hybridfree/eevblog-posts huggingface dataset:
best way to mix a few audio signals? - Page 1
Forum section: electronics / beginners

author: dentaku
author_rank: Frequent Contributor
timestamp: February 05, 2016, 11:27:03 pm
content: I built a simple circuit that take a 2V p-p triangle wave from my little DDS function generator (or any audio signal) and turns it into a square wave using a LM358 as a comparator. I have a pot that lets me adjust the pulsewidth by moving the point at which the comparator flips.This then goes through a divide by three circuit made with a 40hc386 and a 40103.This gives me three different signals, none of them are AC coupled and some of them are 0-5V.I also have a 74393 on the same breadboard that lets my divide it by 2/4/8/16 etc.QUESTION: What's the proper way to mix a bunch of signals like this together. I want to output the mixed signal to an audio amp in the end.There's lots of different info about building simple mixers online but I was just wondering what the EEVBlog forum members think.

author: Synthetase
author_rank: Regular Contributor
timestamp: February 05, 2016, 11:38:27 pm
content: You may findthis articlehelpful. It goes through the pros and cons of different techniques.

author: sync
author_rank: Frequent Contributor
timestamp: February 05, 2016, 11:48:32 pm
content: This is the mixer of an Arp Odyssey. Very simple. The inputs are DC coupled. The output to the VCF is AC coupled.

author: dentaku
author_rank: Frequent Contributor
timestamp: February 06, 2016, 01:31:03 am
content: Quote from: Synthetase on February 05, 2016, 11:38:27 pmI've found lots of useful from Rod Elliott in the past
Best way to power cycle 5-19V device - Page 1
Forum section: electronics / beginners

author: bryce1
author_rank: Regular Contributor
timestamp: May 19, 2015, 07:53:39 am
content: Hi guys,I have developed a watchdog device that can power cycle a device by cutting of power via a low side n mosfet switch. As I want to make this a bit more professional, I wanted to pick your brains. Some people I talked to considered the low side switch a bad idea because you dont know what happens inside an embedded device if you take away ground.How do I do this "better"?As the attached device is not always the same one, I can only work from the spec of 5-19V up to 1.5A.Thanks!

author: Rerouter
author_rank: Super Contributor
timestamp: May 19, 2015, 07:57:58 am
content: use a high side with a charge pump?, if you have any other connections other than power to the end device that are not isolated, you may damage things when there inputs suddenly go from ground to -15V

author: Jeroen3
author_rank: Super Contributor
timestamp: May 19, 2015, 08:00:19 am
content: The enable pin on the regulator.

author: bryce1
author_rank: Regular Contributor
timestamp: May 19, 2015, 08:02:27 am
content: There is no regulator, the device sits between the wallwart and the device.Quote from: Rerouter on May 19, 2015, 07:57:58 amThe other connection is ethernet, so it is opto-isolated.

author: matseng
author_rank: Frequent Contributor
timestamp: May 19, 2015, 08:23:49 am
content: Quote from: bryce1 on May 19, 2015, 08:02:27 amUnless you are having a opto-fibre Ethernet the isolation device would be a small transformer, not an opto coupler... But it's still isolated so that shouldn't be a worry here... ;-)

author: Simon
author_rank: Unknown
timestamp: May 19, 2015, 08:24:14 am
content: If you are removing power from the whole negative of a device it would be ok but if that is connected to other power references then you may have a problem, if your not using much power a P channel mosfet will do it, as mosfets gates can work from 1-15V you should have no problem getting a potential divider ratio that will work for a varying range.
Best Way to Prepare for the Eccouncil 312-50 Exam - Page 1
Forum section: electronics / beginners

author: charleshood
author_rank: Newbie
timestamp: March 03, 2025, 08:54:04 am
content: The EC-Council 312-50 Certified Ethical Hacker (CEH) exam tests candidates on essential cybersecurity skills, including penetration testing, network security, and ethical hacking techniques. To prepare effectively, it’s important to use reliable Certified Ethical Hacker v13 study materials and312-50 Exam Questions. Platforms like P2PExams provide CEH practice questions and study resources that help candidates familiarize themselves with the exam format and key topics. By using such resources, learners can assess their understanding, identify weak areas, and improve their problem-solving skills before the actual exam.

author: ahsrabrifat
author_rank: Regular Contributor
timestamp: March 14, 2025, 06:46:00 am
content: You can study “Certified Ethical Hacker (CEH) All-in-One Exam Guide” by Matt Walker.
Best way to sense presence of voltage on wide range power rail - Page 1
Forum section: electronics / beginners

author: FartingNoveltyToyEngineer
author_rank: Newbie
timestamp: July 05, 2025, 08:16:26 pm
content: I want to sense the presence of voltage which can range from 3.3 to 30 volts. Output signal should be 3.3v logic level and preferably it wont fry the io pin in any case. I have brain stormed these potential solutions, one with a zener diode and one which uses a 3.3v reference supply already present in the system. Are these any use? Please feel free to share your solutions and please note this is mostly for learning purpose.

author: TimFox
author_rank: Super Contributor
timestamp: July 05, 2025, 09:16:09 pm
content: Do you have a tolerance spec for the 3.3 V end of your input voltage range?If it is wide tolerance, you can just use a resistor driving the base of a transistor with any reasonable collector supply, possibly adding a couple of diodes in series with the resistor and another resistor from base to emitter.

author: FartingNoveltyToyEngineer
author_rank: Newbie
timestamp: July 05, 2025, 10:27:29 pm
content: Basically in my application it's safe to assume that if the supply is anything under 3.3v then it's off. But thanks, that sounds quite an elegant solution.

