Electronic Circuits Projects Diagrams Free - Blogs - DC to Daylight by unclejed613 http://www.electro-tech-online.com/blogs/unclejed613/ Electronic circuits projects and diagrams en Sat, 21 Nov 2009 16:26:27 GMT vBulletin 60 http://static.electro-tech-online.com/images/misc/rss.jpg Electronic Circuits Projects Diagrams Free - Blogs - DC to Daylight by unclejed613 http://www.electro-tech-online.com/blogs/unclejed613/ Marvin the Martian awards http://www.electro-tech-online.com/blogs/unclejed613/95-marvin-martian-awards.html Sun, 09 Aug 2009 20:40:36 GMT "I'm going to blow up the earth, it obstructs my view of Venus......"

quite often there are posts i see, that remind me of this classic cartoon line. common subjects are EMP generators, lasers (in the Megawatt or Gigawatt range), and other devices in the "infernal machines" class. usually the interest in these devices is from some type of annoyance factor ("my neighbor plays his stereo too loud", etc...)... in fact i've been known to dabble in the "infernal machine" category myself from time to time (once built a Tesla coil that blanketed the 4-story apartment building i lived in with wall-to wall RFI, and burned out every CMOS chip within 50 feet). my interest was just plain curiosity, i wanted to build one just to see it work. while i have no problem with experimenters trying stuff out to see it work, i do have a problem with annoyance driven projects whose purpose is to intimidate or exact retribution. grow up, and tell your neighbor his stereo is too loud.

fortunately, for the rest of us as well as the tinkering megalomaniac, the laws of physics imposes severe limitations on the ability for the average tinkerer to create anything that will have much of an effect for more than a few feet. EMP devices are a commonly attempted construction project, but considering the number of watts one can tap from their typical home AC supply, and the physical limitations of the components available to the experimenter, i highly doubt anyone could build something that could do much more than erasing one's computer hard drive from 5 feet away. one of the limiting factors here is the Inverse Square Law. the intensity of an electromagnetic field decreases by a factor of the inverse square of the distance. when it comes to homebrew lasers of any significant wattage, the limitations on the tinkerer are very severe. many of the materials used in making lasers are somewhat pricey. you can't just go down to the hardware store and ask for a ruby or sapphire rod. to make gas lasers is less expensive in terms of materials, but the expertise required in glassblowing, as well as the tolerences in the mirror alignment (two optically flat 1/4" diameter mirrors a foot or so apart, aligned to within a 1/4 wavelength parallelism) still place these out of the abilities of the average tinkerer.

so, when i see "i'd like to build an EMP device to shut down my neighbor's stereo" or "i want to build a huge laser to burn my neighbor's dog when it barks all night long" don't expect any helpful comments from me. i WILL however, award you a Marvin-the-Martian award, because you need to grow up and learn to deal with your neighbors face to face.
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]]> unclejed613 http://www.electro-tech-online.com/blogs/unclejed613/95-marvin-martian-awards.html <![CDATA[wouldn't an AC ohmmeter be handy?]]> http://www.electro-tech-online.com/blogs/unclejed613/92-wouldnt-ac-ohmmeter-handy.html Fri, 24 Jul 2009 03:49:00 GMT it would be nice to be able to measure impedance of an AC circuit as easily as measuring DC resistance, wouldn't it? there are many times in the audio business, when i would like to find out what the impedance of something is at a particular frequency, and i usually have to resort to some indirect method. an impedance bridge is a piece of test equipment that measures impedance, but such a beast is expensive, and is an indirect method, and a bit more complicated than putting a pair of test leads across a device and reading a number. i would like to be able to put a pair of test leads across a device and know it's impedance as a direct measurement. of course there would be one added step, dialing in the frequency i want to measure at, but i can live with that one extra step. so how to go about it?

