hybridfree/eevblog-posts huggingface dataset:
Meeting microphones - Page 1
Forum section: electronics / beginners

author: DALEWP1
author_rank: Newbie
timestamp: February 27, 2025, 01:48:46 am
content: I'm merging two microphones into one helmet so I can have a wired connect to my airband radio and a Bluetooth connection. My plan is to just solder in the leads from the BT mic to the existing mic in my helmet. Do I need to add a diode so one mic didn't break feed to the other? Or is there something else I need to do to make it work correctly?

author: Analog Kid
author_rank: Super Contributor
timestamp: February 27, 2025, 01:53:01 am
content: Diode doesn't sound like a good idea at all.Have you tried just putting them in parallel? That seems the most obvious solution. If they're both the same type (dynamic or electret) that should work.If that doesn't work then you'll have to rig up some kind of preamp/mixer with an input stage for each mike.

author: DALEWP1
author_rank: Newbie
timestamp: February 27, 2025, 03:40:22 am
content: OK. I am basically a newb with all this, so I appreciate it.So, to further my education, why would a diode not be a good idea?

author: Analog Kid
author_rank: Super Contributor
timestamp: February 27, 2025, 04:03:38 am
content: For one thing, it would clip have the signal, distorting it.You don't need to "protect" the microphone from the other mike's signal; it's not going to damage it.Can you temporarily wire them both in parallel and see how that works?

author: themadhippy
author_rank: Super Contributor
timestamp: February 27, 2025, 04:28:01 am
content: Quoteunless ones a ribbon mic and the other needs 48v phantom shoved up it,also paralleling 2 mics that require phantom maybe try and pull to much current from the phantom supply thats limited (or should be) to 10ma

author: Analog Kid
author_rank: Super Contributor
timestamp: February 27, 2025, 05:13:06 am
content: Where in the world do you get 48v. phantom power? The OP's talking about a bike helmet mike and some BlueTooth thing. No ribbon mikes here.

author: CaptDon
author_rank: Super Contributor
timestamp: February 27, 2025, 01:37:57 pm
content: The one problem you may run into would be if one mic is a dynamic and doesn't want any voltage applied to it and the other mic is a FET/Condensor mic and needs a feeble supply voltage and current. That combination simply won't work and could damage the dynamic mic. You may be lucky and both mic input circuits are similar and one mic can indeed feed both devices. A diode blocks current flow in one direction so obviously it is a bad idea since audio is an alternating wave.

author: DALEWP1
author_rank: Newbie
timestamp: February 27, 2025, 05:57:12 pm
content: Oh, sure. That makes sense. So, I can merge these two systems together at the mic and it'll stand a good chance at working. I'll give it a try and see what happens.Thanks for the help and education.
Megger testing a cooker's oven element question. - Page 1
Forum section: electronics / beginners

author: Chris Wilson
author_rank: Super Contributor
timestamp: March 07, 2014, 11:43:10 pm
content: Sorry, not a very exciting question, but we all have to eatOur cooker's bottom oven has started tripping the house distribution panel RCD when the oven has been on for about 10 or 15 minutes. It's not thermostat related I am pretty sure. I have taken the element out and Megger tested it. The Megger will output 500V, although I have a hi-pot tester, too. What sort of reading would you expect a good element to give on the Megger, either terminal to the metal tube around the heater? Infinity? This shows about 1 meg. Obviously I am testing the element cold. Thanks. I am in the UK on 240V 50Hz.

author: Rerouter
author_rank: Super Contributor
timestamp: March 07, 2014, 11:51:23 pm
content: for heating elements the limit is 10K (atleast in aus) as its expected that once it heats up it will drive off its moisture and return to the above 1 Meg value other appliances have to meet,i'm going to assume this is a single phase 230V heating element, in which case 500V is the correct testing voltage, (you may wish to tap the element while testing as when it expands something could be expanding and forming very close to a short)if this is a 2/3 phase element, then 1000V is the correct testing voltage, though it is rarer for a 500V test not to be within the same order of magnitude as a 1000V test,

author: Chris Wilson
author_rank: Super Contributor
timestamp: March 08, 2014, 12:05:45 am
content: Hmm, thanks Rerouter. Sounds like it's well in spec then. Cooker is single phase. Must be a wiring fault, it's an elderly cooker, followers of hi tech kitchen fashion would replace it. Not be a kitchen / bathroom snob, and having a wife that's more suited to work in a crematorium than a kitchen, I am in no rush to buy a new one. I will have to delve behind the rear panel where the wiring hides. Thanks again.

author: SeanB
author_rank: Super Contributor
timestamp: March 08, 2014, 05:03:18 am
content: Might be the element though. Connect it to power while supporting it on some dry bricks and see if it has a current flow through the casing when hot.