author: lakis70
author_rank: Contributor
timestamp: July 06, 2025, 12:03:24 am
content: use a ldo regulator with shutdown function, use a voltage divider to set the limit. Look LK112 and for others similarfor 30V and more LP2950, LP2951 adj output. Look circuits at onsemi datasheet.
(solved) best way to simulate 30amps on components. - Page 1
Forum section: electronics / beginners

author: whitevamp
author_rank: Regular Contributor
timestamp: September 21, 2016, 07:17:15 am
content: i am want to see how components react to 30 amps of current and i have used ltspice, multisim, and Circuit Wizard for this but i had noticed that if i place a dmm/ get the voltage at any node it will show 30kv useing an amp source of 30, but if i use 17vdc there is no amps/ very little.so what is the correct way to simulate this?PS: im looking at making a variable 17VDC 30AMP ( minus of coarse all the voltage drops from the components. ) CC/CV bench power supply from an old rv inverter transformer that is 17VDC 30AMP.

author: alanb
author_rank: Frequent Contributor
timestamp: September 21, 2016, 08:31:53 am
content: The load resistance on the output of your simulation will need to be 17/30 Ohm i.e. 0.57 Ohm to draw 30 Amp from a 17 Volt supply.

author: Delta
author_rank: Super Contributor
timestamp: September 21, 2016, 12:21:03 pm
content: Ohm's law.

author: whitevamp
author_rank: Regular Contributor
timestamp: September 21, 2016, 02:59:17 pm
content: I see what my mistake was now.I was just using an amps source, and not a voltage source and then using ohs law to figure out the correct resistor value.thanks for the help with this issue/question.
Best way to solder 13 pin 1.25 mm pitch FFC on board - Page 1
Forum section: electronics / beginners

author: Jphb1
author_rank: Newbie
timestamp: March 29, 2020, 07:17:15 pm
content: I have this PCB where 13 cable pins used to be soldered and got sheared off. I stripped the cable and got the 13 pins exposed again (I also got a new FFC).Is it an easy task for a beginner to solder the 13 pins back on the board directly or am I better off trying to surface mount a connector?

author: fabiodl
author_rank: Frequent Contributor
timestamp: March 29, 2020, 10:54:08 pm
content: I'd definitely go with a connector. ffc cables melt very easily.

author: bob91343
author_rank: Super Contributor
timestamp: March 30, 2020, 12:43:19 am
content: I have a similar problem. I need to solder a USB C connector to a board. The pitch is so fine I need a magnifier just to see it. I wonder how I can get it done.
Best way to switch large current spikes? - Page 1
Forum section: electronics / beginners

author: s3c
author_rank: Contributor
timestamp: October 07, 2010, 06:59:41 pm
content: I'm currently working on a project that requires me to discharge a cap with virtually no load, ie, just short it out. I'm working with a 100uF cap charged at 300V and above. What would be the best way to switch the connection? Will transistors/fets be able to handle such large current spikes?

author: Time
author_rank: Frequent Contributor
timestamp: October 07, 2010, 07:03:23 pm
content: There are switching devices that can handle that just fine. Mosfets, IGBTs, SCRs just to name a few. Depends on how fast you need to switch it and how much money you have really.

author: Simon
author_rank: Unknown
timestamp: October 07, 2010, 07:08:10 pm
content: A general use mosfet rated at over 300V that can handle up to 30+ amps ? if your worried about blowing it put a small resistor in series with the mosfet channel to control the current,

author: Zad
author_rank: Super Contributor
timestamp: October 07, 2010, 09:01:05 pm
content: Be aware that crowbar-ing caps can sometimes make them go BANG as they heat up and boil the dielectric.

author: s3c
author_rank: Contributor
timestamp: October 08, 2010, 06:18:36 am
content: I haven't heard of IGBT's and SCR's before, looked them up and I think an SCR is near perfect, thanks Time. I'm kinda cautious about using parts with current ratings below 100A, the cap will most likely have a resistance to keep the current below that but since I have no data on it there's no way to know. A load resistor is probably a good idea... Thanks all.

author: Murphy
author_rank: Regular Contributor
timestamp: October 08, 2010, 09:03:46 pm
content: SCRs do the trick, they can handle huge pulse currents many times what their continuous rating is.
Best way to tap/mirror a temp sensor reading? - Page 1
Forum section: electronics / beginners

author: rthorntn
author_rank: Frequent Contributor
timestamp: September 26, 2023, 12:06:17 am
content: Hi,I have a new Reclaim heat-pump and they won't provide me with a way to get at the tank temperature (I can turn the heater on/off with dry contacts).So I was thinking...Reverse engineer the modbus NAHProxy their cloud comms NAHHack the Android app to get the data NAHTry and add a second sensor into the tank sensor well NAHAnd I arrived at somehow just grabbing the resistance directly from the temperature cable, are there any pitfalls to this, what would be the cleanest and easiest way for me to get that temperature value?ThanksRichard

author: jwet
author_rank: Frequent Contributor
timestamp: September 26, 2023, 01:07:52 am
content: The temp sensor is likely part of a bridge or a voltage divider with some kind of stimulus and readback. Just meaure the voltage across it. This correlates with the current temp. Force a large temperature change and measure again. You now have 2 points to define a line. Getting a third would be good. Once you get the values with a DVM, make a little op-amp circuit to scale it to what ever you want. Try to keep the loading minimal to not mess up the existing circuit. You might be able to reverse engineer the input components on the PCB too.

