hybridfree/eevblog-posts huggingface dataset:
Another Constant Current #102 Implementation - Page 1
Forum section: electronics / projects

author: zargnut
author_rank: Contributor
timestamp: December 19, 2011, 02:44:52 am
content: I figured this looked like an interesting newbie project. I took advantage of the schematics published by chrisw957. thanks. Would have bought a board, but could not get a hold of him. I couldn't get it to work initially as I was hooking the pot up as I normally do (in series, without grounding it). I was advised by my infinitely smarter brother that this would not work in this application as there was no current passing to the OP amp. Still not entirely clear on this concept, if anyone wants to educate a newbie.I added a power option for a transformer vs battery and threw it into a pseudo box. As I didn't have a fan laying around I left the sides open for ventilation.I would love some advice on construction, materials, "next time" kinda stuff.Here is link to pictures:https://picasaweb.google.com/zargnut/Electronics_constant_load?authuser=0&feat=directlinkthanksdan

author: eternal_noob
author_rank: Regular Contributor
timestamp: December 20, 2011, 01:33:35 am
content: Quote from: zargnut on December 19, 2011, 02:44:52 amThe reason why this doesn't work properly is because most of the op-amps have a high input resistance to ground. So if you think of the potmeter and the input of the amp like a voltage divider, the potmeter just becomes the uppermost part of the voltage divider. In this case you can only adjust the voltage by 50 millivolts or so. And, remember that there is always a relationship between voltage and current...I have made a little demonstration for you. You need to have Java installed and a little bit of patience (the applet is a slow starter sometimes). The I Meg. resistor represents the op-amp input resistance in both instances. Hope you'll understand things better now..http://bit.ly/sKD4TyQuote from: zargnut on December 19, 2011, 02:44:52 amI'll guess your heat sink will do for most jobs, but I doubt it will withstand the more hardcore ones. Why not use a computer CPU heat sink with a fan next time? You can use one of the spare sections in the op-amp a thermostat, like I did, and easily dissipate 30 Watts through the thing.Here is mine.
Another constant current / power load - Page 1
Forum section: electronics / projects

author: rounin
author_rank: Regular Contributor
timestamp: May 28, 2016, 06:06:34 am
content: Hi all,I decided i needed an analog project to learn how to use op amps (previously being a programmer who moved into digital, and then a bit into power electronics) so I drew up a constant power/current load bank, with active overcurrent/overpower shutdown. It uses a TI current sense amplifier, a AD633 multiplier, and some opamps, comparator, and a latch. Power is provided by a LTC3260EMSE inverting chargepump + dual ldo. I'm hoping for operation at 20V/20A/400W, potentially with forced air cooling over a decent size heat sink.Any feedback on part selection or methodology would be appreciated, thanks.
Another DIY Reflow Oven - Page 1
Forum section: electronics / projects

author: Takigama
author_rank: Newbie
timestamp: February 10, 2025, 03:29:11 pm
content: Howdy Guys,Didn't see anyone post this anywhere yet, but I thought some might be interested. Kmart in Australia have a bunch of "mini" appliances, which are quite cheap. Last time I went there they had a mini oven and my first thought was "thats a nice size for a reflow oven". Its about half the size of most toaster ovens that are often used for DIY reflow ovens and its all of $35AU (not on sale) there's a coke can in the photo for size comparison.Got it home, stuck a thermocouple in there and was disappointed to see it take 10 minutes for the thermocouple to read 200c (at around the same time, its in-built thermal switch turned off). But its a radiant heater and im not sure how accurate my thermocouple is here (i'll try with another later).Put a sacrificial board in with lead-free solder paste, a strip of thin solder and two chunks of thick solder and it cooked them surprisingly quickly. From room temp, 90 seconds for the lead-free to fully cook, the thin solder (0.5mm) went slighly before it and the 3mm solder was beading at about 105seconds (in the photo the paste is on the left, the thin solder is on the three pads next to it and the two large blogs are 3mm solder).I then wanted to see if it could destroy a board and took 3 minutes to turn the board into a black mess in the photo.Unfortunately I dont have an SSR suitable for doing a diy reflow on it yet, but i should have one soon, i'll be curious to see how it performs. Mostly I love it for its size and the fact the tray comes out when you open the door (my toaster oven doesn't do this), the tray is 15cm x 14cm which is bigger than any board I have ever made that would need a reflow oven.The down side is half of it is held together with bend tabs which makes taking it apart quite tricky (where the timer knob is is one place where that is irritating), but you can get to everything that matters without having to touch them.
Another front panel - function gen redux - Page 1
Forum section: electronics / projects

author: icon
author_rank: Regular Contributor
timestamp: April 15, 2012, 10:50:42 pm
content: A function generator got a bit of an internal facelift thanks to some help in the beginners' forum, so I thought a makeover was in order. I used Inkscape and an inkjet printer again. A bit of a motley collection of knobs, but they're what I had available. Photos show the original and the new case; it's a lot easier to do starting with a new case, as you can use the panel design as a drilling template.The function generator's still crap, sadly.John
Another Lattice iCE40 FPGA Dev Board - Page 1
Forum section: electronics / projects

author: joshtyler
author_rank: Contributor
timestamp: October 12, 2020, 10:38:30 pm
content: Just for fun I've been working on a Lattice iCE40 FPGA development board in a bit of spare time over the last year or so.I wanted something compact with gigabit Ethernet, external SDRAM, and potential for connecting other peripherals over PMODs.To make it self contained I created a bootloader FPGA image that can accept bitstreams over the USB UART and saves them into the boot SPI flash. As a nice byproduct this architecture lets the user save multiple applications into different slots, and choose which to boot into at runtime using the push buttons.Choosing the largest iCE40 FPGA means that reasonable sized projects will fit. Getting the gigabit Ethernet to run at full rate is challenging on the iCE40 fabric, but is very possible for simple designs.I think it would make a nice platform to prototype a logic analyser, where data can be streamed out over the Ethernet link, but it will probably take me a while to get around to writing this!You can see all the details athttps://github.com/joshtyler/manila-ice

author: TheHolyHorse
author_rank: Regular Contributor
timestamp: October 13, 2020, 10:28:12 am
content: Looks really nice
Another LISN - Page 1
Forum section: electronics / projects