author: Chris Wilson
author_rank: Super Contributor
timestamp: March 10, 2014, 10:06:28 am
content: Good idea, thanks Sean.
MEI Analyzer and STS  - Page 1
Forum section: electronics / beginners

author: JimmyMacRod
author_rank: Newbie
timestamp: January 29, 2021, 08:03:50 pm
content: Hi everyone!I'm looking for a copy of the ANALYZER Software tool from MEI used with the VN2000 non flash port and a diagram of the wiring used to connect the device to the computer. Also I would like the wiring diagram of the harness used to connect the MDB Bill and Coin Acceptors to the computer where the STS tool from CPI is installed. I'm trying to fix some units from MEI/CPI. Any information would be appreciated.
Memory address prefix - Page 1
Forum section: electronics / beginners

author: tatel
author_rank: Frequent Contributor
timestamp: January 27, 2023, 05:59:31 pm
content: I was debricking and old TP-Link router via serial console+tftp. I used commands like:Code:erase 0x9f020000 +0x7c0000I know that this is erasing a memory range beginning at 9f020000; the end is 7c0000 bytes after the initial address.I also know that the first 128KiB of flash are reserved for the U-boot partition: and that these 128 KiB translate in hex as 20000So I guess 9f0 is the prefix and 20000 the offsetBut, for the life of me, I can't figure where the 9f0 prefix comes from.I would greatly appreciate any pointers

author: magic
author_rank: Super Contributor
timestamp: January 27, 2023, 07:15:23 pm
content: Not 100% sure, but could it simply be the address where flash is mapped into the CPU's memory address space?It's common for such mapping to exist, and it will appear at some fixed (for a given CPU type or router model) address, usually far away from zero, usually in the upper half of the address space - above 0x80000000.

author: Benta
author_rank: Super Contributor
timestamp: January 27, 2023, 08:18:16 pm
content: You'll need to look at either the address-decoding hardware or (if the system has one) the setup of the MMU.It's very common to boot from ROM at address 0x0 and after initial setup remap the ROM to somewhere else in the memory map.

author: tatel
author_rank: Frequent Contributor
timestamp: January 27, 2023, 09:08:46 pm
content: Quote from: Benta on January 27, 2023, 08:18:16 pmI woul like to know the name of that address-decoding hardware. Would do some Google search for itArchitecture is mips_24kc. CPU is Qualcomm Atheros QCA9558FWIW, here are the commands used:Code:ap135> tftp 0x80060000 wr1043nv2_tp_recovery.binap135> erase 0x9f020000 +0x7c0000ap135> cp.b 0x80060000 0x9f020000 0x7c0000ap135> boot.m 0x9f020000As I understand it:Download binary image, put it at address 0x80060000Erase memory range from address 0x9f020000 to 0x9f020000+0x7c0000copy what is at address 0x80060000 at address 0x9f020000 size is 0x7c0000boot with image located at address 0x9f020000Firmware image has to go right after U-boot partition (128 KiB). So I guess 0x9f020000 maps that. Is this right?Flash layout attached.I would love to know how memory addresses are calculated from the flash layout data

author: Benta
author_rank: Super Contributor
timestamp: January 27, 2023, 09:36:53 pm
content: You're floating at the firmware/software level. I'm talking hardware.But as usual with Qualcomm, trying to get a data sheet is hopeless.

author: tatel
author_rank: Frequent Contributor
timestamp: January 28, 2023, 08:27:23 am
content: Thank you, but I can't really say answer is helpful.Could you give some link to any documentation you consider relevant?Looking around I fell over this serie of YT videos by Ben Eater, I'll have a look at ithttps://www.youtube.com/playlist?list=PLowKtXNTBypFbtuVMUVXNR0z1mu7dp7eH
Memory Depth - scope - Page 1
Forum section: electronics / beginners

author: Bandoneon
author_rank: Newbie
timestamp: March 08, 2019, 03:31:35 pm
content: Hello everybody,I want to measure the memory depth of my scope, is there a possibility to do this? I use a Rigol DS1062CA and I want to do this because I want to check that the manufacturer of the scope is right and if I change the inputsignal I want to look that the memory depth is still the same.I found already this formule on the internet, is this formule right?Memory depth = Sampling rate * time per division * #divisionsWho can help me?Greetz

author: ArthurDent
author_rank: Super Contributor
timestamp: March 08, 2019, 05:09:42 pm
content: I'm not sure you are looking for the right variable. Memory depth for any given scope is given in the specifications and for any trace is divided by the number of channels you have turned on. To maximize memory depth, use one channel if possible. Selecting the highest time/division will help also. The formula is (Memory depth/time per division) x number of divisions = sample rate.https://www.testandmeasurementtips.com/memory-depth-and-sampling-rate-in-oscilloscopes/Here is a good explanation:http://literature.cdn.keysight.com/litweb/pdf/5989-4501EN.pdf

author: ataradov
author_rank: Super Contributor
timestamp: March 08, 2019, 07:50:20 pm
content: Why would manufacturer lie about this stuff? Especially given that specified value is just 10 kpts. It can't go any lower, really.

author: w2aew
author_rank: Super Contributor
timestamp: March 08, 2019, 08:18:51 pm
content: Not all scopes share the memory among channels. In other words, some scopes give you the same maximum available record length regardless of how many channels you have turned on.Also remember that the displays on digital scopes rarely have anything more than 1000-2000 pixels across the screen horizontally. So, even if you capture a waveform using 1Mpoints - depending upon how to view that waveform (zooming in/out, or making measurements, or exporting the waveform for external analysis), the number of points in the waveform may be different that the memory specified for the acquisition.Some scopes give you direct control over how much memory is being used, and will report this value to you somewhere in the user interface. Some scopes don't tell you easily.Also note that some scopes use a decimated set of display point for the on-screen measurements, and some use the acquired samples points in memory - this can fool you sometimes too.Bottom line, you have to take care in how you use the scope to determine the amount of memory used, and how to control it.

