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Making a Pulsing/Fading LED Circuit

Discussion in 'LEDs and Optoelectronics' started by Chris Zanowick, Mar 19, 2018.

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  1. Chris Zanowick

    Chris Zanowick

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    Mar 19, 2018
    Hello Everyone,

    I am in need of some assistance. My current project is to create a small sign with LEDs to attract attention. After reviewing all the different options, I found a method presented on YouTube which would best suit my purposes. I have gone through the video to determine the component the person used for the project.

    TITLE: How to Make a Pulsing/Fading LED Circuit
    URL: HTTP World Wide Web YouTube dot com /watch?v=qLAi7hkDuYw

    The components he descriibed in the project in the video are below.

    555 timer
    1000 microFarad capacitor
    2N222A Transistor
    150 ohm resistor
    1200 ohm resistor
    LEDs
    9v Transistor battery

    My question to your experts is this. Can you tell me what wattage are the resistors?

    Also, what is the best way to add a second LED, so they will fade/pulse in sync with each other?

    Would love to add a potentiometer to adjust the fading rate, any suggestions?

    I would love to hear from anyone who had replicated this project.

    Thanks,
    CAZanow
     
  2. hevans1944

    hevans1944 Hop - AC8NS

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    Welcome to EP, @Chris Zanowick!

    What the YouTube video shows is a "Monkey See, Monkey Do" demonstration with zero explanation of how the circuit works. Do you really expect to learn anything by replicating this project?

    If you look and listen carefully, you will notice that near the end of the video, when the 2N2222A transistor (NPN type) is being connected, that the narrative description does not agree with the actual placement of the wires. The schematic reference for part of the bread-board circuit is shown below:

    [​IMG]

    The LED in blue, its 150 Ω current-limiting resistor, and the PNP type transistor are not part of the bread-board demonstration. Also, the 20 kΩ resistor has been replaced with 1200 Ω and the 220 μF capacitor has been replaced with 1000 μF.

    In the bread-board demonstration, the collector, not the emitter, of the 2N2222A NPN transistor is connected to the positive 9 V supply rail. The 150 Ω resistor is connected to the emitter of the transistor, not the collector. This agrees with the schematic posted above and also available through this link.

    The video is poorly made (it is difficult to see where some of the wires connect to the positive and negative power rails; the base, emitter and collector terminals of the transistor are hidden; the polarity of the LED is impossible to determine by inspection) and the video is incorrectly narrated. The worst parts are the comments that follow below the video. These are composed by the blind leading the blind. Some of the "advice" is just plain wrong, like connecting multiple LEDs in parallel. For example, this comment:

    is not only WRONG, but it is never challenged in later comments. YouTube, in general, is an awful place to learn anything about electronics. You have come to the right place in joining us here at Electronics Point.

    To answer some of your questions... the resistors can be 1/4-watt or even 1/8-watt (if you can find them). To add a second LED just wire it in series with the first LED. Point both in the same direction. To vary the fading rate you would wire a potentiometer, connected as a variable-resistor (rheostat), in series with the 1200 Ω timing resistor. I would recommend you start with a 50 kΩ potentiometer, which will allow you to vary the overall timing resistance from 1200 Ω to 51,200 Ω.
     
    Last edited: Mar 19, 2018
  3. Chris Zanowick

    Chris Zanowick

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    Mar 19, 2018
    Hi Hevans1944,

    Thanks for your reply. I know you can't believe everything see on the Internet. Was only using it as a reference, and yes that was a horrible video. Like the one below. Would like to know how he did video graphics and such.

    Dual Flashing LED Circuit using 555 timer on breadboard - Basic electronics Projects
    URL: HTTP World Wide Web YouTube dot com /watch?v=y2UYPpNQRJg

    I have a background in sciences, engineering, telecom and Information Technology which helps with a number of my electronic projects from small to commercial high voltage. But, there is always something to learn. Used to have fun with the old Radio Shack 101 electronics experimentation kit back in the early 70s for the small electronic gadgets.

