hybridfree/eevblog-posts huggingface dataset:
Safe to have Bluetooth board over signals or ground plane? - Page 1
Forum section: electronics / projects

author: rea5245
author_rank: Frequent Contributor
timestamp: December 03, 2014, 01:11:33 am
content: Hi,I'm laying out a PCB for my latest project and it includes an HC-05 Bluetooth transceiver module, which includes a copper trace that acts as an antenna. My question is, is it OK (i.e. it won't hurt the RF reception or transmission) if there are signal traces running beneath the HC-05? How about if there's a ground plane under the HC-05? None of the signals would be high speed - less than 1 kHz.Thank you,Bob

author: rea5245
author_rank: Frequent Contributor
timestamp: December 03, 2014, 03:04:16 pm
content: Thank you, evb. The HC-05 datasheet - such as it is - says nothing about the antenna. But TI has an application note about Bluetooth antennas (http://www.ti.com/lit/an/snoa519b/snoa519b.pdf) and it says of printed antennas: "Printed and surface-mount antennas have certain common properties. Area around and beneath the radiating element must be kept copper-free. The ground plane must be placed on one side of the radiating element."So that's my answer.- Bob

author: Jeroen3
author_rank: Super Contributor
timestamp: December 03, 2014, 03:15:30 pm
content: Two traces parallel to each other will form a capacitor.Two traces/planes under each other will form an even better capacitor.Two long strips with some insulator coiled up will form a radial capacitor.On Vcc this won't be much of an issue, but at 2.4 GHz the effect is different.

author: Howardlong
author_rank: Super Contributor
timestamp: December 03, 2014, 04:01:22 pm
content: In addition, even if you strip the copper, be aware that having extra the dielectric of any substrate like FR4 will affect the radiation pattern. As has been suggested, always follow the documentation for this sort of stuff, they will have had these modules in expensive RF anechoic chambers. There will often be recommendations on where to place the antenna WRT the board enclosures too. if not, always have it on the edge of the PCB, and that edge ought to be close to an RF aperture (ie, not in the middle of a conductive case, but at an end with plastic, that's what the black plastic areas are on iPads etc).

author: Neilm
author_rank: Super Contributor
timestamp: December 03, 2014, 07:21:26 pm
content: I have used some modules that did not mention anything about the layout requirements in the datasheet. Hence, the first project too use in the company could barely talk to the PC beside it.Later I found some app notes on the website that gave some patterns for where the module could not have any metal (trace, screw or what ever). The result being that the next project could happily reach over 8 meters.Neil
Safe way to apply voltage on output of buck converter? - Page 1
Forum section: electronics / projects

author: llkiwi2006
author_rank: Regular Contributor
timestamp: December 11, 2019, 03:36:13 pm
content: I am doing a design with supercaps for power backup and I'm using a LMR14030 buck converter to charge the caps. I am worried that the ic is not designed to have power applied to the sw pin. I added a diode (D5) to vin to prevent current leaking back into the input rail, and I am using the en pin to disable the ic until vin is higher than the maximum voltage on the supercaps. Will this work fine?
Safe way to get 3.3 logic levels out of a Siglent SDG1032x generator - Page 1
Forum section: electronics / projects

author: cncjerry
author_rank: Unknown
timestamp: December 05, 2022, 08:26:03 pm
content: Subject says it all. I have the SDG1032x, upgrade to the higher frequency. I need 3.3v logic level signals and I need it to be safe. I was thinking of squaring it and putting it into a Schmitt trigger but was wondering if it was necessary. I was thinking of setting the max output level and then using an offset?Thanks

author: cncjerry
author_rank: Unknown
timestamp: December 05, 2022, 09:21:15 pm
content: I never noticed before that you can set the high value and low value for the amplitude. What threw me though, was the high value reads 3vpp when I have the low value at 0v. But when I set the maximum output, I have to set it to 6v to get 3V output. 2nd issue I found is that when I change the output levels, it seems to go back to a bipolar signal (ac coupled +/-). I was using this thing the other day and I blew the regulator on one of those small power supplies that plugs into a breadboard. I assumed it was because the generator started putting 1.5 negative volts on the ground - that's what I'm trying to avoid. I'm thinking diodes to couple it? Thoughts? I could also just transformer couple it to a squaring circuit and then rebuild the signal using a schmitt trigger.Thanks

author: Ian.M
author_rank: Super Contributor
timestamp: December 05, 2022, 10:30:18 pm
content: What frequency range do you need at logic levels, and are you driving CMOS logic?If its not too high and you are driving CMOS logic, you could try a potential divider between the sig. gen. output and your +3.3V rail. Set up the generator for 6.6V Pk-Pk symmetrical about Gnd, and if the potential divider uses equal resistors, you'll get 0V to +3.3V swing at the divider tap. 2x 10K would do well enough for low frequency work. At higher frequencies you'll probably need to go down to 1K resistors, and if you are pushing even further into the MHz region you'll probably need a few pF or even tens of pF across the resistor between the sig. gen. and the divider tap to speed up the edges by compensating for the input capacitance of the logic gate and other strays.However beware of reflections in your output leads transiently doubling the voltage at edges - you may need to terminate them with a matched resistance to ground at your target circuit, which is likely to affect the output level.

