hybridfree/eevblog-posts huggingface dataset:
How can I calculate how much potential I can get from a lipo cell? - Page 1
Forum section: electronics / beginners

author: NaDobraNich
author_rank: Regular Contributor
timestamp: March 09, 2023, 08:44:25 pm
content: I have a sensor that gets dropped into a hole. It's size contained. I might be able to recover it, but might not, so I need pretty cheap costs.I plan on feeding it with a lipo cell, but I need a lot more than the 3.7V of a fresh cell and momentarily, I need .5W spikes of power for short amounts of time. So I need a boost circuit to get the voltage up, but then I get a little lost.I think on a LiPo cell, that those typically "short" pretty well. That if I have a 3.7V 100mAh cell, that I "could" get 48V and 10mA from that, but it would be the ESR that is the main limiter.Then the boost circuit's response and efficiency.Then that the battery will quickly drop from 3.7V.Am I missing anything? It seems like it's fairly straight forward things, but there has to be some extra difficulty. For example, what are the chances I could get .5W instantly from some China 3.7V? If I want to figure this out for a specific battery will I need an ESR meter?

author: shapirus
author_rank: Super Contributor
timestamp: March 09, 2023, 08:50:11 pm
content: Any respectable rechargeable lithium cell's datasheet specifies maximum continuous discharge current and maximum peak current for a given pulse duration. When you know these and your boost circuit's efficiency, you can calculate whether the cell will be able to output what you want.Start with checking the datasheets of some cells that fit in your size constraints.p.s. boosting 3-4V to 48V isn't going to be an easy job.

author: NaDobraNich
author_rank: Regular Contributor
timestamp: March 09, 2023, 09:16:23 pm
content: I'll get right on asking suppliers on AliExpress for proper datasheetsYea, I don't really need 48V specifically. And I do need it quickly when I need it. It was just an example, I'd probably be fine with the requirements at 24V. So I'll start there. I haven't made a boost circuit yet, what is the limiting factor for gain? Inductor/capacitor size quality?

author: james_s
author_rank: Super Contributor
timestamp: March 09, 2023, 11:26:19 pm
content: It's fairly easy to boost 12V to 170V for nixie tubes so it shouldn't be too hard to boost 3.7V to 48V. Disposable camera flash circuits get around 200V from a single 1.5V AA cell. Fancier xenon camera flashes get more than that from usually 4 AA cells. It's not trivial but it's not super hard either.
how can I calculate input impedance?? (In learning AOE) - Page 1
Forum section: electronics / beginners

author: JunHyeob LEE
author_rank: Newbie
timestamp: March 14, 2019, 01:45:00 am
content: Hi, I start to study electronics. And I'm a beginner.In Learning AOE, I have questions.I know Rout is ((4k ll 4k) + 2k) ll 10k = 5.45kbut I don't know how to calculate Rin.

author: Wimberleytech
author_rank: Super Contributor
timestamp: March 14, 2019, 02:14:49 am
content: Rout = ((4k || 4k) + 10k) || 10k = 5.455kNow for RinYou must assume that the junction of the two 25k resistors is open circuit (no additional load)Using the same methodology as was done for RoutRin = ((25k + 25k) || 10k) + 10k = 18.33k

author: JunHyeob LEE
author_rank: Newbie
timestamp: March 14, 2019, 03:23:28 pm
content: Thanks a lot!

author: bson
author_rank: Unknown
timestamp: March 15, 2019, 12:35:06 am
content: WimberleyTech didn't explicitly state it, but input and output impedances (often called Z11 and Z22) are always measured open circuit. Output impedance with the input open, input impedance with the output open. Even with things like antennas the same model is used, although there is no "output" per se, the input is measured as if there is an open output. Admittances (Y11, Y22) are measured with the opposite endshorted.This means C has an input impedance. Then B+C has an input impedance, but to measure B alone you'd need to disconnect C from it. Same with A+B+C. On the output side, A has an output impedance measured with the input open as drawn and B disconnected. The A+B, with C disconnected, and finally A+B+C has a joint output impedance.Hope this helps understand in/out impedances.

author: JunHyeob LEE
author_rank: Newbie
timestamp: March 15, 2019, 01:24:40 am
content: Thank you for your detail explanation.

author: Wimberleytech
author_rank: Super Contributor
timestamp: March 15, 2019, 01:45:08 am
content: Quote from: bson on March 15, 2019, 12:35:06 amI do not disagree regarding two-port analysis. However, for this problem, even with the limited insight into the context of the original question, I still believe that you treat Vin as a short circuit for Rout analysis.
How can I calculate mosfet heat dissappation? - Page 1
Forum section: electronics / beginners

author: alank2
author_rank: Super Contributor
timestamp: August 31, 2014, 02:00:36 am
content: Hi Everyone,I'm feeding it a 8kHz PWM signal and it is switching a 40mA load (which I realize is very little for a mosfet).It is a IRLD024PBF-ND.Thanks,Alan

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 31, 2014, 02:42:52 am
content: Circuit?

