hybridfree/eevblog-posts huggingface dataset:
Tutorial on the Input Filter Design - Page 1
Forum section: electronics / beginners

author: rbola35618
author_rank: Frequent Contributor
timestamp: June 08, 2018, 01:48:18 am
content: Hi EEVBLOGGERsIt has been a while since I have posted a tutorial on the forum. I notice there are several power supply questions from our younger engineer. I hope this will be useful to people.Robert Bolanos
Tutorial Video, Forward Converter Part 1,2,3,4,5 - Page 1
Forum section: electronics / beginners

author: rbola35618
author_rank: Frequent Contributor
timestamp: December 26, 2014, 07:10:05 pm
content: Here is a tutorial on how to analyze a two switch forward converter and how to simulate it using SPICE.Video1: Analysis of a Buck converter.Video2: Analysis of a forward converter.Video 3 Analysis and simulation of the output inductor for forward converter.Video 4 Forward Converter: An analysis of how the capacitor's ESR effects the ripple voltage.https://www.youtube.com/watch?v=22rzr9j1D1Q&feature=youtu.beWill be adding more videos as time permit.Questions or comments can be sent to rbola35618@aol.comRobert

author: planet12
author_rank: Regular Contributor
timestamp: December 26, 2014, 10:57:02 pm
content: subscribers = subscribers + 1Thanks Robert - just watched some of your flyback videos and quite enjoyed them too.

author: rbola35618
author_rank: Frequent Contributor
timestamp: December 30, 2014, 12:26:29 am
content: Video 4 Forward Converter: An analysis of how the capacitor's ESR effects the ripple voltage.https://www.youtube.com/watch?v=22rzr9j1D1Q&feature=youtu.be

author: rbola35618
author_rank: Frequent Contributor
timestamp: January 01, 2015, 02:49:11 am
content: In this tutorial, I show how to damp the output filter so that you don't get ringing when powering up the supply. I also show the effects of operating in Discontinuous Current Mode (DCM) and show how the supply will peak detect when in DCM. In peak detecting, the output voltage of the supply will ramp up and possibly damage any sensitive loads that the supply may be connected?Forward Converter Part 5·
Tutorial Video, Frequency response of a Common Drain and Common Source - Page 1
Forum section: electronics / beginners

author: rbola35618
author_rank: Frequent Contributor
timestamp: July 01, 2014, 03:16:18 pm
content: This videos show how to calculate the frequency response of a common Drain and a common Source. I used a technique called the Open Time Contant (OTC). The advantage in this technique is that it is more intuitive that deriving the transfer function of the circuit. By finding the time constant of each capacitor, it give insight into which capacitor is slowing the circuit down. It is a powerful technique in analyzing circuits. I then use SPICE to verify my hand calculations.Comments and Question are welcomed at rbola35618@aol.com Request for the SPICE file can also be sent to my email mention above.Frequency Response of a Common DrainFrequency Response of a Common Source
Tutorial video, gain/phase of a flyback using a function generator and scope - Page 1
Forum section: electronics / beginners

author: rbola35618
author_rank: Frequent Contributor
timestamp: June 15, 2013, 05:30:23 am
content: Poor man's frequency response analyzer(Gain and Phase measurement of a flyback supply)This video is a follow up to a previous video where I used a Venable Frequency Response Analyzer (FRA). Most FRA are out of the budget of most small business or hobbyist. However, you can use a function generator, an injection transformer, and a scope to measure the stability of a power supply such as a flyback.This video shows you step by step in setting up a function generator, an injection transformer, and a scope to measure the gain and phase of a flyback. By injecting a signal and measuring the amplitude and the phase delay, you can measure three critical power supply specifications such as the crossover frequency, phase margin, and gain margin.
Tutorial Video on Loop compensation and Simulation of a Flyback Part 2 - Page 1
Forum section: electronics / beginners

author: rbola35618
author_rank: Frequent Contributor
timestamp: December 02, 2012, 06:13:30 pm
content: In this video, I verify the AC model (Jack's model) against a switching model (Basso's Model)Please excuse the audio noise. I am triying to get a better microphone or perphaps filter out the noiseQuestions and comments are welcomed.I hope you find the videos useful.Robert
Tutorial Videos: Small Signal analysis of MOSFET - Page 1
Forum section: electronics / beginners

author: rbola35618
author_rank: Frequent Contributor
timestamp: April 08, 2013, 08:09:03 pm
content: For those who are interested in how to perform small signal analysis on Mosfet. Videos based on the Sedra Smith book. Originally recorded to help my son in his EE circuit class.Deriving impedanceGain of a Common SourceGain of a Common DrainGain of a Common Gate
TV Died, Am I capable of fixing it? - Page 1
Forum section: electronics / beginners

author: Amblydoper
author_rank: Newbie
timestamp: June 13, 2013, 08:06:59 am
content: I have an older LG TV that has served me well, but it died today after 2 days of operating in the hot weather. Cooler now, its still dead, so it must not just be the heat.The Back light works fine, displaying a nice life-less dark grey. The thing tuns on and off from the remote, although these steps take 3 times as long as normal. Just before it failed, the display occaisionally cycled to 50% grey, for a second, then back to a normal picture for 10-15 seconds, before it flashed/cycled again to grey. So I think the display is perfectly fine too.Knowing just a little about electronics from the EEVblog videos, I'd bet dollars to donuts that there are some blown caps in there, and that replacing them will bring my TV back. But I've never touched a soldering iron and I don't own a meter. Am I foolish to attempt a repair on this? Is this something I can do, or will I fry myself? I don't care if I fry the TV, I'd just rather NOT replace it if I don't have to.

