hybridfree/eevblog-posts huggingface dataset:
Small LCD Panel emitting lots of EMF - Page 1
Forum section: electronics / beginners

author: testtube44
author_rank: Regular Contributor
timestamp: September 23, 2018, 11:59:58 pm
content: I have a camera, and a synthesizer which both have small LCD screens, and they emit a lot of electromagnetic radiation. A very low (maybe ~20hz), noisy, pulsing ringing sound. Why do small panels like these do this and big screens like my monitor don't emit at all, and is there any way to mitigate this?
Small Package LVDS Transceivers - Page 1
Forum section: electronics / beginners

author: LukeGary
author_rank: Newbie
timestamp: May 22, 2022, 10:47:17 pm
content: Hello, I am currently working through a system level design of some scientific instrumentation. One module of the system will need 4 LVDS signal pairs for communication between a 2Msps acquisition device and a microcontroller over a flax cable, the entire assembly is similar to an ink-jet printer head. The moving component is quite small and I am having some trouble sourcing small 2Tx/2Rx LVDS transceivers to use on the smaller board. I have looked at the MAX9113/MAX9112 combination, as well as the SN65LVDS050, but both of these solutions are a little large given the available board area. What I am wondering is are there any small (3x3mm - 4x4mm) 2/2 transceivers I just haven't found yet, or are there any slick tricks to create an LVDS driver/receiver out of more readily available components given the board area constraint? I have considered using some high-speed comparators, but any that are currently available seem to end up with a larger implementation than the transceiver approach.

author: jwet
author_rank: Frequent Contributor
timestamp: July 15, 2022, 02:56:01 am
content: The 9110/12 and 9111/133 are as small as I've seen- they're offered in a 2x3 TDFN 8 and SOT's . I think these are the tiniest.
Small part storage solutions available domestically in Australia - Page 1
Forum section: electronics / beginners

author: rthorntn
author_rank: Frequent Contributor
timestamp: July 04, 2018, 06:52:10 am
content: Hi Everyone,Thanks for all your help in the past.I can't really find anything suitable for holding lots of small boards and components that isn't crappy or ridiculously expensive.I would want about 400+ little compartments that I could sit on a desk.Nothing too heavy, available domestically by mail order.Budget $400.Thanks for looking.CheersRichard

author: +Mikie
author_rank: Contributor
timestamp: July 19, 2018, 01:26:02 pm
content: I was in a similar situation earlier. It took me a while to realize there is a 3D printer right next to me on my deskMust be getting old. $400 would buy a 3D printer kit and lots of filament to print whatever you wish/need/like. Thingiverse is full of various designs, many of them customizable.Otherwise, Jaycar sells small component drawer sets. If that's not to your liking, only other suggestion is Howard's Storage shops. If they don't have what you want, they should be able to point you in the right direction. Storage is all they do, there must be something in their suppliers' catalogues available to order in even if they don't normally stock it.

author: knapik
author_rank: Regular Contributor
timestamp: July 19, 2018, 01:29:48 pm
content: Hey, this is something that I've been interested in too, and unfortunately, I just haven't been able to find anything. That 3d printer solutions sounds like a good idea, I wonder if I should make some worthwhile investment into one for the future.

author: vk6zgo
author_rank: Super Contributor
timestamp: July 19, 2018, 01:37:40 pm
content: Bunnings, Stratco, Red Dot, maybe Ikea.
small pitch PCB manufacture, cheep and deliering to austria? - Page 1
Forum section: electronics / beginners

author: Trax
author_rank: Regular Contributor
timestamp: September 28, 2014, 03:01:30 pm
content: I'm looking for a PCB manufacture that could make PCB's suitable for small pitch SMD IC's that would be cheep and located in Europe delivering to Austria.CheersTrax

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: September 28, 2014, 03:30:06 pm
content: www.eurocircuits.com

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 28, 2014, 03:54:57 pm
content: What is "small pitch"? Even the cheap Chinese services offer enough precision for 0.5mm pitch devices.Tim

author: jc101
author_rank: Frequent Contributor
timestamp: September 28, 2014, 09:33:47 pm
content: Quote from: mikeselectricstuff on September 28, 2014, 03:30:06 pm+1 had no problems with them
small portable 24V battery supply - Page 1
Forum section: electronics / beginners

author: grymoire
author_rank: Contributor
timestamp: February 22, 2021, 03:25:57 pm
content: I have a coil unit that is designed to light up RFID like LED's, similar to these RFID/NFC Nail stickershttps://www.adafruit.com/product/3781The coil unit comes with an AC to 24V 2A DC adapter. However I want something that isSmallNot connected to ACDoesn't need to provide power for more than 10 minutes. I'm looking for short-term and occasional use.Preferably rechargeablePreferably something that can also supply 3.3V and 5V output as well. I have an Arduino project with multiple 3.3V sensors, and I've read that the project will need an external power supply for the sensors.I was also thinking I could add a relay allowing the Arduino to control the 24V coil.I found a $70 unit on Amazon that has both 24V and 5V outputhttps://www.amazon.com/TalentCell-PB240A1-Rechargeable-22400mAh-82-88Wh/dp/B078T7M9HZBut it is lacking a 3.7V output. I could just add a separate supply for those sensors (with a common ground of course). Or use a separate supply for the Arduino+sensors, if I used a unit that only had 24V output.Is this the right way to go? Is there a cheaper option? I'd hate to waste $70 on a supply that may go bad if I could have something with replaceable 18650 batteries. I found this 5V/3.3V unithttps://www.amazon.com/Diymore-Holders-Lithium-Battery-Charging/dp/B0813G77RT/which seems reasonable for powering the Arduino+sensors. I'm also going to try a gang of 9V batteries to see how long they can power the coil. Any other suggestions?