author: nctnico
author_rank: Super Contributor
timestamp: December 05, 2022, 11:15:00 pm
content: Well, there is always 50 Ohms in series with the output. A zener diode will do just fine for protection.
Safely measure DC voltage for MCU - Page 1
Forum section: electronics / projects

author: mitrynicolae
author_rank: Contributor
timestamp: December 27, 2018, 06:06:09 pm
content: Hello everyone!I need your help in designing the input circuitry before the ADC of the MCU. The design should meet the following requirements:1. the allowed input voltage should be between 0 and 25 volts2. the output voltage should be between 0 and 5 volts3. it should be as linear as possible4. it should protect the MCU ADC for unexpected failure (input should not get to ADC pin by any means; In my design I was using an op amp buffer)5. it should have a reverse polarity protection (it's a must)6. it should have an over voltage protection(it's a must). If by mistake the operator of the device inputs 30v instead of 25 maximum the circuitry should survive without issue. A value above 25V will be read as 5 volts. Also if the erroneous voltage disappear from the input, the circuit should recover by itself.7. it should use as few components as possible8. it should not use dedicated ICs (maybe already exists)9. it should have a compensatory adjustment in case some components don't exactly match the specifications (plus or minus 20%) (it's a must)10. the supply voltage for the circuit will be 5V max.I have come with the following schematic. Please analyze it and let me know if there is anything wrong with it (except the high power consumption on the input which I already know.)P.S. Please note that the op amp used is actually MCP6022 (but that part does not exist in my simulation tool.)

author: Kilrah
author_rank: Unknown
timestamp: December 27, 2018, 08:25:35 pm
content: Resistive divider with high enough values and software cal...

author: max_torque
author_rank: Super Contributor
timestamp: December 27, 2018, 10:15:46 pm
content: First question, what is your required measurement bandwidth or sampling rate? if you have a low bandwidth (say 1Khz / 2ksps or lower) then it's trivial to arrange a resistive divider with suitable diode or zener clamping to achieve these aims (ie no active circuitry)
Safety capacitor identification - Page 1
Forum section: electronics / projects

author: punkieys17
author_rank: Newbie
timestamp: October 27, 2023, 08:39:53 am
content: Could anyone tell me the size of this safety capacitor. Its across the input of a heating controller. Everything measures ok - it just seems to have exploded and shorted the external fuse. No other markings. Can find the 565-1Y but the 1nM is throwing me. Sorry for asking such a dumb question but I grew up with pin through the hole and uF etc.

author: Shonky
author_rank: Frequent Contributor
timestamp: October 27, 2023, 09:04:52 am
content: 1nFY Class250VM = 20% tolerance

author: wraper
author_rank: Unknown
timestamp: October 27, 2023, 09:07:37 am
content: It does not like there is anything wrong with this capacitor and something else let out magic smoke nearby it.

author: punkieys17
author_rank: Newbie
timestamp: October 27, 2023, 09:13:25 am
content: Thank you. The tell tale was the black burn mark behind it - nothing else in the area and the back blown off. It feeds live/neutral into a discrete component bridge rectifier which checks out and there is good resistance between live and neutral as connected to the circuit. Not sure what would cause such a failure - it was sitting leant over above the tracks so wonder if it just shorted somehow. Many thanks for your help.
Safety cutoff circuit troubles - Page 1
Forum section: electronics / projects

author: Pentoad
author_rank: Regular Contributor
timestamp: December 26, 2019, 02:52:43 pm
content: I am designing a system where a relay is turned off for some time when a voltage is present at the input pin. When the voltage is present, C1 is discharged and the relay switches off as it's meant to. The only issue I'm struggling with is when the circuit is powered up for the first time, I have to wait about a minute for the capacitor to charge and the relay to switch on. How would I change the circuit so that C1 is charged once when the circuit is powered meaning that I don't have to wait for it to switch on?

author: MiDi
author_rank: Frequent Contributor
timestamp: December 26, 2019, 09:13:35 pm
content: As a starting point:There are a couple of issues with this, can you figure out which?Any ideas to fix the issues?

author: mk_
author_rank: Regular Contributor
timestamp: December 26, 2019, 10:06:39 pm
content: Quote from: Pentoad on December 26, 2019, 02:52:43 pmat least polarity of Q2 is not how it should be...

author: Pentoad
author_rank: Regular Contributor
timestamp: December 26, 2019, 10:17:01 pm
content: Easyeda seems to always give me upside down transistors and I forgot to flip it.Quote from: MiDi on December 26, 2019, 09:13:35 pmI can't help you without a description of your problem.
Safety Grounding of Large Instruments - Page 1
Forum section: electronics / projects

author: leonhart88
author_rank: Regular Contributor
timestamp: February 10, 2019, 07:28:12 pm
content: Hi All,I have a general "best practice" question about grounding of large instrumentation. In the past, when I've built enclosures or sub-systems out of 8020 and aluminum or powder coated steel panels, I've always attempted to ground all panels & metal parts (eg. using PEMs on the steel panels, and biting washers on the 8020 extrusions with grounding wires).You can imagine that for a large instrument, this can start to become a ton of work with lots of little tooth washers and nuts, etc. One can also imagine that various parts of the instrument will never have high voltage components inside of it and that the high voltage components can be isolated into one section of the instrument.In said system, there's one inlet connector for 120V AC going into a AC/DC power supply and then low voltage DC (24-48V) is broken out to various sensors & actuators inside.My question is, is it best practice to ground every single metal item in this instrument? Or is it adequate to simply limit the area in which the live AC wires could touch during a fault and only ground that subsection? For example, if the AC wiring is confined to a small sub-section of the 8020, is it adequate to just ground the extrusion & panels around that area? Alternatively, if the AC wiring enters an enclosed box (like a junction box) immediately and the AC/DC converter is located inside of said box, with only 24-48V DC exiting the box, do any external panels need to be grounded at all since the box will prevent a fault from touching external metal components?Note that I'm just curious about this as a best practice, however if there are applicable standards for general instrumentation, I would be interested to know details on those as well.Thanks everyone!
safety of Chanies line to 3.3 v converter - Page 1
Forum section: electronics / projects

