hybridfree/eevblog-posts huggingface dataset:
Learning how to identify boards  - Page 1
Forum section: electronics / beginners

author: Seaofdep
author_rank: Regular Contributor
timestamp: October 17, 2017, 06:09:08 am
content: How do y'all identify what purpose different circuit boards were for? Usually researching does the job but for example picture I added I can't find anything , looked up website labeled and found nothing, any help?ThanksSent from my iPhone using Tapatalk

author: Nusa
author_rank: Super Contributor
timestamp: October 17, 2017, 06:26:09 am
content: Context is important when trying to determine what a board does.In this case it's easy because I'm familiar with boards very similar to that one. What you have there is a BMS (battery management system) board for a lithium-ion pack. For up to 10 cells in series, based on the number of contacts.

author: Boschi
author_rank: Regular Contributor
timestamp: October 17, 2017, 06:27:43 am
content: Im pretty sure is a bms, but i cant say much more :/Inviato dal mio A0001 utilizzando Tapatalk

author: Seaofdep
author_rank: Regular Contributor
timestamp: October 17, 2017, 06:34:25 am
content: That's what I thought at first mainly because most I have seen has the battery pads labeled B1-2-3 etc but second guessed myself. Hmm this might be useful being that I have a dual cell charger ATM which can be a bit aggravating when needing to charge several cells..... thank you for the help !!Sent from my iPhone using Tapatalk

author: Seaofdep
author_rank: Regular Contributor
timestamp: October 17, 2017, 06:40:38 am
content: Any chance where I can find a wire diagram for something similar ?Sent from my iPhone using Tapatalk

author: Seaofdep
author_rank: Regular Contributor
timestamp: October 17, 2017, 06:56:41 am
content: Quote from: blueskull on October 17, 2017, 06:44:27 amAlthough I was pretty sure it was a bms Being a beginner and knowing said subject isn't to be taken lightly , it's good that I second guessed myself and went with asking for help. I'm not sure what or if it can be anything else and that's why asking was the way to go . Thank you , your comment led me to researching and learning some new things Sent from my iPhone using Tapatalk
Learning how to use a 555 timer - oscilloscope - troubleshooting - Page 1
Forum section: electronics / beginners

author: de_light
author_rank: Regular Contributor
timestamp: October 05, 2020, 10:44:35 am
content: Just messing around with a simple 555 astable circuit and having a probe around with my new Rigol 1054Z oscilloscope. Just learning.I built a circuit and clearly did something wrong. My LED switched on and off at the (slow) rate I set, but initially, the LED was very dim for about a second. I put the probe on the LED and got quite an interesting waveform. It showed lots of high-frequency noise at 11KHz at 5.1V which corresponded to the dim section, before settling down to 3.5V when the waveform was stable. I've attached a picture of the same pattern but AC-coupled.I then rebuilt the circuit from scratch and problems were solved - nice square waveform pattern.What went wrong in my circuit the first time to give me all that high-frequency AC signal which made the LED dim?!

author: Doctorandus_P
author_rank: Super Contributor
timestamp: October 05, 2020, 12:16:08 pm
content: I'm guessing this capacitor is supposed to be connected to something, possibly pin 5? (I have not looked at a 555 for some time).
Learning how to use an Hp8903a - Page 1
Forum section: electronics / beginners

author: reddish75
author_rank: Regular Contributor
timestamp: March 28, 2017, 03:05:10 pm
content: Hi, looking on how to use a HP8903a properly for testing amplifiers etc,With the pic in the link below I'm measuring the output of my Leader Lag-120b its set at 20khz as you can see but with the distortion is it measuring at 0.0261? Am I reading that correctly?Thankshttps://1drv.ms/i/s!AhyV-hIo37nZp1toa_ezUTaw0ykp

author: barry14
author_rank: Regular Contributor
timestamp: March 28, 2017, 11:20:27 pm
content: The % annunciator is lit so the reading is 0.0261% which is a reasonable value for distortion of an audio generator.

author: metrologist
author_rank: Super Contributor
timestamp: March 28, 2017, 11:22:24 pm
content: That's cool, I have an 8902 I'd like to learn how to use...

author: reddish75
author_rank: Regular Contributor
timestamp: March 29, 2017, 02:25:04 pm
content: Thanks for that, so to test the specs (shown in pic in link below) what would I set it to?https://1drv.ms/i/s!AhyV-hIo37nZp1zH-iwmeTakJGeg

author: Tony_G
author_rank: Super Contributor
timestamp: March 30, 2017, 01:00:19 am
content: The manual for this is here:http://exodus.poly.edu/~kurt/manuals/manuals/HP%20Agilent/HP%208903A%20Operation.pdfEnd of section 1 has some basic measurements explained and 3-38 onwards details each of the options.TonyG

author: Tony_G
author_rank: Super Contributor
timestamp: March 30, 2017, 01:03:27 am
content: Quote from: metrologist on March 28, 2017, 11:22:24 pmThis guide will take you and a signal generator through the key functions of an 8902A.http://www.keysight.com/upload/cmc_upload/All/EPSG085831.pdfTonyG

author: metrologist
author_rank: Super Contributor
timestamp: March 30, 2017, 02:59:54 am
content: Thanks Tony!

