---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sat 02/26/11: 9 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:43 AM - Re: coil tuning anyone? (Dan Billingsley) 2. 10:14 AM - Re: coil tuning anyone? (Robert L. Nuckolls, III) 3. 12:33 PM - Re: AOA circuitry (user9253) 4. 01:57 PM - Re: PM capacitor inrush (Jan de Jong) 5. 01:58 PM - Re: Re: AOA circuitry (Jared Yates) 6. 03:45 PM - Re: coil tuning anyone? (Dan Billingsley) 7. 06:01 PM - Re: PM capacitor inrush (Robert L. Nuckolls, III) 8. 07:39 PM - Re: Turning simple-ideas into working hardware. (Robert L. Nuckolls, III) 9. 08:09 PM - Re:hi!5c (leesafur@aol.com) ________________________________ Message 1 _____________________________________ Time: 05:43:48 AM PST US From: Dan Billingsley Subject: Re: AeroElectric-List: coil tuning anyone? Bob, Thanks for the reply. My equipment is at school so I will send the make and models to you Monday. Below I attached the link to where I got the plans. We are making our search coil at about 12" diameter. I know if I followed the sizes they gave it would come out fine, yet I would like to teach the kids how to do coil tuning. In my electronics I class we wind coils to make crystal radios and it would be good to cover tuning here as well. If you have any suggestions on what might make the following project work better, I'm all ears. http://www.easytreasure.co.uk/bfo.htm Thanks a Bunch for taking a look! Dan ----- Original Message ---- > From: "Robert L. Nuckolls, III" > To: aeroelectric-list@matronics.com > Sent: Fri, February 25, 2011 8:48:27 PM > Subject: Re: AeroElectric-List: coil tuning anyone? > > > > At 09:29 PM 2/25/2011, you wrote: > > > > > > > I have found plans on building a simple BFO metal detector. I will have them > > making their own PCB's and constructing the entire project from raw >materials. > > The area I am needing help with is tuning the coils. They should be wound to > > match as close as I can get them so the fine tuner will be effective + or - > > 250hz (the frequency target is 100khz) > > > > > > The tools I have available to me include an oscilloscope and a function > > generator...the questions; > > What are the make/model of your test equipment items? > > > 1. Do I have what I need to assist / measure my coil windings to get them in >the > > frequency ball park? > > There are coil winding calculators all over 'net. > I presume your plans call out the electrical size > of the components. Can you scan the schmematic and/or > point me to a link where you might have downloaded it? > > > 2. Would someone be kind enough to give me a clue how it is done? > > Not a problem once we fill in some numbers. For example, > A 10" search coil wound of 104 T #22 wire will yield > about 5.4 mH. Parallel this with a 470 pF capacitor and > you find the thing resonates around 100 KHz. The fixed > oscillator coil might better be a purchased item. It will > need a LOT of wire in a small space to get into the 5.4 mH > class of inductor. Do your plans call for any torroidal > inductor cores? > > > > Bob . . . > > > > > ________________________________ Message 2 _____________________________________ Time: 10:14:32 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: coil tuning anyone? >If you have any suggestions on >what might make the following project work better, I'm all ears. >http://www.easytreasure.co.uk/bfo.htm > >Thanks a Bunch for taking a look! Hmmm . . . what's the 'lesson plan' for this endeavor? You mentioned having students lay out an ECB. Is this a paper exercise or are you planning on fabrication as well? This is a complicated project (read high risk) for a class-room exercise. The device is rich in simple-ideas (physics) each of which presents an opportunity for teaching. At the same time, it takes only one solder joint, one bad component, one wiring error to 'disappoint' even the most interested members of the class. Without a solid personal understanding of that which you hope to illustrate and demonstrate, your own ability to trouble shoot and fix a defect offers risk for this being more of a "turn-off" than a "lights-on" experience for the students. It wouldn't help your personal credibility either. What are the design goals for the experience? There are thousands of examples of kit-built technologies where following clearly written instructions will produce a functional product. Unfortunately, the experience adds little to a student's understanding of the simple- ideas that make it work. Heathkits come to mind. My good friend an mentor of over 40 years, former dean of engineering at Wichita U, assembled his first color TV from a Heathkit. Worked good, lasted a long time . . . but he had not the foggiest notion of how or why things worked the way they did. His thing was aerodynamics and mechanics. The article you cited has a clever application of some simple-ideas. The oscillators are of a configuration I've never seen before: the collector and base