author: Stonent
author_rank: Super Contributor
timestamp: June 13, 2013, 09:00:19 am
content: I'm not completely sure, but I think Dave may have made a video once of him repairing an LCD with some caps.Bad caps or blown MOSFETs are what ends up being the problem on a lot of LCD screens.

author: ttp
author_rank: Regular Contributor
timestamp: June 13, 2013, 10:13:08 am
content: Some electrolytic caps can give you a nasty bite, make sure you short them before you touch them.

author: ptricks
author_rank: Frequent Contributor
timestamp: June 13, 2013, 10:27:23 am
content: If you have never used a soldering iron it might be an expensive way to learn. If you are just going to discard the TV then give it a try, nothing to lose.

author: amyk
author_rank: Super Contributor
timestamp: June 13, 2013, 11:00:45 am
content: Post the model number and good pictures of the boards inside, we might be able to tell you what to check. As you mention a backlight I assume this is an LCD, which is going to be a little better for the beginner as the only high voltages are in the inverters/CCFLs/PSU unlike a plasma.

author: alanb
author_rank: Frequent Contributor
timestamp: June 13, 2013, 01:09:38 pm
content: If you are interested in electronics and want to learn its worth investing in the basic tools (Soldering station and meter) and giving it a try. If your not going to pursue electronics as a hobby then you are probably better off spending your money on a new TV.
TV in the bedrom - Page 1
Forum section: electronics / beginners

author: jarleiceman
author_rank: Contributor
timestamp: December 11, 2013, 08:06:59 pm
content: HeiI have a problem, I have an ALTIBOX PRV, ALTIBOX ROUTER, PHILIPS TV 55" (2013) 3D...and then I have a Philips TV in my bedroom...I want to whatch TV in my bedroom,but I dont't want to use Wireless system...too expensive...I know I can use a "splitter" from the ALTIBOX PVR (HDMI)and just turn off my TV in the livingroom......But here is the kick: I want too use a cable With a RC-reciver in the bedroom so I can change channel on the ALTIBOX PVR-Box in bed.So, where do I conect this cable in the ALTIBOX PVR-Box...? Can I just parallell-couple it on the Box RC-reciver-diode...and where can I get this kind of cable...?I know I can use my Android too use on my TV...but not on the ALTIBOX PVR-Box...From the man in the Northjarleiceman
TV IR Remote controls what are some fun experiments to do with them ??? - Page 1
Forum section: electronics / beginners

author: lordvader88
author_rank: Frequent Contributor
timestamp: September 23, 2017, 10:37:17 pm
content: I've never hocked 1 up to anything or an Oscope, and how do they work ?An IR LED flashes near 30-40-50kHzWhen did they start using them as a standby pwr switch on, and back at the beginningAn LED pulses a sqr. wave binary , how does the TV compare that to some internal saved binary code ? Was it 4000 and 74 logic stuff to save a short "program "(incomplete sentence/though)It's fascinating the way all that started out, but I don't know how they did it with mechanical systems, and then whent electriacal logicI must learn more,What are some fun TV remote projets ?

author: rstofer
author_rank: Super Contributor
timestamp: September 23, 2017, 10:43:54 pm
content: http://www.righto.com/2010/03/understanding-sony-ir-remote-codes-lirc.html
TV faulty power board  - Page 1
Forum section: electronics / beginners

author: altanok
author_rank: Newbie
timestamp: February 14, 2022, 06:18:32 pm
content: helloi have panasonic plasma Tx-p42gt60e (p-plasma 42-screen in inch , gt-higher class 60-year of made E-sell for europe) with faulty power board (90% sure). tv wont turn on and there is no stand by red light. there is no 5V on stand by. when i checked conector from power board to main board there in no Voltage at any pin. Visual check - OK , Fuses - OK ,condensators are visualy OK. Do you guys have any idea that might help or what to check ? i have servise manual for almost the same TV but country for use doesnt match ( mine is E- europe and manual is B / Y not quite sure what is different)
TVS diode for IC 5V protection - Page 1
Forum section: electronics / beginners

author: aless2056
author_rank: Contributor
timestamp: October 09, 2022, 08:53:08 pm
content: Hello, guys I have a very simple circuit with a PIC16F628 connected directly to a digital potentiometer MAX5389. All powered by a 5V source through an LM7805.Initially, I had a problem with the Max5386, which returned the resistance to the initial position, after I put a 100nF capacitor between Vcc and the IC's gnd, the problem resolved. But now after a few days on, the Max5389 always burns, I believe it is some transient in the power supply.Can putting a TVS diode on can prevent this from happening?Which TVS diode would be indicated?

author: JustMeHere
author_rank: Frequent Contributor
timestamp: October 09, 2022, 10:57:21 pm
content: Probably drawing too much current through your chip. Depending on the exact version. 2.5mA to 500nA is going to be your max safe current draw.

author: aless2056
author_rank: Contributor
timestamp: October 10, 2022, 01:15:13 am
content: What would be the TVS Diode options to protect the MAX5389 when it is powered by a 5V source?

