hybridfree/eevblog-posts huggingface dataset:
Intel IXP425 power supply - Page 1
Forum section: electronics / projects

author: ealex
author_rank: Frequent Contributor
timestamp: August 23, 2013, 12:20:49 pm
content: HelloI've got a switch based on an Intex IPX425 cpu that is acting up.I could identify 3 different power supplies: a 3.3 switch mode one that is working properly and 2 linear ones based on LX8384-00 - 5A adjustable LDO.Both of the LDO's are powered from the 3.3V rail.One of them gives out 1.95V with 0.61V on the adjust pin and the other one gives out 1.3V with just 0.060V on the ADJ pin.The 1.95 one goes to the ethernet isolation transformers and to some RTL8309 switch controllers ( seems appropriate according to the RTL manual) .The 1.3V one seems to go directly to the CPU.From what i can read on the LDO's datasheet they try to achieve 1.25V on the ADJ pin ( Reference Voltage is 1.25V ).I'll try to remove the voltage set resistors from the circuit to measure them - in circuit they have some very strange values.Is the 1.3V rail correct for the intel CPU ?After a while it gets warm but i can't see no activity on the RAM of FLASH bus.I'll start by replacing the capacitors after the LDO's

author: cyr
author_rank: Frequent Contributor
timestamp: August 23, 2013, 02:28:42 pm
content: I'm almost positive 1.3V is the correct core voltage, that's what we had on an IXP425 design I worked on.

author: ealex
author_rank: Frequent Contributor
timestamp: August 23, 2013, 02:31:09 pm
content: Thanks.So the LDO's might be ok.I'll try replacing caps,etc as soon as I get at my work bench.

author: ealex
author_rank: Frequent Contributor
timestamp: August 23, 2013, 06:46:49 pm
content: Update:I've replaced the caps but no changes - when i plug it in all LAN led's turn on and no reaction whatsoever.I've probed around the CPU - no activity on the memory bus or on the FLASH, just several 33Mhz clocks and a lot of pins that are sitting at ~ 280mV.There is a CF card that has a file system with some configuration data that seems ok ( no change when this card is unpluged )No activity on the serial console, etc.I'll try to see if i can connect to the boot flash (intel 28F320)- there is a 2x8 connector next to it.The CPU is in a BGA package - maybe there is a loose connection ?

author: garak
author_rank: Contributor
timestamp: September 01, 2013, 06:47:17 pm
content: I don't know this CPU from Adam, but have you checked the other obvious things? CPU reset lines etc? Often in embedded designs these are connected to a supervisory chip. Pulling up the D/S for this would tell you what it's looking for which might help you in finding electrical issues.

author: ealex
author_rank: Frequent Contributor
timestamp: September 03, 2013, 05:59:14 am
content: I had to return that switch - i could not find info. regarding it's pinout.There were no supervisor chips on board - just several clock drivers that were working and a lot of realtek / network dedicated ic's that i could not test.Thanks for your hints
Intel pciE Gen4 Retimer spec = FUBAR? :o - Page 1
Forum section: electronics / projects

author: frogblender
author_rank: Regular Contributor
timestamp: June 12, 2021, 08:10:42 pm
content: Here is Intel's spec for standardizing Gen4 PCIe retimer pinouts:https://intel.ly/3zcOW8BIt specifies the bga pinout for x4, x8, and x16 pinouts. But for the x16 section only: their table of pin numbers doesn't jive with their BGA drawing pin numbers (see attached).For the x8 section in the spec, the table and BGA drawing jive OK.But for x16, something is messed. Anyone know what is going on?EDIT:the circled in ORANGE in the image is just ONE example. NONE of the pins match. For example, in the table, pins EU26, EW29, N34, R35, Y34, AB35 don't exist on the bga drawing (which only goes up to row 24).

author: ajb
author_rank: Super Contributor
timestamp: June 12, 2021, 09:04:54 pm
content: Seems like just a couple of typos23->34 or 24->35 are easy typos to make if your hands are misaligned on the number row. Looks like the letters are wrong as well, but it's hard to read the text on your screenshot, even with the full image open. It's annoying that the table doesn't seem to be correct, but these are the kind of errors humans will generally overlook very easily, so not a great shock that they snuck through into the final doc.

author: frogblender
author_rank: Regular Contributor
timestamp: June 12, 2021, 09:30:19 pm
content: EDIT:attached is higher-res shot of the bga drawing. NONE of the bga pins match any of the pins in the table.

author: frogblender
author_rank: Regular Contributor
timestamp: June 12, 2021, 09:34:42 pm
content: Quote from: evb149 on June 12, 2021, 09:15:38 pmYes, Fig3-4 does match the table. But the table lacks all power and grounds....

author: frogblender
author_rank: Regular Contributor
timestamp: June 12, 2021, 09:49:23 pm
content: One other thing to point out: this is a funny BGA, with many (most?) pads missing, pads of multiple sizes, some oval pads, and many rows and columns just barely misaligned with their neighbours (see attached from intel spec, coincidently the most illegible drawing from a datasheet in the history of the universe).I think the problem is the "barely misaligned" rows and columns - when you are numbering the pins, and you are working on column "AA" for example, and you encounter a barely misaligned, your choices are:1) decide the barely misalinged is worthy of a new column label, and call it "AB", or,2) decide the barely misaligned is close enough, and leave it as "AA".Intel, apparently, chose to do both, and produced poop.

