hybridfree/eevblog-posts huggingface dataset:
Recent im/export problem purchasing super capacitor from chinese ebay suppliers - Page 1
Forum section: electronics / general

author: wb0gaz
author_rank: Frequent Contributor
timestamp: August 05, 2021, 01:46:09 pm
content: Moderators - not sure where to post this, so if this is not suitable for posting, please remove - thanks.I've tried several times this summer to purchase small number (=personal/hobby use) of super capacitors or super capacitor modules from various chinese suppliers on ebay and amazon. In all four of the instances so far since July 2021, the export process (from china to US) stopped (parts apparently never left china and returned to shipper), or supplier refused to initiate shipment in the first place (no purchase resulted in delivery). In all cases (except the latest one) the purchase was refunded (and I believe that one will be resolved with refund soon.) These parts still appear to be on sale from their various suppliers.I've searched online for any other discussion of this issue, and I can't find anything.Thanks for any comments/observations.
Questions battery Lipo - Page 1
Forum section: electronics / general

author: tiago1986
author_rank: Regular Contributor
timestamp: July 27, 2021, 07:57:23 pm
content: 1) How to find out if my Li-Po Xiaomi BM20 battery is genuine or fake?2) my battery has two protrusions, one in the center and the other appears in the upper corner, does this force me to dispose of the batteries in the trash? i put photos
HP 6060A voltage limits - Page 1
Forum section: electronics / general

author: robin@ganmartechnologies.
author_rank: Newbie
timestamp: March 23, 2021, 09:12:39 pm
content: HelloOur HP 6060A load has front panel limits pretty well known: 0-60v/0-60 ampBut on the back near the load connectors, we see "+/- 240 V" (with respect to GND) printed in solid black engraving surely from the original mfr.Does it mean it can handle 240V (wrt gnd) ? surely at <300W but +/- 240V gives it a whole new application!Anyone has experience with this application?Appreciate any clarification.r

author: megajocke
author_rank: Regular Contributor
timestamp: April 02, 2021, 07:43:02 am
content: That is a specification of how well the output is isolated from ground. The maximum voltage you are allowed to apply between the floating output and ground is +-240V.

author: BioEng
author_rank: Newbie
timestamp: July 29, 2021, 03:13:22 pm
content: I have a 6060A, No output and the front panel never changes from 0V or 0A. If I press the Display settings I can Adjust both Voltage and Current. but no output. Anybody got any Ideas? i have manuals and schematics.thanks Trev
Gap in metal enclosure for SMPS - Page 1
Forum section: electronics / general

author: Faringdon
author_rank: Super Contributor
timestamp: July 18, 2021, 07:44:11 pm
content: HiWe need to pass EN55032 with an offline isolated 20w flyback SMPS.We have an earthed metal screen all round it, apart from a 33mm by 8mm bit which is open. Will this be OK from a radiated EMC viewpoint?(After all, the 1GHz wavelength is 30cm.)

author: langwadt
author_rank: Super Contributor
timestamp: July 18, 2021, 08:39:24 pm
content: http://cdn.lairdtech.com/home/brandworld/files/EMI%20Rule-of-Thumb%20for%20Calculating%20Aperture%20Size%20Technical%20Note%20Download.pdf

author: TimFox
author_rank: Super Contributor
timestamp: July 18, 2021, 09:28:07 pm
content: Also, for a more general case, Google “waveguide beyond cutoff” for the penetration of an evanescent wave into a hole.

author: Faringdon
author_rank: Super Contributor
timestamp: July 20, 2021, 05:18:57 pm
content: Thanks, looks like a 33mm by 8mm gap ("slot") is going to let through to much radiation.I am wondering about doing some trick with inner layer copper to do the shielding across the isolation barrier?I wonder if an inner layer of secondary ground copper can be sneaked across the Offline SMPS isolation barrier to do the under-side shielding?(sec ground is actually earthed anyway)I doubt it would be violating regulations as its covered by FR4?...otherwise it'll be very awkward to get a metal enclosure to cover the entire Mornsun LS15-13B12 SS power module as it stands mounted on the PCB.Mornsun LS15-13B12 power modulehttps://www.mornsun-power.com/index/sitesearch/partlink/keyword/LS15-13B12SS.html

author: dmills
author_rank: Super Contributor
timestamp: July 21, 2021, 12:05:21 pm
content: Treez,How much energy are you actually making up in the UHF region?For a mains power supply application I would be somewhat surprised if there was much above low VHF, and you don't need to shield that which you do not produce.Usually my issues up where that slot radiator will screw you are more in the way of harmonics from video clocks and the like rather then harmonics from power converters.
Y caps better directly across transformer in offline flyback SMPS? - Page 1
Forum section: electronics / general

author: Faringdon
author_rank: Super Contributor
timestamp: July 17, 2021, 04:08:43 pm
content: Page 4 of the Mornsun LS15-13B12 power module (Offline flyback, 12vout, 15w out) shows a Y cap from primary ground to secondary ground. This is obviously for common mode filtration. But wouldnt it be better if it was actually fitted on the Mornsun PCB and placed right across the actual isolation barrier, immediately next to it?Mornsun offline power modulehttps://www.mornsun-power.com/html/pdf/LS15-13B12SS-F.html

author: voltsandjolts
author_rank: Unknown
timestamp: July 17, 2021, 04:13:25 pm
content: Please stop. Please.