author: Tony_G
author_rank: Super Contributor
timestamp: March 30, 2017, 03:21:32 am
content: NP, it's a fantastic guide in my opinion to show the basics of the 8902A. The only downside is that it assumes you know why you'd want to measure what you're measuring.The 8902A is a great piece of kit. I went out and bought the microwave down converter (11793A) for mine. Been very happy with it.If you don't have the 11722A Sensor that goes with it then you can build your own. I did a video on it here:https://youtu.be/39UZNyCStoUTonyG

author: macboy
author_rank: Super Contributor
timestamp: March 30, 2017, 02:49:41 pm
content: Quote from: Tony_G on March 30, 2017, 03:21:32 am8902A != 8903A

author: Tony_G
author_rank: Super Contributor
timestamp: March 30, 2017, 03:56:17 pm
content: Correct but Metrologist asked about an 8902.
learning how to use my Rigol DS1104Z's features, need help - Page 1
Forum section: electronics / beginners

author: jpyeron
author_rank: Regular Contributor
timestamp: November 24, 2019, 04:06:05 am
content: I am trying to reverse engineer a communications protocol between two black boxes.The reader has an inductive coil and the sensor has a mating coil. I have put a man in the middle coil circuit, and the reader communicates with the sensor successfully.It appears as a 7kHz 34V peak to peak sine wave, sampled as show here:. The communications start after pressing the trigger and last less than 5 seconds (having trouble getting an exact timing).I tried the record feature, but captures way too little (2 frames), so I know I am doing something wrong.

author: jpyeron
author_rank: Regular Contributor
timestamp: November 24, 2019, 05:12:04 am
content: I am assuming that I will see something like:.I am looking to trigger continuous recording, until memory is exhausted and after the first trigger event.The whole signal is about a second long.100us per divhttps://youtu.be/at8rgkf5-hs?t=420us per divhttps://youtu.be/at8rgkf5-hs?t=17

author: jpyeron
author_rank: Regular Contributor
timestamp: November 24, 2019, 05:56:44 pm
content: Solved it - Roll mode - page 63 of the manual
Learning Inductor Behavior by Simulating in LTSpice - Page 1
Forum section: electronics / beginners

author: fatalelieberi
author_rank: Contributor
timestamp: August 23, 2017, 04:41:04 am
content: As the title suggest, I'm trying to learn how inductor behaves. I read from my book that it follows this equation V=L*(di/dt). So, to confirm it, I'm setting up a circuit in LTSpice which can be seen below. Basically, I'm giving a time-varying linear current to the inductor from 0A to 1A for 5ms. Then, the current rate changes to 0A from 1A in 2ms. If my calculation is correct, at the rising current, the inductor will have 0.2mV across it until 5ms then it will have 0.5mV at the falling current (5ms to 7ms). However, the simulation graph shows different result. So, basically I want to ask is this, how does this happen? Did I make a mistake?

author: Ian.M
author_rank: Super Contributor
timestamp: August 23, 2017, 05:21:45 am
content: From the LTspice help file:QuoteTo get a 'pure' theoretical inductor without fiddling in the control panel you *MUST* set Rser to 0 and Rpar to effective infinity (I used 100 TeraOhms).Also using a behavioural current source for linear ramping is extremely clumsy and in larger sims will increase simulation time. I strongly recommend an ordinary current source configured with a PWL waveform.e.g.Code:PWL(0 0 +1m 0 +5m 1 +2m 0)waits 1ms (as starting immediately at time=0 can result in large transients in some circuits) then over the next 5ms ramps up to 1A,then over the next 2ms ramps back down to 0.LTspice sim attached that matches your theoretical figures.

author: fatalelieberi
author_rank: Contributor
timestamp: August 23, 2017, 06:37:24 am
content: Wow, that explains a lot! Thanks for your help, it's now behaving like the theory says.Quote from: Ian.M on August 23, 2017, 05:21:45 amI didn't know that feature in LTSpice. I guess I'll explore it then.

author: Ian.M
author_rank: Super Contributor
timestamp: August 23, 2017, 06:43:39 am
content: Its using an undocumented feature of PWL() - any time with a + in front is relative to the previous time, which makes it *MUCH* easier to describe waveforms like yours. Seehttp://ltwiki.org/index.php5?title=Undocumented_LTspicefor more stuff that never made it intp the help file.
Learning PIC "language" for a complete noob - Page 1
Forum section: electronics / beginners

author: joblessalex
author_rank: Contributor
timestamp: September 04, 2012, 07:16:38 am
content: Hello guys! I just picked up a kit and have a lovely PIC16F627 in it to program. I have no idea where to start, and Google turns up more gibberish than I can understand! The kit came with absolutely no documentation, and I had to solder things in by one overhead picture of the stupid thing! Needless to say it works, but where to go for beginner programming lessons? I know a bit of things on Arduino, but no real coding. Thanks! Also, if you see this Dave, UNBLOCK ME ON YOUTUBE! (please?) I don't know what I did, but I can't comment anywhere!

author: Rerouter
author_rank: Super Contributor
timestamp: September 04, 2012, 07:35:40 am
content: http://www.winpicprog.co.uk/pic_tutorial1.htmmay as well start off where you most likely began on arduinos, hope it helps

author: notsob
author_rank: Frequent Contributor
timestamp: September 04, 2012, 07:59:02 am
content: Here's a couple of places to start PIChttp://www.gooligum.com.au/tutorials.htmlhttp://www.pcbheaven.com/picpages/CheersPeter

author: Bloch
author_rank: Unknown
timestamp: September 04, 2012, 08:09:06 am
content: Quote from: joblessalex on September 04, 2012, 07:16:38 amA noob and "no documentation" is a bad combinationI would suggest buy a Pickit2 or Pickit3http://www.microchip.com/pickit3

author: amyk
author_rank: Super Contributor
timestamp: September 04, 2012, 08:23:05 am
content: As always, refer to the datasheet to get really familiar with all the subsystems.http://ww1.microchip.com/downloads/en/devicedoc/40300c.pdfDon't forget to look over any errata too.

