hybridfree/eevblog-posts huggingface dataset:
my new scope - Page 1
Forum section: electronics / beginners

author: m3vuv
author_rank: Super Contributor
timestamp: May 20, 2020, 09:06:17 am
content: Hi all,ive just brought a :KENWOOD DCS-8200 PROGRAMMABLE DIGITAL STORAGE OSCILLOSCOPE from ebay,my current scopes are an old heath pc scope,my everyday scope is a tek 453 50mhz bandwith,im just wondering the pros and cons of the kenwood over the tek,they are both 50mhz scopes,ie would the kenwood display the frequency of the signal at the input and would i be able to zoom in on the trace?,it will be a week before it gets here,also i gave £67 for it including postage,is that a good price?,cheers all m3vuv.

author: Gyro
author_rank: Super Contributor
timestamp: May 20, 2020, 09:55:42 am
content: Hmm, that's an unusual one - it appears to be one of the old hybrid Analogue + Digital storage mode models. It looks a decent 2 channel 50MHz analogue bandwidth scope, but is only 20Msps on the digital mode, giving 8MHz single shot and 50MHz Equivalent time sampling (repetitive signal), with 2k samples per channel display memory and 16k samples total (presumably able to roll back and forward through 8 screens worth). Also the same in a reference memory. On the upside, it does have a pen plotter interface and comprehensive GPIB functionality. It also seems to have cursors, display readout etc.As for good price? Well assuming that it's working, it meets the £1/MHz criteria for a decent analogue scope (if you assume £16 postage) and has the additional digital functions and GPIB. It should certainly give you a lot of fun for a comparatively small amount of cash.I found a copy of the comprehensive Operating Manual....http://www.cieri.net/Documenti/Kenwood/Test%20Instruments%20-%20User%20Manuals/DCS-8200%20-%2050%20MHz%20Programmable%20Dual%20Trace%20Digital%20Storage%20Oscilloscope%20(Eng).pdfThe service manual doesn't appear to be on any of the normal shared repositories, but it looks as if you can purchase a PDF copy for $4.95 from several sites (check that itisn'tthe same manual that I linked above!)

author: m3vuv
author_rank: Super Contributor
timestamp: May 20, 2020, 10:09:33 am
content: ive got the owner manual downloaded,couldnt find the service manual tho,fingers crossed i wont need it,should be fun to play with,this was the listing :https://www.ebay.co.uk/itm/KENWOOD-DCS-8200-PROGRAMMABLE-DIGITAL-STORAGE-OSCILLOSCOPE-/324163319386?ul_noapp=true&nma=true&si=hXoDkaechFgjdH2y4SHx2PAcdnM%253D&orig_cvip=true&nordt=true&rt=nc&_trksid=p2047675.l2557

author: Gyro
author_rank: Super Contributor
timestamp: May 20, 2020, 10:42:13 am
content: A couple of sites (probably related)...https://www.manual-buddy.com/p/kenwood/dcs8200-service-manual.htmlhttps://www.manualscenter.com/manuals/kenwood/dcs8200-service-manual.htmlAs for the 'Battery down' message, I think the manual says something about the battery being able to maintain the reference trace for 30' odd days. No idea what type - probably NiCd at that age.

author: m3vuv
author_rank: Super Contributor
timestamp: May 20, 2020, 11:36:10 am
content: yes i spotted that,suppose its similar to a cmos battery,will know more when it arrives.
My Newark Order is Messy. Typical? - Page 1
Forum section: electronics / beginners

author: NT0Z
author_rank: Regular Contributor
timestamp: January 29, 2023, 02:29:27 am
content: Hi, gang,A year ago I ordered a bunch of SMD caps from a Newark sale, and I just got around to unboxing them.Of the 60 individual bags, half had a stick-on label that showed the description of the actual part's value. Half the bags only had a dozen or so cryptic stock numbers, pick codes, etc, but NO indication of part values. And the SMD parts themselves have no visible designators.I had to cross-ref the 16-digit item codes on the bag stickers with the codes on the packing list. Of course, everything is in 4-point "mouse type" (about 12 pages of it).This was tedious and took a long time, which makes the sale savings less attractive.Actually, if this is a standard thing with Newark, I don't think I'll be back. Is it standard?Of course, Newark HAD to have lost money on my order. Sixty tiny "ziploc" bags with SMD parts inside were each packaged in giant bubble mailers, and the giant mass of mailers came to me from three warehouses. The caps, which can fit inside a cigar box, had a shipping volume equal to that of a dorm fridge (almost).Now, I use the mailers as package padding when selling on eBay, but c'mon, there can't be any profit in my $60 order with that much packaging material, multiple warehouse drops, etc. So, if Newark is trying to discourage me from doing business there, I get it. And it's mostly working.What have you experienced?I usually buy from Digi-Key, which is near me in MN. But Newark had a great sale...Thanks,Kirk, NT0Z

author: BillyO
author_rank: Super Contributor
timestamp: January 29, 2023, 05:25:27 pm
content: I use Digi-Key. Never had a problem with orders from them.Never used Newark, but if I had and I had an experience like yours, I would have used them only once.

author: TassiloH
author_rank: Regular Contributor
timestamp: January 29, 2023, 06:28:43 pm
content: Looks like they haven't changed their ways in the last 15 years or soBack during my time in the US, I ordered a lot of SMT components from them (they were a preferred vendor for the university) for a project, lots of different resistor and capacitor values, but mostly 10 or less of each value. Received two big boxes filled with padded mailing envelopes, each containing a plastic bag with the little piece of cut tape. Not all of them had the values on the label, but as I had to check for completeness I had the order with the info at hand.

