hybridfree/eevblog-posts huggingface dataset:
How does the pinout work for this version of the LM317? - Page 1
Forum section: electronics / beginners

author: WarFreak131
author_rank: Contributor
timestamp: December 06, 2020, 05:57:51 pm
content: I am looking to use this LM317 in a project I am going to build:https://datasheet.lcsc.com/szlcsc/Unisonic-Tech-LM317AG-TN3-R_C75510.pdfThe LM317 is a three terminal device, but the TO-252-2 package only has 2 pins plus a tab. The tab is usually ground, but not in this case. The sample drawings only say what pin #1 is. Whatwouldbe pin #2 is cut off of the package. Is the tab considered to be pin 2, or pin 3?Thanks!

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: December 06, 2020, 06:21:54 pm
content: Tab would be pin 2 (VOUT). The tab is always the center pin (not ground) on 3-terminal packages (unless specified otherwise).

author: Siwastaja
author_rank: Super Contributor
timestamp: December 06, 2020, 06:46:01 pm
content: Proper datasheets specify the pinout unambiguously, mentioning "tab" directly, or specifying "tab = pin #x".But, when they fail at doing that, you just need to know that on such classical tab + 2 legs packages, the tab is always pin #2, and the legs are #1 and #3. Many such packages even have a short stub leg #2 available, you can see with a multimeter how it connects to the tab. I sometimes (ab)use this stub leg, for example solder a bypass capacitor there.No, the tab or thermal pad isn't always ground.Oftenit is, and when it is, it's quite helpful.

author: Zero999
author_rank: Super Contributor
timestamp: December 06, 2020, 08:24:27 pm
content: Yes, the middle pin is normally connected to the tab, but in some components it's isolated, in which case it will be stated on the data sheet.In the case of the common bipolar voltage regulator ICs, 78xx, 79xx, LM317, LM337, the centre pin is normally the most negative voltage on the regulator, which is the adjust pin, on the LM317, but is the input on negative regulators such as the LM337.

author: WarFreak131
author_rank: Contributor
timestamp: December 06, 2020, 10:32:40 pm
content: Thank you everyone!
How does this 74LS93 circuit work? - Page 1
Forum section: electronics / beginners

author: tjewell
author_rank: Contributor
timestamp: September 07, 2024, 06:28:43 pm
content: Hi all, I just cannot get my head around this little bit of circuit. It's taken from the schematics of the 80 column board of an odd French computer (the Goupil 2). So we've got a 14.7456 MHz clock hooked up to a 74LS93 which creates a sync pulse for the 6845 video chip. The output (pin 8 -> clk) seems to be running at 1.638 Mhz - the input frequency divided by 9. Which seems wrong to me, I would expect it to be divided by 10. So I'm trying to work out if this is intentional or not. But I cannot for the life of me understand how the 74LS93 is set up, with the QA and QD outputs connected to the resets and how this creates the output. Can anyone help me? Many thanks in advance!

author: m k
author_rank: Super Contributor
timestamp: September 07, 2024, 07:33:11 pm
content: Those are set of dual part chips, and pretty old.A and QA are a separated part, so B and the rest alone are an octal counter.Connecting QA to B adds a bit and it's a hex counter.When R01 and R02 are high the counter is zeroed, so 1001.

author: Benta
author_rank: Super Contributor
timestamp: September 07, 2024, 09:35:35 pm
content: Nasty circuit with runt pulses, but that's how it was done back then.Yes, it counts from 0 to 8 and resets at 9, so divide-by-9 is the result.Outputs are (QC bold):0000000100100011110001010110011110001001 + QA -> RO1 and RO2 high -> reset (plus nice output glitch) -> 0000

author: tjewell
author_rank: Contributor
timestamp: September 08, 2024, 11:24:29 am
content: Doh! QA + QD =~ 1 0 0 1 = 9I really should have spotted that relation. So it's working as intended, if a little bit hacky. Many thanks everyone!
How does this circuit function? - Page 1
Forum section: electronics / beginners

author: jeffjmr
author_rank: Regular Contributor
timestamp: December 03, 2022, 01:28:49 am
content: Since JU1 is in parallel and a dead short bypassing R55 and R56, how does this circuit function? Any resistor in parallel with 0 ohms is 0 ohms.But the circuit does work. It calibrates this power supply’s ammeter. I don’t understand how.Can someone enlighten me?Jeff

author: BillyO
author_rank: Super Contributor
timestamp: December 03, 2022, 01:34:06 am
content: 1) is the jumper in place?2) doe the calibration pot make a difference?

author: jwet
author_rank: Frequent Contributor
timestamp: December 03, 2022, 02:56:25 am
content: My best guess is that its a two point calibration to get rid of an offset that might be on the signal feeding the meter. With the current set to zero, you close the jumper and adjust the mechanical zero on the meter for zero- having the jumper closed, gives you a magnified response. This cancels any offset in the circuit and any meter mechanical offset due to mounting (gravity). You then open the jumper, go full scale on the current and adjust the pot for full scale. You then sweep between zero and full scale on the meter even with some gain and offset errors on the input. The jumper is only used for cal. The meter resistance is usually around 50 or 100 ohms. If you meausre across the pot and the 3.6K, you should get something like 4k when the pot is centered.