author: bob91343
author_rank: Super Contributor
timestamp: February 22, 2021, 06:23:26 pm
content: If you have a 5V line you can add a 3.3 V regulator from it and get what you want.

author: ledtester
author_rank: Super Contributor
timestamp: February 23, 2021, 02:56:11 am
content: QuoteI think there is a review of that module in this video:https://youtu.be/-SJbdPvgQnEA lot depends on how much power you need at each voltage -- 3.3, 5 and 24.A standard approach to getting a higher voltage from a lower one is to use a boost converter, something like:https://www.amazon.com/Converter-Voltage-Adjustable-Step-up-Circuit/dp/B07XG323G8But you'll pay for it in efficiency. The youtube channel robojax has a lot of videos testing the efficiency of various boost and buck modules -- e.g.:https://www.youtube.com/c/RobojaxTV/search?query=boost

author: grymoire
author_rank: Contributor
timestamp: February 23, 2021, 05:37:25 pm
content: Thank you! Very helpful.

author: BrokenYugo
author_rank: Super Contributor
timestamp: February 24, 2021, 06:53:37 am
content: Dos this thing actually pull 2 amps at 24V? It would be really good to know that before moving forward.
Small power supply upgrades - Page 1
Forum section: electronics / beginners

author: Doctorsdad
author_rank: Newbie
timestamp: July 02, 2025, 04:16:00 pm
content: Hi,A long time ago, I used to be quite handy but it's been several decades since I picked up a soldering iron and I need to solve a little power supply problem. In the old days I'd have gone to Maplin and now I'm hoping you can point me in the right direction.I have a water feature powered by a 9V/6W solar panel.I'd like to add in a rechargeable battery so that it works when the sun goes in.Can I get off the shelf components to do that?It would be very nice to add in remote switching but that can come later.Regards,Dave. ( Old dog hoping to learn new tricks )

author: thm_w
author_rank: Super Contributor
timestamp: July 02, 2025, 09:43:03 pm
content: Usually these pumps are rated 5-12V. The panels are rated 9V and ~2-3W.If you want to keep it dead simple, the panel can charge a set of maybe 6 series nimh AA cells through a schottky diode.https://www.reuk.co.uk/wordpress/education/basic-4-aa-solar-battery-charger-plans/Though you might want to investigate at what voltage the pump shuts off, and if it still draws power. You probably don't want to completely drain the batteries to nothing, better if it shuts off when the voltage reaches around 5 or 6V.
small power transformer assumptions check - Page 1
Forum section: electronics / beginners

author: gauze
author_rank: Newbie
timestamp: December 01, 2022, 05:04:13 am
content: I am trouble shooting something that doesn't power on and I have arrived at the mains power transformer when switched to 110v volt (my country) I get a resistance on primary side of around 45 ohms, and if I put it in 220v position and check the 2 connected terminals I get around 160 ohms, I'd think it should be 2:1 ratio so I think something is damaged in the transformer, am I correct?ps The internal part number is JVC QQT0177-004 and has additional marking "TAM M 0103" which I can't find a datasheet for.thanks

author: wasedadoc
author_rank: Super Contributor
timestamp: December 01, 2022, 09:43:52 am
content: That 4:1 ratio is possibly correct. A common method is to have two 110 windings. They are connected in parallel for 110 volt input but in series for 220.
Small Question on SMPS Tranformer Isolation Material - Page 1
Forum section: electronics / beginners

author: homebrew
author_rank: Frequent Contributor
timestamp: April 22, 2016, 07:29:58 am
content: Hi,can anybody tell me what the yellow sticky tape inside typical SMPS transformers actually is?It looks like electrical tape - which it is certainly not. Kapton-Tape it isn't either.Btw., when winding a transformer myself, is Kapton a viable (and safe) option to use?

author: Richard Head
author_rank: Frequent Contributor
timestamp: April 22, 2016, 08:20:26 am
content: It's polyester tape. Normally 50um thick but to check clean the glue off and measure with a micrometer.Not nearly as temperature hardy as polyimide, but easier to use as it stretches nicely.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 22, 2016, 09:43:30 am
content: Mylar/polyester, with acrylic adhesive. 3M Scotch something or other is pretty standard.Kapton/polyimide is fine too, but rather expensive and higher temperature than you need. (Ironically, polyimide with acrylic adhesive isn't much higher temperature than polyester. The silicone adhesive stuff is good for plenty, though.)Tim

author: Richard Head
author_rank: Frequent Contributor
timestamp: April 22, 2016, 10:58:39 am
content: TimI've dismantled seriously overheated HF transformers that use polyimide tape and the copper wire is almost black due to overheating but the polyimide tape can still be unwound and is virtually untouched. When polyester tape is used it turns into a melted gooey mess. Obviously, no normal person would design a transformer to operate anywhere near these limits but it's good to know what gives when you push the limits.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 22, 2016, 12:38:47 pm
content: Yeah, normal magnet wire enamelmelts and soldersat the temperatures where polyimide just begins to sweat. To use it to its fullest advantage, you must use high temperature (usually, polyimide as well!) enamel, and bobbin, and either keep the core a whole lot cooler (ferrites run out of steam much above 100C!), or use a higher temperature material (NiZn ferrite or powdered iron)!Tim

author: homebrew
author_rank: Frequent Contributor
timestamp: April 24, 2016, 06:11:11 am
content: Thank you very much for the infos!I have Kapton laying around. And for a one-off thing, I don't care the costs that much.
Small resistor value for a differentiator - Page 1
Forum section: electronics / beginners

author: renzoms
author_rank: Regular Contributor
timestamp: October 24, 2019, 12:58:34 am
content: I’m having a hard time understanding “pick a resistor value that is small enough so dVout/dt << dVin/dt” for a differentiator. I’m graphing 5 V DC supplied to this circuit, and even at 1M ohm and 1pF, the voltage across the capacitor reaches Vin in 10us. I don’t experiment with AC & ”high speed” yetI get how a small resistor (R2) connected to another resistor (R1) in series, would cause a large portion of the supplied voltage to be across (R1). I’m trying to connect that to this technique and I need help. 🙏 Thank you.

