hybridfree/eevblog-posts huggingface dataset:
Why Sweeping Spectrum Analyzer Circuit Needs More Than One LO? - Page 1
Forum section: electronics / beginners

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 26, 2018, 04:22:10 pm
content: i'm learning SA topology... my curiosity is, why need 2 (or even more) Local Oscillator in the design? why cant just use one LO? in example diagram below, at the end after 3 LOs, the 10.7MHz signal is processed. why cant just use one 10.7 - 1010.7MHz VCO or if its too odd, use one 10-1010MHz VCO and process the 10MHz signal after RBW filter?and while i'm at it. if you have more room to answer, this is the 2nd but less important question... i heard about phase noise (LO's?) business. whats about it? i mean how it can affect the SA accuracy? or noise level? or whatever the fuzz is? thanks for your time.https://en.wikipedia.org/wiki/Phase_noise

author: Tomorokoshi
author_rank: Super Contributor
timestamp: March 26, 2018, 04:37:23 pm
content: A lot of it comes down to how wide the frequency range is of the device. A spectrum analyzer can be thought of as a very wide-band tunable radio.Here is a nice overview of a dual local oscillator approach to radios:http://www.radio-electronics.com/info/rf-technology-design/superheterodyne-radio-receiver/double-superheterodyne-receiver.php

author: w2aew
author_rank: Super Contributor
timestamp: March 27, 2018, 12:36:25 am
content: The answer can get complicated pretty quick. But, the main reasons have to do with achieving high dynamic range, good image rejection, good dynamic range, good frequency accuracy and low phase noise.For example, to get good image rejection, you want the conversion images to be far away from the IF frequency to make them easy to filter at the front end. Since the images are 2x the IF frequency away, the higher the IF the better. But, in order to get good selectivity (low RBW), you want the IF to be low frequency. You also have to consider the difficulty of getting low-noise, high-accuracy/stability LOs - much more difficult to do for very wide frequency ranges.These are a few of many reasons that multiple conversion stages are used in Spectrum Analyzers (and receivers, etc.)

author: BrianHG
author_rank: Super Contributor
timestamp: March 27, 2018, 01:23:59 am
content: I remember one of my first home made spectrum analyzers. I ended up using an old trashed TV tuner which had DC control in which swept the tuner from 30MHz at 0v to 1.2GHz at 22v. The output was a 45Mhz IF stage. I had a 45MHz 6MHz bandwidth saw filter there & an AM TV IF tuner there, and off of that, 2 different 4.5Mhz filters for really narrow band visualizations. The first-LO coming out of the TV tuner was already pre-scaled down /16 if I remembered correctly.I know that the tuner's internals were complicated to be able to tune and go through a 1Ghz span with a single voltage sweep, without any band switching like most more modern compact TV tuners. The number of coils and copper strips & posts inside, all bent and tuned by mechanical position, doing most of the work, is a nightmare & I didn't touch anything inside there.
Why the elaborate metallic case on some SMD polyfuses? - Page 1
Forum section: electronics / beginners

author: lpc32
author_rank: Frequent Contributor
timestamp: April 10, 2015, 10:08:39 pm
content: What's the idea behind the shape of SMD polyfuses like the following?

author: Zero999
author_rank: Super Contributor
timestamp: April 10, 2015, 10:14:27 pm
content: There is no case. What you have there is the semiconducting PTC resistor element sandwiched between two metal plates.

author: Simon
author_rank: Unknown
timestamp: April 11, 2015, 06:58:02 am
content: standard sheet metal

author: Ian.M
author_rank: Super Contributor
timestamp: April 11, 2015, 07:25:53 am
content: The PTC element's bulk resistivity is too high, so a large area thin layer is used to reduce the resistance to something useful for a fuse in the rating desired. The metalwork is only what's needed to make contact to the element, spread the heat to prevent hot-spotting and premature tripping, and keep it off the board (apart from the ends) for predictable thermal behaviour.

author: lpc32
author_rank: Frequent Contributor
timestamp: April 11, 2015, 02:01:18 pm
content: Still, oddly shaped, no? Usually components come in neat little "sealed" packages.Also, that's not the only package for polyfuses. There are more standard looking ones, such as these:

author: SeanB
author_rank: Super Contributor
timestamp: April 12, 2015, 08:47:05 am
content: The first will have a larger current rating, while the small flat ones are low rated, and also require a specific board pad layout, traces to and from that are a specified width and a specified solder amount to get the trip rating within the specs. The others are wire ended, so that you have basically the first fuse with no shaped metal to make it SMD, just the 2 wire leads and a conformal coat for extra protection and the ability to survive a pick and place machine grippers.

author: lpc32
author_rank: Frequent Contributor
timestamp: April 16, 2015, 04:29:40 pm
content: Presumably you could make the smaller SMD ones a smaller version of the one in the top post, or the large one a supersized version of those SMDs. So I'm still puzzled.
Why the redundant Fuse and redundant rectifier diode(Series) - Page 1
Forum section: electronics / beginners

author: Sultanpepper123
author_rank: Regular Contributor
timestamp: March 24, 2020, 09:34:36 pm
content: Hello,I would appreciate if someone would share his thoughts on why would someone put a fusible resistor in series before an NTC ? . Also in the rectifier diode stage there are two extra series diodes in each branch (L1,L2,L3 & N), i tried to simulate the series diode in LTspice and i could not find any noticeable difference ....For more information on the circuit for context , this a 3 phase AC/DC power supply used in a reference ATSAM4L electricty meter.Thanks in advance

author: Yansi
author_rank: Super Contributor
timestamp: March 24, 2020, 09:40:55 pm
content: The fusible resistor is there due to the presence of varistors (MOVs) as an overvoltae protection. If a large enough surge comes by, resistors will open to prevent risk of fire (failed MOVs usually end up dead short)Doubled diodes are likely either due to voltage rating or more likely due to some safety standard so that requires the circuit to be single fault proof. Any diodes shorted will not end up with a big bang.

