hybridfree/eevblog-posts huggingface dataset:
Passive switching to battery when paralleled USB power is disconnected - Page 1
Forum section: electronics / projects

author: PP3331
author_rank: Contributor
timestamp: August 29, 2020, 04:50:41 pm
content: I know there are some chip-based solutions to this, but I'd prefer doing it passively if possible. The power feeding into a USB input can be supplied either by the associated USB cable from a computer, or, when that cable is disconnected, from a battery source that is connected in parallel. I would like to find a way to switch between the two without using a physical switch. That is, the battery will only feed power to the USB input if the USB cable is disconnected, and the battery will not be involved when the USB cable is connected. Thanks.

author: Peabody
author_rank: Super Contributor
timestamp: August 29, 2020, 05:15:59 pm
content: You can connect each power source to the load through a Schottky diode. Then the source with the highest voltage will power the load. The other diode will be reverse-biased, so no current will flow through it. This assumes the battery voltage is less than the USB 5V.If you want to eliminate the diode voltage drop in the battery line, you can use a traditional load sharing circuit, which is one diode, a P-channel mosfet, and a resistor. The attached circuit shows a battery charger being used, but it should work the same if there's no charger. USB voltage, if present, turns off the mosfet, which isolates the battery. Otherwise, the gate pull-down resistor turns on the mosfet. The orientation of the mosfet is a bit unusual, depending on how you look at it.

author: PP3331
author_rank: Contributor
timestamp: August 29, 2020, 06:03:02 pm
content: Thanks. I had been considering using Schottky diodes that way, but am a bit concerned about leakage current back into the (lipo) battery.

author: David Hess
author_rank: Super Contributor
timestamp: August 29, 2020, 06:51:27 pm
content: The leakage current through schottky diodes is typically insignificant as far as a battery is concerned.The common alternative where lower voltage drop and/or lower leakage is required is to use "active" rectifiers made from power MOSFETs which are switched on or off to select the source.

author: PP3331
author_rank: Contributor
timestamp: August 29, 2020, 07:07:47 pm
content: Thanks very much.
Password to restore Options on the Advantest R3131A - Page 1
Forum section: electronics / projects

author: Tony_T
author_rank: Newbie
timestamp: March 07, 2017, 02:39:26 pm
content: Thought I should share this very useful information on how to restore Options like the Tracking Generator / Frequency Span Lower Limit which have become disabled after the NVram battery has failed / been changed.This information was posted yesterday on the Advantest group by 'wschraml' and is not my own.. but I've seen many R3131A owners asking for this info in the past and believe it wasn't readily available before. So I thought it warrants posting elsewhere.To restore your Tracking Generator / Lower frequency span and perhaps other 'Options' to the Advantest R3131A do the following:-<Shift> <9>Password: 882323 <Hz> (882323 seems to be the default PW)Change the “A Type” option to “On”“Exit”Tony

author: cncjerry
author_rank: Unknown
timestamp: November 13, 2018, 08:33:48 pm
content: I am going to kick this back open to make sure it is all in one place.I noticed today that my R3131A wasn't holding the settings and I assumed the battery was dead. I also checked the TG for the heck of it and I have an error 802 at power on, might have been 820, but it talks about the TG not being leveled. If I go into the setup code as mentioned below and re-activate the TG, the error goes away.Anyway, thanks again for posting this information as it saved my TG.Jerry
Paste and stop for exposed pad with vias - Page 1
Forum section: electronics / projects

author: okw
author_rank: Frequent Contributor
timestamp: May 28, 2025, 12:08:58 pm
content: I'm seeking recommendations for paste and stop layers for chips with exposed pad and vias in the PCB.If the manufacturers recommended land pattern is 3 by 3 squares (0.63x0.63mm each) with vias between, and the chip has a solid exposed pad (3.7x3.7mm), what's the best practice for paste and stop layers? I'm using the ESP32-C3.My first thought was to put a single stop (3.15x3.15mm as I need some room for the VDD trace) under the chip, and paste just around each of the 9 recommended pads (0.63x0.63mm). But that might be too big soldering area for too little paste, and it might flow all over the exposed pad and not bond very good)? Also the possibility that the solder flows through the tented vias (which will be exposed without soldermaksk).My second idea was to put individual stop and paste for each of the 9 squares. It might help a little, as the criss-cross soldermask between the PCB pads won't attract the paste. But could still be a problem.I've attached the recommended land pattern from espressif, along with my stop layer and paste layer.Any insights here?

author: okw
author_rank: Frequent Contributor
timestamp: May 28, 2025, 05:43:17 pm
content: Here are the stop and paste layers (hatched).
pata connectors and sockets - Page 1
Forum section: electronics / projects

author: srscricket
author_rank: Newbie
timestamp: February 06, 2014, 09:55:07 pm
content: Anyone have an idea on what the pata sockets on motherboards are called?

author: NiHaoMike
author_rank: Super Contributor
timestamp: February 06, 2014, 10:08:45 pm
content: They're just pin headers with an alignment cage.

author: hlavac
author_rank: Frequent Contributor
timestamp: February 16, 2014, 06:07:57 pm
content: Try IDC headers

author: free_electron
author_rank: Super Contributor
timestamp: February 16, 2014, 06:52:11 pm
content: box headers
Pattern Prohibited Area - Page 1
Forum section: electronics / projects

author: electosleepy
author_rank: Contributor
timestamp: August 18, 2016, 02:56:04 am
content: For the recommended land pattern in the linked component there is a pattern prohibited area. Does this mean that I need to remove the copper in the specified area?https://www.amphenolcanada.com/ProductSearch/drawings/AC/1140084168.pdf

author: Monkeh
author_rank: Super Contributor
timestamp: August 18, 2016, 10:39:35 am
content: I'd say so. It looks as if the contacts can actually touch the board in those areas.