author: amyk
author_rank: Super Contributor
timestamp: June 13, 2021, 12:10:14 am
content: Quote from: frogblender on June 12, 2021, 09:49:23 pmI can understand missing pads from a regular grid (very common), but slightly-different-sized pads and evenovalones? Who even comes up with stuff like this?

author: frogblender
author_rank: Regular Contributor
timestamp: June 14, 2021, 05:09:34 pm
content: Quote from: amyk on June 13, 2021, 12:10:14 amPerhaps the rational of funky-shaped/off-sized/offset BGA pads is you can squeeze diffpairs between them.
Intelligent LED with  strobe/latch control line - Page 1
Forum section: electronics / projects

author: ricko_uk
author_rank: Super Contributor
timestamp: March 16, 2020, 02:34:40 pm
content: Dear all,do you know of any LEDs similar the WS2812B (datasheet attached) that:- controlled via serial line (i.e. built in controller)- has a strobe/latch line so that the output changes only when that line is asserted- ideally can be chained (this is just a plus not a requirement)Many thanks
Interactive simulator for GUI - Page 1
Forum section: electronics / projects

author: ricko_uk
author_rank: Super Contributor
timestamp: April 05, 2022, 10:38:06 pm
content: Hi,I would like to make an interactive GUI simulation for a touch display product, so for example depending on which button they press a different screen is displayed.It would be helpful for me but also for the client. It would be nice if they can download it on their smart phone (even if the screen size would obviously be different) or as second option, onto their PC.I was wondering about a couple of things...- can you suggest any free solution, preferably iphone/android app and if not then PC?- how do they make those really nice UI graphics? Obviously you can have a graphic designer doing them for you and then use either the vector or the bitmaps. But perhaps there are packages that already have built-in fancy graphic templates?Thank you

author: Nominal Animal
author_rank: Super Contributor
timestamp: April 05, 2022, 11:45:45 pm
content: The simplest method for GUI simulation/demonstration I know of, is to make web pages (HTML+CSS+Javascript) pretending to be the UI. Works everywhere. Use screenshots from actual buttons and so on; then, you can show how the same UI looks on different devices (assuming you target multiple platforms).

author: SiliconWizard
author_rank: Super Contributor
timestamp: April 05, 2022, 11:57:25 pm
content: Yep. Now, if you're not familiar with HTML, or CSS, or JS, it may not be all that easier to do than just writing a quick mock-up UI with your favorite GUI library. But the benefit of going HTML is that you can have other people do it for you. There are many, many web developers out there.I've occasionally used Pencil:https://pencil.evolus.vn/but, IIRC, it doesn't create "dynamic" content. It's just static. That may have changed though, so it's worth a look.
Interest check - Extender boards for TM500-series modules - Page 1
Forum section: electronics / projects

author: mdszy
author_rank: Unknown
timestamp: November 18, 2018, 02:03:31 am
content: I've acquired quite a few Tektronix TM-500 modules, most of which don't work. Repairing them is incredibly difficult because they have to be slotted into the power supply rack in order to be powered on. I've looked for extenders and they're all either very expensive or no longer available.What I've thought of is a design using using two separate boards, one that gets connected to the module, the other gets connected to the inside of the power supply. They'd be connected with a ribbon cable of some kind.Would anyone be interested in this sort of thing? What would you be willing to pay for it? Would you prefer to purchase as a kit (components and boards all provided, just needs to be soldered) if it was cheaper than a fully assembled board? Note that a kit would involve soldering multiple 58-pin connectors.

author: xrunner
author_rank: Super Contributor
timestamp: November 18, 2018, 02:18:39 am
content: You don't need to make those. You can get a pre-made extender cable for cheap. I've used then to repair many TM-500 modules. They are listed on Ebay as JAMMA extender cables, for troubleshooting video game boards, but they use the same connector. The only thing is you need to cut the trace between p1/p2 and p3/p4 on both sides, their boards require that configuration but it's a bad thing for these Tektronix chassis.JAMMA Extender

author: mdszy
author_rank: Unknown
timestamp: November 18, 2018, 02:19:26 am
content: Quote from: xrunner on November 18, 2018, 02:18:39 amWell I'll be spooked. That's awesome! Thank you!

author: xrunner
author_rank: Super Contributor
timestamp: November 18, 2018, 02:20:18 am
content: Quote from: mdszy on November 18, 2018, 02:19:26 amMy pleasure! Enjoy!

author: texaspyro
author_rank: Super Contributor
timestamp: November 18, 2018, 02:43:24 am
content: You mean something like this? I sell kits for $20 each plus shipping.They use two 40-pin IDE cables to connect the boards. Kits include two boards, cables, connectors, LED.

author: dkzahooie
author_rank: Newbie
timestamp: October 21, 2019, 11:53:45 am
content: I'm interested in one of those extenders. Where do I get it?Thanks
Interested in creating high voltage regulator... - Page 1
Forum section: electronics / projects

author: DaveHardy
author_rank: Regular Contributor
timestamp: October 10, 2012, 08:36:28 pm
content: I'm interested in creating a high voltage regulator that is capable of delivering about 250 to 300v with minimal ripple and almost no load. Furthermore, it must have excellent short circuit protection. I plan on using a Villard cascade voltage multiplier circuit to get me up to where I need to be from typical +/- 15v transformer secondaries. The Villard cascade multiplier can deliver high voltages, but there is a huge amount of ripple on the output of it - close to 40v. I've found a few circuits that appear to do the trick on paper, but I'm not sure what to expect in practice because I've never done anything at this high of a voltage with semiconductors.Here are a few of the circuits that I have found so far. I have seen a few Villard cascade circuits with resistors stuffed in them to change the loading characteristics and, I'm assuming to drain the caps for safety, but I can't seem to find any sort of equation that could explain things further. Regarding the BJT circuit, it is pretty self explanatory, but I'm just not sure what to look out for or what to avoid when the voltages are that high. The MOSFET circuit that I posted looks like a real bitch to implement. Does anybody have suggestions or ideas before I start welding leads together on my protoboard? What common failure modes should I be aware of with the BJT circuti? Perhaps someone could post a better circuit than the BJT?-Dave
Interesting article on the pitfalls of replacing CCFL backlights with LEDs   - Page 1
Forum section: electronics / projects

