hybridfree/eevblog-posts huggingface dataset:
Do I need a 3 gang switch to parallel one, two , or three caps across another? - Page 1
Forum section: electronics / beginners

author: Chris Wilson
author_rank: Super Contributor
timestamp: November 18, 2020, 09:38:39 pm
content: I want to be able to sequentially additively switch in three fixed caps across a variable cap as padders, with a manual switch. What sort of switch would suit please? Using a switch to add series components is easy, but I am struggling as to the easiest way to parallel devices in sequence, adding another and another to gain more padding. Thanks.

author: Ian.M
author_rank: Super Contributor
timestamp: November 18, 2020, 09:54:34 pm
content: Assuming the extra caps are all the same, take a two pole four way rotary switch, on one pole link ways 2 and 4, and wire a single cap to them, and on the other pole link ways 3 and 4 and wire two caps in parallel to them. The result goes from no caps at position 1 to three at position 4 in uniform steps.

author: jimmc
author_rank: Frequent Contributor
timestamp: November 18, 2020, 11:07:30 pm
content: Can be done with a 3 pole 4 way switch, usually in a single wafer.C1 to pole 1, C2 to pole 2 and C3 to pole 3, other ends of capacitors all joined to terminal 1.Common the following:positions 2, 3 & 4 of first section withpositions 3 & 4 of second sectionand position 4 of third sectionjoin to terminal 2.Then capacity between terminals 1 & 2 is0 in position 1C1 in position 2C1 + C2 in position 3C1 + C2 + C3 in position 4There is a switch that will do this directly but the are about as common as hen's teeth. (Cumulative switch see below)Jim

author: Brumby
author_rank: Unknown
timestamp: November 18, 2020, 11:40:23 pm
content: IFQuote from: Ian.M on November 18, 2020, 09:54:34 pmTHEN:QuoteELSE:Quote from: jimmc on November 18, 2020, 11:07:30 pm

author: Brumby
author_rank: Unknown
timestamp: November 18, 2020, 11:46:38 pm
content: As for this:QuoteTake it as a FYI. It comes into its own for high number of connections, but for your situation - unnecessary.

author: Chris Wilson
author_rank: Super Contributor
timestamp: November 19, 2020, 11:49:33 pm
content: The padder caps are different values so I will follow the example from jimmc. I have found a Russian ceramic switch with 3 poles and 5 positions, but with only 3 contacts on one section and just one on the last. The contacts are bolted to the ceramic with 2mm brass screws and nuts, with the nuts soldered over. I have heated and released the nuts and assembled it as a 3 way, 4 position, with much fiddling. So good to go. I need a hefty switch as the padders are across a vac variable in a balanced aerial tuner so the switch may see many kV. Thanks to all for the valuable help.
Do I need a scope??? Pliz - Page 1
Forum section: electronics / beginners

author: smid1584
author_rank: Newbie
timestamp: October 08, 2017, 07:18:30 am
content: Hi. Please excuse the total noob question...I've got a security background (things like network and web application defense/hacking), but I'm fairly new to the world of hardware. I have a basic understanding of PCBs, components and ICs, and have a tiny bit of experience with logic analyzers. I'd like to set up a lab and I'm wondering if I'll be able to get by without a scope for a while.Aside from normal soldering setup, I have a decent low-end multimeter and I'm planning to buy a Saleae 8-channel logic analyzer (not the pro version) and a universal device programmer (recommendations welcome--looking in ~$50-$75). I'm mainly interested in snarfing firmware and analyzing communications between components on embedded devices, and just learning more about electronics in general.My question is, what types of things might I need a scope for, that I wouldn't be able to do with the things I described above? (Remember, I'm a newb, so the more you can explain it like I'm five, the better...)Thanks!

author: Fred27
author_rank: Unknown
timestamp: October 08, 2017, 07:28:14 am
content: A logic analyser will show you the content of a digital signal. A scope will show you the quality - e.g. whether the edges are clean and whether the 1s and 0s are really the voltage you think they are.Whenever this question is asked here the general consensus is "get a scope". Personally, I'd say wait for a bit. A logic analyser should do for a while. By the time you need a scope you'll have a slightly clearer idea what you need. The chances are that you will get one though and it will be a Rigol DS1054Z.