author: jeffjmr
author_rank: Regular Contributor
timestamp: December 03, 2022, 04:44:42 pm
content: ‘Doh! My bad, Billy.I shouldn’t have asked until I checked. The jumper may indeed not be closed.Jwet, your response is intriguing but the calibration instructions do not call for changing nor address the jumper.I need to unstack my power supplies so I can take the cover off of one of these (I have two) and check the status of that jumper. These are BW 1743 supplies. They have digital meters.The reason I am looking closely at this circuit, is one of these has fairly accurate and linear meters, and the other does not. The instructions call for calibration at mid scale. I am trying to see what I can do to minimize the errors at the extremes of the scale. It reads high at low values and low at high values so I think?? it may be addressable in the circuit as opposed to just errors internally to the digital meters.Am I on the right track?Thanks for your inputs.Jeff

author: jwet
author_rank: Frequent Contributor
timestamp: December 03, 2022, 06:37:53 pm
content: If the meters have a zero adjust, you could follow my procedure anyway. You seem to have a span and zero type problem.This whole thing could be a left over from a time when they had mechanical meters?

author: jwet
author_rank: Frequent Contributor
timestamp: December 03, 2022, 07:37:23 pm
content: Looked it up on line, the current meter has a zero and a span spot.Check out page 24 -https://bkpmedia.s3.amazonaws.com/downloads/manuals/en-us/1743_manual.pdf
How does this circuit work ? (Arduino auto power changeover circuit) - Page 1
Forum section: electronics / beginners

author: whatsthegeek
author_rank: Contributor
timestamp: December 03, 2017, 02:38:15 pm
content: Hi, I've been trying to understand this circuit:How does it block the USB 5v when the comparator detects there's more than 3.3v at the power jack ?I think there's something I'm not getting xDHope someone can help ^^

author: Nusa
author_rank: Super Contributor
timestamp: December 03, 2017, 03:00:59 pm
content: It's actually detecting more than 6.6V at the power jack. Note the voltage divider reducing it by half before the comparator. The comparator controls the mosfet on the USBVCC line. It's a P-channel mosfet (arrow facing out, not in), so a high output from the comparator will turn it off.

author: danadak
author_rank: Super Contributor
timestamp: December 03, 2017, 03:01:36 pm
content: The comparator trips when the power jack reaches 6.6V, thatin turn turns off the PMOS fet that connects the 5V usbvcc bussto the LP2985 regulator input.Regards, Dana.

author: whatsthegeek
author_rank: Contributor
timestamp: December 03, 2017, 04:36:03 pm
content: Quote from: Nusa on December 03, 2017, 03:00:59 pmOops, just noticed that xDBut there's something that I don't get, won't the current flow through the flyback diode of the mosfet ?

author: glarsson
author_rank: Frequent Contributor
timestamp: December 03, 2017, 04:41:42 pm
content: Quote from: whatsthegeek on December 03, 2017, 04:36:03 pmOnly if the 5V from USB is above 5.6V.

author: Nusa
author_rank: Super Contributor
timestamp: December 03, 2017, 04:58:33 pm
content: Quote from: whatsthegeek on December 03, 2017, 04:36:03 pmWhat he said about diode voltage drop. It probably won't happen. Even if it does likely no harm done.I believe the real purpose of the circuit is to keep the 5V voltage regulator from trying to power the USB line.

author: whatsthegeek
author_rank: Contributor
timestamp: December 03, 2017, 06:28:43 pm
content: Ok, thanks for the explanationI remade the schematic for my own device, is it correct ? would you change some of the components ?

author: Peabody
author_rank: Super Contributor
timestamp: December 03, 2017, 07:01:41 pm
content: That's not quite the same circuit as your first one. Does Vin of the 3.3V regulator need to be tied to +5V instead of Vcc?

author: whatsthegeek
author_rank: Contributor
timestamp: December 03, 2017, 07:45:52 pm
content: Yes, it needs to get power from the 5v rail otherwise, the board won't get 3.3v when powered from USB

author: danadak
author_rank: Super Contributor
timestamp: December 03, 2017, 09:00:46 pm
content: You should add some hysteresis on comparator -http://www.analog.com/en/analog-dialogue/articles/curing-comparator-instability-with-hysteresis.htmlRegards, Dana.
How does this current limiter work? - Page 1
Forum section: electronics / beginners

author: Sudo_apt-get_install_yum
author_rank: Regular Contributor
timestamp: June 10, 2020, 06:26:03 am
content: Hello!Could someone please explain how this current limiting circuit works?I have never seen anything like it, the components is a LM317 voltage regulator with a resistor between the load and output. Voltage input is 24VDC and output is 24VDC. See the attached image.Thanks for any help!

author: tszaboo
author_rank: Super Contributor
timestamp: June 10, 2020, 07:02:11 am
content: The LM317 regulates the output to keep 1.2V (as I recall) between thee output pin and the adjust pin. If the current is low, the voltage drop on the resistor is less than 1.2V. If you try to pull more current, then it starts regulating, and voltage drops on the LM317.

author: mikerj
author_rank: Super Contributor
timestamp: June 10, 2020, 09:28:41 am
content: Note that the rail voltage labels are misleading, if you are putting 24v in you won't be getting 24v out even when not in current limit. The dropout voltage of the LM317T could be as much as 2.5v at high temperature max current.
How does this drop the voltage down without a resistor? - Page 1
Forum section: electronics / beginners

author: Beamin
author_rank: Super Contributor
timestamp: March 28, 2021, 07:38:22 pm
content: This goes from live 220v to 24 or 17 volts. How does it do this without a resistor or regulator?

author: MikeK
author_rank: Super Contributor
timestamp: March 28, 2021, 08:05:17 pm
content: What do you mean?...The zener is setting the voltage.

