hybridfree/eevblog-posts huggingface dataset:
Is it OK to leave the base of an optocoupler open circuit? - Page 1
Forum section: electronics / beginners

author: merlinb
author_rank: Contributor
timestamp: June 03, 2020, 08:42:07 am
content: With a lot of optocouplers* all three pins of the photo transistor are available. I presume this is so you can pad-down the current-transfer ratio if you need to. But if you want maximum CTR, is it OK to leave the base pin open circuit? Or can bad things happen that way?*e.g.https://www.vishay.com/docs/83606/cny17.pdf

author: Labrat101
author_rank: Unknown
timestamp: June 03, 2020, 01:55:00 pm
content: Hi have repaired quite a few power boards with these optocouplers and the spare pin has been leftfloating so far they have not failed . .There should not be any problem leaving it floating as long as itnot close to high noise source . but even then it would take a lot to make it false trigger .Its a NPN output depending on the opto . if you are designing a circuit youcould make use of the C & E . Base Floating is Fine . and should not cause problems .Or use it as a NPN to switch low current ...RNS

author: David Hess
author_rank: Super Contributor
timestamp: June 03, 2020, 03:27:13 pm
content: The base can be left open unless there is some problem with leakage or EMI in which case the base connection might be guarded by the emitter but I have never seen that be necessary. Sometimes I have seen the base connected to the emitter with a series RC circuit which limits bandwidth but optocouplers are pretty slow anyway.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 03, 2020, 04:39:17 pm
content: Yes it is normally left open, this is how the CTR is measured unless otherwise specified.The main use is to add a B-E resistor, typically 47-100k, to speed up turn-off. Switching speeds under 10us can be achieved this way. However, CTR is significantly reduced.There are niche uses where the base can be driven, say for creating a logic function, or used for feedback like in a transimpedance amplifier:(which achieves an analog bandwidth around 600kHz as shown). I've yet to see either application in a product.The pin does indeed invite capacitive coupling; this isn't usually a problem for phototransistor outputs, as the amount of charge injection needs to be relatively large to have much effect; however for hybrid photodiode types like 6N136, it's terrible (with manufacturers often cheating the dV/dt spec by using such a low common-mode voltage step that it doesn't matter). 6N136 should not be used in noisy environments, and 6N138, SFH6345 and others are excellent substitutes.Tim

author: merlinb
author_rank: Contributor
timestamp: June 10, 2020, 07:56:40 am
content: Thanks everyone!
Is it OK to put 0603 resistor on the 0402 pads? - Page 1
Forum section: electronics / beginners

author: Iron Downey
author_rank: Contributor
timestamp: May 16, 2016, 09:57:45 am
content: I made a mistake for the package of the resistor. The pads on the board is 0402, I bought 0603 and I have assembled 1 piece now. See the attached picture. It looks fine, but I'm a little wonder if it would have some bad effects?

author: nour
author_rank: Frequent Contributor
timestamp: May 16, 2016, 10:22:23 am
content: That looks perfectly fine to me

author: Psi
author_rank: Super Contributor
timestamp: May 16, 2016, 10:28:41 am
content: It will work fine for one-off stuff

author: m98
author_rank: Frequent Contributor
timestamp: May 16, 2016, 12:25:34 pm
content: Wouldn't expect any problems.

author: Neilm
author_rank: Super Contributor
timestamp: May 16, 2016, 06:49:28 pm
content: About the only problem I can think of is that it will work fine - but if you build one with the smaller resistor you find that one of the parts is out of specification - most likely dissipating too much heat. What you have here will be OK, but when you make one with the small component remember to check none of them are getting too hot.

author: Iron Downey
author_rank: Contributor
timestamp: May 17, 2016, 07:52:15 am
content: The boards work fine, just not in good look. I have accpeted it O0
Is it okay for a fuse to go on the neutral lead of a AC circuit? - Page 1
Forum section: electronics / beginners

author: Pagweb
author_rank: Newbie
timestamp: March 03, 2013, 08:17:37 pm
content: Hello everyone,Today I built a my first project that uses mains powers. It's a simple AC transformer that steps down 120v to 12v. Here is a picture:As you can see, it has a load switch and an led indicating it's status. Now, after reviewing the design, I realized that I wire the fuse in series with the negative terminal of the transformer, not the positive like that datasheet of the transformer says. My question is: does it really matter? Shouldn't the circuit break weather the fuse is on the negative or positive end?Thanks in advance.

author: hlavac
author_rank: Frequent Contributor
timestamp: March 03, 2013, 08:46:33 pm
content: Transformers do not have positive or negative terminals.If you are talking about mains power "live" and "neutral", it only matters if there are exposed metal parts and your device uses earthed socket that can not be plugged in reverse.In that case the fuse is required to cut off the "live" side of the mains power.Your design looks like it uses double isolation and the fuse is just for protection of transformer from short circuit so in that case it does not matter on which primary winding terminal it is connected.

author: grumpydoc
author_rank: Super Contributor
timestamp: March 03, 2013, 08:54:26 pm
content: AC doesn't have "negative".If you put the fuse on the mains side of the transformer and mean "neutral" then this is dangerous - if there is a fault which causes excessive mains current to flow the fuse will blow but the circuit is left "live" which might catch someone out when fault finding. Also if there is a live-to-earth short inside your equipment the fuse might not blow at all which could be a fire risk.If you mean the low voltage side between the transformer and bridge rectifier then it doesn't matter - except that isn't the best place to put the fuse because the filter capacitors will still discharge into the load.If you really mean the negative line (i.e on the DC side between the common and the negative output terminal) then it depends a little whether the negative is grounded. If it is then it's not all that good an idea because the ground connection is broken should the fuse blow. If the output is floating (i.e not connected to ground) then it doesn't actually matter all that much but the convention is to put any fuse on the positive side.Usually fuses are placed on the "hot" line in AC circuits and in the positive line in DC circuits. It's worth following that convention if only to avoid violating the "law of least surprise".