author: rstofer
author_rank: Super Contributor
timestamp: October 24, 2019, 01:38:58 am
content: When they calculate I, they assume dVin/dt >> dVout/dt and summarily drop dVout/dt from the remainder of the calculation. What I think they aren't pointing out is that dVin/dt is the result of a driving circuit with a very low impendance compared to R such that the source can charge the capacitor much faster than R can discharge it.https://www.electronics-tutorials.ws/rc/rc-differentiator.htmlThis article also doesn't get into the driving impedance but I imagine they are talking about a perfect signal source which would have zero impedance or, more practically, 50 Ohms. So, if R is 10K, 10K is >> 50 so it should work. But that assumes that Vout is driving into a circuit with very high impedance.All of which points to using an op amp on the output to buffer the voltage and provide a low impedance to the next stage.https://www.electronics-notes.com/articles/analogue_circuits/operational-amplifier-op-amp/analogue-differentiator-circuit.phpIn the realm of analog computing, we go out of our way to avoid differentiators because they are high pass filters and allow noise to propagate. An integrator, by definition, accumulates the noise and averages it out like a low pass filter.

author: renzoms
author_rank: Regular Contributor
timestamp: October 24, 2019, 01:52:55 am
content: Quote from: rstofer on October 24, 2019, 01:38:58 amWow dude. Thanks I really understand more of this information now.
"small sensitive triac" - meaning? - Page 1
Forum section: electronics / beginners

author: aneevuser
author_rank: Frequent Contributor
timestamp: May 06, 2022, 12:31:50 pm
content: I have found the following ST app. note, "TRIAC analog control circuits for inductive loads"(https://www.st.com/resource/en/application_note/an308-triac-analog-control-circuits-for-inductive-loads-stmicroelectronics.pdf)It suggests a modification to improve triac triggering in an analogue AC power control circuit for inductive loads; this requires what they call a "small sensitive triac". (This is shown in Figure 8.) However, I'm not sure what they mean by this.I'm guessing that "small" means "low power requirement", but I'm not sure what they mean by "sensitive" - do they mean "low gate threshold voltage"? If so, I can't really see why - the auxiliary triac gate sees the voltage that triggers the diac, which is going to be much greater than the typical triac gate threshold voltage anyway, as I understand it.As things stand, it seems to me that this circuit will function fine with both triacs identical. Am I misunderstanding things here?

author: Terry Bites
author_rank: Super Contributor
timestamp: May 06, 2022, 03:57:42 pm
content: It refers to a low gate current needed for triggering.For Triacs and SCRs its gate current that defines gate sensitivity not voltage.You do have to apply a couple of diode drops with your current drive never the less.

author: Benta
author_rank: Super Contributor
timestamp: May 06, 2022, 06:22:43 pm
content: Means something like a MAC92 (obsolete).

author: edavid
author_rank: Super Contributor
timestamp: May 06, 2022, 06:47:07 pm
content: 2N6075B says right on the datasheet that it has "Sensitive Gate Triggering", and it's still in production.It's in a smallish TO225 package.https://static6.arrow.com/aropdfconversion/de332a907176345b94718624b0fa42132d8685fa/littelfuse_thyristor_2n6071_d_datasheet.pdf.pdf

author: Benta
author_rank: Super Contributor
timestamp: May 06, 2022, 07:12:45 pm
content: 2N6075B is somewhat big for this, I'd say.The Littelfuse LX803 could fit the bill.

author: Ian.M
author_rank: Super Contributor
timestamp: May 06, 2022, 08:27:19 pm
content: TO-92 package TRIACs exist. e.g.https://eu.mouser.com/c/semiconductors/discrete-semiconductors/thyristors/triacs/?package%20%2F%20case=TO-92-3There are currently 18 part numbers in stock at Mouser in that category with 5mA or under gate current to trigger.

author: aneevuser
author_rank: Frequent Contributor
timestamp: May 07, 2022, 07:09:46 am
content: Quote from: Terry Bites on May 06, 2022, 03:57:42 pmI see. So here, I guess the requirement for sensitivity is due to the fact that when the auxiliary triac is on, the RC time constant is much smaller due to the pot. being bypassed, and so there is simply much less charge available on C to drive the auxiliary triac's gate?QuoteI'm not sure what you're saying here: where do a couple of diode drops come into the picture? Is this referring to the gate threshold voltage? Is that typically 2 diode drops?
Small sensor voltage with unipolar opamp - input offset troubles! - Page 1
Forum section: electronics / beginners

author: justlv
author_rank: Newbie
timestamp: November 14, 2014, 09:20:34 am
content: I am conditioning a sensor which has a small voltage output (~1mV max - it's a thermopile) and trying to use a low cost low-offset amplifier like the MCP6422.I'm using a large non-inverting gain (3.3M/1k). This results in the input offset of 200uV in some cases to result in a voltage of up to 700mV.BUT - I am okay with this as I am measuring the delta between when the thermopile is ~0V to when it is around 1mV, EXCEPT when the input offset voltage of the opamp used happens to be negative, clipping the first value resulting in a delta less thanCan anyone help with any techniques to mitigate this? I've considered an auto-zero amp (MCP6V32) or somehow adding a 200uV reference to prevent clipping?Greatly appreciated!