author: hubi
author_rank: Regular Contributor
timestamp: October 10, 2022, 01:53:42 am
content: Can you post a schematic of your simple circuit?JustMeHere's explanation for the chip failure seems more likely than transients.
TVS Diode for Surge Protector  - Page 1
Forum section: electronics / beginners

author: Wookie555
author_rank: Newbie
timestamp: August 30, 2019, 01:01:36 pm
content: I'm looking at making a DIN mounted surge protector for 240VAC and I found a TVS diode that seems to fit the bill.Specifically, PTVS10-380C-TH which is rated for 10kA @ 8/20 μs with a Repetitive Standoff Voltage of 380V.It costs $139 which is only slightly higher than a comparable MOV based unit.The fact that there aren't existing commercially available TVS suppressors units available in this power range makes me a little nervous, especially when it seems so clear cut.Is this feasible?And should I be running an MOV in parallel?

author: David Hess
author_rank: Super Contributor
timestamp: August 30, 2019, 04:18:06 pm
content: It is feasible but for a given capacity, a TVS is more expensive than a MOV simply due to their construction differences and materials and I think this explains the difference in popularity. The TVS has the advantage of not wearing out with repeated use while MOVs silently stop, um, MOVing.Before MOVs became popular, they used to make some really big TVS devices.I would not put a MOV in parallel but I might put a GDT in parallel.

author: MarkF
author_rank: Super Contributor
timestamp: August 31, 2019, 12:27:22 am
content: TheBourns Hybrid GMOV Componentsalso look promising.

author: Wookie555
author_rank: Newbie
timestamp: August 31, 2019, 08:13:15 am
content: QuoteThis makes sense for residential installations, but there are plenty of corporate customers willing to pay more for extra reliability.It's strange that I can't find *any* DIN modules using TVS diodes even when the parts are commercially available.

author: Wookie555
author_rank: Newbie
timestamp: August 31, 2019, 08:15:25 am
content: QuoteWould I get the same result if I put a GDT in series with an existing MOV based unit?
TVS diode - Page 1
Forum section: electronics / beginners

author: Vcky_electro
author_rank: Contributor
timestamp: May 21, 2019, 03:29:19 pm
content: Hi,Im using two Type-C connector in my board. ONe is for data + power and another one is for only power. Do i use TVS diode for both connector ? or one TVS diode is enough for both connector.(Note: Both connector power is Vbus=5V)Please let me know if anyone knew..Thanks,Vicky.

author: piguy101
author_rank: Regular Contributor
timestamp: May 23, 2019, 01:21:21 am
content: Not exactly sure what you are talking about, but it is often good practice to include a TVS diode on every single signal wire (and power wire) coming into a device when transients are possible. You never know which pin could have a nasty spike on it for some reason.

author: Lt_Flash
author_rank: Regular Contributor
timestamp: May 24, 2019, 06:17:00 am
content: Quote from: Vcky_electro on May 21, 2019, 03:29:19 pmYou put one TVS diode per each line. Usually there are TVS diodes in a pack for USB - they have 2 TVS diodes and 1 Zener diode, for example - prtr5v0u2x. This one has a Zener diode to clamp voltage and two TVS diodes for anti-static protection. If you're using something like uni-directional TVS diode Vishay SMP13A-M3/84A - you put each of them on protected line. If you're using multiple connectors - you put one TVS pack for each connector, see example here:https://static5.arrow.com/pdfs/2014/6/5/0/43/53/634/mcp_/manual/328evb-usb2514b-fs_a12020evaluation20board20schematic20pdf.pdf
tvs diodes - Page 1
Forum section: electronics / beginners

author: peterthenovice
author_rank: Regular Contributor
timestamp: November 11, 2015, 02:16:41 am
content: hiwhat clamping voltage do i need for tvs diodes/esd protection to protect a atmega32u4 being used as an adapter for atari/commodore 64 joysticks.should it be 5v?http://www.instructables.com/id/Classic-Joystick-to-USB-Adaptor/?ALLSTEPS

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 11, 2015, 01:01:34 pm
content: BAT54S, wired from GND (anode) to connector pin (middle) to VCC (cathode), is probably the simplest. Use a 1k resistor from connector pin back to MCU pin.I don't see a schematic so I don't know how specific this is.Tim

author: SeanB
author_rank: Super Contributor
timestamp: November 11, 2015, 06:12:24 pm
content: You wil be using a 1k pull up resistor for the joystick, so a 10n ceramic capacitor from the input to ground, the BAT54s across the capacitor and a 10k series resistor from there to the MCU input pin will do the job. Pull up resistor limits current into Vcc and the diode catches negative pulses, while the 10k series resistor ( can be really anything from 10k to 100k) limits current into the MCU diodes. put a 6V8 transient absorber across the Vcc rail to the MCU and it will survive well, Not going to survive mains, but will handle the body model transients well enough and cheaply.
Tweaking a solenoid driver - Page 1
Forum section: electronics / beginners

