Nixie clock circuitry finally complete!
It may have looked like I fell off the earth, got distracted by shiny things again and dropped my electronics projects – again. Well… NOPE. I’ve been furiously, wildly and tediously soldering this beast together.
Things I learned along the way
Well, the first thing I learned is that building anything beyond a simple project is a right pain in the arse on these solderable prototyping boards. I do like their convenience, and previously I had assumed I would be limited to using this and other perfboard-type prototyping boards, but from here on out, I’ll be making proper PCBs. You’ll see why below.
A right rat’s maze
One big drawback to making your projects on perfboard or solderable breadboard or similar is the sheer number of solder joints you have to make. Not only do you have to seat all of your components and solder them in, but you need jumpers or longer wires to anywhere it has to connect to. This is fine for a simple design, but in this case, it got obscene on board two.
This is why one should get PCBs made. This took forever.
Nixie supply soldering coming along!
Winter is hard, it’s cold, there’s not enough food, the hounds attack… wait. That’s my video game. Relevant though, because that’s exactly what has been distracting me from making serious progress on my electronics projects. I am referring of course to Don’t Starve. Sometimes though, I have to force myself to haul my ass down to the basement and get something done – or I never will. I have a long history of procrastination and it’s time I finish a few things with electronics before the ice thaws.
Today, I managed to get down there and solder some more. Like many things, it’s easier once you get into the rhythm of it. I’ve never been great at soldering (see my previous post on the voltmeter sub-project) but it’s exactly true that practice makes perfect. I’m finding with each successive try, I am making better, cleaner, shinier joints that are less likely to short or crack or be non-functional.
Today is a landmark. The first time I soldered something up and it worked. I didn’t have to reflow any joints or troubleshoot mistakes, it worked. I couldn’t be more pleased. From the pictures here you can see me assembling my nixie clock and what I have done so far is solder on a triple power supply. The first two are quite simple using LM78xx regulators to gave me +12V and +5V. No explanation needed there. The second feeds off the 12V and uses a switchmode circuit to bump it up to 170V – the butter zone above strike voltage for my nixie tubes.
After a couple hours of soldering and a quick trimpot calibration, it reads 170.2V. Brilliant.
Next step is to fit the oscillator into the small space beside it to the left which consists of a 4521 frequency divider, a crystal and some passives.
Now that I’m back to where all my tools are, I had a few minutes to pop down and perform the changes I have been documenting.
After messing about with a few alligator leads, I determined that not only does IN LO need to be connected to analog common, but the voltmeter ground as well. When IN LO wasn’t grounded, I got an initial reading (with nothing connected to the input) way off zero, beyond the point the trimpot could calibrate it.
As the forum posts mentioned in my previous articles stated – the dotted connections. must both be connected for the thing to work properly. This means REF LO is connected to ANALOG COMMON which is connected to IN LO and then GROUND. Given the language in the datasheet, I would have that it was an either/or scenario, not both. Regardless, I am pleased it’s working.
The assembly process was a bit messy, I cleaned up a lot of solder blobs and accidental solder bridges. Unfortunately, I soldered/desoldered and overheated a couple of pads, removing them from the board, the result works but it’s messy. If it can survive a few knocks and keep working, good enough for now. I can always build another one.
The divider resistor values calculated in my previous post worked a charm. Rather than wasting money and time grabbing 1% resistors, I tried various combinations of 5% ones until I got very close to those values. I tried a number of test voltages from batteries and my soon-to-be-replaced power supply and noted that not only was the reading linear across a range of voltages, but along it’s scale ranges as well which is exactly what I was looking for. After calibrating to 100mV and further trimming it a hair to get it in line with my multimeter, I am pleased to say it seems accurate to better than 1% which is not only good enough for it’s intended purpose, but better than I expected.
I have earned myself a beer tonight!