author: rdl
author_rank: Super Contributor
timestamp: October 08, 2017, 07:44:54 am
content: Take a look at the Analog Discovery 2http://store.digilentinc.com/analog-discovery-2-100msps-usb-oscilloscope-logic-analyzer-and-variable-power-supply/It covers a lot of the basics and will still be useful if you move on to better equipment. One possible drawback is that it's PC based and not a stand alone device.
Do I need a USB Isolator when controller motors via a PC? - Page 1
Forum section: electronics / beginners

author: eeguy
author_rank: Regular Contributor
timestamp: May 08, 2020, 01:50:08 pm
content: Hi, I plan to use a PC to control some motors. The total amp under full load is about 60-80Amp, 12V. I have two devices (usb to rs485 interface adapter and a controller board with usb connection to the PC and several rs485 connectors to connect to the motors). Do I need to worry about the motors damaging the USB port of the PC? If so, what USB Isolator do you recommend? Thanks

author: Mp3
author_rank: Frequent Contributor
timestamp: May 08, 2020, 08:42:09 pm
content: Will one of the ADUM3160 / ADUM4160 premade adapters work for you? They're readily available from many places around $10. I was about to DIY one out of some parts from Mouser but these come in lower on the $ count and are premade.

author: wizard69
author_rank: Super Contributor
timestamp: May 08, 2020, 10:49:56 pm
content: Well it depends. A good isolator should protect you from mistakes and transients. The bigger question in my mind is why are RS 485 line going to the motors? It almost sounds like you have motors with integrated controllers /drives but you state that the controller is separate.I’d almost certainly look at every device connected to to see if their ports offer isolation. You may not need isolation if it is already incorporated into the motor controls. There are lots of other factors to consider so it isn’t that simple. For example does your control cabinet have high voltage devices, RF sources, large inductive noise producers such as relays. In an industrial solution there are often these risks to your equipment so isolated ports are often the default.

author: eeguy
author_rank: Regular Contributor
timestamp: May 09, 2020, 12:48:11 pm
content: Quote from: Mp3 on May 08, 2020, 08:42:09 pmDo you know which is good? There are lots of them. Some look the same or almost the same but from companies I have never heard of. There are $10-30 up to $250.
Do I need any extra circuitry for a basic power relay? - Page 1
Forum section: electronics / beginners

author: Marmotta
author_rank: Contributor
timestamp: January 01, 2020, 06:42:27 pm
content: I'm building a low powered PC with an external graphics card and noticed while testing everything for the first time that the graphics card would be constantly powered on, regardless of the state of the PC motherboard. As the motherboard and graphics card both run off separate 12V inputs, I'd thought I'd put a power relay on the input of the graphics card and connect the coil to a low-current 5V signal from the motherboard which would only be active when the PC was powered on.Since the 5V signal will only ever be present when I want the power passing through the relay to the graphics card, is there any reason to add any further circuitry to the relay for practical or safety purposes?

author: David Hess
author_rank: Super Contributor
timestamp: January 01, 2020, 11:49:51 pm
content: That should work fine.

author: JustMeHere
author_rank: Frequent Contributor
timestamp: January 02, 2020, 12:03:46 am
content: You need a fly back diode on the coil.

author: David Hess
author_rank: Super Contributor
timestamp: January 02, 2020, 12:57:50 am
content: Quote from: JustMeHere on January 02, 2020, 12:03:46 amThe flyback diode will not hurt but the bulk output capacitance on the 5 volt supply will absorb the back EMF.
Do I need load capacitors for XTAL with CL 4pF to 10pF? - Page 1
Forum section: electronics / beginners

author: ttodorov
author_rank: Regular Contributor
timestamp: April 28, 2018, 08:04:13 am
content: Hi,I am choosing a quatz crystal for a design I am working on and looking at Mouser and DigiKey, I see a lot of options with load capacitance of 10pF and below. What I am used to are crystals with CL of 18 to 22pF and these were easy: CL=C/2-Cstray, with recommended values for stray capacitance from traces and the like around 10pF. But with the new ones I am left scratching my headDo I need any ceramic caps with CL of the crystal at 10pF? And if the stray capacitance of the board is 10pF, how do I use a crystal with CL=4pF?I looked for application notes for crystals, but couldn't find anything specific or new enough (on sites like Abracon). I would appreciate some help, if anyone can answer that... Thx.Best regards!