author: GardG
author_rank: Newbie
timestamp: March 29, 2021, 09:18:17 pm
content: Hi all,I'm building a driver for a linear solenoid - the intention is basically to make it possible to use a slightly over-spec supply voltage to make it knock as hard as possible, then have the voltage drop off to a reasonable holding voltage as quickly as possible. I'm almost there, I've just got some questions related to tweaking it.I've based my circuit off the information found inthisexcellent write-up. I've built "version 1" of the circuit, which works as expected (it's just a cap and a resistor in parallel after the solenoid), and I'm now building "version 2", which uses a PNP to short out the cap when voltage is removed, so that it's empty and immediately ready for another cycle, without having to wait for it to discharge. My circuit is just like the schematic on the above page, which is this:With the following differences:- The solenoid isthis one(7R resistance)- R2 is 7.5R- Diodes are 1N5400- Q5 is TIP42A- For testing, I'm using a pushbutton instead of Q1My issue is that when power is disconnected, the Base-Emitter voltage of Q2 doesn't go low enough to turn it on and short the cap. Of course, part of the problem is that I'm using a transistor with a too high VBE(on) compared to the one in the original schematic - but looking at the Base-Emitter voltage on the scope, it doesn't really seem to go much below -0.7V, which wouldn't be enough even if I had the suggested transistor, which needs -1V.I've adjusted the R4 and R5 values, but it doesn't make much of a difference. If I just use jumpers instead of R4 and R5, I do in fact (sometimes) get a low enough voltage to turn Q2 on, but this makes the whole circuit unreliable and is clearly not a good idea. Other resistor values (5R-33R) don't seem to make much of a difference, I still can't quite reach -1V, I just get more noise with lower resistance. Best I could do was -779mV, as per the attached scope shot.So - I'll get the proper transistors, but apparently I need to do something else as well to make it work reliably. Any clues on what to adjust? Is there simply not enough energy stored in the solenoid to get sufficient flyback to turn Q2 on?

author: Manul
author_rank: Super Contributor
timestamp: March 29, 2021, 09:40:01 pm
content: BJT transitor base is current driven, not voltage. You basically do not care about the exact voltage, you care how much current is going. BE junction is like a diode. It has a forward voltage drop. Until it reaches that - almost no current flows. When it reaches that, the current suddenly appears and if you increase current, the voltage changes very little.
Twin-t notch filter transfer function - Page 1
Forum section: electronics / beginners

author: miketan3904
author_rank: Contributor
timestamp: June 11, 2020, 08:51:46 pm
content: Hi. I am referring to this document:https://www.analog.com/media/en/training-seminars/tutorials/MT-225.pdfI was trying to derive the transfer function given in the document but failed.I have attached the schematic diagram with node labeling and the equation that i wrote at node Vx, Vy and the non-inverting input of U4. I substitute the first and second equation into the third equation but the transfer function that i get (fourth equation) is different from the document.I would appreciate if someone can point out my mistake. Thank you!

author: RoGeorge
author_rank: Super Contributor
timestamp: June 11, 2020, 08:59:00 pm
content: Last time you posted herehttps://www.eevblog.com/forum/beginners/input-impedance-of-twin-t-notch-filter/and abandoned the subject.To see if there are any answers to your own posts, click the "Show new replies to your posts." link shown in the upper left of any page in this forum, the link on the right of your avatar picture, under your own username.

author: Benta
author_rank: Super Contributor
timestamp: June 11, 2020, 09:43:55 pm
content: From what I can see, no mistake. I'm sure you're in a position to work this out. Cut 'n paste doesn't do it.
twin wave phase shift output loss formula - Page 1
Forum section: electronics / beginners

author: Quantumplate
author_rank: Regular Contributor
timestamp: March 22, 2022, 03:14:06 pm
content: Is there a formula for this anywhere? What I mean by the subject line is when you add 2 waves of the same frequency and amplitude together, but vary the phase. Obviously when in phase the resultant output is doubled, and when 180deg out of phase there is no resultant at all. I can see using circle vectors that at 120 deg phase shift, then the combined output is the same amplitude as each of the two input waves.Feeling stupid I can't find the formula online!

author: Terry Bites
author_rank: Super Contributor
timestamp: March 22, 2022, 06:44:17 pm
content: Lay back and watch this

author: Quantumplate
author_rank: Regular Contributor
timestamp: March 23, 2022, 03:47:49 pm
content: Great thanks for the link.So the factor is 2Acos(phi/2) for anyone seeking the nitty gritty.

author: CaptDon
author_rank: Super Contributor
timestamp: March 24, 2022, 02:03:44 pm
content: Using the simplified formula posted by Quantumplate can someone post the step by step math for the following two waves, and would this exactly predict the output voltage/power of for instance an R.F. power combiner. Just for reference let's say it is the standard where every port is 50 ohms. So for my inputs, the waves are the same identical pure sinewave frequency but different in phase. Wave one is 1vpp and is the zero degree reference, wave 2 is 2vpp and lags behind wave 1 by 45 degrees. Can you show the step by step math? Thanks!! (I find this interesting because many years ago RCA had an A.M. broadcast band transmitting system where two 25KW transmitters were combined and by the use of phase shift produced a typical A.M. broadcast signal. RCA called it AmpliPhase and I have the brochures. I never worked on one but they were miserably hated by broadcast engineers apparently due to power combiner fires and blowouts. The system could not produce the 110% forward / 99% backward modulation of today's PWM modulated transmitters and the RCA system was often called Ampli-Fuzz by those who worked on it.) Thanks all!!!
Two 24V PSUs in series + tap in the middle - Page 1
Forum section: electronics / beginners

author: TeraHz
author_rank: Contributor
timestamp: July 19, 2012, 04:27:05 am
content: Hi there,I have a couple of 24V 6.5A switch mode PSUs (http://www.circuitspecialists.com/products/pdf/CSI-15024-1M.pdf) and I'd like to put them in series to get a 48V output but I have two questions:The PSUs seem to have enough protection features (as per DS), should I add another set of diodes on the outputs?And the main question, is it possible to tap one of the PSUs to get 24V out as well or will that cause issues?The 48Vs will be loaded at 1.5A-2.2A and the 24V at 1.5A-1.75A.