author: Tepe
author_rank: Frequent Contributor
timestamp: March 03, 2013, 11:40:11 pm
content: Quote from: hlavac on March 03, 2013, 08:46:33 pmIn this country, most sockets have no ground and while live is supposed to be to the left and neutral to the right, the plugs have no indication and can be inserted either way. So no matter where the fuse is put, there is 50% chance it will be on the neutral side. Luckily, RCDs are mandatory.
Is it okay to mix and match fluxes? - Page 1
Forum section: electronics / beginners

author: nshoo
author_rank: Newbie
timestamp: July 03, 2020, 08:21:07 pm
content: I'm getting into the hardware side of electronics and recently bought a roll of solder (I've decided to go lead-free, specifically Kester 24-9574-7618). What I didn't realize is that instead of having a rosin core like I thought, the solder actually contains Kester 275 no-clean flux. I'm looking to buy a flux pen, and before I found this out I had settled on the RMA kind, but I've seen some people suggest that different types of flux are incompatible. All my googling so far hasn't resulted in a clear consensus. So, is this something I should worry about or should I go ahead and get the rosin flux? (P.S. if you've got any other tips or experience to share I'd be glad to hear it!)

author: jpanhalt
author_rank: Super Contributor
timestamp: July 03, 2020, 09:03:23 pm
content: The TDS,MSDS, or SDS (all versions of datasheets) may have the information you need. Some early "no clean" fluxes were just diluted RMA.You will probably notice isopropyl alcohol (IPA) in some and not others. IPA is a good solvent for rosin. So I would expect a rosin core solder to be compatible with a flux pen that was rosin + IPA. When you go to organic or water soluble, then I would expect to see some incompatibilities.

author: wraper
author_rank: Unknown
timestamp: July 03, 2020, 09:10:31 pm
content: Kester 275 has ROL0 classification. So it's rosin based with low activation.

author: nshoo
author_rank: Newbie
timestamp: July 06, 2020, 05:41:33 pm
content: Thanks for the replies, the datasheet turned out to be very helpful! The no-clean flux I had my eye on is apparently incompatible (it's the organic kind), so thank you!

author: wraper
author_rank: Unknown
timestamp: July 06, 2020, 06:56:41 pm
content: Quote from: nshoo on July 06, 2020, 05:41:33 pmLOL what? Kester 275 is hydrogenated rosin (organic) with light activation. RMA is rosin based as well and of course is organic too.

author: jpanhalt
author_rank: Super Contributor
timestamp: July 06, 2020, 07:23:46 pm
content: Agree. I think the 3 main classes are:1) Organic, rosin based (rosin is a weak acid), not water soluble2) Organic, organic acid based, water soluble (NB: One brand I checked only listed "urea" as a component. Most people would not consider urea an acid, but it is very polar and water soluble.)3) Inorganic, water solubleBe aware of "salt" without a specification and hydrochloride. The latter always has halogen; the former may unless it says halogen free.
Is it okay to use sharpie on PCB? - Page 1
Forum section: electronics / beginners

author: ianriley0
author_rank: Newbie
timestamp: August 29, 2016, 03:53:19 pm
content: Simply Put: Sometimes, coworkers and I will use sharpie to write on conformally-coated PCBs as notes to each other, with short notes such as firmware version. Am I correct in thinking that the conformal coating is enough that this isn't damaging the PCB?Followup: What about writing on non-coated FR4?

author: tszaboo
author_rank: Super Contributor
timestamp: August 29, 2016, 04:10:08 pm
content: Yes, you can write with alcohol based pens on PCBs. Just make sure it has soldermask where you write. I dont think anyone will say "oh noes, it will ruin the flammability" or conductivity.

author: Ian.M
author_rank: Super Contributor
timestamp: August 29, 2016, 04:49:31 pm
content: You'd want to avoid metallic pigment inks and any black inks containing carbon, UNLESS there is a dedicated area to write on with no signal tracks. If you are laying out a PCB that you expect to hand-annotate, provide rectangles of white silkscreen to write on either over the groundplane or bare PCB.Totally bare FR4 (no coper, soldermask or silkscreen) can be lightly sanded to roughen the surface and marked in pencil, and also erased. However you need to be careful to avoid conductive graphite dust getting where you don't want it.

author: Fsck
author_rank: Super Contributor
timestamp: August 29, 2016, 06:05:29 pm
content: it's fine, but I would tack a sticker on it (solder mask) to write on. those little colored dot stickers are pretty commonly used.

author: Simon
author_rank: Unknown
timestamp: August 29, 2016, 06:17:47 pm
content: I write on conformally coated PCB's and non. the ones we have at work do have a space for this. Note that if you write first them coat the ink will disolve and you won't be able to see what you wrote.

author: LabSpokane
author_rank: Super Contributor
timestamp: August 29, 2016, 10:35:36 pm
content: A sharpie directly on the PCB /FR4 is fine. I put white rectangles on mine to write the firmware rev. I've never seen a silkscreen dissolve due to alcohol. Most silkscreen is epoxy based these days and does not dissolve readily with alcohol-based solvents.Obviously you don't want to write across sensitive traces, or connect pads together with ink, such as the front end of an instrumentation amp, but a little common sense goes a long way.Also, QC (rubber) stamps have been applied directly onto FR4 for many decades now.

