I'm happy to receive any comments, questions, suggestions, corrections, rants and raves about this page. Correspondence is equally welcome in English, German and Spanish. But I must warn you that since about mid 2009 I have no longer been able to keep up with the large amount of mail received, so I have a growing backlog of messages, each of which requires a detailed, involved reply! I fear some of these messages will have to go unanswered, and I'm sorry for that, but each day only has 24 hours, and I need some of them for other tasks than writing e-mails...
So, before you e-mail me, please read these FAQs. I will not reply to questions that are already covered in the FAQs. Under the FAQ section is my contact address!
Q: Your schematic so-and-so shows a capacitor having a value of 33n. I've never in my life seen anything like that. I only know uF and pF as units for capacitance. Is the n a typo?
A: You surely live in the USA, where nF (or just plain n, when it's obvious that it refers to a capacitance value) strangely is seldom used. Instead it is widely used all over the rest of the world. The basic unit of capacitance is the Farad, its symbol being F. This basic unit can be used together with any of the prefixes of the International System of Units, such as m for milli, u (or more correctly the Greek letter mu) for micro, n for nano, or p for pico. So, 1F = 1,000mF = 1,000,000uF = 1,000,000,000nF = 1,000,000,000,000pF. And in a schematic, often the F isn't printed because it's obvious, so you will see capacitances specified in p, n, u, or sometimes even m.
Q: Your schematic this-and-that states a resistor value as 8k2. What in the world does that mean? 8k at 2%? 8k at 2 watts?
A: It means 8.2 kiloohms. This is a standard shortform writing, which is actually in wide use all around the world, the USA included, but still some people don't know it. A 1.5 Ohm resistor might be written as 1Ω5, 1R5, or in an old and little used standard, 1E5. A 0.2Ω resistor might be written as 0Ω2, 0R2, or as 200m. Note that the R instead of the Greek omega character is commonplace, because some drawing software doesn't have the omega! And the web page editor I used for some years doesn't have it either...
Q: What's the power rating of the resistors in your schematics?
A: Unless otherwise stated, 1/4 watt is fine.
Q: What's the voltage rating of the capacitors in your schematics?
A: Unless stated, you will have to figure it out on your own! Basic circuit analysis should tell you what's the highest voltage that can appear on any given capacitor. Use a cap rated at a somewhat higher voltage. If you don't know how to analyze a circuit, using a capacitor rated for a voltage higher than the supply to that part of the circuit is usually safe. A capacitor of higher voltage rating than necessary is almost always OK too, but will be bulkier and more expensive.
Q: What's the tolerance requirement of the resistors in your schematics?
A: Unless otherwise stated, 5%. If you happen to have resistors with tighter tolerance, that's fine, of course. And any capacitors in critical parts of a circuit should be 5% too, if possible. Many other capacitors, such as bypass and coupling capacitors, are very uncritical.
Q: When trying to download the PCB design for this-or-that project, I got a broken link. Is the file missing? Could you send it to me by e-mail?
A: The file is NOT missing, but it's too large for your old-fashioned web browser to display! Right-click on the link, save the file, then open it with a good image viewer, such as IrfanView (recommended and free). Or get a better web browser.
I included this explanation in several of the texts about my projects, right where the links to the big images are, but still people ask me this question! Obviously these people don't read the text! So I have included this in the FAQs, and will no longer reply to mail about this problem.
Q: The parts list for this or that project is missing! Can you send me the parts list, hopefully with part numbers from several distributors?
A: No, I won't! You have to extract the parts list yourself, from the schematic. This will force you to spend some time on it, and that's very helpful for understanding it! Unfortunately I have found that when I publish complete parts lists, many people will just go ahead and order the parts, only to find out later that they don't have the slightest clue about how to put them together...
Q: Can you sell me a printed circuit board for this or that project?
A: No. Making PCBs is always a hit-and-miss operation with the means I have. Make your own, or have it made.
Q: Your project so-and-so doesn't include a PCB layout. Could you send it to me, please?
A: No, sorry. If there is no PCB layout published with a given project, it means I never designed one for it. I build many of my projects on universal boards, or even point-to-point wiring (dead bug style), instead of designing custom PCBs for them. It's so much faster!
Q: The component placement diagram for this project doesn't give full details, and I have no clue which part goes where. Please send me a fully detailed placement diagram.
A: Sorry, in most cases I don't make such a diagram. It takes a lot of time, and instead it takes almost no time to look at the schematic and the PCB to find out which part goes where, and in what orientation. So do that!
Q: How much would you charge for a ready, assembled unit?