author: Phoxtane
author_rank: Regular Contributor
timestamp: August 19, 2016, 02:34:37 pm
content: Quote from: Monkeh on August 18, 2016, 10:39:35 amShouldn't the board's solder mask protect from that issue? Unless OP is making the boards at home without a solder mask...

author: Monkeh
author_rank: Super Contributor
timestamp: August 19, 2016, 02:37:59 pm
content: Quote from: Phoxtane on August 19, 2016, 02:34:37 pmSolder mask vs several thousand abrasion cycles. Solder mask loses.
paypal - Page 1
Forum section: electronics / projects

author: electros6
author_rank: Regular Contributor
timestamp: November 12, 2013, 04:20:46 pm
content: First of all sorry to post this in the project section.I am from India. I like to purchase some FPGA board form ebay.comI have VISA debit card , but doesn't allow to pay through debit cardI tried entropay virtual card but not work .Please somebody tell me how to purchase from ebay. pleaseeeeeeeeeee

author: Clint
author_rank: Regular Contributor
timestamp: November 12, 2013, 04:34:20 pm
content: I think you will need a voltage regulator and 2 operational amplifiers. Can you make you own PCB's, have you tried boiling your credit card in animal fat? is so try vegetable oil.User given a 3 day "cooling" period to just sit back an admire how other forum members get along quite well without crossing too many lines all at once !

author: kaz911
author_rank: Super Contributor
timestamp: November 12, 2013, 04:37:04 pm
content: Quote from: electros6 on November 12, 2013, 04:20:46 pmContact a Freight Forward company that purchase it for you. You pay them with bank transfer or credit card - and then they buy it for you and have it shipped to india for you even if the seller does not ship directly.www.myus.comdoes such services and many others. But remember they do take 5-10% for offering the service.

author: ElectronicAllsorts
author_rank: Newbie
timestamp: November 12, 2013, 05:50:04 pm
content: Are you trying to pay through paypal without making a full verified account?if so its best to make a full account and go through all the verification, ebay sellers can choose not to accept orders if the buyer is not using a verified account with confirmed address. Its a pain but worth it in the end to have a fully functional paypal account.Also you could try emailing the seller to see if they ship to your location as again sellers can choose to not sell to some parts of the world and that could be the reason you cant orderIndia post is well known to be really bad at losing things so many ebay sellers wont play as it not worth all the grief, but some may make an exception if you ask nicely.

author: Simon
author_rank: Unknown
timestamp: November 12, 2013, 06:08:54 pm
content: you can usually put a visa card through paypal without an account, i do it often, that means that the seller may still be protected. I have to get proof of postages for everything I send overseas as royal mail won't pay up otherwise. I guess they have agreements with counterparts in other countries

author: gotvolts
author_rank: Contributor
timestamp: November 13, 2013, 03:52:25 pm
content: As a business paypal user, i see this problem come up quite a bit for my international customers.9 times out of 10, the issue is that the shipping address the customer provides at check out is different than the billing address of the credit card. Due to paypal's fraud preventative measures, you will be unable to check out successfully if this is the case.
PC board defluxing and washing - Page 1
Forum section: electronics / projects

author: calexanian
author_rank: Super Contributor
timestamp: December 10, 2013, 03:31:42 am
content: I have been looking for a solution for years. Perhaps somebody out there already has it. We need a way to deflux, and also clean boards that some back in for service. As it is now we just use flux off, or other such chemicals but it is rather wasteful. Years ago we could use vapor units but California no longer allows them. I have been trying to think of some contraption that would wash the boards, then I could distill the dirty solvent back out. Perhaps under vacuum to reuse the cleaner. Any thoughts? We still use RA flux in most of out products, and have for 34 years...

author: gbyleveldt
author_rank: Contributor
timestamp: December 10, 2013, 06:28:47 pm
content: This:http://www.electrolube.com/products/cleaning/detail.html?pid=26&section=1and 3 minutes in an Ultrasonic cleaner. Rinse, dry, done.And after 80 boards over a one month period it still seems rather effective, although there's a fair amount of gunk forming at the bottom of the cleaner

author: calexanian
author_rank: Super Contributor
timestamp: December 10, 2013, 10:26:52 pm
content: Thanks for trying but that product is not available in the U.S.and dose not meet our local environmental requirements (The most stringent in the entire world to be exact here in the San Joaquin valley.)

author: nctnico
author_rank: Super Contributor
timestamp: December 10, 2013, 10:33:41 pm
content: Bio-ethanol works OK for removing flux. Simple Green works great for cleaning dirty boards.

author: mazurov
author_rank: Frequent Contributor
timestamp: December 10, 2013, 10:47:16 pm
content: Hot IPA combined with ultrasonic bath. If your rosin is badly burnt, like after lead-free rework, some mechanical cleaning with old toothbrush may be necessary on fine-pitch parts. I use two 30 min. runs in 60-70C ultrasonic - first using 70% USP grade grocery store IPA (which can be used several times), second with 99% IPA (which can also be used several times depending on what you're making). Compresses air cleaning and toothbrush between 1st and 2nd runs. Works very well. You can recover IPA with simple distillation setup using very little electricity; this is also a way not to drain lead into the sewer, if you're still using lead in your process.

author: Napalm2002
author_rank: Regular Contributor
timestamp: December 11, 2013, 04:04:56 am
content: I know a guy who works for NASA that says that they clean their boards with straight everclear. Ie pure grain alcohol. I was also told that a big company used to put their boards in a dish washer...