author: Gyro
author_rank: Super Contributor
timestamp: March 24, 2020, 09:48:42 pm
content: Agreed, I think you answered your own question, at least partially, in your thread title... Redundancy (against critical component failure) and safety (the fusible resistors) where redundancy can't be applied.

author: Sultanpepper123
author_rank: Regular Contributor
timestamp: March 24, 2020, 10:06:23 pm
content: Quote from: Yansi on March 24, 2020, 09:40:55 pmThank you for sharing your thoughts, It is unclear to me any idea what is the use of the NTC here ?Quote from: Gyro on March 24, 2020, 09:48:42 pmThank you sir for sharing your thoughts, makes sense.

author: Yansi
author_rank: Super Contributor
timestamp: March 24, 2020, 10:11:57 pm
content: The power supply module contains inpput filtering capacitors - no surprises. You need to limit the peak current charging the caps. This should be obvious stuff.

author: Sultanpepper123
author_rank: Regular Contributor
timestamp: March 24, 2020, 10:16:21 pm
content: Quote from: Yansi on March 24, 2020, 10:11:57 pmi am aware of the inrush current phenomenon, my question which was poorly put together is why use 2 fuse mechanisms , shouldn't the fusible resistor be enough for the MOV during a fault and for the inrush ?

author: Gyro
author_rank: Super Contributor
timestamp: March 24, 2020, 10:40:45 pm
content: Without the NTC thermistors to limit the inrush current, the fusible resistors would probably need to have a higher power rating, reducing protection of the MOVs.

author: Sultanpepper123
author_rank: Regular Contributor
timestamp: March 24, 2020, 10:46:01 pm
content: Quote from: Gyro on March 24, 2020, 10:40:45 pmThanks for clearing that up , really appreciate it
why the stator magnetomotive force lags behind stator armature current in salien - Page 1
Forum section: electronics / beginners

author: khatus
author_rank: Regular Contributor
timestamp: February 21, 2019, 02:07:47 am
content: https://circuitglobe.com/two-reaction-theory-salient-pole-synchronous-machine.html?fbclid=IwAR1ODRDONC27LIL83Lvb3WohPaSrIG4BRZ8l-ATyeloZEqrZ6juKw__jNMQHello guys in two reaction theory of salient pole alternator when a lagging power factor load is connected to the armature, why the stator magnetomotive force Fs a.k.a MMF lags behind Ia(stator armature current) by angle 90 degrees??.AsMMF = Curremt X number of turns in stator coil.So MMF should be in phase with armature current.
Why there is a PLL next to VCO in Siglent SSA3021X ? - Page 1
Forum section: electronics / beginners

author: jimon
author_rank: Regular Contributor
timestamp: June 24, 2016, 09:37:40 am
content: Noobie here, so if you watchedyou might notice some PLL business next to main VCO.As I understand VCO generates first LO, and it's feed to first mixer, but than there is coupling to input (or is it output) of PLL next to VCO. Why do they have it there? To lock main VCO to 10 MHz ref somehow?There is also second LO in bottom right corner, which is free running(?)/locked to main 10MHz ref(?) which feeds second (1:1) and third mixers (4:1).Another question - tracking generator there also have a separate PLL? As I understand we just need to mix first LO down to spectrum's analyzer input working frequency. Does it mean that tracking generator PLL always generate same frequency? aka 1st_LO_freq_range - some_const_freq = input_freq_rangePS. Don't really understand that business with 3rd mixer, why it's needed? And how the heck does Siglent achieve -120dB-ish noise floor when even RF switches there are rated for -40-60 dB coupling?Very thanks!
Why triac keeps getting damaged in this circuit? - Page 1
Forum section: electronics / beginners

author: mkaluza
author_rank: Contributor
timestamp: July 03, 2022, 03:45:57 pm
content: Hi!First - if my schematic makes no sense, let me explain what I wanted to achieve. I have dual switch connecting 330n and 1u caps to AC. Those power a led strip via a rectifier bridge (it has a parallel 100u cap and so the voltage is fairly constant, that's why I replaced it with a voltage source to keep the schematic clean). That works as intended - one switch is 'low', the other is 'high'. The issue is that when 'high' is on, adding 'low' to it makes little difference in the total light output when compared to going from 'low' to 'high'. I wanted to change that by adding a triac that would act as a kind of AND gate - if both high and low are on, enable one extra cap. So now, if 'low' current would be I, then 'high" would be 3I and 'both' would give 7I (vs 4I before), which gives a noticeable difference.But it doesn't workTriac seems to get damaged in some way after few switches.Any suggestions?The only difference is that I use a different triac model in reality - I have BT131-600, which is also 'small'.Thanks!Martin

author: harerod
author_rank: Frequent Contributor
timestamp: July 03, 2022, 04:59:10 pm
content: BT131-600 - maximum permissible gate voltage 5V. Maybe this was exceeded at some point?Edit 2207040954:This old datasheet shows some maximum ratings (including gate parameters). Without further comment on the circuit - I am sure that some absolute maximum ratings are being exceeded:https://pdf1.alldatasheet.com/datasheet-pdf/view/16744/PHILIPS/BT131-600.html

author: Zero999
author_rank: Super Contributor
timestamp: July 03, 2022, 07:15:20 pm
content: The gate looks like a pair of diodes back-to-back, so there isn't a maximum gate voltage rating. The gate voltage is dependant on the gate current and junction temperature.https://www.ween-semi.com/sites/default/files/2018-10/bt131-600.pdfMy guess is the current surge through the capacitor is what's killing it.