author: themadhippy
author_rank: Super Contributor
timestamp: March 28, 2021, 08:26:30 pm
content: the 330nf capacitor is pretending to be a resistor,the magic phrase to search for is capacitive dropper

author: TimFox
author_rank: Super Contributor
timestamp: March 28, 2021, 08:39:47 pm
content: Since the reactance of the capacitance is much higher than the load resistance (Zener or relay), it limits the current nicely from the high voltage source into the load. A good capacitor will not dissipate power and heat up, while a 10 k resistor would dissipate about 5 W with 200 V across it. That is approximately the reactance of 330 nF at 50 Hz.
How does this heatsink mate with a to-220? - Page 1
Forum section: electronics / beginners

author: Chai
author_rank: Regular Contributor
timestamp: February 14, 2017, 06:33:53 pm
content: The bolt hole isn't drilled.

author: Karlo_Moharic
author_rank: Regular Contributor
timestamp: February 14, 2017, 06:39:24 pm
content: Could you give me a bit more information about heatsink?

author: danadak
author_rank: Super Contributor
timestamp: February 14, 2017, 06:40:53 pm
content: Some are designed with spring metal U clip that presses tab against heat sink.See attached.Regards, Dana.

author: Chai
author_rank: Regular Contributor
timestamp: February 14, 2017, 06:41:18 pm
content: https://www.digikey.com/products/en?keywords=AE10851-ND

author: Chai
author_rank: Regular Contributor
timestamp: February 14, 2017, 06:44:55 pm
content: Got it from digikey and there was no clip included.

author: Mr.B
author_rank: Unknown
timestamp: February 14, 2017, 06:57:54 pm
content: As danadak says; there is a metal U clip required.The hole of the TO-220 device sits over the 'pimple' sticking out of the heatsink and the spring clip secures the device to the heatsink.Absolutely a spring clip is required.Similar to the shot below.

author: free_electron
author_rank: Super Contributor
timestamp: February 14, 2017, 07:28:45 pm
content: Quote from: Mr.B on February 14, 2017, 06:57:54 pm<-THIS

author: Chai
author_rank: Regular Contributor
timestamp: February 14, 2017, 07:35:23 pm
content: Ah ok! It is normal practice to not include the clips with the heatsink?

author: SeanB
author_rank: Super Contributor
timestamp: February 14, 2017, 07:53:17 pm
content: Yes, as you can order a few versions of the heatsink, but there is only one clip style.

author: Chai
author_rank: Regular Contributor
timestamp: February 14, 2017, 07:59:18 pm
content: All good now. Thanks everyone

author: Wollvieh
author_rank: Contributor
timestamp: February 15, 2017, 01:29:11 am
content: The picture is not too detailed, but could it be the hole is already prepunched? So you just pop it out with a rusty nail and an old shoe, if drilling is no alternative.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 15, 2017, 04:40:48 am
content: Could also be a mis-struck part.Though, that pip on the back would be an awfully convenient grab point for a spring clip!You wouldn't want to have to drill through it BTW -- you can do it a few times, but the anodize finish will punish drills; it's hard even on carbide tooling.Tim

author: Chai
author_rank: Regular Contributor
timestamp: February 15, 2017, 10:49:05 pm
content: Quote from: T3sl4co1l on February 15, 2017, 04:40:48 amBought 4. All the same. It's clip to nip like others have said.

author: mmagin
author_rank: Frequent Contributor
timestamp: February 16, 2017, 01:37:08 am
content: Quote from: T3sl4co1l on February 15, 2017, 04:40:48 amLooks like it is correct, from the drawing:
How does this sound-card oscilloscope probe circuit work? - Page 1
Forum section: electronics / beginners

author: Yuu
author_rank: Regular Contributor
timestamp: April 26, 2023, 12:40:07 am
content: Was looking at using a soundcard for spectrally analyzing audio signals since it will be better than my Rigol 1054Z at the task and I came across the circuit attached.My idea so far is to use a potentiometer with the slider terminal tied to one of the other terminals and use that to voltage divide my probe input. Note that the load is known (for a mic input I think 60 ohm). People sometimes use a potentiometer in normal config and not in a rheostat config like I suggest here. I think either would work. I don't think I favor one or the other.Anyway, I saw this circuit and I don't know how it works. As far as I know, voltage regulators, say a 5V one, would take an input voltage with some headroom for dropout voltage and then regulate that down to 5V at the output. Surely it must function as a voltage divider in some form since the mic input is expecting about 10mV but I can't really reason how it would do that. Any ideas?

author: Kim Christensen
author_rank: Super Contributor
timestamp: April 26, 2023, 12:47:14 am
content: Whoever designed that is a moron or just plain evil.

author: YurkshireLad
author_rank: Frequent Contributor
timestamp: April 26, 2023, 12:54:26 am
content: Quote from: Kim Christensen on April 26, 2023, 12:47:14 amCan you explain why, so those of us that are unable to read your mind (and also too stupid to know why) can understand. Asking for a (stupid) friend.

author: Kim Christensen
author_rank: Super Contributor
timestamp: April 26, 2023, 01:07:13 am
content: Quote from: YurkshireLad on April 26, 2023, 12:54:26 amThose are 5V regulators. They can take a positive DC voltage from 7V to 35V and reduce it to 5V. An oscilloscope & probe should be able to take a large range of voltages and polarities (+- 50mV all the way up to +-100V or higher, both AC and DC). This circuit would fail at best, could destroy your sound card, kill you, and probably all accomplish 3 at once if you're unlucky and unskilled.