author: NT0Z
author_rank: Regular Contributor
timestamp: January 30, 2023, 09:56:24 am
content: Wow. My experience exactly.I figured -- and I was hoping -- that this was some kind of temporary Covid Madness issue...--KK
my pcb order issue - Page 1
Forum section: electronics / beginners

author: fitter108
author_rank: Contributor
timestamp: November 29, 2010, 03:49:10 pm
content: I ordered a pcb from PCB CART in china and the board was single sided and was surface mount. The order was filled out as layer = 1 but had soldermask on 2 sides and silkscreen on 2 sides. The pcb had no soldermask on the front side that had no tracks or pads but i wanted the mask so the silkscreen would look good. It shows as finish surface. Was the order my fault because I only asked for a single layer board or was it an oversight of the supplier. Just dont want it to happen again. Not a big deal yet I only ordered two boards. Any advice is appreciated. Darrell

author: Psi
author_rank: Super Contributor
timestamp: November 29, 2010, 11:35:24 pm
content: hm.. I think i'd expect to pay for a 2-layer board if i was getting silkscreening and mask on both sides.It's probably something you need to ask the production house, see what they class as one/two layer and what they will do for each.Always a good idea to add some text on a 'FabNotes' layer to make sure the person doing the board knows what you want.

author: fitter108
author_rank: Contributor
timestamp: November 30, 2010, 03:17:29 am
content: Thanks so much I figure its my fault but i will call them before I do that type of a board again. That fabnote layer is also an excellent idea . great thanks so much again

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 30, 2010, 02:03:16 pm
content: can you post picture of your faulty pcb? sorry, my language reading and writing is very poor.

author: RayJones
author_rank: Frequent Contributor
timestamp: November 30, 2010, 06:52:12 pm
content: You asked for single sided and by the sounds of it only had traces on one side.If you wanted lower side solder mask and silk screen you would need to supply specific instructions for that to happen.Even if you asked for double sided you also usually need to explicitly state lower side silk screening.The fabnotes for your design sound like a very good idea, especially as it is an abnormal request.
My personal Stream Board - Page 1
Forum section: electronics / beginners

author: Forser
author_rank: Contributor
timestamp: September 25, 2017, 07:51:59 am
content: Talked about it a long time ago before Elgato even had announced their Stream Deck.It's been out now for a while and i have looked into it and i feel like i want to make my own version of Stream Deck to learn more about MCU, USB Interface, Touchscreen and design of PCB.I feel i could do something similar to the Stream Deck but without using the same hardware.Elgato is using a ATSAM9G45 Processor which from the specs seem very much overkill since it has a lots of features that isn't used at all like Ethernet, Audio, Card Readers among things.What i am trying to figure out is what type of MCU to use since i only need to handle USB interaction between PC and the panel, Touchscreen on the Panel and some kind of memory storage to save the button images and such on the unit.From my guesses, a Arduino isn't optimal based on the specs Elgato's unit and i also wanting a touchscreen of 5" or bigger (but not bigger then 10").Any suggestions on what kind of MCU that would be capable of USB connection between PC and Unit, Touchscreen Panel and be able to handle memory for storage?Preferable a MCU that doesn't require hotair gun / reflow to solder it to a PCB.Hope i posted this in the right section of the Forums.Thanks in advance for suggestions / advice.

author: Cliff Matthews
author_rank: Unknown
timestamp: September 25, 2017, 04:14:31 pm
content: Op. No response yet? One wonders if most EE's know what a Stream Board is.. (I'm not but I did look it up). It's visual macro/function keys, implemented as a mini usb keyboard from an LCD touch-screen and grid of clear buttons placed on top.

author: Forser
author_rank: Contributor
timestamp: September 25, 2017, 05:30:21 pm
content: Forgot to add a video what it was about.So thank you!
My RIGOL DS1102CA oscilloscope's shows more noise at 50ms/div than at 20ms - Page 1
Forum section: electronics / beginners

author: comfortcube
author_rank: Contributor
timestamp: September 10, 2021, 04:47:17 am
content: Basically, I'm trying to look at noise, and if I set the time scale to 50ms/div or above, and then run a capture (either single sweep or normal or auto), I get a lot more "noise" appearing on the screen than if it was 20ms/div or less. Even weirder, if I "zoom in" to the captured "noisy" signal at 50ms/div, all the noise disappears, and zooming back out to 50ms/div, noise is no longer there. This is easier explained with the images I put up here:https://imgur.com/gallery/mduOwE6I also put an image at the bottom of this post showing the steps involved here. I should point out my trigger settings are set to: Rising Edge CH1, Single Sweep, AC coupled, 100ns Holdoff.This is a bug right? I don't think I'm doing anything weird here...
My silly solution for a BMS  - Page 1
Forum section: electronics / beginners

author: Ehaze
author_rank: Contributor
timestamp: February 22, 2022, 12:30:31 am
content: Any tips or pointers please comment !I have 2 groups of 3, 4bay 18650 holders I want to make some battery packs 12v3s.1 group is 3, 4bay (1s4p protected ) holders . I just had an idea I could connect them directly in series, but now I wonder, the holders are protected from low voltage and so I am not sure if they will allow series connection. The charging plan was to use this xtar 4 bay charger, it has a display so I can see MAHs and Vs. I will use alligator clips to connect a single pack to each bay, keeps the voltage at a standard 3.7 to 4.2 per pack , so I think it will work.The other group is unprotected , so I wanted to us a BMS board for the over discharge and low voltage. Maybe use the BMS for discharge only and a balance charger. I also kind of want to be able to break each pack down quickly with xt30 connectors !I would like to know if anyone could tell me the best way to Bypass the BMS/PCB board for charging ? ( it will be charged by the 16v max,1-4s balance charger) Should I solder the balance wire to the BMS/PCB board's pads or to the nickle strip positive end of each pack ?Should I skip the BMS board and just use a low voltage board connected directly to the final pos/neg wires coming from the full pack ?