author: David Hess
author_rank: Super Contributor
timestamp: March 09, 2019, 05:22:25 am
content: Quote from: ataradov on March 08, 2019, 07:50:20 pmSome manufacturers have lied about or at least misrepresented record lengths as they are a major marketing feature. The instance I am thinking of involved the manufacturer listing the number of *bytes* of record length but with 16 bit samples, this number was twice as high as the number of samples.
Memory IC Identification, (Datasheet Included) - Page 1
Forum section: electronics / beginners

author: andrewlapham
author_rank: Contributor
timestamp: June 21, 2020, 05:13:08 am
content: I have a cheap android car radio i bought off Aliexpress and was thinking up upgrading the memory ICs. Inside i found two RS256M16V0DB.http://szrayson.com/uploadfiles/2020/05/20200519171905651.pdfAre these chips actually 512mb a piece or are they both 256mb? I'm having trouble understanding the datasheet tbh. the android system says it has 1gb installed but just like the fake android version it claims, is it also reporting a fake amount of ram?Thanks.

author: PA0PBZ
author_rank: Super Contributor
timestamp: June 21, 2020, 08:18:29 am
content: The memory chips are 4Gb (Gigabit) each for a total of 8Gb or 1GB (Gigabyte)

author: magic
author_rank: Super Contributor
timestamp: June 21, 2020, 08:56:15 am
content: Is this some sort of common DDR DRAM?Then there is no autodetection for those things. Size and other parameters of the memory (internal geometry, timings) are encoded somewhere in the firmware blob of the SoC.

author: andrewlapham
author_rank: Contributor
timestamp: June 21, 2020, 09:55:44 pm
content: I have firmware on hand for the 2gb version of this device. What was really confusing me is how the memory density is calculated. Its a bit confusing when the phisical ic has 256m printed on it when its obviously a 512mb ic.

author: mikerj
author_rank: Super Contributor
timestamp: June 21, 2020, 10:05:03 pm
content: Quote from: andrewlapham on June 21, 2020, 09:55:44 pmRS256M16V0DB.The 256 relates to the number of words and for this device they are 16 bit words. When expressed as the number of 8 bit words (i.e. megabytes) the number will be doubled.
Memory in a function generator, when is it usefull ? - Page 1
Forum section: electronics / beginners

author: giacomo
author_rank: Regular Contributor
timestamp: May 31, 2017, 10:47:35 pm
content: Hi, i was considering to buy a basic function generator (like a siglent SDG805 or an instek from the SFG-1000 series).But looking at the varios models i think to not understand what is a waveform memory in a function generator and when is it usefull to have a lange amount of memory...

author: SebG
author_rank: Regular Contributor
timestamp: June 01, 2017, 12:04:13 am
content: Usually the memory is so you can store your own arbitrary waveforms. Most function generators will have basic waveforms like sine, triangle, square wave, or some other like gauss or noise. But if it doesn't have what you need then you can create your own and upload it to the function gen. The more memory you get the more points your arbitrary wave can have, ie more resolution.
MEMs and Smart Devices Design Documentation - Page 1
Forum section: electronics / beginners

author: jafacakes
author_rank: Newbie
timestamp: October 28, 2012, 11:48:13 am
content: Hi all, I'm a long-time viewer of the show but first time Forum-user.I am doing my 4th year of an EE MEng here in the UK and one of my modules is asking me to design (and simulate) a MEMs or Smart Device.I would like to ask if anyone knows of a good source of information (e-book if possible) where I can actually see how things like Accelerometers, Pressure Sensors, Gyros etc. are laid out on silicon and the reasons behind one design over another.It is my understanding that this sort of information is critical IP to the companies that design them, which I why I am having such difficulty in finding specific design information (e.g. diagrams of the silicon layout, equations for the changes in silicon properties with physical deformation etc.).Can anyone help me?(n.b. i'm not looking for answers here, just for where to find more information)

author: KedasProbe
author_rank: Frequent Contributor
timestamp: November 01, 2012, 05:55:39 pm
content: Maybe you can get some info from the examples in the simulation softwarehttp://www.comsol.com/showroom/product/mems/If you make an account you can download PDF documentation of the examples.
Merry Christmas - Page 1
Forum section: electronics / beginners

author: alloby
author_rank: Contributor
timestamp: December 25, 2017, 03:01:50 pm
content: I would like to wish all members a merry Christmas and thank everyone for all the help and advice I have received brilliant forum.

author: Cliff Matthews
author_rank: Unknown
timestamp: December 25, 2017, 03:15:01 pm
content: Quote from: alloby on December 25, 2017, 03:01:50 pmTo you and all as well! However we celebrate, may it be calm and happy with friends or family and some satisfying refreshment! Maybe "a cold one" for those live down-unda - apparently it's been very hot!
MESR 100 v2 leads - Page 1
Forum section: electronics / beginners

author: Noidzoid
author_rank: Regular Contributor
timestamp: June 21, 2018, 12:12:03 am
content: Hello one and allCould someone tell me why the leads that came with this meter are so short (I'm assuming there is a reason), and is there any reason why I shouldn't change them for something longer with probes on the end rather than the cumbersome alligator clips that are difficult to use in small spaces.Sorry if this is a dumb question but I really am quite new to this.Many thanks in advance to anyone shedding light on this.