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 30, 2021, 06:13:48 am
content: Actually put this together some years ago, and buttoned it away before I could take a picture...Three lines, from a 240VCT isolation transformer; the three inductors of varying size at the left end, ballast the transformer's leakage (biggest for neutral, a direct connection obviously, the others for H1/H2 -- evidently at different depths in the windup, hence the differing leakage), giving close to 250uH I think it was, and this is terminated by, not 4.7 ohms for some reason, but 7.8 actually (hey, I have a ton of those resistors..?), in series with 5.6uF. Then the traditional 50uH chokes to the output, and coupling caps and highpass filters to the RF ports.Chokes are designed for soft saturation around 30A or so I think, so, good enough for the 15A RMS rating of the transformer it's tuned for, and won't be quite right at the peaks of a full load FWB, but at lower power, or higher PF, it's good. Anyway, that only affects LF response, so even if switching ripple might read in error in that case, the higher stuff is fine.Given the stub lengths and terminal strip construction,Oh yeah a construction detail about that terminal strip in the middle, that's copper clad (I don't have any old-school strips suitable for 14AWG solid wire), it's 2oz double sided, with a strip along the base to make a nice wide solder fillet to the bottom panel, then separate squares along the top, with holes drilled through to clinch the wires on.No, no plots or anything quantitative; no fancy limiters. It's pretty basic, it'll work well over 30MHz which is good enough for me. I suppose stub lengths will start pulling in by a few hundred MHz, as well line-to-line crosstalk; but anything I'm going to wire up to it, is already going to be dubious by such frequencies, so yeah, no worry. Also based on my experience with a different network, which I did measure up to fairly high frequencies (from which, I'd expect maybe ~20dB crosstalk between adjacent taps).Tim
Another Microchip Screwup?  Tx2/Rx2 on the PIC1F26K22.... - Page 1
Forum section: electronics / projects

author: Jon Chandler
author_rank: Frequent Contributor
timestamp: October 08, 2010, 10:42:21 pm
content: (Excuse a couple paragraphs of necessary background information)On my TAP-28 board, designed for embedded applications using 28 pin PIc18-series parts, I've included connectors for variousfunctions.There's a 6-pin connector for ICSP, following the pinout convention of the PICkit 2. There's a 6-pin connector for the UART with TxD and RxD (along with 2 other port pins for general purpose use) that follow the pinout convention for the PICkit 2 UART tool. The makes it simple to program the chip with the PICkit, and then swap the cable over to the UART connector to monitor program execution.There's a 3rd 6-pin connector for I2C/SPI. For this, I followed the convention of the PICkit serial analyzer. The result is connectors that match the function, but they are all wired similarly with (up to) 4 port pins, power and ground. If a particular feature isn't being used, the connectors are somewhat interchangeable with power, ground and 4 general-purpose port pins.Many of the 18F-series map the functions the same way, so many different parts can be used on the board.Now enter the 18F26K22, a 28-pin package with 2 UARTs. Very handy for I/O intensive applications. So the question came up of how this would map to the dedicated connectors.The first complaint is the idiotic pin diagram from the data sheet. It shows only the port numbers and none of the alternate functions.Looking further, I found the pin table. Tx2 and Rx2 are on RB6 and RB7, the pins used for ICSP.Ok, that's good. The 2nd UART maps to the ICSP connector. But looking a little closer, and looking at how my connectors map, this reverses Rx and Tx compared to my UART connector. Bad luck you may be thinking. But what this means is the when you have the PICkit connected to the ICSP connector for programming, when you launch the UART tool to monitor the second UART (convenient, since the PICkit is already connected there), the UART connections will be WRONG.Maybe this is way the UART tool isn't included in the PICkit 3

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 09, 2010, 03:53:51 am
content: maybe they are walking backward!
Another old connector, this time from Fluke... - Page 1
Forum section: electronics / projects

author: sdg
author_rank: Regular Contributor
timestamp: November 21, 2013, 09:59:43 pm
content: Hi,What is the name/brand of that green connector ? This one is on the rear panel of a Fluke 8520.

author: AndersAnd
author_rank: Frequent Contributor
timestamp: November 21, 2013, 10:24:56 pm
content: 20 pin EDAC 516 series:http://www.edac.net/product.html?cid=31Sold at eBay, Mouser, DigiKey etc.eBayhttp://www.ebay.com/itm/Fluke-369231-Connector-Rectangular-Cable-Plug-20-Position-/300853662036?pt=LH_DefaultDomain_0&hash=item460c469154eBayhttp://www.ebay.com/sch/i.html?_nkw=EDAC+516Mouserhttp://www2.mouser.com/EDAC/Connectors/Backplane-Connectors/Rack-Panel-Connectors/516-Series/_/N-axj5h?P=1z0zlevZ1z0wxonZ1yzvd0oDigiKey:http://www.digikey.com/product-search/en?pv88=34&FV=fff40016%2Cfff803d2%2Cfffc0097&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25

author: sdg
author_rank: Regular Contributor
timestamp: November 22, 2013, 11:22:06 pm
content: Many thanks !