author: jonpaul
author_rank: Super Contributor
timestamp: July 19, 2021, 01:28:12 pm
content: No reason, the module supplier is showing various safety and EMI components external to the module.Diffreent applications will demand different X, Y caps, fuses etc eg Japan/EU/USA or application areas, eg medical/broadcast/consumer/industrial.Jon

author: Faringdon
author_rank: Super Contributor
timestamp: July 19, 2021, 04:12:39 pm
content: Thanks, though you would agree, that Y caps across the isolation barrier need to be as near the transformer as possible?

author: Gyro
author_rank: Super Contributor
timestamp: July 19, 2021, 09:42:34 pm
content: Y caps are far more accessible in through-hole. You should have noticed that the Mornsun module is completely smt.
Multimeters cannot measure AM power signal - Page 1
Forum section: electronics / general

author: worldwideglide
author_rank: Newbie
timestamp: July 14, 2021, 12:48:32 pm
content: Hello,I am trying to get an RMS measurement of this waveform:It's amplitude modulated, fixed frequency @ 1.7MHz, and the amount of AM can vary. None of my multimeters like it (tried fluke and others). So far the only way I can get a measurement is with an oscilloscope on RMS setting, but this is not an ideal setup because we need to be able to take this measurement quickly and not have to set up a scope every time.Is there an easy way to get an RMS measurement of a signal like this that doesn't involve a scope?Cheers!

author: TimFox
author_rank: Super Contributor
timestamp: July 14, 2021, 01:46:36 pm
content: There are specialized RF voltmeters that can do a true rms voltage measurement, but is that the parameter you want for this measurement? A common parameter for modulated RF waveforms is PEP = "peak envelope power", which is the mean power associated with the voltage at the maximum excursion of the voltage. A peak-to-peak responding voltmeter (which can be built easily with two capacitors and two diodes) is more appropriate for that measurement.

author: Someone
author_rank: Super Contributor
timestamp: July 15, 2021, 12:18:05 am
content: rms of an RF signal, thermal power meter is your "cheap" and simple tool.

author: f4eru
author_rank: Super Contributor
timestamp: July 15, 2021, 10:04:01 pm
content: https://www.google.de/search?q=rf+wattmeter-> you have to convert back to voltage, but it's the correct tool.Same but with a disply in volts :https://www.google.de/search?q=rf+voltmeter

author: David Hess
author_rank: Super Contributor
timestamp: July 15, 2021, 11:26:20 pm
content: A sampling RMS voltmeter can make that measurement. In principle you can make one using a sample and hold of sufficient bandwidth and any RMS voltmeter.

author: worldwideglide
author_rank: Newbie
timestamp: July 19, 2021, 12:12:53 pm
content: I should probably add that what I'm measuring is the voltage applied to a nebulizer (water vaporizer). The 1.7MHz signal is to cause vibration and the AM is to set magnitude of vapor output.I found another post about this on the forum:https://www.eevblog.com/forum/beginners/info-about-rf-voltmeter/#:~:text=Assuming%20that%20RF%20stands%20for,anything%20above%20about%201%20MHz.Looks like the capacitor + diode method may be the best way to do this without buying something expensive
Newly discovered feature of the Chevy Bolt - Just revealed - Page 1
Forum section: electronics / general

author: DougSpindler
author_rank: Super Contributor
timestamp: July 18, 2021, 01:41:05 pm
content: Newly discovered feature of the Chevy Bolt - Just revealed, they catch fire when charging.GM recommends you watch the Bolt while charging. If you see smoke or fire GM recommends you discontinue charging the vehicle.https://www.theverge.com/2020/12/2/22135764/chevy-bolt-batteries-catching-fire-class-action-lawsuit

author: wraper
author_rank: Unknown
timestamp: July 18, 2021, 01:42:07 pm
content: Volt is a very different car, PHEV, not BEV.

author: DougSpindler
author_rank: Super Contributor
timestamp: July 18, 2021, 01:45:51 pm
content: My bd, I mixed up Volt, which I own and Bolt. - Thanks - Post has been corrected.
Looking for Power Supply - Page 1
Forum section: electronics / general

author: PixieDust
author_rank: Frequent Contributor
timestamp: July 06, 2021, 12:49:29 pm
content: Hi,I'm looking for a power supply for a Raspberry Pi type device. Question is, how do you know what power supply is good and which one isn't? What should you look for? Cheap Chinese ones make me sweat. I wish there was some sort of Computer PSU gold/platinum/silver rating.

author: Faringdon
author_rank: Super Contributor
timestamp: July 10, 2021, 08:34:56 pm
content: What vout and pout do you need?Also, what is your power source, Mains or battery?

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 10, 2021, 08:38:37 pm
content: Just get a good quality smartphone charger, for example Anker.

author: tunk
author_rank: Super Contributor
timestamp: July 10, 2021, 08:44:21 pm
content: Would this work:https://lygte-info.dk/review/USBpower%20Ikea%20Koppla%20UK.htmlhttps://youtu.be/uRe9w5PKmsE

author: Gyro
author_rank: Super Contributor
timestamp: July 13, 2021, 09:02:42 pm
content: Ikea stuff will at least be safe!Pi's tend to be rather sensitive about their supply voltage, it needs to be at the top end of the 5V tolerance range (up to 5.25V) for reliable operation, particularly if powering any Hats.The official Pi power supply is rated 5.1V @ 3A. Actually, why don't you buy an official one? They're not expensive and you'll have peace of mind.
Mains filter for Mornsun AC/DC power module ? - Page 1
Forum section: electronics / general