author: Pedram
author_rank: Regular Contributor
timestamp: August 31, 2014, 03:49:13 am
content: it depends on RDS(on) , gate voltage , frequency , driver's output impedance and gate capacitanceaccording to datasheet, RDS(on) is 0.1ohms on 5V DC Gate voltage. at 50ma it dissipate less than 250uW

author: DanielS
author_rank: Frequent Contributor
timestamp: August 31, 2014, 12:03:35 pm
content: The fundamental way of calculating dissipation in any component is: sum of integral of i(t)v(t) on all pins averaged over a number of complete operating cycles.A simplified ballpark figure if the rise/fall curves are roughly linear: ((trise+ tfall)*IDSrise+fall average*VDSoff/2 + ton* RDSon* Ids^2) / period.The exact rise/fall waveforms can vary considerably depending on circuit design and operating region. If the MOSFET drives an inductor operating in continuous mode at 10A average current and has a 500ns rise/fall time, 30V input voltage and 0.02 RDSon, you lose about 15W from rise/fall and 1W from ON-time.
How can I calculate the maximum switching frequency of a diode? - Page 1
Forum section: electronics / beginners

author: tastychickenwings69
author_rank: Newbie
timestamp: March 18, 2022, 08:22:02 am
content: Hi.I have a RFN10NS8D super fast recovery diode and wanna calculate the maximum working frequency.I was planning on using it for some HF AC rectification tests.The trr reverse recovery time is 40ns.datasheet:https://fscdn.rohm.com/en/products/databook/datasheet/discrete/diode/fast_recovery/rfn10ns8d.pdfHelp would be nice.

author: Ian.M
author_rank: Super Contributor
timestamp: March 18, 2022, 09:28:46 am
content: You cant. All the datasheet gives you is typ. and max. Reverse Recovery Times (Trr) for the reverse current to drop to 25% of its initial peak. You have to decide what proportion of the reverse half-cycle you can tolerate it conducting for without excessive losses, and, allowing for any asymmetry in the waveform, decide what *YOU* regard as its frequency limit in *YOUR* application.
How can i connect 9" TFT with general TFT board used for a 7" TFT - Page 1
Forum section: electronics / beginners

author: sairfan1
author_rank: Frequent Contributor
timestamp: January 02, 2025, 10:13:22 pm
content: I bought a 7" TFT with driver board from aliexpress, later i found a 9" TFT taken out from a car media player and I was looking for a genaric TFT driving board to use.One I bought from Aliexpress 7" TFT has 50 connection pins but 9" TFT has just 26 pin connections, I do not understand types of TFT and connectors and I was looking for help if its possible that i can use 9" TFT as well.Picture of both connecting strips and board is attached.

author: prints-f-darkness
author_rank: Contributor
timestamp: January 03, 2025, 01:34:20 am
content: Hi,A TFT LCD display can have one a few types of interfaces, see the link below,https://www.hongguangdisplay.com/blog/common-types-of-tft-lcd-interface/"I" don't think there is a standard pin out for any of the interfaces, its whatever the manufacturer decides. That being said, the only way to find a driver board for your display would be with the correct pinout of the display, and driver board.Bare in mind, the likely hood of finding a driver board for a salvaged display is very low, especially without a datasheet. Impossible? no, highly unlikely, yes.Does the display have any markings to indicate a manufacture, or part number?

author: Psi
author_rank: Super Contributor
timestamp: January 03, 2025, 01:38:55 am
content: It's a bit of a mess, even if the connector is correct and the pinout is correct the controller still has to be told/programmed with what display it's connected too a lot of the time. I think there are some standards but there's also a lot of random stuff.There used to be some generic driver boards available on aliexpress that came with USB and an App that you could use to reprogram the drive board to work with all sorts of panels, I dunno if you can still get it

author: coromonadalix
author_rank: Super Contributor
timestamp: January 03, 2025, 02:11:17 am
content: yes it is not easy at it would seem, the controller ic need resolution, frequencies, mapping etc ....search here for a thread about theses ic's you can find on the web tools to do that and reconfigure if needed

author: amyk
author_rank: Super Contributor
timestamp: January 03, 2025, 08:50:57 am
content: As the silkscreen on the driver board PCB indicates, and just based on the number of pins, that 7" TFT uses a TTL interface.The 26-pin one, if pins 10 and 11 are joined together, is likely to be an analog RGB panel with this pinout:https://preview.redd.it/6wcc6tlzeif91.png?width=634&format=png&auto=webp&s=6fc4f62f26399e68074d7ffac0ab40acda5f1d16I have written about these before here:https://www.eevblog.com/forum/beginners/salvaged-7_-tft-display-but-how-to-interface-with-it/msg940613/#msg940613https://www.eevblog.com/forum/projects/re-purposing-a-photo-frame-looking-to-identify-the-lcd/msg704798/#msg704798
how can i control the power of modules connected to esp32? - Page 1
Forum section: electronics / beginners

author: Rishles69@
author_rank: Regular Contributor
timestamp: March 21, 2024, 10:41:23 am
content: so i recently started a wearable project where there are like 7-8 modules in it. I don't need these modules working together and i only need to use 3-4 modules at a time to save power (battery has only 500mah) and switch off the other modules which are not in use. The modules i use are:- ESP32C3 xiao, 2x MCP23017-E/SO MICROCHIP I/O Expander, 16 bit (to increase more pins and control 17 leds and 4 touch switches), SSD1327 oled, bmp180 sensor, max30102, mpu6050, hmc5883l, sd card module, vibration motor module, ATGM336h gps module. Im thinking of using a transistor or mosfet butwhat and which transistor should i use?andwhat is the program for it when i control i through the i/o expander?

author: aliarifat794
author_rank: Regular Contributor
timestamp: March 23, 2024, 10:27:28 am
content: For your application, MOSFETs might be more suitable due to their lower power consumption.
How can i design a battery from laptop's battery - Page 1
Forum section: electronics / beginners

author: shahsali
author_rank: Newbie
timestamp: December 10, 2013, 04:00:35 am
content: I have several unused HP laptop batteries and i want to design a bigger battery and charging circuit by taking all cells out of the laptop battery. is this possible?

author: BravoV
author_rank: Super Contributor
timestamp: December 10, 2013, 04:28:34 am
content: Quote from: shahsali on December 10, 2013, 04:00:35 amPossible ? YesSafe ? Probably not, especially looking at the way you ask the question that I guess it shows your knowledge level on these topic. A fire extinguisher standing by near vicinity when you play with it is highly recommended.