author: calexanian
author_rank: Super Contributor
timestamp: December 11, 2013, 05:13:37 am
content: The hard part will be reusing the fluid. Some kind of distillation method will be required every now and then.
PC board - high speed multichannel data pattern generator - Page 1
Forum section: electronics / projects

author: cio74
author_rank: Regular Contributor
timestamp: March 18, 2016, 07:09:41 pm
content: Hello,I am wondering if anyone around has experience with PC DIO boards to generate parallel data patterns, say 32-96 bits at a time at a 1MHz+ speed. Any recommendation and things to look for while working with such boards?Thanks.IC

author: pelule
author_rank: Frequent Contributor
timestamp: March 18, 2016, 07:46:41 pm
content: Which PC bus interface you plan to use (PCIe or PCI)?There are BUS interface chips available to adress IOs via PIC/PCIe - for example IDT, NXP, Texas Instruments and Avago.I am not sure, if the PC bus is fast enough to generate a 1 MHz clocked pattern countinously (which I assume is required).In that case the pattern can be stored in a buffer RAM on that card and a binary counter to count the pattern at the required speed. With this solution also higher clock speeds are no problem.You may want to use a dual ported RAM if you like to change the pattern without disturbance of the running pattern. (This is in pinciple the opposit of a very simple logic analyzer).An example for the PCI bus you find here:https://www.google.de/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&uact=8&sqi=2&ved=0ahUKEwjF_O3P_crLAhVEvxQKHTh2AngQFggrMAI&url=http%3A%2F%2Felectronicdesign.com%2Fdsps%2Fchip-connects-pci-bus-local-bus-or-parallel-port&usg=AFQjCNF9y-pFWRcf1KPvX-Rmg-omfrg5DQ&bvm=bv.117218890,d.ZWUBRPeLuLe

author: cio74
author_rank: Regular Contributor
timestamp: March 18, 2016, 08:19:25 pm
content: Thank you for your reply, I currently have a few boards and some have been already tested. The ones with an isolated output won't be able to match the requirements for speed. The non-isolated one claims 100Mhz+ transfer rate. I take that's the rate on all channels not individual.The boards I am talking about are PCI, the 100MHz one has a 32Mb buffer. It makes sense since PCI bus is slower than claimed rate.http://www.dynamicc4.com/download/spec/pcidio32_datasheet_english.pdfI would assume I just send data patters and then trigger (software) the output. Have to see about setting the correct rate. Good thing it has memory, can use it from Windows, generate software accurate timing would have been a pain.The thing is, I have no experience working with them, not sure what should I look out for.
PC coolant expansion - Page 1
Forum section: electronics / projects

author: artag
author_rank: Super Contributor
timestamp: July 18, 2024, 09:07:02 am
content: I'm building a system that uses warm circulating water to keep a constant temperature.I've allowed for a pump, heater, filter, reservoir and a partitioned expansion chamber as used in hot water systems. But I may make a smaller one using PC watercooling parts and it made me wonder - how do they allow for the coolant to expand as it warms up ? I don't think they're generally open, and while some pump types have a reservoir that might trap a bit of air it seems like you'd at the very least need to carefully bleed it after moving.Or are they so small that a few bits of flexible hose will take up the slack ?

author: Phil1977
author_rank: Frequent Contributor
timestamp: July 18, 2024, 11:58:30 am
content: A few bits of flexible hose and a few unavoidable air/gas bubbles do the trick.Some better systems have a pressurizer or use little balls of compressible balls.
PC front panel audio/usb panel circuit - Page 1
Forum section: electronics / projects

author: Agony
author_rank: Contributor
timestamp: March 26, 2013, 05:25:35 pm
content: So new case - and annoying front panel noise.Wiring and mobo itself ok - and as always its the front panel itself:The headphone/mic jack ground is same with the USB - no wonder there is noise.So in theory i could phsically isolate the jacks from usb. EAch jack shares common ground and has 2 conenctiosn for left/right.But as a result with it separated from the usb fails - the sound is quiet and weak (as if it somehow depends of usb GND instead?) any ideas?

author: hammil
author_rank: Regular Contributor
timestamp: March 26, 2013, 05:31:03 pm
content: It's all the same ground system. The entire PC will be mains-earth referenced. Do you have an oscilloscope? Do some measurements at various points along the signal path - from the motherboard to the jack - under different conditions.

author: Agony
author_rank: Contributor
timestamp: March 26, 2013, 05:42:16 pm
content: unfortunately no osc available so no way to really probe anything.Tho the audio jack should have separate gnd pin - why would it connect it through the usb cable.Unless they used soem off the shelf common parts and just jacked the connector to it.The 3 pins right above the large connector for each jack dont look like they are for just structual. gonna crack it open again and see the pins on the mobo side connector.

author: c4757p
author_rank: Super Contributor
timestamp: March 26, 2013, 05:45:44 pm
content: That board looks very familiar... I swear my PC's case has the same little board and I had to replace the piece of crap USB jacks that were on it. And I have some horrifically nasty noise as well. Pathetic... I never bothered to do anything with it - just connected to the rear port instead. But I do have a scope or three. Maybe I'll have a look at it for you later.

author: Agony
author_rank: Contributor
timestamp: March 26, 2013, 05:52:27 pm
content: yeah looks liek a standard bpard - it even has the ground 'connections aroudn screw hoels - even tho the screw attach to the plastic case.The HD pinout standard has a gnd pin. So i dont see why would it be linekd to the USB GND.Just dont want to jack it out again (they decided to hide it behind front panel, closed with 6 screws -_- in annoyign hard to reach spots) - specially since i get my solder station back in a few days i wouldbt be able to do much rewireing.Yeah back works - but if you use headsphones and speakers.. .one jack on back isnt enough.