    I had a good feeling the wattage was 1/4 or possibly less. Thanks for the confirmation. Have to go to bed, early start for work tomorrow. Will have to take more time tomorrow evening to go through the details of your comments. I am sure that I'll have some follow-up questions on the things you pointed out.

    Thanks,
    CAZanow
     
  4. Chris Zanowick

    Chris Zanowick

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    Mar 19, 2018
    Hevans1944,

    Oops, I gave a link to a wrong video. It was supposed to be another fading/pulsing circuit build.

    You don't think that I would use YouTube as an official way to learn a science, do you? I would hope you would have thought better of me. That video is the reason I came to the forum. His wiring looked questionable, very dodgy.

    This guy's diagram appears to be an alternate version of fade/pulsing function. It looks to be a dual LED alternating fading/pulsing function.
     
    Last edited: Mar 20, 2018
  5. hevans1944

    hevans1944 Hop - AC8NS

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    I don't know anything about you, and therefore have no thoughts, better or worse, of you... yet.

    There are hundreds, if not thousands, of visitors to Electronics Point who believe they are informed by the likes of YouTube videos and Instructables articles. They are all "monkey see, monkey do" experimenters, not scientists by any stretch of the imagination, interested only in copying what they believe will be a successful outcome for their current project. Many are "drive by posters" who join EP just to ask a question and then are never seen or heard from again. Often that single question will elicit a thread of a dozen or more responses before everyone realizes the original poster (OP) is not participating in the "discussion" and may not ever "visit" EP again. That's a waste of our free time.

    I have some problem with that attitude because, IMO, it is inappropriate for this particular online forum. There are other forums that do cater to "monkey see, monkey do" projects, some with better advice than others. You will have to discover and visit them and then decide for yourself whether such is worth your investment in time. Here we cater to those hobbyists who help themselves, meaning a certain level of knowledge of physics, electricity, and electronics is required to fully participate. So far, you have not demonstrated any such knowledge.
     
  6. Chris Zanowick

    Chris Zanowick

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    Mar 19, 2018
    Did I accidentally join a forum that was more for electronic engineers? If I did, I am sorry. I get the impression that maybe the type of project on which I started this thread is inappropriate.
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    1/4 watt will be fine. Larger is ok too.

    Another LED in series with the existing one may work (it may also change the behaviour somewhat). Another alternative is another 150Ω resistor and LED placed in parallel with the existing one. This may also change the timing slightly.

    Replace the 20k resistor with a 1k resistor in series with a 50k pot.

    If you need more specific instructions about how the additional LEDs should be connected, go to the resource section and read the LED resource.
     
    hevans1944 likes this.
  8. davenn

    davenn Moderator

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    no not at all, as I said in the PM to you :)
    please don't take offence to what Hop said.
    He was more pointing out the nuisance people that populate the net and forums ( a generalised comment)
    what @hevans1944 is probably trying to tell you in a not so clear way ( unusual for him) is that there is a lot of garbage out there
    I also commented on that in the PM to you :)

    if you see something you would like to have a go at building.
    A good way to find out if it is any good and reliable is to post a link and ask the Q ... "Is this project OK, or is it garbage"
    then sit back and wait for the comments

    Dave
     
    darren adcock and hevans1944 like this.
  9. Chris Zanowick

    Chris Zanowick

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    Mar 19, 2018
    Hi Steve,

    Thanks so much for your input. I thought that I would do a few breadboard simulations on TinkerCAD with various designs. Setup three and there are many out there. Some work better than others, assuming the simulation accurately represents the behavior of the design. Many of the circuit designs are not verified to be operational as claimed.

    It has been many years, since I did some fairly in depth electronics work, thought 1/4 watt was right. Many of the designs don't mention all the specifications of the components. Guessing a bit on what some of these guys stating.

    One of my designs in the simulator has a 100k pot, forgot the other resistor. But, It still works in the simulation. How much of a change in behavior do you think I would see by adding the fixed resistor into series with it?

