For those of you who actually look here, and I’m thankful for all that do, you may have noticed a rather drastic change in colour scheme and an entire redesign of the home page.
Archive for techmission
There are always a lot of myths floating about … about Macs and about malware. There always seem to be two camps with diametrically opposed positions. Some hold on to the rather antiquated “Macs can’t/don’t get viruses” which is inaccurate, and in fact never was accurate at any point in time. The other camp is claiming with each new news story that it’s the thin end of the wedge and soon OSX will be as much of a helpless victim as Windows always has. This is also incorrect, and probably not true of Windows any longer either.
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.
A simple build for much peace of mind.
I recently came across a new (to me anyway) electronics youtube channel presented by one Peter Oakes. I love collecting these channels, many great designers out there and lots of good information to absorb. I may do a post just on my favourite ones in future. Anyway, he is making both a power supply and dummy load so I ventured through his videos to glean lovely pearls of wisdom.