author: KC7HP
author_rank: Newbie
timestamp: January 13, 2020, 01:28:48 am
content: I just got the same multimeter from the eBay so appreciate the guidance. Note EDAC has revamped their website and the product information link is now:https://www.edac.net/series/516
Another Pre-tracking regulator problem, what's wrong? - Page 1
Forum section: electronics / projects

author: baoshi
author_rank: Regular Contributor
timestamp: October 12, 2012, 03:27:04 am
content: Inspired by Dave's Rev.C of lab power supply design, I am trying to built up my power supply with components on hand (LT3080 and LT1871).I did some simulations in LTSpice IV.The strange part is, I modeled the output bypass capacitor C3 of SMPS using Sanyo OS-CON 35SEPF120M (120uF, 18mOhm ESR), the LT3080 output went free fall to negative value.The circuit simulates fine if I increase ESR to 25mOhm, or I parallel two output capacitors.Initially I suspect it is the ripple current limit of capacitor causing this, but even if I increase ripple current rating to 10A the simulation is still wrong.All the while pre-tracking regulator output is normal though.I wonder what's happening there, or is it a LTSpice error?The source file is attached.Thanks for viewing.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: October 12, 2012, 04:41:41 am
content: Bear in mind I am only guessing this, I didn't look at the model.Your actual circuit is possibly unstable with this cap as the load.LTSpice trys to follow this unstable behaviour with each iteration but its model soon fails. Something goes divide by zero maybe or divergent instead on convergent.I guess it is just showing the limitations of LTSpice which is doing the best job it can of showing the limitations of your circuit.
Another project - OneAC Power Conditioner - Page 1
Forum section: electronics / projects

author: xrunner
author_rank: Super Contributor
timestamp: May 23, 2016, 11:18:47 am
content: My neighbor had to go to assisted living, and his daughters were cleaning up the house. He had told them to give this thing to me, so one brought it over last night. Well, her husband was carrying it because it weighs a TON. They thought it was a battery backup, but it's really a OneAC power conditioner.I checked it out and it works, but it's pretty dusty and dirty. It has a honkin' massive transformer, two, what I would call run caps (5 uF ea.), and some sort of OneAC device inside (lower left in pic). From what I understand it removes power spikes and can smooth out millisecond gaps in power, couldn't find a lot on it. Apparently it's a big 60 Hz tank circuit?I'm going to clean it up, replace the caps, and replace the outlets on the rear - things got a little rusty and crusty over the years.

author: bktemp
author_rank: Super Contributor
timestamp: May 23, 2016, 11:37:31 am
content: I've bought a Oneac power conditioner some years ago, because I thought it would be a ferroresonant transformer/regulator. But it is only a simply isolation transformer with some caps attached to the output.The leakage inductance of the transformer and the capactitor at the output form a low pass filter, removing short spikes. But compared to a true power conditioner/regulator it does not work very well in cleaning up the waveform.Your unit also looks like a isolation transformer with some caps attached to the output.The additional device is probably a resetable fuse (it should have a pushbutton).

author: xrunner
author_rank: Super Contributor
timestamp: May 28, 2016, 11:24:14 am
content: I've been cleaning the thing up. I also bought two new capacitors and three new outlets.
Another RLC calculator - Page 1
Forum section: electronics / projects

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 11, 2023, 07:32:42 am
content: This one using vector measurements:https://www.seventransistorlabs.com/Calc/RLC.html#vecSeems to be correct but let me know if you find any funny business.I should put the impedance and parallel/series equivalents into their own section or page too, but this is good too:https://www.daycounter.com/Calculators/Parallel-Series-Impedance-Conversion-Calculator.phtmlTim

author: precaud
author_rank: Frequent Contributor
timestamp: January 11, 2023, 01:35:42 pm
content: Thanks, will be handier to use than the program I have on my ancient HP 41CSince the Z is a vector quantity, how about showing the phase angle too? Some of us prefer to work with results not normalized to a given frequency.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 11, 2023, 01:58:41 pm
content: Ah, I don't have much use for that myself, but for reference, sure why not. Give it a refresh and see.Tim

author: precaud
author_rank: Frequent Contributor
timestamp: January 11, 2023, 02:08:48 pm
content: I don't see it - still Z and Q in the results box.

author: jonpaul
author_rank: Super Contributor
timestamp: January 11, 2023, 02:09:54 pm
content: Tektronix 1961 circular slide rule...no software no computer, intuitive, parallel solutions of all variables.Tek rep giveaways...still have and use two!JON

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 11, 2023, 02:18:37 pm
content: I thought of a better way to do it.Try againTim
Another round of "what connector is this?" - Page 1
Forum section: electronics / projects

author: symp
author_rank: Contributor
timestamp: July 10, 2024, 03:08:32 am
content: Hi All,Sonar connector from a lowrance fish finder, original got twisted off the board, but no luck finding what it is.....no markings at all, doesn't seem to match up to any of the usuals like TE or amphenol. 7 female contacts, pcb mount, outer diameter 18mm, 27mm height top to bottom of the housing (not including pins).Offering a $10 paypal bounty

author: Jonathon_Doran
author_rank: Regular Contributor
timestamp: July 10, 2024, 08:11:08 am
content: A Lowrance 7-pin proprietary connector?https://connector.pinoutguide.com/7_pin_Lowrance_custom/

author: symp
author_rank: Contributor
timestamp: July 10, 2024, 12:15:38 pm
content: That's the one, I will be very sad if it really is proprietary, seriously?