author: m k
author_rank: Super Contributor
timestamp: March 01, 2022, 04:46:43 pm
content: Removing protection is always a no no.
My SMPS design keeps blowing up - Page 1
Forum section: electronics / beginners

author: PeteAU
author_rank: Contributor
timestamp: June 08, 2016, 01:38:31 pm
content: Hi All,Please excuse me, I'm a software guy dabbling in electronicsFor a project, I made a little switch mode supply using a typical SOP8 that many manufactures have. It's a RICHTEK RT8272, it's really similar to a MP1584 or Ti TPS54332 I figure.It works OK, for a while. But when I connect/disconnect the (bench) supply a few times, I manage to kill it! The IC stops working and I have to replace it. I guess there's some charge left in the inductor and doing something bad (?).What do you think, should I add some diodes somewhere for protection against VBAT or GND disappearing? I already tried adding the D3 as shown, but it didn't help, still blew up another one.

author: PeteAU
author_rank: Contributor
timestamp: June 09, 2016, 02:00:29 am
content: Thanks blueskull for the reference, looks like good bedtime reading. I am getting some overshoot due to lack of 'damping', it seems. Maybe adding some higher ESR caps will help.

author: AJBotha
author_rank: Newbie
timestamp: June 09, 2016, 08:37:16 am
content: Try adding a TVS diode parallel to your C1 capacitor. This will ensure that if any transients are created they are shorted away from your device. Something like P6KE24AG from On Semi. The Anode on the negative side (GND) and the Cathode on the positive side (after your polarity protection diode).D3 serves no purpose, you can safely remove it.Adding the 0.1uF ceramic cap from SS to GND might also help,this "Soft Starts" your output and is usually a good idea.

author: Yansi
author_rank: Super Contributor
timestamp: June 09, 2016, 10:02:08 am
content: Show us the layout.

author: PeteAU
author_rank: Contributor
timestamp: June 09, 2016, 12:06:03 pm
content: I took the tip from the "Ceramic Input Capacitors Can Cause Overvoltage Transients" PDF and put a tantalum in parallel with C1. It did the trick! It's only overshooting around 1 to 2V now, instead of 24V!

author: Kyklas
author_rank: Newbie
timestamp: January 15, 2018, 01:00:04 am
content: Hi,Thanks for this investigation. I got some step down from ebay and they keep blowing up as well : Mini DCDC Buck Converter Step Down Module Power Supply For aeromodellinghttp://r.ebay.com/Dx5vLd.

author: Kyklas
author_rank: Newbie
timestamp: January 15, 2018, 04:08:54 pm
content: I tested the input capacitor transient from my module and the overshot to a step input of 15V gives 35.2V. This does kill the RT8272 IC. Adding a 100uf 25V Aluminum Electrolytic Capacitor reduced the overshot to 17.2V.I blew at least 8 module. The issue happens when I used high input voltage. I set my regulator to 5V and 12.8V powered from a 15V supply. The regulator generating 5V powered from 12V have not fried yet.

author: fcb
author_rank: Super Contributor
timestamp: January 15, 2018, 04:27:08 pm
content: I love AN88."When switch SW1 in Figure 1 is turned on, the mayhem starts."

author: Neilm
author_rank: Super Contributor
timestamp: January 15, 2018, 08:06:11 pm
content: Double check the layout - I have seen PSUs blow up purely due to poor layout.
my SMPS is will be OK ? - Page 1
Forum section: electronics / beginners

author: ammjy
author_rank: Regular Contributor
timestamp: December 28, 2017, 07:30:08 pm
content: Hello, guys !! i need advise.i use mean well LRS-350-48 SMPS. it have 48 V, 7.3 A spec.cause by my misstake, via multimeter probe tip - 230V AC Netural line and Product shield connected 2 times shortly.. and i saw little spark.between 230V AC Netural line and Shield, voltage is 110 V almost.my SMPS will be fine ?still work and output DC voltage is normal. i just worry.

author: eblc1388
author_rank: Frequent Contributor
timestamp: December 29, 2017, 01:35:15 am
content: As I have read from your post, you have only live and neutral connection to the power supply. The power supply shield, which should be connected to the mains earth, was not connected. You have accidentally shorted the shield to the neutral via a probe tip and saw little spark.If that is correct, then you should not be worried. It will not damage your power supply at all.However, I would advise to provide an earth connection to the shield, because as you have noticed, the shield can float to some high voltage because of the Y-capacitor inside the power supply. You wouldn't want tinkling feeling every time you touch the power supply shield, would you?

author: Yansi
author_rank: Super Contributor
timestamp: December 29, 2017, 02:10:59 am
content: Doesn't the manufacturer clearly say the ground should be hooked to?http://www.meanwell.com/Upload/PDF/Enclosed_Type_EN.pdfWarning / Caution !!(5? The ground(FG) must be connected to earth ground.Not respecting that is a very VERY bad practice! Always hook the ground properly, if the device requires you to do so. Even if you need to do a "quick test".

author: Yansi
author_rank: Super Contributor
timestamp: December 29, 2017, 12:55:23 pm
content: Neutral should be never touched either!Both the line and neutral have to be considered "hot" and potentially dangerous. Which makes sense. Never ever think of touching any of these, except ground.