of the transistor are tied together via the dc resistance of the coil. Power to the oscillator comes through a 10K resistor. This means that the DC power available to the collector cannot exceed the Vbe drop of the transistor. I spider-webbed the oscillator Emacs! . . . and powered it up. Emacs! Sho'nuf. It WAS a weak oscillator given that the transistor had to run on about .6 volts. Further, I couldn't get it to oscillate at much below 15 volts. Here's the 20v trace showing about 100 mV pk-pk signal. Emacs! Here's the signal with a 30 volt supply (about 3 milliamperes through the 10K resistor). The signal is much stronger, nearly 200 mV pk-pk. I can't argue with the author's claimed success and the notion that the circuit has been duplicated thousands of times. However, before I stepped in front of a class with this project as a proposed teaching exercise, I would want to have a 99.99% SOLID circuit that had a very high probability of student success. The classroom is no place to be debugging design flaws. Your students will not be impressed. Can we talk about some other experience to introduce your kids to silicon and rosin smoke? I think the metal detector needs to be solidly vetted as at teaching tool before you drag it into the classroom. Bob . . . ________________________________ Message 3 _____________________________________ Time: 12:33:01 PM PST US Subject: AeroElectric-List: Re: AOA circuitry From: "user9253" If you have an old hard drive that you do not want, you can take it apart and remove the powerful magnets. Do not get your fingers between them! Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=332155#332155 ________________________________ Message 4 _____________________________________ Time: 01:57:42 PM PST US From: Jan de Jong Subject: Re: AeroElectric-List: PM capacitor inrush I was not too worried about the once per flight high current event, but having derived some numbers I thought I 'd share them anyway (I found the 45% overshoot from a 15 mOhm 30' wire to 15 mF interesting - glad I'm not building a 747). But thank you for your comments! Jan de Jong ________________________________ Message 5 _____________________________________ Time: 01:58:01 PM PST US Subject: Re: AeroElectric-List: Re: AOA circuitry From: Jared Yates If you want an old hard drive to take apart and don't have one, send me an email and I'll fill up a flat-rate envelope for you. On Sat, Feb 26, 2011 at 3:27 PM, user9253 wrote: > > > > If you have an old hard drive that you do not want, you can take it apart > and remove the powerful magnets. Do not get your fingers between them! > Joe > > -------- > Joe Gores > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=332155#332155 > > ________________________________ Message 6 _____________________________________ Time: 03:45:38 PM PST US From: Dan Billingsley Subject: Re: AeroElectric-List: coil tuning anyone? =0A=0AWell, I certainly appreciate and respect your opinion ( I wouldn't ha ve asked if =0AI didn't). And, you are right concerning having a solid proj ect that has been =0Aput through the paces prior to having the kids get fru sterated with it. I can =0Atell you I am a bit frusterated as a new electro nics teacher ( have been =0Ateaching Intro classes for 2 years). The curric ulum I have developed (as =0Amentioned) includes building a crystal radio a nd this has been quite successful. =0AWe then build a simple amplifier whic h uses an LM386 along with resistors and =0Acaps on a perf board. This has turned out to be a good conclusion to that class. =0AMy frusteration-come s in trying to advance a bit-into-a project that will be a =0Astep up -in-challenging skill levels and not blowing them out of the water. We =0Aare also-financially limited due to a $15 cap on what we can charge fo r a lab =0Afee, so as far as kits go...there are a bunch- out there but o ut of the dollar =0Arange. This forces me to find circuits that I can purch ase the-parts and keep =0Athings cost effective. I suppose I can keep thi ngs simple with bread boards and =0Atiming circuits, but I am open to -su ggestions for projects if you have any in =0Ayour bag of tricks. My bag is just beginning to grow along with my experience. =0AThanks for testing that circuit! Back to the-drawing board.=0ADan=0A=0A=0A>=0A>From: "Robert L. Nuckolls, III" =0A>To: aeroelectric-list@mat ronics.com=0A>Sent: Sat, February 26, 2011 10:08:08 AM=0A>Subject: Re: Aero Electric-List: coil tuning anyone?=0A>=0A>=0A>If you have any suggestions o n =0A>>what might make the following project work better, I'm all ears. =0A >>http://www.easytreasure.co.uk/bfo.htm=0A>>=0A>>Thanks a Bunch for taking a look!=0A- Hmmm . . . what's the 'lesson plan' for this endeavor?