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: December 04, 2016, 08:10:35 pm
content: http://xiphmont.livejournal.com/70696.htmlI don't know how common it is for an LCD to have filters that don't work so well with standard white LEDs, but it's an interesting subject and not something that would have ever occurred to me!

author: SeanB
author_rank: Super Contributor
timestamp: December 04, 2016, 08:28:38 pm
content: Not too surprising, you get some truly bad CRI led lights these days, with a spectrum that is only blue and some other yellow and a bit of red. To match a LED display you need to have light where the filters in the display are, or use a RGB led that matches instead.
interesting board about eevblog and Dave  - Page 1
Forum section: electronics / projects

author: ansonbao
author_rank: Regular Contributor
timestamp: November 29, 2016, 09:13:52 am
content: Today our client sent an interesting picture (pcb design) to us,glad to find eevblog and Dave on it.I think he must in this forum.Hope he will appear in the post,your design is so great,please come to share your thoughts about it.

author: tggzzz
author_rank: Super Contributor
timestamp: November 29, 2016, 09:37:11 am
content: Amd what service is your client asking you to do with those boards?

author: ansonbao
author_rank: Regular Contributor
timestamp: November 29, 2016, 09:44:32 am
content: Quote from: tggzzz on November 29, 2016, 09:37:11 amhe just receive the boards and said satisfied to our service

author: ataradov
author_rank: Super Contributor
timestamp: November 29, 2016, 11:14:57 pm
content: Quote from: tggzzz on November 29, 2016, 09:37:11 amHe is a PCBWay rep, and presumably someone asked to make those boards. The design is open, so no problem here.

author: ansonbao
author_rank: Regular Contributor
timestamp: November 30, 2016, 01:44:21 am
content: Quote from: ataradov on November 29, 2016, 11:14:57 pmthe design is open?next time i will try it

author: EEVblog
author_rank: Unknown
timestamp: November 30, 2016, 01:50:04 am
content: Quote from: ataradov on November 29, 2016, 11:14:57 pmUnless they go sell them with my name and logo on it.

author: ansonbao
author_rank: Regular Contributor
timestamp: November 30, 2016, 02:42:37 am
content: Quote from: EEVblog on November 30, 2016, 01:50:04 amHello,Dave,hope you everything is ok.The pcb design is by you?

author: ebclr
author_rank: Super Contributor
timestamp: December 05, 2016, 04:29:05 am
content: One more reason to avoid this suppler, they expose customers orders on public.
Interesting choice for a power supply design... - Page 1
Forum section: electronics / projects

author: ivaylo
author_rank: Frequent Contributor
timestamp: July 18, 2015, 04:25:02 am
content: So I picked up an anonymous piece of equipment (mostly to harvest those cool Bourns multiturn pots). I could tell it was a custom job, but judging by the exterior it seemed pretty nicely designed, pretty cool front panel and all. Nothing could prepare me for what was inside though... Designed by a Liberal Arts major is an understatement. A whole wall wart for a transformer (with all of it's output cable nicely coiled!)... A tiny 24V switch for a mains switch... All 110V solder joins hanging around bare... Two boards attached to each other with a single loose bolt... A piece a foam taped on the lid for "insulation"? Still keeping the Bourns pots, but I thought I'd share

author: TiN
author_rank: Super Contributor
timestamp: July 18, 2015, 05:07:12 am
content: Man, you broke it's calibration now since you open it!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 18, 2015, 05:22:01 am
content: Surprised they bothered to screen print it. Unless it was already something commercial, but that seems unlikely.My guess, it comes from a university and was a "grad student special", or it's test equipment from a small company or department that doesn't have QC procedures for their home-made equipment.Tim

author: Refrigerator
author_rank: Super Contributor
timestamp: July 18, 2015, 05:33:07 am
content: I guess it was someone's school project ? He/she made it look nice on the outside and as long as it works and you don't have to show the insides you should be good to go.

author: amyk
author_rank: Super Contributor
timestamp: July 18, 2015, 05:35:51 am
content: Any idea what it does? It doesn't look like there's much in it. Some sort of quack device?

author: SeanB
author_rank: Super Contributor
timestamp: July 18, 2015, 06:08:41 am
content: Keep the black painted copper strap holding the transformer as well, and the DVM modules as well.You could take some of those Chinese SMPS modules and mount them inside and make a nice 4 isolated output power supply as well.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 18, 2015, 06:21:14 am
content: It looks like some sort of I/O panel, probably for experimenting with stuff.

