hybridfree/eevblog-posts huggingface dataset:
How do you run a IN-12B Nixie tube - Page 1
Forum section: electronics / beginners

author: Tom10000
author_rank: Contributor
timestamp: March 23, 2018, 12:47:48 am
content: Hello,I recently bought a Soviet IN-12B nixie tube and I am wondering how to run ithere is a picture:

author: Canis Dirus Leidy
author_rank: Regular Contributor
timestamp: March 23, 2018, 05:21:00 pm
content: Do you read Russian?OK, more seriously. IN-12B does not fundamentally differ from other Nixie tubes. Indicator's anode is connected to high voltage source through current-limiting resistor, cathodes are connected to decoder with high-voltage capable output (such as K155ID1 aka 74141) or transistor switches:http://radiokot.ru/lab/controller/28/07.pnghttp://jacoburge.co.uk/nixie-clock/P.S. Some numbers fromIN-12 datasheet:Anode voltage (DC): at least 200V, 250V recommended."Digit" cathodes working current (DC): 2.5-3.5 mA"Comma" (digital dot) cathode working current (DC): 0.3-0.5mA

author: james_s
author_rank: Super Contributor
timestamp: March 25, 2018, 06:23:13 am
content: It's pretty easy, you'll need a power supply delivering at least 170V or so, an anode resistor calculated (using Ohms law and the forward voltage of the tube subtracted from the supply voltage) to deliver around 2mA. For the decimal point you need an additional resistor on that cathode to reduce the current further if you use that element.
How do you screw stock microscope mount to the table?  - Page 1
Forum section: electronics / beginners

author: u666sa
author_rank: Frequent Contributor
timestamp: September 01, 2023, 02:55:21 pm
content: Me honestly have to clue how he did it. But I have to figure it out. Attached pics. Otherwise I'd have to pay $110 for something like this custom made:The mount I have is attached in 3 photos at the bottom of this thread.

author: u666sa
author_rank: Frequent Contributor
timestamp: September 01, 2023, 04:06:43 pm
content: Quote from: wasedadoc on September 01, 2023, 04:05:40 pmThe 3 attached photos.

author: wasedadoc
author_rank: Super Contributor
timestamp: September 01, 2023, 04:11:17 pm
content: Looks like you need to make a hole in the tabletop for the threaded part in 2023-09-01_17-51_1.png to just fit through. Are there any more pieces you have not shown?

author: u666sa
author_rank: Frequent Contributor
timestamp: September 01, 2023, 04:38:24 pm
content: Quote from: wasedadoc on September 01, 2023, 04:11:17 pmYou see, how he screw the stock mount that microscope comes with into table?This is the stock mountI want to figure out how to screw the pole from the stock mount into table. Making the hole in the table is no problem. The problem is that table is thick.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: September 01, 2023, 05:04:40 pm
content: Quote from: u666sa on September 01, 2023, 04:38:24 pmUse a longer bolt then.As an alternative, you can also use the stock table, rotate it a bit and then put something heavy like a power supply on top of it. This is at least an easy temporary solution.

author: wasedadoc
author_rank: Super Contributor
timestamp: September 01, 2023, 05:24:01 pm
content: Now that I see the large plate, that changes things. Does the bolt with with head for an Allen key unscrew and come out of the black cylinder?

author: u666sa
author_rank: Frequent Contributor
timestamp: September 02, 2023, 12:41:29 pm
content: Yea, I now realize that it is a bolt after all. So I'm getting a longer bolt and two flat wide heavy washers.
How do you search Digikey etc for  DC leakage current sensors? - Page 1
Forum section: electronics / beginners

author: Faringdon
author_rank: Super Contributor
timestamp: September 26, 2022, 10:03:36 pm
content: Hi,The FG-R05-3A is a current sensor which detects between -50mA and +50mA of DC leakage current in the mains supply (eg to an EV chargepoint).FG-R05-3Ahttps://www.mouser.co.uk/datasheet/2/212/1/KEM_SE0217_FG-1894121.pdfHow do you actually find other similar things on mouser or digikey etc?....neither have any way for you to depict these types of (DC leakage) current sensors.....they just come under "Board level current sensors"

author: geggi1
author_rank: Frequent Contributor
timestamp: September 27, 2022, 05:07:32 am
content: Search hall current sensor.Here is what i found on google.https://www.google.com/search?q=hall+current+sensor&oq=hall+current+sensor&aqs=chrome..69i57j0i512l4j0i22i30l5.6360j0j4&sourceid=chrome&ie=UTF-8

author: Hawaka
author_rank: Regular Contributor
timestamp: September 27, 2022, 07:15:01 am
content: Try residual or leakage current sensor. LEM has quite a few models.Sometimes it's easier to search on the manufacturer website for such things, then check the price and availability on octoparts.

author: Terry Bites
author_rank: Super Contributor
timestamp: September 27, 2022, 02:32:04 pm
content: Have you used the internet before?
How do you use the solid resin flux? - Page 1
Forum section: electronics / beginners

author: kalel
author_rank: Frequent Contributor
timestamp: July 09, 2017, 06:04:11 am
content: I'm sure that a Flux pen might be easy to use, but how do you use Flux in packages like these (that's just the cheapest flux package available):They come in a solid form, no spill, as they call it, and if you burn it with a soldering iron, I guess you used it up already. Maybe it's not designed for soldering irons? Although they mention soldering irons and all kinds of other things in the title.Anyway, any experiences are welcome.