author: tooki
author_rank: Super Contributor
timestamp: August 30, 2016, 09:51:50 am
content: I think he meant that Sharpie ink would dissolve in alcohol (which I can absolutely confirm is true).Nobody was talking about silkscreens.

author: ianriley0
author_rank: Newbie
timestamp: August 30, 2016, 08:06:24 pm
content: Quote from: tooki on August 30, 2016, 09:51:50 amI was actually talking about the conformal coating- just wanted to make sure that my understanding was correct and that there was no damage being done.That being said, I think I will invest in a handheld labelmaker, since some of the areas can be hard to write small enough onThanks All!
Is it permissible... - Page 1
Forum section: electronics / beginners

author: metrologist
author_rank: Super Contributor
timestamp: November 17, 2017, 08:34:23 pm
content: ...to build my dps power supply converter and brick source into a wooden box? I would use aluminum sheet metal for the front and rear panels.

author: floobydust
author_rank: Super Contributor
timestamp: November 17, 2017, 09:19:23 pm
content: Sure, I think a few aspects to consider:Fire safety asks for nothing combustible (wood) in contact with parts that can get hot.The DPS can fail and spit some sparks, surely add a fuse somewhere, but have some clearance between the PCB and wood.If you're charging a battery overnight, unattended, you don't want a campfire.I suggest ventilation for the brick and DPS, not a closed box.You'll have to decide if you want a (DPS) floating output or earth-ground connection.If your brick is ungrounded (2-prong) then stray voltage which can damage semiconductors and equipment you are powering from the PSU.I am talking about Y-capacitor leakage currents in the brick. You can measure ACV from earth-ground to brick output (-) and see if this is a problem.Main problem I encounter with the DPS is EMI is higher than analog power supplies. I add a CM choke and two Y-caps to earth ground, after the output.I'm thinking of you using the power supply for "quiet" work.

author: metrologist
author_rank: Super Contributor
timestamp: November 20, 2017, 03:50:07 pm
content: I had a better idea...Since I had some shallow C-channel aluminum [, I notched a couple of V's in the lips so I could bend it to the same size as my switching PS brick. I screwed that frame and the converter to the top of the PS brick, and mounted the LCD, a switch, binding posts, and a 3-prong line filtering receptacle. (I did not have enough room to mount a third earth binding post, but the PS will be earth grounded)Now all I have to do is remember NOT to connect the mains to the converter (since they are pointed right at that board).It seems like it will be a decent package.

author: metrologist
author_rank: Super Contributor
timestamp: November 21, 2017, 08:28:04 pm
content: So, about my Chinese brick supply, here is the configuration I have.I think I should use my DMM and measure AC voltage and current on its output terminals:+ to earth- to earthThen just AC voltage between terminals.I'll look up Dave's video on the topic, but would you expect to have to do anything other than just wire it up? The chassis will be earth grounded at the supply mains input.The supply has active, thermal controlled cooling with a fan on the bottom, so I will add some feet, and I may add some washers between the cover for a small gap at the top, or I may add some slots in the side and top.
Is it possible  -15V/2A  with MC33063? - Page 1
Forum section: electronics / beginners

author: endorfin35+
author_rank: Newbie
timestamp: November 25, 2023, 02:51:29 pm
content: Hi everyone,I'm not experienced in this matter. I want to generate -15V from +24V. I prepared the drawing attached. I'd like to hear your ideas.

author: Terry Bites
author_rank: Super Contributor
timestamp: November 25, 2023, 05:14:51 pm
content: Yes.You can make an inverting buck converter. See 9.2.1 and 8.2.1.2 in the datasheet.www.ti.com/lit/gpn/mc33063aThe calculations are simple but a bit tiedious. My advice, do the calculations in excel or other spreadsheet so you can tweak your design.Or....https://observablehq.com/@sharow/mc34063-inverting-conveter-calculatorThe mc34063 is essentially the same as the mc33063, the only difference is an improved operating temperature range.I asked our robot overloards gptchat: "Design an inverting buck converter with an MC33063. 24 volts input, -15 volts output"Reply...https://chat.openai.com/share/9bb4bb18-c3e0-4b2a-b7c3-25e9f767c509MFSOAB

author: endorfin35+
author_rank: Newbie
timestamp: November 25, 2023, 06:40:49 pm
content: The calculator was very useful. Thanks for this.The thing that caught my attention is that for 2A current, 7.6A peak current occurs. That's a pretty high value.On the board referenced, I see only one integrated circuit, one diode and one inductor for this task. It is not clear what the ic is. However, its structure looks simple.
is it possible? controlling MC34063 digitally? - Page 1
Forum section: electronics / beginners

author: ali6x944
author_rank: Frequent Contributor
timestamp: February 07, 2016, 06:19:24 pm
content: is it possible to control the MC34063 digitally with out losing efficiency?

author: Jeroen3
author_rank: Super Contributor
timestamp: February 07, 2016, 06:31:53 pm
content: You can use a digital pot in the sense divider feedback. Or inject current into the divider using a dac and an opamp.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 08, 2016, 06:39:37 am
content: If you have any kind of digital control, you can literally do better by using it directly as PWM.MC34063 sucksthat much.Tim
Is it possible to cut down an ESD mat to a more suitable size? - Page 1
Forum section: electronics / beginners

author: Specmaster
author_rank: Super Contributor
timestamp: June 07, 2018, 10:56:09 am
content: Hi I have a 3m ESD mat but my bench is only 1.3m, in essence its an old office desk, could I effectively cut the 3m mat down in size to make fit my bench top or would that risk effecting the effectiveness of the remaining mat at all?