author: c4757p
author_rank: Super Contributor
timestamp: March 26, 2013, 06:02:10 pm
content: Quote from: Agony on March 26, 2013, 05:52:27 pmLuckily for me, my speakers have a wanky little control pod that sits on the desk and has a headphone jack. Maybe you could build something like that temporarily?
PC keyboard (101 keys) decoder IC row and column map? - Page 1
Forum section: electronics / projects

author: Jester
author_rank: Frequent Contributor
timestamp: April 14, 2018, 03:46:05 pm
content: Is there any sort of standard definition of which keys are mapped to which rows and columns?My google searches are yielding nothing of value.

author: Ian.M
author_rank: Super Contributor
timestamp: April 14, 2018, 05:03:03 pm
content: I wouldn't expect there to be any standardisation as there have been many generations of MCUs used as the in-keyboard encoder chip, with varying I/O port capabilities and almost invariably with propitiatory closed source firmware, so it all comes down to what's the cheapest matrix layout to make a flat-flex set of contacts for, which is dependent on interference from structural elements o9f the keyboard case, and thus the artistic desisign, then they realocate between columns/rows and I/O pin swap to make it happen.
PC Motherboard power-diagnostics tool - Page 1
Forum section: electronics / projects

author: IamSynthetiC
author_rank: Regular Contributor
timestamp: September 25, 2020, 05:41:18 pm
content: Hi, recently a friend of mine contected me with a "burnt" motherboard. While i was troubleshooting i got the idea for a device that would measure Current, Voltage and Status signals the PSU gives to the motherboard.I had some time to kill so i started working.My design has :Hull Current SensorsIntegrated -12V,12V,5V and 3.3V rails for standalone use (without PSU)Power SupervisorAC-DC Converter2x 18650 Batteries for portable useIntegrated BMSHere is the EasyEDA link: (It is still a Work-in-Progress)https://easyeda.com/marioskritikakis/atx-current-meterOne thing i am having trouble with though, is finding a reasong to build it. I am not sure this device would benefit me in troubleshooting. What do you thing ? And what do you think of the design ?Thanks
PC pin / socket receptacle manufactures - Page 1
Forum section: electronics / projects

author: b177
author_rank: Contributor
timestamp: January 24, 2025, 06:46:50 pm
content: Hi,I am looking for alternative MFGs to MillMax PC Pin / socket receptacle, specifically series 8369.https://www.mill-max.com/products/pin-receptacle/receptacle-with-standard-tail/8369This part, the socket accepts 1mm diameter pin, and has a 0.76mm tail. I have combed through DigiKey and Mouser for Manufactures and review all of their offerings. The closest I found was Preci-Dip, which is generally lower cost than MM, but they do not have sockets that accept 1mm pins.I've also looked at LCSC, hoping to find a lower cost Chinese brand but didn't find anything.Any suggestions / leads / places to search, etc?Thank you in advance.

author: henmill
author_rank: Contributor
timestamp: January 24, 2025, 07:03:30 pm
content: Have you tried Harwin? They make a lot of similar receptacles to Mill-Max. Might be pricey though.https://www.harwin.com/products?family=sockets&range=ezi
pc power supplies - Page 1
Forum section: electronics / projects

author: houghe9
author_rank: Newbie
timestamp: January 13, 2014, 08:18:57 am
content: hola!i was watching the rigoI power supply video and was thinking about other devices we take for granted. i was thinking about pc power supplies and was wondering if anyone has looked into the damage components may be receiving on the drive power supplies. of course there is regulation but is it enough? what is the quality of the dc feeding external devices. the low cost of drives, cases built to hold arrays, the increase in fans used to cool that additional hardware. especially with all of the new power saving features in use not just going into stand by but reducing processing load on the fly, could that be slowly damaging other components with transient spikes?would it improve reliability to compartmentalize specific devices to a second and third power supply?

author: NiHaoMike
author_rank: Super Contributor
timestamp: January 13, 2014, 02:54:46 pm
content: Multi rail PC PSUs are very common nowadays, though the cheap ones pretty much all lie. A quality PC PSU is about as clean of a power supply as you could get (second only to batteries) as a commodity good.

author: houghe9
author_rank: Newbie
timestamp: January 14, 2014, 02:23:51 am
content: thanks for the reply. I was just wondering about it now that I am doing more component level repair it is becoming very clear how unreliable some of the parts that are being used in everything. I thought it would be interesting to see but as you said cheap parts there is no garuntee. again thanks for the reply.
PC upgrade, sort of - Page 1
Forum section: electronics / projects

author: Renate
author_rank: Super Contributor
timestamp: July 16, 2020, 01:26:50 pm
content: My PC was overdue for an upgrade, so I ordered the parts.I overlooked the fact that my new motherboard is full ATX.My case was mini ATX.Oh, well. I drilled out the rivets to the bottom plate, trimmed it with sheet metal shears and pop rivetted it back in.Now my PC is upside down. I did remount the optical drive right side up.Eventually I'll get a new case.

author: aiq25
author_rank: Regular Contributor
timestamp: July 16, 2020, 02:31:28 pm
content: At least its functional.