author: Faringdon
author_rank: Super Contributor
timestamp: July 11, 2021, 03:37:28 pm
content: The Mornsun LS15-13B12 AC/DC module datasheet (offline flyback , 15w) gives examples of mains input filters needed to be added to get through EMC compliance testing.However, I don’t see how they can give such examples, as many people will be connecting secondary GND to earth, which gives far worse radiated emissions. They haven’t shown the case of secondary GND being connected to earth, which is highly common amongst likely users of this power module.How can they give filter examples without stating whether or not the secondary GND is earthed?Mornsun LS15-13B12 AC/DC module datasheethttps://www.mornsun-power.com/html/pdf/LS15-13B12SS-F.html
Ferrite beads vs Common mode choke for EMC? - Page 1
Forum section: electronics / general

author: Faringdon
author_rank: Super Contributor
timestamp: July 09, 2021, 08:44:02 am
content: Hi,We all know how a single common mode choke is usually insufficient in an offline Flyback SMPS (10-70W). Common mode emissions can cause problems from 150kHz right up to 250MHz and beyond. No common mode choke can have good common mode attenuation over that bandwidth. As such, its normal to use a relatively large common mode choke of some 10mH or so, and to augment this with an upstream, smaller common mode choke, for the higher frequencies.As such, I chose the B82721K2282U030 common mode choke as our “high frequency” common mode choke, and the wurth 744862100 for the “low frequency” common mode chokeHowever, looking at the attenuation graph, it looks as if we would be better off by simply placing a ferrite bead (Wurth 74275143) in the Live and Neutral lines. (instead of the B82721K2282U030 common mode choke) Would you agree?B82721K2282U030 common mode chokehttps://product.tdk.com/system/file...c/line-filter/data_sheet/30/ds/b82721k2xu.pdfWurth 74275143https://www.we-online.com/catalog/datasheet/74275143.pdf
The easiest way of sourcing a nuclear fusion plant - Get it from Amazon! - Page 1
Forum section: electronics / general

author: Gyro
author_rank: Super Contributor
timestamp: June 17, 2021, 07:33:57 pm
content: It looks as if the UK may be in the running for being the first country to make it's own Sunshine.Quotehttps://www.bbc.co.uk/news/science-environment-575122292025 and $400M sounds pretty optimistic.

author: ucanel
author_rank: Regular Contributor
timestamp: June 17, 2021, 07:53:53 pm
content: ITER scheculed for 2025 but they started at 2005 with 35 nations and i think the budget is in billions $.https://www.iter.org/proj/inafewlinesThere are very good videos about it at youtube one of them shows the power stations app. Terawatthttps://youtu.be/cvsj0nqHwic

author: Gyro
author_rank: Super Contributor
timestamp: June 17, 2021, 08:12:18 pm
content: Quote from: ucanel on June 17, 2021, 07:53:53 pmYes, the article mentions private company frustrations with ITER timescale delays and that it isn't likely to be up and running until 2035. Maybe he has ambitions of being the Elon Musk of nuclear fusion - It's either going to show up the big boys, or be a massive money pit.Curious that it's planned to be 70% of the size of a commercial reactor though. I could understand a half scale prototype, but 70%? Why not go to 100% if you're building all that infrastructure.

author: gmb42
author_rank: Frequent Contributor
timestamp: June 18, 2021, 09:20:00 am
content: Quote from: Gyro on June 17, 2021, 08:12:18 pmThey're avoiding the infamous last 20% that always takes 80% of the time\cost by a safety margin

author: Gyro
author_rank: Super Contributor
timestamp: June 20, 2021, 06:45:15 pm
content: With the extra 10% margin for added luck, to help with the short timescale low budget. They ought to be able to come up with a 50% model more or less instantly!

author: Bassman59
author_rank: Super Contributor
timestamp: June 20, 2021, 06:51:47 pm
content: "it won't generate power ..." but what will it do?

author: BrokenYugo
author_rank: Super Contributor
timestamp: June 20, 2021, 09:39:13 pm
content: Quote from: Bassman59 on June 20, 2021, 06:51:47 pmDemonstrate gain >1 with the proposed technology I guess.

author: Whales
author_rank: Super Contributor
timestamp: June 20, 2021, 11:11:58 pm
content: Quote from: BrokenYugo on June 20, 2021, 09:39:13 pmCan I hook it up to my speakers? I've heard of a plasma tweeter. Maybe that's asking too much, I'll just use it as a mic pre-amp.
Feedback loop for ADP2303-5 - Page 1
Forum section: electronics / general

author: Faringdon
author_rank: Super Contributor
timestamp: June 20, 2021, 08:05:20 pm
content: Hi,We wish to use ADP2303-5 for a buck controller 12vin to 5vout at 3A.We wish to re--use BOM components.Therefore we want to use a 6.8uH buck inductor, and a 56uF/25v Al poly output cap.ADP2303-5 datasheet gives no mention of its internal error amp transfer function, or its modulator transfer function, therefore its impossible to calculate the feedback loop bode plots.Do you know how we can get this info?(LTpowerCAD is not useful as it wont let us select these component values together)
Boost converter: Where to best place CST? - Page 1
Forum section: electronics / general

author: Faringdon
author_rank: Super Contributor
timestamp: June 13, 2021, 07:56:39 pm
content: HiDo you agree the low side CST position is better since it means no overvoltage spiking to the FET?Also, the leakage inductance of the CST provides some reduction in gate drive dv/dt and thus improves EMC?PDF schems and LTspice sims of low-side and high-side CST positions attached

author: bob91343
author_rank: Super Contributor
timestamp: June 13, 2021, 08:34:06 pm
content: What is CST? When you use acronyms you fend off many potential replies.