author: Jonathon_Doran
author_rank: Regular Contributor
timestamp: July 10, 2024, 12:59:53 pm
content: I've seen some of the connectors on pigtails or adapter cables. Do you have the model number of the board/device?

author: symp
author_rank: Contributor
timestamp: July 11, 2024, 05:31:07 am
content: Lowrance HDS 10
Another Use for a PLCC Extractor - Page 1
Forum section: electronics / projects

author: ximac
author_rank: Contributor
timestamp: June 27, 2015, 07:16:15 pm
content: Hi,Recently I bought a TL866A EEPROM blower that came with a free PLCC extractor. I had little use for this tool until I needed to extract a difficult TO-3 packaged 2N3055 in an HP tracking generator. Voila - remove the screws, apply a little heat to the joints and the extractor pulled it clear.Cheers - Joe
Anritsu MS2721B portable spectrum analyzer repair - Page 1
Forum section: electronics / projects

author: nexus
author_rank: Regular Contributor
timestamp: December 10, 2022, 11:11:00 pm
content: Hi all,Thought I'd share a project I just wrapped up. I had an MS2721B portable analyzer that I bought for parts (non working) on eBay. I discovered that a critical connector which interfaces with the front panel was ripped off. 24 pads were also removed by this previous damage.I sent the board out to an electronic repair shop that specializes in ripped pad replacement (NorthridgeFix). I've been watching their channel for a while since they have lots of great repair videos, and thought this would be a good opportunity to see just what kind of repair they could pull off!The results speak for themselves:Enjoy.
Antenna Controller - Page 1
Forum section: electronics / projects

author: PioB
author_rank: Regular Contributor
timestamp: September 02, 2013, 07:57:59 pm
content: Hi,I am not sure if that should go here or in the microcontroller section..My father-in-law is a member of an Astronomical Society. Some time back they got a donation of an 8 ft parabolic dish.Due to my background in computational chemistry, a ham radio exam ~20 years back, and more recently an interest in arduino/microcontrollers he asked me if I could help him with the design of the antenna controller, a challenge I happily accepted.In a first stage that should only be able to control the elevation, with a possible extension to azimuth later. So my general idea was as follows:An Atmega328P is connected to the computer via an usb (FTDI FT231X) chip, a few buttons/rotary encoder for the menu control, a PCF8574 Port expander for the LCD, an eeprom for data/elevation storage and a P82B715 I2c bus extender.On the other end of this is a board with an accelerometer (Invensense MPU6050 on a GY-521 board from amazon) which will serve as an inclinometer by using gravity as a reference.An optocoupler will drive a Pololu Motor controllerhttp://www.pololu.com/catalog/product/759(up to 40 V 20 A)The actuator is not bought yet, but will probably be of the 12 or 24 V variety.I would be very happy if someone could review my schematic which is here:https://lh6.googleusercontent.com/-VPeZ0D-Z9CA/UiTkMUqQV9I/AAAAAAAAHcM/Q2QxvyUBtsw/s2560/Schematic.pngThe (eagle) design files are on githubhttps://github.com/baettigp/Dish-ControllerMainboardThe reset circuit leaves the possibility to switch between a capacitor in series and one in parallel, as Arduino seems to use the series version in their boards...The accelerometer-adapter board is already made and the accelerometer sends back results if connected via a second P82b715.I have learned very much during the design of this project, but not being an EE, I hope I haven't commited any really big blunders.Thank you very much for looking at my design.
Antenna design guidelines for NRF52832 based board - Page 1
Forum section: electronics / projects

author: Sai teja
author_rank: Regular Contributor
timestamp: November 18, 2017, 02:10:11 pm
content: Hello,I am designing a 2 layer board with NRF52832 IC. I am following all design considerations and reference design mentioned in IC's datasheet provided by Nordic. I have a query regarding antenna. "Application Note AN043 pdf contains reference meandered f-antenna antenna for 2.4gHz. As my requirement is also for 2.4gHz, I am using the same antenna as mentioned in pdflink:http://www.tij.co.jp/jp/lit/an/swra117d/swra117d.pdfI have attached the reference antenna image from this pdf.A/c to the pdf, antenna distance from board edges(D1, D2 and D3) is mentioned. But my board dimensions would be 100X50.Plese clarify my following doubts1) Is it mandatory to follow those dimensions(D1, D2 and D3)?2)Is board size affect antenna performance?3)Is it required to use any passive component to tune the antenna?4)Unfortunately, I don't have network analyzer with me. Can you suggest any online simulation tools to validate my design?
Antenna diversity spacing for the mobile band? - Page 1
Forum section: electronics / projects

author: eecook
author_rank: Regular Contributor
timestamp: September 02, 2014, 03:29:36 pm
content: Hi all,I am trying to calculate the optimum distance between the main_ant and div_ant for a 3G/4G (700-2100Mhz) modem I am working on. This modems (ideally) will be on a fixed position attached to light poles. From what I've found, multipath fading will appear either1. As a standing wave, in which case a half wave separation would be ok, or.,2. As signals coming from different channels (different multipaths), in which case it is desired to minimize the cross correlation.If 1. was the case, what is a good trade off for multiband scenario?If 2. was the case, I cannot seem to find any pair of references that say the same thing. Some talk about a minimum and a maximum distance, some talk only about a minimum (sory I am not referencing, it's been a bit of a messy search), and in any case, this distances are not always the same value (expressed as fraction of wave-length).I found this documenthttp://www3.alcatel-lucent.com/bstj/vol50-1971/articles/bstj50-6-1859.pdfwhich seems useful, except for the part were it says that I should be using a 70lambda spacing, which is way bigger than the enclosure (ants should go inside). Plus, cell phones have the div_ant only a couple of centimeters seperated from the main one.Could anyone shed some light on the matter please?Is there any document that explains this at a more fundamental level?Regards.
Antenna Impedance - Page 1
Forum section: electronics / projects

author: James Nilton
author_rank: Newbie
timestamp: June 01, 2015, 10:09:47 pm
content: I have to remove the antenna from my Multi-Rotor to get it into the boot of my car, this has on a couple of occasions led to me almost powering up with no antenna attached. this would obviously lead to my transmitter frying, so I made a 'remove before flight' flag to remind me.But i'd like to make a flag to replace the antenna with the same impedance as the antenna, just in case the flag doesn't remind me.how would I measure the impedance and what could I use to replicate its impedance?