author: Classicmacintosh
author_rank: Newbie
timestamp: July 19, 2012, 07:21:22 am
content: From my experimentation using a couple of old Toshiba laptop PSUs (15vDC at 3A), yes you can put them in series. I was using three in series (so producing 45vDC at 3A max) to blow up old PCI modems (not that I recommend using PSUs like this!) and tapped off the first PSU to run a 12v fan (at 15v) to remove the smoke.I used no external circuitry as the PSUs seemed to be incredibly well protected. As I do not know if your PSUs are as well protected, I would play it cautious and use diodes.If your PSUs are suitably protected, jut give it a shot as if they don't like it then the worst they can/will do is to go into protection mode.Good luck!-Ed

author: Psi
author_rank: Super Contributor
timestamp: July 19, 2012, 09:32:33 am
content: Just be careful that all of the power supplies are switched on before you apply a load.

author: TeraHz
author_rank: Contributor
timestamp: July 19, 2012, 02:27:40 pm
content: I've actually tried them in series before and they worked just fine for the 1-2hrs I had them that way. I was only concerned about taping the 24V as well.Psi, the supplies will be on pretty much 24/7, only the load will be turned on/off.Thanks

author: digsys
author_rank: Unknown
timestamp: July 19, 2012, 02:37:08 pm
content: This sort of thing is done all the time, so it's not scary. Maybe as a minimum extra protection, put fuses on the+48V Tap and one on the +24V Tap. That way if anything goes wrong with either load, you're covered.

author: ftransform
author_rank: Frequent Contributor
timestamp: July 29, 2012, 04:49:10 am
content: Some people recommend adding diodes in between the power supplies in case one fails to turn on or a short occurs.This website covers the issue briefly:http://power-topics.blogspot.com/2009/07/operating-power-supplies-in-series.html
Two BIOS chips on HP Envy x360 13-bf0013dx ipa32 la-m024p rev 1b?  - Page 1
Forum section: electronics / beginners

author: u666sa
author_rank: Frequent Contributor
timestamp: October 04, 2025, 09:41:25 am
content: No, I've definitely seen dual BIOS mobos from Gigabyte. But on laptop it's a brand new thing for me. Besides, these don't look to be DUAL bios. Chips are UC3 and UT3, one of the chips is taken off on photo. The one that is taken off has almost no data inside, there is some stuff but mostly it is empty. The other one is full of stuff and most likely the chip near keyboard connector is the BIOS. I'm lying, I've seen laptops with two BIOS chips, one for BIOS and one for VBIOS, and this laptop does not have a discreet GPU. So I have no clue.

author: RoGeorge
author_rank: Super Contributor
timestamp: October 04, 2025, 10:14:44 am
content: If they were to be dual BIOS, I would expect the two memory chips to be close to each other, not diagonally across the PCB. The second memory must be for something else. Combined with the much shorter content you found in the second flash, that's not a dual BIOS, it's for something else.Try to find a service manual with the schematic, or maybe follow the programming pins traces to discover which chip is making use of the second memory.

author: u666sa
author_rank: Frequent Contributor
timestamp: October 05, 2025, 12:36:24 am
content: One near keyboard connector is the actual BIOS, the other one near touch connector is type-c bios, also called thunderbolt bios.
Two-cell Charging - Page 1
Forum section: electronics / beginners

author: Tin Duc Vo
author_rank: Contributor
timestamp: May 02, 2014, 04:13:55 pm
content: Does anyone know if it's okay to just charge both cells instead of balance charging? I don't know how to look up a two-cell balance charging IC for my 7.4V pack. I want to charge in circuit and it's just an rc battery. I can tap the 3 points for charging.

author: retrolefty
author_rank: Super Contributor
timestamp: May 02, 2014, 04:56:18 pm
content: Quote from: Tin Duc Vo on May 02, 2014, 04:13:55 pmUsing a so called 'balanced charger' will actively ensure that the two cells are equalized as well as charged charged up. Commercially built and sold 2-cell li batteries are made with cells closely matched to try and keep them close to being matched over their life even if not using a 'balanced charger', however it would be good for you to check periodically that the mid cell tap voltage is at 50% of the two cell output voltage.For high performance, high current discharge packs I would say using a proper balance charger is a requirement for best results, safety, pack lifespan, etc.
Multiple camera controller - Page 1
Forum section: electronics / beginners

author: Thane of Cawdor
author_rank: Regular Contributor
timestamp: April 02, 2020, 10:10:38 am
content: Hi,I understand that I could potentially do this with a embedded computer which has multiple camera inputs but wanted to find out if there's a lower power/footprint way to go ahead with this.Are there any video controller ICs or off-the-shelf ICs available which could do something like this - if so, where would you start (I know it probably wouldn't be trivial)?Thanks

author: magic
author_rank: Super Contributor
timestamp: April 02, 2020, 06:19:21 pm
content: The screenshot they show has the video streams in separate windows, so it could be as simple as a USB hub with three cameras hooked up to it.What you are trying to achieve isn't easy, you essentially do need an embedded computer to drive both cameras, perform the image processing and pretend to be a camera to another USB host. You can't simply "combine USB signals" from multiple devices. Pretty surely the "computer" could be reduced to a single ARM SoC, however.The CCTV market may have some off the shelf solutions, but I'm not familiar with that stuff.