author: Colin55
author_rank: Contributor
timestamp: September 05, 2012, 11:37:16 pm
content: http://www.talkingelectronics.com/has all the resources you need.

author: joblessalex
author_rank: Contributor
timestamp: September 08, 2012, 12:52:49 am
content: Thank you for all of the information! I will be getting the kit in a while after returning the dogey kit I got! It only works on legacy serial ports, not adapters and as such was useless!

author: westfw
author_rank: Super Contributor
timestamp: September 08, 2012, 01:35:06 am
content: http://jaluino.org/?I second the recommendation for WinPicProg...(People underestimate how important the USB port on Arduino was. Or the bootloader in general.)Another suggestion: USB Bit Whacker.
Learning resources - Page 1
Forum section: electronics / beginners

author: Jebnor
author_rank: Regular Contributor
timestamp: June 15, 2013, 06:06:45 am
content: I thought I would start a thread about learning resources we have found.I found a bunch of lectures from EE courses. I like them.Electronics For Analog Signal Processing - Ihttps://www.youtube.com/course?list=EC4E1A7D28A90C9B41Just go tohttps://www.youtube.com/user/nptelhrd/and search for "Electrical". It seems they have their entire EE course on there. ( And some other stuff as well)I now have 100+hrs of courses to watch.

author: Jebnor
author_rank: Regular Contributor
timestamp: June 15, 2013, 06:26:26 am
content: Or I could put it in that Sticky thread...
Learning RFID - Page 1
Forum section: electronics / beginners

author: Sivand12
author_rank: Contributor
timestamp: November 18, 2014, 11:23:27 am
content: Follow my posts as I discover RFID, please do comment on my posts with suggestions. =]http://theelectronicbyte.wordpress.com/2012/10/17/decoding-the-unique-identifiers/
Learning RFID - Page 1
Forum section: electronics / beginners

author: Mprentice1
author_rank: Newbie
timestamp: October 17, 2012, 03:00:35 pm
content: Follow my posts as I discover RFID, please do comment on my posts with suggestions. =]http://theelectronicbyte.wordpress.com/2012/10/17/decoding-the-unique-identifiers/
Learning the Art of Electronics 2016 as companion for 2nd edition TAOE - Page 1
Forum section: electronics / beginners

author: Ducttape
author_rank: Regular Contributor
timestamp: October 15, 2016, 02:13:57 pm
content: I have the 2nd edition of 'The Art of Electronics' and I'm considering buying the latest (2016) version of 'Learning the Art of Electronics' to supplement it. Is LTAOE 2016 essentially as useful with the 2nd edition TAOE as it is for the 3rd?
Learning The Art Of Electronics parts needed per lab - Page 1
Forum section: electronics / beginners

author: congruentsquare
author_rank: Contributor
timestamp: May 01, 2018, 02:31:46 pm
content: *

author: rstofer
author_rank: Super Contributor
timestamp: May 01, 2018, 03:15:36 pm
content: The problem may be delivery time.I would look at the complete parts list and buy ALL of the inexpensive parts (resistors, capacitors, switches, pushbuttons, LEDs, etc) in one order. The specialized components, used for one or two experiments, might get ordered just ahead of the experiment.Digikey has a shopping list:https://www.digikey.com/en/resources/edu/harvard-lab-kitOver the years, I have bought resistor and capacitor assortment kits from Jameco. It's nice to have basic components on hand and well organized. The parts are a lot cheaper on eBay and if a storage method can be found, this will be cheaper and just as good as the Jameco assortmentshttps://www.jameco.com/z/00081832-540-Piece-1-4-Watt-5-Carbon-Film-Resistor-Component-Kit_81832.htmlThere are several kits at Jameco.

author: congruentsquare
author_rank: Contributor
timestamp: May 01, 2018, 03:49:11 pm
content: *

author: rstofer
author_rank: Super Contributor
timestamp: May 01, 2018, 09:06:16 pm
content: I get my parts in 3 or 4 days from DigiKey. I don't tend to buy off of eBay, I have enough problems getting my stuff to work to be having to think about fakes. And delivery from China can take a VERY long time.Even with the fast delivery from DigiKey, my short attention span will drift before the parts get here. I need a good stock of general stuff sitting right here.I think your list will be very helpful. A lot of people ask about the parts for LTAOE so maybe it will get promoted to a 'sticky'.
Learning to use QUCS-s - Page 1
Forum section: electronics / beginners

author: sidereal
author_rank: Contributor
timestamp: January 15, 2023, 02:52:06 pm
content: HiI am trying to learn how to use QUCS-s on linux with ngspice backend.My simulation is attached. I am trying to add a DC simulation of a simple transistor powered RC oscillator circuit. However, I get the errorNgspice started...Error on line 11 or its substitute:q2 v2_out _net2 0 1could not find a valid modelnameSimulation interrupted due to error!Note: No ".plot", ".print", or ".fourier" lines; no simulations runNote: No compatibility mode selected!A picture of how I set out the simulation is also added.Can anyone please tell me where I am wrong? Thank you.
Learning Transformers - How to see Phase on Scope - Page 1
Forum section: electronics / beginners

author: K1JOS
author_rank: Regular Contributor
timestamp: February 19, 2015, 05:22:41 pm
content: I am learning about transformers and the phase changes between primary and secondary and buck/boost examples. I would like to put these signals on my scope. I have a 115vac primary xfrmr with several low voltage secondary's. What is the preferred method to compare the phase changes on a scope? Is the scope probe high enough impedance that I could put the probe tip on the primary hot and the probe ground on the neutral? Should I instead use an isolation transformer to supply the transformer primary?