author: wraper
author_rank: Unknown
timestamp: June 21, 2018, 12:42:22 am
content: You'll get more error in readings with long leads. Also if you use long leads, both of them should be attached together to basically make a single cable, otherwise readings will significantly vary depending on the cable position because of series inductance change.

author: Noidzoid
author_rank: Regular Contributor
timestamp: June 21, 2018, 01:21:14 am
content: Thanks for the reply Wraper.Do you mean the wires should be taped/twisted together so they are close to each other but not actually connected (core to core)? If this is the case I will make up a new set. One of the reasons I bought this unit was that I thought it could be used to test capacitors without having to remove them from the board, but the short length and awkward clips don't make it easy.

author: wraper
author_rank: Unknown
timestamp: June 21, 2018, 08:41:37 am
content: You could tape them together at say each 10 cm of distance.

author: Noidzoid
author_rank: Regular Contributor
timestamp: June 21, 2018, 07:34:44 pm
content: Quote from: wraper on June 21, 2018, 08:41:37 amMany thanks Wraper much appreciated

author: hugo
author_rank: Regular Contributor
timestamp: June 22, 2018, 12:17:13 am
content: Quote

author: Noidzoid
author_rank: Regular Contributor
timestamp: June 22, 2018, 06:54:22 am
content: Would twin speaker cable be suitable? There would be no need for the tape. Banana one end, pointy probe the other.
Metal core (aluminum) prototype boards from China? - Page 1
Forum section: electronics / beginners

author: Kester
author_rank: Newbie
timestamp: May 01, 2020, 08:29:06 pm
content: Hi Everyone,I'm getting into LED lighting, and I thought it would be cool to design my own metal core PCB to mount surface mount LEDs on. My hope is that a large PCB can replace a heatsink, and ordering a custom one will give more more flexibility regarding LED placement and having individually addressable LEDs than buying a premade one. I see that many Chinese PCB manufacturers have the option for metal core in their online forms, but some also say to contact them directly regarding metal core PCBs in their FAQs. So I'm wondering if anyone has ordered a metal core PCB from one of these manufacturers (JLCPCB, NextPCB etc) and whether the process is as simple as regular FR4 boards.Thanks in advance for your help,Kester

author: floobydust
author_rank: Super Contributor
timestamp: May 01, 2020, 09:41:13 pm
content: I have done MCORE withPCBWAYfor some LED lighting projects. I was really happy with them, good quality and the routing, holes (for mounting) really good. Would use them again.The LED's used were Cree XP-E and 3W beads. The tough part is soldering them because the boards take an incredible amount of heat. Tried hot air and overheated some LED's and then a reflow oven works but with a bit extra hold time due to the delayed heating of the boards compared to FR4.This is the hardest part, putting the boards together with expensive LED's, costly when you roast them or the silicone lens melts.

author: xavier60
author_rank: Super Contributor
timestamp: May 01, 2020, 11:04:57 pm
content: Quote from: floobydust on May 01, 2020, 09:41:13 pmI got some 138°C solder paste for doing LED replacements on aluminium PCBs, I haven't actually used it yet.https://au.element14.com/mg-chemicals/4902p-15g/no-clean-solder-paste-138-deg/dp/3018417

author: Kester
author_rank: Newbie
timestamp: May 01, 2020, 11:30:55 pm
content: Thanks floobydust and xavier60, I will definitely try this then, with low temp solder paste. This changes my plans a bit. My original plan was to start with premade boards and work my way up to custom boards. But if ordering the board is straightforward I can start with a custom board and smaller (cheaper) LEDs and work my way up to larger LEDs.The bigger plan is to have plant grow lights that also function as room lights, controlled with an MCU. Custom PCBs help a lot with getting the aesthetic I'm looking for.
Metal Dome (aka snap dome, tactile dome) Supplier - Page 1
Forum section: electronics / beginners

author: Oanu
author_rank: Newbie
timestamp: April 11, 2015, 11:50:07 pm
content: Hello Everyone,I'm trying to design a low-profile, mini keyboard. As part of this, I am trying out different ways to make the keys switches. One of the better ways seems to be making the switches out of metal domes resting on the PCB and creating a silicone or rubber mat to go on top of it.An example of the metal domes:My problem is that I'm having a hard time figuring out where to buy low quantities of them. Even though they seem to be somewhat generic, I can't find anywhere to directly buy them. All of the manufacturers have samples, but it doesn't feel like the proper channel to get them.In summary, how/where do I buy low quantities of metal snap domes?

author: free_electron
author_rank: Super Contributor
timestamp: April 12, 2015, 01:04:05 am
content: SNAPTRON

author: dcel
author_rank: Regular Contributor
timestamp: April 12, 2015, 01:05:36 am
content: First where are you? Second, Welcome to the forum!Snaptron in Colorado is where I just sourced mine from. They have a design sample kit you can order online. I placed the order and hadn' t hears from them, or got the samples, so I called them, very helpful.Give them a try.Chris

author: Oanu
author_rank: Newbie
timestamp: April 12, 2015, 03:07:56 am
content: Quote from: dcel on April 12, 2015, 01:05:36 amI'm currently in Canada, but moving to the States soon-ish. Also, thank you, I've been registered on the forum for 3 years, I just haven't posted.Snaptron has what I want, but I felt that around 50 was too many to sample, but not enough to actually place and order. Do companies like that do business with hobbyists?