author: ivaylo
author_rank: Frequent Contributor
timestamp: July 18, 2015, 06:43:13 am
content: Yeah, some sort of education project makes sense come to think of it. But when I had to make those 25 years ago they were always looked at inside and out, on this one someone spent all the money for the outside...
interesting circuit : use DAC as Attenuator - Page 1
Forum section: electronics / projects

author: squadchannel
author_rank: Frequent Contributor
timestamp: April 04, 2025, 11:00:16 am
content: from the analog signal source circuit of the hp 3562A.signal is input to the VREF.U251 is AD7533 10Bit R2-R.on second thought, it is indeed possible.Much smarter than the precision resistors+analog switches that audiogeeks like.No, potentiometer is sufficient.I'm seeing this for the first time, is this a common circuit? are there any advantages or disadvantages?

author: moffy
author_rank: Super Contributor
timestamp: April 04, 2025, 11:17:38 am
content: Multiplying DACs have been used like this for quite a while, the R2R configuration is quite effective for this allowing reasonable BW up to a few MHz. The trick is the analogue signal is fed into the Vref which is then multiplied by the DACs digital input.

author: SiliconWizard
author_rank: Super Contributor
timestamp: April 04, 2025, 11:26:06 am
content: This wasn't uncommon, I remember it was even mentioned in the applications section of many DACs datasheets. Of course you would be careful not to exceed the max voltage for Vref.

author: squadchannel
author_rank: Frequent Contributor
timestamp: April 04, 2025, 11:30:26 am
content: more googling, it seems that multiplier DACs work differently than the microcontroller DACs I often use. Hmmm... I still don't know much about this.

author: squadchannel
author_rank: Frequent Contributor
timestamp: April 04, 2025, 11:55:41 am
content: mean that the ratio of the op-amp can be changed digitally?

author: moffy
author_rank: Super Contributor
timestamp: April 04, 2025, 09:54:09 pm
content: Quote from: squadchannel on April 04, 2025, 11:55:41 amThe opamp is providing a virtual ground for the switching resistors and just summing the currents which is proportional to Vref*DigitalValue.

author: Kleinstein
author_rank: Super Contributor
timestamp: April 05, 2025, 08:33:37 am
content: Quote from: SiliconWizard on April 04, 2025, 11:26:06 amThe MDACs can usually tolerate quite high ref. voltage, like +-10 V or even +-25 V for the AD7524. There are 2 limits: a hard one not to cause damage and a practical one where the errors get larger, e.g. from thermal effects and the switch resistance getting too nonlinear. Exceeding only the practical limit for a short time should be no issue.Usually the feedback resistor part should withstand the full swing of the OP-amps and the ref. input should withstand the same, at least as a damage limit.

author: radiolistener
author_rank: Super Contributor
timestamp: April 05, 2025, 12:42:50 pm
content: Quote from: squadchannel on April 04, 2025, 11:00:16 amYes, this is pretty common circuit, it is named DAC volume control
Interesting connection inside a cheapo smoke alarm - Page 1
Forum section: electronics / projects

author: 8086
author_rank: Super Contributor
timestamp: March 30, 2013, 02:58:07 am
content: So I bought a cheap smoke alarm as the battery had died in the one I had. I only bought it for the 9V battery, which was the cheapest option in the store, so I had a smoke alarm spare. Teardown time!I found an interesting design choice near the radioactive source/detector. There's a metal shield that connects directly to a pin on the DIP device next to it, without using the PCB at all. Both go through a hole drilled in the board and there appears to be something like a guard ring around the pins.I hadn't seen this before so I thought it might be of interest to some of you.http://imgur.com/a/GRGeW

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 30, 2013, 03:50:30 am
content: That's a high impedance connection. For it to work, leakage must be kept to a minimum.BTW, it's pretty easy to wire it to always be in an "alarm" state so you can use it as a nice buzzer. (Or just wire the piezo to a microcontroller.) Also, if you attach the radioactive element to a cheap webcam board, you can get a nice random number generator.

author: TerraHertz
author_rank: Super Contributor
timestamp: March 30, 2013, 03:53:58 am
content: Cute.For detection of ultra low current from that front electrode, to avoid surface creep leakage on the board, they eliminated the board!You see an equivalent scheme in other sensitive circuits, except using a teflon post to support a solder tag that has the critical circuit component legs attached.This way sure is cheaper!

author: amyk
author_rank: Super Contributor
timestamp: March 30, 2013, 08:06:38 am
content: Did they really try to scrape the part# off thateasily identifiableIC? Guard ring and the rest of the circuit look identical to the datasheet.

author: codeboy2k
author_rank: Super Contributor
timestamp: March 30, 2013, 10:36:55 am
content: Just don't go trying to scrape out that radioactive stuff more than necessary for just1random number generator.This guy was trying to make a reactor in his childhood, and as an adult was caught stealing smoke detectors.Likely he wanted to try again.from:http://www.foxnews.com/story/0,2933,299362,00.html
Interesting diode failure mode - Page 1
Forum section: electronics / projects

author: Prehistoricman
author_rank: Regular Contributor
timestamp: September 28, 2018, 06:34:51 pm
content: Story time.I was fiddling around with my guitar pedals when I realised that my vintage PSK DST-2 distortion pedal (schematic here) was really warm. It was so warm, in fact, that the sticky-back Velcro had detached from the pedal. I had to investigate.Under the highlighted brown patch was a diode. A reverse-polarity protection diode intended to short the supply if it's coming in in the wrong direction. I first spotted the diode not by the brown patch, but an intense burning sensation.This generic tester did not recognise the part. Let's do some analysis of our own...On the right you can see the normal diode characteristic but with a super strange reverse-bias one.This puppy was dissipating about 2 watts inside the pedal. I thought diodes failed short...?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 28, 2018, 08:50:26 pm
content: Cool, a partial failure. Probably burned through in a spot, causing a ~resistive characteristic?Would guess replacing it with a TVS or zener would be recommended.Tim