=0A- You mentioned having students lay out an ECB. Is this=0A- a paper exercis e or are you planning on fabrication=0A- as well? This is a complicated p roject (read=0A- high risk) for a class-room exercise. The device is=0A - rich in simple-ideas (physics) each of which=0A- presents an opportun ity for teaching. At the same=0A- time, it takes only one solder joint, o ne bad component,=0A- one wiring error to 'disappoint' even the most=0A - interested members of the class. Without a solid=0A- personal underst anding of that which you hope to=0A- illustrate and demonstrate, your own ability to=0A- trouble shoot and fix a defect offers risk for this=0A- being more of a "turn-off" than a "lights-on" experience=0A- for the stu dents. It wouldn't help your personal=0A- credibility either.=0A=0A- Wh at are the design goals for the experience?=0A- There are thousands of ex amples of kit-built=0A- technologies where following clearly written=0A - instructions will produce a functional product.=0A- Unfortunately, th e experience adds little to=0A- a student's understanding of the simple- =0A- ideas that make it work. Heathkits come to mind.=0A- My good frien d an mentor of over 40 years, former=0A- dean of engineering at Wichita U , assembled his=0A- first color TV from a Heathkit. Worked good, lasted =0A- a long time . . . but he had not the foggiest=0A- notion of how or why things worked the way they=0A- did. His thing was aerodynamics and m echanics.=0A=0A- The article you cited has a clever application=0A- of some simple-ideas. The oscillators are of=0A- a configuration I've never seen before: the=0A- collector and base of the transistor are tied=0A- together via the dc resistance of the coil.=0A=0A- Power to the oscillato r comes through a 10K=0A- resistor. This means that the DC power availabl e=0A- to the collector cannot exceed the Vbe drop=0A- of the transistor . I spider-webbed the oscillator=0A=0A=0A=0A--- . . . and powered it up.=0A=0A=0A=0A--- =0A--- Sho'nuf. It WAS a weak oscillator giv en that the transistor had=0A--- to run on about .6 volts. Further, I couldn't get it to oscillate=0A--- at much below 15 volts. Here's th e 20v trace showing about 100 mV=0A--- pk-pk signal.=0A=0A=0A=0A- -- Here's the signal with a 30 volt supply (about 3 milliamperes throug h=0A--- the 10K resistor). The signal is much stronger, nearly 200 mV pk-pk.=0A=0A--- I can't argue with the author's claimed success and the notion that=0A--- the circuit has been duplicated thousands of ti mes. However, before=0A--- I stepped in front of a class with this pr oject as a proposed teaching=0A--- exercise, I would want to have a 9 9.99% SOLID circuit that had a=0A--- very high probability of student success.=0A=0A--- The classroom is no place to be debugging design f laws. Your=0A--- students will not be impressed. Can we talk about so me other=0A--- experience to introduce your kids to silicon and rosin smoke?=0A--- I think the metal detector needs to be solidly vetted a s at=0A--- teaching tool before you drag it into the classroom.=0A=0A =0A=0A- Bob . . . ________________________________ Message 7 _____________________________________ Time: 06:01:04 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: PM capacitor inrush At 04:54 PM 2/26/2011, you wrote: > >I was not too worried about the once per flight high current event, >but having derived some numbers I thought I 'd share them anyway (I >found the 45% overshoot from a 15 mOhm 30' wire to 15 mF interesting >- glad I'm not building a 747). >But thank you for your comments! To be sure, the severity of the 'problem' increases with physical size of the system (long runs of wire) and complexity (lots of electrical wigglers). I think one of my Florida seminar attendees was a space shuttle techi . . . he commented that it was the electrically noisiest vehicle he'd ever worked on. But there are ways to cope. For example, the signals from GPS satellite signals are so weak at the earth's surface, they cannot be distinguished from atmospheric noise were it not for a predictable pattern in their emissions. When you know precisely what you're looking for, the extraneous stuff can be filtered/ignored as long as it's not overwhelmingly strong. Knowing what's on the power bus is the first step toward being sure that you can artfully reduce its effects to insignificance. Bob . . . >Jan de Jong > > >----- >No virus found in this message. >Checked by AVG - www.avg.com Bob . . . ________________________________ Message 8 _____________________________________ Time: 07:39:22 PM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Re: Turning simple-ideas into working hardware. At 06:35 PM 2/26/2011, you wrote: Well, I certainly appreciate and respect your opinion ( I wouldn't have asked if I didn't). And, you are right concerning having a solid project that has been put through the paces prior to having the kids get frustrated with it. I can tell you I am a bit frustrated as a new electronics teacher ( have been teaching Intro classes for 2 years). The curriculum I have developed (as mentioned) includes building a crystal radio and this has been quite successful. Great! We then build a simple amplifier which