author: Brumby
author_rank: Unknown
timestamp: July 09, 2017, 06:17:42 am
content: This has been discussed before:https://www.eevblog.com/forum/chat/solid-rosin-flux-how-is-it-used/

author: kalel
author_rank: Frequent Contributor
timestamp: July 09, 2017, 06:53:00 am
content: Quote from: Brumby on July 09, 2017, 06:17:42 amThanks. Will check. Assuming it's answered there, feel free to ignore this post/thread.

author: Brumby
author_rank: Unknown
timestamp: July 09, 2017, 07:26:43 am
content: The first few posts give you some answers - which is why I posted the link.After that, there's more discussion on chemistry - and using Coke.
How does "smart" chargers for smartphones and tablets work - Page 1
Forum section: electronics / beginners

author: aiq25
author_rank: Regular Contributor
timestamp: June 14, 2015, 02:00:40 pm
content: Hi I was wondering if anyone provide some articles or sources where they explain how does the "smart" chargers for smartphones and tablets work. What I mean is I would like to understand what voltages the D+/D- lines on the USB have to be to get higher current output from the USB chargers.I was always under the impression that a universal USB charger for devices "detects" the voltage on the D+/D- lines to determine if higher currents (1A, 2A, etc...) should be outputted. And the voltages on the D+/D- lines are set on the device (phones, tablets) and not on the charger.

author: Towger
author_rank: Super Contributor
timestamp: June 14, 2015, 02:05:38 pm
content: AFAIK the data lines in the usb plug are shorted, so the device knows it can draw more current.

author: ablacon64
author_rank: Frequent Contributor
timestamp: June 14, 2015, 02:25:24 pm
content: I have an HP Slate 7 2800 tablet and lost the AC adapter. The new adapter (not original) only worked after I shorted D+ and D-.

author: sleemanj
author_rank: Super Contributor
timestamp: June 14, 2015, 03:26:43 pm
content: In brief:Androidy stuff, the charger shorts the d pins.Iphony stuff the charger provides a voltage on the d pins, the specifics of which determine the current capability.In anycase, it is the charger that has the pins short or whatever, the shorting is the charger saying what ITs capablity is, the device looks at it to know how uch it's charging circuit can draw. Remember a usb charger is nothing more than a 5v power supply, the actual charging profile is managed by the device.

author: Howardlong
author_rank: Super Contributor
timestamp: June 14, 2015, 04:18:41 pm
content: The Microchip USB3751 device will identify the various non-proprietary chargers for you (ie those in the USB spec). Take a look at Table 4-1 on page 14 of the datasheet herehttp://ww1.microchip.com/downloads/en/DeviceDoc/00001824A.pdfUSB battery charging is historically a complete mess due to glacial pace of standards bodies being out of sync with the pace of technology and market demands.Edit: I just noticed they have an app note herehttp://ww1.microchip.com/downloads/en/AppNotes/en567019.pdf

author: miguelvp
author_rank: Super Contributor
timestamp: June 14, 2015, 06:54:00 pm
content: You could get one of Franky's YZXstudio meter.https://www.eevblog.com/forum/buysellwanted/franky's-sales-thread/msg690194/#msg690194Not sure if it's the red one or the yellow one that has the feature to detect the voltages, I'm pretty sure is the red one, but the video review from Julian Ilett should explain more:BTW Franky if you are reading this, what's up with the "Androd"? you should get the designer/maker of the device fix that. Then again, it might already be fixed on the firmware update you already mentioned.
How does a double-layered Vacuum Fluorescent Display work? - Page 1
Forum section: electronics / beginners

author: GnatGoSplat
author_rank: Regular Contributor
timestamp: February 19, 2022, 03:11:17 am
content: Came across this random auction, I think it's a car stereo with built-in EQ. What caught my eye that it's got a "DOUBLE LAYERED / FLUORESCENT DISPLAY". Looks like it has a transparent VFD on top of another VFD.https://www.ebay.com/itm/133869488338Also found a Youtube vid.So that got me wondering, how did they pull this off? The phosphor segments are usually visible, how did they make them transparent? Were there any other devices that used a double layer VFD like this?I've seen see-through OLEDs before, but first time to see a VFD like that.

author: tooki
author_rank: Super Contributor
timestamp: February 19, 2022, 02:35:45 pm
content: Presumably it's simply some kind of transparent phosphor. They certainly seem to exist (see the images on p.216 ofthis journal article).Or maybe it's ordinary phosphor, but deposited as a pattern that is sorta see-through, kinda how we see through window screens?Either way, it'll certainly use ordinary indium tin oxide as the transparent conductors on the glass.P.S. I can't access all of them, but there are journal articles and patent filings about transparent phosphors, e.g.:https://patents.google.com/patent/US2980550https://opg.optica.org/josa/abstract.cfm?uri=josa-45-7-493https://ieeexplore.ieee.org/abstract/document/7267309https://opg.optica.org/josa/abstract.cfm?uri=josa-47-4-300https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6422321/
How does a Hall effect transducer  work? - Page 1
Forum section: electronics / beginners

author: J4e8a16n
author_rank: Regular Contributor
timestamp: August 17, 2015, 06:36:49 pm
content: Hi everybody,How do I set up this to read the current passing in a wire troughtout the device. I put a resistor?Do I ut a small voltage between the two post of the transducer?Thanks for your attentionJPD

author: KerryW
author_rank: Regular Contributor
timestamp: August 17, 2015, 09:20:45 pm
content: That's NOT a Hall effect sensor.. It is basically a transformer secondary. The wire you pass through the center hole forms the primary. It will only detect AC current, not DC.If that is what you want, connect a 50 Ohm resistor between the 2 pins and measure the AC voltage across the resistor.