author: AG6QR
author_rank: Frequent Contributor
timestamp: February 19, 2015, 07:02:03 pm
content: Be very careful here. See one of the "how NOT to blow up your scope" videos or threads.The ground clip on your scope's probes is grounded through the scope's mains plug. The neutral wire isn't quite exactly the same as ground, though they should be connected at the service entrance. But if there's any current flowing through neutral, its potential isn't the same as ground potential, due to V=IR and the fact that the neutral wires aren't zero resistance. If there is a GFCI protecting the circuit, it should trip as soon as your scope probe provides an alternate path for some current to leak to ground.If you connect the ground clip on a scope probe to a hot lead instead of neutral, something is going to go BANG! If you're lucky, it'll only be your scope that dies.An isolation transformer can help somewhat, but it comes with its own safety issues which you should understand. As soon as you ground one point of the DUT using the scope probe ground, then the DUT should no longer be considered isolated. If you connect the scope probe clip to some point on the device that has a voltage relative to the main chassis/frame, it's possible you could get a shock by touching the chassis with one hand while touching a grounded point (for example, a shield on a piece of test equipment) with the other.I won't say it can't be done, but it does require extreme caution and understanding of the issues.If the purpose is for learning about transformers, I'd recommend starting with a UL listed low voltage transformer, a "wall wart" or something of the type used for landscape lighting, irrigation sprinklers, or other small stuff. These usually put out something like 12 to 24VAC, with a fairly modest current limit. Use that as your source of AC, and do your experiments on a transformer that's starting with that low voltage, low energy AC. The theory is the same at lower energy levels.

author: K1JOS
author_rank: Regular Contributor
timestamp: February 19, 2015, 07:10:37 pm
content: Perfect... many thanks. Why don't they put a low current fuse on the scope probe ground lead?

author: electr_peter
author_rank: Unknown
timestamp: February 19, 2015, 10:31:43 pm
content: Quote from: K1JOS on February 19, 2015, 07:10:37 pmIt will compromise high BW performanceit is not needed with proper measurement setup andblown fuse can create very dangerous situation in some cases.
Least-significant digit accuracy at low end of range - Page 1
Forum section: electronics / beginners

author: grenert
author_rank: Frequent Contributor
timestamp: January 27, 2011, 06:00:38 am
content: My understanding from the EEVblog on accuracy/resolution is that accuracy specs are made at full scale. Does the +/- LSD spec change at the low end of the scale? For example, if a 2000-count meter is specified as 0.1% accuracy +/- 5 counts, does that mean on the 200 V range a measurement of 1 V could appear on the meter as anywhere from 1.5 to 2.5 V? That's an effective error of 50%!

author: Bored@Work
author_rank: Super Contributor
timestamp: January 27, 2011, 07:04:04 am
content: You talk about digital multimeters, right?Typically, specs are given as +/- (percentage of reading + Digits). Where Digits is another way to express percentage of nominal full scale value, or LSDs. The Digits rating doesn't change at low measurement values.Therefore, one of the golden rules of using a meter is to try to use a range where your value is in the upper 2/3 of the full scale of that meter.

author: saturation
author_rank: Super Contributor
timestamp: January 27, 2011, 01:23:22 pm
content: With that much drift, zero volt input to the DMM can cause it to fluctuate between 200.5 and 199.5 making resolving 1V on the 200V scale unhelpful.But, using the same specs on a 20,000 count DMM you'd have:200.05 to 199.95 at zero input,and at 0.1% accuracy 1V would be 0.999 to 1.001 and it would now be viable, with readings somewhere between 200.95 - 201.05, for about 5% total error.Quote from: grenert on January 27, 2011, 06:00:38 am

author: Unknown
author_rank: Unknown
timestamp: January 27, 2011, 07:50:21 pm
content: Quote from: grenert on January 27, 2011, 06:00:38 amNo.Quote from: grenert on January 27, 2011, 06:00:38 amCorrect. It's x% of value + y% of full scale (often expressed in digits). At the bottom of the range, the second term will become the most significant. You should use the lowest range possible, like BoredAtWork wrote. This will give you both better accuracy and better resolution.
Leave a firewire device plugged in when not in use? - Page 1
Forum section: electronics / beginners

author: danhaun
author_rank: Newbie
timestamp: April 17, 2022, 12:23:30 pm
content: I use Canopus (Grass Valley) ADVC-55 video converters to digitize the output of some vintage but high quality microscope cameras with great results. For some practical reasons beyond cost, these out perform available digital cameras. The problem is that these converters are Firewire devices designed to convert VHS tape to digital, they are no longer produced or supported. I would like to keep them operational for as long as possible. I have two working ones and two that were working but then suddenly stopped converting. I usually keep them plugged in to the computer all of time. I've done this for 11 years to one box that recently quit on me, so I am now questioning that practice. One of the functional boxes seems to want to warm up before it will convert video andI am wondering if this is sign that it too will fail. Two of the large chips on the board are very warm to the touch even when not converting video. I have-read on line about failing capacitors over time and wonder if it better to remove the power source.My question: Should I unplug when not in use? Is there anything else I should be doing to make them last? and finally What about repair options? Should I consider this or instead try to buy up a few more spares on eBay? Would that even help if components fail over time?Sorry if this are dumb questions. My expertise is in laboratory science. Thanks in advance for any advice.

