Sense Hat Lights up Pi

One of our chief complaints about the Raspberry Pi is it doesn’t have a lot of I/O. There are plenty of add ons, of course to expand the I/O capabilities. The actual Raspberry Pi foundation recently created the Sense Hat which adds a lot of features to a Pi, although they might not be the ones we would have picked. The boards were made for the AstroPi project (the project that allowed UK schools to run experiments in space). They don’t appear to be officially for sale to the public yet, but according to their site, they will be selling them soon. Update: Despite some pages on the Raspberry Pi site saying they aren’t out yet, they apparently are.

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A Tale of Three Soldering Iron Controllers

[ZL2PD] needed to replace an old Weller soldering station and decided not to go with one of the cheap soldering stations you can find all over the Internet. He has a long story about why he had to design his own controller, but you never have to explain that to us. He kept detailed notes of his journey and in the end, he built three different controllers before settling on one.

He started with a Hakko hand piece that uses a thermistor for temperature measurements. The first iteration of the controller had analog controls. He wasn’t happy with the number of parts in the design and the simple LED display. That led him to replace the controller with an ATTiny CPU and a use a serial LCD.

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Clocking (or Overclocking) an AVR

Some guys build hot rods in their garage. Some guys overclock their PCs to ridiculously high clock frequencies (ahem… we might occasionally be guilty of this). [Nerd Ralph] decided to push an ATTiny13a to over twice its rated frequency.

It didn’t seem very difficult. [Ralph] used a 44.2 MHz can oscillator and set the device to use an external clock. He tested with a bit-banged UART and it worked as long as he kept the supply voltage at 5V. He also talks about some other ways to hack out an external oscillator to get higher than stock frequencies.

We wouldn’t suggest depending on an overclock on an important or commercial project. There could be long term effects or subtle issues. Naturally, you can’t depend on every part working the same at an untested frequency, either. But we’d be really interested in hear how you would test this overclocked chip for adverse effects.

Now, if you are just doing this for sport, a little liquid nitrogen will push your Arduino to 65 MHz (see the video after the break). We’ve covered pushing a 20MHz AVR to 30MHz before, but that’s a little less ratio than [Ralph] achieved.

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Scrappy RGB Binary Clock From The Parts Bin

Sometimes you just want to make something, and not spend any money doing it. That’s what [Evan] had in mind when setting out to make this cool RGB LED binary Clock.

The project box is made from scrap pieces of balsa wood, with the front being a scrap of acrylic.  Multiple layers of the balsa wood were glued up to thickness and drilled to hold the LED’s, some paper was added on top then the acrylic to give everything a frosty diffused look.

LED’s are controlled by the good ‘ol 74HC595 serial to parallel shift register, and a ATTiny84 micro all set on scraps of perf board [Evan] had kicking around. Time is kept by an off the shelf RTC module and everything is point to point wired together .

Once the glue dried and a lid added, [Evan] has a colorful and fun looking 4 bit per digit binary clock that always takes us a few moments to read.

Upgrading An Old Lantern

[Shockwaver] stumbled across some old kerosene lanterns, and decided he also stumbled across his next project. He decided to leave the kerosene out, and in its place used some RGB LEDs to bring the lanterns back to life. This is quite an upgrade. Considering the burning kerosene will only put out a few colors of light, the astute reader will have realized the RGB array has the ability put out over 16 million colors.

After some initial testing, he settled on a 24 LED circle array powered by an ATtiny85. The FastLED library helped him keep the code within the tight memory requirements. [Shockwaver] was not used to working with the such a small amount of memory, but after some fiddling he was able to make it work in the end, using 8,126 bytes.

The source can be found on his github page. Be sure to check out the video below to see the RGB lantern in action.

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Embed With Elliot: Shifting Gears With AVR Microcontrollers

Most modern computers are able to dynamically adjust their operating frequency in order to save power when they’re not heavily used and provide instantaneous-seeming response when load increases. You might be surprised to hear that the lowly 8-bit AVR microcontrollers can also switch CPU-speed gears on the fly. In this edition of Embed with Elliot, we’ll dig into the AVR’s underappreciated CPU clock prescaler.

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Embed with Elliot: Multiplexing SPI Uses Few Pins

[Ralph Doncaster], aka Nerdralph, seems to be absolutely driven to see how few resources he can use on a microcontroller to get the job done. In this post on his blog, [Ralph] writes some custom bit-banged SPI code to cut the number of SPI lines necessary to drive an nRF24L01+ radio module from four down to two. That really helps if you’re using a micro with only six free pins, like an ATtiny85.

If you’re going to say, “why don’t you just buy a bigger microcontroller?”, you’re missing the point. This exercise strikes us as optimization for optimization’s sake and a dirty hack, both of which are points in its favor.  There are also a couple of techniques here for your mental toolbox. We thought it was interesting enough to look at in depth.

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