author: ammjy
author_rank: Regular Contributor
timestamp: December 30, 2017, 09:19:21 pm
content: Thanks you a lot replies, Guys !!
My Startup SMD Equipment - Page 1
Forum section: electronics / beginners

author: sentry7
author_rank: Regular Contributor
timestamp: April 05, 2015, 04:52:05 pm
content: Hey guys,I finally had time enough to sit down and finalize my "cart": stuff I'm getting to start my SMD workbench. Here's what I got so far.Hakko FX888D Soldering StationYIHUA 858D Hot Air Rework Station0.3mm 63/37 Rosin Core 1.2% Solder1.5m 2mm Desolder WickKester 951 Flux PenKester EP256 63/37 Lead Solder PasteESD Tweezers / ForcepsDesoldering Pump / Sucker10X Headset MagnifierI need to find out whether the tips for the Hakko 936 are compatible with the FX888D, but other than that, here's what I have. Any suggestions?
my turtle beach p11 headsets keep falling apart, is there anyway to prevent this - Page 1
Forum section: electronics / beginners

author: frondaro
author_rank: Newbie
timestamp: December 16, 2024, 10:12:20 am
content: hello, i'm not a professional, i have never messed with my electronicsi have bought several dozen turtle beach p11 headsets and they keep falling apart at the same two places, where the cord connects to the headset or where the cord connects to the middle pieceis there anyway to prevent this? i'm tired of having to buy another set off ebay EVERY THREE MONTHSthank you

author: Halcyon
author_rank: Unknown
timestamp: December 16, 2024, 10:24:59 am
content: It seems the clear answer is: Stop buying Turtle Beach. They are (not so) cheap Chinese shit.They are a long way from what they used to be. Kind of like Nokia back then compared to now.

author: frondaro
author_rank: Newbie
timestamp: December 16, 2024, 11:58:57 am
content: okie dokie,what should i buy?

author: amyk
author_rank: Super Contributor
timestamp: December 17, 2024, 10:55:18 am
content: It sounds like they didn't provide enough strain relief for the cable.
My tv starts to flicker... - Page 1
Forum section: electronics / beginners

author: lukesavenije
author_rank: Newbie
timestamp: May 17, 2019, 06:02:49 pm
content: Hello everyone, just recently my Salora 40led1500 started to flicker, started with a little once in a while, then started to do it heavily, and now it's running somewhat normal again. I'm curious what you guys have for solution, but keep in mind that i'm a beginner with tv hardware, tho i have some a lot of experience on computer hardwareI've opened the backside of the tv to see if i could notice anything weird, but i wanted a varification... here some things i have recorded:https://youtu.be/qarB8ygJhm0any help is appreciated

author: lukesavenije
author_rank: Newbie
timestamp: May 17, 2019, 06:06:15 pm
content: another (longer) videohttps://youtu.be/ZyCBqF99qQo
My understanding of the cause of common mode noise in my measurement - Page 1
Forum section: electronics / beginners

author: eTobey
author_rank: Super Contributor
timestamp: December 22, 2024, 12:48:33 pm
content: Hi,i have read a bit, drawn my circuit and started thinking. Because i did not comprehend why the noise was exactly generated in the scope/circuit, even though i had the probe shorted.Now i have come a conclusion and would like to know if this is true, and if there are other circumstances where this would be not the case or somehow different:"The noise is generated by a current that flows through the GND lead of the probe (through earth GND back to the supply and its parasitic capacitances), and therefore creating a voltage."

author: m k
author_rank: Super Contributor
timestamp: December 28, 2024, 02:18:25 pm
content: Practically everything is an antenna of some sort.So everything must be filtered somehow also.If your shorted probe is showing a shape of a line voltage it is not shorted to neutral.

author: eTobey
author_rank: Super Contributor
timestamp: December 29, 2024, 02:26:48 pm
content: Quote from: m k on December 28, 2024, 02:18:25 pmNeutral? You mean earth ground?

author: m k
author_rank: Super Contributor
timestamp: December 29, 2024, 04:12:06 pm
content: More like a point the PSU treats as neutral.It can still be "far" from real earth.When you short the probe you still have a triangle of probe leads and a circuit at the other end.Some say that for 4-wire measurement you should have all leads disconnected from the bundle.I guess that starts to be around a magic category.
My wee 555 timer circuit!  - Page 1
Forum section: electronics / beginners

author: Terry01
author_rank: Frequent Contributor
timestamp: May 24, 2018, 10:54:32 pm
content: I have a wee "555 circuit" made up on a breadboard that's been in my 1 of my desk drawers for well over a year now!I love adding in a couple more LED's or changing the capacitors or resistors around and measuring the changes around the circuit on 2 or 3 meters,,....4 or even 5 if it's the weekend and i'm really going at it!Every newby should make something like this up and spend a wee while tinkering with it. It's amazing what you can learn from a simple wee circuit!The 555 is such a simple wee chip but it's so versatile!Tonight's yabber over

author: james_s
author_rank: Super Contributor
timestamp: May 25, 2018, 01:02:22 am
content: The 555 really is pretty amazing, and as I recall it almost didn't get developed. Even now that a microcontroller can do just about anything a 555 can do and for about the same cost, I still like to use the old 555 now and then.

author: Terry01
author_rank: Frequent Contributor
timestamp: May 25, 2018, 06:57:29 am
content: Yes, i'm sure I have read that too James. It's survived the "test of time" as they say right?I just went and read some of the Wiki info about it just now!On the go since 1972, 1 billion per year(estimated) produced, the most popular IC ever made.....yada yada yada....!I'm going to do the same with a couple other chips and again just leave them made up so I can "tinker" with them and see what and how every part of the chip is working. I know for me I had a few "I understand now" moments with that simple wee circuit.
Myson Century MTL015GG Datasheet - Page 1
Forum section: electronics / beginners