author: johanan
author_rank: Newbie
timestamp: January 03, 2016, 06:38:47 am
content: I wonder if any one tested these small , very low cost converters for safety.http://www.aliexpress.com/item/5PCS-Lots-AC-DC-Power-Supply-Buck-Converter-Step-Down-Module-3-3V-500mA-SG231-SZ/32423033877.htmlWhile the price and size are very attempting, I don't have the equipment to test how well isolated they are. I don't care much about EMI for my hobby projects, but safety is another story.Johanan

author: Ian.M
author_rank: Super Contributor
timestamp: January 03, 2016, 06:56:30 am
content: Its a cheap chinese PSU. The only way to tell for certain is to Hi-Pot test then tear one apart and measure all the clearance and creepage distances, including those for the inter-windng insulation of the transformer. However the track running under the optocoupler on the back of the board compromising the creepage distance isn't a good sign.

author: johanan
author_rank: Newbie
timestamp: January 03, 2016, 01:42:50 pm
content: I will be happy to see Dave doing a video on this

author: djQUAN
author_rank: Frequent Contributor
timestamp: January 03, 2016, 02:18:29 pm
content: Quote from: johanan on January 03, 2016, 01:42:50 pmIf you are looking for a vid on one specifically on the supplies you bought then get some sent to him for a 2min teardown. If you just want to see cheap powersupplies torn apart, Bigclive has some in his channelhttps://www.youtube.com/user/bigclivedotcom/videos
SAIA PCA1 restoration + making programming console - Page 1
Forum section: electronics / projects

author: Bendba
author_rank: Regular Contributor
timestamp: August 27, 2016, 01:08:36 am
content: Hi,Here is something I've been working on for a little while. I have two plc's, SAIA PCA1 (made in Switzerland)They are really good machines (I used to have three of them with the programming console but they somehow got lost), I've been playing with them a few years ago.They are built around a 8085 processor.Those two units I have now are coming from ebay. I bough then because they were cheap. One is working (when powered, whatever rom is in it is doing whatever it is programed for)I attached some photo of the other unit, which is not working. I took it apart and still have to find the problem (I suspect the power supply)I'm planning on reverse engineering it so I can modify and/or make my own I/O cards (they sell for around $100 a piece, too much for me)But I have three major issues.1. I don't have the book with the language anymore, it's some sort of basic, you don't program it in assembler.2. I suspect the second unit also has a defective Basic Rom (uv eprom) because when I put it in the working unit, it seems to do some random stuff for a split second and then freezes.I would like to find a valid copy of that rom. If I can't, I'll make a copy of the other, hoping it's 100% good.3. I don't have the programming console anymore (reference is SAIA PCA2.P05) and I wouldn't mind being able to reproduce one. There is one for sale on ebay but it's for over $2000I did contact SAIA Burgess but didn't get any answer, I'll try again.The other thing is that I am a bit hesitant about how much I can put online when I reverse engineer it, I don't know where is the limit when it comes to patents; if there is still a valid one on that device.If anyone has some informations, it'd be very helpful.Thanks
Saleae Logic 16 - Page 1
Forum section: electronics / projects

author: dan3460
author_rank: Frequent Contributor
timestamp: June 05, 2017, 09:10:02 pm
content: This project has several I2C peripherals but I only have implemented one and worked with no problems. I just added 2 more modules with two different addresses. These two modules are initiated just before than the older one that I had. I set up my logic analyzer to see was going on and to make sure that the MCU was talking to modules, the logic analyzer showed no problems, then I looked at the older module and with disgust I saw that the stops and starts were in wrong location. I commented out the new modules from the program and reload it into the MCU, no problems with the old nodule. Added the new modules, problem with the old module. I thought that I have made a mistake on the programing of the new modules. I've included a picture of this problem. Something was weird as I can recognize the start sequence and looked ok to me, I went to see if it was something wrong with the I2C setup, without changing anything came out of the setup and averithing was ok, starts and stops in the correct position. Attached is a picture of that.As anyone encountered similar problem? Is there a solution?

author: mubes
author_rank: Regular Contributor
timestamp: June 05, 2017, 10:36:36 pm
content: Do you have any i2c buffers in your system? I have had worlds of trouble with those...if so look very carefully at the permitted DC offsets ... They are much lower than you might expect and if you exceed them you _do_ get troubles.Dave
Saltwater, meet sensor - Page 1
Forum section: electronics / projects

author: theatrus
author_rank: Frequent Contributor
timestamp: June 18, 2014, 01:28:39 am
content: My faithful commercial aquarium controller from the past ten years did something funny: the temperature element railed at 121F. The temp sensor was at fault, but there were no obvious problems. The sensor element is a fully encapsulated, with no visible seams, silicone wire affair with an element at the end of the wire.As an exercise, I tried to find out where the fault in the cabling was - there were no water intrusion signs anywhere along the cable until I hit the end. The attached picture is the tiny sensing element which has clearly seen better days. I can't tell if the corrosion somehow entered the encapsulated end...Just a reminder that water, and especially salt water, is pretty darn nasty stuff.