author: J4e8a16n
author_rank: Regular Contributor
timestamp: August 17, 2015, 09:27:11 pm
content: Ok.JPD
How does a .jed file map to the device? - Page 1
Forum section: electronics / beginners

author: obiwanjacobi
author_rank: Super Contributor
timestamp: March 18, 2023, 02:23:56 pm
content: I am researching how (jedec) .jed files map to GAL chips (like the 16v8/22v10).I am playing with the idea of writing my own CUPL software - because I cannot stand WinCUPL any longer 😁I know that the ones and zeros in the .jed file correspond to fuses in the device. I just don't know what the order (or address I guess) is they are counted in...So any info how those fuse maps map to the actual device would be welcome.

author: BillyO
author_rank: Super Contributor
timestamp: March 18, 2023, 04:03:30 pm
content: Here is something that might get you going:https://k1.spdns.de/Develop/Projects/GalAsm/info/galer/jedecfile.html#:~:text=3%20JEDEC%20File%20JEDEC%20means,generated%20by%20the%20GAL%2DAssembler.
How does a multimeter measure voltage internally? - Page 1
Forum section: electronics / beginners

author: nightfire
author_rank: Frequent Contributor
timestamp: April 02, 2022, 10:28:19 am
content: I am to dive a bit deeper in understanding how different types of measuring devices work internally.My question here is, in which way do multimeters (digital or analogue) measure voltage? How do they compare it to a known value, do the necessary steps of having True RMS integration done?With a DMM I understand that later in the chain, an ADC will convert the values- how do they do this and what is with the sample rate?Sadly, Google did not lead me to in-depth knowledge :-(Could someone point me to some ressources?

author: Electro Fan
author_rank: Super Contributor
timestamp: April 02, 2022, 12:05:21 pm
content: If you can get this book it has a lot of the info you are seeking:https://www.ebay.com/itm/373714731573
How does a PLC read a 120VAC input - Page 1
Forum section: electronics / beginners

author: AMWallace123
author_rank: Newbie
timestamp: February 01, 2018, 03:56:49 pm
content: How does a PLC convert a 120VAC input, to a voltage that can be read with surface mount components? Most PLCs have around 10 inputs. I doubt they use a transformer for each 120v input. Does anyone understand the inner workings of a PLC? ~ Thanks

author: Ice-Tea
author_rank: Super Contributor
timestamp: February 01, 2018, 04:01:57 pm
content: Beefy resistor + optocoupler.

author: djacobow
author_rank: Super Contributor
timestamp: February 01, 2018, 04:02:55 pm
content: They use an optoisolator. This is an LED and a phototransistor in one package. The mains drive the LED (current limited by resistors, of course) and the phototransistor can be used on the low voltage side to do whatever. Frequently, it just acts as a pulldown in concert with a resistor pull-up.

author: PartialDischarge
author_rank: Super Contributor
timestamp: February 01, 2018, 04:47:00 pm
content: Given we are talking about analog measurementsthey use an extra-cheap A/D converter that transmits the digital data over an optocoupler. The voltage to measure is scaled-down by a resistive divider before the A/D.To keep it simple and low cost all of this electronics on the 'primary' side is powered from the same voltage it is trying to measure via a high voltage mosfet and a regulating zener.For digital ON/OFF data, driving the led of an optocoupler in an analog way will work

author: rstofer
author_rank: Super Contributor
timestamp: February 01, 2018, 04:56:43 pm
content: When it is a digital input and we're only interested in ON or OFF, an optocoupler will do the job just fine. Sooner or later the signal needs to be converted to DC and, perhaps, filtered before stuffing it into an IO port. There will also be some input protection circuitry at the 120V level.Stripped to the essentials:https://www.myodesie.com/images/wiki/2/PLC23.PNG

author: David Hess
author_rank: Super Contributor
timestamp: February 01, 2018, 06:56:28 pm
content: Dedicated galvanically isolated ADCs are pretty cheap now so that is one way. Another way is to use a linear optocoupler and then do the measurement on the non-isolated side.

author: Jeroen3
author_rank: Super Contributor
timestamp: February 01, 2018, 07:41:31 pm
content: The same way they read DC inputs, except then with some additional current limiting by means of capacitor.You can use a bidirectional optocoupler to save the diode and have one cycle lower latency.(source)

author: David Hess
author_rank: Super Contributor
timestamp: February 01, 2018, 11:27:55 pm
content: If you just want to measure the presence of 120VAC or 240VAC, then that is much easier with just the optocoupler circuit as shown.

author: retrolefty
author_rank: Super Contributor
timestamp: February 02, 2018, 01:02:29 am
content: Another easy method is to use a small 120 vac coil reed relays for each AC channel being read.
How does a STLINK/V2 know when SWD or Jtag mode can be selected - Page 1
Forum section: electronics / beginners

author: aa8pa222
author_rank: Newbie
timestamp: October 22, 2015, 08:28:57 pm
content: I have an eval board that requires a jump to be installed before SWD will work. I installed the jumper and now both Jtag and SWD work as they should. My question is once I installed the jumper how does the STlink/V2 know that the jumper was installed. The jumper is on the output of an and gate that that has 2 inputs USB_Jlink_TMS and Jlink_TMS, the jumper takes the output of the and gate and goes to Jlink_TMS. It looks like the jumper goes back to the STlink/V2 connector. Any ideas will help.

author: stmdude
author_rank: Frequent Contributor
timestamp: October 23, 2015, 07:39:06 am
content: Schematics would be helpful. Since it's an eval-board, they can probably be found online.Edit: Though, in general, I haven't seen a STLink/V2 (or V1) being able to autodetect JTAG/SWD. I've always had to tell the software which interface I wanted to use.