author: amyk
author_rank: Super Contributor
timestamp: April 12, 2015, 04:21:13 am
content: 50 is by no means a large amount... these are usually sold in bags of 1000+ or more.

author: Ian.M
author_rank: Super Contributor
timestamp: April 12, 2015, 04:35:26 am
content: Snaptron seem to actively discourage resellers/distributors. There aren't even any on EBAY. Can anyone suggest alternatives that can actually be ordered in reasonably small quantities (e.g bag of 100)?

author: PeterFW
author_rank: Frequent Contributor
timestamp: April 12, 2015, 06:41:56 am
content: Quote from: Oanu on April 11, 2015, 11:50:07 pmThe same question is on my mind, i have settled on something like this:http://www.ebay.com/itm/50x-Tact-Switch-SMT-SMD-Tactile-membrane-PUSH-Button-switch-SPST-NO-4x4x0-75mm-/161184149182Those are cheap china parts, but the same type you get from name brand companys.But those might be too large for your application.

author: Oanu
author_rank: Newbie
timestamp: April 14, 2015, 02:27:52 am
content: Quote from: PeterFW on April 12, 2015, 06:41:56 amThose are a good size, but I've found others on Mouser that seem like they would work a bit better, for hardly much more money:http://ca.mouser.com/ProductDetail/CK-Components/PTS540-JM035-SMTR-LFS/?qs=sGAEpiMZZMsgGjVA3toVBPOYV%2f7yxh9MHsqsFwP8JLI%3dIt's also nice to order parts from a more reputable/reliable company.
Metal enclosure grounding - Page 1
Forum section: electronics / beginners

author: rfguy2020
author_rank: Contributor
timestamp: October 31, 2024, 12:43:19 pm
content: Hi,I have problem similar to this:https://electronics.stackexchange.com/questions/455276/shielding-and-ground-loops-rf-panel-jacks-for-gpsI'm designing PCB and I would like to connect heat sink to the case and then I have some coaxial RF connectors (operating frequency 600MHz - 1300MHz). Then I have some IO/ethernet/USB/Power connectors. I have metal enclosure.I'm concerned about EMC issues. According to my understanding, the best practice would be connect connector shields and mounting screws through 1Mohm resistor in parallel with capacitor to signal ground. There was some suggestions to use isolated coaxial connectors, but I still have my heatsink connected to signal ground and chassis ground. I have not seen isolated coaxial connector used in many products. I'm not sure if isolated coaxial connector is actually causing more EMC problems.Would it be the best option to connect heatsink, coaxial connector and other connector shields to signal ground as low impedance as possible?Or should I try to have high DC impedance between signal ground and chassis ground (through resistor parallel with cap)? I guess it might be possible if heatsink is anodized and I would use isolated coaxial connectors.

author: selcuk
author_rank: Frequent Contributor
timestamp: October 31, 2024, 01:40:36 pm
content: Usually a low impedance ground connection is better for EMC purposes. You may read the message and the document in the link to see the difference between direct connection and using parallel components. This information is not specific to RF connectors by the way.https://www.eevblog.com/forum/projects/why-usb-c-gnd-is-being-connected-to-the-shield-of-the-cable-after-connecting/msg5269563/#msg5269563

author: Terry Bites
author_rank: Super Contributor
timestamp: November 01, 2024, 01:49:48 pm
content: Your RF io is low impedance, say 50R?In that case (no pun intended) do ground loops really matter?Is this a concern or an observed problem.An isolated connector allows you to float the input/ output. Why would you do that. All RF grounds need to be tied together with a low impedance path.If they don’t then there's a high chance that the grounds will either be susceptible to or create RFI.
Metal etcher with an H-bridge - Page 1
Forum section: electronics / beginners

author: matn1
author_rank: Newbie
timestamp: December 04, 2018, 05:52:51 pm
content: Greetings!I have been learning electronics on the fly, partly from EEVBlog and other sources.I am also a part time knife maker, where I have had the requirement to etch metal.This process is normally accomplished with DC 24v at about 1.5A current to remove metal, and then switch to AC to darken the etch. This is done using a piece of felt dipped into an electrolyte, generally salt water. Anyhow: works ok with my lab PSU for DC and then switching to a big block transformer for AC, but then thats not a fun integrated solution is itSO: I've begun, through trial and error and magic smoke, to design a microcontroller based version of this which would allow me to switch from AC to DC and also alter output voltage. Thus far, I have finished the variable DC voltage part, but am now facing an issue where I would actually like to prevent the circuit from going above 2A output, whether its in DC or AC. By that token, I also want to prevent the system from failing due to a short of the 2 output leads.I have drawn what I have built in Eagle, and I am attaching a screenshot of my circuit thus far (I have mediocre Eagle skills to this day).Could anyone comment on what I could do to impose a max current of 2A along with shield this against shorting the leads?Somehow I dont think controlling current via code would be timely enough as opposed to hardware control. Perhaps that perception is wrong however...Thanks!