uses an LM386 along with resistors and caps on a perf board. This has turned out to be a good conclusion to that class. Another good one. My frustration comes in trying to advance a bit into a project that will be a step up in challenging skill levels and not blowing them out of the water. That is where the artful side of teaching must prevail. We are also financially limited due to a $15 cap on what we can charge for a lab fee, so as far as kits go...there are a bunch out there but out of the dollar range. This forces me to find circuits that I can purchase the parts and keep things cost effective. I suppose I can keep things simple with bread boards and timing circuits, but I am open to suggestions for projects if you have any in your bag of tricks. My bag is just beginning to grow along with my experience. Thanks for testing that circuit! Back to the drawing board. I'm pleased that you've already got a general notion for what the path to success looks like. I've had several teachers approach me who were looking to launch their first endeavor. There the challenge was greater . . . I had to teach the teacher. You've worked past those early hurdles and can focus on refinement. Some years ago I was working with a teacher who wanted to go the next step above a crystal set but with some attention to history too. How about a one-tube radio? Most folks don't know what tubes are. But they're a whole lot easier to teach than transistors! Further more, you can take one apart and hold the pieces in your hand. No such luck with a 2N2222. One of the ideas that grew out of our discussions was the development of a one-tube radio module. As with the crystal set, the major performance driver was the 'front end' work. It all happened with the tuner. Further, risks to success were based more on techniques (soldering fragile little gizmos together) and parts selection (being able to duplicate or artfully substitute a bill of materials). So how about starting with a 'stock' module that reduced the risks while evaluating performance gains demonstrated by the student work-product. I came up with this proposal: http://www.aeroelectric.com/Catalog/AEC/9050/9050-600a.pdf The idea was that these modules would belong to the school and be re-usable from one class to the next. The goal was to go through the now 'ancient' texts on DIY radios and duplicate some of the tuner designs. Then evaluate performance for selectivity and sensitivity using some calibrated test equipment (also built by the teacher or an advanced student). This reduced the class-to-class costs dramatically and reduced risks for no-learning-events driven by assembly and/or parts selection snafus. We thought that I would kit the modules and he would have some of the more advanced students build them. That teacher got laid off and I've not heard from him again. That was about 4 years ago. How would you proposed to introduce and teach ECB fabrication? There's a free ECB design package that is VERY powerful. I use it all the time for my projects. When the work product needs to be converted to useable hardware, their prices are quite reasonable and they're quick 1 day turn with two day UPS delivery of finished boards. http://expresspcb.com This same package could be used for a paper design task. Students could lay out boards, print the artwork and swap it with other teams for proofing. This is exactly the way we did boards at Electro-Mech and Beech for about 30 years. For a class, three or four teams could do layouts. Swap between teams for proofing. Then vote on the best looking layout and order that one for the class project to move forward. Alternatively, you could have a 'stock' ECB that had been previously ordered in quantity to get the cost down. I wouldn't give up on the metal detector. But I think it wise to have a working model in class on Day One. Throw a schematic up on the screen and dissect the simple-ideas. Again, packaging, coil winding, and mechanical fabrication presents some challenges that could blow a perfectly good lesson plan out of the water. Let's talk about ways to refine the metal detector (or any other circuit) into a teaching tool. How many students are in the typical class? Bob . . . ________________________________ Message 9 _____________________________________ Time: 08:09:52 PM PST US Subject: AeroElectric-List: RE:hi!5c From: leesafur@aol.com YD Dear sir/madam: ???????????????????? Please forgive us to disturb your valued time. ??????????????????????????????????????? This is a big wholesale company in china, sell electronic products to all the world,such as laptop, camera, phone and so on. We can offer the low price and high quality to you. If you have free??? ????????????????????????? time, please take a few to visit our official we bsite: www.edazzone.com ???? Then any questions, please contact us freely. ???? Email: edazzone@gmail.com??? ????????????????????? 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