author: mikerj
author_rank: Super Contributor
timestamp: July 16, 2020, 03:03:56 pm
content: You'll probably start a whole new "case mod" scene

author: coromonadalix
author_rank: Super Contributor
timestamp: July 16, 2020, 05:19:15 pm
content: seriously? loll i was bout to do an acrylic case, lost too many hours to fit all the partsjust bought a new case instead, now its a small matx with 1500$ worth of parts in it ...asus tuf gaming b550 wifi plusryzen 5 3600x32gb of ram500gb nvme drive500 gb ssd drivezotac mini gt1030 AMP EDITION 6 gbtwo 2.5 inch hot swap bayand a 2 external ports usb3 cardthemaltake 750w psujust unnder 15 secs to boot to windows loll
PC/104: Fitting components that are >15mm high - Page 1
Forum section: electronics / projects

author: logancane
author_rank: Regular Contributor
timestamp: May 13, 2021, 10:27:53 pm
content: Has anyone done a project using a PC/104 stack where you had to use components greater than 15mm high? If so, what is the most professional way to go about it?In my case, I want to include my power supply on the stack and I want to include my inductor which measures 15.37mm. Ideally I want there to be a gap.Inductor:https://www.coilcraft.com/getmedia/a2805f49-c9b8-42c0-9939-b2d75eed7288/ser2900.pdfCheers everyone!

author: Benta
author_rank: Super Contributor
timestamp: May 13, 2021, 10:51:06 pm
content: Stick an M/F connector onto the board to get double height.

author: dmendesf
author_rank: Frequent Contributor
timestamp: May 13, 2021, 10:53:12 pm
content: Just add a number of bare pc-104 connectors to add height without adding boards.

author: daveismissing
author_rank: Contributor
timestamp: May 13, 2021, 10:58:56 pm
content: Quote from: Benta on May 13, 2021, 10:51:06 pmI seem to recall buying some MF with really long tails and assembling boards maybe inches apart

author: logancane
author_rank: Regular Contributor
timestamp: May 13, 2021, 11:12:04 pm
content: Quote from: Benta on May 13, 2021, 10:51:06 pmIs this advisable in a situation where there is likely to be high vibration? I am putting it on a high altitude balloon.

author: Benta
author_rank: Super Contributor
timestamp: May 14, 2021, 10:13:17 am
content: Never heard of much vibration in a balloon. A B-29, yes.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: May 15, 2021, 12:00:07 am
content: If you "want to go professional about it", then stay within the spec of the allotted space.Maybe you can put two inductors in series or in parallel.Another possibility is to mill a big hole in the PCB, and mount the inductor from the underside.I do find it strange though to use PC104 in a high altitude balloon.PC104 is big and heavy. Does not matter much for an industrial environment, but a high altitude balloon is a bit different.Also, Inductors that can handle 100AIf you've been using this design for 40+ years, then maybe it's time for a complete revision. Maybe build something that is the size and weight of, for example an average phone?Including batteries!

author: Terry Bites
author_rank: Super Contributor
timestamp: May 18, 2021, 01:45:46 pm
content: A beast alright. I've used a LattePanda. Despite of its utterly infantile name, it works a treat in grown up applications.
PC/104 plus to pci adapter - Page 1
Forum section: electronics / projects

author: Daxxin
author_rank: Regular Contributor
timestamp: May 09, 2023, 05:16:18 pm
content: need to realize this adapter with custom size but cannot found any schematic wiring connection by google.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: May 10, 2023, 09:10:44 am
content: Maybe this helps:https://pc104.org/wp-content/uploads/2015/02/PCI104_Express_v1_0.pdf(That took me about 3 minutes, inclusive typing this)

author: Psi
author_rank: Super Contributor
timestamp: May 10, 2023, 09:16:40 am
content: I always assume it's a bot whenever anyone uses the word 'realize' to mean 'create' or 'bring into being'.
PCA9685 i2c problem - Page 1
Forum section: electronics / projects

author: xuio
author_rank: Contributor
timestamp: May 02, 2015, 03:14:11 pm
content: I have made a custum board with an ATMega32u4 (sparkfun pro micro 3.3v bootloader, Yeah its arduino based), an IMU (BNO055) and a PCA9685.When I ran the i2c scanner script (from the arduino website) it only recognized the BNO055 (0x29), but not the PCA9685, which should be at 0x40.It does also not react to the example sketch from the adafruit library.The schematic is a clone of adafruits 12 Channel servo board, I assembled 3 boards so far and none of them is working, so a chip fault is unlikely.The schematic is attached and yes: the i2c bus has pullup resistors.Thanks for your help!MoritzEdit: This is the QFN version of the chip

author: eneuro
author_rank: Super Contributor
timestamp: May 02, 2015, 10:42:40 pm
content: Quote from: xuio on May 02, 2015, 03:14:11 pmHow did you got this address?While you have all A0..A5 pins pull down to ground (0), than according to its datasheethttps://www.adafruit.com/datasheets/PCA9685.pdfQuoteFor I2Creadwe get: 10000001 ->0x81write 10000000 ->0x80I'd suggest use small AVR MPU like my favourite ATTiny85 and try to talk to this thing a few lines of custom C code.Another option is to use I2C optoisolated PC <-> MPU intrface and call this device directly from PC without need to use any MPU.I've made such PC Linux based I2C optoisolated PCB with PC817 5kV optocouplers and it performs quite well below 50kHz, while cutoff of slow PC817 is around 80kHz, so rather than messing with Arduino library which might have bugs, I'd rather go to the bacics and run simple AVR I2C code or PC based while it is easy log everything on PC hard disk for analysis directly from I2CBTW: Yep, probably you forgot about this last bit and then 1000000 -> 0x40 but you need add 1 bit more for R/~WAnyway quite nity PCA9685 PWMed LED driver I might want to use in one project to drive H bridges for DC motors control

author: xuio
author_rank: Contributor
timestamp: May 03, 2015, 11:35:26 am
content: I had a look at the schematic again this morning and it turns out that SDA and SCL are switched on the PCB, but only for this chip.I fixed it with a couple of bodge wires and everything is working now.So yeah Murphys Law all the way…But thanks eneuro for your help!Moritz
PCB 3D rendering failure issue - Page 1
Forum section: electronics / projects

author: ranganatennakoon
author_rank: Contributor
timestamp: September 16, 2020, 01:23:22 pm
content: 1) I intend to render a PCB through the Fusion 360.material was aded to render.Then the PCB top layer of the render output was missing.No matter how hard I tried, it still was same.What do I need to do to get correct ?2) What changes need to be made to make the render output more realistic?

