I assumed (just to simplify) that motors run 4 times slower then I thought that if heater gets 4 times less Wats and gives 4 times less power to air than the balance can be at the close temperature to the original situation so heater positive temperature coefficient can be ignored. But I think in real the temperature will be lover so (thanks to that coefficient) the relation of motor speed to heater power will be higher so temperature lover so relation higher and so on…
I’m not sure but it is possible that temperature was still too high and my brother used diode in serie with that all.
My association with what you said about motor in series. I think it was in 1986 when I was first time in my live in West Germany. I had everything paid by University, and also got some money but having in mind that those time my salary was $13 per month, everything (even battery) seemed for me very, very, very expensive there. If it were not my first visit there then probably I would think a little different but it was first time. I had Zenith camera with built-in light meter and just then that light meter small coin battery refused to work. I recharged it a little using hair dryer and pocket knife - the only tool I had. I connected that battery for a while in series with that motor (motor gets DC). I had too few hands so I had to ask my colleague for help at a critical moment when I was keeping everything at right places and someone had to switch it on for a moment.
Temperature may well be lower or higher depending on a lot of factors. Heating elements are very much non-linear devices when it comes to resistance at high enough temperatures and temperatures themselves are highly non-linear respective to air flow. Air flow is non-linear to motor speed and motor speed is not linear to voltage.
Yes I guess the key is that if the voltage is too low for the fan to overcome friction, it is conceivable (maybe not so likely) that the heating element could run hotter. I think the heating element may often be connected in series with the fan so the heating element might be able to “hog” the voltage.
I once tried something like that with a button cell.
I’ll call it “flash” charging…it went flash and then bang. Absolutely amazing how much mess one of those little things can make.
Not loaded DC motor speed is linear to voltage. I also suppose that with low motor speed the air flow is close to linear to its speed.
So I assume that with 1/4 voltage motor is more effective (not seriously loaded and still with liner speed to voltage) than with full voltage. As it is more effective I suppose temperature will be lower.
May be with 1/40 voltage it will even not start so will be not effective at all.
No. The help was only needed because (as I have written) I had too few hands to master it all. It was rather old air dryer (looking from nowdays) and construction was easy to disassemble, but I had to keep that battery somewhere inside between some wires I disconnected (probably they were mounted with screw) while I needed the power to be switched on for may be around 15s. It was enough for that battery to work then for several months.
You probably wonted to charge it too fast
In the 80’s it was standard here (at least among electronics students) to charge not rechargeable batteries. I had special tool to it made of wooden clothespin + two pushpins and AC 220 plug (rectification + current limiting in that plug).
I had an acquaintance (fellow D&D campaign player) who used to work at a power plant in Pennsylvania (Limerick nuclear power plant, but I doubt the power generating technology was important to his story). He would tell (maybe still tells, I’ve lost touch with him) a story about one day he went to work putting his watch on out of habit even though he knew the battery was dead. He normally walked on a path that went between the power generating building and the local substation, but that day he noticed that his watch started working after walking that path… He decided that EM fields strong enough to partially charge his watch’s battery wasn’t something he wanted to expose himself to on a daily basis so after that day he avoided that path when he could.
Battery dead at room temperature wormed by body can be a little less dead an watch can start working (for a limited time). I don’t think watch can demodulate AC EM field to charge a battery, but who knows…
May not be able to charge a battery but there is a slight chance to harvest energy via an inductor. As far as I know watches contain such inductors which I know from countless disassembled watches in my childhood. Also watches work with pretty low energy levels. Because of that I think that story is “plausible”
My Dad was not an EE, but he used to think that beaming electrical energy was a technology to come. I think of a number of things:
Amateur radio operator as a kid and “too much RF in the shack.”
While it might be technically possible you may risk frying every living thing and conductive device around the target device.
I know now that a lot of work has been done on wireless charging. But whatever we have these days (that I am aware of) relies on relatively close proximity. Such as putting your phone onto a charging mat. For electric cars can wireless chargers couple across maybe a few cm?
I mostly agree with Piotr. But it turns out that it is not so difficult for joined dissimilar materials to rectify. So the explanation of rectifying stray fields sounds unlikely but not impossible.
I moved to Minnesota in 1976. A big item in the news for a few years was a 750 KV DC transmission line which was being considered. Farmers complained about “stray voltage” affecting dairy cows. Sounds like nonsense but I think it was poor choice of words describing some actual phenomena. There was also the possibility of corona discharge electrifying a metal roof on a nearby barn for example. Weird stuff…
Mediser … doing well thanks … hope all is well in your neck of the woods. Honestly, business has slowed down much like the 2009 budget crunches. No worries, I agree with your suggestion, simply take the opportunity to do things that have taken the back seat for too long. When business slumped the end of June (investors got cold feet, claiming virus wows), rather than look for more work, my son and I installed the three decks that the house was missing since the house was build in 2015. Also installed some flooring, sauna, landscape rocks, etc. After all that, electric design work just popped back up, so working EE again, missed it )
Also did some tinkering with a toy idea. Got it working. Partner presented it to two big toy companies last week, and received positive response. So I will now package it for demos next week.
Frankly, finding new EE projects is the hardest thing that I do. While most clients do bring me repeat work, my new clients end up being referrals mostly vs completely new clients that I find.
If you have any pointers for me to ID new clients without referrals, I am all EARS )
