Hardware theory...

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Re: Hardware theroy...

Postby UAirLtd » July 21st, 2011, 9:05 pm

CodeJunkie, I agree with k-ww. The majority of manufacturers of ICs supply a recommended circuit either in the datasheet or application notes, which will tell you the type and value used for capacitors. These values do not necessarily tie in with the theory (and in many cases you won't get enough information to calculate it).

For example, the datasheet for the LM7805 linear regulator converting 9V to 5V says to use 0.33uF for input, and 0.1uF for output. Although the notes in the datasheet also implies that the output capacitor is not absolutely necessary for it to work, it'll just work better with it there.

From a practical point of view, you probably don't want to have to buy every single capacitance value that a datasheet might suggest you use, so knowing a bit of theory would let you make an educated guess as to whether it's ok to use the nearest higher or nearest lower value as a substitute.

My advice to you is to learn the theory if you can, but don't get too hung-up about it (unless you're doing precise oscillators, or filters, or power circuits), and go with the datasheet recommended values
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Re: Hardware theroy...

Postby CodeJunkie » August 5th, 2011, 6:21 pm

machinelou wrote:Sorry, this has been killing me. If this thread needs to stay a sticky, can someone please fit the title so "theory" is spelled correctly. Thanks


Fixed. You should see me try to spell without spell check...
Thanks for all of the replies guys and gals :D
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Re: Hardware theory...

Postby n0lkk » October 23rd, 2011, 9:29 pm

You may or may not find this site helpful http://www.allaboutcircuits.com/ Don't forget to search at you tube. I have been placing the Navy Electricity Electronics Technical Series modules on http://www.archive.org search for neets, and while you are there also search the video section for army or navy training videos on the subjects. Also doing a web search for neets should find where you can read the modules online. I have to admit I don't have all the modules loaded up to archive.org yet. While the why is under too much information, the last time I tried a marathon session, I ended spending 3 day in hospital. Hope this helps some a little.
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Re: Hardware theory...

Postby MrHusic » October 24th, 2011, 5:19 pm

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Re: Hardware theory...

Postby KillerBug » August 8th, 2012, 5:52 pm

Capacitors can make great timers too; I use a 0.1uF capacitor to time the pulses from a 555 in my PWM fan controllers. It charges up to a digital 1, triggers the circuit, gets discharged to a digital 0, and repeats. I can speed up the rate with a smaller cap, or slow it down with a larger cap; to me it is an analog electronic hourglass. Somehow I doubt this is what they imagined capacitors would be used for when they were first created, but it works great. Of course I also use them for power regulation on sensitive circuits and with inputs that are not regulated.
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Re: Hardware theory...

Postby Osgeld » August 8th, 2012, 8:42 pm

They make ok timebases if you don't need high accuracy, but they tend to float with temperature, and the tolerances are not very tight
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Re: Hardware theory...

Postby n0lkk » October 18th, 2012, 11:33 am

I have found associating animation with another search term is helpful in finding animations and videos showing how something works i.e. [ animation inductor] . While inductors , and capacitors can be useful in DC only circuits, it's in AC circuits than they really do a lot of work for us. Reactance is a resistance to AC current, capacitors, and inductors are reactive components., In AC circuits, they resit current flow in a manner they do not in DC circuits. Radio Waves are AC, in radio transmitter, receivers is where capacitors do a lot of magic for us. For excellent printed material on the topic go to http://www.archive.org and search for neets, I have uploaded most of the Navy (USA) Electricity Electronics Training Series to there.
http://www.allaboutcircuits.com/videos/index.html
http://electricalway.blogspot.com/2011/ ... jw/AC.html
Those are a few of many
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Re: Hardware theory...

Postby bvc11 » July 15th, 2013, 9:57 pm

wow,loads of info,really benifit me a lot.thanks for your info,I think this will solve a big problem of me :P
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Re: Hardware theory...

Postby mgingerich » August 18th, 2013, 5:53 pm

If you're using a capacitor for "smoothing" a power supply, in my experience you can't have too much capacitance: bigger is generally better. The main reason capacitors exist in specific values is for tuned LC circuits, which use a capacitor and an inductor. These have a resonant frequency determined by the values of the capacitor and inductor. They are extremely important in radios, oscillators, tesla coils, etc. Wikipedia does a pretty good job of explaining them: http://en.wikipedia.org/wiki/LC_circuit
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Re: Hardware theory...

Postby Mjolinor » August 19th, 2013, 2:00 am

Except that the bigger it is the more is the inrush current and if you go too big you fry the first stage of the PSU when you plug it in.

Swings and roundabouts, a happy average is what solves most things.
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