author: magic
author_rank: Super Contributor
timestamp: April 03, 2020, 07:27:58 pm
content: Actually, I think there are datasheets for some camera sensors which more or less describe how to talk to the sensor. But that's just my vague recollection, all I have ever cared about in sensor datasheets was learning the pixel size of some off-the-shelf camera modulesI think I have also seen camera modules on auction sites with interfaces other than USB. I think there are actually some more or less "industry standard" interfaces. IIRC some popular board like RasPi was supposed to have one. Maybe somebody else can help.Then you still need some USB (presumably 2.0) interface to connect to the host. That's not something you are going to bitbang with an Arduino. And firmware for that interface too. Say hello to USB and USB Video Class specs unless you find some ready to go sample code or Linux "gadget" driver.
Two contactors wired as changeover switch - Page 1
Forum section: electronics / beginners

author: V_King
author_rank: Regular Contributor
timestamp: February 26, 2019, 07:48:40 am
content: Hello,I'm a bit lost with contactors and their variety.I have a small solar setup. The solar charger has a programmable load output of battery voltage, which I want to use as a power for a changeover switch. When the batteries are in good charge state, I want mains power to be powered from the batteries>inverter>AC. But when the batteries discharge would reach pre-set voltage level, the load output from solar charger goes off and I want a changeover switch to swap into mains power.The batteries nominal is 24V, the mains is 240V / 16A AC. Is there a simple way to wire two contactors as a changeover switch, with 24v dc control? When I google for contactor wirings, it leads me to industrial applications, with way too much details for my head.Any advice much appreciated.Thanks

author: Ian.M
author_rank: Super Contributor
timestamp: February 26, 2019, 11:22:42 am
content: While its theoretically possible to wire two contactors, interlocked via their auxiliary contacts, as a mains changeover switch, its doubtful that it would be possible to do so legally under the UK wiring regs.If this is a fixed installation, you need a commercially availale automatic transfer switch and a licenced electrician to install it.

author: sokoloff
author_rank: Super Contributor
timestamp: February 26, 2019, 11:38:03 am
content: If this is a consumption device (given the low power, I assume it is), I see two approaches:1. A simple DPDT relay with break-before-make guarantee by spec.2. A mains to DC convertor to feed the DC stage before the inverter. At high solar output, you could turn this off, but that only gives you a modest reduction in losses.1 is way more efficient, 2 is simpler to reason about enough to get to a conclusion of “yeah, that’s safe”. 2 is probably also more durable in terms of likely to keep working for a decade without screwing with it.If this is a production device (in either sense, meaning not a lab project or intended to feed the mains distribution), I would not feel comfortable at all fiddling with it.

author: V_King
author_rank: Regular Contributor
timestamp: February 27, 2019, 07:18:02 am
content: Thanks for the responses. Found the info elsewhere. The thread can be closed.
Two Dimensional EMF detector - Page 1
Forum section: electronics / beginners

author: BrentonS
author_rank: Newbie
timestamp: February 05, 2019, 04:42:37 am
content: Hi.I would like to build a device that creates a two-dimensional image of high voltage power lines by detecting the electromagnetic field.I have an idea how to achieve this, but i'm not sure if it is physically possible.The 50Hz EMF would be measured with a phased array grid of antenna elements, amplify/filter each element and convert to digital.Apply calculated delays and sum the elements to "scan" across and down. Display the data by equating signal strength at each point to a range of colours.Wavelength = speed of light / frequency = 299792km/s/ 50Hz= 5996kmIs there a lower frequency limit for phased arrays?As the wavelength of 50Hz is so large, i'm thinking the spacing of the elements would be impractical.http://www.rfcafe.com/references/electrical/ew-radar-handbook/images/img153.gifIf 50Hz is too low, would it be possible to use this method to detect harmonics within the 50Hz signal?
Two dimmable current sources on same trafo? - Page 1
Forum section: electronics / beginners

author: FriedMule
author_rank: Frequent Contributor
timestamp: May 04, 2020, 01:17:46 am
content: The idea is to have two current sources, working independent. Both are dimmable to adjust current to the loads, i.e. a LED.I have tried to simulate a circuit, looking somewhat like this drawing. But it looks like none of the varistors do dimm anything when two current sources are combined in same circuit.What is wrong? :-)

author: Manul
author_rank: Super Contributor
timestamp: May 04, 2020, 01:40:36 am
content: There is nothing wrong with idea. And I can not see nothing wrong with your posted schematic. What is function of 1K5 resistors, load? Anyway, should be a simulation problem. By the way, that is potentiometer (pot), not a varistor.

author: jackthomson43
author_rank: Contributor
timestamp: May 04, 2020, 05:01:07 am
content: I am wondering what's its purpose? Anyways circuit seems fine, strange its not working. You should try simulate & debug it in Proteus. OR check out theseFree Circuit Simulator.