author: duak
author_rank: Super Contributor
timestamp: September 29, 2018, 07:36:24 pm
content: I remember finding a Zener diode that did something like this once. It was in a power supply and was supposed to regulate a voltage for a low level stage. I sort of recall it running hot so I replaced it with one with greater dissipation.If you look up "Zener zapping" you can see that with enough overcurrent, the junction can be completely shorted out. Apparently, the aluminum in the bonding pads diffuses into the silicon. I suppose if the Zener was operated just above its limit, over time enough aluminum atoms migrate and cause a parallel resistance while leaving the diode junction somewhat functional.Cheers,

author: Prehistoricman
author_rank: Regular Contributor
timestamp: September 29, 2018, 08:21:30 pm
content: Interesting!I suppose it could have been a Zener. I don't have any official schematic and the number on the package doesn't bring up any results (011AA).Replacing the diode has fixed a few odd behaviours of the pedal (sorry, Tesla, I just used a random diode that was lying on my desk). It used to turn on (engage the effect) after unplugging another pedal earlier in the chain. That's been happening for a very long time so I suppose it's been faulty (to a lesser extent) for an even longer time.
Interesting Diode issue with ACS712 - Page 1
Forum section: electronics / projects

author: Roze
author_rank: Contributor
timestamp: May 08, 2016, 06:08:19 pm
content: Hi,I'm designing a circuit to simply switch mains power on an off through wifi, yes I know it has been done before, but I felt like making my own.In any case, this circuit contains a ACS712 Hall effect sensor to measure amount of current drawn, mainly for determining broken lamps and stuff.Now to the problem, according to the datasheet, there is supposed to be a diode on the output when measuring AC (+a capacitor), and I have built up the circuit in Proteus Simulator to test it out.The output from the sensor is linear and 0-5V, with the rated +-5A sensing capability, that gives a 0-point around 2.5V and a -5A reading at 1.5V and a +5A at 3.5V, the output never goes negative, yet, without the diode (D1 in following schematic) the output is a sine wave, just like the input, but with the diode, its almost smooth.The people at IRC believes the Diode should not be there and just breaks things, and thus that the people who wrote the datasheet are idiots and that the simulation is also broken, therefore,I wonder, if/why does it work?Is not the Diode supposed to be having no effect when the voltage keeps positive?The 0-point became 2.27V after adding the voltage follower in the simulation, without it, I could not seem to scale the signal properlySchematic and Capture with Diode (D1). According to simulation, this method works for measuring AC:Schematic and Capture without Diode: (Corresponding Capacitor, C2, is also removed, since it had no major impact without the Diode)Excerpt from datasheet:http://www.allegromicro.com/~/media/Files/Datasheets/ACS712-Datasheet.ashx

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 08, 2016, 07:35:03 pm
content: Well, obviously, if you need a DC output corresponding to the AC level, you must rectify the signal.If you can do the rectification (and preferably, RMS too) in software, you're better off doing it that way. You will need a sample rate of at least ~1kHz to get enough points per cycle that the reading is reasonable. (Actually, you only need a sample rate as high as the polling frequency and required statistical accuracy. Smart meters, for example, often do equivalent time sampling, which saves on power. Since they only care about polling a few times a minute, to get an accurate measure over ~hours of duration, this is fine.)With only a volt or two of signal, a discrete diode is a pretty shitty solution, hardly qualitative even (i.e., is there a few amps of AC flowing or not?). I would recommend a precision full wave rectifier (op-amp pair and some diodes and resistors) for the analog solution, or a proper RMS converter chip.Tim (heh, I'm AFK from IRC this weekend)

author: moffy
author_rank: Super Contributor
timestamp: May 09, 2016, 12:06:01 am
content: To measure the AC without DC offset(Hall sensors have quite high drift figures) pass the signal through a high pass filter, e.g. cap/resistor then level shift and precision rectify as required.
Interesting dissertation on magnetic core materials, propagation/resonance - Page 1
Forum section: electronics / projects

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 02, 2024, 02:25:25 pm
content: Glenn R. Skutt, High-Frequency Dimensional Effects in Ferrite-Core Magnetic Devices:https://vtechworks.lib.vt.edu/server/api/core/bitstreams/af8749ec-eca2-4c3a-98a2-c20857b3fb1f/contentLots of experimental methods, measurements and simulations (for varying degrees of approximation/representation) relevant to design and use of ferrite materials.Tim
Interesting failure of 74 Series level shifter IC (74LVC8T245) - Page 1
Forum section: electronics / projects

author: tom66
author_rank: Super Contributor
timestamp: April 12, 2020, 05:15:05 pm
content: I have spent the last few days tracking down a frustrating problem with an FPGA SPI interface. The FPGA is the slave and a level shifter is used to shift up the 1.8V MISO signal to the 3.3V MCU domain.I was unable to determine why in some cases bytes of all zero would be read, and why some bit patterns (but not all) were received incorrectly. I thought it was a defect with the design of the SPI IP inside the FPGA. However the mystery was revealed when I tested the input and output of the MISO channel of the level shifter (the other direction of channels are shifted by another device.)The output has become very "latent" and is prone to noise, so much so that it was occasionally shifting bits into the next bit position at just 6MHz. The part is rated to ~6ns input-to-output delay in this configuration so should be capable of >50MHz data transfer without error. I originally suspected I might have mucked up and not connected the /OE or DIR pins, but I double checked these and resoldered the entire part with no change to its behaviour. Sometimes, the part would fail to work altogether, and other times I'd get erroneous transitions causing a "double edge" SPI data bit, which was particularly odd.Replacing the part fixed the issue. Parts were bought from Mouser.Has anyone else seen this failure before?In the below scope screenshots, dark blue is output, pink is input, and yellow is the SPI clock.
Interesting Grounding on TI EVAL Board - Page 1
Forum section: electronics / projects