a DC DMM ohmmeter circuit is a simple device. you have a digital voltmeter across a pair of probes, and a DC current source set to a known current. if the current were for instance 1mA, then the voltmeter would directly read 1V/kΩ, so a reading of 0.6V would be a measurement of 600Ω. simple.... i like simple, so how to do it for AC? could it be that simple? i think so. i have a function generator with a sine wave output, and a true RMS voltmeter, so how do i get a known AC current, when my FG has a voltage output? a series resistor introduces error, especially once the impedance being measured is more than a few percent of the resistor's value, so a series resistor is not the answer here.

it pays to browse the Application Notes of IC manufacturers like Analog Devices, TI, and National Semiconductor. i've learned a huge amount over the years from app notes, more in fact than one could learn in school. if you have a creative mind, you can see something almost insignificant in an app note and solve a huge problem with it (like using LEDs as opto sensors. somebody saw a little blurb about it in one of TI's app notes back in the 70's, did some experiments with it, and now it's common practice). so, while thinking about how to make an AC current source, i remembered seeing a "bipolar" current source. of course, this current source was shown with a DC input, because nobody in their right mind would ever need an AC "constant current" source (AC constant current source IS a bit of an oxymoron, isn't it?). so i did a search and found a whole app note by NS, about the Howland current source. it turned out to be EXACTLY what i was looking for, but from the text, not hardly a mention of using it for AC. so i loaded up LTSpice, drew the schematic and ran the sim using an AC source instead of DC. perfect, with 1V AC going in and a 1kΩ scaling resistor i got 1mA out, no matter what the load resistance was. stage 2 was actually building it expecting some unexpected error that would disqualify the circuit as unusable. no such error ocurred, it worked exactly like the sim (which if you have any experience building what you have run on a sim, is the exception rather than the rule). so now i have a working current source, and the scale factor is easy to set. with 1Vrms in, and a 1k scaling resistor i get 1mA out. with a 100Ω resistor i get 10mA out. i can literally take a DVM and my device, dial in a frequency, and do a direct measurement of impedance. so, shown below is an excerpt from NatSemi's AN-1515, and the circuit i used for my current source. i used a TI TL2072 op amp instead, and replaced the input voltage source with my function generator (the -2072 is a vastly improved -072).
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]]> unclejed613 http://www.electro-tech-online.com/blogs/unclejed613/92-wouldnt-ac-ohmmeter-handy.html Rtfm http://www.electro-tech-online.com/blogs/unclejed613/91-rtfm.html Wed, 22 Jul 2009 02:06:41 GMT everybody should know what this means...... if not here's a linux page with a description of this command and it's usage.........
http://www.wlug.org.nz/rtfm(1)
:D


ok, if after you read that, and you're still not sure, it means Read The Fine Manual, Read the Fun Manual, or another version not suitable for polite conversation.

working for a large service center, i see a lot of equipment that comes in for repair which, frankly, wouldn't have to if people pulled out that mysterious book that comes with your shiny new home theater system, sat down and read it cover to cover just once. and those who should read the manual are not only the consumer, but the sales staffers who guide the consumer in their purchasing decisions. two examples of this are from actual pieces of equipment that came in for repair recently one of them is from a consumer, one is from a home theater sales "tech". the first one (from a consumer adding an additional feature to their home theater setup, i.e. a second TV monitor) is the complaint on a Blu-Ray player. the customer, already having an HDMI TV monitor connected, was adding a secondary monitor to the setup, by attaching the second monitor to the component jacks (red, green and blue plugs). his complaint? no audio through the second TV monitor...... no it doesn't work like HDMI, it also needs a pair of audio cables, which is shown on page 6 of the owner's manual.
the second came from a sales floor "tech". complaint? multichannel surround receiver only has 2 channels of audio out to the speakers. the "fix" for this one was a single push of the Surround Mode button on the front panel, which switched from 2CH Stereo to 5CH Surround...... BTW, that one was on pg 12.
the sales "techs" and consumers aren't completely at fault here. engineers and marketing execs have their place in this mess too... a recent editorial in an engineering magazine was talking about the consumer electronic industry's fixation on "Feature-itis". Feature-itis has always been part of the consumer electronics industry, but for a long time, there was a very real, physical limitation on how many features could be implemented in a piece of equipment, it's called FRONT PANEL SPACE. mechanical switches and controls were limited on how close together you could put them in a piece of sheet metal, and you could see where every single one was set. there were also circuit board real estate and power dissipation issues. the more features, the more PC board real estate required, and the more packed the PC board, the more heat had to be vented somehow (and packing PC boards closer together made this difficult).with modern technology, however, there is literally no limit to the amount of features that can be installed (actually programmed is a more accurate term) into a piece of equipment. all that's needed on the front panel is a very few small buttons, and a few square inches for a fluorescent or LCD display and a window for a remote sensor. inside the unit you have a power supply, an amplifier section (i'm using a receiver as an example), and input-output boards for the signals and speaker outputs. these all take up a generally standard amount of real eatate inside the chassis.