author: Stonent
author_rank: Super Contributor
timestamp: December 10, 2013, 04:45:51 am
content: Rechargeable batteries based on Lithium can catch fire or explode if not properly charged which is why laptop batteries and cell phone batteries have more than 2 pins on them. There is almost always a pin that relays charging information back to the circuit so that the batteries are not charged incorrectly. If you remove the cells from the battery you are bypassing the safe charging circuit design and can potentially have a dangerous situation.

author: amyk
author_rank: Super Contributor
timestamp: December 10, 2013, 12:04:31 pm
content: AFAIK there's a pretty sizeable number of the population using unprotected 18650s in torches, with an extremely low incidence of fires and the like, but still, use common sense and don't push the cells beyond their specs.

author: Neilm
author_rank: Super Contributor
timestamp: December 10, 2013, 06:49:50 pm
content: I don't know about HP batteries but I know there are some configurations of battery protection and charger circuits that allow the host (laptop) to interrogate the pack. If the host does not like what it sees it will not switch on the battery power FET.

author: staxquad
author_rank: Frequent Contributor
timestamp: December 10, 2013, 09:20:42 pm
content: Quote from: shahsali on December 10, 2013, 04:00:35 amI took apart a Dell laptop battery pack for the cells. You just have to make sure you don't short any of the cells or circuitry while you're dissecting them. Better to do that outside to be on the safe side.

author: kripton2035
author_rank: Super Contributor
timestamp: December 10, 2013, 09:27:38 pm
content: you need a fire extinguisher specialized for li-ion batteries, that is with carbonic snow inside, beside the area of workor do it outside...

author: shahsali
author_rank: Newbie
timestamp: December 13, 2013, 12:55:44 am
content: thx for all replies. I am planning to take batteries apart n use cells. any good reference for designing charging circuitry for these cells?
How can I detect if two magnets are coupled? - Page 1
Forum section: electronics / beginners

author: GeriX
author_rank: Newbie
timestamp: January 26, 2024, 02:38:24 pm
content: Hello everyone!I´m trying to build a sensor, that are mounted close to an array of neodymium square magnets. It is supposed to detect the polarity of the closest magnet (wich works fine with my Hall Sensor 49E) and whether there is another second magnet coupled to it (behind it).As of my understanding, the detectable field should extend in axial direction, when two magnets are coupled together. However I am unable to observe a change in the detected values, whether I only apply one or two magnets.Can you suggest another sensor or signal processing strategy, or is just my physics understanding wrong?See the attached fotos for understanding of the configuration.Thank you!

author: MasterT
author_rank: Frequent Contributor
timestamp: January 26, 2024, 03:10:33 pm
content: Board you have, likely build with comparator - trim pot to adjust threshould. Post circuits or link to data sheet, in short you need linear amplifier or if magnets close enough DMM 'd be sufficient

author: GeriX
author_rank: Newbie
timestamp: January 26, 2024, 04:57:05 pm
content: Ok, I desoldered the Sensor from the PCB and can now detect a very slight difference when coupled, so this and a linear amp is a good solution, thanks!PS: What is a DMM?

author: MasterT
author_rank: Frequent Contributor
timestamp: January 26, 2024, 05:00:23 pm
content: Digital Multimeter (DMM).
How can I do my own DIY 1s LiPo charged? - Page 1
Forum section: electronics / beginners

author: XxMandragoraxX
author_rank: Contributor
timestamp: January 24, 2025, 07:23:05 am
content: Guys, I bought a 1s battery charger for my tinywhoop dronethe question is that I would like to know if I could make one myself. I have seen on ALI that they sell very simple circuits to act as a BMS. Is it possible that with a 4S at 2 A charger you can charge 4 batteries simultaneously, occupying each battery as if each independent battery were a cell in a 4s pack?this is the circuit I talked about

author: inse
author_rank: Super Contributor
timestamp: January 24, 2025, 07:45:42 am
content: In principle you could wire up four single batteries in series and charge it with this thing.But I would never do that as the batteries may have different capacity or charge state and this crappy circuit doesn‘t monitor individual cells.I doubt it’s more than a current limited voltage source.

author: thm_w
author_rank: Super Contributor
timestamp: January 25, 2025, 12:23:54 am
content: Just get multiple 1S USB charger modules if you want to charge multiple batteries at once.Using a 2, 3, 4S charger like you show doesn't make sense to do.

author: XxMandragoraxX
author_rank: Contributor
timestamp: January 27, 2025, 07:10:20 am
content: But doing this, te current get down so hard because each baterry is 550mAh. I mean if I use this litio charger for charge 1s LiPo batteries, How I should wire this?Because I think that if you have a BSM with 4A and I connect the batteries in parallel, the current has to go down, right?since the current would be distributed among all the batteries that were connected

author: kjr18
author_rank: Regular Contributor
timestamp: January 27, 2025, 08:49:02 am
content: Easiest and cheapest way is to use 4 TP4056 modules, and wire every battery separately. Connecting them in series is possible, but then you need to power each module with separated power supply, their grounds isolated. Not an easy as sounds. You can get small dc/dc modules like B0505S, but that's not really efficient and useful.As for connecting them in parallel, they also should be at similar discharge level, because if one of them is a bit off, other cells might get overcharged a bit, and that one not, and this difference will get bigger with every discharge-charge cycle, until something breaks.If you really want to charge them all at the same time, connected in series then you need a charger that monitors voltage of every cell and correct it if needed, something like hobby chargers.

author: XxMandragoraxX
author_rank: Contributor
timestamp: January 27, 2025, 11:41:56 am
content: Thanks so much. Ill get one of that, a little bit more expensive but more safe.

