by a Teensy 3.0 using the OctoWS2811 library from Paul Stoffregen which is capable of driving over 1000 LEDs at a whopping 30FPS using just one Teensy microcontroller. It works by using Direct Memory Access to send data over serial into the Teensy’s memory and directly out to the LEDs with very little overhead — it is a Teensy after all!

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Quick and Dirty RFID Door Locks Clean up Nice

homemade RFID Door Locks

[Shawn] recently overhauled his access control by fitting the doors with some RFID readers. Though the building already had electronic switches in place, unlocking the doors required mashing an aging keypad or pestering someone in an adjacent office to press a button to unlock them for you. [Shawn] tapped into that system by running some wires up into the attic and connecting them to one of two control boxes, each with an ATMega328 inside. Everything functions as you would expect: presenting the right RFID card to the wall-mounted reader sends a signal to the microcontroller, which clicks an accompanying relay that drives the locks.

You may recall [Shawn's] RFID phone tag hack from last month; the addition of the readers is the second act of the project. If you’re looking to recreate this build, you shouldn’t have any trouble sourcing the same Parallax readers or building out your own Arduino on a stick, either. Check out a quick walkthrough video after the jump.

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Make that C64 Keyboard Work as a USB Keyboard


Let’s face it, we all have keyboard peculiarities. Don’t try to deny it, everyone who types a lot has an opinion of the keyboard they stroke so frequently. We know [Brian Benchoff] swears by his model M, and we’re guessing he was the one that bumped into [Evan] and convinced him to write about his conversion of a Commodore 64 keyboard for use as a USB device.

This is not [Evan's] first rodeo. We recently saw him fixing up the worn off letters of his own model M. But this time around there’s some clever microcontroller work at play. Apparently mapping 122 keys using an Atmel AVR 32u4 chip (built in USB connectivity) is quite a task. Luckily someone’s already worked out all kinds of good things and is sharing the love with the Soarer’s Keyboard Controller Firmware. Of course it handles scanning, but also includes debounce, muxing, and the trick to scan more keys than the uC has pins for. We still don’t fully understand that bit of it. But [Evan] did post the config file he’s using so perhaps after we get elbow-deep in the code we’ll have a better understanding.

If you give this a try, we want to hear about it. Anyone have any modern keyboards they’re in love with? Leave a comment below.

Add a Bluetooth Interface to Your Kitchen Scale

Kitchen scale

When [Adam] found himself in need of a force meter, he didn’t want to shell out the cash for a high-end model. Instead, he realized he should be able to modify a simple and inexpensive kitchen scale to achieve the results he desired.

The kitchen scale [Adam] owned was using all through hole components on a double-sided PCB. He was able to easily identify all of the IC’s and find their datasheets online. After doing some research and probing around with a frequency counter, he realized that one of the IC’s was outputting a frequency who’s pulse width was directly proportional to the amount of weight placed on the scale. He knew he should be able to tap into that signal for his own purposes.

[Adam] created his own custom surface mount PCB, and used an ATMega8 to detect the change in pulse width. He then hooked up a Bluetooth module to transmit the data wirelessly. These components required no more than 5V, but the scale runs from two 3V batteries. Using what he had on hand, [Adam] was able to lower the voltage with just a couple of diodes.

[Adam] managed to cram everything into the original case with little modification. He is now considering writing an Android application to interface with his upgraded kitchen scale.