author: daveatol
author_rank: Regular Contributor
timestamp: December 06, 2018, 05:30:08 am
content: The LMD1820 has a current sense output, which you can use in conjunction with a comparator (possibly the one in the microcontroller) and reference voltage to trigger the LMD1820 BRAKE line when current is >2A. You'd then want an inductor in series with the etching output to slow the rate of change of the current when the brake is applied/removed (otherwise the current will just oscillate between MAX and 0A).
Metal Oxide Varistor Selection? - Page 1
Forum section: electronics / beginners

author: Banksy
author_rank: Newbie
timestamp: June 17, 2020, 06:52:29 am
content: Hi EveryoneI'm fitting an Access Control Panel with a mag lock and coded key entry etc. The main panel will supply power to Maglock without the need for a separate power supply but its necessary to fit a Metal Oxide Varistor across the power lines in the MagLock to suppress Transient voltages. But I'm stuck with the Math and haven't a clue which one to fit?The MagLock draws 420mA @ 12 Volts The power supply for the panel delivers 14.3 Volts @500mA PLEASE can anyone suggest an MOV for the purpose and a part number or suitable source?I would be extremely grateful! Thanks everyone.

author: Vovk_Z
author_rank: Super Contributor
timestamp: June 17, 2020, 08:24:01 pm
content: There is at least several variables you have to take into account. I can't remember all of them at moment, but at least you have to start from: what voltage is dangerous for you device and what voltage gives your power supply with zero load (is it regulated or not).Then you have to study a little about MOVs parameters.

author: Banksy
author_rank: Newbie
timestamp: June 20, 2020, 10:46:39 am
content: Thank you for taking the time to reply and for your help Vovk_z)) Much appreciated.

author: Vovk_Z
author_rank: Super Contributor
timestamp: June 20, 2020, 02:59:05 pm
content: Here is a document from TDK:SIOV metal oxide varistors. Selection procedure
metal ring on joint PCB  - Page 1
Forum section: electronics / beginners

author: zennon
author_rank: Newbie
timestamp: July 08, 2018, 05:00:25 pm
content: New to soldering, tried to desolder a mouse switch on a PCB. I thought i did a good job, but it's not working with the replacement. I did change it with a different brand of switch so not sure if that's the reasonORwhile desoldering, i removed also a metal ring from the joint in the back of the PCB? Is that an issue? That joint, the solder doesn't stay down but form like a bulb. If that the problem, which is most likely, is there a way to replace that metal ring? I thought most contact and circuits are on the front side of a PCB?

author: JS
author_rank: Frequent Contributor
timestamp: July 08, 2018, 05:46:06 pm
content: Don't worry too much, if there is connection to that place from both sides of the pcb solder a very thin wire from the switch side crossing to the other side, put the switch in place, solder the switch and the thin wire to whatever is left on this bottom side.JS

author: zennon
author_rank: Newbie
timestamp: July 08, 2018, 06:00:13 pm
content: Here is a pic. Somehow the eyelets of BOTH middle joints came off when using the pump. The other ones are good, so don't know if i did something wrong or they weren't firmly attached to the board initially. How do you repair those eyelets? They are like 3mm? I have a different board that i could pull some out probably but is it possible and if so how to remove?

author: JS
author_rank: Frequent Contributor
timestamp: July 08, 2018, 06:02:04 pm
content: Overheating lift pads, not rare to happen, as I said don't worry too much and ensure conections with bodge wiresJS
Metallized Polyester Film Capacitors - Page 1
Forum section: electronics / beginners

author: SG-1
author_rank: Regular Contributor
timestamp: February 19, 2011, 12:07:27 am
content: The capacitor has a DC rating, but neither end is marked +/-http://www.vishay.com/docs/42091/v430p.pdfWorks either way ??A .47micro-F is being used in parallel with a 400V 40A diode in a 125VDC circuit.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: February 19, 2011, 12:44:08 am
content: These caps are non-polarised, so can be used any way round.Only caps that use 'special' dielectrics to achieve high capacitances are polarity sensitive - e.g. electrolytic, tantalum, aluminium polymer.

author: SG-1
author_rank: Regular Contributor
timestamp: February 19, 2011, 01:55:29 am
content: Well now, that just takes all the potential for excitement out of this circuit !Thank you very much.

author: Zero999
author_rank: Super Contributor
timestamp: February 19, 2011, 09:50:38 am
content: Yes they're non-polarised and note how much larger they are than electrolytics of the same value and voltage rating.
Meter Movement - Page 1
Forum section: electronics / beginners

author: codingwithethanol
author_rank: Regular Contributor
timestamp: September 01, 2019, 01:57:31 pm
content: I was fiddling around with magnet wire and was trying to make some diy relays, and I had the idea to try to make a analog meter or something else interesting. After a bit of googling I found nobody else even attempting this, simply "lol buy a meter movement from china and bias it". Is there something inherently complicated about it or do my google-fu skills suck? For example, there are plenty of videos showing how to make diy relays, heres one:heres another:whereas this is the best I could find for making a meter movement, but its basically just a current indicator not really a "meter" per se:

author: codingwithethanol
author_rank: Regular Contributor
timestamp: September 01, 2019, 05:32:41 pm
content: Bumping the thread since no one has dropped by. Just for the cynics, I'm not trying to make a serious functional meter, just a little dinky proof-of-concept thing that rotates in proportion to current or voltage. My question is why nobody has come up with a simple little way to DIY this, as I have seen relays and mini steam engines made from random bits and bobs.
Meter readings (mA,V) - Page 1
Forum section: electronics / beginners

author: gregfox151@gmail.com
author_rank: Contributor
timestamp: March 17, 2013, 05:59:36 pm
content: Hi,I have a panel meter that reads in volts, from 00.01 up to 30 volts.I also have a circuit I want to connect it to, that puts out 0-199 mV.When I connect to the circuit and try to read say, 140mV, my meter reads 00.01.Is there any way (other the easy way out, of simply getting a meter that reads in mV) for me to be able to read the 140 mV more precisely?I thought of an H bridge or something along those lines, but ahhh, the must be an easier way.Any thoughts appreciated.