what is new is the electronic "magic" to a) control all of the systems, interpret user input, perform signal and power switching, b)take all of the input signals and manipulate the signals, even adding effects and filtering, and c) monitoring the system for fault conditions such as shorted speaker wires, all of this continuously.

and all of this "magic" resides in an epoxy square, about 1" (2.54cm) on a side and 0.1" (2.5mm) thick. it all resides in DSP code, there can be thousands of features and settings coded into this small device, menu upon submenu upon feature settings. so many submenus and choices it's easy to get lost and forget what you just changed. you can no longer see the whole "front panel" at a glance and say "oh, i forgot to switch this back to 'tape 2'". all of your settings are hidden behind the front panel, where you can't see or remember them, and any one of them can dig you in deeper when you try to correct a mistake that suddenly cuts the sound out or makes it sound terrible. don't get me wrong, modern technology is very useful, and DSP solves a lot of difficulties that audio designers have been wrestling with for years (yes, now there IS such thing as a "brick wall" filter, and it works!!!!), but having too many features, many of them hidden in layers of submenus, is a perfect breeding ground for Murphy's Law, "If there is an option that causes a malfunction, the option will be set." Fortunately there is (and this is usually in the owner's manual near the back) always the Master Reset, which is great for getting a piece of equipment working again, but then the consumer has to start all over (but this time hopefully he Reads The Fine Manual.....)..... ]]> unclejed613 http://www.electro-tech-online.com/blogs/unclejed613/91-rtfm.html i void warranties..... http://www.electro-tech-online.com/blogs/unclejed613/82-i-void-warranties.html Tue, 23 Jun 2009 03:56:48 GMT actually, not me, since i work for a warranty service center, but i saw the t-shirt and had to post a picture of it. it says "I void warranties" and has a picture of many common screwdriver bits used in consumer electronics. if it's broke and it's still under warranty, get it fixed for free, don't open it to poke around. if it's out of warranty, and you don't have a service plan you paid for, go ahead, poke around all you like, it's already broken and you will a) find something simple like a bad solder connection, b) figure out what component has failed, c) take it to get fixed COD (take my word for it, the repair will cost less if everything is back where it belongs), or d) give up on it and toss it and buy a new one.

there may be no such thing as a free lunch, but a free repair on a warrantied item (or maybe the manufacturer can't figure it out and gives you a new one anyway) is a pretty good deal if you can resist the urge to see what made the thing tick before it broke.
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]]> unclejed613 http://www.electro-tech-online.com/blogs/unclejed613/82-i-void-warranties.html 1kW inverters for free!!!!!!!! http://www.electro-tech-online.com/blogs/unclejed613/81-1kw-inverters-free.html Sun, 21 Jun 2009 19:29:54 GMT i see (and answer) a lot of posts both here and elsewhere about 1kW inverters. my immediate answer is usually something along the lines of "there's no such thing as a free lunch". first of all do the math. 1000W/12V=83A. assuming about 15% in losses, that's pretty close to 100A. not only are we talking "heavy iron" here for a transformer, we're talking heavy copper too, since the wire used in the primary circuit needs to have negligible copper losses at 100A. you also need about 20 MOSFETs per side (of a split winding on the transformer) assuming 10A devices, and a safety factor of 2:1. that also makes for a very large heat sink. so basically we're looking for a "welding" transformer with a 12Vct @100A winding, 00ga wire (or at the very very least 2ga kept very very short) 40 MOSFETs, and a very big heat sink.