author: Faranight
author_rank: Unknown
timestamp: April 17, 2022, 01:42:21 pm
content: I'm not sure about Firewire, but I learned a lot about failed components and repairs from watching this guy on youtube.Here's a video how he finds and replaces failed caps on laptop motherboards:Things are definitely fixable. If you have a donor board you can desolder some spare parts and replace the failed ones on another board.
Lecroy 6100A 1GHz oscilloscope weird screen thing - Page 1
Forum section: electronics / beginners

author: Ammar
author_rank: Regular Contributor
timestamp: September 08, 2017, 10:05:28 am
content: Hello,I have a Lecroy 6100A 1GHz oscilloscope. All of a sudden, the screen started to display a sort of kaleidoscope of the waveform. I have tried lots of settings, but I have no clue what is going on. It seems to depend on the time base.I am feeding in a 1MHz sine wave to create the plots below. What the?

author: lukier
author_rank: Unknown
timestamp: September 08, 2017, 10:52:54 am
content: You have sequence mode enabled + one of the many kinds of sequence display modes (I forgot their names) - this could result in seeing a part of the sine rising 10 times on the screen.
Lecternette model> L40-10A Vintage powered podium... the serial is 170028 - Page 1
Forum section: electronics / beginners

author: flanger
author_rank: Newbie
timestamp: January 11, 2024, 03:05:02 pm
content: I have a Lecternette model> L40-10A Vintage powered podium... the serial is 170028, I got it from a thrift store. It works great - I plug a microphone in the top and play harmonica through it. My question is, there are a bunch of spots is the back of the amp, that I would like to possibly use - especially the sockets for attaching more speakers too. I have never seen those type of speaker connectors, how would I go about using them? Thank you for any help! here are some photos to see the amp...
LED 10V dimmer - Page 1
Forum section: electronics / beginners

author: rthorntn
author_rank: Frequent Contributor
timestamp: April 18, 2022, 06:28:43 am
content: Hi,I got a LED lamp that has a dimmer capability, from what I have read it needs a "current source 10v dimmer".So it got me thinking can I just use a USB buck boost adapter to supply the 1-10v, it only needs 10ma?Thanks.Richard

author: Terry Bites
author_rank: Super Contributor
timestamp: April 18, 2022, 03:14:51 pm
content: The 0-10 or 1-10 volts is a control protocol. Its a just a control voltage . This voltage can be applied to multiple bulbs or LED current source PACKS at the same time.In the instance of your diagram, the current source is inside the bulb assembly. Some bulbs need a separate constant current source or DC voltage supply. Dimmable power packs often contain the 10V regulated supply so all you need is a pot.

author: tepalia02
author_rank: Regular Contributor
timestamp: April 20, 2022, 03:37:12 pm
content: I think you need a constant current LED driver.

author: rthorntn
author_rank: Frequent Contributor
timestamp: August 24, 2022, 04:23:26 am
content: This is the PCB of the 0-10V DC dimmer, this works with my lights but I'm not super happy with it and want something that has a bit better "resolution" and "range".The pot starts at 0°, clicks on at 40° and turns to about 280°. I think a multiple turn pot would be a good start, something "digital" would be even better, maybe even so something that I can preset?Has anyone seen anything off the shelf?Or something I can DIY with an MCU with code available?Thanks!
LED  and diode Hysteresis - Page 1
Forum section: electronics / beginners

author: MathWizard
author_rank: Super Contributor
timestamp: January 26, 2021, 06:58:51 pm
content: I was reverse engineering a circuit that uses some LED's, not just for looks, and so I was looking closer than ever before, at the I/V curve data, w/ a PSU and DMM, to figure some BJT biasing.And then I found something I must have forgot about, the hysteresis path nature of LED's. The I- vs V values, are lower on the way up before the threshold , and then the current remains higher, as the voltage is decreased again.So this can be used as Schmittcht trigger.So how much hystersis is there in other diodes ? I guess it's related to capacitance and semi-conductor physics, depletion regions and whatever....maybe it just a temperature thing tho too, that gets exaggerated when it coldI think I've heard hysterisis of fast recovery diodes in SMPS, and probably LEDs too. I don't think I ever heard anyone mention it about jelly bean low voltage, low freq. diodes.So is it just really small, even compared to an LED ?The Red 5mm LED I checked had endpoints at 693uA 1.85V (2.5mA on the way back) and + something over 15mA @ 2.06V, on the way up.GRN 5mm LED was 735uA @ 1.95V (and 2.3mA on the way back), and threshold about 2.17V, currents shoots to around 11mA

author: Ian.M
author_rank: Super Contributor
timestamp: January 26, 2021, 07:22:55 pm
content: Sounds like thermal effects - heat up the junction by passing current through it and its Vf drops proportionally to the tempoerature increase, until it has cooled again. Datasheets usually state that characteristic curves that pass significant current through a junction were taken with low duty cycle pulsed techniques, e.g. power on for 100us to make the measurement, then off for the rest of a 100ms interval for a duty cycle of 0.1% and corresponding reduction in self heating.

author: Benta
author_rank: Super Contributor
timestamp: January 26, 2021, 08:39:27 pm
content: Reminds of the time (late 1970s) when I invented the bicolor LED: 10 mA current: green. 1 A current: red (bond wire).

