Over the last couple days, I really sat down and sorted a couple of things that were unknowns. Either I had forgotten why I designed it that way on the schematic or had only roughly figured it out in the first place. One was the flashing LEDs from the last post. I had subsequently tried other resistor values for different effects, but in the end stuck with the 1.5kΩ one. I did like the blanking and hopefully it will be a nice effect once i have it all assembled. I can always change the resistor later if I wish.
Tag Archive for electronics
I’m trying to keep going and have some bench time every day to keep things going. So far, so good.
I figured the next bit to sort was how to move the decorative flashy LED feature over to the 12V rail. As mentioned before, I want to keep the 5V side exclusively for the clock and digital logic so it keeps its time when I unplug it (provided I have a 9V battery in it of course).
It’s been a long time since I’ve written anything about… anything. As always, I’m happy if anyone finds the information here useful, but I don’t expect anyone to read it really or give a toss. Really use it as my open lab notes which I refer back to when I take these long breaks to remind myself just what in the hell I was doing!
I have a fairly good memory. To the surprise of some I can recall conversations verbatim from twenty years ago… but I know the instant I say “oh I won’t bother noting that, I’ll remember for sure…” is the moment that said information is forever wiped from existence, never to be seen again. One such, happened when I revisited my Nixie Clock project which I’ve been working on since… 2012 probably?
Institutionalized Dumpster Dive
Over the weekend, I had occasion (in other words I made an occasion) to visit A1 parts and surplus in Etobicoke. I have mentioned it before as a candyland for the junk enthusiast and this is essentially correct. Despite its remote location, it is well worth the visit, just be prepared to dig and expect no help from the rather cantankerous guy at the counter. Total comic book guy for the electronics store which I find endearing rather than offensive. Anyway, if you ever end up there, be prepared to wade through tons of unsorted junk, find a few gems, and score a few surplus deals.
Or how I just love to overcomplicate things
Lights, buttons knobs and dials have always fascinated me. In fact, it says so in my baby book pretty much exactly. I think that was genesis of my love for technology, electronics, sci-fi and general science and nerdom. After all, what could be cooker then “techy shit” as gmunk puts it?
With every project I do, I tend to dream up ways of making the interface and functionality as flexible (read: complicated) as possible. I want to feel like I’m flying the frickin’ Enterprise when I do my thing.
Just a quick test and a quick solution
Had a few minutes to just check up on why the load would change when the voltage does. A simple test of trying a higher voltage power supply seemed to do the trick. Stayed within 10mA of where it should, and probably did better than that, but my multimeter can’t measure that. The new power supply is a 200mA 12V wall wort which is very unregulated. I measure 16V off the bugger with no load. Makes me wonder if what is printed on the box is merely a suggestion. Still, nice to have the headroom. Now the opamps have enough swing to really kick that MOSFET into regulating the current flow reliably.
Improvements and fine tuning
As mentioned in my last post on the dummy load, though I am very pleased with the results, there is always room for some fine tuning and improvement. Also, some parts needed to be bought. First off, here’s a revised version of the schematic:
Some quick tests work out quite well
Had a tiny pocket of time with which to test a few things with my aforementioned dummy load I just build. In looking through my collection of junked wall wort power supplies I found a low power one, a 9V 210mA. I wanted to check and see if the voltage headroom for the opamp would be worse. As it turns out, the stated 9V is actually 11.3ishV but whatever. I knew the supply would only need to deliver a few milliamps so I ventured to see how much exactly.
The dummy load returns and I do some cooking
I do very much enjoy watching youtube channels on electronics. It has probably been the single most instructive resource for me and led to real understanding of what I am actually doing.
Some time ago, I watched Dave Jone’s excellent episode on building a constant current sink – a “dummy load” which is an essential piece of test gear for testing out power supplies. So much less fiddly than messing with loosely spec’d power resistors, I had always had the intention of building one but never quite got around to it.
Cor blimey I nearly blew my head off. Shorting capacitors, particularly large ones is a very scary experience. I had removed the rectification board from the mains board of the power supply project. Read more