author: kjr18
author_rank: Regular Contributor
timestamp: January 29, 2025, 11:07:00 am
content: You don't really need to buy a new one. That one you showed in first picture should work just fine.
How can I drive this LED matrix? - Page 1
Forum section: electronics / beginners

author: jammo
author_rank: Newbie
timestamp: August 08, 2018, 03:45:28 pm
content: I've got a Maplin (RIP) LED matrix display. Unfortunately, the ROM chip has died on the controller board. But I have no reason to believe that the LEDs don't work.Is there any way of controlling this matrix without the original controller board? Pictures below.Matrix frontMatrix backController frontController backMatrix closeupThanks!

author: Pirateguy
author_rank: Regular Contributor
timestamp: August 13, 2018, 01:18:49 am
content: well those ICs on the front are the drivers, looks like all this needs is a microcontroller to tell it what to do,check the numbers on those chips and google up their data sheets, and also do a google on the part number + arduino(odds are somebody wrote a library or tutorial for it)

author: Ian.M
author_rank: Super Contributor
timestamp: August 13, 2018, 02:16:23 am
content: Not quite - the column drivers + a 60 bit shift register to control them are on the display board, but the row drivers are on the controller. If you want to drive the display board off something like an Arduino, you'll need seven power P-MOSFETs to replace them either low Vgs threshold ones if it runs the matrix from 5V or ordinary ones with gate drivers to handle the level shifting if it runs from a higher voltage.What happened to the ROM? If you don't need to add features the original didn't support, it might be easier to find someone who's got one and can copy it.

author: Eka
author_rank: Regular Contributor
timestamp: August 13, 2018, 03:03:11 am
content: Quote from: Ian.M on August 13, 2018, 02:16:23 amI second all of this.The column drivers are the ones next to the resistors. The shift register are the other chips. Simple enough to drive. The chip that drives the rows is the STA402A on the driver board which leads me to:https://www.digikey.com/product-detail/en/sanken/STA402A/STA402A-ND/4289345It is buffered from the MCU by U10 and U11?, whatever they are. The controller board may be designed to run two of the arrays, but this one may be paralleling the STA402A PNP Darlington driver chips to drive the one long array. I'd need to see the cables better.

author: Ian.M
author_rank: Super Contributor
timestamp: August 13, 2018, 04:01:06 am
content: There's also likely to be an issue with the row multiplexing - if it stops, the continuous LED current is probably high enough to burn out LEDs that are on in the row that its stuck on. This isn't a problem once you have 100% tested stable firmware, but during development unless you are very good and very lucky, to avoid letting the magic smoke out you either need to reduce the LED supply voltage to reduce the max continuous current through them, or patch in a circuit to monitor the duty cycles of the seven row drive lines and if any stay over 15% for long, disable the display.
How can I find 5 letters marked IC with 8 pin IAFEF ? - Page 1
Forum section: electronics / beginners

author: diegooo1972
author_rank: Newbie
timestamp: September 10, 2020, 12:36:04 pm
content: Hi AllAs topic i'm not able to find the datasheet of an IC 8pin marked IAFEF.I see a lot of chip marked with 5 letters but I don't know how to read them.Sorry for the silly question and thx anyway.

author: Jwillis
author_rank: Super Contributor
timestamp: September 10, 2020, 08:24:43 pm
content: Don't know if this helps but the Markings IAFEF point to a SOT23-8 switching regulator .https://www.aliexpress.com/item/32900819085.htmland the closest manufacturer with Top marks like that is Monolithic Power Systems . For examplehttps://www.monolithicpower.com/en/documentview/productdocument/index/version/2/document_type/Datasheet/lang/en/sku/MPQ2143-AEC1/page 15. JEDEC REFERENCE IS MO-193, VARIATION BA .

author: Microcheap
author_rank: Frequent Contributor
timestamp: September 11, 2020, 04:33:48 am
content: I normally use this site when I need to look for a smd reference marking:http://www.smdmark.com/en-US/search/code?id=IAFI've searched using only "IAF" and got some results. The MP2159GJ step-down converter seems to fit your description.https://www.monolithicpower.com/en/mp2159.html

author: diegooo1972
author_rank: Newbie
timestamp: September 11, 2020, 05:43:26 pm
content: I already tried mp2159 but it seems to have different pin configuration or i have another shorted components that I can't find anywhere. Atm I ordered IAFEF from aliexpress. But thx so much for this site to recognize SMD. I'll check for MPQ2143-AEC1. Thank so much for this answers. Really appreciate.
How can I find my posts? - Page 1
Forum section: electronics / beginners

author: hummusdude
author_rank: Regular Contributor
timestamp: October 09, 2021, 05:30:13 am
content: This is such a noob question...but I can't find any link in the forum that takes me to my posts. Also, does the forum save drafts? At times when I've tried to post a new thread it just disappears altogether when I hit the "Post" button.

author: bdunham7
author_rank: Super Contributor
timestamp: October 09, 2021, 05:35:12 am
content: From the home page, select 'Profile', then under your avatar select 'Posts'.

author: PerranOak
author_rank: Frequent Contributor
timestamp: October 09, 2021, 04:00:45 pm
content: Yeah, I wish there was a more convenient (one click) way of doing that.

author: oPossum
author_rank: Super Contributor
timestamp: October 09, 2021, 05:09:30 pm
content: Quote from: PerranOak on October 09, 2021, 04:00:45 pmBookmark this link:https://www.eevblog.com/forum/profile/?area=showposts;u=116305

author: Terry Bites
author_rank: Super Contributor
timestamp: October 03, 2022, 12:14:27 pm
content: Er no, nothing shown on that page.So anoying not to just have a button on the home page.In fact- preposterous!