author: Terry Bites
author_rank: Super Contributor
timestamp: September 27, 2023, 07:24:22 pm
content: J4 on the PCB looks like its got TEMP written under it. The coax calbe suggest that there is a small signal running though there.It looks very basic so I doubt they've used anything more than the cheapest (10K) thermistor at the other end.More cheap assery means that the the coax centre connects to V+ via the pull up resistor.You can see a bit of RFI and over voltage protection and what maybe a pull up resistor, R82?If this isn't my fantasy bullshit the voltage across J4 will be roughly proportional to T.Strap a thermometer to the pipework nearby and then use your DMM and find out.If so, then its easy to throw a digital voltmeter module 200mV (Ebay Ali etc.).Get the Slope and Intercept if you can.Scale with high value resistors and offset as per.If its a severe curve then its going to get complicated. Open a beer and congratulate yourself, or not as the case may be.
Best way to test a switch-mode power supply? - Page 1
Forum section: electronics / beginners

author: Mavro
author_rank: Contributor
timestamp: May 22, 2014, 12:27:32 am
content: Hi there!I'm trying to compare the quality of a switch-mode power supply -- a 12v 2.5A cheap chinese wall wart ($6.99) vs a 12v 2.5A "quality" CUI ($20). Does anyone have a tutorial? I want to measure noise and ripple being generated (if any) and just see if there is an overall quality differences are between the two.I have a Rigol 2000 series scope, electronic load and Agilent 34661A DMM -- what's the best way to test a power supply... Dave, anyway of doing a video on this topic?Thanks!Danny

author: poorchava
author_rank: Super Contributor
timestamp: May 22, 2014, 07:04:32 am
content: For testing a power supply you'll need an active load or a high power resistor array to impose varying loads on the power supply. In general you want to observe on the oscilloscope how ripple, voltage and general shape out the output waveform will look like at varying load levels.You can also check the mains input (be careful with that) to check if the power supply creates any interference on the power line.

author: VK5RC
author_rank: Unknown
timestamp: May 22, 2014, 09:36:35 am
content: One of the big issues is the earth lead can act as an antenna and pick up switching noises that aren't really on the power supply line, very short tails from coax at the supply not the load, I recall a good you tube discussion but can't find it easily. Don't use a standard cro lead as it is too susceptible to pick up stray signals.

author: Mavro
author_rank: Contributor
timestamp: May 22, 2014, 11:53:48 pm
content: Quote from: VK5RC on May 22, 2014, 09:36:35 amThat's why I have been noticing -- lots of external noise when trying to probe the supply. If you have a youtube discussion that would be great -- maybe a good topic for Dave to do a video on?

author: VK5RC
author_rank: Unknown
timestamp: May 23, 2014, 12:01:32 am
content: Dave has done one

author: Mavro
author_rank: Contributor
timestamp: May 23, 2014, 03:23:54 pm
content: Quote from: VK5RC on May 23, 2014, 12:01:32 amDOH! Thanks!
Best Way To Test Capacitors With A Multimeter? - Page 1
Forum section: electronics / beginners

author: JakeC
author_rank: Newbie
timestamp: October 20, 2013, 10:22:31 am
content: Hi,I am attempting to repair our old TV. When you turn it on the backlight only stays on for about a second. After some research I believe it is one of the caps, I have read about using the ohms range to charge the cap then measuring it with volts DC. Is this the best way?ThanksJake

author: DL8RI
author_rank: Regular Contributor
timestamp: October 20, 2013, 11:04:33 am
content: Hi,at first I would try a visual inspection, normally the Caps are visually damaged.Charging the caps (any battery does the job, you don't have to use the Ohm-Range) and discharging them via the input-impedance of your DMM would do, then you have to calculate your time-constant (tau=RC) and so on... They have to be desoldered first!Faulty caps normally have a big difference in Capacity (nF instead of µF), so this method may be accurate enough, but this is kinda annoying. Maybe it's time for a new DMM, even the cheaper ones have a C-Measurement build in.Another type of diagnostic is the ESR, I'm not sure if the new DMMs can measure this (mine can't).

author: Unknown
author_rank: Unknown
timestamp: October 20, 2013, 11:23:00 am
content: In general ESR is a better diagnostic of failed caps in switching power supplies than capacitance. I don't know of any DMM that can measure ESR, you would generally look at LCR meters or dedicated ESR meters (e.g. the Bob Parker design). I don't see how you'd improvise an ESR measurement with just a DMM, in general you'd use a function generator and oscilloscope for that. Forum user krypton2035 has collecteda bunch of DIY ESR meter schematicson his website.
Best way to use PTC thermistor in fan controller ? - Page 1
Forum section: electronics / beginners

author: lordvader88
author_rank: Frequent Contributor
timestamp: June 12, 2019, 08:29:48 pm
content: I'm making something basically like this PWM circuit for a 12V 4-pin CPU fan. It doesn't have to be super accurate and I might just make it without the thermisitor for now.http://www.paulvdiyblogs.net/2015/08/controlling-temperature-driven-fan-with.htmlI'm wondering , what's the difference between a circuit that sends a precise constant current through the PTC therm. like from TL431 and transistor,,, and a circuit that allows the PTC current to change with it's resistance ?

author: cur8xgo
author_rank: Regular Contributor
timestamp: June 12, 2019, 08:34:32 pm
content: Quote from: lordvader88 on June 12, 2019, 08:29:48 pmWell so analyze like this:PTC resistance changes in both cases.In constant current case, as resistance changes, voltage will change, so voltage is signal.In constant voltage case, as resistance changes, current changes, so current is signal. If you put another resistor in series with it, you turn that current signal into a voltage signal.

author: lordvader88
author_rank: Frequent Contributor
timestamp: June 12, 2019, 09:39:18 pm
content: Somewhere I've mapped out the PTC therm PWM circuits on quality computer PSUs, but that's OTT for this, and there's not much space left on the PerfCB. So I might use only a 555 circuit. Soon I need an excuse to copy that good computer PSU circuit tho. They use the TL431 in a type 2 or 3, something or other setup icr, such that the Bode plot and transfer functions act better.