author: mkaluza
author_rank: Contributor
timestamp: July 04, 2022, 03:11:21 pm
content: You're probably right - the simulation didn't take into account switching it on at random moments during the AC cycle... Added some small resistors (18 Ohm) and it lived a little longer, so after finally doing some calculations I figured I need bigger ones and probably a small redesign of the circuit so that gate cap is smaller.Is there any other way to counter the surges? Inductors, but those would introduce their own set of problems probably...Thanks for pointing this out!Martin

author: Zero999
author_rank: Super Contributor
timestamp: July 04, 2022, 03:54:48 pm
content: An inductor would have to be huge to make and difference and its impedance would counteract the capacitance. Only switching the TRIAC on shortly after the zero crossing point would reduce the surges.
Why two inputs? - Page 1
Forum section: electronics / beginners

author: viperidae
author_rank: Frequent Contributor
timestamp: February 07, 2019, 07:26:52 am
content: Looking at the datasheet for this bus interface IC, there are two inputs. They're both identical. Why would they do that?https://www.renesas.com/us/en/doc/products/assp/rej03f0095_ha12240fp.pdfS1 and S2 are both TX inputs.

author: vealmike
author_rank: Regular Contributor
timestamp: February 07, 2019, 07:45:39 am
content: Quote from: viperidae on February 07, 2019, 07:26:52 amPhilosophical rather than electrical your question is. The application must you consider. To see a wood, one must first ignore the trees. Change must come from within, but charge a product of time and current it is.Yeerrs.

author: viperidae
author_rank: Frequent Contributor
timestamp: February 07, 2019, 08:01:51 am
content: The application for the chip is a physical driver for IEBus, to connect to a NEC/Renesas MCU with a built in IEBus controller.Those built in controllers only have one TX output.

author: Ice-Tea
author_rank: Super Contributor
timestamp: February 07, 2019, 08:07:04 am
content: S1 and S2 are followed by an OR gate. So it allows some sort of multiplexing or logic gating. If you don't need it, tie it to ground.

author: bsudbrink
author_rank: Frequent Contributor
timestamp: February 07, 2019, 05:20:11 pm
content: Quote from: vealmike on February 07, 2019, 07:45:39 amStock in Disney/Lucas Arts he owns.

author: David Hess
author_rank: Super Contributor
timestamp: February 07, 2019, 07:07:33 pm
content: The second input allows the output to be set into a known state without relying on the data source. This can be especially important when the data source uses a different power domain and may generate spurious data during power up or power down. The ancient 1488 RS-232 line driver and many other interface ICs have dual inputs also for the same reason.

author: viperidae
author_rank: Frequent Contributor
timestamp: February 07, 2019, 09:36:41 pm
content: Quote from: Ice-Tea on February 07, 2019, 08:07:04 amAccording to the equivalent circuit, these are "active low" inputs, driving the base of a PNP transistor. I think I'll need to tie them together or tie one high.

author: Ice-Tea
author_rank: Super Contributor
timestamp: February 08, 2019, 06:43:24 am
content: Quote from: viperidae on February 07, 2019, 09:36:41 pmThe DS clearly states that logic high is 2.1V or above.
Why voltage  multipliers  are not actual "multipliers"? - Page 1
Forum section: electronics / beginners

author: 001
author_rank: Super Contributor
timestamp: November 05, 2018, 03:13:39 pm
content: Why voltage multipliers are not actual "multipliers"?I cant` get 30V DC from single 16V AC transformer

author: macboy
author_rank: Super Contributor
timestamp: November 05, 2018, 04:02:52 pm
content: A 16 VAC transformer may have a no-load voltage of 18 to 20 VAC (which drops to 16 VAC at full load). At 20 VAC, the peak voltage will be about 28 V, so when rectified, about 27 VDC. So if you set up a x 2 multiplier you might get 40 to 50 V after accounting for diode losses, and depending on the transformer. That is only withnoload. Any load will cause the voltage to sag. You need big capacitors in the multiplier to reduce this voltage drop.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 05, 2018, 04:20:15 pm
content: And significantly worse from a split-bobbin or "impedance protected" type transformer. Multiplier requires very low impedance from the transformer.Tim
Why would I use a "Resistive Touchscreen Controller" - Page 1
Forum section: electronics / beginners

author: michaelym
author_rank: Regular Contributor
timestamp: December 18, 2013, 07:07:30 am
content: Why can't I just use the ADC in my MCU?

author: tesla500
author_rank: Regular Contributor
timestamp: December 18, 2013, 07:42:46 am
content: It provides some nice features like current limiting drivers, for the case where you touch both the top left and bottom right (for example) of the screen and the touchscreen effectively becomes a short circuit. Also, touchscreens are often used in systems with high end microprocessors that don't have any internal ADCs.

author: con-f-use
author_rank: Unknown
timestamp: December 18, 2013, 09:31:24 am
content: And some are protected against static...