author: FriedMule
author_rank: Frequent Contributor
timestamp: May 04, 2020, 11:45:38 am
content: The whole idea with this circuit and my "project" is to learn, to understand parallel vs series connected separate circuit, how to control LED / current and how they do ract to raising voltage. Simply just a journey out in the electronic universe:-)The 1k5 is a shunt resistor across the load allows the current to go to zero.I am somewhat concerned about it being a simulator error, because it do make me second guess my self and make me search for "the error" in hours, when nothing is wrong. I had the same "problem" while trying to understand a simple astabil multivibrator, I could simply not see the logic in how it could work at all, I could only conclude that the two LED's would glow constant or not at all. So to find out where I was wrong, did I simulate the contraption and to my surprise, did the circuit just glow constant!I did later find out that the reason for the circuit to work, is due to the imperfection of the resistors value. :-)

author: FriedMule
author_rank: Frequent Contributor
timestamp: May 04, 2020, 09:32:13 pm
content: Quote from: jackthomson43 on May 04, 2020, 05:01:07 amDon't you think that $5,795 is bit steep for a noob who are trying to learn about the most basic components?I could buy 4 complete labs at that price, that would fit my needs:-)https://www.labcenter.com/pricing/
Two isolated ground from a single ground terminal - Page 1
Forum section: electronics / beginners

author: Adhith
author_rank: Frequent Contributor
timestamp: March 06, 2018, 05:47:38 am
content: Hello everyone...I'm using a 4S 18650 battery pack and its BMS board in one of my project. I'm using a constant voltage buck boost converter to boost the voltage from 12v to 18v and then using a CC/CV buck converter to buck the voltage to the required voltage of 16.8 for the battery pack. The reason I'm using two of these modules is to due to the lack of availability of an appropriate CC/CV buck boost converter. Anyhow the thing works fine since i have tested it with led strips and works as expected.The problem starts when i hook the output of the CC/CV buck module to the P- of the BMS (battery management system) Since the ground terminal is common for the P- and CC/CV buck converter input (output ground of CV buck boost converter) and output. So its clear that the resistance for the constant current function is bypassed and thus the constant current function doesn't work.So what I'm looking for is a solution to separate these two grounds from each other. What might be the possible solution.. apart from replacing the entire modules since the project is almost completed and all wiring had done.I have attached the pic of the CC/CV buck module and the schematics of the thing which I'm trying to do belowany help would be appreciated...
Two knobs for a Dick Smith Oscilloscope Q-1280 - Page 1
Forum section: electronics / beginners

author: Hammer_651
author_rank: Newbie
timestamp: October 07, 2024, 03:31:20 am
content: Hi all. Would anyone know or have two knobs for a Dick Smith Oscilloscope as shown in the photos. The shaft is 5.96mm slotted, the rest of the photos are self explanatory.Thanks.Hammer.

author: neillnz
author_rank: Contributor
timestamp: October 07, 2024, 08:42:38 am
content: I think you are going to have to settle on something functional as opposed to finding a source for an identical knob.What you want to search for is a knob for a 6mm shaft with the style "fluted", "splined" or "puish on".If you are not too fussy it seems Jaycar have a few options.If you don't like any of the options out there then there is always 3D printing. I have not printed one before but people are 3D printing knobs for a splined shaft:https://www.thingiverse.com/thing:5757475

author: Ian.M
author_rank: Super Contributor
timestamp: October 07, 2024, 09:38:16 am
content: Its only got two of the big knobs:https://www.radiomuseum.org/r/dicksmithe_65mhz_single_channel_oscilloscope_q_1280.htmlso anything off-the-shelf of a similar style and diameter for a splined shaft, with a recessed base in black plastic with a white line would be fine.
Two op-amps in parallel - Page 1
Forum section: electronics / beginners

author: limata
author_rank: Contributor
timestamp: May 28, 2014, 04:26:49 pm
content: Check this sample circuit about two op-amps in parallel.http://www.intersil.com/content/dam/Intersil/documents/an11/an1111.pdfIn Figure 2, Resistors Rbm1and Rbm2were included inside the feedback loop. I don't quite understand how this can limit the offset current?Thanks.

author: madshaman
author_rank: Frequent Contributor
timestamp: May 28, 2014, 05:21:59 pm
content: The offset current they're talking about is due to the output of A and B not being *exactly* the same. Whenever there's a non-zero voltage differential current will flow according to ohm's law, so the resistors are limiting the current which flows between the two opamp outputs, that is Iab = (Va - Vb)/(Rbm1 + Rbm2).I hope that's what you were asking.

author: limata
author_rank: Contributor
timestamp: May 28, 2014, 06:15:09 pm
content: Thanks. That is what I was asking.Although in the sample circuit ( figure 2 in the linked pdf), those two resistors should be left out of the feedback loop, otherwise the op-amp output will not see these two resistors.
Two rail power supply with 7815 - Page 1
Forum section: electronics / beginners

author: TiTanerCZE
author_rank: Contributor
timestamp: September 24, 2017, 05:22:48 pm
content: Hi, I am trying to build simple two rail power supply, each channel max 15V 1A. I will use torid transformer with two ouputs, each with separed groud. I usually see similar circuit using 7815 for positive rail and 7915 for negative rail and transformer is with a center tap. Because each groud is seperd from the other i can use just 7815 and then connect them in series to get the "negative" rail?Thanks.

author: Dave
author_rank: Super Contributor
timestamp: September 24, 2017, 05:38:25 pm
content: Yes, you can do that.