author: aa8pa222
author_rank: Newbie
timestamp: October 23, 2015, 10:43:53 am
content: Yes you do select which interface you want to use via the software. Without the jumper you can only select Jtag. Swd is not available. Once the jumper is in place both Jtag and swd are now available. Let me ask it a different way. What happens to a digital signal when you add it to itself, this is what I see the jumper is doing. The output of a 2 input and gate has one of its inputs jlink_tms jumpered to the and gates output. Then this signal is sent to the mcu. I trying to understand what is taking place when and input is added to itself on the output of an and gate. I can see on a scope frequency changes and pulse duration when switching between Jtag and swd. I need to know why this happens when the jumper is installedSent from my iPad using Tapatalk
How does a typical DMM measure AC current (circuit level)? - Page 1
Forum section: electronics / beginners

author: replaysMike
author_rank: Newbie
timestamp: September 17, 2019, 04:54:41 am
content: Hey all,I've taken apart a few of my DMM's in trying to understand how they are measuring AC current, and scratching my head.I see that they all seem to take the same approach using a shunt resistor (Constantan 0.1ohm). Looking at my Extech EX330 I see a TLC27M2C op amp that looks like its used for measuring the voltage drop on the shunt resistor. There are some other components before it gets there and I can't identify them all (Q4-Q7) so I don't know what they are doing before it hits the op amp.The op amp has 5.9VDC at VCC, and I measured the default output of the op amp (on both outputs) and it's 1.5 VDC. When I run a 1amp AC current through it there is no change in output yet the meter is clearly measuring 1 amp. Perhaps this op-amp doesn't really deal with the current measurement but I can't see anything else that obviously does before it enters the MCU. And if it does, I don't understand how it works as the common mode voltage range is only 0.2-3.0V on that op amp and I'm measuring 120VAC. Because its a floating power supply it doesn't matter?Anyone with more knowledge on the subject? I only half understand it.

author: Kleinstein
author_rank: Super Contributor
timestamp: September 17, 2019, 06:52:18 am
content: The AC current measurement is usually just like DC, with a shunt and than measuring the small voltage. There may be some extra AC amplification with an OP or similar - however with battery operation this is more likely left out to save power.For the AC voltage measurement there are different options: the cheap ones may use a kind of precision rectifier (e.g. an OP circuit with diodes), while the better ones tend to use an analog RMS to DC circuit to get true RMS readings. A few may also use a reasonable fast ADC to sample the AC waveform and than do the RMS calculation in software. With modern DMM chip sets much of this may be part of the big central chip.For higher voltage (e.g. more than 0.2 V) there is a resistive divider at the input. For a cheap meter this could be the same divider also used for DC volts. The 1.5 V level seen could be a virtual ground connected to the common terminal. So relative to the signal ground the supply is more like -1.5 V and + 4.4 V.
how does AB1 differ from AB2 in push pull tube output amp? - Page 1
Forum section: electronics / beginners

author: Deactivated-1
author_rank: Frequent Contributor
timestamp: February 02, 2020, 03:27:05 am
content: is AB2 ultra-linear and AB1 not or is it something different?

author: gbaddeley
author_rank: Regular Contributor
timestamp: February 02, 2020, 05:29:08 am
content: Wikipedia power amplifier classespage has the answer.
How does Anti-Static Mat work? - Page 1
Forum section: electronics / beginners

author: dsab
author_rank: Newbie
timestamp: April 17, 2014, 09:49:46 pm
content: Is this also safe when using an anti-static mat, that your power point(powerbar) is switched off & plug into the outlet. Also that the PSU is switched off and plug into the powerbar. Use a motherboard Standoffs on the psu screw hole & attaching the alligator clip to the standoffs.Is this okay? is the mat grounded?This is a brand new build.What if it’s not a brand new build, what do u suggest?

author: Alphatronique
author_rank: Regular Contributor
timestamp: April 17, 2014, 10:04:26 pm
content: Hinormally recent static mat have >10 meg and up ,so in theory it safe to let a PCB powered and on the mat(for some time mat have go from conductive to disipative for safety reason typical spec was Surface resistivity is 10^8– 10^9 Ohms. )but ideally try to avoid it ,since even if it safe it may affect circuit behaviourbut old mat may much lowerand mat must be connected to EARTH whit supplied cable ,most of time in that cable it put for safety a 1 meg resistor

author: Nerull
author_rank: Frequent Contributor
timestamp: April 17, 2014, 10:10:07 pm
content: Even a 1000V/4.2 Gigaohm megger can't measure the resistance of the top layer of a dual-layer mat (I've tried), so I doubt it will effect any circuit you put on it. It's also not really what he asked.Turning off the power to the power strip or PSU should not disconnect ground, so you should be grounded. It wouldn't hurt to check for continuity between the standoff you're using and the ground pin on the power strip.

author: dsab
author_rank: Newbie
timestamp: April 18, 2014, 02:23:18 am
content: Thanks Nerull for answering my question, I should be grounded if I do it that way.
How does coaxial termination chain attach to device or rack? - Page 1
Forum section: electronics / beginners

author: matthuszagh
author_rank: Frequent Contributor
timestamp: August 14, 2022, 03:39:49 pm
content: I expect this is pretty obvious, but I can't quite figure it out.Some coaxial/RF terminations come with a chain. For example, see the image attached. How is the end of the chain supposed to connect to the device or equipment rack? An image showing its use would also be very helpful. Thanks!

author: mikerj
author_rank: Super Contributor
timestamp: August 14, 2022, 05:02:37 pm
content: Usually mounted via one of the screws on a flange style chassis mount connector, otherwise it will have it's own screw holding it to the panel.