author: lapm
author_rank: Frequent Contributor
timestamp: December 18, 2013, 11:55:23 am
content: My limited experience on capasitive and resistive touchpads is that resistive ones are more accurate. but this just mo opinion, have not done any testing other then couple mobile phones...As others have pointed out, dedicated interface chip on these usually provides some handy features that are good to have.Want to be super cheap, nothing is preventing you to use MCU's AD converter, but then you can expect some troubles to show up. Things you might not know that touchpad can do or behave like that...
Why would one need different Thermoelement connector for different type   - Page 1
Forum section: electronics / beginners

author: RoadRunner
author_rank: Frequent Contributor
timestamp: June 30, 2022, 04:26:29 pm
content: I have recently bought a rusty broken, Digistant Temperature sensor calibrator off ebay, it came with many different connectors as per image.Why would one need different connector?

author: wizard69
author_rank: Super Contributor
timestamp: July 01, 2022, 05:30:58 pm
content: Thermocouples are created any time dissimilar metals come into contact. Also there is the concept of reference junction compensation.The NIST as some create materials related to temperature transducers.

author: elekorsi
author_rank: Regular Contributor
timestamp: July 01, 2022, 08:39:48 pm
content: as written above, thermocouple junction occurs when two different metals are joined. For that reason there are different connectors for different thermocople types, so that there are no additional TC joints. Also the connecting cables must be specified specifically for the TC type that is used...forget regular copper cables. Same goes for any terminals in the cabinet...
Why would you put inductive resistors in series with a small electric motor ?  - Page 1
Forum section: electronics / beginners

author: tigrou
author_rank: Regular Contributor
timestamp: September 02, 2023, 06:29:38 pm
content: This schematic is from the grinder of a coffee machine.I am wondering why there are resistors in series with the motor. What is the purpose ?AFAIK It's quite common to add inductors and capacitors to form a LC circuit and do some filtering (to prevent interferences to go back to the electronic part) but there is no capacitor here.

author: tigrou
author_rank: Regular Contributor
timestamp: September 02, 2023, 06:46:43 pm
content: Quote from: temperance on September 02, 2023, 06:43:59 pmI wrote resistor because it's written "Ind. resistor" above it and resistors are usually shown as a rectangle.But indeed there is no "ohms", it's only talking about Henrys and Amps.

author: coppercone2
author_rank: Super Contributor
timestamp: September 02, 2023, 06:46:58 pm
content: hi, can you put the resistor value of the proposed resistorbecause if it dont have resistance then its a inductor

author: temperance
author_rank: Super Contributor
timestamp: September 02, 2023, 06:55:14 pm
content: I wanted to expand my comment but instead deleted my post.There are many ways to filter brushed motors. Sometimes the capacitors are integrated into the motor itself because they need to be as close as possible to the brushes. A combination of some DC resistance within an inductor is not so strange and very of done with low power brushed DC motors like those in shavers, soup mixers,...to provide some damping.

author: TimFox
author_rank: Super Contributor
timestamp: September 02, 2023, 07:27:20 pm
content: The label "resistor" must be a mistake.15 uH at 2 A is a reasonable value for an inductor, and would help filter brush-commutation noise to reduce radiated and conducted EMI through the power feed.If it were a mistake for 15\$\Omega\$, that would be a physically large resistor that would be rated for > 60 W.In Europe, the rectangle is often used for resistor, but in North America, it is usually symbolized as a zig-zag, which is a better metaphor for a resistance.In both areas, an inductor is usually symbolized as a set of loops.
. - Page 1
Forum section: electronics / beginners

author: Unknown
author_rank: Unknown
timestamp: August 04, 2020, 05:44:21 pm
content: .

author: tooki
author_rank: Super Contributor
timestamp: August 04, 2020, 05:55:39 pm
content: Probably to prevent ghosting with those specific keys.

author: wizard69
author_rank: Super Contributor
timestamp: August 04, 2020, 07:26:03 pm
content: Quote from: icpcb on August 04, 2020, 05:58:35 pmI have no idea what ghosting is but if they are using more keys than required there is something special being done with one or more keys. Maybe one needs to generate an interrupt. Even there, 14 is an odd increase in line usage.

author: tooki
author_rank: Super Contributor
timestamp: August 04, 2020, 09:28:29 pm
content: Quote from: wizard69 on August 04, 2020, 07:26:03 pmhttps://deskthority.net/wiki/Rollover,_blocking_and_ghosting
Why wounldn't big "modern" stereo amp have main's Earthing ? - Page 1
Forum section: electronics / beginners

author: lordvader88
author_rank: Frequent Contributor
timestamp: June 26, 2019, 12:59:44 pm
content: I'm just wondering, it has a big linear trans, bolted to the case, made + 2001 by Kenwood, and I'm sure meets all safety requirements to be sold here, yet has no mains earthing ?

author: ebastler
author_rank: Super Contributor
timestamp: June 26, 2019, 01:03:55 pm
content: It must be double-insulated, or "class II", then. You should find the "two concentric squares" symbol on its type label:https://en.wikipedia.org/wiki/Appliance_classes#Class_II

author: madires
author_rank: Super Contributor
timestamp: June 26, 2019, 01:41:15 pm
content: Some amps with 2-prong plugs have a ground terminal for optional earthing. Since ground loops are a common problem with audio setups an enforced ground via the amp's mains plug might be not the best idea.

author: mariush
author_rank: Super Contributor
timestamp: June 26, 2019, 01:47:52 pm
content: There are ways to make transformers with enough insulation between primary and secondary that earthing is not required.For example, there are R core transformers where each winding is in a separate spool, on opposite sides of the core material :http://jamestransformer.com/en/transformer/R_core_transformer.htmlOr you can use double insulated wire, or plastic frames with plastic wall between the two windings...