author: OE2WHP
author_rank: Regular Contributor
timestamp: June 07, 2018, 01:22:37 pm
content: You can cut your mat to whatever size you need, without influencing the function. Just make sure that the mat is still connected to mains earth after cutting. ;-)

author: Specmaster
author_rank: Super Contributor
timestamp: June 07, 2018, 07:23:06 pm
content: Thanks, you just confirmed what I thought, thanks.
is it possible to damage Ethernet NIC with RS-232 signal - Page 1
Forum section: electronics / beginners

author: m4rtin
author_rank: Regular Contributor
timestamp: September 28, 2015, 08:27:58 pm
content: Let's say that I connect aDE-9 <-> RJ45 cablein a way that DE-9 connector is connested to (Cisco) network device serial(RS-232) port and RJ45 connector is connected to laptop NIC port. This should mean that laptop NIC might receive +3V to +15V or -3V to -15V signals on some pins while normal Ethernet on physical layer is between -2.5V to +2.5V. Is there a risk to damage NIC with 6 times higher voltage than nominal? Is it possible to damage serial port? Has anyone done that in practice?

author: bitslice
author_rank: Frequent Contributor
timestamp: September 28, 2015, 09:34:27 pm
content: Ah, silly Cisco and their RJ-45 console port,ethernet signals go via a transformer before they get near the electronics, so it will be OK (AFAIK)

author: amyk
author_rank: Super Contributor
timestamp: September 28, 2015, 11:58:33 pm
content: Quote from: bitslice on September 28, 2015, 09:34:27 pmYes there's a transformer (the "magnetics") but too much current will burn it out. Of course this is entirely dependent on how it's wired, as you may end up with the voltage harmlessly between two of the pairs (which is essentially what PoE does).

author: Kleinstein
author_rank: Super Contributor
timestamp: September 29, 2015, 04:43:51 pm
content: RS232 outputs are current limited (at least they should be if by the standard, and all chips a know do limit the current). This way the RS232 is protected from shorts too. The current is likely not enough to damage the ethernet input transformer. Also input impedance on ethernet is much lower, so there will not be a high voltage.So normaly there should not be any damage, but I have noch tested or in detail looked at the ethernet specs.

author: suicidaleggroll
author_rank: Super Contributor
timestamp: September 29, 2015, 05:39:46 pm
content: I agree that it should be alright. The RS232 spec dictates that outputs should be able to drive into a short indefinitely, so that side should be fine, and the current limit on RS232 should be low enough to not damage the transformer on the RJ45 side, assuming the cable was even wired to pump current through one of the pairs.

author: Cliff Matthews
author_rank: Unknown
timestamp: September 29, 2015, 08:27:50 pm
content: The only damage to Ethernet I've seen In 30+ years of IT from Buss-tag to Racal-Milgo sync modems to working at Gandalf-Infotron and Intel-Dialogic, is by lightning. The interface is magnetically coupled and often potted - it used to look like a fat IC chipNow many of the magnetics are hidden inside deep RJ-45 jacksLiitlefuse has quite a few good referenceshttp://www.littelfuse.com/~/media/electronics/design_guides/esd/littelfuse_ethernet_protection_design_guide.pdf.pdf
Is it possible to hook up an ATX PSU and an Xbox 203W PSU in series - Page 1
Forum section: electronics / beginners

author: AnonymousChen
author_rank: Newbie
timestamp: May 12, 2013, 09:53:16 am
content: Hey there is it possible to hook up an dual rail ATX PSU +12v1 22A +12V2 20A with a 203W Xbox PSU 12V 17A in series to get 24V for a 3D printer

author: amyk
author_rank: Super Contributor
timestamp: May 12, 2013, 10:31:40 am
content: The ATX PSU will be ground-referenced, not sure about the Xbox one but if it is then you can't.

author: AnonymousChen
author_rank: Newbie
timestamp: May 12, 2013, 10:59:45 am
content: Do you mean ground referenced as in the mains have ground and BTW the Xbox PSU has no ground on mains but the ATX PSU does

author: gxti
author_rank: Frequent Contributor
timestamp: May 12, 2013, 01:33:42 pm
content: Then it will be fine. I know in the US at least, xbox PSUs do not have an earth pin, so they must float.
Is it possible to identify an SMD Capacitor or other component on a motherboard  - Page 1
Forum section: electronics / beginners

author: HelloBug
author_rank: Newbie
timestamp: April 17, 2019, 09:06:46 pm
content: I was trying to fix a laptop motherboard. I don't have the schematic for it.I needed to replace some smd components that were corroded, like a capacitor.They are the standard smd type components you would see with no markings, like the smd capacitors in the image linked to below.http://www.capacitorlab.com/capacitor-types-ceramic-smt/ceramic.jpgIs it possible to repair and replace smd components like those capacitors without a Schematic or donor board?I would hate to throw away a potentially fixable laptop, but I just don't know what to replace any of the components with.

author: wraper
author_rank: Unknown
timestamp: April 17, 2019, 09:19:22 pm
content: You cannot identify SMD ceramic capacitors by their looks. If there are still some terminal plating left, you could measure capacitance. Voltage rating would be selected according to place it's used at or just go to max available voltage rating for the size. If cap is completely destroyed, you could try looking for similarly looking cap, preferably sitting on the same power rail and measure that.But I don't think that is the main problem. If there is corrosion somewhere under BGA, you won't be able to fix that without special equipment.