author: uer166
author_rank: Super Contributor
timestamp: June 14, 2021, 12:29:31 am
content: Quote from: bob91343 on June 13, 2021, 08:34:06 pmBased on schematic CST==Current Sense Transformer, which is a stupid acronym. I've only heard Current Transformers abbreviated "CT".In any case, the high-side version is better electrically since there is no sense coil in the gate drive path, and no extra impedance.

author: Weston
author_rank: Regular Contributor
timestamp: June 14, 2021, 12:41:27 am
content: As said, inductance on the source slows down the switching.Also, for the same di/dt you get the same voltage spike due to leakage inductance. Except now its a negative voltage on the source instead of a positive voltage on the drain.Any reduction of DS voltage stress is going to be due slower switching caused by the added source inductance. If this is an issue, you might as well just slow down the gate drive with a gate drive resistor, that's more adjustable.Additionally, Treez/ocset, if you are going to keep creating alt accounts to get people to do your job for you consider changing your phrasing so its not immediately obvious

author: Faringdon
author_rank: Super Contributor
timestamp: June 14, 2021, 04:44:30 am
content: Thanks, ..are there any other ways to get high bandwidth current sensing like this, other than using a sense resistor?Eg, any really fast Hall type sensors.As you know, its needed to depict the trapezoidal fet current very accurately (for current mode control) and without filtering it too much.Ive heard of people using a really low value sense resistor and then amplifying this with a really fast op-amp, have you heard of this?

author: pwrtrnx
author_rank: Newbie
timestamp: June 20, 2021, 07:33:35 am
content: We design boost converters to 6.6kW, we have always put the CT in the drain - for lots of good power electronics reasons.
temperature and voltage keep battery lipo - Page 1
Forum section: electronics / general

author: tiago1986
author_rank: Regular Contributor
timestamp: June 20, 2021, 03:26:00 pm
content: 1) the temperature in my home ranges from 31-34°C for maximum long term storage is it better to keep Lipo at 3.85V or lower it to 3.6V??2) If I don't have the smartphone and the original charger To charge discharge a xiaomi BM20 and Nokia BP-5L battery what is the best option?

author: Siwastaja
author_rank: Super Contributor
timestamp: June 20, 2021, 03:42:17 pm
content: Hello again.3.85V is good. 3.6V is even better. I suggest you print this out, frame it and put it on your wall.For 2), there is no good answer. If you know how, you can design a good charger but that's a lot of work and requires competence. Another option is getting the original smartphone, that's definitely the easiest way to get the proper charger circuit and proper contacts for the battery. Third option is use some Aliexpress crap which may or may not work and may be lethally dangerous to use.

author: tunk
author_rank: Super Contributor
timestamp: June 20, 2021, 04:43:54 pm
content: Please, this is your third thread with more or less the same question.The reason for not getting more answers is that there are no definiteanswers to your question, only rough guidelines. And these has beenprovided in your other threads.

author: tiago1986
author_rank: Regular Contributor
timestamp: June 20, 2021, 05:38:25 pm
content: I will lower the voltage to 3.6V this voltage also works for counterfeit batteries or from a simpler manufacturer? does all Li-Po have a lower self-discharge rate at 3.6V?the resistor just touches the contacts of the BM20 and BP-5L batteries and discharges the battery? Universal charger LED takes a long timeI don't know the best option to charge because I don't have the smartphone and the options are few to charge the Lipo BM20 and BP-5L so I asked for suggestions

author: Gyro
author_rank: Super Contributor
timestamp: June 20, 2021, 06:31:38 pm
content: Quote from: tunk on June 20, 2021, 04:43:54 pmFourthactually fifth, I reported one, which was removed (so maybe more).
How to monitoring amount of solar power sold to power company?  - Page 1
Forum section: electronics / general

author: DougSpindler
author_rank: Super Contributor
timestamp: May 22, 2021, 05:35:21 am
content: I am located in California, my power company is PG&E. Last year due to over production of solar electricity I gave over $1,000 of electricity to the power company for $40. Does anyone know any energy credits monitoring software so I could see where I stand when it becomes true-up time with the power company. What makes this tricky is the rate plan I am on with PG&E is a Time of Use. On weekdays the amount of money PG&E buys excess electricity changes 5 times per day and can rage from $0.14 to $0.58.Anyone know of a software program which works with Time of Use solar customers which will let you know where you stand financially with your power company?

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 23, 2021, 04:51:38 am
content: If it's a fixed schedule or there's a place online to download it, write your own Python script to calculate it.

author: AlbertL
author_rank: Regular Contributor
timestamp: May 23, 2021, 01:41:19 pm
content: What kind of production meter are you using?

author: DougSpindler
author_rank: Super Contributor
timestamp: May 23, 2021, 05:20:38 pm
content: I am using an Enphase IQ Envoy. I don't think data can be exported.I could use Python and have used Excel. The problem is there are no APIs. One has to manually export the data, manually clean-up the data and import. The power company has some API, but it requires a authentication and isn't that easy. Then they change the structure of the data for time to time and then it doesn't work anymore.

author: AlbertL
author_rank: Regular Contributor
timestamp: May 25, 2021, 01:57:02 pm
content: Actually, Enphase does have an API. I played with it a little and was able to access performance data, and later a developer we hired used it in an app for fleet monitoring. Seehttps://developer.enphase.com/.

author: DougSpindler
author_rank: Super Contributor
timestamp: May 25, 2021, 02:17:50 pm
content: Quote from: AlbertL on May 25, 2021, 01:57:02 pmThanks, Didn’t know this is something they offered.