author: retrolefty
author_rank: Super Contributor
timestamp: June 18, 2014, 01:42:42 am
content: In most industrial installations the temperature sensors are installed inside 'thermowells' which is just a tube closed at one end that is inserted into the media to be measured, such that the sensor is never subjected to the actual media being measured.http://2.bp.blogspot.com/_ZNZ7m9tKOBk/TT_J15ARKKI/AAAAAAAAAD8/zJG25-GOOPY/s1600/A%2BThermowell.jpgSo did you end up with any 'floaters' ?

author: theatrus
author_rank: Frequent Contributor
timestamp: June 18, 2014, 01:48:59 am
content: No floaters in this case - I have enough redundancy setup, but ended up with the chiller and heaters both turned on fighting each other for at least 12 hoursLuckily their own internal thermostats worked fine and temp only dipped to 78F.

author: Mechatrommer
author_rank: Super Contributor
timestamp: June 18, 2014, 04:51:09 am
content: ten years in saltwater is pretty good! how much the sensor cost was?
Salvage parts out of a few racks of PowerEdge servers - Page 1
Forum section: electronics / projects

author: iceisfun
author_rank: Regular Contributor
timestamp: March 06, 2014, 11:21:31 pm
content: I have a few racks worth of pull PowerEdge gear and it seems that the PSUs out of these things have some pretty neat stuff in them.Is it worth tearing these apart? It seems pretty hard to do with a iron, the board is thick and hard to heat up.I have about 20 machines, maybe more all pulled working and I do not have any need for old servers.

author: houdini
author_rank: Regular Contributor
timestamp: March 06, 2014, 11:39:35 pm
content: The power supply's are more useful as a unit. You can usually hack them to use as a high current 12v supply.

author: Monkeh
author_rank: Super Contributor
timestamp: March 06, 2014, 11:51:08 pm
content: How old are these servers?You may not need them, but others might be able to use them.

author: Swake
author_rank: Frequent Contributor
timestamp: March 07, 2014, 08:44:32 am
content: Hack one of the servers for the fun and experience. The supply is certainly a good place to start looking for parts, but not the only one.Sell the other servers for cheap and a quick win, eventually in parts such as disks and motherboards, with the money you can buy the components you really need for your projects.

author: true
author_rank: Frequent Contributor
timestamp: March 07, 2014, 06:39:17 pm
content: I know something interesting you can do - give them to meHow old are they? Probably not much you can do that's interesting with old servers.

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 07, 2014, 07:54:22 pm
content: What size are the cases and are they standard ATX? 4U and larger rack server cases that accept ATX motherboards are really useful for building workstations in. (The smaller cases generally won't fit video cards and are nowhere as useful. But an ATX-compatible 2U that has a PCIe riser able to fit a 2 slot video card would be very valuable!)Assuming the machines are too old to have much practical use, the PSU (if ATX compatible) and cooling fans are good to salvage for reuse as-is. The motherboards often have a lot of caps and MOSFETs that are reusable. Heatsinks are always nice to salvage, both big and small.

author: JimmyM
author_rank: Regular Contributor
timestamp: March 11, 2014, 12:46:23 am
content: Quote from: true on March 07, 2014, 06:39:17 pmYou, sir, have a gift for sarcasm.

author: The_Penguin
author_rank: Regular Contributor
timestamp: March 11, 2014, 01:08:37 pm
content: Quote from: Monkeh on March 06, 2014, 11:51:08 pmIndeed. I have 4 Dell 1950s in production as hypervisors, yet I see tons of them for sale by "recyclers" for $200.00 or less.
Salvaged ic's - Page 1
Forum section: electronics / projects

author: electronics technician
author_rank: Regular Contributor
timestamp: March 23, 2021, 11:34:00 pm
content: What's the most amount of ic's yall ever salvaged in 1 go

author: Ground_Loop
author_rank: Frequent Contributor
timestamp: March 27, 2021, 03:19:49 am
content: That's about what I retrieved from some abandoned computer thing more than 40 years ago with a butane torch and a pair of pliers. They were nearly all 74xx logic chips. I still have many of them to this day.

author: retiredfeline
author_rank: Frequent Contributor
timestamp: March 27, 2021, 04:17:04 am
content: I used to recover TTL ICs from computer boards with a paint stripper hot air gun. Melt the solder then whack the board on the edge of box. Used to get 20-50 chips in one go. I'll probably never use up that hoard. :-(

author: David Hess
author_rank: Super Contributor
timestamp: March 27, 2021, 08:46:32 pm
content: We replaced a wire wrapped S-100 disk controller which was all TTL and included an Intel 8008. I seem to recall that it had 186 ICs, and I did not even have to desolder them.
Salvaged SMPS to bench supply - Page 1
Forum section: electronics / projects

author: RubiconJoe
author_rank: Newbie
timestamp: October 19, 2014, 01:20:18 am
content: I salvaged what seems to be a pretty high end switch mode power supply. It is rated for 12V DC, 5A. Aside from trying to reverse engineer it to see how it works, I would also like to convert it into a variable bench supply for my lab. It is a relatively small unit and think it would be perfect for my bench.What would be some things to consider for re-designed/modifying this supply?