author: Simon
author_rank: Unknown
timestamp: March 17, 2013, 06:38:51 pm
content: you need to find out how to alter the meters settings, or it has one scale only and your stuffed

author: toster
author_rank: Contributor
timestamp: March 17, 2013, 06:42:10 pm
content: wouldn't an op-amp do?

author: gregfox151@gmail.com
author_rank: Contributor
timestamp: March 17, 2013, 06:43:48 pm
content: op amp? how would you use it?

author: Simon
author_rank: Unknown
timestamp: March 17, 2013, 06:44:40 pm
content: not really as the meter reads on a certain scale, amplifying the value will just mean that the scale will be all out and you've changes the meter, say he does a x10 on it that means it now only good to 3V and misreads everything

author: qno
author_rank: Frequent Contributor
timestamp: March 17, 2013, 08:05:41 pm
content: usually these meters have a full scale of 320 mV or 400 mV.With a voltage divider and a variable decimal point you can expand the range.Check for a part of type number.Google for data. Usually the manufacturer wants to sell as much as possible by showing how easy it is to use the part in the datasheet.You have to change the input voltage divider and change the position of the decimal point.
meter trouble - Page 1
Forum section: electronics / beginners

author: glee
author_rank: Contributor
timestamp: September 28, 2012, 01:39:49 pm
content: I bought an 87-V meter from eBay which doesn't read current correctly. I replaced the fuses today but this did not fix the problem.Example: dial up 8V from a power supply and run this across a 1k resistor; PS shows 8mA, 87-V reads 8V, $15 RS meter reads 8mA, all as expected.But if I reverse the roles of the meters: 87-V shows 160mA, RS reads 7.99V.Under manual ranging the 87-V continues to show "16" values. ie: on 60mA range it shows 0.16mA, on 600mA range it shows 1.6mA, on 6A range it shows 0.16A.I retested the fuses and they are fine. Inspecting the board shows nothing obviously out of place (to the naked eye).Can anyone suggest next steps for troubleshooting?Thanks.

author: saturation
author_rank: Super Contributor
timestamp: September 28, 2012, 02:38:22 pm
content: Check if the error isconsistentacross different resistors and voltages, if it is and all you need do is add or substract an offset, then its just badly off calibration.
method for eliminating the oscilloscope noise signal - Page 1
Forum section: electronics / beginners

author: arivel
author_rank: Regular Contributor
timestamp: May 08, 2024, 08:35:48 am
content: Hi everyone .I have a rigol DS1202z-e oscilloscopelately I have to make alternating current voltage measurements but the PP voltage to be measured is very small, it is in the order of mV.the disturbing signal overlaps and mixes on the screen with the small signal that I am interested in measuring and displaying.Is it possible to eliminate the disturbing signal from the screen?.

author: RoGeorge
author_rank: Super Contributor
timestamp: May 08, 2024, 08:39:23 am
content: Might be. If you have some other good-enough signal (in sync with the noisy one), then use the averaging mode instead of normal acquisition:https://www.eevblog.com/forum/projects/oscilloscope-with-trace-averaging-as-a-lock-in-amplifier-(rigol-ds1054z)/

author: Vovk_Z
author_rank: Super Contributor
timestamp: May 08, 2024, 09:04:57 am
content: 1. Make sure 20 MHz bandwidth limit is switched on.2. O-scopes in general are not good for accurate measuring low signals.You may use AC milivoltmeter for accurate AC voltage measurements (average voltage or RMS but not Peak-to-Peak). Oscilloscopes are more for observing signals but not for measuring.But there are new 12-14 bit digital scopes which I guess are better with this (with what you want).As for me, I use o-scope together with AC millivoltmeter, AC microvoltmeter and a very good soundcard (as spectrum analyser) to make low-noise measurements and research.

author: Roehrenonkel
author_rank: Frequent Contributor
timestamp: May 08, 2024, 09:35:42 am
content: Ciao arivel,your signal is too weak, so make it bigger ((pre-)amplify).You can also try to filter out the noise (bandpass-filter on your signal).What probe / shunt are you useing?Where is the noise comming from?Good luck

author: pdenisowski
author_rank: Super Contributor
timestamp: May 08, 2024, 10:47:52 am
content: Quote from: RoGeorge on May 08, 2024, 08:39:23 amThis. If the "desired" signal is deterministic and the noise is randomly distributed, averaging might help (a lot).Most scopes (even my old analog Hameg scope) support averaging, so it's a cheap and easy thing to try.

author: arivel
author_rank: Regular Contributor
timestamp: May 08, 2024, 01:25:51 pm
content: thanks for the replies.the probe is the one supplied with the oscilloscope, nothing esoteric.in my opinion the noise is that of the electrical supply (room wiring 50 Hz 220 volts) and the circuit that I have to analyze most likely functions as an antenna.Maybe it's better to explain what it is. I should have done it right away. I attach image.it is an AC current sensor that detects a voltage by induction of the current flowing in a piece of linear conductor (rogovsky coil variant).
Method of making PCB ? - Page 1
Forum section: electronics / beginners

author: Nhan95
author_rank: Contributor
timestamp: April 11, 2015, 06:27:42 am
content: Hi. I often make Pcb by ironing method. But it is easy to damage when you iron it and depend on kind of paper yu use. So is there any other method to print the circuit on the board easier

author: DarkZero
author_rank: Regular Contributor
timestamp: April 11, 2015, 02:50:14 pm
content: Hello !