author: Giannaapom
author_rank: Newbie
timestamp: June 18, 2021, 06:36:09 am
content: First of all, congratulations on acquiring a company, especially related to green electricity. What about the charts? You can look at charts of different global companies related to your business. I have a couple of questions about this business. How often do you need to change the solar panels? And how many are enough for your company, for a certain number of customers? I'm just thinking about doing this business too, and I do not know where to start.

author: DougSpindler
author_rank: Super Contributor
timestamp: June 18, 2021, 07:30:41 am
content: The charts are daily production which doesn’t help. In one day the rate can change 5 times. And then there is a summer and winter rate.
EBL 9 Volt 6F22 Li-Ion batteries - Page 1
Forum section: electronics / general

author: bdunham7
author_rank: Super Contributor
timestamp: June 15, 2021, 05:49:40 pm
content: Has anyone seen or used these specific batteries from EBL?http://www.eblmall.com/product/ebl-usb-rechargeable-9v-lithium-batteries-5400mwh-long-lasting-li-ion-batteriesI currently have the other EBL 9V Li-Ion types, the blue 600mA ones that are simply 2 cells in series plus some protection circuitry for 6.6-8.4 volts (which is good for most things because they have low internal resistance) and they require their own charger. The ones I linked have a USB charger and I presume that they use one cell plus a DC-DC converter. This would be great for smoke detectors, but I'm wondering if the output is noisy, which might be a problem in things like DMMs and voltage references.
Problem Li-Po battery - Page 1
Forum section: electronics / general

author: tiago1986
author_rank: Regular Contributor
timestamp: June 11, 2021, 10:11:12 am
content: I have a handheld handheld console but something strange happened to me twice, I kept the device turned off with the xiaomi BM20 battery inserted and both times after a period of non-use (maximum 2 months) when I went to use the device the battery was swollen swollen, what could be happening? if I store the BM20 outside the device it does not swell in the stove but it is very annoying to keep putting and removing the battery from the device

author: tiago1986
author_rank: Regular Contributor
timestamp: June 11, 2021, 10:45:37 am
content: I bought several BM20 batteries on Aliexpress the same from the same seller but they only swell if they are inserted in the device for a long time without use he said they are original and their value is high, they had a voltage of 4.1v

author: tiago1986
author_rank: Regular Contributor
timestamp: June 11, 2021, 10:46:37 am
content: device is handheld Powkiddy Q80

author: Siwastaja
author_rank: Super Contributor
timestamp: June 11, 2021, 10:52:39 am
content: The aliexpress cells are just crap and possibly dangerous. Don't waste your money on them.

author: tiago1986
author_rank: Regular Contributor
timestamp: June 11, 2021, 10:59:05 am
content: Where can I buy the original BM20?the strange thing is that this battery swells only inside the device turned off and not plugged into electrical power

author: tiago1986
author_rank: Regular Contributor
timestamp: June 11, 2021, 12:11:29 pm
content: I do not know the protection circuit of the device is a handheld handheld Powkiddy Q80 console but it was purchased with the battery already installed and it did not swell but the original batteries I bought both bulged inside the console with it turned offI just updated the console firmware

author: tiago1986
author_rank: Regular Contributor
timestamp: June 12, 2021, 10:22:19 am
content: I'm thinking about purchasing an imax B6 mini universal charger to charge/discharge/storage mode some Li-Po mobile phone batteries BM20 and BP-5L models but I don't know which adapter I can buy to make this operation possible, there is an adapter for do that? I think about buying on Aliexpress
P Channel Switch  - Page 1
Forum section: electronics / general

author: thelearner
author_rank: Contributor
timestamp: June 03, 2021, 04:22:19 am
content: Hello,I want to design a circuit that switches between USB & Battery power. If USB is present then the battery should be cut off. If USB is not present then the board should be powered through the battery. I found two designs(attached images). Can anyone tell me which design to use and the pros and cons of the two designs?

author: Peabody
author_rank: Super Contributor
timestamp: June 03, 2021, 03:25:47 pm
content: The circuit in 1.png is typical, and works fine. I can't tell what's going on in 2.png.Edit: The mosfet is oriented correctly in 1.png. It is wrong in 2.png. The issue is the mosfet's body diode, which must block the 5V supply from coming back into the battery. If you add the body diode to the mosfet symbol, you'll see. Here's an example:

author: ocset
author_rank: Super Contributor
timestamp: June 06, 2021, 09:53:48 pm
content: This is nice for youhttps://www.analog.com/media/en/technical-documentation/data-sheets/4412fb.pdf
Opto-isolated offline Flyback feedback loop. - Page 1
Forum section: electronics / general

author: ocset
author_rank: Super Contributor
timestamp: June 06, 2021, 02:14:30 pm
content: Hi,This post concerns offline flyback controllers that output a current from their COMP pin for feedback loop control purposes. The COMP pin gets pulled down by a common emitter connected opto. Now, all small signal feedback loop equations for error amplifiers deal with this situation by assuming a “pullup resistor” connected to the COMP pin pulling up to Vcc of the controller. However, as discussed, many controllers simply have a current source as described, and no actual pullup resistor. However, one still has to derive an “effective pullup resistor “ value for use in the feedback loop equation. How do you do this? Is the following method OK?.....…………..----------------------……………….--------------------The attached is a LTspice simulation of an LT1243 based offline flyback with common emitter opto connection feedback. The error amp in the LT1243 is set up as a ~1mA current source by grounding the FB pin. (the LT1243 is pin-for-pin like the UCC28C43)Also attached is the small signal open loop feedback loop calculation document in excel (for this converter).This shows that the “effective pullup resistor” at the COMP pin of the LT1243 must be ~10k.{this was asserted because setting the pullup resistor to 10k in the excel doc revealed a crossover frequency exactly correspondent to what is shown in the LTspice simulation (attached). The simulation demonstrates the feedback loop crossover frequency by way of its vout deviation following a sudden load transient}.The question is, the “effective pullup resistor” value of 10k is correct….but how is it calculated?As an estimation, I would say that the fact that the error amp is outputting a current, means that in actual fact the “effective pullup resistor” value will vary with the load on the converter? Would you agree that it is pertinent to simply calculate the “effective pullup resistor” value by dividing the voltage at the output of the error amp (ie at the COMP pin) by the current value that it is outputting?…and do this for the case of maximum load?...you then end up with the highest value that the "effective pullup resistor" could be. This is a good value to take because it will give the least phase margin, and so represents a conservative calculation. Would you agree?
PV Clamp Meter - Parasitic Inductance/Power consumption/other effects? - Page 1
Forum section: electronics / general