    I did set the LEDs up in series with only one resistor. Simulation seems to be okay with that. I haven't been able to determine whether it being in series or parallel will generate more synchronization of LEDs. I only need to use two for the project.

    I would like to try one or more other designs, before I settle on the best of the three I have right now. Unless, there is a better one out there.

    Looking at the designs, none of the ones I have been evaluating have a power switch in them. Generally where is the best place to put that switch. Right now I have one setup near the battery. I set it up quickly and threw it on the positive side for the time being, until I can go back through and clean up the layout.

    I'll upload an image of it when I get it cleaned up a bit for the benefit of all to see.

    Do you know if there is an easy way to convert the BRD file to a diagram? Have been poking around the Internet for an answer on that, nothing definitive on it, yet.

    Thanks.
     
  10. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    That is generally the appropriate place.

    Sure. Let me tell you that I'm certain the behaviour will differ depending on whether you have two LEDs in series with one resistor, or two strings (of 1 LED and 1 resistor) placed in parallel.

    Feel free to experiment and see if one suits you better than the other.
     
    hevans1944 likes this.
  11. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Not that I'm aware of.
     
  12. hevans1944

    hevans1944 Hop - AC8NS

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    Okaaay... not a "drive by" poster, and you still seem to be interested in learning at your "advanced" age. Geez... electronics lab experiments from the 1970s...

    I purchased one of these a couple Christmases ago for one of my grandchildren, who has been diagnosed as having a form of autism. He really enjoys "taking things apart" to "see how they work" and even sometimes manages to put stuff back together again. So I bought one of the last remaining kits sold locally by Radio Shack and gifted him with it for Christmas that year.

    He lives with his mom in Virginia Beach, Virginia, and I lived in Dayton, Ohio, at the time. So, after returning to Dayton, I visited one of the few remaining Radio Shack brick-and-mortar stores and purchased another learning kit for me, thinking I would do the "experiments" along side my grandson, communicating via cellphone. Alas, he never showed any interest and Radio Shack is no more! But you can still find the kits sold on-line at sometimes bargain and sometimes truly exorbitant prices. Caveat emptor! The original kit included two manuals, one for analog circuits, one for digital circuits, written by Forrest Mims. The manuals consist of classic "monkey see, monkey do" circuits, with just enough "theory" thrown in to keep a youngster's attention and perhaps encourage them to want to learn more.

    I have noticed what to me is a disturbing trend lately: Newly hatched "electronics enthusiasts" are satisfied with simulating circuits on a personal computer rather than actually building, testing, and experimenting with real circuits using real parts. Perhaps this has something to do with the cost of obtaining parts, but IMO it is a dangerous path to follow if you really want to learn electronics. There is an old saying: The map is not the territory. Computer simulation is the map; the territory is the real world of electronics.

    A simulation is only as good as the model from which it is constructed. Without actual construction, using real parts, there is no way to validate whether the model is accurate or not. Does this mean simulation is useless? Of course not, but one needs to be aware of one's limitations, as Dirty Harry (portrayed by Clint Eastwood) would say. Any simulation needs at least one "reality check" against real parts in a real world. But of course you are aware of this fact from your statement:

    If you are serious about learning electronics, dig out that old 101 Experiments kit (or buy a replacement) and begin bread-boarding real circuits again using real components. Purchase an inexpensive digital multimeter at a "big box" home improvement store. Verify the validity of Ohm's law calculations by measuring voltages and currents in actual low-voltage (battery operated) circuits. Yada, yada, yada. This will take some time, but if you lay the groundwork for DC analog circuit analysis (Ohm's Law, Kirchoff's Laws) you will have a solid foundation from which to proceed.

    Simulations (SPICE) were originally created to assist in integrated circuit design around the middle of the 20th Century. Understandable, given the cost of actually "taping out" and manufacturing a new integrated circuit. With the advent of inexpensive personal computers, simulations have spread like wildfire into every aspect of design... not just electronics but anything you can think of can now be inexpensively modeled and simulated.