author: mariush
author_rank: Super Contributor
timestamp: June 12, 2019, 10:36:43 pm
content: You could use the PTC to limit the voltage to the fan... for example you can use a linear regulator to adjust between 7v and 12v depending on temperature. Just insert the PTC in the adjustment loopYou could use a npn transistor in linear region to limit the current based on the PTC value.You could also just use the PTC in a voltage divider and read the voltage with the ADC of a microcontroller, then PWM accordingly - a 6-8 PIC10 micro (or an attiny) would do it.No need for a TL431 voltage reference, when you have an internal reference or you can just use 5v as reference ... and pic programmers are now 15$ or less.For example a PIC10F320 will do the job... in DIP package like a 555 :https://www.digikey.com/product-detail/en/microchip-technology/PIC10F320-I-P/PIC10F320-I-P-ND/2764510
Best ways to get constant 5V output from a single cell and external supply? - Page 1
Forum section: electronics / beginners

author: Ddkdjdjdj
author_rank: Newbie
timestamp: September 18, 2023, 02:17:19 pm
content: Dear all,"Get a Constant +5V Output by Switching Between a +5V Input and a Single-Cell Li+ Rechargeable Cell"https://www.analog.com/en/design-notes/get-a-constant-5v-output-by-switching-between-a-5v-input-and-a-singlecell-li-rechargeable-cell.htmlDoes anyone know of any ICs which can do what the article talks about with a single chip?Thanks

author: janoc
author_rank: Super Contributor
timestamp: September 18, 2023, 02:30:10 pm
content: Probably any of the powerbank chips will do what you want.

author: DavidAlfa
author_rank: Super Contributor
timestamp: September 18, 2023, 02:36:45 pm
content: No, you need a step-up converter, the simplest design will need at least some capacitors, an inductor and the switching IC.But you can find modules.

author: Peabody
author_rank: Super Contributor
timestamp: September 18, 2023, 02:50:28 pm
content: Power banks are designed to charge batteries, not to directly power a circuit. Power bank chips have a tendency to produce a short dropout when the external power is connected or disconnected. They also typically shut down if output current falls below some level. I don't know of any exceptions, but there may be some. So the first decision is whether you actually want a power bank or a UPS circuit.

author: Terry Bites
author_rank: Super Contributor
timestamp: September 18, 2023, 04:41:08 pm
content: You want a DC-DC converter with "pass-through" or "pass thru" if you live at AD. There are specific ic's with this function but they are mostly aimed at mobile devices. The come in bga packages so not easily on a home brew pcb or perfboard design. eg TPS61281DI think that a single chip solution will end up being an expensive haemorrhoid for you. I'd start on ebay.Many DC-DC boost conveters will pass though Vbatt-Vf, where Vf is the forward voltage of the external diode. Say 0.5V for a Schottky. Can you live with 4.5V?

author: LinuxHata
author_rank: Frequent Contributor
timestamp: September 19, 2023, 09:57:44 am
content: There are special power bank ICs, which can do both charge and boost at same time.Have look at injoinic website and ETA solutions too and consonance website. They have chips capable of doing that.Just note, if you need anything higher than 5V 2A output, there will be hard to solder at home chips, like DFN and BGA.

author: Infraviolet
author_rank: Super Contributor
timestamp: September 19, 2023, 02:34:10 pm
content: Keep in mind that the current you want at 5V needs a proporrtionally greater current at the cell's lower voltage to supply the step-up regulator, and that is before acounting for the regulator's imperfect efficiency (although this is often pretty good and close to 90%). It is my understanding that where single chip solutions are concerned they almost all require some amount of inductors and caps as external passives to do things which can't be fitted within a chip's geometry, but the datasheets usually tell you the parameters these external parts will need.
Better digital thermocouple IC than Max31855 - Page 1
Forum section: electronics / beginners

author: embedded.world@aol.com
author_rank: Contributor
timestamp: June 13, 2014, 09:16:50 am
content: Max31855 is digital thermocouple IC .Is there any better digitally compensated IC which have better resolution/accuracy & sampling time for K-type thermocouple

author: mariush
author_rank: Super Contributor
timestamp: June 13, 2014, 12:17:47 pm
content: I've recently made a thermometer using AD595 - amplifies thermocouple output to 10mV / C (+0.011mv/C offset) , +/-1 C for the precision version, +/-3C otherwise, up to 1250c, not just 0 to 700c. You still need a mcu to convert the voltage to temperature, but it's possible to get better than 0.25c steps.

author: echen1024
author_rank: Super Contributor
timestamp: June 13, 2014, 08:31:22 pm
content: Quote from: mariush on June 13, 2014, 12:17:47 pmI use the newer version of the chip, the AD8497.

author: nsayer
author_rank: Regular Contributor
timestamp: June 14, 2014, 02:54:23 am
content: I second the AD849x... In my case I chose the AD8495. A third the price of the 595, but it is only available SMD.
Better understanding of radio modulation techniques (SDR related) - Page 1
Forum section: electronics / beginners

author: Stonent
author_rank: Super Contributor
timestamp: June 14, 2015, 10:05:01 pm
content: I've been playing around with one of those USB DVB TV modules that can be easily used as software defined radio and was trying to better understand some of the transmission types.I understand AM, FM in general but not so much about upper/lower/dual sidebands, and CW.I get that upper and lower sidebands seem to move the transmission to just above or below the carrier, and dual is on both sides. CW I'm not as sure about but it seems to be more for morse code.When I'm sweeping looking for things with my SDR, is there a point where I need to be changing modes between USB/LSB/DSB and CW?I know AM is typically used at lower frequencies, and FM more so elsewhere, but not always. Terrestrial radio in the 86-108MHz band is all wide band FM, but amateur radio seems to be narrow band FM.Is there a common bandwidth I should be using when looking for radio broadcasts outside commercial radio?Right now I sweep around looking for the spectrum to move up and down in an area then just play around with LSB/USB/DSB and band widths until I get what sounds the best.