author: Griffin
author_rank: Unknown
timestamp: March 02, 2012, 05:21:00 am
content: Hi every1I've been looking for the datasheet for the this chip: Myson Century MTL015GG for a while now. I have a bunch of reverse cameras with their dash mount displays but all have some form of power problem. So I am looking at reusing some of the parts, they have nice 7" LCD's and, Atmga 168, a video decoder chip and these Myson chips.Anyone that now where I can uncover the datasheet for that chip?
Mysteries of the Vizio SB2020n-J6 sound bar - Page 1
Forum section: electronics / beginners

author: Peabody
author_rank: Super Contributor
timestamp: December 12, 2022, 10:39:57 pm
content: It sells for $70, which I guess means I shouldn't expect much. Anyway, here's what my Kill-a-watt says using an optical cable:Off 1.9WOn, TV off 1.9WOn, TV on, Mute 2.1WOn, TV on, medium volume 2.2WOn, TV on, high volume 3.5 to 4WSo it appears there's no particular point in turning it off when not in use. I would have to unplug it to make any difference. But you know, it's 2 watts. What's surprising is how little power it uses to produce pretty loud audio. Not home theater quality, but better than the TV speakers.I do have one issue with it, which is that it is unable to "learn" the IR commands issued by my Sharp TV remote's Vol-, Vol+, and Mute buttons. The manual says it will, but it won't. Does anyone else have this model that could test that? I don't want to return this one only to have the replacement do the same thing, and it may be that the Sharp IR protocol is just too strange.
Mysterious connector (fan of the DP832) - Page 1
Forum section: electronics / beginners

author: ElektronikLabor
author_rank: Regular Contributor
timestamp: March 19, 2014, 08:30:34 pm
content: Hello,I'm searching for the name of the connector for the blowers of the power supply Rigol DP832; I can't find anythingBelow 3 pictures of the connector.Please help meThanks

author: Legion
author_rank: Frequent Contributor
timestamp: March 19, 2014, 09:00:14 pm
content: Looks like a JST PH connector. But your's has 4 wires coming off it, normally there's only two.

author: ElektronikLabor
author_rank: Regular Contributor
timestamp: March 19, 2014, 09:38:44 pm
content: Thanks Legion,the JST PH looks for me a little bit different; here a pic of it:The JST PH has only one bar at one side; the connector I'm searching for has two parallel bars. Maybe it's a some sort of variation?BTW: The connector has 2 pins; Rigol violated it with two parallel blowers (2 wires per pin)

author: notsob
author_rank: Frequent Contributor
timestamp: March 19, 2014, 10:15:01 pm
content: looks like the JST XH series [2.5mm pitch] - try digikey for them

author: ElektronikLabor
author_rank: Regular Contributor
timestamp: March 19, 2014, 10:33:04 pm
content: Thanks,That looks promising!I will buy the crimp contacts tomorow in a local store and order the housings todayThumbs up for the competence of both of you, notsob and Legion!
Mystery (to me) OPamp circuit - Page 1
Forum section: electronics / beginners

author: Muffins
author_rank: Regular Contributor
timestamp: June 26, 2019, 02:39:53 pm
content: Hi guys.I have a circuit I need to understand with for a course I'm doing. It is some sort of power circuit using opamps. I have not done much with opamps yet and the textbook I'm working from has a single diagram of the circuit without any description. Does anyone know what the below circuit is called?

author: StillTrying
author_rank: Super Contributor
timestamp: June 26, 2019, 02:59:57 pm
content: Does anyone know what the below circuit is called?A lamp dimmer ?https://en.m.wikipedia.org/wiki/Phase-fired_controller

author: rstofer
author_rank: Super Contributor
timestamp: June 26, 2019, 03:01:46 pm
content: It's a lamp dimmer...Let's start with X2 - it is being used as a comparator to detect zero crossing. You can see where the + input is SLIGHTLY higher than ground. When the waveform slightly crosses 0V, the comparator switches. When it does, it triggers the transistor to short out the timing capacitor.X1 is an integrator or ramp generator. It charges up on C2 and creates a ramp that is reset by X2 (above).X3 is another comparator and triggers when the ramp voltage gets to the voltage set on the + input. Thus there is a delay caused by the ramp voltage and this turns the lamp on at some time after zero crossing. The delay is adjustable with VR1.The lamp turns on at some point after zero crossing and turns off at the next zero crossing. Maybe it's easier to think about as: the lamp turns off at every zero crossing and turns back on after some delay. Given the full wave rectifier, this happens on every half cycle or twice the nominal line frequency.Something like that...Just take apart each of the 3 op amp blocks and analyze them separately. Zero crossing detector, ramp generator, delay/switching.

author: Muffins
author_rank: Regular Contributor
timestamp: June 26, 2019, 04:22:08 pm
content: Thanks guys. I can move forward from here.rstofer, your explanation makes sense, thank you for taking the time to make it.
Mystery component - Page 1
Forum section: electronics / beginners

author: shmashma
author_rank: Newbie
timestamp: January 09, 2020, 12:00:57 pm
content: Hi everyone,I have a nice old surface mount component here with a crack in it.I think it's probably a 50 ohm resistor because thats what I measured across. I'm not sure what LJ stand for, anyone?

author: mvs
author_rank: Frequent Contributor
timestamp: January 09, 2020, 12:56:47 pm
content: It looks like a thermistor (NTC or PTC). To be sure, you can heat it and measure resistance again.50 Ohm NTC you may find in a small switched PSUs. It is used to limit inrush current.