author: ssashton
author_rank: Frequent Contributor
timestamp: February 08, 2023, 01:01:45 pm
content: I got hold of the project files for theTPA3244 TI EVALboard and I thought this was interesting enough to be worth a thread.On this board there are 4 audio line level inputs which are buffered by a couple of NE5532 op-amps run single-rail with a V-MID supply. They feed a class-D amp IC found in the middle of the PCB.What I find really interesting is they have chosen to route a separate trace for the audio input ground and connect the V-MID supply filter caps directly to it. This is then joined to the main ground planes next to the big amp IC.I wanted to know what you guys think of this?Is it some legacy thinking that audio should be 'star grounded' or does the designer know their stuff? (They work at TI they must be good, right?)It interrupts the main ground plane, but there are also ground fills on the other layers that tie across the routed trace. Kind of wondering if I should do similar on my own board.

author: dobsonr741
author_rank: Frequent Contributor
timestamp: February 08, 2023, 08:04:38 pm
content: It’s an input ground lift. Allows the other end of the input cable to define your GND and not to force ground current to go through your cable’s shield feeding the amp. Somewhere in between the differential and single ended input. Far worse than differential, might hear a bit better noise/hum performance.

author: ssashton
author_rank: Frequent Contributor
timestamp: February 08, 2023, 11:12:00 pm
content: I'm not sure I follow, can you explain in more detail please? The ground trace here is tied to the ground plane, so it's not lifted in terms of being floating or transformer isolated.

author: dobsonr741
author_rank: Frequent Contributor
timestamp: February 09, 2023, 01:41:18 am
content: You are right, it's not ground lift. Looks like star ground, if you found the two are directly connected on the gerber. I assumed there is a resistor between the input ground and the system ground. As in TI SLOA143, 5ohm Rgbk on page 2.

author: ssashton
author_rank: Frequent Contributor
timestamp: February 09, 2023, 11:10:57 am
content: Oh that's a nice document!Yes I think it is a star ground, but recently I had been reading a lot that star ground is an old design method and single ground plane should be used. So I thought it was unusual to see both here.
interesting manufacturer. linear systems - Page 1
Forum section: electronics / projects

author: sarepairman2
author_rank: Frequent Contributor
timestamp: February 01, 2016, 03:29:20 am
content: http://www.linearsystems.com/

author: calexanian
author_rank: Super Contributor
timestamp: February 01, 2016, 03:40:39 pm
content: Neat. I bet those "specialty replacement" parts are not cheap! But hey, at least somebody is making them.

author: Pjotr
author_rank: Frequent Contributor
timestamp: February 01, 2016, 04:45:41 pm
content: It's a small company that sources obsolete parts, mainly jfets. They serve niche markets like audiphiles and some research facilities. Price is very high compared to the original parts and performance often not up to the original (wider spread, higher noise).

author: Cerebus
author_rank: Super Contributor
timestamp: February 05, 2016, 12:07:55 am
content: Quote from: calexanian on 01 February 2016, 17:40:39The weird thing is that parts you can ONLY get from them are reasonably priced but parts that have second sources are priced really high - at least they are by their UK distributor. For instance:A linear systems only part:LS843 - closely (1 mV) matched monolithic dual JFET, very low noise (7nV/sqrt(Hz)) £3.64 1 off, £3.10 1000+A second sourced industry standard partLinear: SST4117 - Low leakage n-channel JFET £1.79 1 off, £1.31 1000+Fairchild: MMBF4117 - Low leakage n-channel JFET £0.198 50 off, £0.095 250+Yes, that's right £1.31 @ 1000+ for a part you can get at 250+ for £0.095 from RS (Not the cheapest supplier on the planet).

author: EagleTG
author_rank: Newbie
timestamp: February 07, 2016, 05:14:40 am
content: Hahah, I expected it to be the exact opposite of:https://en.wikipedia.org/wiki/Non-Linear_Systems(manufacturer of the Kaypro line of computers)...https://en.wikipedia.org/wiki/Kaypro

author: Vgkid
author_rank: Super Contributor
timestamp: February 07, 2016, 05:37:41 am
content: Looking at trendsetter.com(us distributor) the sst4117 is $2.15 , while the much more exotic 2n4117 in to-72 is $2.85.
Interesting Power Good Circuit? How does it work? (Lolin32/ESP32) - Page 1
Forum section: electronics / projects