author: Paul Price
author_rank: Super Contributor
timestamp: November 14, 2014, 05:40:02 pm
content: Just use a small trimpot connected to a stable reference voltage and apply an offset trimming current to the - input of the MCP6422 through a large valued resistor. In other words, compensate for the offset by trimming the op-amp output to 0.0000V with the trimmer to balance out the offset voltage.

author: free_electron
author_rank: Super Contributor
timestamp: November 14, 2014, 06:16:49 pm
content: large gain is your problem.you have large resistors. multiply with input offset current and you get huge offsets.use several opamps cascaded each with max a x10 gain.

author: justlv
author_rank: Newbie
timestamp: November 14, 2014, 06:29:34 pm
content: Thanks free_electron - but wouldn't this just stack - unless we're relying on the average offset of the whole chain -> 0. Should there be AC coupling between?Also, if the offset is -200uV and my signal varies from 0 - 1mV, I will only read 800mV delta no matter what my gain is.

author: justlv
author_rank: Newbie
timestamp: November 14, 2014, 06:32:43 pm
content: Quote from: Paul Price on November 14, 2014, 05:40:02 pmThanks - I'd need a digital trimpot I'd think. It may just be easier to use a more expensive auto zeroing opamp?

author: mzzj
author_rank: Super Contributor
timestamp: November 14, 2014, 06:40:11 pm
content: Quote from: justlv on November 14, 2014, 06:29:34 pmUse better opamp. Cascading doesnt really help as you probably cant use AC coupling because you lose your measurement signal.Look for some opamp with less than 10uV offset, not 1000uV as specified for your current opamp!
Small signal analysis when base is grounded ? - Page 1
Forum section: electronics / beginners

author: lordvader88
author_rank: Frequent Contributor
timestamp: April 29, 2019, 07:17:10 pm
content: I finally learned the basics of the hybrid T-model for BJT AC signals, so that's great. Say u have a BJT voltage reg. circuit, where the AC ripple from rectifier/filtering, is on the source voltages of everything. And have cap'a on the bases of BJT's. So ignoring the actual reactance of the cap, if u do small signal analysis with the model, u short the base. So there is no ac base current? Even tho I can see the voltage ripple. So it's common-mode,Also in for instance a Colpitt's oscillator, where let's say a parallel tank circuit has C1 between B-E and C2 between E-gnd. Also the DC bias across the tank is usually always way way more than uV and mV considered in small signal analysis. So am I missing something or is this model is not for this case at all ?Also I forget how I once did the loop gain of this type of oscillator, and I can't find the video, so I have to learn that I know. But in that analysis I was using the actual reactances, and I guess just the large scale BJT model ?I have made a model in LTspice of my broken Tektronix 422 PSU, and it works quite well.What of the small signal analysis can be applied to this ? Any where a BJT does't have a cap on it's base ?Or should I be able to work out all relevant stuff from doing a massive mesh/node analysis with large scale BJT model, with common-mode AC ignored, is that right ?

author: lordvader88
author_rank: Frequent Contributor
timestamp: April 29, 2019, 07:40:33 pm
content: https://www.seas.upenn.edu/~ese319/Lecture_Notes/Lec_19_Colpitts_Osc_09.pdfTime for another go this thenOk and I'm realizing I never used node/mesh analysis with complex numbers and impedance that way. So now I realize I should use that on big and small BJT models. So I'll try that and see if it matches with LTspice.I'm forgetting what I know and don't know
Small Signal MOSFET Transconductance Gain - Can't Figure it Out - Page 1
Forum section: electronics / beginners

author: willbanks
author_rank: Contributor
timestamp: April 15, 2023, 07:53:25 pm
content: I am tasked to find the gain of this small signal circuit drawn in my work. I have absolutely, NO idea how the professor came up with his answer. I would e-mail him, but he doesn't respond on weekends.The professor's answer is included. If anyone can tell me where I am messing up, I would be incredibly grateful. the channel length modulation (lamda) = 0, so the output impedance is infinite therefore an open circuit.https://imgur.com/a/tQGSZr8
Small solar panel - Page 1
Forum section: electronics / beginners

author: @rt
author_rank: Super Contributor
timestamp: November 14, 2021, 02:48:29 am
content: HiI have a 5W solar panel from Jaycar (Australia) that comes with alligator clips presumably for connecting to a 12V battery.Why is this ok to use 17.5V panel directly connected to a battery without a charge controller? Will this damage the battery?Open Circuit Voltage: 22.0V, Voltage at Pmax: 17.6V, Current at Pmax: 0.29A.

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: November 14, 2021, 03:11:33 am
content: What is the C-rate of the battery ?What was the state of charge of the battery ?" Why is this ok to use 17.5V panel directly connected to a battery without a charge controller? "Without more details , that statement is a assumption .

author: brucehoult
author_rank: Super Contributor
timestamp: November 14, 2021, 03:37:05 am
content: As it says, if your battery is of sufficient capacity then it's ok to just leave it connected directly as a trickle charger. Sadly, they don't seem to actually say what is sufficient. I think around a 10 Ah battery would be right for trickle charging with this panel.Otherwise:"A charge controller is recommended to prevent over-charging of the battery when the panel output exceeds the routine circuit load."They even suggest one:https://www.jaycar.co.nz/miniature-12v-3a-pwm-solar-charge-controller/p/MP3762That would handle up to ten panels like you're using, and allow a battery to be charged much more quickly but without overcharging it.

author: Renate
author_rank: Super Contributor
timestamp: November 14, 2021, 11:35:35 am
content: Most small, consumer solar panels have an open circuit voltage of 18V or so.Since everything (including solar panels) has a load curve you can run them at different loads, different voltages, different currents.At 12V it's probably running around 1/3 of an Amp or so.You could leave this on your car battery for a year in the Kalihari desert and not worry about overcharging.If you are using this on something smaller a charge controller of some sort would be in order.