    That includes weather and climate models, but we all know (or should know) how accurate or inaccurate those simulations can be. Last year I watched with some amusement how "forecasts" of the track and intensity of Hurricane Irma evolved. None were very accurate, but a lot of people here in southern Florida decided "to get the hell out of Dodge" rather than suffer the possibility of a "direct hit" by Irma. The resulting traffic on I-75 turned it into a virtual parking lot for several weeks.

    Go ahead and tinker with Tinker Cad and its constant "improvements," but I doubt you will learn much electronics compared with the "old fashioned way" of just building something from real parts. "Letting the magic smoke out" of components is a time-honored experimenter's tradition. So purchase plenty of spare parts. Most of all: have FUN.

    The purpose of the fixed resistor is to limit the minimum value of resistance you can insert. Some circuits behave poorly (or not at all) if the potentiometer (wired as a rheostat or variable resistor) is set to "zero" value. Since this is a simulation, go ahead and add the fixed resistor in series with the potentiometer. Then you decide how much change in behavior occurs.

    No, Electronics Point welcomes everyone interested in learning and practicing the art of electronics. Most of us do expect you to learn... at your own pace and to the level of your own ability. But if your only interest is copying the work of others, that's okay too. If you want to really get embarrassed and feel like you have stepped off into the deep end of the "electronic engineers only" pool, try posting questions at Electronics Stack Exchange.

    As far as types of projects you can post, the most inappropriate are subjects that violate established "laws" of physics... perpetual motion machines of any kind, zero-point energy sources, whether based on sucking energy from "the vacuum" or from permanent magnets, will get your post either deleted by a moderator or moved to the woo-woo section and promptly closed for further discussion. Full terms, rules and guidelines, subject to change and interpretation by the moderators at any time and for any reason, can be found here.

    We get MANY "how do I do this with my LEDs" type of questions. There is now a thread in the resource section on EP devoted just to the topic of how to "light up" one or more LEDs. The blinking, dimming or fading, or sequencing of multiple LEDs is a separate issue worthy of its own thread discussing specific implementations. The "fading and blinking" circuits you have cited use the linear properties, as opposed to the switching properties, of a transistor to control the brightness of an LED. Although this works, it is not very efficient. A "better" alternative is to control LED brightness by varying the average current through the LEDs using pulse-width modulation, driving the transistor as an on/off switch instead of operating it in it's linear region.
     
  13. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    In a real circuit, if this resistance falls to zero (or too close to zero) the 555 will be destroyed.
     
  14. Chris Zanowick

    Chris Zanowick

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    I know we are a bit off topic here, but what the heck. We'll get back to it, though.

    Holy smokes Hevans1944! I thought I typed a lot. Did you learn typing the old fashioned way on manual typewriter like I did? Sure seems like it.

    Would you happen to know, I live in southern Dayton, Ohio. Miamisburg to be exact and work out at WPAFB. What a small world. It seems many Daytonians end up in Florida at some time or another.

    Looking back now, I really wish I wouldn't have gave up that Radio Shack 101 electronics experimentation kit. I believe my Mom donated it. Hope it inspired someone else to learn electronics and sciences. I also had the chemistry kit. Helped me with my model rocketry and pyrotechnics activities.

    I haven't dug that far into electronics as I had more of a fondness with model rockets and desire to learn aero-astro engineering. The aero-astro industry wasn't doing so well when I was in college. Had to abandon the rocket scientist career. Ended up in computers, doing everything from one end to the other. The fundamental knowledge in electronics help pave the way for many other things. Electronics knowledge was so helpful that I used it quite a bit in fireworks displays doing electronic firing systems and setup. They are now very advanced and control by computers. The hubs which electrify the individual igniters for the fireworks still use fairly basic electronics. If you are a Do-It-Yourselfer person, electronics is unavoidable. Need to learn it, period.

    I heard the computers and the modeling software for weather forecasting are out of date here in the USA. Europe uses more up to date hardware and forecasting models. Explains why you'll see various hurricane track forecast cones for one storm.