author: VK5RC
author_rank: Unknown
timestamp: June 14, 2015, 11:05:24 pm
content: I would suggest some reading of something like the ARRL Handbook, or the RSGB equivalent, which will go through it in a well constructed manner, you can receive CW with SSB, the tone you hear is the difference between the received Continuous Wave and the suppressed carrier the radio 're-inserts'.
Between these 2 simple circuits which one produce the lowest noise ? - Page 1
Forum section: electronics / beginners

author: Frederico Acardi
author_rank: Contributor
timestamp: August 14, 2021, 04:27:37 pm
content: Hello, I need to know if bypassing the unused part of the resistor has lower noise than not, see here :Thank you.

author: mariush
author_rank: Super Contributor
timestamp: August 14, 2021, 04:33:36 pm
content: They look the same to me ... in the first picture the wiper shorts out the second part of the potentiometer, in the second picture the part after the wiper is just floating.In both cases, you only have one resistor across output and ground.

author: Frederico Acardi
author_rank: Contributor
timestamp: August 14, 2021, 04:54:46 pm
content: Yes they achieve the same result, but does shorting the unused part or the potentiometer leads to lower noise ?Less stray noise pickup maybe or something like that or less EMI pickup ?Thank you.

author: FrancisM
author_rank: Contributor
timestamp: August 14, 2021, 04:56:31 pm
content: Noise wise, it's the same.I would choose the circuit on the left side for safety reason.If the wiper goes open, there will always be a path to ground for the following circuit at OUT, it will never float.

author: Frederico Acardi
author_rank: Contributor
timestamp: August 14, 2021, 05:02:18 pm
content: Thanks.Do I create a loop with circuit 1 on the left ?

author: FrancisM
author_rank: Contributor
timestamp: August 14, 2021, 05:15:40 pm
content: You can see it as a loop, but if using a pot or an adjustable, a tiny one with no effect.Given the value of R1, I suppose you're not playing at RF, so nothing to worry about.

author: Gyro
author_rank: Super Contributor
timestamp: August 14, 2021, 05:39:40 pm
content: The first one is better in that, if the wiper goes intermittent, there will still be the end-to-end resistance of the potentiometer in circuit, rather than going completely open circuit. It's normal to connect the wiper to one end of the potentiometer when creating a variable resistor for this reason.In terms of noise, the wiper contact on a potentiometer is always noisier when it is passing current. Ideally the wiper always feeds a high impedance stage. It doesn't help in this situation, but as you mentioned noise...

author: Frederico Acardi
author_rank: Contributor
timestamp: August 14, 2021, 05:49:00 pm
content: Hy chris, so the first/left one is better as safer, in case of wiper failure, but is noisier than the second/right version ?

author: Gyro
author_rank: Super Contributor
timestamp: August 14, 2021, 05:58:24 pm
content: Yes, the left one is a little better (and more common practice). No, it won't be any noisier than the right hand one - in extreme cases (intermittent wiper) it is quieter.
Beware Chinese Power Supply Modules - Page 1
Forum section: electronics / beginners

author: atw58
author_rank: Newbie
timestamp: February 24, 2017, 04:02:46 am
content: I added a 40V center tap transformer to a +-15V Chinese power supply module. There was a little smoke when powered on so I turned it off. Turned it on again to see where the smoke was coming then boom the large electrolytic cap after the bridge diodes blew up. It knocked out both lenses out of my glasses and really bent the frame. What happened? The cap was soldered in backwards. See this old posthttps://www.eevblog.com/forum/beginners/what-happens-when-you-put-an-electrolytic-capacitor-the-wrong-way/on the dangers of reversed caps.Worth remembering when assembling a power supply.

author: jh15
author_rank: Frequent Contributor
timestamp: February 24, 2017, 05:46:01 am
content: Was it a problem that it was a Chinese power supply or that it was abused?

author: ebastler
author_rank: Super Contributor
timestamp: February 24, 2017, 06:45:02 am
content: That sounds pretty scary. Glad that you were wearing glasses, and that your eyes did not suffer any damage!Would you have a link to the particular power supply module you used?And maybe a photo of the damaged module, just out of curiosity?

author: Rick Law
author_rank: Super Contributor
timestamp: February 24, 2017, 06:57:19 am
content: Quote from: jh15 on February 24, 2017, 05:46:01 amAbuse of a child with disabilities I would say. Growing up with the capacitor installed backward is going to be hard, and then this kid with disabilities has to carry a heavier load in life than designed...OP with bold+italic added:Quote from: atw58 on February 24, 2017, 04:02:46 am

author: wraper
author_rank: Unknown
timestamp: February 24, 2017, 07:06:31 am
content: Quote from: atw58 on February 24, 2017, 04:02:46 amRegardless of crappy PSU, why would you do so?Quote
bf199 equivalent - Page 1
Forum section: electronics / beginners

author: pitpat
author_rank: Contributor
timestamp: May 14, 2020, 04:10:07 pm
content: Hi guys, i need some help finding an equivalet for the bf199 pnp transistor for my hameg 103 oscilloscopehttps://www.datasheetarchive.com/pdf/download.php?id=e1ec0cc83cd2410ebf459526a2f35b17b44785&type=O&term=BCS49.I've read on an old tread that the bc547 npn will also work. is it true??Thanks

author: Andreas
author_rank: Super Contributor
timestamp: May 14, 2020, 07:10:16 pm
content: Hello,the BC547 has a different pin out and lower band width.Depending on the application it can work.On the other side: there are still some manufacturers which deliver the part with the original specs (CDIL) eg. sold here:https://www.reichelt.de/hf-npn-to-92-transistor-25-v-100-ma-350-mw-bf-199-p5433.html?&nbc=1with best regardsAndreas

author: pitpat
author_rank: Contributor
timestamp: May 14, 2020, 08:55:56 pm
content: Hi Andreas thanks for the help, the transistor should be for the y-preamp according to the schematics, ill'ask to my local supplier before ordering.