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: October 19, 2014, 01:41:27 am
content: What's pretty high end about it? Looks like a bog standard supply to me. And what's to reverse engineer? It's not the warp core from the Enterprise. There are so many resources out there on how these things work.Here's what you need to consider:http://www.ebay.com/itm/Variable-DC-Lab-Bench-CV-CC-Power-Supply-0-18-VDC-0-3-Amps-NEW-/161442719954?pt=LH_DefaultDomain_0&hash=item2596bc68d2and move on. You won't be able to even get just an enclosure with two posts going for that price.There's no point anymore in building stuff like this yourself.And let's not even get started about a newbie tooling around mains voltages. That sticker and silkscreen were there to warn *experienced* people!IMO, YMMV, etc.

author: RubiconJoe
author_rank: Newbie
timestamp: October 19, 2014, 02:23:14 am
content: Thanks for your input Alex. It was just an idea I had when I came across it. Maybe not such a good one...

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: October 19, 2014, 02:28:19 am
content: Quote from: RubiconJoe on October 19, 2014, 02:23:14 amHere's some consolation though: those Chinese supplies will probably require some incoming inspection, ie, "take it apart!".Keep your supply in your bin though.

author: Richard Head
author_rank: Frequent Contributor
timestamp: October 19, 2014, 06:03:51 am
content: What is a little different though is those thick film solder-in modules. I suspect those are the control circuits and there's no SMD stuff under the board.
same capacitance,same class,same voltage rating,different package characteristic - Page 1
Forum section: electronics / projects

author: electronx
author_rank: Regular Contributor
timestamp: December 08, 2023, 11:12:26 am
content: The same capacitance has the same class at the same voltage rating. However, the capacitor package are different. Will the characteristics be different?I usually wouldn't pay any attention to this, but I found this information. Is this only valid for class 2 and class 3 caps ?

author: Kleinstein
author_rank: Super Contributor
timestamp: December 08, 2023, 12:13:09 pm
content: This is mainly a thing with class 2 MLCCs. The drop in capacitance with small relatively high capacitance X7R and similar is well known. The smaller 0805 part has thinner dielectric and thus getting the drop earlier. They may also opt. for a higher µr material that is more sucesptible to saturation.The voltage rating with ceramic caps is sometimes not a really hard limit, but more a test limit on how much testing is done. So the same parts could also be tested a bit stricter and sold with a higher voltage rating (e.g. 16 V) - this could well work with the 1210 size, but for the 0805 size one may have more failing the test.

author: TimFox
author_rank: Super Contributor
timestamp: December 08, 2023, 03:00:19 pm
content: The non-linear behavior of Class-II dielectrics is a property of the material itself, and therefore depends on the E-field (voltage gradient = dV/dx) in the material, not the total voltage across the entire slab of ceramic.Larger packages can have substantially higher thickness, thus reducing the E-field for a given total voltage.

author: MarkT
author_rank: Frequent Contributor
timestamp: December 08, 2023, 11:19:00 pm
content: The materials that exhibit super-high dielectric constant (1000's to 10000's) are all ferroelectric (BaTiO4 is the best known), and ferroelectrics are highly non-linear, very sensitive to temperature and microphonic (i.e. piezoelectric). Ferroelectricity is named by analogy with ferromagnetism and has nothing to do with iron.

author: aeg
author_rank: Regular Contributor
timestamp: December 08, 2023, 11:36:32 pm
content: Go to the cap vendor's website and look up the characteristics graph (not the datasheet) for the individual part number.

author: CosteC
author_rank: Regular Contributor
timestamp: December 10, 2023, 11:03:59 am
content: Two caps with same capacity and voltage and material may vary in C vs DC and C vs time (ageing) curves. Real voltage withstand will also differ, but this is usually not important.
same capacitors on both main board and daughter board? - Page 1
Forum section: electronics / projects

author: carl0s
author_rank: Unknown
timestamp: May 12, 2018, 11:12:44 am
content: Hi. I'm attempting to build an LCD TFT display daughter board for the stm32l4r9i-discovery board (MIPI DSI).I am basing it off the schematics of the included AMOLED daughter board.One thing has confused me a bit..There are 100nf capacitors on 3V3_LCD and VDD_LCD (CN4 pins 36 and 38) of the main board itself (housing side of the connector).But the same capacitors are showing on the schematic for the same pins on the daughter board / LCD board (CN1, mating plug).Is it likely that this is just an oversight in the schematics? i.e. it only needs to be on one or the other? Or is this some kind of good practice for circuit design?Here is the relevant bit of the main STM32L4R9I-DISCO board schematic:and here is the screen daughter board schematic:I suppose I could just try to check if they are present on both boards, but, some of these things are minuscule and I may struggle to identify them

author: carl0s
author_rank: Unknown
timestamp: May 12, 2018, 11:18:19 am
content: I just noticed C6 is the same too. Is it to do with putting them closer to the thing drawing power?

author: carl0s
author_rank: Unknown
timestamp: May 12, 2018, 11:21:48 am
content: I just used my brain and checked the silkscreen. All those caps are present on both board.