author: floobydust
author_rank: Super Contributor
timestamp: June 27, 2019, 02:28:36 am
content: Historically consumer audio gear is not grounded, instead double-isolated because of the ground-loops that occur.Power amp, tape player, turntable, TV, DVD player etc. would be connected together and lots of mains hum results.You would have to use balanced audio connections instead of single-ended RCA jacks, so added cost there they avoid.Really old audio gear from the 1950's or so, there was no earth ground in North American outlets. So they manufacturers used the "death cap" to stop RF and noise from being a problem.
Wi-fi goes down - Page 1
Forum section: electronics / beginners

author: Remark
author_rank: Contributor
timestamp: July 24, 2022, 07:26:06 pm
content: Hello everyone!I have been learning to work with embedded linux boards for a while. And I ran into an interesting problem right now. For example if I try to connect to my board using ssh root@, my wireless connection keeps disconnecting. In this case, disconnecting the embedded device from the router with a LAN cable will restore the connection. I'm trying to understand why this happens. Is there a long-term solution to this problem? Maybe someone have faced a similar issue? I'm running Ubuntu 22.04 LTS.Thanks!Remark.

author: mag_therm
author_rank: Frequent Contributor
timestamp: July 24, 2022, 09:20:50 pm
content: Checks:Login to router as admin and look at "Block Services" or similar.(Blocking ssh to wireless might be seen as prudent in some cases)If the wireless client is accessing via any router gateway, then that router needs to have port forwarding, port 22 to <yourserver> port 22But that setting is not needed for another LAN user, like your cable connectionThe following are general tests although less likely to show the cause if you can already login via a LAN cableOn the wireless client run: ( fedora, assume ub is similar or you can find equivalent)nmap -Pn <yourserver> ;See that port 22 is opentraceroute <yourserver> ; to see if any gateways are in hops from your wirelessThen do the reverse back to wireless client from embedded linuxOn the embedded linux, look at the firewall settings, that ssh port 22 is showing.Try to login from wireless client using ssh <user>@<yourserver> (instead of as root)Actually direct root login is usually disabled from any IP. That is done in sshd-config where it is worth reading all permissives.Because, you login as user than su to root only when needed.To see ssh login attempts on embedded linux run as root:cat /var/log/secure* |grep ssh | more ; That might show the login attempts from wireless that you can then compare.( if there are too many logins to check, you can either delete or rename the secure*, then do test logins to start a new file)Edit, Adding another likely one !The RSA keys may be referenced to presently different ip. Can happen on server or client or both/home/<user>/.sshmake a dir old. Then move the present known_hosts into old.After that a new known_hosts will be made and you will confirm to add a new key for each client next time they log in
Wi-Fi router power output - Page 1
Forum section: electronics / beginners

author: Jane
author_rank: Frequent Contributor
timestamp: December 09, 2017, 09:24:35 pm
content: What methods can be used for measuring the power output of a Wi-Fi router?Is it also possible to measure the waveform of that wifi router( antenna power signals)?Thanks for suggestions

author: danadak
author_rank: Super Contributor
timestamp: December 09, 2017, 10:16:43 pm
content: QuoteA spectrum or network analyzer. Or a calibrated antenna, like a dipole or monopole.QuoteYes, there are scopes that can actually see the waveform. Sampling scopes would permitthat. Its complex modulation, DSSS, so you could look at the modulating signal or the complexcarrier result.https://en.wikipedia.org/wiki/Direct-sequence_spread_spectrumRegards, Dana.

author: Dave
author_rank: Super Contributor
timestamp: December 09, 2017, 10:45:22 pm
content: Something likethiswould also work very well.

author: Jane
author_rank: Frequent Contributor
timestamp: December 11, 2017, 09:06:23 am
content: @danadak: You sayQuotedo you mean to connect an antenna to a spectrum analyzer? Or to use an antenna with a different device such as a scope?And what kind of scope to use?Thanks

author: danadak
author_rank: Super Contributor
timestamp: December 11, 2017, 11:18:13 am
content: This might help -https://www.semtech.com/images/promo/Semtech_ACS_Rad_Pwr_Field_Strength.pdfRegards, Dana.

author: Raj
author_rank: Frequent Contributor
timestamp: December 12, 2017, 04:05:09 pm
content: There are some diy network analyzer based on esp chips, on instructables

author: Azu
author_rank: Newbie
timestamp: December 19, 2017, 01:21:05 am
content: Surprisingly, the Wifi Analyzer app on the Play Store does a pretty pretty good job at measuring your signal vs competing signal in your area best of all it's free! I assume if you're a Apple user they should have something equivalent.
Wich data type for display buffer - Page 1
Forum section: electronics / beginners

author: PeterFW
author_rank: Frequent Contributor
timestamp: February 06, 2016, 09:13:06 am
content: Hello everybody!On my bench sits a 16x25 pixel LED display i build, after i veryfied that everything works it is now time to write a library and write some proper code.Each pixel has 8 bit resolution, at the moment i am using a 2D array to store the display data. That makes for nice and easy readable code.While looking up another library i saw it use a normal array as a display buffer.Is a reason behind that?Should i switch to a simple array or can i continue to use a 2D array?Greetings,Peter

author: dom0
author_rank: Super Contributor
timestamp: February 06, 2016, 09:39:39 am
content: Multi-dimensional arrays are folded into a one-dimensional array in virtually every programming language (except maybe shells and probably mathematics software), so there really is no advantage in writingframebuf[WIDTH * y + x]over e.g.framebuf, the latter will be converted by something like the first by the compiler.
wich hot air station to buy - Page 1
Forum section: electronics / beginners

author: Passarotrovao74
author_rank: Newbie
timestamp: January 10, 2025, 06:55:35 pm
content: HelloI ´m a absolut beginner and i own a VELLEMAN VTSSC50N soldering station now i want to buy a hot air station for soldering and desoldering smaller components. I dont want to spend much so it can sit on a conner on my place, but i want to buy once.Any ideas about a decent air station less that 150 euros.Thanks.

author: Old Printer
author_rank: Frequent Contributor
timestamp: January 11, 2025, 03:55:50 am
content: I bought the Quick 957DW+ from Tequipment for $105 US dollars and I am quite happy with it. Rotary analog heat and air controls with digital temperature readout. Air pump is in the control unit and heat element in the hand piece. Next model up was three times the price and more than I cared to invest in a tool I only use occasionally.