    Have a nice Radio Shack multi-meter bought 25 or more years ago that looks like a Fluke. Always pulling that thing out and using it. Have an amp reading accessory that goes with it for commercial work. Don't think this multi-meter has a capacitance reading capability, though. Really needed that to check my capacitor that I believe went out on my washer machine. Fairly sure it cooked the windings on the motor, could smell it. Could really use an oscilloscope, too.

    Hevans1944 and Steve,

    After asking about the fix resistor in line with the potentiometer, was a bit a stupid question on my part. Believe I already knew the answer before asking it, or at least after clicking the "Post Reply" button on the page. Logic would dictate the potentiometer most likely adjusts to zero and the fix one is necessary to have some sort of resistance on that leg of the circuit with the 0 ohm setting of the pot. But, thanks for the warning that it could damage the 555 timer. Very good to know for everyone.

    Is there any particular power and voltage ratings I need to pay special attention to for potentiometers for these types of projects? Don't see any of those specifications mentioned for the ones used on breadboards.

    From what I have been researching, the design I am primarily working with seems to generate the best sloped wave for the fading. Oscilloscope would really help confirm that.

    I am loading up a couple of online shopping carts with all the electronic components for the real hands-on work.

    Really wish I found this forum many years ago. I see there are even a few topics posted on lasers. How very cool!

    Thanks.
     
  15. hevans1944

    hevans1944 Hop - AC8NS

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    Yep. Dad went to a G.E.M (Government Employees Mart) department store in Houston, TX when I was about seven or eight years old, living in Lake Charles, LA where Dad was a bombardier/navigator on B-47 bombers. He bought a Royal Portable Typewriter with an integrated case. There were four levers in the bottom of the case that secured the typewriter while also allowing the typewriter to also be removed and placed on a desk. I was very happy when he gifted me with that typewriter, but not so happy when he covered all the keys with red plastic peel-off stickers so I couldn't see the characters embossed into each key. He then told me I had to learn something called "touch typing," and I was not allowed to remove the key stickers until I did.

    So I spent the next few months (and years... my short stubby fingers had trouble reaching the number keys from the "home" row) learning how to touch type in lieu of two-finger hunt-and-peck. Good thing I did too: one high school I attended years later in Smyrna, TN in the eleventh grade offered a typing elective. So I signed up and was the only guy in a class full of girls :D. Since I already knew how to touch type, I aced the course.

    I eventually joined the Air Force and purchased a used electric typewriter at my first (and only) duty assignment at Kincheloe AFB, MI. That served me for many years after my AF hitch was up, until personal computers came along. I gave up using the electric typewriter and began using PCs with word-processing software instead. Not quite so good for printed copy using affordable printers, but I did purchase a 24-pin Epson dot-matrix ribbon printer that did a "pretty good" job with Word Perfect fonts. Later I upgraded to a monochrome HP Laserjet printer and wore out two of those before finally settling down with HP ink-jet color printers. IIRC, I am now on my third (or maybe fourth) HP ink-jet. If I need high-quality color prints, I take a thumb drive to Staples and let them print. I use Microsoft Office software exclusively now, instead of leaving the Windoze environment for a flavor of Linix and open-source software. Just lazy, I guess, but Word 2010 does everything I need to do. And WIndows 10 seems adequate as far as multi-tasking, non-premptive operating systems go.

    I spent most of my career working for contractors who worked for various labs at WPAFB, Area B. Fresh out of the service in 1967, I talked my way into a technician job at the UDRI and stayed there for twelve years while I pursued (part time) a BEE degree on their dime. All I had to pay for was my books, and most of the labs were waived because of my technician job. My first task at UDRI sent me to Area B to resurrect a dynamic fatigue testing machine, whose California builder went bankrupt trying to get it to work. We got it running to original spec about a year later. From there on it just kept getting more and more interesting until I graduated.