author: shmashma
author_rank: Newbie
timestamp: January 09, 2020, 02:52:56 pm
content: Thanks, that's super helpful. The part is pretty erratic but I can raise or lower the resistance depending on the side I heat up so I'm confused.
Mystery component on rotating plinth with LED lights - Page 1
Forum section: electronics / beginners

author: Quantumplate
author_rank: Regular Contributor
timestamp: April 21, 2022, 09:17:54 pm
content: This thing runs off a 6v A.C. source to power the synchronous motor. Has about ten Leds of different colours that uplight your object for display. On the pcb are 4 diodes, 2 filter caps, 2 trannys and a few resistors AND this thing sticking up on a separate small board. I assume this is some kind of ic to make the lights do a pretty pattern, but never seen one like this. The light show on my unit is not working properly, so I suspect this component. Anyone know if I can get a replacement anywhere? Thanks

author: golden_labels
author_rank: Super Contributor
timestamp: April 21, 2022, 11:54:49 pm
content: That is a daughterboard, which contains an unmarked intergrated circuit. The IC is placed directly on the board and covered with epoxy, also known asblack blob, instead of being in its own package.Almost universally direct identification of such chip is impossible and at best it may be guessed by comparison with similar devices, other version of the same device, or — if the board itself can be identified — from its schematics.
Mystery components? What are these? - Page 1
Forum section: electronics / beginners

author: sourcedog
author_rank: Newbie
timestamp: August 02, 2014, 06:35:16 pm
content: So, quite some time ago I got an assorted collection of basic components cheaply on ebay (you have to start somewhere, right?) and basically, it's what I've expected it to be. But there was one bag in there with components I've never seen before:http://abload.de/img/20140802_192308shuif.jpgWhat could that be? My interest is piqued quite a bit.They seem to be some kind of diode. At least, if I use my multimeter the right way, that isIf that's the case, do they have a special usage case?

author: PA0PBZ
author_rank: Super Contributor
timestamp: August 02, 2014, 06:38:49 pm
content: I'd say zener diodes, looking at the different numbers on them which look like voltages a lot.

author: sourcedog
author_rank: Newbie
timestamp: August 02, 2014, 06:58:45 pm
content: Alright, that seems to be case. I grabbed a random one out of the bag (one with 6.8 marked on it) and it has absolutely no conductivity in reverse and about several Megaohms in the other direction (forgot how much exactly). When turning my multimeter to diode test, it shows 0.68 Volts. Guess the weird package and the fact I don't understand zeners fully, yet, threw me off.Thanks for the hint
Mystery Device(s) - Page 1
Forum section: electronics / beginners

author: metrologist
author_rank: Super Contributor
timestamp: October 22, 2016, 10:52:14 pm
content: I have my late grandpa's parts bins and have been trying to identify many of the components. Many if the IC's I can find datasheets, but many I cannot, and there are some parts unmarked.Here is a very small passive device. The 2 legs at the top are hair sized and about an inch long, so the device is small SMD size; however, grandpa has nothing SMD and much of what he has is 70's-90's vintage. If this is not for microwave, what could it be?p.s. I have several in a plastic package, so the image is looking through old plastic under ~20x mag.

author: Rerouter
author_rank: Super Contributor
timestamp: October 22, 2016, 10:53:37 pm
content: Its either an inductor, or a strain gauge by my eyes,Resistance should chance when deflected if a strain gauge.

author: RoGeorge
author_rank: Super Contributor
timestamp: October 23, 2016, 12:14:32 am
content: My first bet would be for a strain gauge.Second bet, maybe an RTD:http://www.capgo.com/Resources/Temperature/RTDs/RTD.html

author: metrologist
author_rank: Super Contributor
timestamp: October 23, 2016, 12:20:46 am
content: That's cool. I think it is Resistance Temperature Detector (RTD). Thanks!I bet he had them for replacements for his DMM.

author: SeanB
author_rank: Super Contributor
timestamp: October 23, 2016, 04:53:00 pm
content: If it is a ceramic substrate it is a Pt100 sensor, and if it is on a mylar or Kapton substrate it is a strain gauge. Pretty much the same thing, just the one is on a close to zero expansion substrate to measure temperature, and the other is designed to be exposed to strain.

author: metrologist
author_rank: Super Contributor
timestamp: October 25, 2016, 01:14:33 am
content: LoL! In Dave's latest mailbag #936 he shows many of the same sort of old stuff I have. The transistors, dip IC's, and resistors and caps from that era.
Mystery Diode - Page 1
Forum section: electronics / beginners

author: kars
author_rank: Contributor
timestamp: August 31, 2021, 10:16:08 am
content: Hi all,I've been browsing some datasheets for a project im working on and i have found a diode type i have never seen before. (see attached image)God knows what this thing is. Looks a bit like a crossover between an SCR and zener diode.Does anyone have any idea what this thing is?

author: Benta
author_rank: Super Contributor
timestamp: August 31, 2021, 10:36:09 am
content: Voltage reference, eg, TL431.

author: kars
author_rank: Contributor
timestamp: August 31, 2021, 10:46:54 am
content: Aaah, i have never seen them like this before. Thanks!

author: Zero999
author_rank: Super Contributor
timestamp: August 31, 2021, 11:21:28 am
content: It's often called a programmable zener diode, but is really an op-amp, driving a small transistor, with a voltage reference connected to the input. Page 20 of the TI data sheet has a block diagram.https://www.ti.com/lit/gpn/tl431

author: David Hess
author_rank: Super Contributor
timestamp: August 31, 2021, 04:10:20 pm
content: That is the symbol I use for adjustable shunt regulators and references like the TL431.
Mystery, diode raising no load voltage measurement. - Page 1
Forum section: electronics / beginners

author: BlackICE
author_rank: Regular Contributor
timestamp: July 18, 2022, 12:40:46 am
content: I have an old phone SMPS wall wart labeled 5v 700ma that I want to use to power a micro controller. I measured the voltage and got 5.75v. Using a scope I measured the ripple to be 40mv ptp at 30 Khz. I thought no big deal I'll use a diode to bring the voltage close to 5v. To my surprise without any load the voltage increased to 6.33v, using a 5K load resistor I got what I expected 5.25v, which should be fine for the micro.How does the diode increase the voltage?What's the expected lifespan of no name wall warts? I will be drawing less than 1 ma most of the time and for 45 mins 100ma flipping and powering relay controller. I'm planning to use this as a defrost timer on a refrigerator. The micro goes to sleep for 12 hr than wakes up to disable the compressor for 45 minutes then the cycle restarts and continues forever.