author: Howardlong
author_rank: Super Contributor
timestamp: June 01, 2015, 10:54:11 pm
content: I assume that this is for the video downlink?You can measure the impedance with a network analyser.However, it's almost certainly 50 ohm.

author: calexanian
author_rank: Super Contributor
timestamp: June 02, 2015, 12:56:33 am
content: I would use an appropriate small dummy load. What bands and what power are we talking here?

author: Melt-O-Tronic
author_rank: Frequent Contributor
timestamp: June 02, 2015, 01:45:55 am
content: Pending answers to the above questions, you can almost certainly solve your problem with a 50 ohm terminator off of eBay. I'm guessing RP-SMA or SMA. Once you get one, dip it in red Plasti-Dip or paint it a bright color as a visual reminder.

author: calexanian
author_rank: Super Contributor
timestamp: June 02, 2015, 06:13:16 am
content: http://www.diamondantenna.net/dl30a.htmlSomething like this perhaps. Also most modern digital rigs have high SWR cutout to save the power amp. MOST do. Not all, and it should in no way be used as a fail safe in that manner.

author: Dago
author_rank: Frequent Contributor
timestamp: June 02, 2015, 07:29:56 am
content: Are you sure your transmitter would fry? Most low power transmitters can handle full reflection.

author: SeanB
author_rank: Super Contributor
timestamp: June 02, 2015, 05:36:26 pm
content: 50R dummy load on a N connector, and attach the red flag to it as well, so you are less likely to lose it.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 02, 2015, 05:53:28 pm
content: Note that the terminator has to be rated for at least some fraction of full transmitter power, or else both will end up smoked.Tim
Antenna in a non standard enviroment - Page 1
Forum section: electronics / projects

author: daqq
author_rank: Super Contributor
timestamp: August 27, 2013, 07:45:59 am
content: Hi guys,Assuming a standard bluetooth module with a built in antenna (2.4 GHz, ceramic on PCB), would the module function and communicate properly was in an environment with a different relative permittivity than air? Namely clear epoxy (somewhere around er = 4), with a thickness of several centimetres.Thanks,David

author: Psi
author_rank: Super Contributor
timestamp: August 27, 2013, 07:54:43 am
content: This might be of some use.http://duepublico.uni-duisburg-essen.de/servlets/DerivateServlet/Derivate-14694Final_Papers/GM0105-F.pdfHas values for epoxy potting at 2.4, 5.8, 12 and 24Ghz

author: KJDS
author_rank: Super Contributor
timestamp: August 27, 2013, 09:51:30 am
content: They usually need some matching circuitry to get reasonable performance and it needs tuning on a design by design basis. so you'll need to take a best guess, attach a measuring cable, pot it, let the epoxy set, measure it then adjust the component values to achieve a good tune. Adjusting those with epoxy over them is going to be tedious or will take a few boards and a few epoxy pours.

author: babysitter
author_rank: Frequent Contributor
timestamp: August 28, 2013, 07:01:22 am
content: I am up to a similar thing - tell your boss clear epoxi is not suitable at least in the proximity of the antenna. I am looking into PUR "integral foam".(Just dropped a line to get onto the notify list)

author: ElectroIrradiator
author_rank: Frequent Contributor
timestamp: August 28, 2013, 07:13:23 am
content: Short answer is no. Antennas markedly change their basic properties when encapsulated in solids, compared to air/vacuum. For microwaves you have the added problem of dielectric losses in the potting compound. Those losses can be amazingly high in some cases, as many epoxies and the likes have very poor RF qualities.So at the very least the antenna needs to be redesigned for the new environment / dielectric constant of surroundings, after which you need to check for losses and transmission efficiency through the potting compound.
Antenna matching and substitution - Page 1
Forum section: electronics / projects

author: Digibin
author_rank: Regular Contributor
timestamp: July 19, 2017, 10:06:48 pm
content: I'm looking to replicate the design of a sub GHz eval boardSTEVAL-FKI868V1and integrate it into a custom design. Using the same schematic and layout for the S2-LP transceiver chip in my own design.I'd like to use a PCB antenna instead of the SMA connector. I've copied the single band antenna design given in a TI app noteDN024. With the matching network on the eval board, could I simply remove the SMA connector and put the PCB antenna in it's place? Ensuring a 50R trace from the matching network to the antenna.
Antenna matching for RF chips - Page 1
Forum section: electronics / projects

author: gxti
author_rank: Frequent Contributor
timestamp: July 10, 2011, 06:44:41 pm
content: I want to use Microchip's MRF49XA transceiver (datasheet:http://ww1.microchip.com/downloads/en/DeviceDoc/70590b.pdf), and like several trx I've run across it has differential, open-collector outputs. This and all the related chips recommend a balun made of a few inductors and capacitors (page 76 in the datasheet) to convert to a 50 ohm, single-ended output. All of these examples, though, are for use with a quarter-wave monopole antenna and don't make any mention of dipole. Do I still use the same balun if I want to use a dipole antenna, for examplehttp://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=ANT-916-CW-HW-ND? The datasheet hints that it can drive a loop or dipole antenna "directly", but also says that coils are required for all antennas due to the open collector outputs. Would something like a Pi filter handle both the coil requirement and the impedance matching? How do I go about choosing values for it?

author: gregariz
author_rank: Frequent Contributor
timestamp: July 11, 2011, 05:45:51 am
content: My approach would be to forget about their recommended matching circuit. Since both outputs are out of phase open collector, I would tie each to your supply rail via identical RF Chokes. The chip says it has an Automatic Tuning Unit in it - I've not used that chip so I can't say how good it is.

