Re: International standards (2023 Update)

ah, the days of ECE290. I'd suggest looking around for course websites for "Computer Engineering I" or similar; I happened to find this at Rice with a little googling:

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Franklin M. Siler    UIUC: Undergraduate in Electrical Engineering
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10A102G RES NETWORK 10B 1K 9RES 2%

Reference to

for the 8B331G though it could also be an RC terminator network. Hope your beter at German than I am.

for

can

I want to build the one I worked out for myself, not just copy another design. I'm doing this to practice/learn how to, as much as to have a working system.

and mine has 2 chips to your 3, so nerrr. ;)

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Get a variable load like headlight bulbs and keep loading it up till it gets hot after several hours so the temp will stabilize.. If you can comfortably hold your hand on it you've found a load that it'll be happy with and should work for years. Remember that half wave vs full wave recitifiers will have double utilization factor.

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You would be better off to mount a rather small fan on the end of a shaft, then drill a suitably sized hold at the stern of your boat, take proper steps to prevent water from leaking around the shaft, and connect the shaft to the motor in the belly of the boat. Make sure the fan remains under the surface of the water and rotates such that it is pushing the water backwards. This arrangement would be more compatible with Newton's laws of motion, since the fan would be pushing against the water rather then blowing air into the sails.

Good luck!

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Fair enough...

I assume you've double-checked that your 4538 (and other) connections are wired up exactly as intended? And that the chip is inserted with correct polarity! Have you swapped it for a fresh 4538, with same result? Have you used the 4538 in a basic test circuit to check it's not already zapped?

BTW, I got this message on trying that JPG link: ==================== Notification Too Many Users There are more clients using this WebWasher than your license allows. Please upgrade your license to support more users.

-------------------------------------------------------------------------------- generated 11/Aug/2004 10:00:39 +0100 by bncfms04 (WebWasher 4.4.1 Build 1003) ====================

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Terry Pinnell
Hobbyist, West Sussex, UK

Thanks Dan,

Looks like I need a little more research and study. I will look into the regulator issue and try to find the book you mentioned.

The alternators are the same and will be driven off the same belt so they will be in sync. Sounds like I should let them gen DC and then invert instead of the complicated disconnect of that alternator function.

Thanks again Jay

I have hand-wound hundreds of power transformers for personal use, and

*NEVER* had to worry or compensate for "copper loss". Never ran out of window space, either. Now core loss is someting that cannot be avoided, but can be safely ignored for 50W and higher power transformers (small percentage of core rating).

Sorry, that's my careless description. There's only *one* primary, tapped in the familiar way (presumably to accommodate mains in the range 220-240V, although there are no markings). I simply measured the three combinations, and used the full winding.

orange o---------o | C| C| 4.5 ohms brown C| o---------o C| Total winding 47 ohms C| C| C|42.5 ohms C| C| C| white | o---------o

created by Andy´s ASCII-Circuit v1.23.080803 Beta

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Terry Pinnell
Hobbyist, West Sussex, UK

Thanks, but I mentioned what IMO is the snag with that up-thread in Message-ID:

I've since implemented the alternative I suggested. Currently (sorry ) I have the secondary delivering 2.2A (an arbitrary first choice), while I monitor transformer case temperature with my DVM.

But I still don't see how even a protracted series of such tests is going to tell me with any accuracy what I can expect using DC loads at various voltages in the range of my supply.

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Terry Pinnell
Hobbyist, West Sussex, UK

Ah! Ok now, thank you.

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Tony Williams.

Yes

Yes

No - need to get another one.

It was working before, so don't see the need for that.

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I read in sci.electronics.design that Robert Baer wrote (in ) about 'Estimating transfomer current rating?', on Wed, 11 Aug 2004:

Your windings have zero resistance? Maybe you are using a different definition of copper loss than I^2R?

This depends on the ratio of window height to limb width. For scrapless and even semi-scrapless laminations, the copper loss considerably exceeds the iron loss if proper allowance on maximum induction is made fro high mains voltage. With modern silicon iron, an iron (hysteresis) loss of 5 W/kg at 1.5 T is typical.

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The good news is that nothing is compulsory.
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I read in sci.electronics.design that Terry Pinnell wrote (in ) about 'Estimating transfomer current rating?', on Wed, 11 Aug 2004:

If you are using a series regulator following a bridge rectifier with a large filter/reservoir capacitor, the a.c. secondary current will be between 1.6 and 1.8 times the d.c. load current. It has a peaky waveform, so you need a true r.m.s. meter to measure it, or use your scope. The waveform is close to repeated half-cycles of a higher frequency than 50 Hz, maybe 150 Hz, interleaved by zero-current periods. So you can take the r.m.s. value as the peak value divided by sqrt(2) and then divided by the ratio of the duration of the pulse to the whole half-period, i.e. 3, if the pulse looks like 150 Hz.

The load voltage is irrelevant, because the rectifier always produces the full voltage across the capacitor.

All you need to check is that the transformer doesn't get too hot with the maximum current you want to draw from it.

--
Regards, John Woodgate, OOO - Own Opinions Only. 
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

The rms current values in the secondary winding are directly substitutable. The 1.8 relationship of RMSin/DCout is typical of capacitive rectifier filters with 15% ripple.

Theres no reason why you couldn't bodge a capacitive rectifier-filter onto your winding as a test load.

When shopping for suitable junk transformers, it's often wise to take a meter or two and scrap paper with you.

L values give turns ratios. R values give first-order current-generated rises.

Otherwise, why not think of other uses for those extra windings? While neccessity may be the mother of invention, opportunity or incident is it's father.

RL

I've had time for testing the isolated secondary at only two loads so far, but here are the results. The temperature measurement was with the miniature sensor that comes with my DVM, taped to top of transformer. Case was open though.

Time Load (A) Temp (C) V (AC RMS)

---- -------- -------- ----------

11:03 0 25 25.4

11:03 2.20 25 22.0

12:00 2.18 42 21.9 OK to hold.

12:03 2.92 42 20.6

12:50 2.87 53 20.4 Too hot to hold

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Terry Pinnell
Hobbyist, West Sussex, UK

Thanks. Must that be done with the transformer removed from the large metal case of the power supply? That can get too hot to touch and obviously heats up the transformer too. But if the 'hand test' is done with the transformer removed, and a maximum current thus empirically determined, then how reliable is it for regular use, when the transformer will be heated by the hotter case? That's the 'snag' I referred to.

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Terry Pinnell
Hobbyist, West Sussex, UK

I have two different types of cubical heat spreaders. There is a Sn/Pb plating layer on each surface of heat spreader. Heat spreader A with 7 micron plating layer thickness. Heat spreader B with 0.5 micron plating layer thickness. If both heat spreaders have equal heat conductivity characteristic, will the one with thinner plating layer be having solderability problem? If so, how the thickness of Sn/Pb plating layer is related to solderability? I worry that the thinner plating layer will pose the solderability problem and reduce the heat transfer efficiency.