author: mikerj
author_rank: Super Contributor
timestamp: October 03, 2022, 12:51:58 pm
content: Quote from: Terry Bites on October 03, 2022, 12:14:27 pmThe link is personal to a specific account, the link above is for PerranOak's account. Yours would behttps://www.eevblog.com/forum/profile/?area=showposts;u=689532
How can i get Display Port out from this mobile MIPI-DSI output using sn65dsi86? - Page 1
Forum section: electronics / beginners

author: electricenthusiast
author_rank: Contributor
timestamp: December 18, 2022, 02:31:38 am
content: How can get DisplayPort/Edp output from this Mobile mipi-dsi display input from this schematic using SN65DSI86 ic?See 1.jpgThere are some SN65DSI86 ic reference schematics but i dont know how to do it and does it work?. Can somebody help me?. If someone can do it pls send me a schematic? Thanks.You can look up these schematics for any help (note: my dsi source is a single channel with 4 data lanes and 1 clock lane).See 2.jpg and 3.pngI am sure it works and i dont want to throw my phone away
How can I get error(angle) of between two quaternions ? - Page 1
Forum section: electronics / beginners

author: ammjy
author_rank: Regular Contributor
timestamp: January 20, 2020, 09:25:13 pm
content: Hello, EEVblog users,always thanks you for your time.in Euler angles case,first, If desired Euler angles are 5, 5, 5 (in order xyz).and If state of Euler angles are 4, 4, 4.than, the "error" will be 1, 1, 1 simply. (it is error, so it is not meaning attitude)but, in Quaternion case,Quaternion has exteneded complex number system with 4 components w + xi + yj + zk,therefore, it can not be calculated simply like a Euler angles.and rule of subtract of between two quaternion is as follows.difference = quaternion1 * inverse(quaternion2)( here, suppose, two quaternions has difference as much Euler angle 1 degree.)but, when I convert "difference" to Euler angle after calculate, result is not 1 degree.Could you give some advice for me ? maybe I am thinking wrong about it.Please, let me know.
How can I keep a GPIO pin high momentarily during boot? - Page 1
Forum section: electronics / beginners

author: tcz
author_rank: Contributor
timestamp: December 14, 2021, 07:51:49 pm
content: Hello, people of eevblog!I am working on my Xmas light setup. I'm almost ready to impress the kidsthe only thing holding me back is that stubborn GPIO2 pinthat needs to be high for a short time on power up (having the pin low boots in programming mode).The firmware I'm running (EspixelStick) uses the pin to send DATA to the LED strip, and from what the author says, changing the pin is not an option (UART is on it).My other builds using a NodeMCU and a Wemos Mini D1 instead of the ESP-01s have no problem booting with the DATA line connected. I should add there's a 470ohm resistance connected in line between GPIO2 and the data line.So what's the secret?I know these boards have extra components, I'm just not sure which ones keep the pin high.I got the ESP-01s to keep the cost down, so If there's a simple way to do this with passive components (even if it's hacky), it would be ideal.Also, if it's of any use, I am using an AMS1117 based regulator module to power the ESP.Thank you!

author: ve7xen
author_rank: Super Contributor
timestamp: December 14, 2021, 08:09:02 pm
content: It's probably sufficient in this case to use a weak pull-up resistor (say 100k) to Vcc on the microcontroller side of the 470R. This will give it a defined state when nothing is driving it, but is easily weak enough to be overridden by the microcontroller once the code boots and the pin is set as output.

author: tcz
author_rank: Contributor
timestamp: December 16, 2021, 07:58:54 am
content: Wow, re-reading myself now, that previous post took a while to trow in the ESP-01s context. Hahaha, sorry.Thank you for your suggestion, I will try the fix asap!
How can I limit a device's current draw from a cheapo Boost/Buck?  - Page 1
Forum section: electronics / beginners

author: monster_of_electronics
author_rank: Contributor
timestamp: January 01, 2016, 09:32:42 am
content: I'd like to use one ofthesecheap boost/buck converters w/a 3S li-po battery to charge a laptop, but the laptop can draw as much as 4 amps continuous @ 15v, it doesn't seem wise to trust the said cheapo boost converter for more than 70% of it's advertised max continuous ampacity.A slower charge is fine in this case, how can I restrict how much current the device (laptop) can draw without modifying the device.

author: mikerj
author_rank: Super Contributor
timestamp: January 01, 2016, 11:19:52 am
content: This will be very difficult indeed. You'll need to reverse engineer the laptops battery charging circuit and determine which component sets the maximum charge current. Obviously you can't really lower the power consumption of the rest of the mainboard (CPU, north/southbridge,hard drive etc..) but this shouldn't be a problem if you never actually power up the laptop.However the current consumption when only charging the battery (laptop powered down) may be a fair bit less than 4 amps. Why not measure the current consumption in this condition (with a discharged battery) before modifying anything?

author: Ian.M
author_rank: Super Contributor
timestamp: January 01, 2016, 11:25:43 am
content: Try and see if the laptop will charge from a current limited bench supply set to 15V O/C and 2A S/C. If it will, there is a fair chance it will also charge from a current limited boost/buck module, though there may be an undesirable interaction between the module's current limit feedback loop and the laptop charge controller that may cause the output to pulse. If you are going to experiment with this, I would advise a heavy duty crowbar circuit set to 16V in case the module output overshoots.
how can I measure AC voltage of bridge diode on PCB of CRT TV? - Page 1
Forum section: electronics / beginners

author: bshi02
author_rank: Regular Contributor
timestamp: May 04, 2024, 12:53:52 am
content: I read below article and I want to measure AC voltage of bridge diode on PCB of CRT TV with switching on.https://www.electronicsrepairmadeasy.com/2016/06/lg-21-crt-television-intermittent-dead.htmlBut as far as I know,When I measure any voltage in HOT area of CRT TV's PCB,I should place black probe to negative pin of The biggest capacitor(main filter capacitor) in Hot area.Then If I measure AC voltage of bridge diode(TS4B05G) which is located in Hot area of CRT TV,After setting analouge meter to AC voltage mode,Should I place black probe to negative pin of The biggest capacitor(main filter capacitor) in Hot area and place red probe to #pin2(AC) or #pin3(AC) of soldering point of bridge diode(TS4B05G)?or Is it not necessary to place black probe to negative pin of The biggest capacitor(main filter capacitor) in Hot area when I measure AC voltage of bridge diode(TS4B05G) but I only need to place black probe to#pin2(AC) and red probe to #pin3(AC) of soldering point of bridge diode(TS4B05G)??