author: HelloBug
author_rank: Newbie
timestamp: April 17, 2019, 09:27:33 pm
content: So you think I should find a similar looking capacitor on the same power rail, remove it and then measure the capacitance?

author: wraper
author_rank: Unknown
timestamp: April 17, 2019, 10:09:27 pm
content: Quote from: HelloBug on April 17, 2019, 09:27:33 pmyes

author: james_s
author_rank: Super Contributor
timestamp: April 18, 2019, 12:33:46 am
content: You could also guess based on what it does. If it's decoupling on a power rail then 100n is a reasonable guess. If it's physically bulky then it may be as large as 10u.

author: JustMeHere
author_rank: Frequent Contributor
timestamp: April 18, 2019, 12:55:36 am
content: You could look at the component the cap is near. Then check the data sheet. For example, if the cap is for a power regulator, the datasheet for the power regulator would be a good place to start.
Is it possible to import a PCB pattern into an EDA to replicate PCB? - Page 1
Forum section: electronics / beginners

author: SeamlessPurse
author_rank: Newbie
timestamp: December 29, 2021, 10:29:20 am
content: HiSilicon chip magazine provides pdf PCB patterns for their projects. For example:https://www.siliconchip.com.au/Shop/10/6063(there's a link to download for free).I've never used an EDA however can the PCB pattern be uploaded and used as the layout. I have the relevant issue with schematic and silkscreen.I'm not looking to sell or plagarise I simply don't etch PCBs anymore.

author: NorthernWing
author_rank: Contributor
timestamp: December 29, 2021, 04:04:38 pm
content: I wouldn't really call it a typical feature, but sure there are ways to make it work. I don't know about any other packages since I don't use them, but DipTrace has the ability to import a bitmap image as an object and use it as any layer (copper, silk, mask, etc). You'll have to convert/print that PDF as a PNG or BMP first though before you can do anything with it.It's a bit wonky because the program vectorizes imported images into a huge pile of separate objects, but you just need to right click andGroup->As Componentand it takes care of it.Nope, they fixed that since the last time I used this feature.EDIT: I'll give it a try since I have DipTrace already pulled up here...give me a sec...- Yep, still works, but you'll have to manually replace all of the through-hole drills/etc since all you've got are the top and bottom copper layers.Dave did a video on DipTrace a long time ago now, but I really wish he'd revisit it over on the channel; it's completely unrecognizable since that video and has gotten so many new features/fixes that I wouldn't even call it the same product anymore.
Is it possible to modify cartridge soldering iron to be used on 5 core station? - Page 1
Forum section: electronics / beginners

author: khtwo2002
author_rank: Contributor
timestamp: January 12, 2016, 09:09:47 pm
content: As far as I know, a important parameter of solder iron is its react to the thermo change on it's tip. Cartridge style solder iron has its advantage by nature. Is it possible to modify such cartridge style solder handle from good brand to be used with some cheap solder stations, such as 898D+? Those solder stations has 5 core cable port for iron handle. Anyone have some experiences?

author: KL27x
author_rank: Super Contributor
timestamp: January 13, 2016, 04:49:13 am
content: Other than a relative dearth of cheap cartridge-tip knockoff handpieces, sure why not?

author: khtwo2002
author_rank: Contributor
timestamp: January 13, 2016, 02:33:29 pm
content: Quote from: KL27x on January 13, 2016, 04:49:13 amThere are quite some such handle or diy cartridge handle on ebay at below $18. The thing I'm not sure is the pinout of the 7 pin cable and 5 pin cable. What voltage they use. Can the cheap station handle the cartridge thermo sensor? Where can I find such information?
is it possible to parallel mosfets in the zvs circuit and how  - Page 1
Forum section: electronics / beginners

author: DarkZero
author_rank: Regular Contributor
timestamp: December 16, 2015, 07:31:52 pm
content: hello all !i tried to parallel mosfets and on the out-put i get one swing of the sine to be a lot lower and some weird shape and its random on every turn on while with just 2 mosfets i get nice sine wave. any can help me understand mosfet paralleling.http://uzzors2k.4hv.org/projectfiles/flybacktransformerdrivers/Mazzilli%20ZVS%20Flyback%20Driver.png
Is it possible to phase shift a signal to make use of multiple scope channels? - Page 1
Forum section: electronics / beginners

author: lscw
author_rank: Contributor
timestamp: June 28, 2020, 02:37:41 am
content: I'm probably missing out technical terms that better describe what I'm trying to say but here goes:Is there a reliable way/is it even possible to utilise two or more oscilloscope channels (assuming max sample rate/ch remains the same), each phase shifted appropriately to increase the total sample rate of a signal?I'm picturing in my head a 2 channel 1Gs/s/channel scope sampling a single signal at 1Gs/s on channels 1 and 2, with a 1ns delay on the signal input to channel 2 and the waveforms overlayed on the display. I guess interpolation might get in the way but is there any other reason it couldn't work?