author: David Chamberlain
author_rank: Frequent Contributor
timestamp: May 12, 2018, 11:25:36 am
content: Its a good enough rule that each design assumes the other card has no decoupling.

author: carl0s
author_rank: Unknown
timestamp: May 12, 2018, 11:30:22 am
content: Quote from: David Chamberlain on May 12, 2018, 11:25:36 amI see, thanks, and are they more effective if they are closer to the power source or drain, rather than in the middle near the connector? Just wondering why C6 is added as close to the LCD as possible (it's right next to the tiny LCD FPC connector on the daughter board), while C1 and C2 on the daughter board are as close to the big board to board connector as possible, and C52 and C53 are the same (close as possible) but on the main board side.

author: voltlog
author_rank: Regular Contributor
timestamp: May 12, 2018, 12:22:37 pm
content: decoupling is most effective when placed as close as possible to the device drawing power.

author: David Hess
author_rank: Super Contributor
timestamp: May 12, 2018, 04:52:11 pm
content: The connector has inductance which when combined with a capacitor on either side decouples in both directions; think of it as a pi filter. Usually I would expect a large capacitance on the load side and a small capacitance on the source side but 0.1uF is actually pretty large. Decoupling on both sides also minimized loop area which would otherwise radiate or pick up EMI.
Same Pro Electron type Designation for Transistors from multiple Manufacturers - Page 1
Forum section: electronics / projects

author: euzer
author_rank: Regular Contributor
timestamp: November 27, 2018, 04:44:55 pm
content: I'm curious in when the same Pro Electron type designation (More specifically, the reuse of the 3 digit serial number) is used for transistors from multiple manufacturers. For example, many manufacturers offer a BC817 NPN transistor, and I'm wondering what the significance of this is.Could it be that one manufacturer is initially granted the type designation, and then others license the design and use equivalent processes and lithography stencils to fabricate a clone of the part, with hopefully similar characteristics. The design rights may expire after a period of time and it become public domain for anyone to produce.Another option is that secondary companies design a new device from the ground up to mimic the characteristics of an already allocated serial number. Alternatively a company has an existing device in its portfolio that has similar characteristics to an existing device, like a BC817, so just badges it as that and offers it to the market.

author: David Hess
author_rank: Super Contributor
timestamp: November 28, 2018, 02:43:38 am
content: It is the second one; other companies produce an equivalent which meets the registered specifications. Which means if you design a circuit which relies on an unspecified behavior, using the same transistor from a different manufacturer may be problematical. This can also be a problem if the original manufacturer changes processes.

author: euzer
author_rank: Regular Contributor
timestamp: November 28, 2018, 09:27:04 am
content: Thanks for the response.Is there anyway or where to find out who the original sponsor with Pro Electron (or EECA) is for a specific type number, and also the registered data/specifications for that part?
Sample Frequency and Bit Resolution Demonstrator Box 1989 test teardown - Page 1
Forum section: electronics / projects

author: oz2cpu
author_rank: Frequent Contributor
timestamp: September 05, 2022, 08:17:06 pm
content: I know you are going to like this onehand made in 1989 for a school / education location in Denmark,it really works and is fun to play with, only minor detail is it would love to get a new input level potmeter.BNC on the back is Sample Freq out 5V TTL levels, very usefull too (8.1 to 47kHz)https://youtu.be/dtnrPs3PIGg
Samsung MLCC ? Is it good compared to other big brands ? - Page 1
Forum section: electronics / projects

author: BravoV
author_rank: Super Contributor
timestamp: February 20, 2014, 05:18:49 am
content: Going to purchase smd MLCC caps, browsing at few online distributors show Samsung is relatively cheaper than other established brands like Taiyo Yuden, TDK, AVX and etc.I'm not looking for military grade cap, just for general purpose, is it decent ? or good enough ?Just don't trust ebay or aliexpress that have tons of these which I doubt if they're genuine or re-labeled crap.

author: Dago
author_rank: Frequent Contributor
timestamp: February 20, 2014, 06:46:50 am
content: I've never heard of a ceramic cap that would have failed so I guess they are fine. Since they are already specified for change of capacitance over temperature range (last letter in the code eg. X7R, means it is specified for +-15% capacitance change over the temperature range of -55 ...125C) I can't see what else could be wrong with them. Unless your using them for something very specific.Anecdotally I've personally always bought the cheapest ceramics (often times Samsung) and never had any problems or even though I could have any problems due to that

author: georges80
author_rank: Frequent Contributor
timestamp: February 20, 2014, 06:56:07 pm
content: I have used Samsung MLCC capacitors on some of my LED driver boards, they perform well and to spec. Samsung is a BIG brand...The only time I'd be very careful choosing a capacitor vendor is for critical areas (input/output) filtering where 10uF/22uF/47uF size ceramics are used (often several in parallel). For those areas the ESR and voltage de-rating specs become very important and just choosing X5R or X7R is only one of the important parameters.Often, testing is required to determine how the capacitor behaves in such a situation - especially long term reliability. The long term reliability is an important issue (that many times only becomes apparent after a product has been out for several months or years) that often overrules switching to a different and lower priced device... In this case best to stick with the product that is proven.If you are just tinkering, then that's a different story.cheers,george.