author: brucehoult
author_rank: Super Contributor
timestamp: November 14, 2021, 12:02:33 pm
content: Quote from: Renate on November 14, 2021, 11:35:35 amThe product page for what I assume he's talking about (https://www.jaycar.co.nz/12v-5w-solar-panel-with-clips/p/ZM9050) says:- open circuit voltage 21.8 V- short circuit current 310 mA- Maximum power point 17.4 V 290 mASo, feeding into 12 V or 13.8 V it's obviously going to be somewhere between 290 and 310 mA, probably nearer the lower end of that.QuoteAgreed, the average car battery being around 50 Ah. Even a motorcycle battery would probably be ok.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: November 14, 2021, 01:23:24 pm
content: I know such panels mostly being used as kind of 'battery self-discharge protection' for vehicles or boats that are idling in winter. Seems to me perfectly sensible though to just connect them to a normal Pb-battery without any worries. Those panels just have too high internal impedance to cause overcharge on a Pb-battery
Small Switch - Current Handling? - Page 1
Forum section: electronics / beginners

author: LeoTech
author_rank: Regular Contributor
timestamp: March 18, 2018, 02:20:48 pm
content: Hey everyone,Quick question about small switches:I am looking for a switch for my next project, and as I have almost zero experience with switches and current handling, I thought to ask here.The switch in question is this one:(Source: Muekra.de)For several reasons, which are to complicated and unnecessary to explain here, I can only use this supplier and I am not able to find a datasheet for this switch.So for my question: Will this switch be able to control/handle a current of max. 20 mA at 12 Volts?Thanks in advance,Leo

author: Zero999
author_rank: Super Contributor
timestamp: March 18, 2018, 02:44:08 pm
content: Impossible to know without the data sheet.One of the problems with low currents is the oxide layer on the contacts may not be broken, when the contacts close. The current required to ensure the switch works reliably, is known as the wetting current, i.e. the minimum current which can be reliably switched.

author: SeanB
author_rank: Super Contributor
timestamp: March 18, 2018, 03:10:17 pm
content: That switch 20mA at 12V no problem short term. However long term those switches are not exactly the most reliable type, they, depending on the actual manufacturer, the choice of materials they used that day ( plastics and steel they use is very variable in quality, as it generally is a cheap recycled material with unknown quality control other than meeting some basic specs for dimensions and melting point) and just how worn the actual production tooling was. But, for a switch where under 500 operations is going to be the life, and you are not in any sort of aggressive atmosphere or too humid, it will generally do.

author: LeoTech
author_rank: Regular Contributor
timestamp: March 18, 2018, 03:25:00 pm
content: Thanks for the answers!Quote from: Hero999 on March 18, 2018, 02:44:08 pmI've never heard of that, but it sounds plausible - although I doubt this will have any effect. If the current turns out to be to low, I can always increase it. I am more worried about the max current.Quote from: SeanB on March 18, 2018, 03:10:17 pm500 operations is good enough for me, as this will be a one-off project sitting on my bench, and I can always replace the switch if necessary.In terms of quality control, you are most likely correct, as this indeed appears to be a cheapo from China.Thanks again,Leo

author: Gyro
author_rank: Super Contributor
timestamp: March 18, 2018, 05:03:23 pm
content: That switch should have no difficulty handling your maximum 20mA current, particularly at 12V (very low signal voltage can be more of a problem). It may not be of good quality but slide switches have good contact wiping action.If in doubt, try it with an LED and series resistor and see if it flickers.

author: Zero999
author_rank: Super Contributor
timestamp: March 18, 2018, 05:58:31 pm
content: Quote from: LeoTech on March 18, 2018, 03:25:00 pmhttps://en.wikipedia.org/wiki/Wetting_currentLooking at it again, you should be fine, with 20mA as it's a small switch.
Small toroid mechanical fixturing - Page 1
Forum section: electronics / beginners

author: matthuszagh
author_rank: Frequent Contributor
timestamp: November 28, 2022, 06:26:29 pm
content: I'm building a PCB circuit that requires a custom-wound toroid for use as a 3-winding transformer. The toroid will be pretty small: OD=9.5mm, ID=4.75mm (https://www.mouser.com/ProductDetail/Fair-Rite/5961000201?qs=Ca1fAiqt1aqSBOA35FqYWg%3D%3D&countryCode=US&currencyCode=USD). I'd prefer that the toroid not be mechanically supported by the transformer windings. Suggestions for how to support this mechanically? An enclosing case, especially one that does not allow water and IPA to enter, would be nice but not necessary. If using the windings for support is the typical solution, that would be useful to hear, along with any suggestions for how to make that robust (e.g., keeping the leads short).

author: fourfathom
author_rank: Super Contributor
timestamp: November 28, 2022, 06:57:15 pm
content: A [machine screw / insulating washers / nut] through a hole in the PCB? Zip-ties through holes in the PCB? Glue?

author: TimFox
author_rank: Super Contributor
timestamp: November 28, 2022, 07:17:15 pm
content: One thing to avoid is a conductive path that goes around the toroid (from the bottom, through the hole, around the top, and back to the bottom).That forms a "shorted turn" that will degrade the transformer.A screw through the hole, with no "roof" around the toroid, is OK.

