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...)
This is a simple script that runs on two Arduinos. They bounce messages back and forth over 2.4GHz using the nRF24L01+ modules, flashing their LEDs when messages successfully handled. Sweet, and the breakout boards work just fine.
So recently I've been intrigued by small-batch PCB fab services, like OSH Park. Like the ready supply of components from various online sellers, it's amazing how cheap you can get boards made over the net these days. How do they do it? As I learned in this hardware hangout, there are some neat tricks done behind the scenes to aggregate small orders into full panels sent to a fab.
A quick demonstration using four JK flip-flops set up in "toggle" mode to implement an asynchronous 4-bit binary counter. This is the classic circuit, straight out of a text book. It's implemented with:
two 74LS73 for the flip-flops
a 555 Timer astable oscillator providing the clock pulse