The pre-programmed microchips I wrote about last week arrived. I took a live, working Clock on my desk from a previous batch and that became the test bed. I de-soldered the old microchip, dropped a new one in, and voila, it worked. There's something amazing to me that I can reach out to a vendor, say "gimme the same thing you gave me last time" and, even though it was a few years later, get exactly that.
I also have a renewed appreciation for production quality systems where you can trust that what's on the BOM is good. I had a pretty hacked together system and folder structure, but I could still find my BOM and my old PO's, and the firmware image is for sure a trackable line item. It's part number AWK-105-0047RevA.hex, and it comes with corresponding revision controlled fuse and lock bit settings.
So the microchips are on there way to the assembly house and I'm one step closer to a new batch of Clocks.
Thinking Up Projects to Prototype
On a separate tangent, I recorded an episode for the Pick Place Podcast a while ago. It came out just recently, and one of the things we talked about was a technician I worked with who had phenomenal skills at making surface mount electrical prototypes, with intricate little traces made out of copper tape, and beautifully laid out little jumper wires.
This is something I've had in the back of my mind for a while and I've been thinking about things to prototype to practice those surface mount hacking skills.
I may have an idea.
When I was a kid (this was in the 90's), I had a DIY hobby kit that I soldered together. It was called the TS-4 "Tickle-Stik" from Ramsey Electronics and it turned 3 volts DC into about 85 volts AC, which is enough to feel a buzz. In retrospect, I'm surprised this was ever sold to the public, but hey, nobody got hurt and it was fun. You might even say, electrifying. (I'll show myself out.)
Anyway, I found it in my basement, it's no longer functioning, but I thought, maybe I can reverse engineer it and then use this as inspiration to build a prototype.
The Internet Delivers
Then I thought, the internet never forgets and maybe I can find the manual for this thing, along with the schematic and save the reverse engineering step.
Well, the internet has delivered in spades. I'm not sure Ramsey Electronics sells hobby kits any more, but I did find an archive with a pdf of the manual and I have an email out to Ramsey's sales team to say hello and see if the original owner/inventor is still around.
Crowd Sourcing an EE Consult
Anyway, the whole point of this post is that I'm scratching my head a little over the schematic and while I play an electrical engineer for fun sometimes, I'm mostly a mechanical engineer on the inside.
The circuit is an example of a blocking oscillator. When the circuit and the transistor turns on, feedback from the transformer secondary "blocks" the signal that turned on the transistor in the first place, which in turn kills the current to the transformer primary, which leads to a current drop in the secondary, unblocking the transistor to turn on again, and leading to oscillations.
Or so I think.
I keep scratching my head, because I think the polarity on the transformer is backwards. Part of me thinks that I might have theory of operation slightly off, and it's overshoot and ringing in the RLC portion of the secondary that creates a negative voltage and turns the transistor off, but again, I'm not sure.
Anyway, if you're an EE and willing to talk me through it, drop me a line!