author: themadhippy
author_rank: Super Contributor
timestamp: April 26, 2023, 01:08:41 am
content: https://www.eevblog.com/forum/beginners/7805-for-sound-card-input-protection/msg4563376/#msg4563376

author: radiolistener
author_rank: Super Contributor
timestamp: April 26, 2023, 10:06:35 pm
content: Using voltage regulator to limit voltage on sound card input is a bad idea. You're needs to use suppressing diodes for that.

author: Yuu
author_rank: Regular Contributor
timestamp: April 27, 2023, 12:00:07 am
content: Quote from: themadhippy on April 26, 2023, 01:08:41 amHahahaha I'm glad I wasn't going insane and that the circuit really didn't make much sense. I also will need to try the search function next time.Thanks Kim, Hippy, and Radio for the feedback. I think I'm going to end up doing something like image attached. It should let me probe up to about 15V
How does this VR work ? - Page 1
Forum section: electronics / beginners

author: huu_tri0101
author_rank: Contributor
timestamp: November 14, 2013, 08:12:09 pm
content: How does it work ?schematic for this VR.Thank you guys a lot.

author: Andy Watson
author_rank: Super Contributor
timestamp: November 14, 2013, 09:01:00 pm
content: Quote from: huu_tri0101 on November 14, 2013, 08:12:09 pmThe usual way. You turn the black bit in the middlehttp://www.alps.com/WebObjects/catalog.woa/E/HTML/Potentiometer/RotaryPotentiometers/RK14K12/RK14K1240062.htmlThere's more here:http://www.alps.com/WebObjects/catalog.woa/E/HTML/Potentiometer/RotaryPotentiometers/RK14K12/RK14K12_list.html

author: Balaur
author_rank: Unknown
timestamp: November 14, 2013, 09:02:40 pm
content: Looks like a stereo, 7 pin, rotary potentiometer with a D shaft.Most likely a linear one, with a detent in the middle.

author: huu_tri0101
author_rank: Contributor
timestamp: November 15, 2013, 02:08:25 pm
content: thank you a lot
How far up the code stack should I start it - Page 1
Forum section: electronics / beginners

author: nissanvietnamvn
author_rank: Newbie
timestamp: June 14, 2019, 08:28:11 am
content: Looking to write a microcontroller application, I'm building a rowing computer so first version is usb, accelerometer, display, sd card. The general concept is read sensor data do some math and store it to memory & display it on screen. At some later time offload the data via usb. The SD card was a shortcut idea to avoid the usb data part on the initial go around. I'm planning to use an STM32F0 to start with. I have a SW background so I'm kinda struggling with the whole 'roll your own' approach for everything.I'm pretty certain I need a bootloader as I want to flash firmware updates via usb. What are my options here? I found OpenBootloader but that was about it, is there anything else worth looking at?I looked around for some kinda OS and came across the concept of RTOS, i think this is probably a bit to much for my needs but is there other maybe less heavy loop/scheduler type frameworks? (i'm hopefully searching for the wrong terms which is why i can't find much)juck

author: cur8xgo
author_rank: Regular Contributor
timestamp: June 14, 2019, 03:56:06 pm
content: Quote from: nissanvietnamvn on June 14, 2019, 08:28:11 amYou have a vast....VAST...selection of microcontrollers out there to choose from. I would suggest picking one that is as easy for you to get your head around as possible (development environment and internal complexity), especially if you are already struggling with the roll your own aspect. How did you justify the STM32F0? Is that really needed or could you use a much simpler MCU that you could get off the ground with much faster?If you are thinking RTOS and you have a SW background, just make your own state machine and go from there.
How gentle can a PnP be? - Page 1
Forum section: electronics / beginners

author: pete_flex
author_rank: Newbie
timestamp: December 05, 2019, 04:00:21 pm
content: Bit of a newbie question but I don't have a lot of experience with PnP or roboticsI'm asking if there are an PnP machines out there that can be programmed to pick up the components more gently as standardI thinking of using a PnP machine to position silicone Sires (look like chips but light can pass through them on an IR/ LFI reader) onto cartridges of a standard microscope slide size (25mmx75mm)From what I see, the PnP nozzle has to press down on the component, then pull vac to get it off the reel then stick the component down on to the paste.The cartridges used will have exposed adhesive to hold the chips down. My only concern is how forceful a PnP machine is.I'm unsure if I should be looking at a 5-axis robot arm and allow it to pick & place the sires onto the cartridge.
How good is this PCB layout? It's my first board - Page 1
Forum section: electronics / beginners

author: amin08
author_rank: Contributor
timestamp: November 17, 2017, 08:16:17 pm
content: This is my first board designed in Eagle, and as a noob, I think that someone specialized in PCB layout should give me advice on how to do it well.

author: Rerouter
author_rank: Super Contributor
timestamp: November 17, 2017, 09:08:41 pm
content: PCB design is literally an art form, however luckily it has underlying principles that tell you whether its likely to run well or not.Most of the following are improvements, there is always a trade off for how long the improvments take to implement vs how much you gain by making then,Ok, so first off the mark, you have multiple trace breaking the ground plane under USB differential pairs, this is a no-noNext up the differential part is quite different in length, likely outside the spec, have the differential pair exit left tightly grouped then run to the micro, this will decrease the skew.The 3 pin regulator without its tab actually connected to ground, those via's do almost nothing for it, as fiberglass is an insulator instead you should create 2 small filled zones for that tab (one on each side), and via stitch only in that zone,For the crystal, turn the left crystal capacitor 180 degrees and hop the right crystal trace with it, you want both there ground pads very close to the top left ground pin of the micro,Your digital wires follow some very odd looking grouped routing, e.g. top left, space them a bit wider, to reduce crosstalk, and run them a bit more direct.Your reset pin trace to the ICSP header crosses a lot of traces, if noise couples in to him, it can cause weird glitches,The lower mounting hole does not look like it leaves enough room for a screw head.D4 can be run on the top side, however you chose to jump him to the bottom.Your analog traces cross many digital traces,The diode in the bottom left could be rotated 90 degrees counter clockwise and would tidy up that power trace wiring,
How hot should a 120V to 12V transformer be getting at low current ? - Page 1
Forum section: electronics / beginners