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 11, 2011, 08:53:33 am
content: Quote from: gxti on July 10, 2011, 06:44:41 pmi hate to say it but you need a big buck for this. i have a non working radio in stock and have no clue why albeit everything according to datasheet. you may keep try and error with the value, and enthusiasm as your "faith", or you are going to need to measurement device such as spectrum analyzer or vna to measure the signal strength for real. radio is not something you can ask people for the value and expect it to work 100% otimum, my 2cnts from limited experience at least.

author: vk6zgo
author_rank: Super Contributor
timestamp: July 15, 2011, 12:46:03 am
content: The example you gave is an end fed antenna,& probably includes a matching section so it can be driven from a 50 ohm unbalanced output,so you will probably need the balun.A balanced dipole does not need a balun (but may need some matching circuitry),& is nominally of 75 ohms impedance.A folded dipole is a balanced antenna,does not need a balun (but may need some matching circuitry),& is nominally of 300 ohms impedance.You are unlikely to run into the latter two types with commercially available antennas for your application.VK6ZGO
Antenna wire length limit for Bluetooth - Page 1
Forum section: electronics / projects

author: Pack34
author_rank: Frequent Contributor
timestamp: November 21, 2016, 10:14:00 pm
content: Right now I'm attempting to source an adhesive bluetooth antenna with a 200-mm wire. Due to mechanical limitations this will be the best placement for this.I'm seeing a fair amount of 100-mm or less. Does the antenna cable itself need to be less than the wavelength of the signal?

author: Pack34
author_rank: Frequent Contributor
timestamp: November 21, 2016, 10:28:18 pm
content: I'm attempting to find one of these with a length of 200-mmhttp://www.digikey.com/product-detail/en/taoglas-limited/FXP70.07.0053A/931-1074-ND/2332701I was able to find this Molex one, but it looks like it'll be just a hair too short. I think I really need 200-mm.http://www.digikey.com/product-detail/en/0479501011/WM5032-ND/2709380Can anyone help me out?

author: Monkeh
author_rank: Super Contributor
timestamp: November 21, 2016, 10:38:34 pm
content: What's wrong with this?http://www.digikey.com/product-detail/en/molex-llc/0479502001/WM5030-ND/2709378Or this:http://www.digikey.com/product-detail/en/molex-llc/0479502011/WM5033-ND/2709381Or something else from the 109 2.4GHz antennas with 200-300mm tails:Long URL hereQuote from: blueskull on November 21, 2016, 10:20:13 pmSurely if you attenuate loss, you gain?

author: Pack34
author_rank: Frequent Contributor
timestamp: November 21, 2016, 10:47:26 pm
content: I... completely missed those.Thanks!

author: Zero999
author_rank: Super Contributor
timestamp: November 21, 2016, 10:50:04 pm
content: Quote from: Monkeh on November 21, 2016, 10:38:34 pmHe meant, the longer the cable, the more the signal will be attenuated.

author: Monkeh
author_rank: Super Contributor
timestamp: November 21, 2016, 10:50:40 pm
content: Quote from: Hero999 on November 21, 2016, 10:50:04 pmYou know, I can figure that out.
anti-aliasing low pass filter cutoff frequency - Page 1
Forum section: electronics / projects

author: unscripted
author_rank: Contributor
timestamp: June 05, 2024, 03:35:23 am
content: Just for fun and learning, I'm going through this reference designhttps://www.nxp.com/docs/en/application-note/AN13338.pdfOn section 4.3.2 - Phase Voltage Measurement, it is stated that:QuoteHow did they get there? If I'm not missing something, isn't the cutoff frequency determined by R42/C30, fc = 1/(2*pi*220*0.047u) = 16 kHz. Even doing some Thevening to find the effective resistance, it doesn't get to 27.22 kHz. So either I'm wrong or the application note is wrong. I would appreciate a second eye!On the other hand, what would be the cutoff frequency in the second circuit? Is is determined by the effective resistance ~1K and the C2/C3?