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: January 11, 2025, 09:01:45 am
content: Check eBay, there are lots of “858D” hot air stations for around €35~€40Make sure it includes a selection of nozzles, as not all do.I have had one for a few years and they are good enough for hobby use, both soldering and removing SMD parts.SJ

author: watchmaker
author_rank: Unknown
timestamp: January 12, 2025, 01:34:14 pm
content: I have been happy with the Yihua. Takes up little space (kept off bench until needed), heats nicely and is great for many things.https://www.aliexpress.us/item/3256806674398972.html

author: sairfan1
author_rank: Frequent Contributor
timestamp: January 12, 2025, 04:43:00 pm
content: Years back i bought Yihua Hotair + Soldering station from aliexpress Yihua official store, it works perfect, since then I always buy from Yihua any accessory i need for soldering requirements.They are price quite reasonable, quality is good, they have huge variety for solering related needs

author: ahsrabrifat
author_rank: Regular Contributor
timestamp: January 13, 2025, 05:57:01 pm
content: You can see Sparkfun's hot air rework Station - 8508D. Sparkfun sells authentic and tested products so I find them more dependable than ebay suppliers.
Wide supply voltage range input voltage tolerance - Page 1
Forum section: electronics / beginners

author: czk9527
author_rank: Contributor
timestamp: November 28, 2016, 05:28:09 am
content: Hi guys, just a quick question. If say my MCU is capable of running under wide supply voltage range (1.6V - 3.6V). If I power it with 2V and interface it to an ADC which is powered by 3.3V. Will the MCU blow up? Cheers.

author: MK14
author_rank: Super Contributor
timestamp: November 28, 2016, 05:51:19 am
content: You need to check the datasheet for the specific MCU you are using.Often/usually, the inputs are limited to the supply voltage rails. So if you run it at 2 Volts, the inputs must not exceed 2 volts.But some MCU's have inputs, which can tolerate higher voltages, such as 5V or 3.3V. Again, best to refer to the datasheet.If they do, be careful, because it may only apply tosomeof its inputs, and may have other requirements as well.The problem is that many inputs have ESD/static protection built in to them, which means that there are diodes, connecting it (protecting it) to the ground and Vcc pins. They are connected up in such a way, that if more than about half a volt or so difference (below ground, or above Vcc), between the supply pins and the input(s), significant/huge currents can flow.There is a good EEVblog video about it.

author: Rerouter
author_rank: Super Contributor
timestamp: November 28, 2016, 10:01:58 am
content: Perhaps tell us the interface your adc will use, if it's i2c, you can have your liftups to 2v and it will work just fine, if it's an spi one then add a resistor divider on the inputs and direct connect the outputsMost devices will tell you there accepted high and low input thresholds, and most 3.3v devices I have seen use 1.8v to register a high. Which for a modern micro should be ok.
Wider trace is a lower induction trace? - Page 1
Forum section: electronics / beginners

author: king.oslo
author_rank: Frequent Contributor
timestamp: June 17, 2013, 01:59:16 pm
content: Hello there,Longer traces increase inductance, as become evident from the series inductance formula.And, by the parallel equation, it looks like wider traces would decrease inductance.Can you confirm this?Thanks

author: jpb
author_rank: Super Contributor
timestamp: June 17, 2013, 02:30:20 pm
content: Yes, as a general principle.Though remember that wider traces will also increase capacitance to the ground plane.I used to work with microwave devices and it was very important to minimise source inductance (in FETs) so generally tape rather than wire was usedor else several wires in parallel to connect the source pad to the microstrip.

author: king.oslo
author_rank: Frequent Contributor
timestamp: June 17, 2013, 04:35:49 pm
content: Thank youM

author: onlooker
author_rank: Frequent Contributor
timestamp: June 18, 2013, 12:40:37 pm
content: The parallel formula is not valid here. It applies only to Ls away from each other. When you consider wider trace as a parallel of several narrow traces, mutual inductance comes into play. To a good approximation, the inductance can be considered as independent of width as far as I remember ( or google it)

author: jpb
author_rank: Super Contributor
timestamp: June 18, 2013, 12:49:07 pm
content: Quote from: onlooker on June 18, 2013, 12:40:37 pmYou are right that the parallel formula doesn't hold - I didn't want to complicate matters by raising that - but inductance does decrease with width.A better model is microstrip line, assuming that the traces are above a ground plane.The following web-site gives a formula and calculator (though, as with all these equations, assumptions are made in deriving them such as there is no other metal around other than the ground plane and the strip line itself).http://www.daycounter.com/Calculators/Microstrip-Inductor-Calculator.phtmlThe formula is derived by taking the ground plane to act as a mirror essentially so there is another stripline an equal distance below it. You then need to do a contour integral with the assumption that the microstrip has no thickness and uniform current flow. (Using the integral form of Maxwell's equations.) It's a long time since I was into this sort of thing but I seem to remember it is quite fun.
Wiegand with Logic Analyzer or oscilloscope? - Page 1
Forum section: electronics / beginners

author: nardev
author_rank: Unknown
timestamp: January 27, 2020, 02:02:55 am
content: Other than using a some MCU and existing libraries, i wish to get decent preview of wiegand data transferred from a reader.I have on my disposal some crappy Logic Analyzer which i can use with Saleae software and Siglent SDS 1104X which only has decoder for several protocols, I2C, UART etc.The nature of wiegand is actually to keep both lines at high and pull down D0 for 9 and D1 if 1 is to be sent.Is there any handy way to visualize that, i can decode it by hand, bu i wish to get visualization nicely.Any suggestion?