author: bytemaster0
author_rank: Newbie
timestamp: May 31, 2021, 02:30:11 am
content: Hello all,A quick, but maybe not so quick question. I'm thinking of installing a home energy monitor to go along with my PV setup that's been recently expanded. Almost all of the units out there use clamp-style meters for the PV AC output. I know they're not the most accurate, particularly the split-transformer clamps, but I have a question for which I can't seem to find an answer: There's no such thing as free energy, sowhat effect do the clamp transformer coils have on the power coming from the inverters to the power panel, if there are current clamps on them? Clearly, some energy is being harvested in the form of EMF inducing a voltage in the transformer coil, but this must cause a teeny tiny bit of energy loss from the power lines, no? I realize it may be small, but my engineering mind won't let me rest about it until I put an order of magnitude on it. So, how much do you think it parasitically consumes? Milliwatts? Microwatts? Femtowatts? I realize that the meter itself is powered from mains power, I'm just interested in the potential power loss from an induction coil around the AC wires. Would love to hear anyone's thoughts. Thanks!

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 31, 2021, 03:42:56 am
content: Looking at a 100A sensor I have, it outputs 100mA full scale into a 10 ohm termination resistance. That's 0.1W, while the 100A AC circuit will be 24kW at 240V. Basically it's lost in the noise.

author: bytemaster0
author_rank: Newbie
timestamp: May 31, 2021, 04:20:44 am
content: Excellent real-world response, I think I have my order of magnitude now and can sleep. The meter consumes more power from mains than the clamp ever will in this case. Thank you!
Functional Safety of Electric Vehicles - Active Dischage of HV Capacitors - Page 1
Forum section: electronics / general

author: Hrod_Wolf
author_rank: Newbie
timestamp: May 20, 2021, 05:57:09 pm
content: Hello everyone,As I am discovering the active discharge, I wonder how it works for a DCDC converter. Can someone provide some links or basic litterature for me to understand the principle and some technical litterature to know it in-deph please ?I aim to propose a strong safety strategy (Functional Safety Concept) in order to make sure that:1- The active discharge operates properly2- There is no interaction operating the active discharge while reacting to the DCDC internal failure.Thank you in advance for your responses.

author: f4eru
author_rank: Super Contributor
timestamp: May 20, 2021, 07:08:00 pm
content: There are many, many ways to make your device safe. It all depends on your architecture, objectives and budget....A simple resistor may be enough.

author: PartialDischarge
author_rank: Super Contributor
timestamp: May 20, 2021, 07:47:17 pm
content: I read some standard that recommends for example using resistors in parallel in case one of them fails open.Usually active discharge circuits are commanded by a central control that send and On/off via an isolated dc/dc converter to the discharge circuit ( because usually the dc rails to be discharged are floating and the central control is not)The discharge circuit is usually a string of mosfets of Jfets in cascode to meet the capacitor voltage and resistors are added to limit the current to a predefined level

author: Hrod_Wolf
author_rank: Newbie
timestamp: May 20, 2021, 08:16:57 pm
content: I firstly want to understand the principle of the active discharge and how that works.Secondly I’m interested in all readings you can suggest.Thank you

author: nctnico
author_rank: Super Contributor
timestamp: May 20, 2021, 11:18:06 pm
content: Also don't forget to have some kind of indicator to show there still are lethal voltages present. It has been a while but I vaguely recall LEDs and neon lamps being used in some of the high power supplies I have worked on a long time ago.

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 21, 2021, 01:39:36 am
content: Quote from: nctnico on May 20, 2021, 11:18:06 pmBlue LEDs work great for that, takes very little current to get a visible glow. One fail safe configuration would be to have two in series (at high voltage, if a LED fails open, it probably will change to failing shorted) then with a properly rated resistor or string of resistors to the voltage rail. Add a second one of those resistor/LED strings for redundancy.
battery build using repackr wierdness - Page 1
Forum section: electronics / general

author: m3vuv
author_rank: Super Contributor
timestamp: May 12, 2021, 04:04:52 pm
content: im trying to build a 13s pack 48v,im trying to use repackr to sort the cells,where it asks for the number of cells in series i say 13,when it gives me the results it only lists the total voltage as 38 and only lists 8 groups of cells,whats going on here?,any ideas?,cheers in advance.
new lithium ion 18650 battery build - Page 1
Forum section: electronics / general

author: m3vuv
author_rank: Super Contributor
timestamp: May 08, 2021, 09:02:36 am
content: I am planning on a new 18650 triangle battery build using samsung 15q 18650 cells ,its going to be a 13s 8p,i see repakir to match the cells capacity but no mention of the cells internal resistance,im testing all the cells using a litokala engineer lii-500,some of the cells read 30 milliohm ir and some 125,how should i arrange them regarding internal resistance to keep them ballanced,i have a bt smart bms but want to do the best i can to match them for ballance,cheers in advance.