author: MasterT
author_rank: Frequent Contributor
timestamp: June 05, 2024, 11:49:27 am
content: Should be (R139 + R42) x C30, about 1.41 kHz. AP Note seems wrong. I also dislike capacitive load on Vref /2 buffer, is it stable ?Regarding second circuits, Diff, 3 caps, check out DS formula Analog Device AD8429 p18
Anti-Static Grounding Mat DIY/Repair - Page 1
Forum section: electronics / projects

author: joshforester
author_rank: Contributor
timestamp: April 28, 2017, 02:31:10 am
content: What's the best place & prices for buying ESD Grommets & Grommet Tools? I have about 10' roll or so of ACL Staticide 8185ESD mat and I'm wanting to make a couple of mats to both keep and sell. Have any of you repaired/made Anti-Static mats, if so what's the most cost effective way to do so?Thanks!
Anti-Vandal Switch with 12mm mount diameter - Page 1
Forum section: electronics / projects

author: 2X
author_rank: Frequent Contributor
timestamp: July 10, 2025, 06:06:12 pm
content: Hi,I want to find an anti-vandal switch with 12mm mount diameter (ar smaller or slightly bigger in worst case). I have search on mouser, digikey, TME but I can't find any anti-vandal switch with 12mm but I didn't find something; only momentary switches. I want to place it on my motorbike (to engage a relay) but the space is very very tight (I want to find a switch with specs and not a chinise).If you have to suggest any another round "small/elegant" switch for external use with some degree of water resistance please tell me.Anti-Vandal Pushbutton Switcheshttps://gr.mouser.com/c/electromechanical/switches/pushbutton-switches/?contact%20form=SPDT~~SPST&switch%20function=OFF%20-%20%28ON%29%2C%20ON%20-%20%28OFF%29%7C~OFF%20-%20ON%2C%20ON%20-%20OFF&type=Anti-Vandal&rp=electromechanical%2Fswitches%2Fpushbutton-switches%7C~Contact%20Form%7C~Switch%20FunctionPushbutton Switches Stainless, Flush Button, Yellow LED ring, Solder terminal, LED 24VDC -Momentaryhttps://gr.mouser.com/ProductDetail/TE-Connectivity-Alcoswitch/AV12F10E524Q04?qs=IKkN%2F947nfCmEeZyMh9TNw%3D%3D

author: kloetpatra
author_rank: Regular Contributor
timestamp: July 10, 2025, 07:11:40 pm
content: https://www.aliexpress.com/item/1005006477375437.htmlhttps://www.aliexpress.com/item/4001172878425.htmlhttps://www.bulgin.com/us/products/stainless-steel-illuminated-vandal-resistant-ip67-push-button-switch-mav0120-series-flush-button-12v-dc-amber-led-dot.htmlhttps://www.te.com/en/product-2488219-1.htmlI tested some of those chinese switches and I think the quality is acceptable.

author: 2X
author_rank: Frequent Contributor
timestamp: July 10, 2025, 08:44:41 pm
content: Quote from: kloetpatra on July 10, 2025, 07:11:40 pmThanks for your reply... as I saw TE and bulgin are momentary and they don't have a latching switch at 12mm.Also, I found:1NO High head Waterproof Metal Push Button Switch LED Light Self-locking/reset 3/6/12/24/220V 8/10/12/16mm Oxidized blackhttps://www.aliexpress.com/item/1005007168217107.html?spm=a2g0o.order_list.order_list_main.10.78d41802aEi3JV

author: 2X
author_rank: Frequent Contributor
timestamp: July 10, 2025, 09:33:27 pm
content: Quote from: kloetpatra on July 10, 2025, 07:11:40 pmHave you ever buy the 8mm switch? Do you know what is the maximum current for the illumination LED in order to calculate the resistor for 12V?It writes:8mm Button8mm Button (which is momentary and no led ) only has Camber Head. Other 8mm button only has High Head.8mm Led button must be connected to the outside resistor when usedPlease allow 0.1-0.3mm differs due to manual measurement,8mm
Anticipated switching noise? - Page 1
Forum section: electronics / projects

author: iampoor
author_rank: Frequent Contributor
timestamp: September 08, 2013, 12:05:59 am
content: Hi!Ive been contemplating using a microcontroller to control transistors as analog switches in low level audio equiptment.Before even embarking on this project, I have a few questions of "anticipation" (AKA: Trying to figure out what the mind boggling issues will be so I dont smash my head through the wall)I am trying to design the quietest system possible. I know a large portion of this will be determined by proper board bussing. Im expecting to use a separate ground for the digital/analog systems, and to use extremely low noise transistors (Anyone have any NPN suggestions to start with?). Also planning on creating the shortest possible trace length between the switching transistors and their respective components. Is it possible to design the PCB with "shielding", like an extra buss that is not connected to anything?What I am concerned about is switching noise and pops while switching resistor/capacitor values. With high speed transistors, will this be an issue? Would it better to implement a short incremental "ramp" while switching values?Sorry if none of this makes sense, please let me know what I need to calirify. Im a newbie and just trying to figure out if my idea is feasible or just plain ole silly!Thanks!

author: Marco
author_rank: Super Contributor
timestamp: September 08, 2013, 12:39:29 pm
content: What kind of current are you switching? For low power you can just get multiplexer ICs designed for audio use.

author: iampoor
author_rank: Frequent Contributor
timestamp: September 08, 2013, 06:10:12 pm
content: Quote from: Marco on September 08, 2013, 12:39:29 pmNot sure on the specifics yet, but it will be well under 100ma, probablly closer to 10ma at most...Hmmmm, do you hae a suggest for a starting point? Looking for the lowest inherant noise possible...preferablly not in a hard to work with package too...
Any 60-pin expansion connector; - Page 1
Forum section: electronics / projects

author: Dinos Tsakalakis
author_rank: Newbie
timestamp: August 27, 2021, 07:10:42 pm
content: Hallo ,resently i started to make a development board but i can not find any type of 60 pin connector that fits here.as also a 2x30 pin connector headers instead.Iam also wondering about ,if i could connect 6 ssq or ssw of 10-pin headers.if you see the screenshot from the dev-board user manual you will see that the j7 is basically a 2 layer 30 pin connector or 60 pin ,so if someone knows the model of this, i also need the schematic and the footprint ,i have attached the question and the the user guid manual of desining the dev board,any answer would be very helpful.