author: jmelson
author_rank: Super Contributor
timestamp: August 14, 2022, 11:06:17 pm
content: Note the chain is not part of the electrical circuit, it is to keep the terminator from being lost.Jon

author: fordem
author_rank: Regular Contributor
timestamp: August 15, 2022, 12:33:25 pm
content: If the terminator is part of a coax ethernet (10base2) network, then one of the two terminators is required to be electrically grounded.

author: Terry Bites
author_rank: Super Contributor
timestamp: August 15, 2022, 01:59:57 pm
content: An M3.5 nut a bolt and a washer. I usually put the hole 25mm or so from the socket centre. It depends on the size of the nut on the back of the BNC.The chain is about 75mm long.
How does FSYNC work on IMUs? - Page 1
Forum section: electronics / beginners

author: axemaster
author_rank: Contributor
timestamp: March 07, 2020, 10:39:28 pm
content: Hi guys, I've been trying to figure this out for a while but with little success.I am working on a hobby project that includes the chip ICM-20602. This is an inertial measurement unit, i.e. accelerometer + gyroscope. It has an input pin called "FSYNC" which stands for "frame sync". This is apparently used for EIS or "electronic image stabilization". Essentially it's some sort of trigger that allows you to synchronize IMU data with the frame rate of a camera.I would really like to use this feature, but despite a lot of googling I am simply unable to find a detailed description of exactly how it works.It seems to be a pretty common feature on IMUs, so hopefully someone here has used it before and can help me figure this out.ICM-20602 Datasheet:https://invensense.tdk.com/wp-content/uploads/2016/10/DS-000176-ICM-20602-v1.0.pdfThanks!

author: ataradov
author_rank: Super Contributor
timestamp: March 07, 2020, 11:46:54 pm
content: FSYNC is just an input signal that is used to generate an interrupt from the sensor. The sensor stores acceleration data in the FIFO for the duration of the frame (between two FSYNC edges) and MCU can go and read the whole buffer in one transaction.That's it, there is nothing special about it. You could really just use VSYNC interrupt from the sensor itself for that, but doing it though the sensor allows you to play with polarity and generally makes writing drivers easier.

author: axemaster
author_rank: Contributor
timestamp: March 08, 2020, 12:15:16 am
content: Just so make sure I understand, you are saying that the FSYNC is gating data collection? As in, the FIFO will only store samples in between 2 FSYNC pulses?I am not sure I understand the role of an interrupt here.

author: ataradov
author_rank: Super Contributor
timestamp: March 08, 2020, 12:18:27 am
content: No, it does not gate anything. It is literally just an external pin that causes an interrupt that will be raised over INT/IRQ pin. Your MCU will go and read the interrupt flags register. If one of the flags set is FSYNC, then it will drain the FIFO.This is just a way to save time by not polling the chip constantly. All you need to do is wait for the interrupt and grab the acceleration data for the whole frame.

author: axemaster
author_rank: Contributor
timestamp: March 08, 2020, 02:27:59 am
content: OK, I think I understand now. Thanks for the help!
How does LED in arduino blinks when program gets uploaded? - Page 1
Forum section: electronics / beginners

author: electrowhiz
author_rank: Contributor
timestamp: May 14, 2018, 06:01:45 am
content: In arduino we will have LED . The LED will blink whenever program gets uploaded. How it happens? I didn't write any code for it? Is it the bootloader responsible for it?

author: Brumby
author_rank: Unknown
timestamp: May 14, 2018, 06:14:58 am
content: Quote from: electrowhiz on May 14, 2018, 06:01:45 amYes.It's an acknowledgement that data is being transferred.

author: electrowhiz
author_rank: Contributor
timestamp: May 14, 2018, 06:20:02 am
content: Tanq

author: darrellg
author_rank: Unknown
timestamp: May 14, 2018, 05:53:42 pm
content: If you look at the schematic for the Uno (https://www.arduino.cc/en/uploads/Main/Arduino_Uno_Rev3-schematic.pdf), you can see that the TX and RX LEDs are conntected to the 16U2, not the 328P. The bootloader runs on the 328P, therefore the bootloader is not flashing the LEDs. The 16U2 is utilized as a USB to serial converter and is programmed to flash the LEDs when appropriate.On Arduinos like the Leonardo (https://www.arduino.cc/en/uploads/Main/arduino-leonardo-schematic_3b.pdf), which don't have a separate chip for USB communication, the bootloader is responsible for flashing the RX and TX LEDs.

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 14, 2018, 07:27:49 pm
content: It is not clear whether you are asking about:1) The RX/TX LED(s) that indicate data/programming activity.2) The built-in LED connected to (typically) pin 13Others have responded to your question if you are asking about (1) The RX/TX LEDs.But if you are asking about the pin-13 LED:Arduinos (genuine, clone, and work-alike) typically come with a demonstration program ("Blink") pre-loaded onto the microcontroller chip. This provides a satisfying experience to the buyer (especially a first-time user). AND, it demonstrates that the chip and board are actually working BEFORE the user attempts to load any code of his/her own. So at least the user knows that the board WAS working when they first received it.