author: elektrolitr
author_rank: Contributor
timestamp: June 28, 2020, 03:40:33 am
content: This is already implemented in many lower-end scopes, when you either have for example 1GSa/s if you use only one channel or 500MSa/s for each if you use both

author: filssavi
author_rank: Frequent Contributor
timestamp: June 28, 2020, 06:28:01 am
content: What you want is a scope with multiple timebases, while this was fairly common in the old analog dual channel CROs; I don’t know of any modern digital scope (up to midrange such as lecroy hdo8000 or tektronix MSO58) that has it.Usually with modern scopes you just capture the first waveform once, store it as a reference and then trigger on the second one, that you can delay as much as needed with regular time base control

author: Kleinstein
author_rank: Super Contributor
timestamp: June 28, 2020, 07:16:14 am
content: Combining 2 (or more) ADCs to get a higher sampling rate is a common practice in DSOs, also at the high end. One usually does the delay / phase shift with the ADC clock and not the signal itself. For times in the low ns range,it only takes a piece of PCB trace to get a delay.Doing this externally is tricky, as high frequency signals need a defined load / line impedance. So already splitting the signal in 2 takes more than a BNC T.

author: magic
author_rank: Super Contributor
timestamp: June 28, 2020, 08:45:24 am
content: Quote from: lscw on June 28, 2020, 02:37:41 amI suppose you could, with some preamp/buffer/splitter according to circumstances and a pair of coax cables of different length.It will make no difference because 1GS/s presumably means "an entry level DSO" and entry level DSOs are limited to a few hundred MHz by their analog preamps, not the ADCs.And you probably meant 0.5ns delay, not 1ns. The latter is completely pointless.

author: bdunham7
author_rank: Super Contributor
timestamp: June 28, 2020, 04:27:14 pm
content: https://www.analog.com/en/analog-dialogue/articles/interleaving-adcs.html

author: lscw
author_rank: Contributor
timestamp: June 29, 2020, 11:36:58 pm
content: Thanks very much for all the replies. They answered my question directly, and the Analog Devices article make for interesting reading
Is it possible to solder small BGA(flip chip) at home? - Page 1
Forum section: electronics / beginners

author: TNb
author_rank: Regular Contributor
timestamp: November 21, 2016, 02:55:19 am
content: Is it possible to solder something likeSTM EMFI02at home? Assuming I can screw up several times before I get it of course.While bigger BGA packages can be soldered manually(like Louis shows below), this is flip chip and damn small one, so I suspect it is more touchy about temperature profile, positioning etc.Should I even consider to buy it and try to solder with hands or better forget about it and find more suitable package IC?And while we're at it - maybe somebody knows good and simple ESD usb protection IC like EMFI02?

author: TNb
author_rank: Regular Contributor
timestamp: November 21, 2016, 04:53:25 am
content: Thanks! Maybe I'll find better IC, for now I haven't seen good one, usually they are either too complex with MUXes inside and other additional crap or I can use separate TVS diodes... but yeah, propably there is better IC, but nevertheless it would be interesting to try solder this puppy by hand, so I might as well buy couple of themP.S. If somebody wonders about topic of using BGAs in their design - routing them is pain in the ass, requires multi-layer board and manufacturer that can handle small pitch traces, so even if it is possible to solder - probably throw this idea away for small hobby prototypes.However(!) you can be lucky like me and you need just outer pins of BGA, so you route it as QFN package basically

author: plazma
author_rank: Frequent Contributor
timestamp: November 21, 2016, 06:13:30 am
content: Hot air works with BGA. Pre-tin or order HASL PCBs. No need for solder paste. The BGA ball alone is enough. Apply flux to PCB before placing the chip.Solder paste does help a little bit. Especially if the PCB is not pretinned or without HASL. I have access to a very good dispenser at work. I have used it for 100+ pin BGA chips.
Is it possible to use a continuity tester here? - Page 1
Forum section: electronics / beginners

author: Bondguy
author_rank: Contributor
timestamp: March 23, 2017, 08:43:00 pm
content: Is it possible to use a continuity( short circuit) tester to test a microchip such as ATMEL IC for a short circuit?Or is there any danger that by using continuity( short circuit) tester I can destroy the microchip if that had been working well?( the tester uses a voltage and I am not sure that voltage can not destroy any transistor (or a similar ) inside )My idea is to compare GND pin with other pins and if the chip is shorted , there will an indication of a beep.Is it workable or not?

author: not1xor1
author_rank: Frequent Contributor
timestamp: March 24, 2017, 06:58:33 am
content: Quote from: Bondguy on March 23, 2017, 08:43:00 pmyou can't trust your multimeter continuity function for that purposethe circuit below might work as it will beep when the resistance is very low (even few milliohms if you set the trimmer for that) and the test current is less than 200µAthe resistors with (*) are 1% and the buzzer I used is just a transducer so the second opamp works as a square wave oscillator.PTC and diodes are input protection (in case of charged capacitor or live circuit test)the led won't turn on when the battery is low

author: Gyro
author_rank: Super Contributor
timestamp: March 24, 2017, 09:30:20 am
content: I've long been intrigued by the 'Ultimate continuity tester' published in Electronic Design. It can even distinguish shorts from inductors, transformer windings and reverse connected windings....http://electronicdesign.com/analog/ultimate-continuity-tester-hides-many-tricks-its-sleeve

author: james_s
author_rank: Super Contributor
timestamp: March 24, 2017, 09:10:45 pm
content: That's pretty clever.I've occasionally used my ESR meter to check for shorted semiconductors. The high frequency makes inductors appear as much higher impedance, the voltage is too low to forward bias semiconductors. Capacitors will of course fool it and look like a short if it's a good low-ESR capacitor but even so a short will usually appear lower impedance than even a good capacitor.

