Solenoid engines? They definitely fall into the the category of because you can. Some people take it to a whole other level (like this V8 model).
What I have here is much more modest - a single-cylinder engine powering an impromptu-wire-art drive train. The mini-solenoid used here has a very small effective stroke - about 8mm - which necessarily constrains the gearing. I was inspired by 30GB's similar model for the layout.
A Wien bridge oscillator is essentially an RC Band Pass Filter with a high Q factor at the resonant frequency, and generates a nice sine wave. I wanted a simple audio-frequency test signal generator, and a Wien Bridge turned out to be perfect for the job.
Here's yet another way to drive a 7-segment single-digit display unit - using a CD4026.
The CD4026 is a 5-stage Johnson decade counter with decoded 7-segment display outputs and display enable. With RESET and CLOCK INHIBIT low, and DISPLAY ENABLE IN high, the 7-segment display outputs progress through the 0-9 sequence on the rising edge of the CLOCK pulse.
It's an interesting alternative to a shift register for driving a 7-segment LED (as in (more...)
This AT89S52-based "shake stick" kit pops up all over the place for a few dollars. I built it and hey, it works great!
But it's not pacakged to be easily re-programmed for other messages or graphics. So started my sleuthing.. which turned into a fascinating story.
It seems the kit was originally designed and built as a uni project by Zheng Zhong Xing 兴向荣 (aka zhengzhongxing39) studying Control Technology and Instruments/Principles and Applications at a (more...)
Then you see the work in progress - the cranes, scaffolding, workers scurrying around the site. But that is what I think really brings it to life. This is not a frozen, finished statement of something other-worldy. It's a vibrant (more...)
So for another project I wanted some "glowing" LEDs, ideally powered from a single 1.5V AA or AAA battery. That seemed like an interesting challenge, especially when the forward voltage of the LEDs I'm using is about 2.1V.
I had a feeling I could cobble together a couple of ideas (Relaxation Joule Thief and RC Oscillator) .. and lo, it works!
Going back to basics - this project is a test of directly driving a common cathode 7-segment LED with an Arduino. It covers the fundamentals behind more advanced circuits like this custom PCB with register interface.
The board combines a common-cathode 7-segment display with a shift register and current-limiting resistors. Nothing earth-shattering, but a good little KiCad exercise. I recently got the boards back from OSH Park, and they work just fine!
The AT24C02 is from Atmel's line of serial EEPROM chips with a whopping capacity of 2K! (256 x 8) That's not a whole lot more than the onboard EEPROM in an Arduino, but it does have the advantage of being external:
it can stay in-situ even if the microcontroller disappears/gets exchanged
multiple devices can share access
There are a few libraries available that encapsulate the interaction with external EEPROMs, but first step is a simple (more...)