author: MathWizard
author_rank: Super Contributor
timestamp: January 26, 2021, 09:36:22 pm
content: See when I 1st was measuring the red LED, I got up to 2.050V w/2.1mA, and then hit it jumped, and the 15mA current limit I had set, kicked in. And also, my DMM changes range too.So latter after posting, and the LED has warmed up a nice while, I'm not seeing that same jump, ....but it still was like hystersis some, but I guess thermal.Yeah yesterday, I made red from a green LED with too much signal strength, I've hardly burned out any, but then I shorted the LED right after by accident. At least they don't explode.Why do they have such large/tough leads, for through hole, compared to most other stuff? Is it just for mechanical strength in the types of exposed places LEDs get placed ?

author: srb1954
author_rank: Super Contributor
timestamp: January 28, 2021, 01:55:21 am
content: Quote from: Benta on January 26, 2021, 08:39:27 pmWith a little bit more current you could have also invented the monostable (one-shot) pulsing red LED.
LED  avrerage power - Page 1
Forum section: electronics / beginners

author: radel
author_rank: Newbie
timestamp: October 20, 2015, 08:14:07 am
content: Hi everyone,I am using LED Vf=3v and If=700mA. This LEDs used some light array project as flashing leds simultanously.i will turn on 15 LEDs at a time. 5x3 (5rows and 3 coloum) matrix.Duty cycle is 667msON time=165mSOFF time=502mSLES are 2W rated .please help to find Average power of LED.::

author: tron9000
author_rank: Frequent Contributor
timestamp: October 20, 2015, 08:21:06 am
content: your duty cycle isn't 667ms, that's your freqency, from your on & off times your duty cycle is:165ms / 667ms = 0.25 or 25%P = IV; so considering you LED is on for 1/4 of the time...your power should be....(i'm not giving you the answer...I want to know if you can figure it out, least then I know what level your at)

author: alsetalokin4017
author_rank: Super Contributor
timestamp: October 20, 2015, 02:47:31 pm
content: Since we are being pedantic....667 ms isn't a frequency, it's a period. The units of frequency aren't seconds, they are cycles per second, ie Hz. Frequency is 1/period (and period = 1/frequency) so the frequency is.....(left as an exercise for the reader...)

author: tron9000
author_rank: Frequent Contributor
timestamp: October 20, 2015, 03:11:02 pm
content: true yes, incorrect terminology on my part, apologies (In my head I see period and get frequency), but something that the OP could figure out.Hardly being pedantic - there's a difference between knowing the answer and being shown how to get the answer. One's transferable knowledge, the others just reciting.
LED backlight driver - Page 1
Forum section: electronics / beginners

author: Kaisha
author_rank: Contributor
timestamp: December 07, 2021, 12:40:00 pm
content: Been trying to put together an LED backlight driver for a small LCD screen (https://www.buydisplay.com/download/manual/ER-TFT032A3-3_Datasheet.pdf). The backlight runs at 3.2v, 100mA. I'll be running this off a pair of lithium ion batteries in series (ie. 10V-6V range). I was going to have the board made at JLCPCB with their SMT service.I've been looking through all the led drivers they have available and none seem to be usable. All the led buck converters require a very large power inductor, often in the 100's-1000s of uH given the low power draw of the backlight (it seems, counterintuitively, that the lower the current draw, the larger the inductor). The buck regulators that do support lower current draw (have a 'skip mode' or 'eco mode') are all constant voltage regulators, not constant current.Are there any led buck drivers (preferably with some sort of dimming) that would work for my situation? This seems like a pretty basic application, I'm not sure why I'm finding it so hard to find a decent part.

author: Steffalompen
author_rank: Contributor
timestamp: December 07, 2021, 01:52:31 pm
content: Something like this?https://lcsc.com/mobile/product-detail/LED-Drivers_Analog-Devices-LTM8042EV-PBF_C108029.html

author: madires
author_rank: Super Contributor
timestamp: December 07, 2021, 02:12:40 pm
content: Have you tried Digikey's parametric search?

author: Kaisha
author_rank: Contributor
timestamp: December 07, 2021, 02:15:06 pm
content: I appreciate the input, but if I'm reading the datasheet correctly, it doesn't support leds below 170 mA. It's also a tad pricey (12$) and quite large for fitting on my pcb.I imagine it has the same problem, smaller current draws require larger inductors unless 'skip mode' or 'eco mode' type of buck converter is used.

author: Kaisha
author_rank: Contributor
timestamp: December 07, 2021, 02:16:30 pm
content: Quote from: madires on December 07, 2021, 02:12:40 pmNo I did not, I just went through the jlcpcb SMT catalog, then the Texas Instruments and Analog websites.

author: madires
author_rank: Super Contributor
timestamp: December 07, 2021, 02:21:52 pm
content: I strongly recommend the parametric search function offered by several distributors. It's a great tool to find parts.