author: m3vuv
author_rank: Super Contributor
timestamp: May 10, 2021, 08:57:43 pm
content: can no one shed any light on this??

author: tunk
author_rank: Super Contributor
timestamp: May 10, 2021, 10:05:14 pm
content: Not sure if a charger is a precision instrument, so the internal resistancemeasurements may not be very accurate. Have you tried to measure it severaltimes for the same cell (taking it out for each time and then reinserting it)?You may also want to check the self discharge.

author: uer166
author_rank: Super Contributor
timestamp: May 10, 2021, 11:27:13 pm
content: Quote from: m3vuv on May 08, 2021, 09:02:36 amOnly use new cells for a new pack. That is a huge range of internal resistance, new cells shouldn't have that.

author: m3vuv
author_rank: Super Contributor
timestamp: May 10, 2021, 11:33:13 pm
content: is the ir very important?
Ancient BenchMarq "Fuel Gauge" Chip BQ2913 - Page 1
Forum section: electronics / general

author: tomoliva
author_rank: Newbie
timestamp: May 10, 2021, 11:01:27 am
content: Been knocking myself out scouring the usual places for a data sheet - guessing it's a product that TI killed off when they took over...Item I'm peering at is in a Giant LaFree ebike NiMH 20 cell Panasonic battery pack - the battery is working OK but range anxious user wants a working fuel gauge ...Anybody have a spec sheet / done a 20S NiMH monitor?

author: Renate
author_rank: Super Contributor
timestamp: May 10, 2021, 01:38:38 pm
content: Dunno.I just ordered some BQ76920-03 (3-5 cell) for a future 4 x LiFePO4 setup.The BQ76940 goes to 15 cells.https://www.ti.com/lit/gpn/bq76920(includes 40)

author: tomoliva
author_rank: Newbie
timestamp: May 10, 2021, 04:59:37 pm
content: I'm guessing that it might be in a Benchmarq Data Book - Benchmarq went through the hoops - bought by Unitrode in 1998 iirc - which itself got swallowed by TI about a year later ...There are hints that a data book was published around '98 but I guess there was a bunch of pruning (and maybe part renumbering) happened.... Found an older databook on archive.org.... and this - just to torment the hunter>https://www.wirelessdesignonline.com/doc/1998-data-book-0001Ho-hum...off to search "gas gauge ICs" ( or maybe an Arduino nano and a few LEDs will wake up fast enough when powered up... - give him a pot to twiddle to adjust the scale to personal taste.... )
Current Sensing MOSFET's - Page 1
Forum section: electronics / general

author: tgferreira184
author_rank: Newbie
timestamp: April 27, 2021, 03:47:28 pm
content: Hello everyone!I came across this application note:https://www.onsemi.com/pub/Collateral/AND8093-D.PDFtalking about Current Sensing MOSFET's. Essentially they are two in one FET's, with one of them much smaller than the other, providing a fixed small percentage of the total current in a sense pin (something in the order of 1:1000th). This means one only has to measure this small current and multiply it by a factor in order to measure the total FET's current, with far fewer losses than the usual inline shunt approach.However, after researching many of the more famous manufacturers i came up short, only finding the IXYS MMIX1T132N50P3(Application note here:https://www.ixys.com/Documents/Appnotes/High_Current_Power_MOSFET_with_Current_Mirror_and_Temperature_Sense_Diodes.pdf),which is a high voltage, relatively low current device, while I need higher current capability at about 50V, and the HEXSense series from International Rectifier, which seems to be long obsolete.To make matters worse, there doesn't seem to be a parametric search that sifts these types of MOSFET, so I wondered if anyone here would know any more of these devices, or to tell me why they are a bad idea.Best regards, Tiago

author: David Hess
author_rank: Super Contributor
timestamp: April 29, 2021, 09:37:44 pm
content: I did a search for them last week and came to the same conclusions; their availability is poor and trying to select for them is useless. I limited my search to 4 pin packages and even that was not enough to find them.

author: tgferreira184
author_rank: Newbie
timestamp: May 06, 2021, 01:05:42 pm
content: After contacting ON Semiconductor I was told they no longer sell any SenseFET, so I guess it's end of the line for it.
Thermistor for NiCd battery pack. - Page 1
Forum section: electronics / general

author: paul8f
author_rank: Regular Contributor
timestamp: May 03, 2021, 10:20:24 am
content: Hi all,just figured out why this cheap old branch-cutter is failing to charge. The thermal sensor is reading in the krange.The (8s) NiCd pack will accept a charge when this is bypassed. I'm guessing it's an NTC thermistor???Any ideas what type it is, and where I could pick up a replacement? Code starts withJJI think.(specs & photos attached).Paul.

author: beanflying
author_rank: Super Contributor
timestamp: May 03, 2021, 11:11:02 am
content: Depending on how it is wired it will be a NO or NC one of theseeBay auction: #132678371472go with 60C will be safe but allow a good charge rate or even just drop it out of the circuit by opening or bridging as needed.They were always just a belts and braces with Nicads and all my R/C packs would never have anything like it used or fitted.

author: mikerj
author_rank: Super Contributor
timestamp: May 04, 2021, 08:15:43 am
content: The JJD-45 thermal switch opens at a nominal 45C.