author: lordvader88
author_rank: Frequent Contributor
timestamp: March 14, 2018, 12:15:20 am
content: I have 2 transformers, rated 120V:12V @1 or 2 amps, both weigh about 0.5lb or more. 1 from a little radio/ghetto BLASTER, and 1 is a certified wall wart. And just running well under 50mA most of the time, they still get VERY hot after a few hours.Is that normal ?

author: BrianHG
author_rank: Super Contributor
timestamp: March 14, 2018, 02:21:37 am
content: Check the power supply input voltage ratings. Old ones may be designed for 110v, and you power coming into you house may be above 125v. This shouldn't do much, maybe make the transformers warm to the touch, but not 70 degrees centigrade. Some older transformers are just designed to run near the core's saturation point, so, the get warm.If you have a properly safe setup to do so, can you tell us how many ma AC the transformers are drawing on the 125v side when nothing is connected on the output.

author: floobydust
author_rank: Super Contributor
timestamp: March 14, 2018, 02:44:10 am
content: I find cheap wall wart transformers run around 35-45C; Copper and steel are expensive so they push the flux-density and the core & primary gets quite warm, even at no load.After a few years the plastic is all discoloured.Older ones were not like this, I have a Sony 9V 1A adapter that is stone cold with 122VAC in, but it's huge.Hammond power transformers (166/167) went through a phase where they made them in China instead of Canada. For the same specs/part number the chinese parts ran quite hot. It was a debacle, as they should have changed the part number. Manufacturers were used to a level of quality. Hammond had to change the design spec from being so cheap.If it's too hot to touch like 80C, I had one transformer that I think has a shorted turn that caused that.

author: amyk
author_rank: Super Contributor
timestamp: March 14, 2018, 10:43:46 am
content: Check if there is any DC bias on the mains, which could be saturating the core partially on each cycle. Another thing you can do is look at the output waveform --- it won't be a perfect sine, but it should not be too distorted or unbalanced.

author: lordvader88
author_rank: Frequent Contributor
timestamp: March 16, 2018, 05:18:00 pm
content: I'll check the AC input current later. But assuming it just runs that hot, I should just add a few holes to the plastic case and a mini fan....darn, they got thrown out years ago by accident.

author: floobydust
author_rank: Super Contributor
timestamp: March 17, 2018, 02:42:56 am
content: If you measure the transformer's primary current, you may get misleading (high) numbers.You see magnetization current which has high peaks (not a sine wave, need true RMS), and mostly out-of-phase with mains voltage so the power (factor) is low.All you can do is add cooling and ensure there's a primary fuse if the transformer does cook.
How identify JST connector type? - Page 1
Forum section: electronics / beginners

author: bitwelder
author_rank: Super Contributor
timestamp: November 16, 2014, 08:34:57 am
content: Has anyone a page that helps to identify the various JST connector types?I have a miniboard with a tiny 2-pin JST, and a cable coming from a different board with a different 2-pin JST connector (just a teeny tiny bigger), so I'd like to know what should I order to make a JST-male-x-to-JST-female-y adapter.For the record, the cable is to provide power to a SSD.EDIT: after some browsing on Digikey catalog I think it's about JST-PH (2.0 mm pin pitch) and JST-XH (2.5 mm pin pitch).

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: November 16, 2014, 12:35:22 pm
content: google image search can be useful for this

author: Kjelt
author_rank: Super Contributor
timestamp: November 16, 2014, 12:44:41 pm
content: Quote from: bitwelder on November 16, 2014, 08:34:57 amUse a caliper between the pins on the board and than you know.
how IEEE work - Page 1
Forum section: electronics / beginners

author: SDBFG
author_rank: Contributor
timestamp: April 23, 2018, 07:17:18 am
content: hellohow IEEE worki mean what does it do?

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 23, 2018, 08:01:19 am
content: gather all engineers and professors. anybody publish writing may get royalty, profit gained will be used for humanity, so thats what they said. or are you talking IEEE the fpga library?

author: SDBFG
author_rank: Contributor
timestamp: April 23, 2018, 08:28:00 am
content: yes sirFPGAand embedded system plc

author: SDBFG
author_rank: Contributor
timestamp: April 23, 2018, 01:46:25 pm
content: please list some so that i can learn sir

author: rstofer
author_rank: Super Contributor
timestamp: April 23, 2018, 02:17:47 pm
content: https://www.cs.sfu.ca/~ggbaker/reference/std_logic/You can just Google for 'ieee.std_logic_'

author: Mr. Scram
author_rank: Super Contributor
timestamp: April 23, 2018, 02:46:40 pm
content: It looks like SDBFG could use some help on how to start appropriate and fruitful threads. SDBFG, it would help if you investigated yourself first a bit and asked questions about what you found after that. Just injecting a question like this into a forum is unlikely to get you far.