author: freda
author_rank: Regular Contributor
timestamp: November 23, 2021, 12:19:52 am
content: Quote from: Gyro on March 24, 2017, 09:30:20 amThe circuit figures in the article are blank now (for me)

author: ledtester
author_rank: Super Contributor
timestamp: November 23, 2021, 10:53:06 am
content: Found it!There is a caveat that the circuit might not work as expected.http://kripton2035.free.fr/Continuity%20Meters/ed-ultimateconti.html(also saved to web.archive.org)Update: Also archived here:https://www.eevblog.com/forum/oshw/continuity-tester-with-glitch-capture/msg2250480/#msg2250480See also this forum post:http://www.8052mcu.com/forumchat/read/190943

author: Gyro
author_rank: Super Contributor
timestamp: November 23, 2021, 10:02:36 pm
content: Quote from: freda on November 23, 2021, 12:19:52 amThis is the one I really trust to work though...https://www.eevblog.com/forum/projects/continuity-tester-circuit/msg2652777/#msg2652777
Is it possible to use USB-C audio along with USB D+/D- lines? - Page 1
Forum section: electronics / beginners

author: Marmotta
author_rank: Contributor
timestamp: June 08, 2020, 09:00:00 pm
content: I was hoping to somehow use an adapter like the one attached below on a project of mine to split some signals (GND, 3.3V and Data via the 3.5mm jack; USB D+/D-, 5V, GND on the passthrough USB-C cable). I assume any such cable would be configured for USB-C Audio Adapter Accessory Mode, but (1) my device wouldn't have any CC detection hardware and (2) D+ and D- are sent to the 3.5mm jack rather than the USB-C passthrough connector.Is there any way to work around this or, failing that, any ideas on any other types of connectors I could break out to USB 2.0 and a separate three-pin socket without having to build my own breakout connector, which is the one thing I'm really trying to avoid.

author: ö
author_rank: Newbie
timestamp: June 09, 2020, 07:07:29 am
content: I guess you would have to use USB Audio connected to a hub or Bluetooth audio to achieve that. Could you explain your idea in more detail?

author: Renate
author_rank: Super Contributor
timestamp: June 09, 2020, 12:44:02 pm
content: The Type C socket on that breakout cable is only for charging.With that plugged in there is no digital data of any kind going anywhere.You only have a TRRS analog jack.
Is it possible to write protect a CF card by hardware?  - Page 1
Forum section: electronics / beginners

author: sam1275
author_rank: Frequent Contributor
timestamp: April 18, 2015, 03:09:12 pm
content: Hi everyone.Is it possible to write protect a CF card by hardware? Just like block pin23 (write signal) on IDEs, Is there any similar thing to completely block any writes on CF card? Some CF cards have write protection switch, is that reliable? Or just a dummy thing like SD cards.Thank you.

author: Grapsus
author_rank: Regular Contributor
timestamp: April 18, 2015, 03:44:08 pm
content: The write signal is for writing an ATA command to the drive, it does not necessarily mean that data will be written on the disk. Hardware write blockers exist, they are used in forensics, but they're more complex than just blocking one pin, they need to understand the higher level protocol in order to refuse actual write commands.

author: Fraser
author_rank: Super Contributor
timestamp: April 18, 2015, 04:05:51 pm
content: +1 on forensic write blocks.Encase use such.They are expensive but essential in legal forensicsAurora

author: sam1275
author_rank: Frequent Contributor
timestamp: April 18, 2015, 04:13:39 pm
content: Thank you guys!So the block pin method even doesn't work on IDE?What about the switch on the industrial CF card? Is there a way to bypass it without hardware access, for hackers or virus?

author: Grapsus
author_rank: Regular Contributor
timestamp: April 18, 2015, 05:11:59 pm
content: I think it's very hard to tell in general. There are many ways to implement a write protection in a memory card, it could be at IDE interface level, write access to flash chips could be blocked, etc. Depending on the attacker's level of access, remote administrator or physical access to the card, and the implementation of the protection it could be very easy or very hard to bypass.Most importantly it will be very hard to get any level of warranty outside marketing crap. If what you're trying to protect has legal implications, you may better find an alternative solution like for example using robust cryptography to sign the data on the card instead of relying on the hardware.

author: sam1275
author_rank: Frequent Contributor
timestamp: April 21, 2015, 06:39:02 am
content: Quote from: Grapsus on April 18, 2015, 05:11:59 pmThank you.
Is it possible? Voltage controlled multiplexer? - Page 1
Forum section: electronics / beginners

author: ali6x944
author_rank: Frequent Contributor
timestamp: March 10, 2016, 04:05:45 am
content: Hi everyone,Is it possible to make Voltage controlled multiplexer for a switch mode pawer supply to chose its operating trepology?

author: Alex Trofimov
author_rank: Contributor
timestamp: March 10, 2016, 10:42:15 am
content: Hi! Basically, it seems possibly, but in most cases it's better to use one proper topology, that serves all the needs.To give better answer there's more info needed. Between which topologies would you like to switch? Which IC do you use?

author: tszaboo
author_rank: Super Contributor
timestamp: March 10, 2016, 11:52:08 am
content: Make a resistor string, the input is some reference voltage, like a TL431, divide it down to the with the correct voltage values. Use these voltages with a bunch of comparators. Route the output of the comparator to some logic ICs, and then the output of those to a bunch of analog multiplexer or switch.

author: matseng
author_rank: Frequent Contributor
timestamp: March 10, 2016, 11:56:14 am
content: Th OP wants to change the topology of the smps, not the voltage. If I remember correctly the high current paths needs to be rearranged for different topologies, and that can't be done with an analog mux, but rather nice fets or realys. But that would probably mess up any nice low-inductance routing on the pcb and cause a low efficiency.I guess it would probably be easier to build the different topology-smps modules separately and then just switch between the output DC from the modules....