author: awef
author_rank: Contributor
timestamp: August 22, 2017, 04:03:35 pm
content: I noticed an interesting circuit in the Lolin32 ESP32 schematic. I think it's trying to detect a USB brownout and force switch over to battery.But in general, I'm thinking... why does this circuit even exist? So..... Here's how far I got:+5V in this picture feeds a 3.3V LDO.+5V also goes to a P-Channel MOSFET which cuts off a battery when VBUS/USB +5V is present.So things are probably well even if we only get +4v?R2/R3 are pulldowns which activate the PNP transistors U2 (Left Qa PNP and Right Qb PNP).Q1 P-Channel MOSFET turns on if Gate = 0, so that requires pulldown R3 to be "active"In order for R3 to really be a pulldown to that would require Qb to be "off". That requires VE to be high. That can only happen if Qa is conducting to VBUS.Well... if VBUS is 5V and all is well, then the pulldown R2 turns on Qa, which causes VE => 5V. That turns off Qb, and R3 pullsdown causing Q1 to turn on. GoodHold on a second #1:So Qa turns on, and suddenly Qa Base/Collector/Emitter are all == Vbus? What does a PNP transistor do when all 3 pins are +X volts?Question #1:If VBUS is grounded to 0V, then Qa and Q1 can't turn on and disappear. Without anything for Qb Emitter, Qb turns off and goes away, and +5V is left floating??Question #2:If VBUS == Vbrown is in a brownout/undervolt condition, then I suppose we want Q1 to turn off quickly. Working backwards, Q1-Gate needs to get a high enough voltage of say 4V to turn off. How? Qb needs to conduct that bad voltage by turning on. That only happens if VE == 0, which allows say Vbrown to go through Qb and hit Q1G. So Q1is off now.But then with VBUS == Vbrown and VE pulling Qa Base to 0V, that would turn on Qa. That would put Vbrown on VE and turn Qb back off. That would have R3 pull VG back to 0v, turning Q1 back on?Curiousity A:Okay so strangely(?) Qa base and collector are connected together.. what does this mean?Curiousity B:It seems any time that Qb is on, that would turn Q1 off. So odd for Q1 to be "feeding its own death".Are you serious #1:So really we're looking for Vbrown to be "so low" that we can "just turn on Qa"... so that anytime Q1 turns on, Qb turns off Q1???Curiousity C:My mind is confused, but since both Base of Qa and Qb are connected together, if Q1 is on, Arent' Qa and Qb's operation kind of in lock step?Perhaps I don't understand fully #1:So... is this really an effective brownout detection circuit? Or is it more like a complicated/expensive pullup/down for the battery?
Interesting PSU short protection - Page 1
Forum section: electronics / projects

author: iMo
author_rank: Super Contributor
timestamp: January 07, 2019, 12:18:30 pm
content: Long time back (in the era of CB radio) I did a teardown of "NT35 13.8V/3.5A" PSU made by "Avanti".The PSU is of simplest design, but what was interesting to see was the "output short protection" design. None shunt sensing resistor was used.Schematics (except the bridge and filter caps) below shows the protection.The short 50Hz pulses are fed into the base of Q5.Under normal operation the Q5 is saturated (via R4/R5) thus there are no pulses at its collector (mind its collector resistor R6 is wired at the regulator's input side).When the PSU's output is hard shorted the Q5 works unbiased (the hot side of R4 is now near gnd level - the base is wired R4||R5 against gnd) and the 50Hz pulses propagate into the base of Q4.The pass transistor Q1 2n3055 is opened for about 200us at 50Hz when output shorted. Q1's power loss is therefore pretty small. In practice the Q1 wasn't noticeable warm when PSU's output shorted.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 07, 2019, 05:38:29 pm
content: Short protection, yes; but you need to get there first!This is a special case of a more generally known circuit, the foldback current limiter.Obviously, this is not brown-out protection (i.e., against a moderately heavy -- not shorted -- load), and peak output current will still be hFE limited(!).There are more clever ways to solve this problem -- that is, current sense without shunt. Monitoring the pass transistor's Vbe for example, usually as part of a dissimilar matched pair. This is hard to do in a discrete circuit, of course, and notoriously hard even in an IC, as the current limit ratings of many LDOs can attest.Tim

author: David Hess
author_rank: Super Contributor
timestamp: January 07, 2019, 09:33:48 pm
content: That is an awful lot of complexity just to avoid a sense resistor which could be used to make the regulator more stable. I wonder though if they did it that way so that the regulator could hard start into a difficult load; fold-back current limiting can have problems with this if it is misapplied. Some early integrated voltage regulators had the same problem when hard starting into a heavy load if their thermal protection was tripped; the solution was to add hysteresis.Old discrete fixed voltage designs, unlike the 723, often used a separate differential pair to measure the voltage across the current shunt so the voltage drop could be much lower than 1xVbe, roughly 0.6 volts, yet yield high accuracy. From that, adding fold-back current limiting typically took just one more resistor.

author: iMo
author_rank: Super Contributor
timestamp: January 07, 2019, 11:13:25 pm
content: 723 PSU with the similar "impulse foldback protection":https://www.elektronik-kompendium.de/public/schaerer/ntifb.htm
Interesting Sensors - Page 1
Forum section: electronics / projects

author: Sebastian
author_rank: Regular Contributor
timestamp: February 17, 2014, 03:15:40 pm
content: I have to build a PIC µC based "multimeter" at school. The sensor part has to be 1x1 in and is connected to 5 I/O pins of the controller and two of them can be used with the integrated 10bit adc. The supply voltage is 5V so i can not really use more than that.So I am looking for interesting sensors or other stuff i could measure. I was thinking about a coax cable length meter that applies a fast rising edge to a open ended coax and then measures the reflection but the PIC is clocked at 4MHz so one instruction cycle is 1µs which means I can not measure short enough times to do that. Of course I could jut make a voltmeter, currentmeter, thermometer or something like that, but I would like to do something more challenging so I am looking for ideas. Keep in mind I only have 1 by 1 inch of double sided PCB .