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 23, 2018, 03:10:01 pm
content: the real turing test for eevblog members... one i know FPGA is Altera Cyclone II, now you can google that...the fellow members from hereshould chime in...
How important is solder mask in between pads? - Page 1
Forum section: electronics / beginners

author: Blitzschnitzel
author_rank: Regular Contributor
timestamp: November 07, 2019, 05:01:54 pm
content: So, I’ve asked JLCPCB what their minimum solder mask width is and the answer was 0.254 mm. When I make some pads smaller I can make that but there is one component where there is no way that I can get solder mask in between the pads.How important is solder mask in between pads? And how much does solder paste stick to bare FR4?

author: ejeffrey
author_rank: Super Contributor
timestamp: November 07, 2019, 05:42:41 pm
content: It is a tradeoff, but we pretty regularly omit solder mask between pads on fine pitch devices. With the right solder stencil and reflow profile it isn't too bad for reflow assembly, it can be more problematic for hand soldering or rework.

author: thinkfat
author_rank: Unknown
timestamp: November 07, 2019, 06:07:07 pm
content: Solder doesn't really stick that much to FR4, the main aspect solder mask helps with is keeping the pad area fenced against the connecting trace. Otherwise, the copper trace would wick the solder alloy away from the pad and you'll likely not get a sufficient fillet. With that in mind, solder mask between pads is not all that important. On the contrary, it's better to have no solder mask at all instead of small slivers of it flaking off because they don't stick to the FR4 during reflow.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 07, 2019, 06:10:58 pm
content: It's not much thickness but it definitely helps the solder roll around between pads, whether it's paste coalescing onto the pads, or errant balls or bridges floating around.10 mil min web is embarrassingly wide, which I guess tells you just how bargain-barrel they've optimized their process. Don't get your hopes up, and all that.It's a few bucks more from a fab with better rules. Well worth the ease of assembly.Tim

author: thinkfat
author_rank: Unknown
timestamp: November 07, 2019, 07:17:52 pm
content: Quote from: ejeffrey on November 07, 2019, 05:42:41 pmUsing ample flux helps with that rework and hand assembly business.

author: Blitzschnitzel
author_rank: Regular Contributor
timestamp: November 08, 2019, 12:01:20 pm
content: Ok I don't need to worry then. Thank you guys!

author: TheHolyHorse
author_rank: Regular Contributor
timestamp: November 10, 2019, 12:41:21 pm
content: I've ordered boards from JLC with 0.2mm soldermask width between some pads with no issues at all.
how is current limited or regulated on step down buck converters?  - Page 1
Forum section: electronics / beginners

author: little_carlos
author_rank: Regular Contributor
timestamp: April 03, 2016, 05:22:46 am
content: Hi, how can the current can be limited or regulated on a step down buck converter? if the voltage is driven by the duty cycle, is the current determined by frecuency or something? how can i regulate the current on a simple switcher like lm2576 or similar?

author: Seekonk
author_rank: Super Contributor
timestamp: April 03, 2016, 06:38:48 am
content: You fake the feedback pin into thinking the output is higher than it actually is. Use a diode to isolate the feedback pin from current control circuit. Low it is ignored and going high will shut down the PWM. If I remember this is similar to 2596 and pin #5 can also do this. Let it go high ans it shuts down. This pin is very fast and it will look like analog control.

author: mikerj
author_rank: Super Contributor
timestamp: April 03, 2016, 10:15:36 am
content: Quote from: little_carlos on April 03, 2016, 05:22:46 amOhms law: I=V/RFor a normal resistive load, current is determined by the voltage. To reduce the current you reduce the voltage, exactly like any other kind of power supply. As Seekonk says, to reduce the output voltage you raise the voltage on the feedback pin.
How is led half angle measured - Page 1
Forum section: electronics / beginners

author: mercurial
author_rank: Regular Contributor
timestamp: March 25, 2024, 07:04:12 am
content: Hi,Was wondering if the Led half angle is measured from the tip of the led or from the actual light origin inside the led package.I couldn't find any definitive references regarding this.For example this documenthttps://www.silabs.com/documents/public/application-notes/AN521.pdfshows 2 different figures (attached)Its not really clear from what point is the half angle measured.

author: CosteC
author_rank: Regular Contributor
timestamp: March 25, 2024, 08:18:25 am
content: Generally from optical source. Almost every led has some lenses and mirror inside.However in practice it does not matter if real LED is shifted 1 mm from optical source with optics. Partially also due to not-so-great repeatability of encapsulation process.

author: mercurial
author_rank: Regular Contributor
timestamp: March 25, 2024, 08:59:29 am
content: Quote from: CosteC on March 25, 2024, 08:18:25 amHi thanks for the info.So if I want to draw rays from the Led extending outward it would be from the led inside the package correct? However we do not know the behaviour of the internal lens, we only know that the datasheet specifies an half angle of some degrees say 10 deg. But I'm not sure from where do I extend the rays? using that 10 deg value.

author: ArdWar
author_rank: Frequent Contributor
timestamp: March 25, 2024, 09:01:41 am
content: It's often specified from the optical center, i.e. the center of the semiconductor surface area.In practice soldering will be much less repeatable than encapsulation in my experience. A bit of shift in optical center is much less impactful than tilting from uneven soldering.

author: CosteC
author_rank: Regular Contributor
timestamp: March 25, 2024, 02:02:46 pm
content: Drawing rays is also bit tricky.Half angle is angle at which intensity drops to 50% (common criteria). So a little more than half angle there is 49% of full brightness. Most LEDs do not have sharp characteristics.I would assume cone of light starts at structure. It is probably not exactly true due to lens but also not far from truth.@ArdWar pointed also inaccuracies of soldering, which add too.