author: beanflying
author_rank: Super Contributor
timestamp: May 04, 2021, 08:45:35 am
content: Quote from: mikerj on May 04, 2021, 08:15:43 am45C would be a likely fail in an Aussie Summer for charging, should be OK for an Irish heatwave

author: paul8f
author_rank: Regular Contributor
timestamp: May 04, 2021, 07:45:53 pm
content: Quote from: mikerj on May 04, 2021, 08:15:43 amThat looks about right. Thanks for the post!

author: paul8f
author_rank: Regular Contributor
timestamp: May 04, 2021, 07:49:32 pm
content: Quote from: beanflying on May 04, 2021, 08:45:35 amYeah, the best Irish summer will never even come close to a bad summer in Oz!Thanks for the help.
[Beginner] Where to connect the AC converter, on load or directly on battery ? - Page 1
Forum section: electronics / general

author: DC1MC
author_rank: Super Contributor
timestamp: April 30, 2021, 05:08:47 pm
content: Hello everybody,as I didn't get any answer on my previous question, I've decided to start with a Victron MPPT 75/15 and two (used) Silicio SE-230 (see attached pic) @50EUR a piece.I have seen different opinions about connecting the 220 V AC inverter, either on Load output of the charger, or direct in parallel with the battery, I would really appreciate an explanation and recommendation of where is the best to connect it get the most power for some garden tools.Also any recommendation of a good battery and a ca. 2000W inverter available in Germany will be appreciated.Many thanks,DC1MC

author: bob91343
author_rank: Super Contributor
timestamp: April 30, 2021, 11:28:58 pm
content: The charger puts out a higher voltage than the battery alone. So the decision can be based on reliability (use the battery) or available power (use the charger).
Please help me to estimate power losses - Page 1
Forum section: electronics / general

author: m.jayid
author_rank: Newbie
timestamp: April 27, 2021, 10:19:45 pm
content: Hi everybody.💐I am a beginner in this field.And I would like to estimate analytically the losses of a three level T type inverter (please see the attachment).Is there any formula for estimating conduction , and switching losses.To design an appropriate heat sink based on that ?Thank you very much.💐💐💐

author: bob91343
author_rank: Super Contributor
timestamp: April 27, 2021, 10:45:59 pm
content: No formula, really. The conductive losses can be estimated by Ohm's law, the ON resistance times the current. The switching losses depend on layout. During the switching time, the transient voltage and current in each part multiplied by the duration, divided by the frequency.Long leads make switching time longer and voltages spike.
Tesla Solar raises prices....$100K+ solar anyone? - Page 1
Forum section: electronics / general

author: bdunham7
author_rank: Super Contributor
timestamp: April 28, 2021, 04:33:52 am
content: https://www.businessinsider.com/elon-musk-tesla-solar-roof-price-mistakes-calculating-cost-2021-4

author: james_s
author_rank: Super Contributor
timestamp: April 28, 2021, 04:52:57 am
content: "Some roofs are literally two times or three times easier than other roofs. So you just can't have a one-size-fits-all situation," he said."This really ought to be obvious, and they could have learned this by talking to a professional roofer, or a general contractor.They made the same mistake with the self driving autopilot project, they assumed it was easy and were overconfident, neglecting to consider that some driving situations are vastly easier than others, and a self driving car without a human driver able to take over that works in 95% of situations is virtually useless.
Current shunt output smoothing - Page 1
Forum section: electronics / general

author: Robert Smith Eco Warrior
author_rank: Regular Contributor
timestamp: April 19, 2021, 08:15:54 am
content: Hi All,I am just doing a bit of temporary wiring in my battery shed to put a 100A/100mV current shunt between my charge controller and batteries. I still have my additional winter solar panels laid out on the ground and I shall soon put them away for the summer. I just wanted to pop the shunt in so I can see what current I am getting from the panels.I am making up a circuit for monitoring but just want to measure the shunt output with my Fluke 77 mk II (I think) multimeter.I am wondering if the PWM switching of the charge controller will give nonsense readings on the multimeter and can I filter the shunt output with a capacitor of some value?

author: Gyro
author_rank: Super Contributor
timestamp: April 19, 2021, 08:43:26 am
content: Good luck with finding a capacitor that will directly smooth a 1msource impedance. You could use an RC filter though, placing a higher value series resistor between the shunt and the capacitor. for instance 1k resistor and 100uF capacitor would give you a -3db frequency of about 1.5Hz.

author: Robert Smith Eco Warrior
author_rank: Regular Contributor
timestamp: April 19, 2021, 12:03:14 pm
content: Ah, yes, I see what you mean.I shall try those values you suggested.I am waiting for Covid lockdown rules to allow me to go and collect an ocilloscope I have bought. Then I might have a chance of seeing what is going on.

author: Gyro
author_rank: Super Contributor
timestamp: April 19, 2021, 01:21:24 pm
content: Those are hopefully worst case values. If possible try to stay down to 10uF or lower as you could do that with a film capacitor, preventing potential leakage current issues with an electrolytic cap (or use a Tantalum bead). The limiting factor on the series resistor is inaccuracy caused by the input resistance of the DMM, normally 10Meg. I am probably being a bit over cautious there too, a 10k resistor would still only affect the reading by 0.1%, your shunt is almost certainly less accurate than that anyway.

author: Robert Smith Eco Warrior
author_rank: Regular Contributor
timestamp: April 22, 2021, 06:57:18 pm
content: Thanks for that.I have a few threads going and I missed your reply for a while.

author: David Hess
author_rank: Super Contributor
timestamp: April 23, 2021, 10:03:20 am
content: The charge controller should have decoupling on its input and the multimeter should not care anyway.