author: BravoV
author_rank: Super Contributor
timestamp: February 21, 2014, 12:25:38 am
content: Thanks for the replies, Samsung then.Yes, I'm aware of the capacitance de-rating vs working voltage, planning to use minimum at >= x2 at rated voltage since size doesn't matter.
Samsung MLCC "Product for POWER application" meaning? "Test (SPL) ClassⅡ"? - Page 1
Forum section: electronics / projects

author: tinfever
author_rank: Regular Contributor
timestamp: March 10, 2023, 05:01:06 am
content: Does anyone know what the difference between these two Samsung MLCCs could be?CL31B106KQHNNN -https://product.samsungsem.com/mlcc/CL31B106KQHNNN.doCL31B106KQHNFN -https://product.samsungsem.com/mlcc/CL31B106KQHNFN.doThe only difference I can see is that the different letter in the PN (NNN vs NFN at the end) indicates "Product for POWER application" according to the spec sheet. However, they appear to have essentially identical characteristics otherwise.Looking at the second page of the spec sheet I do see one the "power" MLCC has the text I marked between *** added.Bending StrengthJudgement:Capacitance change: within ±10%Test condition:Bending to the limit (1mm) with 1.0mm/sec. ***Outgoing test (SPL) ClassⅡ: 2mm***I'm guessing this means the "power" MLCC has additional bending tests done at the end of the production line? What does SPL Class II mean though?I see Samsung has a MLCC reliabilitiy level option of "Normal Capacitors_High Level Ⅱ" but neither of these part numbers fall in to that category in the Samsung MLCC catalog.https://www.samsungsem.com/resources/file/global/support/product_catalog/MLCC.pdfThoughts?
SAMSUNG MOBILE PHONE BROKEN GLASS REPLACEMENT - Page 1
Forum section: electronics / projects

author: MrsR
author_rank: Regular Contributor
timestamp: August 19, 2012, 01:16:13 pm
content: Hi Guys!My son wants me to replace the front glass on his Mobile Phone.He has the new glass Face which has heat sensitive glue for reattachment.Does anyone know the correct temperature that is required to remove the old plate and the replacement Temp to attach the new one.Also should I use an air heat gun or infrared heat.Rachael

author: StubbornGreek
author_rank: Frequent Contributor
timestamp: August 19, 2012, 06:59:22 pm
content: Quote from: MrsR on August 19, 2012, 01:16:13 pmI've done a few but can't give temps; I've found that the adhesive they use in these isn't consistent (different give), so I've kind of developed a feel for it. Use a large nozzle on your hot air tool and keep it moving at a decent distance (set to about 200c). After a few attempts (use suction tool), you'll notice the adhesive start to 'give'. Just don't concentrate heat in one location for too long and careful, the glass obviously gets hot.

author: saturation
author_rank: Super Contributor
timestamp: August 19, 2012, 09:11:19 pm
content: This can help, the temp is generally as he discusses, about 50-70C right at the phone.

author: MrsR
author_rank: Regular Contributor
timestamp: August 21, 2012, 11:00:10 pm
content: Thanks good peoples.Got the old glass off125c as low as my H.Air gun would go and a Teflon coated ceramic Knife (didn't heat up) so no burnt digits.Surprising bit was how easy it was to pull down.I fixed my daughter's Mobile last year and it all clipped together and was a real pain.Again thanks for the advice this has to be the best Electronics FORUM around must be because it's AustralianRachael

author: StubbornGreek
author_rank: Frequent Contributor
timestamp: August 22, 2012, 04:54:32 am
content: Quote from: MrsR on August 21, 2012, 11:00:10 pmI've found Samsungs a lot easier to work on than most, especially Apple products (I find myself scratching my head sometimes with those guys thinking, 'why?').

author: SeanB
author_rank: Super Contributor
timestamp: August 22, 2012, 04:04:02 pm
content: Apple, designed to be easy and fast to assemble, but not a repairable item at all. Basically a use and toss item with a massive price tag.

author: StubbornGreek
author_rank: Frequent Contributor
timestamp: August 22, 2012, 05:22:27 pm
content: Quote from: SeanB on August 22, 2012, 04:04:02 pmPretty much sums it up...wash and repeat.
Samsung S 5 Neo (Softwhere Upgrade  Question) - Page 1
Forum section: electronics / projects

author: Kilroywashere
author_rank: Regular Contributor
timestamp: September 22, 2020, 10:18:05 am
content: G903f is the number i see when i look up upgrading the s5neo .. I am worried I might brick it cuz I have the g903w.... anyone know stuff about rooting and such before I brick this great phone

author: retiredcaps
author_rank: Super Contributor
timestamp: September 22, 2020, 05:34:01 pm
content: According to lineageos sitehttps://wiki.lineageos.org/devices/s5neoltesupported modelsSM-G903FSM-G903MSM-G903WIf you are worried, look at youtube videos and tutorials on how to install custom roms.Needless to say, backup all your files before attempting an install.
sanity check 3000W voltage limiter  - Page 1
Forum section: electronics / projects