author: Mechatrommer
author_rank: Super Contributor
timestamp: September 16, 2020, 03:14:27 pm
content: Quote from: ranganatennakoon on September 16, 2020, 01:23:22 pmpost some relevant pictures here. what do you want to do in fusion. whats the printed outcome? what is your printer?
PCB 4-layer power layout  - Page 1
Forum section: electronics / projects

author: ghoetic
author_rank: Contributor
timestamp: February 02, 2024, 01:55:11 pm
content: I am working on a three level NPC inverter leg, i am interested in opinions on the layout of the layers.this module is intended to connect with 164pin card edge connector.Top layers is UDC+ and PHASE.Bottom layer are UDC- and NP.Inner layers are NP and diode connections.
PCB Antenna Design (GSM/GPS) - Resources Required - Page 1
Forum section: electronics / projects

author: David
author_rank: Frequent Contributor
timestamp: April 24, 2011, 06:04:59 pm
content: Hi all,Could anyone point me in the direction of some information (Links, books, application notes etc) on designing PCB trace antennas? This is a topic I haven't really seen discussed much.Regards,Dave

author: logictom
author_rank: Unknown
timestamp: May 03, 2011, 10:07:07 pm
content: Can't say I know anything on the subject but I was reading this the other day, seems to cover the basics.http://www.freescale.com/files/rf_if/doc/app_note/AN2731.pdfAnother one, for 2.4GHz,http://focus.ti.com/lit/an/swra117d/swra117d.pdf

author: scrat
author_rank: Frequent Contributor
timestamp: May 03, 2011, 10:30:40 pm
content: Searching for "patch antenna design" I found this presentation (https://ccnet.stanford.edu/cgi-bin/course.cgi?cc=ee144&action=handout_download&handout_id=ID11797377905639), where the basic desing calculations remind me of what I studied few years ago (but unfortunately never used). Patch type are quite simple and give directivity (usually orthogonally to the plane), but require quite large pcb area.
PCB antenna design tools - Page 1
Forum section: electronics / projects

author: technix
author_rank: Super Contributor
timestamp: June 14, 2017, 09:22:52 am
content: Do any of you know how to design PCB antennas to a certain frequency?This is aboutmy 4G router project.It needed the following antennae:* 2.4GHz Wi-Fi access point,* Multi-band cellular (two antennae)* Multi-band GPS + GLONASS + Gailieo + Beidou.I am okay with PCB antennae (a PCB trace shaped into some RF voodoo to function as an antenna) or soldered component antennae (a component soldered to the PCB to function as an antenna.) RF pigtails are absolutely my last choice (since it would require me to build a case for it, instead of just whacking the entire assembly inside a paper box and call it a day.

author: technix
author_rank: Super Contributor
timestamp: June 14, 2017, 09:45:17 am
content: Quote from: blueskull on June 14, 2017, 09:34:15 amWhat is a whip antenna? Can I just glue a pair of those down to my PCB after assembly, maybe using double-side foam adhesive that holds the antennae a few millimeters over the PCB?

author: technix
author_rank: Super Contributor
timestamp: June 14, 2017, 10:26:29 am
content: Quote from: blueskull on June 14, 2017, 09:48:40 amThis is what I would avoid.
PCB antenna layout. 915mhz. - Page 1
Forum section: electronics / projects

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: September 10, 2013, 11:21:01 pm
content: HiI wanted to try laying out an antenna on a PCB for a board I am designing. Probably 4 layer.I have a reasonable knowledge of radio comms but have never laid out of designed antennas.Specifics:I am using a radio module from Hope RF. the model is RFM69HWhttp://www.hoperf.com/rf/module/fsk/RFM69HW.htmI want to solder this module straight on to my board which will have a pcb antenna built onto it.The module is based on the SX1231H Transceiver from semtech and the band is 915 MHz.http://www.semtech.com/wireless-rf/rf-transceivers/sx1231h/I dont feel I can layout or even assemble the equivalent circuit to this module on my own pcb, so I will use the module. Very tiny components.Also I want the antenna vertically polarised to match the remote antenna.I currently have the module running nicely with a separate antenna which glues to the inside of the project's ABS box, connected via coax. But my client doesn't want glue, has an aversion to it.Also, when it comes to designing the pcb so that the module to be soldered directly on to it.I am not sure what to do about the main pcb's ground plane.I am fairly sure I should cut out the ground plane or any other fills under it and rely on the module to have its ground plane sorted out. Is this correct?I bought that spectrum analyser from TI for $25 so at least I have some sort of radio tool/toy that should be able to measure antenna efficiency.For any links, design ideas, tips and tricks that would speed me on my way I would be grateful.

author: Psi
author_rank: Super Contributor
timestamp: September 10, 2013, 11:30:58 pm
content: I seem to remember their being online calculators for making PCB antennas.Where you enter the frequency, pcb material etc. and it outputs a design.