    By the time I graduated with a BEE degree in 1978 I thought I had seen everything, So I left UDRI a year after graduation and took a job as a principal engineer with Mead Technology Laboratories in Beavercreek, replacing an engineer there who was forced to leave because of a perceived "conflict of interest" in his owning a small company that "competed" with the giant Mead Corporation for government contracts. Yeah, right. They did give him a choice: give up his shares in the "competing" company or give up his job. That was a no-brainer for him and an opportunity for me. A couple weeks after I accepted their offer I got a call from Hughes Aircraft in Phoenix, AZ, where I had earlier interviewed to do engineering work on Maverick TV-guided air-launched missiles. I wasn't too eager to work for them after I found out their entire technician labor force would walk out if I so much as picked up a soldering iron. I am a hands-on engineer because of my previous technician training and experience. So I stayed at MTL another twelve years, until January 1991 when they laid me and a woman chemical engineer off.

    Much later after I was hired I found out that almost all the work MTL did was either for Foreign Technology Division, now The National Air and Space Intelligence Center (NASIC) at WPAFB, or for the CIA, and required clearances above Top Secret. I got the TS clearance right away, but the extra "tickets" took considerably longer.

    My last major project at MTL was around 1990 to re-design the control electronics for a huge indoor roll-pitch-and yaw (RPY) environmental test chamber at the Sensors Branch in Area B. This rig had been built in the 1950s when all the highly classified overhead imaging systems were based on photographic film. I got to see some of these (now obsolete) camera systems which were marvels of engineering ingenuity. The branch supervisor wanted his test rig updated (his swan song prior to retirement) to support more modern collection systems. Faster, smoother motion, better accuracy, more reliability. I think we were successful in meeting their goals, although just exactly how successful is based on a "need to know" and all my team "needed to know" was we did a good job and deserved an "atta boy."

    This test chamber used hydraulic actuators to lift up and toss around overhead image collection systems while simulating the outside pressure, temperature, and radiation environment, as well as targets on the ground. The government customer wanted to replace the original analog model-controlled system with digital servo valves and an IBM PC-AT clone running an Intel 80386 with 80387 floating-point math co-processor. He also wanted to run the current version of Microsoft Windows, which would not do at all because of its lack of pre-emptive multi-tasking and lots of "bugs" at the time. So, we opted for a real-time Linux OS kernel and X-Windows for the HMI and didn't bother to tell him it wasn't going to be Microsoft Windows until we had something to show him. IIRC, this then state-of-the-art PC was clocked at a whopping 12 MHz.

    We kept the analog model, which was located in the control room above the test floor, but didn't use it for control. Instead it displayed (in miniature) the motions of the real-deal out on the test floor. I managed to get the services of a whiz-bang, recent graduate, new hire, genius software weenie/physicist/engineer to roll the code that made it all work. I, with the help of a senior electronics technician, performed the grunt work of replacing control and signal wiring and designing the control algorithms that were implemented in software.

    This was the software guy's first experience with an embedded computer running real-time programs that tossed around tons of expensive hardware. He did a superb job. He eventually left MTL (which eventually went out of business when they failed to make the transition from film to digital overhead collection systems) and he now has a cushy supervisor job in one the the labs at WPAFB Area B.

    Several years after all that, I landed a job in 1996 operating and maintaining a small 1.7 MV tandem particle accelerator for UES, Inc. As word got around that I was a "hands on" engineer, I got to design laboratory experiments and teach others how to service and maintain vacuum deposition systems. I finally was forced to retire in December 2014 because I couldn't find any customers for our accelerator heavy-ion, high-energy, implant services. We could only implant 4-inch diameter wafers, and the semiconductor industry had moved on to much larger wafers by then. THAT'S WHEN my wife decided we were gonna retire to someplace warm, like Venice, Florida. So in October 2016 we bought a house here, and in December 2016 we rented a Penske truck and moved ourselves here. Best move I ever made, and as a former Air Force Brat, I've made a lot of moves.

    I watched both the European and American track predictions for Irma last year. Neither one appeared to be particularly accurate IMHO, but I don't yet have an historical record to compare them with. We'll see what happens in the upcoming hurricane season. No matter what the track or its predictions, we plan to ride them out.