author: qwaarjet
author_rank: Regular Contributor
timestamp: November 29, 2014, 09:15:48 pm
content: I have been working with a Sorenson SFA constant current power supply. The SFA has great current control but no voltage limit, normally this wouldn't be a problem but the device I'm trying to test start open circuit and then has diode like tendances after a plasma is formed in it. The problem is a I want to bias the device to ~140V prior to plasma formation. At first I tried a resistive preload that would disconnect when current was detected flowing to the DUT this has proven to be unreliable.The ideal device (I think) would be a 140V zener diode that could dissipate the 2800W need to bias the system prior to start and then it would stop conducting as the voltage dropped due to the DUT taking the current instead. the problem is I have not seen a zener with those specs. so a I came up with the attached schematic using high power P MOSFETs to dissipate the power. The system seems to work in SPICE but are there any real world problems that might arise?I'm planing on water cooling the FETsThermal drift on the zeners should not be major concern so long as the voltage stays within +-10V

author: Marco
author_rank: Super Contributor
timestamp: November 29, 2014, 09:38:15 pm
content: How fast does the plasma take over after you turn the current source on? Eyeballing it, the SOA for 140V/5A is about a 50ms pulse.

author: qwaarjet
author_rank: Regular Contributor
timestamp: November 29, 2014, 11:46:57 pm
content: Quote from: Marco on November 29, 2014, 09:38:15 pmmany seconds thought 10A is the usually operating point 20A is a fault casedidn't even look at that part of the data sheet assumed if total was under the devices rating it would be ok.however going by this equationPd = [TJ (max) – TC] / ZthJC = VDS IDI should be just within limits at room temp and my water supply is at least 10C cooler than that.
Sanity Check: ESD protecting a thermistor - Page 1
Forum section: electronics / projects

author: Pack34
author_rank: Frequent Contributor
timestamp: August 09, 2018, 07:42:27 pm
content: Just as a sanity check, isn't it typically a bad idea to attach an ESD TVS diode array to an input thermistor? I could have sworn I've seen some of these essentially float the data line when there's no load. For something like this, would you just put a zener and a polyfuse on the input thermistor net for protection so that the circuit protection wouldn't be able to influence your temperature reading? The zener would be rated above the maximum voltage across the thermistor to protect from voltage spikes and overvoltage events and the poly would do the same for overcurrent.Or am I over thinking this?

author: thm_w
author_rank: Super Contributor
timestamp: August 09, 2018, 10:24:02 pm
content: Schematic would help.I assume you are trying to protect the input circuitry of whatever is reading the thermistor. Series resistor and capacitor would be fine in most cases, unless you need very fast thermistor response.The line would be pulled down or up with a resistor similar to the thermistors value, which would prevent it from floating.https://electronics.stackexchange.com/questions/39531/is-this-an-rc-filter

author: Pack34
author_rank: Frequent Contributor
timestamp: August 10, 2018, 12:38:15 pm
content: The ESD protection is an LCDA15Chttps://www.semtech.com/uploads/documents/lcda15c_6.pdfThe thermistor is used as feedback for a UC3909 lead acid battery charger. The ESD protection chip is used just after the connector and before the battery charging chip.https://www.ti.com/lit/ds/slus239/slus239.pdfGiven that the ESD IC isn't an active component like the MAX3202 I used to use, I think this could be a non-issue. Just trying to be thorough.https://datasheets.maximintegrated.com/en/ds/MAX3202E-MAX3206E.pdf

author: thm_w
author_rank: Super Contributor
timestamp: August 10, 2018, 09:11:10 pm
content: Leakage for the Max3202 is 1nA and for the LCDA15C is 5uA (at 15V). Temp might read a bit lower than actual depending on what resistance the thermistor is and if leakage is similar at lower voltages.May not be significant.

author: floobydust
author_rank: Super Contributor
timestamp: August 10, 2018, 09:50:29 pm
content: Consider your lowest battery temperature. The thermistor is 10K @25°C B25/85=4073 and at -40°C it's high at 360k ohms. So very little TVS leakage current could make it read wrongly high temperatures and undercharge. I guess it depends how hot the TVS is on the charger board.I use shielded cable for the thermistor run, and careful it is insulated and cannot touch the battery terminals. You can get melted traces and drama.Filtering from AC hum I use a large capacitor across the thermistor, it also attenuates an ESD hit.
Sanity check for my battery pack board layout - Page 1
Forum section: electronics / projects

author: roli
author_rank: Regular Contributor
timestamp: November 17, 2021, 10:47:01 pm
content: Hi!Not too long ago I was asking for advice in selecting a battery management/protection IC. In the end I settled for Maxim MAX17320. A bit more details on what the end goal is:https://www.eevblog.com/forum/projects/selecting-a-battery-managment-ic-for-my-project/new/#newBut basically this is the smart battery pack board design for an old Sony aibo - small robot dog. Basically it's meant to replace battery packs that are no longer available.The board is designed to work with two 18650 lithium cells. The maximum current that the robot can draw is about 2A. The board is designed to fit in the limited space available and is meant to be hand soldered. Most of the passive components are 0402 size (except the ones marked).The design is based on these two Maxim examples and the info from the datasheet:https://datasheets.maximintegrated.com/en/ds/MAX17320G1EVKIT-MAX17320X2EVKIT.pdf(page 30)https://www.maximintegrated.com/content/dam/files/secured/design-tools/software/7331/maxrefdes179-schematic.pdf(page 3)https://datasheets.maximintegrated.com/en/ds/MAX17320.pdfDoes anyone see any issues with this board layout or schematic? Have I missed something? I am mostly worried about the upper right corner of the schematic and it's implementation because I am lacking some knowledge in how this is supposed to work exactly.