author: Legit-Design
author_rank: Frequent Contributor
timestamp: September 11, 2013, 12:18:53 am
content: http://www.ti.com/lit/an/swra351a/swra351a.pdfAntenna Selection Quick Guide DN035with Pictures and some basic info of each design and links to design notes.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: September 11, 2013, 12:26:39 am
content: Wow great link, I had found some of those documents but it's nice to have it laid out like that.Thanks Legit.
PCB as reference for EMI measurements - Page 1
Forum section: electronics / projects

author: Anders Petersson
author_rank: Regular Contributor
timestamp: March 31, 2021, 09:55:07 am
content: I'm getting some basic equipment to measure and shield EMI (electromagnetic interference). But will my measurements be correct and will my shielding be effective?Is there any PCB with known and documented EMI levels which I can get to compare my readings?A known emitter of E and H radiation would also be useful to test the susceptibility of my own PCBs.I imagine some manufacturer of EMI shields could publish/sell such a board as a demo of their shielding. Probe manufacturers might also use it as marketing or educational kit.

author: sahko123
author_rank: Frequent Contributor
timestamp: March 31, 2021, 01:38:43 pm
content: id say post this into the rf tab someone there might be more likely to know

author: Anders Petersson
author_rank: Regular Contributor
timestamp: March 31, 2021, 02:43:04 pm
content: Thanks, good idea. Here:https://www.eevblog.com/forum/rf-microwave/pcb-as-reference-for-emi-measurements-275608/
PCB Assembler - Page 1
Forum section: electronics / projects

author: Nanobot
author_rank: Newbie
timestamp: November 14, 2010, 01:39:48 am
content: Does anyone know of a reliable PCB assembler of small quantity PCBs?I am looking to have about 50 PCB's assembled, all SMD 0603 parts, SOIC and 1 64-LQFP u-Controller (totally about 350-400 pads). There is no through hole stuff.I am in Australia but will take suggestions of assemblers from nearly anywhere (all the components are sourced from around the world anyway).ThanksJake

author: krapht
author_rank: Contributor
timestamp: November 14, 2010, 10:14:06 pm
content: While I've never used them, I'm a fan of the blogs written by the staff athttp://www.screamingcircuits.com/.So you might take a look at them.
PCB assembly costs why would LCCs and/or QFN packages double the cost? - Page 1
Forum section: electronics / projects

author: splin
author_rank: Frequent Contributor
timestamp: March 20, 2017, 09:56:15 pm
content: I was just looking at the PCB assembly cost estimator atwww.PCBShopper.com. 1K boards with 30 unique parts, 100 SMD parts comes out at $910. Change to 99 SMT + 1 BGA/QFN/LCC part and the cost doubles to $1880.That's a big difference; I understand that BGA handling can be expensive but what about QFN/LCCs? Aren't they pick and placed and reflowed like any other SMT board or do they require the board to be processed on a different, more expensive line?Do all (most at least) BGA designs require XRay testing after assembly and is that likely to be included in the above pricing? Do QFN and LCC designs also require XRay testing? Doh! Just looked at the order page of one of the quotes - PCBCart. Against the 'number of BGA/QFN/LCC parts field' there is a roll-over help pop-up which makes it clear that all these types require X-ray testing.That does make me wonder why so many parts are only available in leadless packages even for relatively small number of leads - for example the AD5780 is only available in a 24-Lead LFCSP_VQ package.
pcb assembly - Page 1
Forum section: electronics / projects

author: wjmicro
author_rank: Newbie
timestamp: March 02, 2015, 05:07:59 am
content: I am looking for assembly of about 500 simple 2 sided PCBs. Nothing fancy. Very basic SMD. In this small run is there anyone out there that can do this without charging me an arm and a leg?

author: miguelvp
author_rank: Super Contributor
timestamp: March 02, 2015, 05:20:17 am
content: I recently backed up the papilio duo FPGA/AVR board and they used seeed studio:http://www.seeedstudio.com/The board looks nice and clean and they worked out some minor problems with the creator of the board.

author: rx8pilot
author_rank: Super Contributor
timestamp: March 02, 2015, 05:53:59 am
content: Quote from: wjmicro on March 02, 2015, 05:07:59 amIt will always feel like an arm and a leg.First question, where in the world are you? The resources vary greatly in different regions. In southern California, there a a ton of small assembly houses that are reasonable and easy to deal with. Screaming Circuits is good if you want to ship a kit to them or they can make the PCB's through Sunstone, source the components, and assemble. Prices and lead times seem to vary based on the sophistication of the shop. There is one shop close to me that was somewhat low-tech but the prices were good. If your PCB is not BGA or .4mm pitch parts, the prices are not too bad. I personally did not like shipping kits to anyone. I always wanted to deal with people direct to avoid as many issues as possible. Also, I would be present for the setup to answer questions and inspect them myself. 500 PCBs gone wrong can be a serious problem especially if it was my fault with bad documentation.Anyway, where are you?
PCB Autoroute Problems in Eagle - Page 1
Forum section: electronics / projects

author: thelostlevel
author_rank: Newbie
timestamp: July 05, 2016, 07:51:36 pm
content: i thought i'd try and make myself a pcb for thishttp://www.mmmonkey.co.uk/rgb-scart-scanlines/scanline generator but this is my first eagle project and im having a problemin board view when i click autoroute it works fine but when i draw polygons around the board for gnd it will not autoroute and i've tried ratsnest before hand and still nothing, could someone take a look and tell me what i've done wrongi've attached sch & brdthanks in advance

author: timgiles
author_rank: Regular Contributor
timestamp: July 05, 2016, 08:28:04 pm
content: Can't look but have you named the polygons correctly and if using multiple Poly's that touch, look into the levels setting for them. On mobile so excuse lack if robustness in reply!!

author: TheDirty
author_rank: Frequent Contributor
timestamp: July 05, 2016, 08:45:25 pm
content: Placing the fills is the last thing you should do. Autoroute and then place the polygons.You really shouldn't autoroute at all. The Eagle autorouter is not very good and this looks like an easy board to route manually.