author: Yansi
author_rank: Super Contributor
timestamp: May 14, 2020, 09:03:07 pm
content: THT components has started to become quite difficult to find whenever anything tiny bit special is required, like this.The modern replacement could be something like a MMBTH10, you could use a small adaptor board to give it some "legs" so it will look more like the original one.

author: Andreas
author_rank: Super Contributor
timestamp: May 15, 2020, 04:47:12 am
content: Hmm,in the schematic I see "sel." below the BF199 writing.So obviously you need either paired (together with the other BF199) or some other special non data sheet parameters.with best regardsAndreas

author: pitpat
author_rank: Contributor
timestamp: May 15, 2020, 06:10:32 am
content: My bad, i've sent the wrong part of the schematic (confused 701 with 101 that also is a bf199), from what i see the 701 is part of the crt drive circuit.Now the thing is if the transistor is shut open why the crt works? i've got no trace but in component tester mode i see trace and results...

author: pitpat
author_rank: Contributor
timestamp: May 15, 2020, 06:16:40 am
content: Full schematics in herehttps://cdn.rohde-schwarz.com/hameg-archive/HM103_englisch.pdf
BG7TBL voltages of output signals - Page 1
Forum section: electronics / beginners

author: deanic
author_rank: Newbie
timestamp: November 21, 2020, 10:32:18 pm
content: Hi - I need to know the 1 pps and 10 MHz output voltages on theBG7TBL 2020-06-10 GPSDO.I need to connect the 10 MHz signal output on the GPSDO to 3 V imput of on a SDR.I did a Google search but I couldn't find anything - not even a datasheet for the device.I don't have access to an oscilloscope.Thank you.
BGA Chip Reballing - Solder Paste Amount - Page 1
Forum section: electronics / beginners

author: 2X
author_rank: Frequent Contributor
timestamp: June 14, 2024, 07:45:17 pm
content: Hello,I would like to ask your opinion about a reballing procedure. I bought the reballing kit at image 1. I applied a thin layer flux of chipquik SMD291 and I placed the solder balls, but when I removed the stencil, many of the solder balls have gone from their place (maybe I need to make more practice with my hand or a higher viscosity flux needed?) and also these that where stayed in the right place when I tried to heated them with the heat gun (at 330celcius and with the lowest air flow) all have been displaced at all. As I understand this process needs a Rework Station in order the BGA chip will be placed below the top nozzle and heated just with the ambient air flow (or am I wrong?).Another solution that I saw is to buy a rework kit like this in image 2 where it has more thicker stencils and they will not bend with the heat. With this I could heat the solder balls without removing the stencil and so the balls will be stay in place. This thin stencil at image 1 if I heated just a little starts to bend.Anyway, after searching on the internet I found out that the most people (on YouTube at least) use solder paste for reballing and also there are not many brands (mostly Chinese) with solder balls. So, I decided to try to use the solder paste method for reballing and my question is what must be the gap height between BGA chip and Stencil (image 3) in order to apply the right amount of solder paste?Solder paste I am going to use:TS391AX50Solder Paste No-Clean 50g Sn63/Pb37 T4

author: aliarifat794
author_rank: Regular Contributor
timestamp: June 15, 2024, 08:36:34 am
content: Thicker stencils are less likely to bend when heated, ensuring that the solder balls stay in place during the heating process. The rework kit with thicker stencils can be a good investment.

author: 2X
author_rank: Frequent Contributor
timestamp: June 15, 2024, 09:15:02 am
content: Quote from: aliarifat794 on June 15, 2024, 08:36:34 amAfter searching I find out that this type of stencil called "Direct heat stencil".
BGA fanout and soldering - Page 1
Forum section: electronics / beginners

author: ealex
author_rank: Frequent Contributor
timestamp: January 28, 2020, 07:39:30 am
content: HelloI'm trying to start my first project with a BGA package - a Cyclone iV EP4CE6F17C8 (i'll start another thread for the project - might be interesting for someone)The package used by that chip is FBGA-256: page 10, figure 6 fromhttps://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/an/an114.pdfIt looks like it's quite a big package - and I don't plan to use all the pins, but the more I can fan out, the better, as a prototype board(i'll try to use a 4 layer board)I've gather the following clips to help me with the layout:EEVblog #193EEVblog #1029Regarding soldering: will a hot-plate be enough for this ? I assume the BGA package will come pre-balled - i'll only have to re-flow it to the board:Can you recommend some other resources ?

