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When we moved house this past autumn I was adamant with every member of the family, including the two who are college age and on their own (sort of) that the garage was not going to be fair game to store their excess stuff, that we now had a basement, and if they couldn't fit something into their own living space or the basement we didn't need it. This was in contrast to our previous garage, which over time had become so filled with everyone's random junk that I was using my truck's tailgate as a makeshift workbench those times that I needed to do repairs on something or even build something from scratch. They all fought me, not openly of course, but by the time we were moved in the garage was nevertheless full from front to back. In the weeks since the weather became tolerable here I've managed to reclaim almost all of the space, cramming all of the Christmas and Halloween decorations back into the basement, putting up shelves and just moving things around and organizing. So now it's time to start getting some back burner projects done.
This one is already underway as of last week. My grandfather bought a rototiller for my grandmother in 1967. I have a lot of fond memories around this machine mostly revolving around my grandma, who was one of my favorite humans to have ever walked this earth. She loved to cook, loved to laugh, and her cooking spilled over into a love of gardening. All things that she, above all else, loved to share with her family. Especially our generation. One of my favorite memories was of helping her in the garden and watching the grips slip off this beast and the tiller subsequently take off through the yard under it's own power while she looked at those useless bits of rubber in her hands and uttered the only curse word I ever heard come from her mouth, with a suitably stunned look on her face.
My dad inherited the tiller. He used it a lot over the years. It got loaned out. His stepson blew up the engine once, and dad replaced it with a more powerful model. Now my dad is 71 and not getting around very well. He offered it to me, and I jumped at it. But it's also been sitting for a few years.
So last week on my days off I began going through it to atemmpt to get it running again. Dad accidentally left gas in it before storing it, so the tank needed drained and flushed. The gas line was completely rotten, and the carburetor was pretty varnished up. I began taking said carburetor apart, then checked to see how much a new one ran and was pleased to find out they're only $13. Now, ordinarily I would have fixed it anyway, preferring not to just throw things away. But there are definitely parts of this assembly that were not meant to be disassembled and put back together, including the float bowl. So I bought the new carb. I also drained the gearbox (and got the distinct impression that what was in it dated from 1967). It's almost back together now. As I had already determined that it was getting spark, and managed to get it to fire by putting some gas directly into the carb, I'm pretty sure that it'll be up and running come Tuesday morning when I'm off work next.
In addition to software I love to build things in the physical world. I've built things ranging from furniture to guitars to several guitar amplifiers in the past. I have a fascination with old vacuum tube based electronics. Having larger discreet components to work with allows you to recombine things in interesting ways and using a lot less fine motor skill than what is required when working with modern IC chips and surface mount components. But it's been a few years now since I built any electronic gear, as I haven't had anywhere to actually work that wasn't the dining table (and girlfriends to tend to find that objectionable).
Anyway, combining my hobbies of music, electronics and coding into a single project is something I've wanted to do for a while. So project one is something that's been on the back burner for quite a while - a guitar pickup winder. I've had most of the components sitting around for quite a while now, and I'm tired of putting it off.
My winder is going to be powered by a Chinese made replacement sewing machine motor. It's a cheap way of getting a motor with a foot controller, and more than adequate for the task. The interesting part comes in when you get to the counter. There will be a four digit display provided by four Russian nixie tubes, triggered by a hall effect sensor and driven by an Arduino Mega knockoff (the IC's that were originally used for this purpose have long since gone off the market).
Now, a nixie tube has a separate cathode for each symbol that it displays and a common anode. In order to display the correct symbol, you have to allow current to flow in only one cathode. I could have used some high voltage transistors for the task (and indeed this is common practice) but I have a few objections to this way of doing things. The nixies fire at somewhere around 140-170v, and most transistors don't particularly like higher voltages. A lot of the ones that do aren't going to be able to dissipate a lot of heat, either, potentially limiting lifespan. But really I'm making excuses for what I really don't like. They're tiny and hard to work with, and don't look "cool".
Anyway, I have a big crate of vacuum tubes that came from an estate sale years back. The guy had been a television repairman back in the day. The plan is to sort through that box and find a suitable twin triode that I have in sufficient quantity to drive all four nixies, which means I'll be using 20 twin triode tubes for switching to operate a four digit display. Now that's sufficiently ridiculous for my taste. It's like putting a big block Chevy in a speedboat. I like it.
Since this is only for me and will never be resold or marketed I'll be running the tube filaments in a series string directly from wall current. For the nixie's high voltage supply I have a choice of directly recifying wall current, which is definitely frowned upon but works just fine so long as you are absolutely sure that the outlet is correctly wired, or else scavenging one of my early guitar amps for it's 150v secondary power transformer and building a more conventional center tapped supply with CLC filtering.
The cathodes of the twin triodes will go to ground through a couple of LED's to provide consistent bias voltage, with the anodes tied directly to the nixie cathodes. The triode grids can then be driven from the MCU pins, which is why I need the Mega version of the arduino. I need at least 40 pins, plus one for a directional switch (I want to be able to back off some turns if needed and have the counter count downwards while doing so) and another to signal a counter reset. There are ways of multiplexing from a smaller number of gpio pins, but these devices are sufficiently cheap (and the chassis will be sufficiently large) that it's just easier to program the larger board.
I'll mount the tube sockets to a curved sheet of metal in four rows of six, with the nixie at the bottom so that the mubers face roughly towards the operator. The power supply and MCU will sit in a small box underneath that panel, with the motor housed behind it. I'm going for a mad scientist's lair vibe with it and plan to just let it show proudly it's handmade origin. I think the curved panel might even be reminiscent of an old cash register.
I already have the arduino clone, the motor and pulleys, shaft for the bobbin arbor, all of the tubes and sockets for the nixies. I'm pretty well set with wood which will be employed liberally for a lot of parts. So the only things left to aquire are going to be some sheet metal for that panel, for which I need to decide if I'm going to go with steel, aluminum or something like copper which I could decorate, 20 tube sockets (probably the octal type) and I need to resupply on wire. Lots of wire in this case. In multiple colors, so that it's easier to differentiate the ten different cathode wires for each nixie. That shouldn't actually be too bad. Oh, and I'll need some switches and a power brick for the MCU.
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