like i said above, there are 1000W inverters that can be had for free, but it takes a bit of looking to find one that works from 12V. these would be computer UPS supplies. 90% of these run from 24 or 48V batteries, but once in a while you will see a 12V one. 99% of all UPS supplies get scrapped because of sulphated batteries, and the fact it's usually cheaper to buy a new one than pay somebody to replace the old batteries. these are a good "starter" for a 1kW inverter, since the heavy iron, wire, transistors, heatsink and driver board are already there, plus it's already in a chassis with AC outlets. however once you replace the batteries, you will soon find that you can't get it to run on demand. the reason for this is that the control logic wants to see the device pluggedin to line voltage when idle. you will usually want to find this with a schematic, but there is an AC detector circuit that wants AC present, then see the AC go away before it triggers the inverter into operation. the best thing to do here is find the actual logic line that starts the inverter and put a switch there, bypassing the AC detector. every UPS is different, so this is only a generality. you WILL need a schematic to find this, unless the signal is marked on the board somewhere (try looking for a signal marked something like START/STOP, or ACDET). ]]> unclejed613 http://www.electro-tech-online.com/blogs/unclejed613/81-1kw-inverters-free.html watch out for counterfeit transistors http://www.electro-tech-online.com/blogs/unclejed613/78-watch-out-counterfeit-transistors.html Tue, 09 Jun 2009 02:00:39 GMT i'm compiling a counterfeit transistor identification guide. i've seen a lot of these in the last few years, and the counterfeiters are learning from their mistakes. these transistors are usually knock-offs of popular audio output transistors (such as the 2SA1943 and 2SC5200) or TV horizontal output transistors, or any other semiconductors that are normally in the medium-to-high price range ($5.00 US and up).

generally these devices are cheap devices bought in bulk, then have their original part number removed, and have it replaced by a part number consistent with a higher current/voltage/wattage device. for instance an audio output transistor rated at 200W, 300V, and 15A is counterfeited by taking a similarly packaged transistor (MT100 case style) that is only a 150W, 200V, and 10A device. the original part number is shaved, sanded, wire-wheeled or chemically treated to remove the original ink, or in some cases painted black to cover up the original number. the new number and manufacturer logo, as well as date and beta codes are printed on it. these then are advertised and sold as (for instance) 2SA1943's that are at bargain basement prices.

this does two things. the first thing it does is make lots of money for the counterfeiter. if he bought 1,000,000 pieces for $0.10 of a discontinued or factory reject part, and shaves and re-labels the devices for $0.10 each (total invested=$200.000.00), and sells them for a distributor for $1.00 each, he just made $800,000.00 (and if the faker makes the same deal with 9 others, he made $8,000,000.00).

so the distributor advertises the transistor for $5.00 each, which is $2.00 cheaper than the real one at $7.00 each. here's where the second part of the double-whammy comes into play. the real transistor sells for $7.00, the fake one for $5.00, and 10,000,000 of them just hit the market. well the $7.00 price tag for the real one was "what the market would bear" which influenced the $5.00 price tag for the fake one. now the market is distorted by the sudden glut of 2SA1943s, and just to make sales quotas, the distributors with the real ones have to cut their price to $4.00 each, and then the distributors of the fakes cut their price, and it's a vicious spiral downwards, causing both the distributors and manufacturer of the real ones to take a big financial hit, and also the distributors of the fakes take a big hit from having to drop their prices.

meanwhile service companies are happily scooping up the fake transistors by the truckload, installing them in repairs and charging the end user for the repair. of course the service company has at least a 30-day guarantee on parts and labor.

