Last week, I finally got a few parts I was waiting for. Namely the insulating pads that allow me to connect the MOSFET to the heatsink without making the entire case the drain! So with that, assembly is complete. Just need a label for the front which I can do at a later date if ever I make it to Staples to buy adhesive transparency sheets.
Properly mounted MOSFET. Note the pad under it, and the nylon bushing isolating the screw
No, that’s not a euphemism.
Recently, I purchased a new multimeter, the now widely used UNI-T UT61E, which as far as cheap chinese multimeters go is pretty darn good. After watching various teardowns and tests courtesy of Mr. Martin Lorton, I was actually reasonably impressed with the functionality and accuracy of the meter and really wanted one to replace my Mastech “shitty piece of shit” meter which I’ve grown to loathe over the years. Most annoyingly, it had stopped displaying decimal points almost entirely. An internal inspection revealed it to be the switch contacts not quite making contact on the volts ranges (which is… the most important range!). This led to some almost-accidents as I had to guess where that decimal point would be. Is it 2V? 20V? 200V? Bugger this, time to upgrade and get a decent meter. Not that I won’t use the Mastech still, always good to have two meters, and the Mastech measures temperature which the UT61E doesn’t.
It’s been a week of tweaking and assembly, mostly. This is both the part I love the most, and dread the most. On the one hand, it’s awesome to see the project come together and not just be a dangerous collection of bits on my bench. On the other hand – drilling into aluminium is such a chore!
Anyway, here it is thus far:
Front panel view, not perfect, needs labelling, but good enough!
As I said in my last post. I am mostly happy at how the Loaded Dummy performs, but with the caveat of some inaccurate voltmeter measurements.
After some more tuning and testing, I’ve identified two issues that leave the project just shy of my expectations. Neither are deal breakers, but are enough to make me want to investigate further and see if I could improve if not solve them.
Bit of a rats maze, but she works! All the bits are built.
For the past week and change, ever since getting my boards from the fab in the post, I’ve been assembling and testing and fiddling with my dummy load project. I outlined a few beginners mistakes in my last mention, and since, I’ve disovered a few more! Don’t worry, it still works fine enough and I’m still generally pleased with it. I’m even laughing at the absurdity of the bugs I’ve found.
Anyway, here’s the state of it now:
All the bits waving in the breeze, but she works!
Hurray! I got my PCBs via DHL this morning. So happy to receive them and hold in my hand my first professionally made PCB.
Digging up an older idea to fill a newer void
Buzzing along my electronics wave, hot off the success of my nixie tube clock, and dummy load projects, I looked at what else I had going on and found that several of them were in need of panel meters, something I’ve had a really hard time finding at a decent price. You’d figure in this day and age they’d be easier to acquire, not harder.
Anyway, so I dug up my original idea of using an ICL7107 based 7-segment panel meter. I always loved this idea, mainly because I love meters but in particular I love LED 7-seg displays over LCD just for readability and sheer cool factor.
My earlier attempt at a panel meter
Well after humming and hawing, I finally just pushed the button on the dummy load project and ordered the PCBs from JLCPCB (via EasyEDA). I figured I can’t go too wrong, it seems most electronics youtubers seem to like it fine. I think the only thing that could go wrong is I made some mistake on the PCB layout, though I did check it over three times. You never know, Murphy might show up. Still, either way it will be a learning experience and if this works out (as it likely will) I will have more boards made up. I find this all very exciting!
Here is the layout I sent them:
Completely re-done from yesterday, includes the 12V supply
Now that I’ve got my Nixie clock all ready to be housed in a box, and lacking said box, I figured I’d motor ahead and try to get something else going. Next on the list is the Dummy Load, which has sat on a breadboard gathering dust for 3 years now. Funny thing is, I had figured it ready for assembly, but always good to check it out and see if improvements can be made.
To my surprise and delight, my design is working just fine.
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.