author: kizmit99
author_rank: Regular Contributor
timestamp: January 28, 2020, 04:07:57 pm
content: I've used a variant of that same part (in the same package) and reflowed it successfully using a Controleo3 managed toaster oven. So, not a hot plate but probably something close to the same level of technology. I've done 2 boards with that chip and didn't have any issues getting it to soldered successfully.Just a data-point. Good luck.
BGA flux?  - Page 1
Forum section: electronics / beginners

author: u666sa
author_rank: Frequent Contributor
timestamp: September 14, 2023, 05:47:26 pm
content: I see often flux advertised as BGA, and in questions to products people asking if the flux can do BGA? Am I missing something? What's the difference between BGA flux and non BGA flux? Thus far I was able to use whatever flux I had to take off and put on BGA, and do reballs.
BGA removal - Page 1
Forum section: electronics / beginners

author: zerorisers
author_rank: Regular Contributor
timestamp: July 13, 2015, 05:12:53 pm
content: Hello everybody. I have recently purchased a hot air rework station from frys, but I must know. what would be the best way to preheat the board before attempting to use the hot air gun to remove the BGA device? IR or hot air? I will be doing all work in a small room that is about 8"x10" so heat up of the room itself is an issue as it is a bedroom. i have about a 2.5" x 1.5" space to work with.Thanks in advance, zerorisers.

author: John_ITIC
author_rank: Frequent Contributor
timestamp: July 13, 2015, 06:07:44 pm
content: "It depends" (on what size your BGA is and what your board size is).With a hot air station, you will most likely not be able to control the heating of your board/BGA properly, resulting in delaminated PCBs.I have one of these for the explicit purpose of desoldering/soldering BGAs in a prototype environment (same setup as in the picture):http://www.zeph.com/zt-7.htm

author: kripton2035
author_rank: Super Contributor
timestamp: July 13, 2015, 06:39:53 pm
content: I bought a yihua 853AA for this purposean ir plate under the board I heat to 200°C, and the hot air gun above the chip at 300-350°C depends on the size of the chipworks nice. the station paid itself already 6 times ...
BGA Rework Station - LY IR6500 v.2 - Page 1
Forum section: electronics / beginners

author: Johno
author_rank: Newbie
timestamp: April 15, 2020, 02:01:09 am
content: Hi everyone,New to the forum but I'm looking to perform BGA work (replacing or reballing chips like the RSX on the PS3 and similar on other consoles). I do have a hot air station for simple SMD work but it's not powerful enough for larger chips. In searching for a cheap solution as this is a hobby repair I am willing to spend a little bit of money on something that will "do the business" as Dave says but nothing too expensive (<$1K).I found this unitAliExpress Solder Station LY IR6500 V.2but I'd like to see if anyone else has bought this type of unit and their experience with it (and/or the seller). Is the CCD module worth it as well? As far as I can tell it doesn't show the solder ball alignment and just shows the solder balls on the edge of the chip.What else should I look out for? Is there anything cheaper than can do the same thing using IR.I have searched quite a bit on Google (unless I've missed something) and there are only a couple of hits on the EEVBlog forum from a couple years ago but one of the questions seems to be relating to power (120vac vs 240vac) and the other was quite dated but the user went with a different brand/model.
BGA soldering excercises - Page 1
Forum section: electronics / beginners

author: lacek
author_rank: Regular Contributor
timestamp: June 23, 2017, 01:38:18 pm
content: Dear AllI would like to teach myself microsoldering of BGA chips. I have never ever done it - though I feel confident in soldering of ordinary SMD components down to 0402.Could I ask for some recommendations how to train the hand to solder the tiny BGA components? I have come up with the following challenge: take my old smartphone (e.g some old Nokia), remove some components, clear all solder with wick, reball and resolder, see if it still works.Would you have some better recommendations? I want to avoid buying in general ICs just so that I practice mounting them.

author: rstofer
author_rank: Super Contributor
timestamp: June 23, 2017, 06:41:32 pm
content: You could Google for 'soldering BGA' and get over 500,000 hits.You will probably need either a hot air gun or a reflow oven.
BGA soldering pads - how do you repair them? - Page 1
Forum section: electronics / beginners

author: Jane
author_rank: Frequent Contributor
timestamp: June 29, 2016, 11:50:41 am
content: Does anyone have any experience with damaged BGA soldering pads?I mean the soldering pads on PCB.I would guess that a thin( but how much thin ??) copper wire and a glue( but which one is the best) could help.I desoldered CPU that has about 1000 pads and one pad was damaged( it is 1.2V core voltage).I noticed that there are more pads with the same core voltage. Must be all 1.2V soldered or it is not so critical if one is not soldered?Not sure if all 1.2V must be present.

author: Rerouter
author_rank: Super Contributor
timestamp: June 29, 2016, 12:00:06 pm
content: in almost all cases yes all pins are required, playing with 1000 pin BGA's is already a hard task,What i will say is however you do it, your going to keep the added thickness extremly low or you will cause the BGA to not sit as flush as it should,The other point is making sure if surface tension tugs your fix (at high temperatures) that it wont short out on nearby pads,

author: cowana
author_rank: Frequent Contributor
timestamp: June 29, 2016, 12:18:03 pm
content: Quote from: Rerouter on June 29, 2016, 12:00:06 pmWith my experience of BGAs, this isn't the case. When the core draws a high amount of power (say 10A at 1.1v for an FPGA), a lot of pins are used to keep the voltage drop low. These will internally be connected to a plane inside the BGA - so if one of them is missing, it won't cause any issues.The device is likely to have multiple rails of the same voltage in addition to the main core supply (eg a rail for each clock, PLL, tranceiver etc), so there's no guarantee a specific pin isn't dedicated (and thus required) for one of them - but in my experience, in the majority of cases (75?%) one out of several hundred power pins could be disconnected without too much of a problem.
Bias network for Common Emitter: why RB? - Page 1
Forum section: electronics / beginners