the happy (at first) customers take home their amps and the first thing they do when they get home is hook it up and turn it up all the way. the amp lasts maybe 10sec, maybe an hour, maybe a week, before zzzzzzzzztpoofffff, the transistors do what comes natural when they're taken beyond their limits and let out the magic blue smoke. now the happy customer becomes an irate one and demands their amp be repaired again for free. so the service company has to buy the transistors again, and complete the repair again. the customer takes it home again and zztsnap, and now there's a vicious cycle until the service company a)gives up and refunds the customer's money, or b) the service company happens to get a pair of real transistors and fixes the amp. during this process the service company may get some of their money back from the distributor, maybe not. or they may figure out that there are counterfeit 2SA1943s out there and find a distributor that carries the real thing. either way the service company has wasted a lot of money in the process.

some distributors may seek out a source of genuine parts, but not before it has become an expensive lesson to learn. other distributors won't care as long as they meet their sales targets.
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some things to do when you get a replacement part from a 3rd party source:

1)inspect the original and the replacement carefully side by side. look for slight dimensional differences.... mounting hole diameters, heat sink tab and case dimensions, pin thicknesses and shapes.

2) look for differences in print formatting, letter size, font style, logo, date code format, line thickness, ink density. (sometimes the printing on the fakes looks cleaner and nicer than on the real ones.

3)some fake print washes off with acetone.

4)look for tooling marks, scrapes, scratches, rounded edges, any signs of abrasion or erosion on the surface of the device.

5)electrical testing. check B-E forward voltage (at a constant temp) and compare against a known good one. check C-E capacitance, as this is a fairly linear approximation of the surface area of the silicon inside. again compare against a known good one. the capacitance should be within about +/- 10% of a known good one. curve tracer (if you have access to one),. a curve tracer is an almost instant go-nogo test for comparing transistors (a real transistor curve tracer that shows the characteristic curves of the device, like those shown in a data sheet)

6)destructive testing (taking the case apart to view the actual semiconductor die). this takes a hammer or large bench vise, and a lot of finesse to separate the case from the heatsink tab and semiconductor die. a lot can be seen inside of the case. some fakers just re-label a lower class device, so the die size is usually smaller. while a 3mm square die might not look a whole lot smaller than a 5mm square die, look at it's area. a 3mm die is 9mm˛, and a 5mm die is 25mm˛. this matters a lot in current density. another thing that more resourceful counterfeiters (obviously with some kind of limited foundry facilities) is put two 3mm dies on the heat sink tab and parallel them. parallel bipolar transistors have a tendency to "current hog", and eventually one of the dies burns out because it has 90% of the current flowing through it during operation.

i'll get some pictures up as i get them.


one of my "pet" theories is that semiconductor counterfeiting isn't just about the money, but possibly about undermining market competitor's reputations for quality, or worse, as a form of economic warfare of one country against another. ]]> unclejed613 http://www.electro-tech-online.com/blogs/unclejed613/78-watch-out-counterfeit-transistors.html current projects........ (finally figured how to post..... YES!!!!) http://www.electro-tech-online.com/blogs/unclejed613/77-current-projects-finally-figured-how-post-yes.html Sat, 06 Jun 2009 03:06:16 GMT i started this blog because i have a few projects i'm working on and wanted to bounce some ideas around.......

when i originally set this blog up, i couldn't find a link for posting blog entries, now i've found out how, so here goes......

1) working on a white paper about audio power amp output impedance and feedback.

2) working on a device that directly measures AC impedance the same way a DMM measures DC resistance, and does frequency sweeps and impedance graphs (and a whole lot more...). this device is a spin-off of the first project. this is the prototype and is a completely analog instrument.

3)working on a DSP based version of the impedance meter, using the DSP chip to act as the waveform generator, as well as compute the results of various tests.

a couple of projects using DSP for Software Defined Radio.

people who have read my posts will see that i use LTSpice for part of my prototyping process, as well as providing "quickie" schematics for answering questions in the forums. i highly recommend it as it is completely unlimited, no expirations, no node limits, no limit to the number of models you can add to it (only limited by the way models are written).

these projects are in the somewhat "advanced" category, and some of them are for specialized uses.

i'll also try to post some pictures of some counterfeit transistors i have run across in my business. ]]> unclejed613 http://www.electro-tech-online.com/blogs/unclejed613/77-current-projects-finally-figured-how-post-yes.html