    @(*steve*) gifted me with a digital inductance/capacitance meter a few years ago after I escorted him to various sights in the Dayton area. I think he especially enjoyed the visit to Mendelsons. I have wanted one of those LC meters for years, but hadn't realized how affordable they are. I later looked it up online and discovered there is a lot of inexpensive test equipment now available via mail-order from Asia and Pacific Rim countries. A decent dual-channel, 200 MHz, digital storage oscilloscope only costs about 300 bux and they are available in the USA from an American retailer with free shipping.

    Always use potentiometers to attenuate or select low voltage, low power signals. Avoid wiring potentiometers as variable resistors (rheostats), but if you need to do that, always include a series resistor to limit the minimum value of resistance you can "dial in."

    You can purchase pots with power rating from a few hundred milliwatts to several watts, but for most hobby uses you will be working with less than a half watt of power dissipation and voltages of around twenty-four volts or less. Always calculate the maximum power a potentiometer will have to dissipate. If the calculations yield power levels that exceed the rated power dissipation of the potentiometer, either replace the potentiometer with a higher rated power, or change your circuit to decrease the amount of power dissipated.

    Remember to have fun and "let the smoke out" less frequently as you progress in experience and knowledge.

    73 de AC8NS
    Hop
     
  16. Chris Zanowick

    Chris Zanowick

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    Mar 19, 2018
    Now that I thought about it a bit, remember my Brother dropping a metal screwdriver onto the Radio Shack 101 Electronic Kit while some circuits had power, destroying a number of components. Distinctly remember seeing some sparks flying. He was a bit younger and more of a mechanical engineer. It was one of my older Brothers who became the EE.

    Wow, Hop. That is quite an impressive career and thank you for your service. Being that I work out at the base, some of your work sounds familiar. I hope you are enjoying your retirement.

    I had a funny feeling about your typing. I, too, like the fact that my typing class had mostly girls in it. But, had a gut feeling I needed to learn touch typing well to benefit me in the future. One of the best decisions/predictions I ever made. That was before Windows emerged, in the DOS days. I managed to acquire my Father's old typewriter much like the one you described. It is an antique. Have a photograph of him typing on it while wearing sunglasses. Thought he was being cool back in the early 1950s. Where I really became more fluent was when I was working with another IT engineer to transcribe a huge deployment into a huge technical document (over 300 pages) for Standard Register. Years later heard from a New Horizons instructor that was well done document and easy for the techs to follow. It was good to hear that when I struggled a bit with writing essays/papers in school. Think going to a college prep high school and learning some Latin made a difference in the end.

    Area B is where I work now. I hear about all the old stories and times passed. It has been nearly a century since the Orville Wright was a part of the ground breaking in April 13 1926 for buildings 11 and 16 at Wright Field. A lot of things have changed and are still changing there in Area B. You might have known my friend Harvey Bennett who worked on a number of things including the radio systems around the time you were there. He was a hands-on electronics engineer/technician guy. He also served in the USAF. But, there are thousands of people out there. I meet new people there every day, despite having been there for years.

    Was talking to a guy who is repairing an old Garrett Master Hunter metal detector I received from my Brother. He told me that they didn't introduce the capacitance feature on those nice older Radio Shack multi-meters until a number of years later. That sucks.

    Are we going to get into trouble with the moderator for getting of topic here? lol

    Thanks for the additional info on the potentiometer. Have a bit of a break on that project, while I try to get converted over to a civilian position. Anyway, still need to wait for all my components to get shipped to me.
     
  17. hevans1944

    hevans1944 Hop - AC8NS

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    2,046
    Jun 21, 2012
    Depends on how far "off topic" the thread wanders. Sometimes the original poster (OP) leaves (or never participates) in the discussion that follows their initial query. Then you can see a back and forth exchange of posts as we try to figure out what the original question was about. It soon becomes obvious to most of the moderators when this occurs, especially when the conversation is leading nowhere. So, yeah, if we continue sprinkling in personal comments, instead of addressing your original question, the thread could get closed by a moderator. No harm, no foul, for that. We can always start another thread or even begin a "private" conversation.