author: jimmyWalton
author_rank: Newbie
timestamp: November 04, 2024, 08:45:30 pm
content: Hello!I hope that this is the right section for my question.In Microelectronic Circuits by Sedra, Smith (7th ed., 2015) in Section 7.4 some bias circuits for the Common Emitter amplifier are presented.Thishttps://crcit.net/c/b40b7edbe9e044d78a1b5b046fa77544is the first one. And this is an alternative representation of the same circuit, where the couple R1 and R2 has been replaced with its Thèvenin equivalent RBB = R1 || R2 and also the power supply of its branch is the Thèvenin equivalent.https://crcit.net/c/22a82f9756d0403d8c7de6e53ce52144Then, another bias circuit is presented with two symmetrical power supplies, a positive one and a negative one:https://crcit.net/c/e20fa220b49d439d8844a89c54a239fbThere is no substantial difference in the formulae.It is stated that, if the transistor is used with the base grounded (for example in the Common Base configuration), RB is not necessary, and this is acceptable.However, it is also stated that, if the input signal must be coupled to the base (as in the Common Emitter configuration), then RB is needed.Why? I can not understand, and in the subsequent pages there seem not to be some more observations about this. Why is that RB necessary? Note that, while RE is connected to the negative power supply, RB is connected to ground (even if both are grounded when considering the small signal equivalent circuit).

author: PGPG
author_rank: Frequent Contributor
timestamp: November 04, 2024, 11:18:04 pm
content: Quote from: jimmyWalton on November 04, 2024, 08:45:30 pmHere I understand RB being not needed meaning RB is shorted.Quote from: jimmyWalton on November 04, 2024, 08:45:30 pmIf you short base to GND (RB not needed) than coupling input signal to base would mean coupling it to GND.
Bias power  requirement of TNY287 Flyback SMPS controller - Page 1
Forum section: electronics / beginners

author: ocset
author_rank: Super Contributor
timestamp: September 20, 2018, 09:12:23 am
content: Hi,We are using the TNY287 for a offline isolated Flyback SMPS (10W), and we are powering the TNY287 from a bias winding. (schem attached)Page 6 of the datasheet says we must supply 1mA to the TNY287, however page 12 says that the TNY287 requires 550uA.Page 15 of the datasheet states that if TNY287 us supplied with over 4mA , then it will shut down.Please advise if the TNY287 requires 550uA or 1mA?We need to know, because when our secondary is light loaded, our bias coil collapses from 24V down to 14V.........we want to set the feed resistor (R18) to as low value as possible (feed resistor is the resistor that feeds the BP/M pin from the bias coil) so as to reduce dropout of the bias coil in light load as much as possible.If the 550uA figure applies, then we can set the feed resistor to 11k, but if the 1mA figure applies, then we must set the feed resistor to 6k2.If we set the feed resistor to 6k2, then when the secondary is loaded, and the bias coil thence goes up to 24V, then we are feeding the TNY287 perilously close to the 4mA maximum.Please advise the actual bias current draw of the TNY287.TNY287 datasheet:https://ac-dc.power.com/sites/default/files/product-docs/tinyswitch-4_family_datasheet.pdf

author: capt bullshot
author_rank: Super Contributor
timestamp: September 20, 2018, 09:30:51 am
content: Just read the fine datasheet:They state: If you supply enough current (1mA recommended) into that pin, you reduce the devices power dissipation by disabling the HV regulator. The same pin is used for e.g. OVP to shut down the chip in case of feedback loop failure at some higher current threshold (4mA). So one might think, if you supply less current, it either may simply take away part of the power dissipation, or cause some wrecking and havoc - whatever, I can't answer this.So it's up to your engineering skills to find a suitable resistor or add more more components to achieve your goals.
Bias resistor in TIA configuration - Page 1
Forum section: electronics / beginners

author: nihial
author_rank: Regular Contributor
timestamp: March 01, 2025, 05:58:31 pm
content: Hi,I sometime see a resistor in series with the photodiode in TIA configuration.However I don't understand its purpose and I didn't really find an explanation.Anyone fort a short answer and a link to a long answer?Best regards

author: BillyO
author_rank: Super Contributor
timestamp: March 01, 2025, 06:54:59 pm
content: I've never seen this myself. Do you have a link to an example?The only thing I can think of is current limiting.

author: nihial
author_rank: Regular Contributor
timestamp: March 01, 2025, 07:56:49 pm
content: For example inhttps://www.analog.com/en/resources/technical-articles/how-to-effectively-design-and-optimize-tia-interfaces-of-lidar-systems.htmlI don't talk about the resistor with the capacitor for ac coupling but the one even present in DC coupling configuration

author: Gyro
author_rank: Super Contributor
timestamp: March 01, 2025, 08:05:47 pm
content: That one is for current limiting, note the '-HV', avalanche detector diodes work at much higher voltage than the opamp supply rails.
Bidirectional buffer TXB0108PWR - Page 1
Forum section: electronics / beginners

author: rakeshm55
author_rank: Regular Contributor
timestamp: May 20, 2014, 06:46:12 am
content: Hi,Recently i came across this bufferTXB0108PWR (linkhttp://www.ti.com/lit/ds/symlink/txb0108.pdf).....How is it possible for a buffer to act as a Bi directional buffer without direction control.....Wont there we a conflict i mean data contention.... What will happen if both the sides are driving the buffer??..... Is the output of buffer a weak drive (in uAs) then wont the rise times be slow....But the absolute maximum Io is shown as 50mA...Can it used for driving back blanes (inter board connection) where in the kine capacitance will be high.......Please help me understand.....RegardsRakesh M.

author: Monkeh
author_rank: Super Contributor
timestamp: May 20, 2014, 06:50:21 am
content: I think the datasheet explains it pretty well.

author: David_AVD
author_rank: Super Contributor
timestamp: May 20, 2014, 07:00:51 am
content: That's a neat little chip. The direction seems to be per-pin (unless I read it wrong), so could also be used for connecting a 3.3V micro to 5V RS485 transceivers, etc.