author: Gyro
author_rank: Super Contributor
timestamp: September 24, 2017, 05:51:15 pm
content: It has always been the case that 78xx series regulators have been better behaved and more stable than 79xx, being less twitchy about decoupling. It's a sensible thing to do if you have two independent secondaries.

author: TiTanerCZE
author_rank: Contributor
timestamp: September 24, 2017, 05:59:51 pm
content: OKThanks for reply.

author: David Hess
author_rank: Super Contributor
timestamp: September 25, 2017, 03:29:10 am
content: Looks good to me and it is the preferred way to do it if you have two floating secondaries. As Gyro says, the 78xx is better behaved than the 79xx although I doubt the difference matters.Decoupling capacitors C7 and C14 are not required if the input capacitors are adjacent to the regulators. I would use small 10 to 100 microfarad aluminum electrolytics (or 1 to 10 microfarad solid tantalums) for C6 and C8 instead of small ceramic capacitors; high frequency decoupling needs to be located close to the load rather than the source and a low value low ESR ceramic or film capacitor is more likely to cause problems.
Is it safe to use the output of two LED-drivers in series as a +/-72V DC source? - Page 1
Forum section: electronics / beginners

author: RoGeorge
author_rank: Super Contributor
timestamp: October 08, 2022, 09:08:22 am
content: The plan is to get a dual DC voltage source, with +72V GND -72V for a load of only 10...20mA using two LED drivers like the ones in the pics.There seems to be an output transformer with an isolated secondary for output, but there is no optocoupler on the PCB. Has Y capacitor between mains and DC output. The Y capacitors and the powering-up might be troublesome when the output of two SMPS are tied in series.- Are the usual COTS LED drivers galvanically isolated from mains?- Would it be OK to tie the output of two drivers in series?

author: ledtester
author_rank: Super Contributor
timestamp: October 08, 2022, 11:36:45 am
content: The "300 mA +/- 5%" makes me think it's a constant current supply.

author: pcprogrammer
author_rank: Super Contributor
timestamp: October 08, 2022, 12:03:19 pm
content: Second that. Also the DC36-72V bit sways me towards the constant current output.

author: RoGeorge
author_rank: Super Contributor
timestamp: October 08, 2022, 04:30:07 pm
content: It is supposed to give max 300mA constant current when a load of 12...18 series LEDs are connected at the output. Without any load, I was hoping for the voltage to stay at its specified max 72V DC.Same for a load that draws much less than 300mA (like the 10-20mA I need), I expect the voltage to stay very close of the max specified, 72V DC.I'm not sure what will happen when the output of two such drivers are connected together, in series, to give +/-72V, and was hoping somebody else already did this, and know what happens when 2 SMPS modules are put in series.They work, or pop?

author: inse
author_rank: Super Contributor
timestamp: October 09, 2022, 05:55:59 am
content: The driver will run into some kind of open loop protection if the set current cannot be achieved.What the output voltage quality will be like or whether this means stress to components are the questions.Maybe LED drivers are not the best choice for repurposing...

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 09, 2022, 09:07:17 am
content: the best way is study what IC is there and how it controls the output (constant current or constant voltage?) it should be interesting when you know it that you can change its behaviour from constant current to constant voltage by changing/swapping/relocating resistor or components, if its possible.. but if they are really floating/isolated, it should wont hurt to try to connect them in series and put the load in and measure voltage with oscilloscope/dmm.
Two single supplies vs one dual supply - Page 1
Forum section: electronics / beginners

author: Awshua
author_rank: Contributor
timestamp: January 02, 2017, 06:23:12 pm
content: I'm finally thinking about getting some proper power supplies (at least proper within my very limited hobby budget).I've seen Dave's videos on the Korad supplies (and subsequent fix), and they appear to be a descent supply for the money.My question is, is there any advantage to getting two KA3005P single supplies as opposed to one KA3305P triple supply, especially given that currently the former would cost about $60-80 more?Sent from my iPhone using Tapatalk

author: Simon
author_rank: Unknown
timestamp: January 02, 2017, 07:47:10 pm
content: It all depends on what you are trying to do. Some people work with lots of power from one voltage source others may be working wityh lower power from multiple voltages. It really depends on the work you plan to do.

author: MatthewEveritt
author_rank: Unknown
timestamp: January 02, 2017, 08:24:45 pm
content: Duel supplies typically have parallel tracking, which means you can draw more current. Obviously you can put two single supplies in parallel to get the same result, but you can't adjust the voltage with the outputs turned on else they'll 'fight'.Same goes for series operation - it's possible with single supplies, but often duel supplies do it better.

author: jeroen79
author_rank: Frequent Contributor
timestamp: January 02, 2017, 08:26:09 pm
content: It also depends on how the dual supply is connected internally.If the outputs are isolated from eachother then tge dual or triple supply is just the same as the singke supply, but all in one box.If they share a common ground then you are more limited.Often the dual supplies have a panel switch to easily switch between isolated, parallel and series configuration, which saves wires.

author: Awshua
author_rank: Contributor
timestamp: January 04, 2017, 04:16:26 am
content: Thanks. I think the dual supply will meet my needs then. Honestly for anything I've done as of yet anything over 18v and a few hundred milliamps is overkill. It does look like they can be ganged either serial or parallel internally so should the need arise it shouldn't be an issue. I just wanted to be sure I wasn't missing something obvious.Sent from my iPhone using Tapatalk