    I don't do many private conversations because, by definition, whatever is discussed is not made general knowledge on the forums. That seems, to me, to be counterproductive to what EP is all about. I do have a private conversation that goes back quite some time with one member, but we also share common interests in woodworking and live near each other in Florida. And we exchange e-mails from time to time.

    So, getting back on-topic, if I were to summarize LED pulsing and fading using a 555 timer IC, there are two methods that I have seen used, one more robust than the other. The first method, using the circuit you posted, takes advantage of the 555 ability to both source and sink current from its output, pin 3. The circuit charges and discharges a capacitor through a fixed resistor connected to pin 3. This causes a "curvy" sawtooth shaped voltage waveform to occur across the capacitor, and this voltage in turn causes the conduction of a transistor to alternately increase and decrease. One or two LEDs can be wired in series with a fixed current-limiting resistor from "ground" to:the emitter of the transistor, the collector being connected to the positive supply. This part of the circuit constitutes an emitter follower: the voltage on the emitter (with respect to ground) "follows" the voltage on the base, minus the voltage drop across the emitter-base junction. Thus the emitter reproduces the "curvy" sawtooth voltage appearing across the capacitor. There are many variations possible on this theme, but the important thing to remember is the current through the LED is made proportional to the conductance of the transistor, which is operating as a linear device instead of as an on/off switch.

    The other way to control pulsing and fading is to modulate the duty cycle of a pulse-width modulated PWM signal. WIth PWM, the voltage sent to the LED (or two or more series-connected LEDs) is constant in peak amplitude but goes to zero voltage periodically. The current-limiting resistor can be lower in value than would be necessary if voltage were applied continuously, because the average current passed to the LED string is just the maximum current multiplied by the duty cycle: the ratio of the time the pulse is on to the time it is off.

    Pulses are typically generated at a high frequency, a few hundred to a few thousand hertz, to avoid the perception of flicker. Fading is controlled by varying the duty cycle over a longer period of time, typically a few seconds to few minutes depending on the desired fading effect. The advantage of PWM is the current supplied to the LED (or LEDs) is switched through a transistor that is either on or off. An ideal transistor dissipates very little power when fully on and no power at all when fully off. The only time power is dissipated in the transistor is when it is making the transition between the on and off states. A good design will guarantee a very fast transition to minimize power losses.

    Some microprocessors, including the Arduino, implement PWM on one or more output pins by means of internal hardware configuration registers, A software program (a sketch in Arduino-speak) loads the registers and thus determines the PWM duty cycle. All you need to do is connect the PWM output pin to an appropriate transistor driver circuit. This is a good Arduino programming exercise after you get past programming the blinking of the built-in LED on the Arduino board.
     
  18. Chris Zanowick

    Chris Zanowick

    12
    0
    Mar 19, 2018
    Hopefully, the moderator(s) will been a bit lenient in this case.

    We have some common interests with the woodworking, as well.

    Thanks That is a great answer to the question I was going to ask. What circuit would produce the best fading pattern? The answer is in your explanation. The circuit which appears to have the best fade appearance, and I believe has the curved saw-tooth wave of which you mention, is the best one out of the three I have setup. But, that is just the simulation. Won't know for sure, until I build it in the real world. I still need to upload the diagram of that circuit. Wish there was an easy way to convert the TinkerCAD breadboard simulation to a diagram.

    I was thinking my next project would be an Arduino board setup. I do programming in many languages in my regular job. That should be helpful with Arduino projects.
     
    Last edited: Mar 28, 2018
  19. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,299
    2,737
    Jan 21, 2010
    As long as the thread is:
    1. Still discussing the original problem effectively
    2. Remains friendly
    3. Doesn't evolve into Woo-woo
    I have no problem with parts (even large parts) of individual posts following interesting sidetracks.

    At the point where either of the above cease to be the case then I would step in.

    Other moderators may have different thresholds, but I'm pretty confident we all apply a similar kind of test.
     
  20. Chris Zanowick

    Chris Zanowick

    12
    0
    Mar 19, 2018
    Thank you, Sir.
     
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