author: Kaisha
author_rank: Contributor
timestamp: December 07, 2021, 02:50:51 pm
content: Quote from: madires on December 07, 2021, 02:21:52 pmI will give it a try.
led backlight tester - Page 1
Forum section: electronics / beginners

author: glinjik
author_rank: Regular Contributor
timestamp: February 21, 2020, 08:41:44 pm
content: hi i was watching utube videos about building a TV backlight tester first schematic i found plain dont work so was in the posses of building another variant based on 555 timer when a friend gave me a electronic ballast/evg model sh70-z hep group 240vac in 350v out which is about the same as the scheme i was making my question is will this thing be suitable or am i going to get the biggest shock so far?
Led Bulb Blinking Problem & IC thermal shutdown (TSD) protection - Page 1
Forum section: electronics / beginners

author: sdancer75
author_rank: Frequent Contributor
timestamp: February 11, 2020, 04:58:54 pm
content: This specific G4 Led bulb starts blinking after almost 5 years of work.Checking the components in the PCB, everything seems to be OK, except the LED driver ( PT4115 ) where the built-in thermal shutdown (TSD) protection system shuts the functionality of the IC to protect it.So my question is if the PT4115 IC Led Driver is now almost dead since its itself protection system seems to be malfunctioning after all these years of working or if there is another reason that causes the IC to over-temperature and that I should look for.Thanks
LED bulb in wooden enclosure -- safe? - Page 1
Forum section: electronics / beginners

author: pfleenor
author_rank: Newbie
timestamp: December 14, 2018, 07:59:41 pm
content: I'm planning to build a wooden & epoxy lamp similar to thishttps://www.pinterest.com/pin/71705819045683574/There are tons of youtube videos of builds but no one mentions if heat of the light is a factor and I'm having a hard time figuring it out.There won't be any holes in the wood for ventilation. Would something like this work to embed beneath the epoxy?https://www.ebay.com/itm/Original-CREE-10W-XML-L2-Warm-White-LED-Chip-Base-For-Flashlight-Torch-Light/152933793046?hash=item239b907d16:m:meS570C_z-EvE71_T3eo5kQ:rk:36:pf:0&var=452699757422If not what low-heat led light could I safely use?Thanks

author: Wimberleytech
author_rank: Super Contributor
timestamp: December 14, 2018, 08:35:31 pm
content: Quote from: pfleenor on December 14, 2018, 07:59:41 pmI do not believe there is a safety issue because the Cree only dissipates 10 watts. However, if the resin does not move the heat away from the LED, it will kill itself over time. So success or failure depends in part on the thermal conductivity of the resin.That is my SWAG at your question.

author: james_s
author_rank: Super Contributor
timestamp: December 15, 2018, 01:04:25 am
content: I've seen plenty of wood light fixtures using old fashioned scorching hot incandescent lamps so you'll be fine. The LED will fail long before it approaches the char point of wood.

author: Brumby
author_rank: Unknown
timestamp: December 15, 2018, 02:17:17 am
content: Getting heat away from the LED is going to be a key factor for the long term survival of the LED. Even a 1W LED produces enough heat to self destruct in a relatively short time. You will need the LED mounted on a heatsink whatever you do. The LED you linked to is already mounted on a thermally conducting plate - but it really needs a way for the heat to escape. Mounting to a larger heatsink is usual - which is what the slots are for.You don't necessarily need air flow inside the fixture, but it would be good if there was a way for the heat to be taken away from the LED. A big strip of metal to extend the heatsink mass will help and if it can find its way to the outside air, then that would be very beneficial. Perhaps you could make it a feature. If a large enough area in itself, it may not need to be finned - because that's all the fins do: increase the surface area to the ambient air.You are spot on with asking this question, though. Heat is the number one issue with electronics.

author: pfleenor
author_rank: Newbie
timestamp: December 17, 2018, 02:37:52 am
content: Thanks for the replies. I could surely incorporate a way for heat to get out/dissipate. I'll see what I can come up with.

author: cdev
author_rank: Super Contributor
timestamp: December 17, 2018, 02:43:50 am
content: Run the LED at a lower voltage and its likely to stay much cooler and last a lot longer right there. Derating them a small amount makes a huge difference in their useful life span.
led bulbs - Page 1
Forum section: electronics / beginners

author: glinjik
author_rank: Regular Contributor
timestamp: January 24, 2020, 11:32:40 am
content: hi i have led bulbs throughout my house but what I've noticed is they blow very often i have also the spiral eco bulbs as well they never blow what I've noticed is we get light flicker usually in the evening the voltage at 9 this morning was 240.5vac now its 2401.6vac evening it can get as low as 210vac im wondering is the flicker coming from voltage spikes? Thinking about this is it a possibility to add y caps to the bulbs to try to avoid these spikes blowing the bulbs just a theory as I'm writing this I've got the fluke on auto hold monitoring the vac its just jumped to 238.9vac

author: wraper
author_rank: Unknown
timestamp: January 24, 2020, 11:38:23 am
content: Probably you just have crappy bulbs with no real LED driver. Point smartphone camera towards a bulb and see if there is any flickering on display.

author: glinjik
author_rank: Regular Contributor
timestamp: January 24, 2020, 11:49:41 am
content: Just tried the camera thing in video and still photo 26mp camera cant see a flicker I'm using bulbs of all brands the one that blew today is старт. сделано в Китае

author: glinjik
author_rank: Regular Contributor
timestamp: January 24, 2020, 11:53:53 am
content: clearly blown cap and 3 led

author: Psi
author_rank: Super Contributor
timestamp: January 24, 2020, 11:58:05 am
content: I'm working through replacing led lamps in each room with recessed WWA LED strip.Warm white , Cool White, Amber.Unlike your typical LED lamp that runs very hot. An LED strip can last for 10+ years if you keep them running cool.