author: tautech
author_rank: Super Contributor
timestamp: January 27, 2020, 03:24:04 am
content: Quote from: nardev on January 27, 2020, 02:02:55 amSDS1104X-E has a CAN decode that seems similar. Maybe you can you can try that.https://en.wikipedia.org/wiki/Wiegand_interfacehttps://en.wikipedia.org/wiki/CAN_busThe instruction for Siglents STB3 might be useful in helping to get decode settings correct.https://www.siglenteu.com/wp-content/uploads/dlm_uploads/2018/07/STB3_User-Manual_UM60109_E01B.pdf

author: nardev
author_rank: Unknown
timestamp: January 27, 2020, 04:18:07 am
content: Tried with CAN, didn't get what i expected. (can post photos later).I'm just thinking is there some kind of a "math" and signal inversion that i can do and put D0 and D1 on top of each other and get visual like that?

author: digsys
author_rank: Unknown
timestamp: January 27, 2020, 04:30:52 am
content: I do a heck of a lot of Wiegand, and really, a 2ch DSO is pretty much vital. I have decoded heaps of "encrypted" data streams that way.You can also verify - line capacitance, slew / timimg, levels at the same time. Is it a common device?

author: tautech
author_rank: Super Contributor
timestamp: January 27, 2020, 04:36:37 am
content: Quote from: nardev on January 27, 2020, 04:18:07 amChannel menu>P2> Invert.

author: Seeed
author_rank: Newbie
timestamp: March 03, 2021, 02:37:13 pm
content: ...take a look at sigrochttps://sigrok.org/

author: Doctorandus_P
author_rank: Super Contributor
timestamp: March 03, 2021, 02:39:29 pm
content: Throw away that crappy Saleeaeaeaea software and use your cheap LA with:https://sigrok.org/wiki/Protocol_decodersSigrok has Wiegand listed as a supported protocol.
Wien Bridge Oscillator - Page 1
Forum section: electronics / beginners

author: vargoal
author_rank: Regular Contributor
timestamp: February 08, 2015, 05:34:53 am
content: So I am trying to make a sine wave generator to replace my awful signal generator/power supply I got from school for free using a Wien Bridge Oscillator circuit. Anyway I built it up but it's not working and I was wondering if my op-amp has to be rail to rail? If anyone knows that would be great, also if you know of any tricks for a beginner building this circuit that would also be appreciated. For those of you who haven't heard of this here is a linkhttp://www.electronics-tutorials.ws/oscillator/wien_bridge.html

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 08, 2015, 06:15:21 am
content: You need bipolar supplies.Tim

author: AG6QR
author_rank: Frequent Contributor
timestamp: February 08, 2015, 06:20:31 am
content: Your op amp does not have to be rail to rail.In the resistive feedback loop to the negative terminal, the value of the gain is critical. If the gain is too low, the oscillations will dampen to zero. If it's too high, the oscillations will increase in amplitude until clipping and distortion. Also notice that, in order to start oscillating initially, the gain has to be high, so that some random fluctuation will be amplified until it results in full scale oscillation. When oscillation is established, the gain needs to be reduced in order to keep the amplitude steady and low in distortion. To make a good sine wave oscillator with low distortion and a steady amplitude, some sort of active adjustment to the gain in that resistor network is usually used. The classic approach is to use a light bulb, which increases its resistance as more current goes through it. That's what Hewlett Packard did for their classic Wien Bridge audio oscillator. There are other possible approaches, using PTC thermistors, diodes, and/or transistors.If you're not seeing any oscillation, then I'd guess your resistor values in the negative feedback side might be resulting in insufficient gain. Of course, the feedback on the positive side also has to be correct...Here are a few info sources:https://www.calvin.edu/~pribeiro/courses/engr332/Handouts/oscillators.pdfhttp://www.zen22142.zen.co.uk/Design/wien_osc/Wien-Bridge%20Oscillator.htm

author: sdg
author_rank: Regular Contributor
timestamp: February 08, 2015, 08:35:29 am
content: You might want to take a look at an application note from Linear. Can't find the number, but the title is "Fidelity testing for A/D converters" by Jim Willliams & Guy Hoover. It has a very good description of a low-distortion Wien bridge sine generator with AGC and what is needed to make it work.

author: dannyf
author_rank: Super Contributor
timestamp: February 08, 2015, 12:35:35 pm
content: No need for r2r opamps or bipolar power rails.

author: dannyf
author_rank: Super Contributor
timestamp: February 08, 2015, 12:39:22 pm
content: If you post the schematic here it would be easier for others to help you.Agc is helpful but not necessary. My prefered agc is led plus photoresistors.
WIFI Antenna boost for my nexus 7 - Page 1
Forum section: electronics / beginners

author: royderuyter
author_rank: Newbie
timestamp: January 13, 2013, 01:08:25 pm
content: Hi need some help.I want to improve the range of my WiFi Antenna on my android Nexus 7. I wan to hook it up with a 16dBi flat panel WiFi 2.4 GHz antenna. I want to solder it direct to the Nexus 7 using a RP-SMA pigtail bulkhead connector. The idea is to improve the range for a helicopter (AR DRONE) which uses WiFi.This has already been done by some guys in the USA using this exact config. (youtube has lots of stuff on the topic. But no one seems able to answer my questionsWhat I would like to now if how to solder the leads to the Nexus and if there is any polarity issues. Can anyone help?? I have asked thanks Roy

author: Lord of nothing
author_rank: Super Contributor
timestamp: September 05, 2015, 06:36:19 pm
content: Why not an Wifi Repeater?