author: thelostlevel
author_rank: Newbie
timestamp: July 05, 2016, 08:49:57 pm
content: i have labelled them both as gnd, one for top and one for bottom layers and will give it a go manual routing i just thought it would be simple to use the autoroute but obviously notone problem i had when i had all the lines in before i did the polygons is the gnd plain only worked on part of the board

author: thelostlevel
author_rank: Newbie
timestamp: July 05, 2016, 08:55:31 pm
content: chunks on the board not covered how do i correct that?

author: thelostlevel
author_rank: Newbie
timestamp: July 05, 2016, 09:52:02 pm
content: all sorted now

author: Dago
author_rank: Frequent Contributor
timestamp: July 06, 2016, 04:22:21 am
content: Never use autoroute, especially Eagles autorouter.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 06, 2016, 07:26:44 am
content: Autorouter (if usable at all - depends on the tool) is an advanced feature meant for those who know how it works and can configure and guide it properly. It's not a beginner feature. This is a very common misconception. Don't use it.
PCB based USB ESD protection / filter? - Page 1
Forum section: electronics / projects

author: ubbut
author_rank: Regular Contributor
timestamp: July 11, 2018, 08:41:42 pm
content: Just watched Dave's 3000T oscilloscope teardown and one detail on the board caught my attention.(It is not visible in the high res photos, so I am attaching a screen shot from the video)The USB lines have this interesting PCB feature. Given that the only other part here is (presumably) a common mode filter, I suspect that this acts like a tiny spark gab for ESD protection. But there may be more to it as there are these 'wiggles'. Maybe this is some LC-Filter as well?I would be very interested in learning more about this. After all you get PCB features for freethanks

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 12, 2018, 02:20:19 am
content: Doesn't look like much of anything with silk and soldermask over it.Tim

author: BrianHG
author_rank: Super Contributor
timestamp: July 12, 2018, 02:56:24 am
content: That's not silk paint. It's too fine and exact to the trace thickness. It is exposed tin plating.Also, look at the other USB plug, it has the same pattern, with traces to the GND plane and decoupling cap.

author: ubbut
author_rank: Regular Contributor
timestamp: July 12, 2018, 01:22:22 pm
content: I agree. This means there is some purpose here. Would really be interested in design parameters and insights !

author: whollender
author_rank: Regular Contributor
timestamp: July 12, 2018, 01:47:30 pm
content: Only going by the copper, it looks like it's just a footprint that's not loaded that's a shunt between the line and ground. In that location, I'd guess for ESD.That doesn't explain the opening in the solder mask, however.
PCB Capacitor Burnout - Page 1
Forum section: electronics / projects

author: ipek.grgc
author_rank: Contributor
timestamp: June 20, 2020, 09:48:19 am
content: Hello, hope everyone is doing well.I have designed an STM32F1 board variation. I have multiple power sources. One of them is USB 5V and the other is JTAG 3V3. 5V is converted to 3V3 through a MIC5205-3.3YM5 regulator with a 2.2uF bypass cap on its output. The thing is, when i plugged the JTAG connector and powered the circuit from JTAG 3V3 input, after a little while, the 2.2uF bypass cap of the regulator started to smoke. Then i checked, there was short circuit. I tested again after 10 mins, and the short circuit was gone. Then i plug the USB this time, and after a while the regulator input pins started to smoke and there was little sparks. I measured the reg output, it was 3.3V then there was a short again. Now i reflowed the reg and caps again (thinking maybe there were a tiny solder paste leftover would have been stuck in between the legs) and plugged the USB back. I am measuring the reg output and it is currently 1.8V, no smoke or sparks. And when i unplug the USB and plug the JTAG 3.3V again, the same cap starts to smoke again, creating a short. I am lost, i can't find the reason behind this. I am attaching the reg schematic and PCB layout. I am happy to hear any ideas, thanks!

author: Siwastaja
author_rank: Super Contributor
timestamp: June 20, 2020, 09:53:02 am
content: What is the capacitor body size?Ceramic capacitor cracking failure is a possibility, especially if the cap is larger than 0805 (say, 1206 for example). Replace the cap. Make sure there is no board flex. Do not touch the capacitor body with the soldering iron, and solder the pads quickly (a few seconds per pad) without applying excessive heat.

author: mikerj
author_rank: Super Contributor
timestamp: June 20, 2020, 11:04:28 am
content: What type of capacitor did you fit? The datasheet for this regulator states that low ESR capacitors (e.g. ceramic) can cause oscillation.

author: ocset
author_rank: Super Contributor
timestamp: June 20, 2020, 11:18:25 am
content: c20 and c19 are near board edge and may have suffered depanelisation damage. As discussed, replace and try again.

author: ipek.grgc
author_rank: Contributor
timestamp: June 28, 2020, 10:04:36 am
content: I replaced C19, C20 and the Regulator. Now everything works fine, maybe the problem occurred during the SMT assembly. Thanks a lot for the help.
PCB checklist for buttons/switches - Page 1
Forum section: electronics / projects

author: 5upercircuits
author_rank: Contributor
timestamp: March 28, 2019, 08:50:15 am
content: I'm creating a public PCB design checklist (https://murphymeter.com/checklists/checks/2/0/). The scope is consumer products.What would you put into a checklist regarding buttons and switches?So far I have:- Contact bouncing- You should label what it's used for- Operating lifeWhat else? How about contact oxidation? Mechanical stability? How do you check this, or more precise what are counter measures?Is contact oxidation really a problem for consumer products? Maybe if you live close to the shore or in a humid area?