author: jwet
author_rank: Frequent Contributor
timestamp: July 20, 2022, 10:59:10 am
content: DVM's have a very high input impedance- 10M and a little bit of capacitance, diodes have capacitance and some reverse leakage current- also small but working against 10M, significant. What you have done by connecting an unloaded series diode (a small capacitance with some leakage) to a 10M load with a few pf of your DVM is to make a charge pump. The capacitance of the DVM is getting charged up to the peak peak voltage plus a bit or leakage current. Lesson- you need to load rectifying circuits with enough current to kill these leakage and capacitive effects. What you're reading isn't really real, any load other than a DVM would squash this stuff. Measure the voltage across your load or add a 470 ohm resistor etc.As far as longevity of wall cubes go- linear wall cubes are pretty long lived especially if they don't run hot. Switchers are less reliable. In both cases, the filter caps dry out over time- switcher ask more from the caps than linears. I would use a linear for this application- it will do better at the very light loads- you might also add an LED to your circuit so the wall cube will have a minimum load of 10 mA or so- you're not wasting any power really- the losses in the transformer will exceed this. Think of the wall cube that powers your Cordless phone- they last a decade of more.

author: Terry Bites
author_rank: Super Contributor
timestamp: July 20, 2022, 03:00:40 pm
content: I had one of these horrible PSUs catch fire in front of me once, so I'm very wary of leaving them unattended.

author: BlackICE
author_rank: Regular Contributor
timestamp: July 21, 2022, 11:15:17 pm
content: Thanks for the info. That implies that the PtP noise is greater than what I measured on the scope, which if likely since I measured with the BW filter on. When the MC and relay board is hooked up, the min current draw is about 1ma. Which brings the voltage into the correct range.
Mystery night light - Page 1
Forum section: electronics / beginners

author: Peabody
author_rank: Super Contributor
timestamp: March 02, 2022, 06:01:52 am
content: I closed today on the purchase of my downsizing condo, and spent time going over the keys and such, and noticed something strange. The hall bathroom has two flood-type lights above the sink, operated from a standard switch (not dimming). When I turn the lights off, they continue to glow dimly. When asked, the sellers said it's been doing that for about a year, and think it may have something to do with the kind of bulbs they use. Ok.Well, I never heard of such a bulb, or switch. It seems to me that if the switch switches the live line, then the switch is leaking when turned off. If the switch switches neutral, which it shouldn't, then it could be that the switch is ok but the light fixture is leaking to ground.Is there any type of bulb, fixture or switch that would make this behavior ok, or do I need to get it fixed. The home inspection results didn't mention it.

author: Berni
author_rank: Super Contributor
timestamp: March 02, 2022, 06:09:37 am
content: Some LED bulbs can run on a really really tiny current.So it is possible for the capacitive coupling between the wires to transfer enough current to barely light up the bulb. You can fix this by replacing it with a different bulb that needs more current to light.

author: CaptDon
author_rank: Super Contributor
timestamp: March 02, 2022, 03:48:20 pm
content: This often happens when the switch itself is lighted. Many times people take out the incandescent lamps and put in led lamps and have the exact same problems. I have also seen the led lamps flash on briefly about once a minute when supplied through a lighted wall switch.

author: Peabody
author_rank: Super Contributor
timestamp: March 02, 2022, 10:56:09 pm
content: Yes, it turned out to be a lighted switch. But I don't think it was working correctly. I could play around with the switch knob and the dim light would come and go. And I couldn't detect any light at the switch. Anyway, the switch didn't need to be lighted so I replaced it with a standard switch, and all is well.I guess the problem is that there is no neutral line at the switch, so to have a lighted switch a small current has to pass through the light bulb. And while that's typically not enough current to produce light with incandescent bulbs, it seems you do get some light using LED bulbs.
Mystery optoelectronical parts - Page 1
Forum section: electronics / beginners

author: HomoSovieticus
author_rank: Newbie
timestamp: May 05, 2015, 04:21:32 pm
content: Hello, maybe someone can explain me what you see in the pictures ? I know it has something to do with optoelectronics. I couldn't find any better forum to ask. Internet doesn't give any information on them. Maybe someone is interested in them ? They are super super heavy items 1 box is like >30kg easily. See the links below.http://postimg.org/gallery/24smb8m14/79f25c45/What the heck ?? I also own some other interesting pieces without any knowledge what it might be used for ? Like these(and if you are into guessing or have ever worked with things like these I'm super interested in hearing whats up with these things) The big ass metal stand seems like some laser positioning system or whatever ? And interestingly enough it seems that it was never used... :Whats the matter with big round glasses ? Filters ? What kind of ? How to find out ? Check it out here :http://postimg.org/gallery/70zashhs/64448460/Thanks for helping to resolve these mystery items.

author: bitwelder
author_rank: Super Contributor
timestamp: May 05, 2015, 04:48:09 pm
content: The second picture shows the LOMO logo (https://en.wikipedia.org/wiki/LOMO)Perhaps it's possible to ask them what the model OP-23 is, or with some luck find something in their catalogues?

author: HomoSovieticus
author_rank: Newbie
timestamp: May 05, 2015, 04:56:09 pm
content: I have sent e-mail to LOMO. It was very nice idea. I somehow thought that LOMO doesn't exist anymore. What is q switched laser ?