author: DavidKo
author_rank: Frequent Contributor
timestamp: March 27, 2024, 07:42:10 am
content: The LEDs are not point light source. This angle is only approximation from big distance where you can replace it with the point light source. For optical simulations the LED suppliers have measured light sources which can be imported to optical simulation programs.

author: CosteC
author_rank: Regular Contributor
timestamp: April 02, 2024, 06:55:05 pm
content: Quote from: DavidKo on March 27, 2024, 07:42:10 amThis is nicely visible in many LED torches with ZOOM option - you usually can project die image on wall.Anyway, normal, soldered LED is not optically precise instrument.
How is pulse mode useful in a noise generator? - Page 1
Forum section: electronics / beginners

author: elroy
author_rank: Regular Contributor
timestamp: July 16, 2019, 02:06:44 am
content: Based on a recommendation, I'm looking at obtaining one of these broadband noise generators for use evaluating RF filters in conjunction with an SDR:https://g8fek.com/noise-gen.htmlBecause I work with LF/VLF gear, my first thought was to go with the BBGen+ model, which covers down to 20 kHz.The only thing I'm stuck on is that I see the BBGen-pulse model includes a 5 Hz pulse mode.I doubt that I would need or use it, but how is a pulse mode useful in a noise generator? How is it typically used?

author: tggzzz
author_rank: Super Contributor
timestamp: July 16, 2019, 08:45:26 am
content: To distinguish noise from the noise source from other noise.

author: elroy
author_rank: Regular Contributor
timestamp: July 16, 2019, 04:02:43 pm
content: Thanks!
How is the -12V rail supplied in the new PC PSU's with buck convertersForLVRails - Page 1
Forum section: electronics / beginners

author: Deactivated-1
author_rank: Frequent Contributor
timestamp: December 25, 2023, 02:01:09 am
content: How is the -12V rail supplied in the new ATX PSU's that use buck converters for the 5V and 3.3V rails? Does it just use an unregulated winding on the main transformer?

author: Andy Chee
author_rank: Super Contributor
timestamp: December 25, 2023, 02:32:24 am
content: Yes, a separate winding is used to obtain -12V. It is sometimes regulated by a 7912 regulator, but can also be "cross-regulated" via the main 5V rail (using a common choke where all voltage rails pass through).

author: ArdWar
author_rank: Frequent Contributor
timestamp: December 25, 2023, 03:44:43 am
content: These days it's often a "parasitic" flyback converter with such low current capacity and bad load regulation that you aren't even supposed to draw any current from it.I don't know if they even use 7912 anymore after the strict vampire power legislations.
How  is  the   rigol  ds2072? - Page 1
Forum section: electronics / beginners

author: mazhongqiang
author_rank: Newbie
timestamp: December 17, 2013, 04:47:39 pm
content: hello! I'm a student engaged in designing electrical circuits from China,I'm want to know how is the ds2072?Thanks!

author: AndreaEl
author_rank: Contributor
timestamp: December 17, 2013, 06:42:25 pm
content: The DS2XX2 Series has been replaced by the new DS2XX2ASeries in some Country. And in future in all country i think.If you need the website only for info you can check the EU website of Rigol:http://www.eu.rigolna.com/products/digital-oscilloscopes/ds2000/If you want buy a "old" DS2XX2 Series Oscilloscope ask in your country distributor if there are a "old" available.

author: mazhongqiang
author_rank: Newbie
timestamp: December 18, 2013, 02:44:05 am
content: Thank you for answering my question.And I also want to know how the quality of the ds2072a is?And the reliability?

author: Hideki
author_rank: Frequent Contributor
timestamp: December 18, 2013, 10:30:00 am
content: Since you haven't done it yet, go to the Test Equipment subforum and read all the posts about the various Rigols. For example this thread:https://www.eevblog.com/forum/testgear/first-impressions-and-review-of-the-rigol-ds2072-ds2000-series-dso/

author: Rigby
author_rank: Super Contributor
timestamp: December 18, 2013, 02:28:15 pm
content: They're good devices. They're very capable. It's a good choice for an oscilloscope.If you want details, there are lots of details if you search this forum, or you can ask here.
How is this clippy spacer called? - Page 1
Forum section: electronics / beginners

author: fabiodl
author_rank: Frequent Contributor
timestamp: May 05, 2020, 02:29:18 pm
content: How is this clippy (the "arrow" point squeezes, enters the hole, and widens) thing called?

author: Galaxyrise
author_rank: Frequent Contributor
timestamp: May 05, 2020, 04:26:00 pm
content: "snap-fit"?https://www.essentracomponents.com/en-us/s/pcb-spacers/snap-fit

author: fcb
author_rank: Super Contributor
timestamp: May 05, 2020, 05:04:17 pm
content: Be super careful with essentra.What they show on the website, and what actually turn up might be substantially different - they have big problems on the website (I'm in the middle of trying to extract a refund for some stuff that is totally not what was shown).They do PDF versions of their catalogues - use them instead (their advice to me!).

author: Gregg
author_rank: Super Contributor
timestamp: May 05, 2020, 05:34:07 pm
content: I also have had problems with Essentra / Reid Supply or whatever they want to call themselves. Their web listings are totally bonkers and getting the correct item just isn't worth the effort of buying from them. If you send something back, it takes them forever to give you a credit. I really don't know how they stay in business.