author: RobK_NL
author_rank: Frequent Contributor
timestamp: March 10, 2016, 12:10:26 pm
content: This type of question is exactly why my sig is what it is ...
Is it required for the external casings of USB to be connected? - Page 1
Forum section: electronics / beginners

author: epigramx
author_rank: Regular Contributor
timestamp: March 08, 2019, 07:31:54 am
content: I noticed a Xiaomi power bank came with that not connected. Most other cables I have have them connected at low resistance. I noticed one had 10 Ohms resistance (!).

author: ataradov
author_rank: Super Contributor
timestamp: March 08, 2019, 08:01:46 am
content: For a power bank it makes no difference.
Is it safe to attach solar charge controller directly with your mains inverter? - Page 1
Forum section: electronics / beginners

author: abhishekkumar1902
author_rank: Regular Contributor
timestamp: July 03, 2017, 01:24:37 pm
content: I see a lot of these solar charge controllers which are marketed to convert your old AC mains based inverter to a solar hybrid charger. If you see the way they should be connected with the battery is in PARALLEL directly with the battery provided the inverter is also connected to the battery. Now I really doubt if the inverter is powered from mains and the solar charger is also parallelly charging the battery, wouldn't there be any backflow of current in the inverter or the solar controller, if their charge state doesn't match with each other or if they both are operating at different voltages? is it a safe way to use it like this way?

author: David Hess
author_rank: Super Contributor
timestamp: July 03, 2017, 05:15:58 pm
content: You are going to need to be more explicit because your diagram shows a charge controller charging a battery and powering an inverter. Most charge controllers will have no trouble doing this.

author: abhishekkumar1902
author_rank: Regular Contributor
timestamp: July 04, 2017, 05:49:26 am
content: So is it quite safe to just directly hook up the solar charger along with the inverter in parallel?

author: David Hess
author_rank: Super Contributor
timestamp: July 04, 2017, 03:36:50 pm
content: Quote from: abhishekkumar1902 on July 04, 2017, 05:49:26 amSure, how else would you keep the batteries charged while providing AC power? Charge controllers which would have a problem with this are in the minority; they will either allow a load to be connected directly to the battery bank or will provide a separate DC output which can be used to power the inverter.Just to be sure, check the charge controller's documentation.
Is it safe to turn on power supply? - Page 1
Forum section: electronics / beginners

author: giosif
author_rank: Frequent Contributor
timestamp: September 07, 2020, 07:38:16 am
content: Hi,I am troubleshooting a Tektronix 2710 spectrum analyzer and I suspect there is a fault in the power supply section.However, the board in question is also responsible for generating the high voltage for the CRT (please see large PCB in the below picture, courtesy of PA4TIM -www.pa4tim.nl).Is it safe (for the power supply itself) to power it while disconnected from the CRT and all other boards in the spectrum analyzer?For my safety, I will take extra-precautions, but I'm mainly interested in the power supply itself, if it is ok to turn on.Thanks!

author: Vovk_Z
author_rank: Super Contributor
timestamp: September 07, 2020, 07:03:16 pm
content: Good question. I don't know a right answer, but I know that there is a non-zero possibility to make things worse, because some power supplies don't like an absence of load.So we definitely have to hear from somebody who knows this device.

author: giosif
author_rank: Frequent Contributor
timestamp: September 07, 2020, 07:28:13 pm
content: Thank you for confirming my concern!Let's see if someone can give us the more definite answer.

author: ledtester
author_rank: Super Contributor
timestamp: September 07, 2020, 07:33:01 pm
content: You might find some info in the service manual.Tektronics service manuals are usually available on-line from tek.com. There are also other sites offering them for free -- e.g.:https://elektrotanya.com/tektronix_2710_spectrum_analyzer_sm.pdf/download.html#dl

author: srb1954
author_rank: Super Contributor
timestamp: September 07, 2020, 10:02:02 pm
content: Join the TekScopes forum on groups.ioThere is a huge wealth of information available from the group members for repairing Tektronix equipment.

author: giosif
author_rank: Frequent Contributor
timestamp: September 07, 2020, 11:08:53 pm
content: Thank you both!I do have the service manual.I've also joined the discussion group and have started a thread on the repair of this unit.Let's see how it goes.
is it still ok to buy a multimeter that lacks a specific range on one function?? - Page 1
Forum section: electronics / beginners

author: doctorm
author_rank: Regular Contributor
timestamp: May 14, 2010, 05:25:30 am
content: so my question involves a common problem i am having in finding the right multimeter i need.the fluke 115, for example, would probably be the perfect multimeter i could get but the amps range is not low enough. it only goes to mamps and no uamps, which is suggested in my books and some projects.with this in mind, do you, in ur suggestion, still get it even though it lacks the range or do you keep on going?just curious. thanks

author: EEVblog
author_rank: Unknown
timestamp: May 14, 2010, 05:34:29 am
content: No, don't bother with the 115, it's only for electricians who don't deal with low level electronics.I've got 5 $100 meters for review coming up, all cost less than the 115 and all provide greater measurement capability.Dave.

author: doctorm
author_rank: Regular Contributor
timestamp: May 14, 2010, 05:37:20 am
content: Quote from: EEVblog on May 14, 2010, 05:34:29 amok thanks. so when are you going to have the multimeter shootout up? im really excited to see it.