author: HomoSovieticus
author_rank: Newbie
timestamp: May 06, 2015, 09:28:47 am
content: I don't really understand how that can be any type of laser ? It seem like pure piece of metal, no diodes, no wires, nothing ?Any other ideas ?Now a question for you : What the word offtopic means ?
Mystery Part Thread - Page 1
Forum section: electronics / beginners

author: Sirius631
author_rank: Contributor
timestamp: March 24, 2015, 10:22:12 am
content: I have a few Ergomo cycling power meters which have all died, presumably due to the poxy lifespan of the internal NiMh cells. One was already dead when I got it, but it's the strain gauge sensor on the bottom bracket axel which is the important part, so that didn't matter at the time.I have now bought several new NiMh cells of the right voltage, but they are larger, so won't go in the case. The old cells never had the storage capacity to last on a full day's riding. I'm now looking to secure the batteries in the handlebar tube and run a connection lead under my bar tape. I'll take the opportunity to see about charging them with a balanced charge controller, too, since I know the old cells died unevenly.Anyway, whilst I had the case open, I came across this strange looking component. (See attached) It reminds me of a CCD, as there is a lens unit through which the chip die can be clearly seen. If it is a CCD or other opt device, what is it doing in an enclosed case, looking at a black lable?

author: bktemp
author_rank: Super Contributor
timestamp: March 24, 2015, 10:27:38 am
content: It looks like a pressure sensor:http://www.hoperf.com/sensor/barometer_16/HP03S.htm

author: Sirius631
author_rank: Contributor
timestamp: March 24, 2015, 11:39:33 am
content: Quote from: bktemp on March 24, 2015, 10:27:38 amD'oh! Yes, the power meter logs altitude by barometric pressure. I still wouldn't have guessed that this was the pressure sensor looking at it.
Mystery PCB Jumper Number Order - Page 1
Forum section: electronics / beginners

author: DROBNJAK
author_rank: Contributor
timestamp: December 10, 2012, 04:29:53 pm
content: I need to connect IEEE-1394 6-pin cable to a pin group J28. Does anybody know how pin numbers are determined in this layout:- Is a pin marked with A the pin #1? Or, is the pin marked with B the pin #1?- Which are pins 2, 3, 4, 5 and 6? Is it that count grows by rows? Or, does count grows by columns?Thanks in advance. Google just gives me a lots of answers how to connect HD disks and CD-ROMs, which is not my case.

author: c4757p
author_rank: Super Contributor
timestamp: December 10, 2012, 04:44:31 pm
content: Across the bottom is 1 3 5 7 9, across the top is 2 4 6 8. Pin 1 is marked with a square pad.

author: 8086
author_rank: Super Contributor
timestamp: December 10, 2012, 04:53:33 pm
content: Quote from: DROBNJAK on December 10, 2012, 04:29:53 pmSquare pin is pin 1.Generally you go up, then across and down. i.e. the pin directly above A would be pin 2, the one directly to the right of pin A would be pin 3, etc. Whats confusing me is the position of the 9th pin - in all the pinout diagrams I can find, it's in the 10th position, not the 9th...

author: DROBNJAK
author_rank: Contributor
timestamp: December 10, 2012, 05:02:34 pm
content: Yeah, that is why could never get IEEE FireWire port working. Thanks guys.
Mystery relic Microchip SOT style chip identify please? Looked everywhere - Page 1
Forum section: electronics / beginners

author: TnF
author_rank: Contributor
timestamp: April 25, 2024, 01:20:47 am
content: I've looked everywhere, the package is same "length" as SOT-89 (4.5mm) but width is larger ~3-3.1mm, and has only 3-pins similar to SOT-23 instead of SOT-89 3+tab.2nd pin (middle) is directly connected to ground.3rd pin (right one) 1V forward voltage drop to ground and 0.5V in reverse. Looks like it's directly connected to +5V from a regulator.1st pin (left one) no forward voltage drop across but it's connected in circuit, 0.5V in reverse. Reads +5V in operation and goes to MCU reset pin.The whole board is made in Japan in the 90-00's and uses almost exclusively Japanese branded components. Weirdly this one is branded Microchip. I've even went into checking Microchip's acquisitions thinking it might be a rebranded component.Came across these but haven't yet checked all variations, the package and brands differ but it could be a copied design.Any ideas? Thank youedit: Added pin 1 connectionedit2: MCU Reset pin description:

author: amyk
author_rank: Super Contributor
timestamp: April 25, 2024, 04:25:01 am
content: Not Microchip, butMitsumi.PST600DMin MMP-3A package.

author: TnF
author_rank: Contributor
timestamp: April 25, 2024, 06:16:49 am
content: Quote from: amyk on April 25, 2024, 04:25:01 amThanks a lot! You are godsend ;pI saw this brand while looking, searched for the logo too but didn't do a good job it seems;p To be fair they look identicalI wonder though, where/how did you actually find it?

author: pcprogrammer
author_rank: Super Contributor
timestamp: April 25, 2024, 06:28:39 am
content: I tried to look at the by amyk linked pdf file but my system warns for a potential risk, so here is a link to a safer source for this datasheet:https://www.digchip.com/datasheets/parts/datasheet/304/PST600-pdf.php

author: TnF
author_rank: Contributor
timestamp: April 25, 2024, 01:32:02 pm
content: Quote from: pcprogrammer on April 25, 2024, 06:28:39 amWarning is because it's http instead of https link. Just stupid chrome things. Are you worried of a man-in-the-middle attack on a random datasheet?

author: pcprogrammer
author_rank: Super Contributor
timestamp: April 25, 2024, 01:37:34 pm
content: Quote from: TnF on April 25, 2024, 01:32:02 pmFirefox just refused to download the PDF, so I searched for another one.But nowadays you never know what the hacking idiots do out there, so better safe then sorry.