author: electrowhiz
author_rank: Contributor
timestamp: May 15, 2018, 06:22:44 am
content: Tanq for your wonderful information

author: electrowhiz
author_rank: Contributor
timestamp: May 15, 2018, 06:23:27 am
content: Tanq for your information

author: NivagSwerdna
author_rank: Super Contributor
timestamp: May 15, 2018, 06:32:18 am
content: https://raw.githubusercontent.com/Optiboot/optiboot/master/optiboot/bootloaders/optiboot/optiboot.cFlash at start and flash for each character received.Nice to see the easy questions are back.
How does non-restoring division totally eliminate restoration part? - Page 1
Forum section: electronics / beginners

author: shivajikobardan
author_rank: Contributor
timestamp: August 26, 2025, 10:08:49 am
content: Firstly, I must be honest. I have learnt restoring division algorith. And this is what I learnt there.## Basics of divisionz=d*q+swhere z is dividend, d is divisor, q is quotient and s is remainder.## PhilosophyShift left and subtract## How to find quotient?If shift left and subtract greater than zero, quotient bit will be 1.Otherwise, quotient bit will be 0 and restoration will also be performed.## Example(unsigned integer case)z=1011d=0011Initialization:2^k.d=Shift divisor 4(number of bits in divisor) bits left(increase the numerical value of divisor)00110000Calculate its twos complements for future reference: 11010000----Step-4:Initialize remainder s(0)=z=00001011Shift left remainder by 1 bit 2s(0)=00010110Calculate 2s(0)-2^4.dIt will be negative, thus restores(1)=2s(0)=00010110And quotient bit q3=0And so on...I have read in John P Hayes's COA textbook that the difference between restoring and non-restoring algorithm lies entirely on how the next quotient bit is picked.My concern is how did non-restoring division do that now restoration will not be required at all?

author: brucehoult
author_rank: Super Contributor
timestamp: August 26, 2025, 10:18:21 am
content: Compare z and d before you subtract, and don't subtract is d is larger.

author: shivajikobardan
author_rank: Contributor
timestamp: August 26, 2025, 01:15:44 pm
content: I do not quite get it. You mean shifted d right? 2^k.d
How does one allocate different voltages to different circuits from one supply? - Page 1
Forum section: electronics / beginners

author: Dmeads
author_rank: Regular Contributor
timestamp: March 18, 2019, 07:54:25 pm
content: I am a beginner, and I am wondering about how to power different circuits with one supply.Let's say we have a car battery with like 14v, how does that volatge get spread across the various radio, screen, and audio circuits. I'm assuming they don't all run off 14v.I know you can use voltage dividers, but wouldn't that result in power losses if you use resistors?Also with high power circuits, you would need high power dissipation resistors right?If anyone can explain this to me that would be amazing! Also if anyone has any schematics or anything that would be really great.Thanks in advance!

author: Benta
author_rank: Super Contributor
timestamp: March 18, 2019, 08:06:16 pm
content: You use local voltage regulators, meaning each circuit has its own.

author: jeroen79
author_rank: Frequent Contributor
timestamp: March 18, 2019, 08:23:21 pm
content: Depending on the application there are several options.-Linear regulator.Low efficiency but little noise.-Switching DC-DC converter.More efficient but switching adds noise.-Charge pump.For low current applications.-Voltage divider.Most useful if you need some reference voltage with no load.

author: IanB
author_rank: Super Contributor
timestamp: March 18, 2019, 08:40:54 pm
content: Quote from: Dmeads on March 18, 2019, 07:54:25 pmThis tends to happen with modern computer boards.For an analogy, think about the mains supply in your house. Most items need a lower voltage, so you have various "wall wart" or "plug pack" adapters like cellphone chargers that you plug into the mains and get a low voltage out the other side. All of these adapters are various kinds of voltage step-down converter.Similarly, a modern computer board may have a 12 V supply coming in and have it routed around the board like a 12 V "mains". Various chips that need lower voltages, like 5 V, or 3.3 V, or 2.5 V have local voltage step-down converters that take the 12 V "mains" coming in, and produce the required lower voltage going out.The mode of operation of mains adapters and local voltage step down converters on a computer board is very similar. They all tend to be a kind of "transformer" with special circuitry to control and regulate them.

author: rstofer
author_rank: Super Contributor
timestamp: March 18, 2019, 11:25:13 pm
content: Quote from: Dmeads on March 18, 2019, 07:54:25 pmSure they do! Even the engine control unit (ECU) connects to the battery voltage. If anything needs a lower voltage internally then it uses some kind of voltage regulator. But they will all start out by being connected to battery voltage.Others have explained about linear versus switching power supplies and either will work.

author: Dmeads
author_rank: Regular Contributor
timestamp: March 18, 2019, 11:32:21 pm
content: Thanks everyone!!
How does one embed a picture in a post? - Page 1
Forum section: electronics / beginners

author: jcw0752
author_rank: Contributor
timestamp: May 07, 2018, 01:45:11 pm
content: HI,I have a simple question. What is the procedure to embed a picture in a post? I can get an img//img in the post but I can't figure out a procedure to actually get a picture.Thanks John

author: RomDump
author_rank: Regular Contributor
timestamp: May 07, 2018, 02:11:49 pm
content: Quote from: jcw0752 on May 07, 2018, 01:45:11 pmPlease see thisthread.

author: jcw0752
author_rank: Contributor
timestamp: May 08, 2018, 11:48:45 pm
content: Hi RomDump,I appreciate the push in the right direction.My first picture in a postJohn

author: jcw0752
author_rank: Contributor
timestamp: May 09, 2018, 03:34:52 am
content: Good to know I will use it sparingly.John

author: Brumby
author_rank: Unknown
timestamp: May 09, 2018, 04:54:00 am
content: It is good to be conscious about this - but don't get too scared to use it when useful.The thing to be more aware of is the file size of the image. A couple of 100kB images aren't a big worry - but a couple of uncropped, uncompressed images from a 12 megapixel camera aren't going to go down too well for those members with slow internet connections and/or capped plans.If your images don't need all that file size, then reducing them in size will be appreciated by everyone. If, however, you DO have an image that really needs to be big to show what you want, then have it hosted somewhere else and put a link in for those who choose to have a look. Putting a reduced size image in the post is something you can do to give an idea of what the big picture is about, which is helpful.Alternatively, if the image isn't too big, you can upload it to Dave's server as an attachment to a post. SMF automatically inserts a thumbnail which people can then click on to access the full image.
How does poe work? - Page 1
Forum section: electronics / beginners