author: wasedadoc
author_rank: Super Contributor
timestamp: May 04, 2024, 07:49:03 am
content: Your final paragraph is correct.

author: MathWizard
author_rank: Super Contributor
timestamp: May 04, 2024, 11:14:03 am
content: I don't like probing by hand much of anything AC powered, especially if I don't know the circuits. Do you have alligator clips, or a soldering iron ? With the power off I'd find solid places to attach clips, or solder on wires, and clip onto them.If you're not sure about using a DMM, I'd say read up on some safety stuff too. Modern TV's can still have some pretty high voltages in them, even after turned off for a while.

author: CaptDon
author_rank: Super Contributor
timestamp: May 04, 2024, 01:02:29 pm
content: If you want to measure the A.C. input voltage to a bridge rectifier wouldn't simple logic tell you to place your meter across the two A.C. input terminals of the rectifier?? And likewise to measure the D.C. output of the bridge you would measure across the + and - output terminals. You better be using a battery operated meter if you are probing around in the hot side of the SMPS. And be aware that on the output side of the SMPS the switching frequency could be 20KHz to 50KHz and switching waveforms in that area require an oscilloscope. Be careful and don't take any measurements in the hot side of the supply with equipment that is grounded (like a scope) unless you are using an isolation transformer to feed the device under test.
How can I measure R-on for a QS3125 quad switch? - Page 1
Forum section: electronics / beginners

author: crang
author_rank: Newbie
timestamp: September 28, 2012, 08:53:50 pm
content: I tried to measure it directly, my multimeter exhibit 0.5V on probes for 200 ohm scale, but no matter if OE (enable pin) is at ground, or +5V, switch is open (infinite resistance). It should be around 5-7 ohms. I also tried to ground one end of switch but results are the same.Am I doing it wrong or IC is dead?

author: robrenz
author_rank: Super Contributor
timestamp: September 28, 2012, 09:05:38 pm
content: Power it up and enable it, supply a known current (within its capacity) through the enabled switch pins and measure the voltage drop across the same pins. compute the resistance from the current and voltage drop.
how can i measure the current from a negative voltage rail using cheap INA1xx? - Page 1
Forum section: electronics / beginners

author: JPortici
author_rank: Super Contributor
timestamp: September 30, 2017, 04:57:11 pm
content: Hi,i've been scratching my head a bit today on this one:I want to measure the current on a bipolar power supply, using those theap INA current sense amplifiers from texas.positive voltage rail, that's easy, follow the datasheet.negative voltage rail, ehr not so easy. Common mode range goes from GND - 0.3V to 26V.If i had the sense resistor on the GND side it would be easy, common mode is inside range, but that would be pretty impractical (basically have two grounds.)What can i do then?I've seen some solutions, suggesting to use the negative rail as virtual ground, generating a local 5V difference using a zener and then apply a black box (kindly left as an excersise to the reader) to shift the voltage up to the 0-5V range.makes sense, should work, but the simulator though doesn't agree and i don't have the parts to test it in the real world.

author: danadak
author_rank: Super Contributor
timestamp: September 30, 2017, 06:48:03 pm
content: Not sure but seems if your load Rsense to ground is cut to a value suchthat Iloadmax X Rsense > -0.3V it should work ?So if load is max 10A, then Rsense <= 30 mohms ?But then there is this -http://e2e.ti.com/support/amplifiers/current-shunt-monitors/f/931/p/616053/2269385Regards, Dana.

author: JPortici
author_rank: Super Contributor
timestamp: September 30, 2017, 06:54:06 pm
content: But as i said i don't want to do that. Resistor has to be on the -12V side, current is 600mA max
How can I proportionally increase current draw from a load? - Page 1
Forum section: electronics / beginners

author: doublec4
author_rank: Regular Contributor
timestamp: December 13, 2020, 06:59:54 am
content: Hi all,I have a powered RFID tag that consumes very little current (~2mA). I would like to use a high side current sensor to read the current... however the load of the RFID tag is low compared to the range of the current sensor (let's say 1-10mA).Is there a way to proportionally increase the current draw from the RFID tag to somewhere closer to the middle of the sensor range, ie. 5mA ?So when I say proportionally increase, for example if the RFID tag current drops to 1mA, the current being seen by the current sensor would also drop by 1/2 to 2.5mAHope this isn't a silly question! I know another option is to change the R_sense of the current sensing device but if possible I would not like to try and modify the surface mount part if I do not have to.Thank you

author: ledtester
author_rank: Super Contributor
timestamp: December 13, 2020, 07:21:33 am
content: How about use a current sensor with a programmable gain amplifier? For instance, the INA219 can be programmed for /1, /2, /4 or /8 gain.Nice summary of current sense modules commonly used with microcontrollers:https://youtu.be/cG8moaufmQs

author: S. Petrukhin
author_rank: Super Contributor
timestamp: December 13, 2020, 09:45:13 pm
content: No amount of persuasion and arrangement can get more current consumption from RFID, you will have to change the circuit. Maybe you will be satisfied with a parallel shift of the current consumed to the sensor's sensitive area by simply installing a resistor in parallel with the RFID power?