author: Cherry
author_rank: Contributor
timestamp: April 20, 2015, 11:54:01 am
content: Hope to get more information!

author: mayor
author_rank: Regular Contributor
timestamp: April 21, 2015, 12:44:11 am
content: The best method for me has been to use negative film photoresist + print transparencies + uv exposure. It _sounds_ more complicated than it is (in my mind, it's much simpler, and much more accurate, than the paper method).1. Buy UV leds on eBay (cheap)2. Build an array of these on a perf board, power using whatever power supply you have3. By dry film photoresist (http://www.digole.com/index.php?productID=228,for example)4. Buy printer transparency sheets5. Print negative artwork6. Apply photoresist (low heat, low pressure) and uv expose for ~1-1.5m(If you are willing to spend money, you can avoid many of the previous steps buy using pre-sensitised boards)7. Develop using sodium carbonate (easy to find, it's a common swimming pool chemical)You can also buy dry solder mask film and use the same method. This produces pretty good results.I can dig up some notes if there is interest. Here's a snap of my latest result. Photo doesn't do it justice, oxydation on pads is unrelated (out of date Liquid Tin is my guess!)
methods used to make electronics waterproof - Page 1
Forum section: electronics / beginners

author: m4rtin
author_rank: Regular Contributor
timestamp: January 27, 2013, 05:47:29 pm
content: I have aNokia 3720 Classicwhich is compatible withIP54standard. This means that phone has to cope with a following liquid ingress protection test:Code:Water splashing against the enclosure from any direction shall have no harmful effect.Test duration: 5 minutesWater volume: 10 litres per minutePressure: 80–100 kPaHowever, this particular phone has uncoveredcharging portandspeaker. How is it ensured that liquids do not reach electronic components through those holes? In addition, am I correct that waterproof devices use some sort of waterproof coating on the PCB?

author: Bloch
author_rank: Unknown
timestamp: January 27, 2013, 07:08:16 pm
content: Quote from: m4rtin on January 27, 2013, 05:47:29 pmMaybe by using waterproof partshttp://uk.farnell.com/visaton/k64-wp-8ohm/speaker-2-5-waterproof/dp/5095463

author: FenderBender
author_rank: Super Contributor
timestamp: January 27, 2013, 07:55:25 pm
content: Quote from: m4rtin on January 27, 2013, 05:47:29 pmYeah it's usually called "conformal coating".

author: saturation
author_rank: Super Contributor
timestamp: January 27, 2013, 09:35:53 pm
content: For IP 54, jacks, keyboard, LCD screen, speaker etc., must have an equivalent of a gasket seal and exposed surfaces are themselves water resistant. Its "resistant" because its 'water proof' only under certain conditions.The water resistance in this case is just the equivalent of spraying this device 360 degrees at 10L/min at atmospheric pressure, not submersion underwater. I would presume the charging female jack has a cut off switch so the inputs are disconnected until a male jack is inserted into it. IP54 is the least protection for using a device in the rain or marine environments, such as boats.The conformal coating protects PCB and its components against moisture [ such as high humidity in a ship], dust, mold and other contaminants but most are not specifically designed to be immersed in standing water, the casing should do that. Coating are not as easy to guarantee as a protective chassis, which can be easily be rated for true submersion in water for unlimited duration at a specified depth.http://www.procoatus.com/faq.html#conformal-coatings-protect-against
Metrology (?) question. - Page 1
Forum section: electronics / beginners

author: firewalker
author_rank: Super Contributor
timestamp: September 07, 2014, 10:13:14 am
content: I was reading some question in order to prepare some students for a test. One question (translated) is:QuoteThe answer (don't even know if it is correct. In fact I don't now if the question is correct) is the above drawing, with no explanation.I search every book I own with metrology, electrical measurements errors and instruments. I could not find any relative reference to the above.I can understand the point at 200,2. 1% relative error at 200V is 2volts. I can understand the graph starting a 0,0 as the 0 volts Zero Offset. Is the point at 300,5 a sum of relative error and absolute error?Alexander.

author: Simon
author_rank: Unknown
timestamp: September 07, 2014, 10:23:58 am
content: Quote from: firewalker on September 07, 2014, 10:13:14 amSounds like something out of the BTEC L3 course that I stuffed back at the providers due to it's inadequacy, where did it come from ? not that I'm an expert but makes no sense to me. if you have a "possible " error surely the graph should have more than one curve showing the expected ideal behavior and then ideally two dotted lines to illustrate the possible extremes the measurement could come out as given the tolerances stated. Giving a tolerance means that there will be no certain line but one you can hope to achieve and the possible extremes due to real world behavior. That is at least how thermistor manufacturers illustrate and graph the results from their sensors.

author: firewalker
author_rank: Super Contributor
timestamp: September 07, 2014, 10:49:38 am
content: It is from a set of ~300 of question that the candidate must be familiar with in order to succeed to the tests and obtain a technicians license.Alexander.