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: July 30, 2013, 10:14:45 pm
content: Hellohow does power over ethernet work? And how is it done? Another side to this is can it be applied to other communication lines such as serial or will it only work with twisted pair communications?

author: notsob
author_rank: Frequent Contributor
timestamp: July 30, 2013, 10:22:02 pm
content: this took like 3 seconds to findhttp://en.wikipedia.org/wiki/Power_over_Ethernet

author: westfw
author_rank: Super Contributor
timestamp: July 31, 2013, 12:30:55 am
content: I guess your question is a little general to be answered by the wikipedia article.There are two ways that PoE works:1) lower speed ethernet over twisted pair protocols only use two pairs, of the four pairs that exist on an RJ45 connector. So you can "just" run power over the extra wires.2) Ethernet uses a high-speed AC, transformer-coupled signal. You can run a DC level (even in "power" quantities) over the same wires without interfering with the signal.(wikipedia will describe the details of how this is done without frying your non-PoE equipment, setting fire to your wiring, or putting up with excessive power or voltage losses in the long runs typical of "business" wiring.)Yes, similar schemes have been applied to other communications lines. Obviously "string extra conductors" works for any protocol (and so PS/2, ADB, USB and firewire conduct significant amounts of power in dedicated conductors, and Apple used to run power through it's "display connection" cable, and etc.) Low power devices used to "steal" power from the voltages present on "standard" rs232 cables, either by virtue of using extra signals that weren't needed, or "parasitically" by using AC coupling for the signal. For example, RS232-based mice didn't have separate power supplies, back in the day. Finally, there's the Dallas/Maxim "one-wire" protocol, that does bi-directional communications over the +V wire of the two wires used to provide power (+V and GND)
How does power limiting work with audio amplifiers? - Page 1
Forum section: electronics / beginners

author: e100
author_rank: Frequent Contributor
timestamp: March 07, 2018, 08:52:35 am
content: A number of modern guitar amplifiers have a power setting switch, for example 0.5w/50w/100w so that they can be used for practicing at low volumes without turning the volume control down to almost zero with consequent loss of fine control.Is this true power limiting, or is it just an input signal attenuator, as in if you were to massively overload the input, you'll still get 100w coming out the other end?For true power limiting, I would guess for a class D amp you could reduce the DC voltage feeding the output transistors? Is this what they do, and if so, is there an equivalent for old style class B amps?

author: Zero999
author_rank: Super Contributor
timestamp: March 07, 2018, 09:53:50 am
content: It could be an attenuator or it might alter the gain of the amplifier, by changing the feedback resistor values.You'd have to look at the schematic to be sure.
How does the circuit works? - Page 1
Forum section: electronics / beginners

author: Jeeva
author_rank: Newbie
timestamp: April 17, 2020, 04:53:59 pm
content: Hi,Can someone explain how the attached circuit works.Thanks,Jeeva J

author: james_s
author_rank: Super Contributor
timestamp: April 17, 2020, 05:03:44 pm
content: It looks like a voltage to current converter, the amp gets negative feedback from the top of a current sense resistor. What's the circuit used for?

author: Zero999
author_rank: Super Contributor
timestamp: April 17, 2020, 05:38:13 pm
content: Quote from: Jeeva on April 17, 2020, 04:53:59 pmIt doesn't.

author: Jeeva
author_rank: Newbie
timestamp: April 17, 2020, 05:52:45 pm
content: I think it is used to discharge current from HV output PHV.My understanding is since it is a closed loop amp, the voltage at R3 resistor will be same as the voltage at non-inverting input. i.e 0.17V(from voltage divider ckt). Applying ohm's law at resistor R3 we get current as 0.34A (0.17V/0.5R). That means the circuit discharges 0.34A current from drain to source?My doubt is for a P-channel mosfet the current flows from source to drain. How it works here?Please correct me if my understanding is completely wrong.Thanks for your reply.

author: Zero999
author_rank: Super Contributor
timestamp: April 17, 2020, 06:01:32 pm
content: Quote from: Jeeva on April 17, 2020, 05:52:45 pmYes, it won't work with a P-MOSFET. About 25A will flow through the body diode and R3, which will dissipate over 300W. It will work if M3 is swapped for an N-MOSFET.

author: Jeeva
author_rank: Newbie
timestamp: April 17, 2020, 06:13:09 pm
content: What if I provide negative supply voltage, PHV is -100V. Will it work?

author: Zero999
author_rank: Super Contributor
timestamp: April 17, 2020, 06:49:02 pm
content: Quote from: Jeeva on April 17, 2020, 06:13:09 pmNo.

author: Jeeva
author_rank: Newbie
timestamp: April 17, 2020, 07:19:59 pm
content: This circuit is used in power supply schematics and the boards are working and in use. At the PHV point negative supply is given.I am sure the circuit is correct. I am trying to understand how it works.

author: Zero999
author_rank: Super Contributor
timestamp: April 17, 2020, 07:41:52 pm
content: Quote from: Jeeva on April 17, 2020, 07:19:59 pmIt will work if connect N12V to R4, rather than P12V.Why not simulate it and upload the .asc file?

author: Jeeva
author_rank: Newbie
timestamp: April 17, 2020, 08:31:37 pm
content: Attached .asc file.