author: mariush
author_rank: Super Contributor
timestamp: August 27, 2021, 07:32:37 pm
content: They look like standard 0.1" pitch headers.Digikey has 306 headers with exactly 60 pins, but you can go to other potentially more common "sizes" like 62 or 64 or 72 or even lower sizes like 50 or 40You being in Europe may prefer Farnell or TME.eu , here's a TME link to 0.1" (2.54mm) pitch male headers, i pre-filtered for you to show only longer headers (20+) :mile long tme.eu link

author: Benta
author_rank: Super Contributor
timestamp: August 27, 2021, 07:59:50 pm
content: You need two 30-pin single row pin headers. That's clear from the PCB silk screen. They look to be 0.1" pitch, those can be found everywhere.
Any data about CST716 capacitive touch controller (or equivalent)???........ - Page 1
Forum section: electronics / projects

author: Smokey
author_rank: Super Contributor
timestamp: January 26, 2022, 09:30:16 am
content: I'm working with a little TFT LCD that has a capacitive touch screen but no onboard controller. They recommend you use a "CST716" touch driver chip on your board. And of course, no data sheet available.I don't happen to be in China, and don't have any hookups, so I'm having a hard time finding any information about this chip. I would very much like to find some equivalent capacitive touch controller that I can actually get in the USA, but I don't even know where to start considering the actual display touch cable just lists "sensor channels 1-10" and ground pins.Anyone familiar with this capacitive touch controller part or know of an alternative that would work with an interface that's just 10 "sensor channels"?

author: Smokey
author_rank: Super Contributor
timestamp: January 26, 2022, 07:40:19 pm
content: "CST716" also happens to be the part number for a toilet... coincidence?https://www.decorplanet.com/products/toto-cst716-carusoe-two-piece-toilet-16-gpf/cst716.html

author: amyk
author_rank: Super Contributor
timestamp: January 27, 2022, 02:21:27 am
content: Search results also suggest it could be similar to CST816S, of which I found some information here:https://wiki.pine64.org/images/2/2f/CST816S.zip

author: Smokey
author_rank: Super Contributor
timestamp: January 27, 2022, 08:36:57 am
content: Cool! That's more info than I had before. Thanks. I'll keep digging.

author: Smokey
author_rank: Super Contributor
timestamp: January 29, 2022, 02:48:51 am
content: Considering how many displays use these touch drivers, data on these parts is hard to come by. It sounds like the primary difference between the CST716 and CST816 is the support for multi-touch and more events in the CST816. Otherwise compatible.This is the CST816S pinout:http://www.pluschiptech.com/web/userfiles/product/big/816.jpgAnd a terrible google translation of the Chinese only datasheet is attached here.This is all I got from the display datasheet about the capacitive touch connector:I did find someone asking a similar question on reddit a while back with no good answer:https://www.reddit.com/r/AskElectronics/comments/r90ei1/help_find_a_replacement_for_cst816_ic/How would I even go about finding something that would work in it's place?(This goes to show you that no matter how much time you spend designing stuff, it doesn't take getting very far from your experience before you have no idea what you are doing.)

author: Smokey
author_rank: Super Contributor
timestamp: January 29, 2022, 03:18:16 am
content: Something like this maybe?Microchip = MTCH6102https://ww1.microchip.com/downloads/en/DeviceDoc/40001750A.pdfhttps://www.digikey.com/en/products/detail/microchip-technology/MTCH6102-I-SS/4790106
any favourite bluetooth audio modules for retrofits? - Page 1
Forum section: electronics / projects

author: gardner
author_rank: Regular Contributor
timestamp: October 09, 2022, 05:15:15 pm
content: I've been retrofitting different audio gear with bluetooth receivers and I've mostly been using cheap ones based on the Jieli AC6925A. These are a pretty mixed bag with varying features and quality. It looks like the Jieli chip is a general purpose MCU and there's no telling what features may have been programmed into it by the manufacturer. All the cheap modules seem to suffer from huge PSU noise issues requiring an isolated PS and I've been using small DC-DC converters for this with good results.I would like to at least have the ability to change the BT module's name and have a contact closure to place it into pairing mode. Ideally it would be great to have a full set of wireable control inputs that you can use or leave out depending on your needs. Maybe settable output levels would be nice.I'm wondering if anyone has identified a source of BT modules with more consistent features than the cheapies from Amazon?

author: DavidAlfa
author_rank: Super Contributor
timestamp: October 09, 2022, 09:23:06 pm
content: I've played with Cambridge Silicon Radio modules (Now owned by Qualcomm) like csra64215, csr8635, adding bluetooth to mine and some friends's cars.Try to get aptX modules, that's the best quality you can get (lossless audio).Since it became Qualcomm, a lot of previously freely available software became NDA or for customer-only.You can still find them in the>web<...Programming them is a bit messy, you need a specific CSR USB-SPI adapter, and the software is a bit tricky.Someone made>bluemagic<, based on a stm32f103 bluepill, emulating the CSR programmer, but the bluepill only "talks" 3.3V, while most of these bluetooth SOCs work at 1.8V, using resistor dividers didn't work.Ended using a TXS108e logic level translator, then it worked.However, these modules get bricked extremely easy, beyond recovery!They feature a 1.8V-only SPI flash, backup its contents before anything else, so on the event something goes wrong you can restore it.Use another TXS108e if your programmer doesn't support 1.8V, I did that way to interface my CH341A.Once you have a backup, there's no fear!I probably bricked it 20 times.On the first try, I changed the bluetooth name, worked nicely... but then touched something else and killed the module, had to buy a second one to dump the flash contents and recover the first one!