author: David Hess
author_rank: Super Contributor
timestamp: December 13, 2020, 11:14:01 pm
content: Either offset the current by adding another fixed current through the current sensor or multiply the current, which can be done with a current mirror.
How can i put "gravity" to (Lat, Long to X, Y, Z) ? - Page 1
Forum section: electronics / beginners

author: ammjy
author_rank: Regular Contributor
timestamp: April 18, 2019, 08:10:53 am
content: Hello, EEVBlog users !Always thank you for your kind help and time.I want make acceleration data through convert (Lat, Long to X, Y, Z).but, i can't figure out how i can put "gravity" to X, Y, Z equationsto make acceleration data.if latitude and longitude is,Lat = [-30:2:30];Long = [-90:1:90];i can make latitude and longitude as follows,lat = lat * pi/180;long = long * pi/180;phi = pi/2 - lat;theta = long;than, XYZ isx = sin(phi) * cos(theta);y = sin(phi) * sin(theta);z = cos(phi);Can I add g like this?g = [ 0 0 9.8 ];Acc_x = -g * sin(phi) * cos(theta);Acc_y = g * sin(phi) * sin(theta);Acc_z = -g * cos(phi);I am so sorry, my question is so vague.If you don't mind, could you give to me advise ?Thanks you for reading, !Please, let me know !

author: agehall
author_rank: Frequent Contributor
timestamp: April 18, 2019, 08:20:13 am
content: If you just want a vector that represents the direction of g at every point of the sphere, that would essentially be the negative normal at each point.So just use g=-9.81 (note: not a vector!) and then calculate the vector at each point by doing g * [x y z] where x, y and z are calculated as you suggested and you should end up with a vector that describes g as a directional vector at each point [x y z].

author: ammjy
author_rank: Regular Contributor
timestamp: April 18, 2019, 08:27:22 am
content: Thanks you so much, also Thanks you for your time, Ms. Agehall.I understood your kind answer.Have a good day !Acc_x = -g * sin(phi) * cos(theta);Acc_y = -g * sin(phi) * sin(theta);Acc_z = -g * cos(phi);

author: soldar
author_rank: Super Contributor
timestamp: April 18, 2019, 10:33:38 am
content: Quote from: agehall on April 18, 2019, 08:20:13 amThat is a simplification that might be sufficient or not depending on what the objective is. It assumes the world is a sphere and with uniform acceleration of gravity.For more precise calculations search for "convert wgs84 to polar"https://www.pgc.umn.edu/apps/convert/

author: ammjy
author_rank: Regular Contributor
timestamp: April 18, 2019, 11:21:54 am
content: Thanks you for your time, and your kind attention !i understood very well your pointi totally agree.
How can I recognize Maxim Fakes - Specifically MAX4820 - Page 1
Forum section: electronics / beginners

author: sijmen
author_rank: Contributor
timestamp: August 02, 2021, 10:13:50 am
content: Hi,I'm looking for some MAX4820 chips to experiment with. Element 14 has them for about AUD$4.60 each, while on Aliexpress they are about AUD$1.85 eachI've read reports of fake Maxim chips being offered out of asia. Now I figure these are either fakes, or they're real product and the supplier has so many of them, they can sell them at a more competitive price point.How can I recognize a fake Maxim chip?Regards,Sijmen.

author: Zero999
author_rank: Super Contributor
timestamp: August 02, 2021, 11:11:14 am
content: If you buy them from a distributor, such as Element 14, it's highly unlikely you'll get fakes.If you buy them from Aliexpress, it's highly likely you'll get fakes.My advice is buy them from a distributor. Even though it's just over double the price, you have peace of mind.
How can I reproduce this failure? - Page 1
Forum section: electronics / beginners

author: Chabscan
author_rank: Newbie
timestamp: April 05, 2024, 05:19:37 pm
content: Hello.I am checking an electronic cover for a wiper motor. The relay driver / voltage regulator 2550klp is completely blown at its input.I now am trying to replicate this in my table but it seems just cranking up the supply does not do it, it works normally at 13.5 VWhat could actually have happened in the vehicle to specifically damage this component?Thanks a lot in advance.

author: floobydust
author_rank: Super Contributor
timestamp: April 05, 2024, 05:37:21 pm
content: Where is the IC's datasheet, and rest of the schematic.Inputs from the wand are 12V? CTRL goes to relay driver transistors?There are many reasons for the IC to burn up.

author: mikerj
author_rank: Super Contributor
timestamp: April 05, 2024, 05:43:53 pm
content: The Allegro 2550 example circuit shows a diode in the VBB supply, presumably for reverse polarity protection, and your schematic doesn't include this, so perhaps the battery was connected backwards (quite common in the automotive world).

author: BennoG
author_rank: Frequent Contributor
timestamp: April 05, 2024, 06:14:37 pm
content: In a car the voltage can go up to 14V when a normal battery is connected.If there is no battery connected or one that is almost dead the voltage can go up to 18vBut my guess is reverse voltage connected.Benno
How can I switch on a high-current device with a CMOS switch or similar? - Page 1
Forum section: electronics / beginners

author: Marmotta
author_rank: Contributor
timestamp: September 06, 2019, 08:22:29 pm
content: I'm building a PC using an Intel NUC motherboard and an external graphics card - both will run off 12V, but when the motherboard is in standby, the graphics card fan with run at full speed, as the 12V will always run to it as long as the power supply is connected to the mains.Ideally I'd want a positive voltage from the motherboard (between 3-5V or so) sent to a circuit that will then relay the 12V to the graphics card when the motherboard is powered on. I know CMOS switches can perform similar tasks in low current scenarios, but the graphics card can pull 75W, so the current would be around 6.25A, far higher than anything I've seen. Any ideas on how to get around this? I think there might be a pre-built solution out there already specifically for small factor PC builds, but as I need to make a custom PCB for parts of it anyway, I'd rather just stick my in circuit on it as well.

