Simple Ring Oscillator
Inspired by my friend @vk2zay I saw him lash up a simple ring oscillator experiment he saw. Having the time and the components laying around I decided to build one too.
The original idea came from http://www.b-kainka.de/bastel127.html
You can see @vk2zay's experiments :-
And here is my little version :-
It's a very interesting little circuit and super fun to muck around with. Give it a go!
9 cell SMD Ring Oscillator
I gave up trying to build this with gEDA PCB because at the time I couldn't figure out how to rotate components to arbitrary angles. Then I discovered the wonderful "FreeRotateBuffer(
So with my nine cell oscillator schematic I set about making an SMD version of @vk2zay's ring oscillator blinkenlights. It's designed so a CR2032 battery can fit in the centre with a few soldered wire loops to hold it down. I think it turned out pretty neat.
I was thinking about making a double-sided version that links the two loops into a single larger ring so the pulse travels around one side, through the board and around the other then back.
I've found some bugs in PCB with the rotated components, the gerber output is fine, but the G-Code output (that I use for the CNC machine) leaves the pads at their original angle. And my other gerber to G-Code program CopperCAM doesn't support polygon pads (ugh!). So I'm going to have to send the boards off to a PCB house or find an alternative.
CNC Milled 9 cell SMD Ring Oscillator PCB
I managed to get my design over to the CNC mill today. I ended up using pcb2gcode to convert the gerber files. There was a bit of frig'n around but nothing to bad. I didn't change the spindle on the machine to my better low run-out Wolfgang. Instead I left the default Proxxon that has a bit of noticeable run-out when working at these sizes, that's why a few tracks are a bit thinner than I'd like (also the machine has a bit of undiagnosed backlash I haven't dealt with yet).
All in all I'm pretty happy given I just stuck down a piece of FR4 with two strips of masking tape and pressed "GO".
The blank PCB reminds me strongly of a Dharma Initiative logo from the TV show "Lost" for some reason. :)
Solder time!
Finished the SMD Ring Oscillator
So I've finished the SMD Ring Oscillator.
Unfortunately I had to re-make the original board (the one shown in previous post) as I stuffed up and made the tracks just a little too small by setting the cut depth to deep with my v-shaped engraving bit. This makes the clearance between the traces larger and the tracks smaller. I had completed building four of the nine cells when I damaged the board with the tip of my iron building the fifth one. After a few minutes trying to fix the broken track I figured I could make a new one faster and not have this problem.
So a new piece of FR4 was put in the machine, and some eight minutes later I had a new board. Too easy!
When I work with milled boards such as this with SMD components not having a solder mask is a real drag. I've used press-n-peal film and foil in the past to act as a mask, but I've found it's just simpler to use Kapton tape as a temporary mask while soldering. It works great! Love the Kapton!
I'm still figuring out the case for this board, I want to incorporate the battery holder and switch in it's design. My two year old son loves it and I want to make it a bit more child friendly. I was thinking I could simply pot the whole thing in epoxy and use a standard battery holder on the back, or I could make a plexi case and mill out the battery holder in the lid. Decisions, decisions!
For such a simple circuit it's a joyous little thing, it would make an awesome bobble on a Xmas tree. My nine cell version running on 6V draws about 15mA so a CR2032 should last a fair while. But for Xmas decorations you could easily wire a few up in a chain and power them from the wall. Linking them all together would also make a very interesting effect. You could have a master ring that has a bunch of branches that are triggered by it. Fun!
And I solemnly promise I won't make any Xmas tree shaped PCBs using this circuit.
Another interesting use for this circuit would be to use RGB LEDs or different coloured LED for alternating cells and build it into the based of a diffused ball to make a colour shifting mood light. As it stands this little red LED one makes a passable electronic candle when looked at through a piece of paper.