author: Benta
author_rank: Super Contributor
timestamp: November 28, 2022, 10:25:28 pm
content: A toroid that small would typically be mounted with a blob of thermal glue.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 29, 2022, 01:46:19 am
content: Agreed, glue, hot-melt, E6000, silicone, etc. would all be fine, to varying degrees of permanentness.Tim

author: TERRA Operative
author_rank: Super Contributor
timestamp: November 29, 2022, 04:19:52 am
content: I've seen them in HP/Tek gear fixed in place with two cableties wrapped around each side of the toroid and through 4 holes (two per cabletie, one inside the toroid and one outside)I've also seen the toroid epoxied (or potted in a small box) to a small carrier PCB with pins attached, then soldered to the main PCB.You can buy pins that clip onto the side of a PCB then solder them into place, so the legs extend down to be mounted to the main PCB.The Advantest R6142 and R6144 stand their toroid on its side and use one cabletie through two holes on the PCB, so there are a few options.
Smallest, cheapest isolated power supply - Page 1
Forum section: electronics / beginners

author: cowana
author_rank: Frequent Contributor
timestamp: August 12, 2013, 12:44:58 pm
content: I want to build a small module to be connected inline with the power cable to my audio amplifier.It will contain an MCU, and monitor the incoming audio signal. If there is a signal, it will switch on the amplifier with an SSR. If there has been no signal for 10 minutes, it will switch off the amplifier.So, this project needs a power supply, with the following specifications:Input voltage: 240v AC (UK mains)Output voltage: between 3.5v and 5.5v DCOutput Current: <20mA (probably <5mA)Must be isolated/floating, as it will be connected to audio groundIf it wasn't for the last condition, I would use a capacitor/resistor voltage divider and a zener diode to regulate. However this wouldn't be isolated.I could use a small transformer (such ashttp://uk.farnell.com/block/vb1-0-2-9/transformer-1va-2-x-9v/dp/1131623), single diode rectifier, reservoir capacitor and a zener diode for regulation - however this is quite a large solution and I'd like it to fit in a very small case.Any other thoughts or suggestions I've missed would be appreciated!Cheers,Andy

author: Chet T16
author_rank: Frequent Contributor
timestamp: August 12, 2013, 12:55:14 pm
content: Smash open a phone charger?

author: madires
author_rank: Super Contributor
timestamp: August 12, 2013, 01:15:39 pm
content: I use those small Block transformers too for projects with low power consumption. With 22mm X 32mm X 27mm they are quite small, IMHO. And the best feature is that they run 24x7 for 20 years without any problem (home automation). I doubt a good quality mobile phone charger would be smaller or as reliable as the transformer. And the transformer isn't expensive either (some weeks ago I paid EUR 2,40 for 1.5W 6V).

author: Zero999
author_rank: Super Contributor
timestamp: August 12, 2013, 03:42:47 pm
content: I agree a transformer is probably a more reasonable solution. An SMPS will have a higher leakage current and be more noisy so could be unsuitable for this.

author: cowana
author_rank: Frequent Contributor
timestamp: August 14, 2013, 09:02:59 am
content: Thanks for the responses.I hadn't though of a phone charger - and for a project that doesn't require to be on 24/7/365, it's a good solution. However I'd be concerned about a chinese/cheap charger's long term reliability - and using a more expensive brand name one would cost significantly more than a transformer solution.So, I think I'll go with the transformer solution - one of the 1W block transformers, single diode rectifier, bulk capacitor and zener regulation.The audio signal will have a (schottky) rectifier, and then a LPF feeding into the uController.Andy
Smallest wire connectors? - Page 1
Forum section: electronics / beginners

author: Watth
author_rank: Frequent Contributor
timestamp: July 22, 2023, 03:04:34 pm
content: Hello EEV people,I'm looking for really smallest wire to wire connectors, with male and female version; I have the classic "Dupont" connectors, but even these are oversized for this use.The idea is to add lights to a model kit, this means voltage and current are quite small for most lights. (The model kit is Blade Runner's police spinner)Do you know of a model that fits this requirements ?Thanks for reading!Matth

author: Jeroen3
author_rank: Super Contributor
timestamp: July 22, 2023, 03:17:32 pm
content: You can try JST SHR, but you'd need to buy precrimped wire or get the tiny crimper.In model trains things are just soldered to the tiny pcb.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 22, 2023, 03:25:12 pm
content: Molex Picoblade are a quite good balance between size and robustness - 1.25mm pitch I think. You can get pre-crimped leads, and cheap knockoffs on Aliexpress
Smart switch - Page 1
Forum section: electronics / beginners

author: rthorntn
author_rank: Frequent Contributor
timestamp: September 24, 2020, 06:58:22 am
content: Hi,I have an on/off rocker switch, it connects between Terminal 6 and 2 (<20mA of current flow) on a solar transfer switch, when the switch is off (default) my solar panels go to inverter 1, when the switch is on my solar panels go to inverter 2.I want to automate this, preferably with something off the shelf, smartphone control kind of thing.I'm pretty sure I need it to have a latching relay to replace a mechanical rocker switch.If it has a ESP wifi then I will probably flash it if I can (ESPHome or Tasmota) so I can connect it to Home Assistant later?Has anyone seen anything like this, I see things like Shelley, Sonoff and Tuya, a lot of that stuff seems to be deal with switching AC stuff on/off?Thanks.Richard
SMD Transistor Codes 2 Ghz Amp - Page 1
Forum section: electronics / beginners

author: MavMitchell
author_rank: Contributor
timestamp: March 21, 2019, 07:26:05 am
content: So these SMD codes are a new thing for me.My RS SML Sig gen doesn't make power when going through the Output Unit(above 1.2G). I found the one of the OP transistor shorted out, and it took out the bias resistors and a bit of fiber glass.The resistors are completely black so will have to work out what they were, but the FET is marked as H2, and I cant seem to find out what it is.It will be a 2Ghz+ device capable of at least +10dbm, running on about 8V.Some guidance would be great.Thanks.