author: ledtester
author_rank: Super Contributor
timestamp: September 06, 2019, 08:34:58 pm
content: Quote from: Marmotta on September 06, 2019, 08:22:29 pmHow about using a 5V relay? Relays like this are good for 10A:https://www.amazon.com/Tolako-Arduino-Indicator-Channel-Official/dp/B00VRUAHLE/ref=asc_df_B00VRUAHLE/Alternatively hook up your fan to temperature controlled fan controller so it only runs when it's hot, like this one:https://www.ebay.com/itm/12V-PWM-Fan-Temperature-Speed-Controller-Module-High-Temp-Alarm-5V-Buzzer-PC-CPU/263605466941

author: mariush
author_rank: Super Contributor
timestamp: September 06, 2019, 08:56:20 pm
content: Check your video card, it may have a 4 pin fan connector, which means the video card's firmware may be able to dynamically adjust the fan speed based on heatsink temperature.Alternatively, you can buy a fan controller and glue the NTC (temperature sensor tip) to the heatsink, then optionally configure the min and max temperatures :https://www.ebay.com/itm/PWM-4-Wires-Fan-Temperature-Controller-Speed-Governor-DC-12V-for-PC-Fan-Alarm/372494614639?epid=24023606409&hash=item56ba68c06f:g:yBYAAOSw1cdb4qmdThere's instructions attached to the ebay listing above, it's fairly easy to use once you understand the instructions

author: Marmotta
author_rank: Contributor
timestamp: September 06, 2019, 09:07:10 pm
content: Ah, yes, a relay should do the trick nicely, thanks.As for the fan, it's a non-issue if I can regulate the 12V power going to the graphics card. When the motherboard is turned on, I can regulate the fan speed via software.
How can i test APC UPS without a battery - Page 1
Forum section: electronics / beginners

author: sairfan1
author_rank: Frequent Contributor
timestamp: November 19, 2021, 05:09:18 pm
content: I attached picture of APC UPS model Back-UPS RS 900.It does not have battery and I'm not sure if its working good.I want to spend money for battery once I'm sure if its all good.Is there a way to test a UPS if we do not have matching battery model?

author: HB9EVI
author_rank: Frequent Contributor
timestamp: November 19, 2021, 05:12:42 pm
content: you might try with a power supply able to deliver the necessary current, although it can happen that if you use a SMPS, it cannot handle the high inrush current even if it has the necessary power rating

author: SL4P
author_rank: Super Contributor
timestamp: November 20, 2021, 08:59:45 pm
content: That’s a baby UPS, with a single SLA battery inside.For $20 you can put a new battery in.If it works, great. If not, you have a useful battery to use on other projects.Remember to never let SLA batteries over discharge!

author: Gregg
author_rank: Super Contributor
timestamp: November 21, 2021, 04:52:35 pm
content: Your UPS uses a 12 volt nominal lead acid battery; any reasonable capacity lead acid battery would suffice for testing. If you can extend the battery leads outside the case and connect to a known good automotive battery it should work. Put a fuse inline in case the UPS has a major fault.

author: james_s
author_rank: Super Contributor
timestamp: November 21, 2021, 06:18:00 pm
content: I don't think I've ever seen a UPS that didn't have a fuse on the battery internally, you shouldn't even need to add a separate fuse, although it won't hurt to do so. The vast majority of non-working UPS's I've encountered just needed a new battery.
How can our electronic hobby and skills help in survival situations? - Page 1
Forum section: electronics / beginners

author: VladKEasternTiger
author_rank: Regular Contributor
timestamp: March 08, 2010, 11:37:20 pm
content: Hi everyone Im into my bushcraft and survival activities even thoe again Im learning more in this area, topics like "off the grid living" and self sufficient lifestyle. I like the idea of living "off the grid" not totally but its good to have a option to reduce our dependance on the electricity grid, I like to be self sufficient in food and other things, im not against all technology and things we use but im wondering if electricity disappeared tomorrow what devices could we use and how can our electronic hobby come into play to help us survive? If you get what im saying, when we think of electronics people assume televisions and plastations and ipod. I know electronics is more than that like the medical field and space exploration, but I dont know if you know ways we can use what we know to help in a survival situation? I seen one video off a fella that build power batteries and a generator from wind/sun solar to his home, surley they is more than only this idea and where do the circuit boards, components and stuff come into play here?

author: djsb
author_rank: Super Contributor
timestamp: March 08, 2010, 11:47:40 pm
content: Hi,There was a series done by the BBC (now on DVD) called rough science.http://www.open2.net/roughscience/There's also the centre for alternative technology in Wales.http://www.cat.org.uk/index.tmpl?refer=index&init=1Maybe not exactly what your looking for but a start.David.London,UK

author: VladKEasternTiger
author_rank: Regular Contributor
timestamp: March 09, 2010, 12:26:00 am
content: Quote from: djsb on March 08, 2010, 11:47:40 pmthanks dav im tired now zzzzzzzz will look tomorrow thanks my friend

author: Simon
author_rank: Unknown
timestamp: March 10, 2010, 07:37:31 am
content: if we no longer have elctricity you will have a hard time practicing electronics, I'm into making some of my own popwr and set myseft up with some solar pannels but nowhere near enough power to even allo me to be sel sufficient in electronics mainly because now unlike the past i need my PC for electronics. I'm thinking of taking my panels camping with me to run a fridge and music.