author: fabiodl
author_rank: Frequent Contributor
timestamp: May 06, 2020, 03:53:04 am
content: Thank you, I searched for their product on digikey, and found this whole categoryhttps://www.digikey.com/products/en/hardware-fasteners-accessories/board-supports/578And thanks for the advice on essentra, I'll watch out!
How is this connector called and how is the crimping tool for it called? - Page 1
Forum section: electronics / beginners

author: dusan
author_rank: Regular Contributor
timestamp: September 17, 2025, 08:40:32 am
content: This connector that goes on end of wires that goes into breadboards, and the crimping tool, how is it called?Edit: followup question, is there a better version of it (for a breadboarding)

author: Smokey
author_rank: Super Contributor
timestamp: September 17, 2025, 08:51:39 am
content: No idea what that specific pin is, but a "universal crimper" like the iCrimp SN-2549 would probably do the job fine for making breadboard wires.

author: mtwieg
author_rank: Frequent Contributor
timestamp: September 17, 2025, 10:50:13 am
content: I believe that is what's often referred to as a "dupont" connector.This page has tons of info on them.

author: wraper
author_rank: Unknown
timestamp: September 17, 2025, 11:14:09 am
content: Quote from: Smokey on September 17, 2025, 08:51:39 amIt's Mini-PV ("Dupont") connector. SN-2549 and 99% of similar looking crimping tools will crush wire insulation tabs. You need SN-025 or similar with round insulation die to crimp this properly.

author: voltsandjolts
author_rank: Unknown
timestamp: September 17, 2025, 12:46:04 pm
content: Yeh, as wraper says, most crimp tools will crush the insulation tabs with similar profile to the wire crimp.The SN-25 has a round profile for the insulation tabs, so contact will fit in it's housing.
How is this mosfet being switched? - Page 1
Forum section: electronics / beginners

author: kazzle101
author_rank: Contributor
timestamp: January 15, 2022, 09:58:56 am
content: HelloI recently repaired my Duratool solder sucker machine, there was a bad solder joint on the main mosfet, the temperature control had stopped working and it was getting hot enough to glow red.I traced out the circuit for the section that switches the iron. I found that it sends a PWM signal (green wire) through an opto-isolator which switches a n-mosfet to switch power to the heating element.The bit that confusing me is that opto-isolator appears to be switching across the 18v rail rather than pulling the gate high? The gate doesn't appear to be being low when off?Can anyone explain?ThanksKarl.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: January 16, 2022, 02:32:27 pm
content: The optocoupler enables the voltage divider consisting of the resistors (and the resistance of the optocooupler, I do not know optocoupler resistance).Since the 470K resistor is on the Neg side, the gate voltage will be closer to +18volts when optocoulper is ON.I am assuming the bottom voltage on your schematic is a Neg 18 VThe voltage is applied to the gate and turns the Mosfet ON.Otherwise the gate is kept at a neg voltage to keep it OFF.I think the ON gate voltage of the output Mosfet is +5 volts, so I would think that the Gate voltage would be higher than that, perhaps 10 V.Why are there 5W resistors, do they supply something else also?
How is this possible? No continuity on one side of header pin!@! - Page 1
Forum section: electronics / beginners

author: mart1n
author_rank: Contributor
timestamp: April 06, 2016, 08:29:05 am
content: I'm working on building a custom multirotor drone and I have a ground pin on my flight controller board that has continuity with ground on all sides of a header pin except one side. If I touch to probe to any part of this side I get absolutely no continuity but if I move it to any other side or even the tip of the header pin, I get continuity again!How is this possible? and does it really matter? The pin connects with a female header/dupont connector. I'm sure that three sides are enough to make a proper connection to ground?Thanks for the help!

author: tszaboo
author_rank: Super Contributor
timestamp: April 06, 2016, 08:30:20 am
content: I think you should post a picture of the header for us, to be able to help you.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: April 07, 2016, 12:46:57 am
content: A layer of corrosion, glue or even solder flux may be interfering with your probe's ability to make an electrical connection on one side of the pin. Try scraping the pin with a hobby knife, or sandpaper, and try the continuity test again.
How likely would VZCDT be outside 0.7V in an L6564 chip? - Page 1
Forum section: electronics / beginners

author: ocset
author_rank: Super Contributor
timestamp: June 23, 2019, 02:29:32 pm
content: Hi,On page 11 of L6564 datasheet is paramerter V(ZCDT) ("triggering voltage")Do you know how likely the 0.5v or 0.9v parts would be to occur in any batch?L6564 datasheethttps://www.st.com/resource/en/datasheet/l6564.pdf
How long does it actually take to ship to USA if purchasing from EEV Store? - Page 1
Forum section: electronics / beginners

author: abiss221
author_rank: Newbie
timestamp: March 26, 2025, 08:51:03 pm
content: Once I decide between the BM2257 and BM786, I then need to buy them. The lower price on the EEVBlog store is truly appealing but I've read in some places the wait could be 8.5 weeks or longer.Has anyone ordered recently from the store in the USA? And if so, how long did it take? Is there any way to possibly even pay for air shipping? I assume it's by sea since the one guy said 8.5weeks.Also, any tips regarding 2257 vs 786 are very welcome as I don't see any comparisons anywhere since the 2257 is so new. I do like the orange backlight on the new one. Also, what is the serial connection used for, I assume the 786 does not have this.I am trying to decide between the BM2257 and the BM789. I would like this to be my everything meter, but it's probably too expensive for that.

author: ahsrabrifat
author_rank: Regular Contributor
timestamp: March 27, 2025, 12:50:34 pm
content: What about the pricing? Do both multimeters fall within your budget?

author: BillyO
author_rank: Super Contributor
timestamp: March 29, 2025, 02:25:49 am
content: It wasn't recently, but when I ordered my BM786 it took less than 2 weeks to make it to Canada. Has something gone awfully wrong in the last 3 years?