author: andybarrett1
author_rank: Regular Contributor
timestamp: September 05, 2015, 08:29:13 pm
content: Quote from: Lord of nothing on September 05, 2015, 06:36:19 pmA What

author: Lord of nothing
author_rank: Super Contributor
timestamp: September 05, 2015, 08:31:04 pm
content: http://www.linksys.com/at/range-extender/c/wlan-range-extender/

author: Hideki
author_rank: Frequent Contributor
timestamp: September 05, 2015, 09:31:25 pm
content: Quote from: Lord of nothing on September 05, 2015, 06:36:19 pmBecause people usually fly drones outside and don't want to set up a range extender out in the bush on a giant extension cord?(Ok, it could possibly be battery powered.)Anyway... it's not what royderuyter was asking for. Of course there is a polarity issue. You solder the shield to ground and the center connector to the antenna signal. Isn't it clear enough from this video?Are you asking how to solder in general? How to cut and strip the coax? Which pad is ground and which is the antenna, or what?
WiFi antennas all grounded to chassis? - Page 1
Forum section: electronics / beginners

author: cds333
author_rank: Contributor
timestamp: May 11, 2022, 02:18:21 am
content: It is SOP to build a wifi transceiver with all the antennas mounted directly to the chassis?Specifically I am referring to a dual band AX WiFi access point with 8 internal antennas.In such a configuration, wouldn't any signal sent over one antenna also be free to leak out over the other antennas as well?For that matter wouldn't the aluminum chassis act as one big poorly tuned antenna?What confines a signal to it's one intended antenna only?Thanks!

author: Doctorandus_P
author_rank: Super Contributor
timestamp: May 11, 2022, 02:42:48 am
content: I think the aluminium is more of a local "ground".2.99e8/2.4e9 = 12.5 cm wave length, so the aluminiumum is multiple wavelengths.To measure a voltage, you always need a reference, that is why your DMM has two probes. For radio waves the "earth" is used as a ground reference. (except for bipolar antenna's)I'm guessing you big chunk of aluminimum is serving as an "earth" reference here. Maybe that's one of the main reasons to put such a big chunk of metal in that thing.But I'm a complete amateur in this regard and don't know much about this radio stuff.

author: cds333
author_rank: Contributor
timestamp: May 13, 2022, 11:04:38 pm
content: Most other APs I have disassembled have no such ground. This is the first that utilizes such a large piece of metal as a chassis.

author: Whales
author_rank: Super Contributor
timestamp: May 14, 2022, 12:49:10 am
content: Every antenna is fed by two wires and is made of two bits of conductor, never one (even if it appears that way). In this case they're unbalanced signals going over small coax cables (most of signal on centre wire, as little as possible on outer/sheath/shield wire).The centre wire connects to the bent metal antennas. These do not connect to the case, or if they do then it's through a tuned length & shaped section of the bent metal (which won't be a short circuit at the operating frequency of the antenna, so to make things easier you can kind of pretend it's not there).The outer/sheath/shield wire will be the bit bonded to the grounded chassis via metal tape.
Wifi antennas, which is which ? - Page 1
Forum section: electronics / beginners

author: BravoV
author_rank: Super Contributor
timestamp: September 25, 2018, 07:05:10 am
content: At dual bands wifi, say like wifi router that has multiple antennas.Do they all serve both bands 2.4 and 5 GHz ? Or separated ?If its separated, how to determine which is which ?Random images grabbed from the net ...

author: Karlo_Moharic
author_rank: Regular Contributor
timestamp: September 25, 2018, 03:27:38 pm
content: Cheap sdr (one that goes up to 5 Ghz) or cheap spectrum analyzer and small antenna

author: bob225
author_rank: Frequent Contributor
timestamp: September 25, 2018, 03:48:56 pm
content: There all the same either dual band or tuned on board, the method of operation depends how its setup (MIMO)

author: PA0PBZ
author_rank: Super Contributor
timestamp: September 25, 2018, 06:14:42 pm
content: I think it differs per manufacturer and model, some are dual band, some are just fake and have the antenna's for one or both bands inside on the pcb, and others… well you get the idea. Are you just curious or is there any practical use for the knowledge?

author: bob225
author_rank: Frequent Contributor
timestamp: September 25, 2018, 06:25:11 pm
content: WIFI its a entire subject on its own, and a big can of worms

author: BravoV
author_rank: Super Contributor
timestamp: September 27, 2018, 05:46:06 am
content: Thanks all for the replies, I guess there is no simple and straight forward answer as I expected.Quote from: PA0PBZ on September 25, 2018, 06:14:42 pmI'm going to buy a new dual band wifi router at my parent's house, due to the locations and the building structures, and also wiring limitation, the 5Ghz band is lacking at few areas and just want them to use higher bandwidth than 2.4Ghz.I've been looking few routers that have detachable antennas, so I wasthinkingguessing maybe "IF" both bands are separated, I'm going to buy better antenna for the 5GHz band to improve the signal in the house.Yes, I'm aware of other solutions like using separate repeater and such, but just want to explore this possibility of using better antenna.