author: glinjik
author_rank: Regular Contributor
timestamp: January 24, 2020, 12:03:49 pm
content: ive used led strips before but only on 12v direct from solar battery in fact my solar lights have never blown in each room i have 240v and 12v lights we get a lot of power cuts so use the solar system only on cuts

author: glinjik
author_rank: Regular Contributor
timestamp: January 24, 2020, 12:43:51 pm
content: a quick semi fix new cap and bypass the 3 led works great ok for garage maybe there ato solder though
LED choice - Page 1
Forum section: electronics / beginners

author: vyshak
author_rank: Newbie
timestamp: January 01, 2014, 06:47:03 am
content: I am doing a project on path tracking using image processing and I need to use LED s for tracking path.from the image taken with slow shutter speed camera.i have 3 LED of different color close to each other. For distinguishing them properlly what type of LED will be best suited.

author: Rerouter
author_rank: Super Contributor
timestamp: January 01, 2014, 07:54:28 am
content: red green and blue, though you will want a bright red, or to dim the green and blue quite a bit. to level them out

author: vyshak
author_rank: Newbie
timestamp: January 02, 2014, 02:59:04 am
content: thanks...is there any specific led series that suits for my project.??

author: Rerouter
author_rank: Super Contributor
timestamp: January 02, 2014, 03:42:50 am
content: as your tracking it with a camera, you should be able to work out how much light you need,if you need accurate positioning use waterclear leds, noting that they will appear dimmer at an angle but will be a very tight point light source,if you need crude positioning, look for wide diffused led'sas for a specific make and model, i cannot say, i have never done any active tracking, only long shutters on a fixed area,
Led color temperature problem  - Page 1
Forum section: electronics / beginners

author: MesharyHD
author_rank: Newbie
timestamp: May 09, 2018, 06:43:50 am
content: Hello eev communityI'm having problem to find the color temperature for this devices like the nokia 8850 or the ipob mini. (picture attachment for color reference)1https://pre00.deviantart.net/2dad/th/pre/f/2016/226/6/5/nokia_8850_by_redfield_1982-d89ydsx.png2https://www.gadgetmenders.com/images/64gb-ipod-mini-silver-2nd-gen-ssd-flash-upgrade-new-battery-wolfson-dac-30gb-3.jpgI have tried to get my led's from AliExpress which some sellers claimed to be cool white but it wasn't.Can anyone help me to finde these rare smd LED's 1206 0805

author: ogden
author_rank: Super Contributor
timestamp: May 09, 2018, 07:07:42 am
content: Here you go:https://www.findchips.com/search/SML-LX1206UWW-TR

author: MesharyHD
author_rank: Newbie
timestamp: May 09, 2018, 07:22:56 am
content: i have looked into the led's specification from the link you gave me i could not find one listed as 10000k color temperature

author: MesharyHD
author_rank: Newbie
timestamp: May 09, 2018, 07:53:39 am
content: I just have understand this led is determined by X and Y coordinates so I think this is more accurate way to point the colour temperature on a graph

author: ogden
author_rank: Super Contributor
timestamp: May 09, 2018, 02:51:02 pm
content: Quote from: MesharyHD on May 09, 2018, 07:22:56 amThat link was more about places where you can look for LED's that one particular LED I searched for.

author: Jwillis
author_rank: Super Contributor
timestamp: May 10, 2018, 04:14:17 am
content: LEDs are normally rated in nano meters of the band width of light they emit .On the visible spectrum red is the lowest at 620 < λ < 645 nano meters and blue the highest at 460 < λ < 490 nano meters.Although we can't see UV light it does enhance brilliance to the broad spectrum .White leds are a broad spectrum of either Blue/UV diode with yellow phosphor for Cool / Pure White or Blue diode with orange phosphor for Warm White or RGB color mixing but RGB LEDs leave gaps in the spectrum .Because of these limitations LEDS don't have a kelvin rating .Other sources of light like halogens can be adjusted very finely by changing the amounts of various gases to achieve varying warmth's hence a broad range in kelvins.

author: MesharyHD
author_rank: Newbie
timestamp: May 10, 2018, 04:56:00 am
content: Quote from: Jwillis on May 10, 2018, 04:14:17 amThank you that was helpful i was looking inwww.masterelectronics.comLED filter and i found they listed the Color Temperature with k and x,y values which this graph can explain ithttps://upload.wikimedia.org/wikipedia/commons/thumb/b/ba/PlanckianLocus.png/1200px-PlanckianLocus.pnghowever i found some SMD led colors very exclusive to big tech big companies.
LED controller - Page 1
Forum section: electronics / beginners

author: Dexter12353
author_rank: Newbie
timestamp: November 16, 2014, 09:58:50 pm
content: We are installing some of these LED tape strips. The led strips look like this:They run on 12 volts DC.From china for about 5 bucks, you can get these remote controllers that can make flashing effects, fading, brightness, etc. They adjust the brightness via PWM.These remotes only have enough bang (limited to .5 amps) to run 20 feet of these lights. We would like to run approximately 80 feet (4 strings, all starting at the same point, imagine + shape)These remotes have a common positive buss, and they switch the negative.Some screenshots of the controller/remote module:Top w/drawing:Top w/o drawing:Bottom w/ drawing:Bottom w/o drawing:I have investigated Solid State Relays, but they are expensive. I have some 2n3055 transistors laying around, and various resistors/capacitors, and I was wondering if I could build a circuit with the transistors to increase the maximum amperage. I am not very experienced with building circuits, so that's why I've come here for help.Thanks for all of your time!

author: David_AVD
author_rank: Super Contributor
timestamp: November 16, 2014, 10:02:41 pm
content: You can also buy "RGB Amplifiers" very cheaply (< $10) from eBay or China direct. The original controller feeds into the RGB amplifier and that can usually have up to 4A or 10A per channel on it's output.