author: andybarrett1
author_rank: Regular Contributor
timestamp: March 21, 2019, 09:24:16 am
content: HiMight not help in this case but is a good reference to SMDshttp://www.turuta.md/demobook/SMD-2014-sample.pdfAndy

author: ebclr
author_rank: Super Contributor
timestamp: March 22, 2019, 02:05:49 am
content: SHF-0289http://web.rfoe.net:8000/SIRENZA/PDF/gaas/shf/89/shf-0289.pdf

author: MavMitchell
author_rank: Contributor
timestamp: March 23, 2019, 12:03:20 am
content: Perfect.. Thanks for the help..
SMD  - Page 1
Forum section: electronics / beginners

author: Electronics-Repairman
author_rank: Contributor
timestamp: July 08, 2014, 07:46:10 pm
content: Ok troops I'm finally giving into SMD, I want to build a pulse generator where component placement is important, so going for it everything is SMD, glad I have a large bench magnifier, and a good set of tweezers. This could be a steep learning curve

author: Matje
author_rank: Regular Contributor
timestamp: July 08, 2014, 10:39:39 pm
content: Quote from: Electronics-Repairman on July 08, 2014, 07:46:10 pmDon't worry too much, I found it easier than expected, at least for semi-sensible sized parts - no 0402 here.One thing I noticed: I find it easier to work with magnification glasses (attached to your head ;-) instead of a bench magnifier, because these give you more freedom of movement and view. Probably a personal preference to be tested by every person for themselves.

author: GreyWoolfe
author_rank: Unknown
timestamp: July 08, 2014, 10:53:14 pm
content: I second Matje. I have a desk magnifier and a headset magnifier. I use the headset more than the bench magnifier.

author: TheBorg
author_rank: Frequent Contributor
timestamp: July 09, 2014, 04:34:36 am
content: I try to do 0603's at the very minimum, 0805's if I can fit them.But hand soldering 0402's is always fun!Get a decent iron with a decent tip and you'll be fine

author: Electronics-Repairman
author_rank: Contributor
timestamp: July 09, 2014, 05:59:24 am
content: Thanks everyone I'll bare all this in mind

author: jay
author_rank: Regular Contributor
timestamp: July 09, 2014, 07:15:26 am
content: With some magnification hand soldering 0805's and SO packages is actually quicker and easier than TH stuff when you get used to it. I often do mixed SMD & THT boards in my hobby prototypes.

author: sacherjj
author_rank: Frequent Contributor
timestamp: July 09, 2014, 11:18:00 am
content: Hopefully you have a solid color hard surface over your work area. My home lab area was above carpet. Anything smaller than 0805 that was dropped was just considered a loss.

author: hlokk
author_rank: Contributor
timestamp: July 09, 2014, 11:56:02 am
content: I only recently attempted soldering SMD for the first time. I got 1206 resistors figuring they'd be the easiest to solder, but they're too large from spanning between veroboard tracks. 0805's werent much harder to solder at least.Wasnt as hard as I thought though. Sometimes a bit fiddly holding parts down steady but not too bad. Daves tip of 0.5mm solder and a chisel tip iron worked wellOne tip though is if you can, particuarly on IC legs, try pressing the solder tip so it touches both the leg and the solder pad. Touching just on top of the leg and hoping it would "heat through" required longer iron times which prob heated the chip more (although for resistors, touching the top of the contact worked well. Dont forget the flux paste (I found a pen easy). Good luck!
SMD 750 - Page 1
Forum section: electronics / beginners

author: OpenCircuit
author_rank: Regular Contributor
timestamp: May 25, 2017, 02:42:40 am
content: 75ohm?http://www.hobby-hour.com/electronics/3-digit-smd-resistors.phpDoes it appear damaged? Looks like a burn on the 5. DMM indicates OL out-of-circuit..

author: sleemanj
author_rank: Super Contributor
timestamp: May 25, 2017, 02:56:31 am
content: Yes looks like a 75 Ohm resistor

author: xrunner
author_rank: Super Contributor
timestamp: May 25, 2017, 03:01:45 am
content: Quote from: OpenCircuit on May 25, 2017, 02:42:40 amIt doesn't look damaged really, but you seem to state you measured it out of circuit. If it doesn't measure 75 ohms then it ain't no good, doesn't matter what it looks like.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: May 25, 2017, 03:09:36 am
content: Quote from: xrunner on May 25, 2017, 03:01:45 amWondering if the mark on the 5 is consistent with an open SMD. On desk so kinda concerned that if I push to hard with the probe and the probe slips... away goes the resistor. It will obviously never be found again. Appears bad, but never hurts to verify by multiple means- experienced EEs and knowledgeable hobbyists here.

author: xrunner
author_rank: Super Contributor
timestamp: May 25, 2017, 03:13:04 am
content: Just replace it if you aren't sure - it isn't an expensive part.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: May 25, 2017, 03:19:10 am
content: Quote from: xrunner on May 25, 2017, 03:13:04 am...and a week to get here. Verify value and go through the scraps and hope to get really close.

author: Brumby
author_rank: Unknown
timestamp: May 25, 2017, 05:42:15 am
content: ... or stack two 150 ohm ones on top of one another.(Or any other parallel sets to give you 75 ohms)

author: OpenCircuit
author_rank: Regular Contributor
timestamp: May 26, 2017, 04:26:37 am
content: Found a 67.5....
SMD cap ID help - Page 1
Forum section: electronics / beginners

author: warrjon
author_rank: Newbie
timestamp: May 31, 2019, 11:20:08 pm
content: Hi Folks, My name is Warren I was a bench and metrology tech most of my life, retired now. I have done very little SMD work as most of the gear I worked on was Military and/or Aviation where we had to use OEM parts so my SMD experience is limited.Anyway my TDS2024 scope decided to turn its toes up. I have identified 3 faulty components 1 cap and 2 transistors. I have IDed the transistors but the cap is eluding me. The ID id J685L (I make out the 685 is 6.8uF) and polar so either Tantalum or Electro.