A: I don't build equipment for sale, at least not at present. Maybe in the future I will. Unless you make an offer that's too good to refuse! ;-)
Q: I want to build your switching power supply, but I need it to deliver xx volts at yy amperes. Which components do I need to change?
A: I'm getting an average of 4 such requests EVERY DAY about this power supply! I cannot possibly redesign my circuits for every imaginable set of specifications. On top of that, in most cases it's not just a matter of scaling component values, but instead a pretty involved redesign is needed. So either you do it yourself, or you look for some other published circuit that meets your needs.
Q: I want to build your solar panel regulator, but my panel delivers 9 V at 200 mA, and the battery is a 5 AA cell NiMH. Can I use the same regulator?
A: NiMH cells need a totally different charge control than lead acid batteries, and the voltage and current in this case is totally different too. You cannot use this circuit, which was designed for 12V lead acid batteries.
Q: I want to build your dynamo regulator for my antique car, but this car has a 24 V system with positive ground and I have no idea how the field winding is connected. What do I need to change in your circuit?
A: You first need to find out exactly what you have, and then you need to design the proper regulator for it. This circuit is pretty specific, and is not easy to turn around in any way, for opposite polarity or for ground-tied field winding. It's easier to design a new circuit. And no, I don't have the time to do that for you, even if you are a good guy and ask very nicely!
As you can infer from the three questions and answers above, I get far too many requests to modify or redesign my projects for whatever particular needs any of my readers might have. I cannot fulfill these requests, because it would take the full working schedules of several people like me! I'm happy to make available the details about the projects I have developed for my own use, so that you can copy them, learn from them, or adapt them to your needs, but I don't run a free custom design service!
Q: I don't understand your article about this super duper project. Could you explain it in a simpler way to me?
A: No, I cannot. The explanations on my web site are the simplest I can come up with. If you don't understand them, you should start with more basic projects, or even hit the books and learn the fundamentals first!
Q: Your project so-and-so uses a devilish transformer! How dare you? Real electronicians don't ever use transformers! Can you at least give a part number for this transformer, to order it ready-made?
A: Transformers have certain specific characteristics which make them irreplaceable by other components, without loosing performance or increasing complexity. And they are actually easy to wind and use! And no, I cannot give you supplier parts numbers for ready made transformers, when I designed and wound a transformer for one of my projects. The only transformers you can buy ready made are the most common ones, such as power transformers for standard voltages and currents, at line frequency, and a few types of audio, RF and pulse transformers. Almost every other transformer must be custom-wound. I normally give the necessary information about the core, wire sizes and number of turns, and my web site has an article on transformer winding. So you have no valid excuse for not winding your own transformers.
Q: Your project calls for a TL062 operational amplifier, but my local TV spare parts store doesn't carry it. It does carry the TL072, so I used that one. It's an operational amplifier too, the number is real close, and it even has the same pinout, so it ought to work, right? But my circuit doesn't work! Could the reason possibly be the operational amplifier?
A: You bet! You cannot simply replace one op amp by another, and expect it to work. There are thousands of different op amps, and some cross-replacements do work, others do not, or work poorly. Unless you know perfectly well what you are doing, don't do such replacements. When replacing op amps, you need to look at the voltage supply range, the input common mode range, the input differential range, specially check if the input range includes or even exceeds any or both of the supply rails, also check the output drive ability and the range covered by the output voltage, then the compensation, the gain, the gain-bandwidth product, the slew rate, the noise, the distortion, the offset voltage and current, the stability of the same, whether or not the inputs are clamped together, the power consumption, and about two dozen more parameters. It's common practice to replace one op amp by another, but really you need to understand what you are doing. If you don't understand all the details of an op amp's specifications, and the requirements of the circuit, then you better use the exact op amp, even if you have to mail-order it.
Q: Where can I buy all the parts for this or that project?
A: I live in Chile, and I might be able to tell you in which Chilean electronic parts store I bought each part, but that won't be useful to you if you live in China, the USA, Malaysia, Poland, India, South Africa, Australia or who knows where. I have no idea about the electronic parts stores near your place. So, first find the electronic parts stores in your city, or the nearest bigger city, or a really large city, then find the big electronic part distributors in your country that operate by mail, telephone, internet, fax, etc. If that still doesn't help, then look on the web for Digikey, Mouser, Farnell, RS-Components, Conrad Electronic and all the other big distributors of worldwide renown. In many projects I use Amidon magnetic cores, which can be mail-ordered directly from Amidon. That's actually the main reason why I use them! Other brands' magnetic cores can be pretty hard to get.
Q: I built your XYZ-design, and it doesn't work! Are you sure there is no bug in the schematic?