author: Zero999
author_rank: Super Contributor
timestamp: April 17, 2020, 10:09:27 pm
content: Quote from: Jeeva on April 17, 2020, 08:31:37 pmIt works, once the PHV_raw label is connected properly and the default LTSpice MOSFET model (which is just a small signal device) is replaced with a power MOSFET.

author: Jeeva
author_rank: Newbie
timestamp: April 17, 2020, 10:36:48 pm
content: Thank you, I updated the circuit. So the circuit discharges -350mA of current from drain to source.
How does the diode on this display work? - Page 1
Forum section: electronics / beginners

author: Starlord
author_rank: Frequent Contributor
timestamp: May 11, 2017, 02:40:05 am
content: Page 9, one diode:http://www.buydisplay.com/download/manual/ER-OLED015-1_Series_Datasheet.pdfPage 54, two diodes:http://www.buydisplay.com/download/ic/SSD1351.pdfThese diodes connect to VSL, which is described as a "segment voltage reference pin" for "voltage output low level".I'm guessing this somehow sets the voltage that the display sends to the fets inside it when it wants to turn one of the pixels off. But I don't understand why this wouldn't go straight to ground, or why one example has one diode and the other has two, and what the repercussions would be of having too few or too many diodes there.I do know that my display worked with both one and two diodes. I didn't want to try no diodes and potentially blow the display up as they're $12 each.Page 25 of the second PDF shows how a pixel is wired up if that helps.

author: ataradov
author_rank: Super Contributor
timestamp: May 11, 2017, 02:58:34 am
content: They are just used as more or less predictable voltage droppers. If you notice, on the first diagram they specify Vth =1.4V, and on the second one Vth = 0.7V, but there are two diodes. So the goal of that diode is to drop 1.4 V, and you need to select diode(s) accordingly.
How does the DVB-T2 Dongle work? - Page 1
Forum section: electronics / beginners

author: Lord of nothing
author_rank: Super Contributor
timestamp: November 12, 2016, 01:11:52 am
content: Source:http://mysku.ru/blog/ebay/20164.htmlI have an MN88473.So how does the Dongle work?The Signal does first into the:http://www.rafaelmicro.com/product/view/21and get demodulated?After to the Panasonic MN88473 and what does do it there?Than into thehttp://www.realtek.com.tw/products/productsView.aspx?Langid=1&PNid=22&PFid=35&Level=4&Conn=3&ProdID=257and get send into usb?I try to find the limits of the Chips. The "TV" Software allow me to set AM, FM and NFM in the Radio Setting .ini.I know its possible to run the Dongle with SDR Software. So maybe I get run Amateur Radio in the normal Radio Software?!

author: stj
author_rank: Super Contributor
timestamp: November 12, 2016, 01:27:14 am
content: the rafael chip is a tuner,realtek is a fast A-D,most of those dongles only use 2 chips.the tuner and a very fast A-D sampler.all demodulation etc is done in software.http://sdr.osmocom.org/trac/wiki/rtl-sdr

author: Lord of nothing
author_rank: Super Contributor
timestamp: November 12, 2016, 01:30:13 am
content: What did the Panasonic do there?So that mean there is no limits for the Software?

author: stj
author_rank: Super Contributor
timestamp: November 12, 2016, 01:50:34 am
content: the rafael chip can tune from about 30MHz to about 1.7GHz,other than that, it's down to your processing power and the antenna.

author: Lord of nothing
author_rank: Super Contributor
timestamp: November 12, 2016, 01:53:29 am
content: Some people say there is some kind of hardware decoder inside?!Maybe you can explain why the DVB-T Dongle cant Decode DVB-T2?

author: stj
author_rank: Super Contributor
timestamp: November 12, 2016, 02:00:27 am
content: maybe it can - with the right sofware.
How does the Fluke 789 recognize banana plugs? - Page 1
Forum section: electronics / beginners

author: r0tati0n
author_rank: Newbie
timestamp: October 19, 2024, 12:38:01 pm
content: Hello all,I just had to repair a Fluke 789 my company threw away because the already damaged plug now broke.I noticed when testing the meter on Ampere measurement:When nothing is plugged in, the meter displays mA with -25% on the lower half. pressing the blue button does nothing.When test leads are plugged in (not connected to anything) the meter displays Amps and I can press the blue button for switching between AD and DC.How does the meter actually detect if something is plugged in and switches the display?Asking because I tested the replaced input jack receptacle by holding the tips of test leads into the port connected to a low ampere limited power supply and got no reading.Only after plugging in proper banana plugs and holding the tips into the power supply I got the correct reading.

author: wasedadoc
author_rank: Super Contributor
timestamp: October 19, 2024, 01:01:38 pm
content: I fo not know for certain how that meter does it but a simple, common method is that the socket is not a single contact. A split ring or similar which is bridged by the metal plug.

author: Xena E
author_rank: Frequent Contributor
timestamp: October 19, 2024, 07:30:36 pm
content: Optical test lead detection is used on several Fluke meters.X

author: coromonadalix
author_rank: Super Contributor
timestamp: October 21, 2024, 05:16:43 pm
content: if the barrel socket jack is not split in two if you see it directly, it is optically sensed ...

author: timeandfrequency
author_rank: Frequent Contributor
timestamp: October 21, 2024, 06:12:33 pm
content: Hello r0tati0n,I don't know how exactely how it works on the 789, but Fluke also uses 4 mm banana posts/socket with two separated contacts.Here attached is an excerpt of the Fluke 1653 schematic.The two contacts of the female 4 mm connector are identified as J1 & J2 and the detection sub-system is on the left.When a 4 mm banana plug is inserted, the secondary of the T2 transformer is shorted.Another sub-system of the meter provides the oscillator signal JOSC.The JPD signal provides the information about an inserted banana plug.