author: JustMeHere
author_rank: Frequent Contributor
timestamp: June 01, 2019, 01:11:34 am
content: See if you can figure out what it is connected to. Then see what the datasheet says that component needs.

author: radiolistener
author_rank: Super Contributor
timestamp: June 01, 2019, 05:55:52 am
content: tantalum smd capacitors usually has yellow color.

author: Nerull
author_rank: Frequent Contributor
timestamp: June 01, 2019, 07:13:00 am
content: Plenty of tantalums are black.

author: gamalot
author_rank: Super Contributor
timestamp: June 01, 2019, 07:38:23 am
content: They are 6.8uF/6.3V tantalum capacitors.

author: warrjon
author_rank: Newbie
timestamp: June 01, 2019, 07:49:26 am
content: I thought they were yellow until I dug around RShttps://au.rs-online.com/web/p/tantalum-capacitors/8603815/I have come up with a plan.The USB driver has the same cap to ground. I am going to steal it and plug it in where the bad one was and replace the USB cap with one of those from RS.
SMD Capacitor Help needed - Asus Rog Strix G351G Repair - Page 1
Forum section: electronics / beginners

author: EpicLPer
author_rank: Newbie
timestamp: March 02, 2024, 09:17:51 pm
content: Heya,I'm currently trying to repair a laptop (Asus Rog Strix G351G) from a friend and I have very limited SMD knowledge, but I found a blown SMD cap and unsoldered it, now the short on other capacitors is completely gone. Measuring the blown one also shows it's shorted entirely.Now my question is: Is there any way to find out what value it is? There are very similar ones around it, potentially even the same. I also have a few spare boards from cameras and so on laying around, but I don't think they might be the same value.I really have barely to no knowledge how these brown SMD caps work, but I do know that caps usually have different voltage ratings and capacitance. So I highly doubt "just soldering one in from an unknown board and hoping for the best" would work here, even if it would be the easiest solutionI also don't know how to get circuit diagrams (yet alone how to read them correctly) for this specific laptop.Thanks already for your time and help!

author: janoc
author_rank: Super Contributor
timestamp: March 02, 2024, 09:49:56 pm
content: That is most likely a decoupling capacitor only and very likely the same as the identically looking ones next to it.Probably 100n, anything higher rated than about 20V should be OK. It may even work without it as there is most likely plenty of decoupling capacitance around and one missing will not matter much. The exact value is unlikely to be critical here.There isn't really a way to find out what the original value was unless you have either schematic with the value written on (good luck finding one) or another identical board with the capacitor still good and there you could desolder and measure it.

author: EpicLPer
author_rank: Newbie
timestamp: March 02, 2024, 09:57:38 pm
content: Quote from: janoc on March 02, 2024, 09:49:56 pmI happened to find a schematic for it, but I really don't know how to read itI marked the cap in the screenshot, but not sure where to get its values from. This has been posted in another forum where someone asked for cap values.

author: EpicLPer
author_rank: Newbie
timestamp: March 02, 2024, 10:00:02 pm
content: Ah, seems like I found it on another PDFThis seems to be the exact values.Now to find a matching one somewhere tho ^^

author: EpicLPer
author_rank: Newbie
timestamp: March 02, 2024, 11:57:32 pm
content: Good NewsThe laptop works again!At least for now. I'm still not sure if the random capacitor I put in was the right one, but the nF and size seemed to match or was even above (my multimeter was really wonky and showed values all over the place, but when it shortly settled it was above 10uF even) so I hope it'll keep working
SMD capacitor markings - Page 1
Forum section: electronics / beginners

author: MikeK
author_rank: Super Contributor
timestamp: April 25, 2022, 03:52:51 pm
content: Looking for help identifying the electrolytics in the image. The larger one appears to be 100uF/6V, right? And the other is 47uF? I'm not sure about the voltage on the smaller one.

author: free_electron
author_rank: Super Contributor
timestamp: April 25, 2022, 04:14:27 pm
content: correct

author: MikeK
author_rank: Super Contributor
timestamp: April 25, 2022, 06:25:22 pm
content: The "6A" on the smaller one indicates 6 volts?

author: Doctorandus_P
author_rank: Super Contributor
timestamp: April 25, 2022, 06:53:48 pm
content: Probably not.It's more likely that it's just an identification code, just like the "3A" on the larger capacitor.If you then have the documentation from the manufacturer of your capacitors, it has a look up table so you can see what the specifications of the capacitor are.

author: MikeK
author_rank: Super Contributor
timestamp: April 25, 2022, 07:10:11 pm
content: There doesn't appear to be a manufacturer printed on the cap. The device was made in Japan (about 26 years ago), but I looked at the datasheet for Nichicon caps and it doesn't seem to identify these markings.The service manual for the device has a schematic, but...1) the larger cap is 47uF in the schematic and 2) the smaller cap is listed as 6V but also shows a test voltage of 6.3V at the positive terminal.

author: thm_w
author_rank: Super Contributor
timestamp: April 25, 2022, 10:29:09 pm
content: Quote from: MikeK on April 25, 2022, 06:25:22 pmSmaller one is likely 10Vhttps://forum.digikey.com/t/smt-electrolytic-capacitor-with-no-voltage-rating/974

author: MikeK
author_rank: Super Contributor
timestamp: April 26, 2022, 01:07:39 am
content: Okay, thanks.