author: Rudane
author_rank: Regular Contributor
timestamp: February 17, 2014, 05:26:38 pm
content: With the coax you'd need more than 100 meters to get your time of flight signal. How about a photodiode that measures the amount of ambient light and turns on an LED when the amount of ambient light is too low. This would also require some level of hysteresis so the LED didn't turn on and off sporadically near the threshold value. It might also be tricky to remove the effect of the LED's light on the photodiode. Maybe you'd have to consider physical placement options.

author: SeanB
author_rank: Super Contributor
timestamp: February 17, 2014, 06:00:24 pm
content: Use one pin to drive an IR led with 200mA pulses ( 1% duty cycle) and use the 2 inputs to read 2 photodiodes, and make a proximity sensor that is sensitive to direction of approach. The remaining pins can be used to drive a LED with PWM to give an indication of range - off when far growing bright when something approaches the board. The LED will need good decoupling to keep the noise injected into the ADC input low.
Interesting watch project on Dangerous Prototypes - Page 1
Forum section: electronics / projects

author: reagle
author_rank: Unknown
timestamp: June 09, 2013, 12:53:07 am
content: I bet Dave will like this one- I stumbled on it on their forums:http://dangerousprototypes.com/forum/viewtopic.php?f=56&t=5417

author: alank2
author_rank: Super Contributor
timestamp: June 09, 2013, 01:02:32 am
content: That is pretty cool. Ahhh, someday I'm going to see how small I can build a watch with a HP-DL2416.

author: reagle
author_rank: Unknown
timestamp: June 09, 2013, 01:08:15 am
content: Hmm, now I want to make something with that display
Interesting Yihua Hot Air Station. - Page 1
Forum section: electronics / projects

author: PeterG
author_rank: Frequent Contributor
timestamp: January 03, 2023, 09:22:03 pm
content: Hi All,i found this some time ago and there seems to be very little in the way of reviews.https://www.aliexpress.com/item/4001365858636.htmlI am curious what you think about this hot air station. In principle it would be useful for small MSD parts and the slim pencil design would feel less 'chunky'. But it seems i bit expensive for what it is.Pete

author: wraper
author_rank: Unknown
timestamp: January 03, 2023, 09:34:12 pm
content: Expensive and not very practical. You want a more powerful hot air station even for small parts on multilayer PCBs like computer motherboards.

author: jpanhalt
author_rank: Super Contributor
timestamp: January 03, 2023, 09:43:36 pm
content: Why not just choke down the output of a cheaper knock-off station like the 8582D for less than $100?

author: nctnico
author_rank: Super Contributor
timestamp: January 03, 2023, 09:49:13 pm
content: I agree with wraper: 200W isn't enough for hot air. Even with a 700W hot air station I need a hot plate for some jobs

author: wraper
author_rank: Unknown
timestamp: January 03, 2023, 09:55:53 pm
content: The problem is not with power rating as such. Airflow is much more indicative of how useful/powerful it's in practice. If heater is not powerful enough for airflow it has, station simply won't be able to keep high air temperature. Extra heater power without higher airflow is only good for faster heat-up to set air temperature. As this station has no airflow spec given, I assume it's very low.

author: wraper
author_rank: Unknown
timestamp: January 03, 2023, 10:02:45 pm
content: I noticed it has transport screws on the bottom. So most likely is has a diaphragm pump which also is an indication of low airflow. Diaphragm pumps also give pulsating airflow which is able to blow away small components at much lower average airflow than stations with blower fan.

author: PeterG
author_rank: Frequent Contributor
timestamp: January 03, 2023, 10:08:10 pm
content: Quote from: wraper on January 03, 2023, 10:02:45 pmI did not get professional vibes from it. But i have been curious about it. Given there are no clones i figured something was not rite.Thank you for your input everyone.Pete
Interface 3.3V Logic to 5V High Speed Bus? - Page 1
Forum section: electronics / projects

author: hal9001
author_rank: Regular Contributor
timestamp: May 26, 2021, 10:39:41 am
content: I want to interface a FPGA (3.3V IO) with a 64 bit bidirectional bus running at 10 MHz bus clock. Normally this isnt a problem and can connect the FPGA directly and change the tristate modes but here the bus voltage is 0-5V. Hows the best way to do this?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 26, 2021, 11:44:08 am
content: 5V CMOS, not TTL?There are bidirectional bus interface level translators out there. You'll need a bus direction signal, which, you probably have already because what use is a parallel bus without it.Tim

author: Nominal Animal
author_rank: Super Contributor
timestamp: May 26, 2021, 12:48:00 pm
content: Perhaps four74ALVC164245s would work for you?

author: hal9001
author_rank: Regular Contributor
timestamp: May 27, 2021, 08:57:39 am
content: Quote from: Nominal Animal on May 26, 2021, 12:48:00 pmCheers!
interface between the stm32f103rbt and cdb4344 - Page 1
Forum section: electronics / projects

author: elecdesigne
author_rank: Newbie
timestamp: November 11, 2017, 03:11:36 pm
content: hihow is the interface between the stm32f103rbt and cdb4344 ?I dont know how to canect pin togethers.mcu does not have i2s

author: elecdesigne
author_rank: Newbie
timestamp: November 15, 2017, 06:20:46 am
content: HiHow to connect cdb4344 to spi ?

author: Jeroen3
author_rank: Super Contributor
timestamp: November 15, 2017, 06:52:52 am
content: You can't connect that DAC to an STM32F103 since it does not have I2S. Get a chip with I2S.However, you could emulate single channel I2S using SPI and bit banging. With ST a SPI frame is limited to 16 bit.Success not guaranteed.