A: Yes, I'm pretty sure there is no critical bug in any of my schematics, because I draw the schematics WHILE I build my projects, and not AFTER finishing them. There can be minor bugs such as doubled up or missing component references, but nothing that would affect the function of the circuit. Most of the projects on my site have been successfully copied by many people, so those schematics are proven correct. Still, if you are pretty sure you found a bug, tell me, but it's quite unlikely. If your version doesn't work, the most likely reason is that you made some mistake, or even that you got a bad component.
Q: What can I do if I build one of your projects, and absolutely can't get it to work?
A: First, try to make sure that you UNDERSTAND the circuit, before building it. If you don't understand it fully, it's very easy that you will do some little silly mistake that renders it inoperative, and you will never find that mistake. Also, make sure you get good parts! It's not unheard of that someone gets a dead part, even from relatively well reputed stores. Also be aware of the infortunate fact that the world is being swamped in counterfeit parts, mostly coming from China, which are not what is printed on them! Typically some crook will buy many thousand ultra cheap, unmarked small transistors, print "2N2222" on them, and sell them at 2N2222 prices, even if what's inside doesn't get anywhere close to 2N2222 specs! Very common parts like 2N3055 transistors are very often fakes nowadays, and even the more specialized parts are being faked quite often now. So, try to buy parts ONLY from well reputed distributors, and always be prepared to test a part to know if it actually is what's printed on it! And if you get a fake part, return it and firmly ask your money back. It's the only way to try and stop this kind of crime.
And if you absolutely can't get the circuit to work, contact me and tell me exactly what's happening. Also tell me if you have an oscilloscope, or if you are working blind, with a multimeter only. I will then probably ask you to do some specific measurements, and with the results I might be able to pinpoint the problem.
Q: Have you heard of the latest incarnation of the Perpetuum Mobile ? Undoubtedly you should be able to build it!
A: Hundreds of wishful people have wasted my time by contacing me about matters related to "free energy", "magnetic generators" that don't consume input power, over-unity devices, water-powered cars and the like. Please, don't! If you don't know enough physics to understand the principle of conservation of energy, that's YOUR problem, not MINE. It's not my duty to explain this to you. Please hit the books. And if you don't believe that established physics knowledge is correct, and you absolutely want to waste your time and money building miracle machines that run and produce power without consuming anything, you are free to do so. People have been trying that for many centuries, and nobody ever got any success. I only ask you to not waste MY time on such nonsense.
Q: Why are you so negative about electric cars? Do you have stock in the oil industry?
A: I'm not being negative, just realistic! And also a bit frustrated. I would so much love to own an electric car, that works at least as well as my old gasoline stinker, and is less expensive to own and operate. But alas, there is none! All electric cars one can buy either have extremely limited performance along with quite high cost, or extremely high cost along with still rather modest performance. If anybody can tell me about an electric car that is able to carry me from my home to the nearest city and back on a single charge, along with my usual supermarket and home improvement store purchases, with acceptable comfort level, and that is no more expensive to own and operate than my 20 year old gasoline stinker, I will buy it on the spot!
And no, I have no stock in any oil company. But I have no stock in electric car or battery manufacturing companies either.
If you have a comment, or a quick, to-the-point question that isn't covered in the FAQ section, I will probably reply quickly too, but if you ask me to do a custom redesign of one of my projects to adapt it to your specifications (many people want just that!), or if you ask me to explain again something to you that was already explained in one of the web pages and you didn't understand, that mail may go unanswered! And if you send a note just telling me whether you like or dislike something, I will gladly read it, take it into account, but might not reply, unless I have something important enough to comment.
If you e-mail me, please make sure that the return address specified in your address header actually works, and that your mail server doesn't block mail from all addresses that haven't been previously authorized! It happens too often that I write a lenghty reply to someone, only to see my reply returned as undeliverable, because it was considered to be spam by some filtering software! That's very frustrating both for me and for the person who waits forever for my reply. At this very moment I have such undeliverable mail waiting for:
Mike Baxter, Bill (WA4KFI), Norman Platts, Sydney Mulenga, Greg Taylor, Joey Ferrer, Jacki Brook, Kiran, and Paul Noonan
If you are among these, please tell me some alternative e-mail address where I can send my reply to you!
If you need to send me an attachment, please make it small! I live in a rural place, and use a cellphone internet connection, which is very slow and unstable. An e-mail with a three megabyte photo attached will totally lock up my connection, and I will have to delete it on the server, without a chance to even read it. The maximum size of e-mail I can reasonably download is about 200kB total, including all attachments.
And please do not send commercial offers and similar things. As a matter of principle, I never buy anything offered by unsolicited e-mail.
And now comes what you were looking for, so desperately: My e-mail address is , and my name is Manfred.
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