Search found 42 matches

by analogee
Wed Jul 23, 2003 6:54 pm
Forum: General Discussion
Topic: Can MOSFET be used in PWM circuit
Replies: 15
Views: 2949

Re: Can MOSFET be used in PWM circuit

Grant,<p>Switching time I'm not all that experienced with. However, I believe Darlingtons are pretty lousy at switching, unless you were able to bring out the internal connection between the emitter of one transistor and the base of the other one (you can't, in a pre-packaged Darlington). Otherwise,...
by analogee
Wed Jul 23, 2003 12:32 am
Forum: General Discussion
Topic: Can MOSFET be used in PWM circuit
Replies: 15
Views: 2949

Re: Can MOSFET be used in PWM circuit

A healthy dose of skepticism will serve you well in electronics.<p>However, in this case, if you do know some fundamentals, you might consider that the way the schematic is drawn, there is 24 V forward biasing the collector-base junction of the BDW84. Of course, it is a Darlington, but still there i...
by analogee
Mon Jul 21, 2003 11:41 pm
Forum: General Discussion
Topic: Can MOSFET be used in PWM circuit
Replies: 15
Views: 2949

Re: Can MOSFET be used in PWM circuit

Wow, that schematic appears to have multiple errors. At least two at first glance. It looks like they are trying to do a classic buck regulator. The base of the BDW84 is grounded, which means the PWM chip can't do anything to affect it. D1 should be grounded, but not the transistor base. Also, looks...
by analogee
Wed Jul 16, 2003 7:30 pm
Forum: General Discussion
Topic: Help Please with 270ns Inductor...
Replies: 5
Views: 1373

Re: Help Please with 270ns Inductor...

Is the "RGB interface" board an encoder? Might help to know the number of the 16-pin DIP IC on the board.<p>Anyway, if so, encoders (which turn RGB video into a single composite signal) need a delay line to match the luminance to the chrominance in time; the chroma filters delay the color signal so ...
by analogee
Mon Jul 14, 2003 9:33 pm
Forum: General Discussion
Topic: TV output circuits
Replies: 3
Views: 870

Re: TV output circuits

Well, I suppose you could do worse than to pick up an old copy of Don Lancaster's classic "TV Typewriter Cookbook".<p> TV Typewriter Cookbook - available at Amazon.com for under $5 <p>Not that this book presents the easiest or most modern approach if you actually want to build this, but I think the ...
by analogee
Thu Jul 10, 2003 10:08 pm
Forum: General Discussion
Topic: RF remote signaling
Replies: 9
Views: 2012

Re: RF remote signaling

Thanks for the ideas. I especially like the walkie talkie one. The laser idea seems workable in general, but it seems I would need exceptional mechanical stability (not my forte) in the mirrors, since probably a small fraction of a degree of error would cause the light to miss its target. And, reall...
by analogee
Wed Jul 09, 2003 7:57 pm
Forum: General Discussion
Topic: RF remote signaling
Replies: 9
Views: 2012

RF remote signaling

I've got a friend with a long driveway, and he'd like a signal to tell him, in the house, when someone has entered the driveway. It'd be a pain to run a wire down there, so he'd like it to be a wireless transmitter that is battery powered (could even be a car battery he charges every few weeks or so...
by analogee
Tue Jul 01, 2003 10:11 pm
Forum: General Discussion
Topic: 2.4 GHz vs. 900 MHz Phone Technology
Replies: 20
Views: 5626

Re: 2.4 GHz vs. 900 MHz Phone Technology

We've got a Siemens 2.4 GHz phone, but never had a 900 MHz to compare with it. It is "spread spectrum", which I guess implies it is digital transmission, although one could make a case for saying that any wideband FM transmission is "spread spectrum". Spread spectrum should be more robust in the pre...
by analogee
Mon Jun 30, 2003 7:55 pm
Forum: General Discussion
Topic: Older parts - need info
Replies: 8
Views: 1661

Re: Older parts - need info

Older, indeed. Most of these numbers include "date codes" which indicate the date of manufacture.<p>For example:<p>1. 8404 => 1984, 4th week. 2. D8521 => 1985, 21st week. 3. 8417 => 1984, 17th week.<p>and so on...<p>It can sometimes be a little hard to tell what is a date code, but generally it is 4...
by analogee
Mon Jun 30, 2003 7:45 pm
Forum: General Discussion
Topic: low frequency tone generator
Replies: 6
Views: 1245

Re: low frequency tone generator

And let's not forget that your ear is MUCH less sensitive to 27 Hz than midband (500 Hz - 5 kHz or so) frequencies. Something like 60 dB less sensitive. So, for you to hear a 27 Hz tone, it will have to be a LOT louder than a 1 kHz tone.<p>Do a search on "Fletcher-Munson curves" if interested in lea...
by analogee
Tue Jun 10, 2003 12:03 am
Forum: General Discussion
Topic: most useful books
Replies: 14
Views: 2354

Re: most useful books

Well, you may be interested to know that such a device did exist, at one time; I designed a variable gain video amplifier with it. See the datasheet for the obsolete part here:<p> Elantec/Intersil EL-2082 datasheet <p>Current-in/current-out doesn't necessarily make anything easier to design or under...
by analogee
Sun Jun 08, 2003 12:49 pm
Forum: General Discussion
Topic: Wall warts
Replies: 10
Views: 2329

Re: Wall warts

I have no direct experience with Russ's comment that operating at a higher voltage will make it overheat, so I'm curious as to the reason.<p>I'm thinking that (in all of this, I'm assuming no load on the secondary; so we're talking about losses, not power delivered to a load), leakage inductance is ...
by analogee
Tue Jun 03, 2003 9:20 pm
Forum: General Discussion
Topic: most useful books
Replies: 14
Views: 2354

Re: most useful books

Okay, gotta add one of my favorites, for general purpose electronic design -- "The Art of Electronics", by Horowitz and Hill.<p> Art of Electronics Website <p>In my opinion it is the best general purpose book in existence on electronic design. When I read this book, I was sure wishing I'd seen it a ...
by analogee
Wed May 14, 2003 8:39 pm
Forum: General Discussion
Topic: LM317 and op-amp Constant Current Source
Replies: 20
Views: 3449

Re: LM317 and op-amp Constant Current Source

RonH: (caution! long, irrelevant post coming) your post provokes an interesting (well, to me anyway) theoretical question. I've always enjoyed thinking about 'duality' in circuits. You know, like how a current source is the dual of a voltage source; everything is kind of opposite, but similar -- a c...
by analogee
Thu May 08, 2003 1:39 am
Forum: General Discussion
Topic: Wir müssen wissen. Wir werden wissen.
Replies: 1
Views: 528

Re: Wir müssen wissen. Wir werden wissen.

Yeah, that's right. From a speech by, and the gravestone of mathematician David Hilbert. Not that I know a whole lot about him, but I really liked the thought expressed when I first read it.<p>Regards,
Todd