author: Ian.M
author_rank: Super Contributor
timestamp: April 28, 2018, 08:51:50 am
content: You *ALWAYS* need the recommended load capacitance, whether as physical capacitors or as PCB trace capacitance. Also in the classic single gate Pierce oscillator configuration, the capacitors are essential to provide 180 deg phase inversion across the crystal.With Cl=4pF, you need 8pF either end of it as the load capacitors are in series from the crystal's viewpoint. As double sided 1.5mm FR4 will give you about 5pF*per cm2of trace area above a ground plane, neglecting capacitance between traces, that's easily achievable if you keep the crystal layout tight near the IC pins. If you come in under the target capacitance, just expand the crystal pads, but limit their solderable area with soldermask.* varying the geometry from long and skinny to short and stubby will significantly affect this value, I got it from a microstrip calculator that includes fringing fields, using a 2mm trace width. Your crystal traces will be mush narrower but 2mm isn't unreasonable as an average including the pads.
Do I need protection diodes on a colpitts oscillator? - Page 1
Forum section: electronics / beginners

author: Infraviolet
author_rank: Super Contributor
timestamp: January 07, 2023, 06:30:22 pm
content: There's an inductor involved, so will this need diodes to short away any high voltages that occur during powering on or off? Protecting the op-amp and anything else connected to the op amp's output? Or is this the type of circuit where currents will always be minimal, even if the resistors used set a gain so high that the output is a square wave?Thanks

author: Terry Bites
author_rank: Super Contributor
timestamp: January 07, 2023, 07:15:35 pm
content: At resonance the tank appears as a restance, the reactive currents are zero.The opamp will have its own input protection diodes. R1 will limit the current flowing (if any) inputs.Make sure R1 is large enough to keep the input current under the absolute max stated in the datasheet if you're worried.

author: bidrohini
author_rank: Regular Contributor
timestamp: January 08, 2023, 01:02:23 pm
content: I did not see any protection diode at the output of any Colpitts oscillator design so far. Still, if you are doubtful, please take a look at the datasheet of the particular OPAMP that you'll be using.
Do I need Static safe ? - Page 1
Forum section: electronics / beginners

author: Tomer
author_rank: Regular Contributor
timestamp: March 22, 2018, 03:08:03 pm
content: Hi Guys, I would like to buy a SOLDAPULLT desolder hand tool.The model that i want called "Universal" and it comes in 2 variations.1) Regular2) Static safeThe price difference between the models is negligible.My question. Is it a good idea to get the static safe because it can protect certain components and its nice/good to have ? or using a static safe can actually hurt or not be ok for certain uses ?I am a beginner and working mainly on pro audio gear.Thank youTom

author: Tom10000
author_rank: Contributor
timestamp: March 23, 2018, 12:55:10 am
content: No definitely not a solder sucker will not kill any component with static

author: Bassman59
author_rank: Super Contributor
timestamp: March 23, 2018, 03:11:27 am
content: Quote from: Tom10000 on March 23, 2018, 12:55:10 amWell ... it depends.The plastic in the anti-static solder sucker is a type that doesn’t generate static electricity when actuated. The plastic in the regular type probably does. And think about how you use the thing: you put it right at the pin of a device, so for the type that does generate static, the static gets discharged right at the component.“It depends” on the part’s sensitivity to static electricity. Old CMOS parts? Yeah, you’ll probably blow them up. Big bipolar power transistors? Probably not.But when you use one of these things, you are generally uninterested in reusing the chip you are removing. So the zap doesn’t matter. Unless you zap a neighboring device. In which case it does.

author: Tomer
author_rank: Regular Contributor
timestamp: March 23, 2018, 10:28:41 pm
content: Guys, thank you for the replay and help.I was ordering the regular solder sucker and found out they have 25$ minimum on there site(It's not early 2000!! / Very annoying) so i took the static one just to be over 25 and added a ringThanks for the helpTom
Do jbc C210 and C245 use same thermocouple - Page 1
Forum section: electronics / beginners

author: leham
author_rank: Regular Contributor
timestamp: May 25, 2020, 09:53:13 pm
content: I’m looking to buy a JBC clone station but want to know if I can use the smaller C210 tips.The clone station only have single 24v output, where as the original can switch to 12v for the c210 cartridges.Does anyone know if they use the same thermocouples between the two cartridges, if so that would make converting the clone to the lower voltage easier.

author: Ribster
author_rank: Frequent Contributor
timestamp: May 25, 2020, 10:25:42 pm
content: Both have different wiring. One has a short between 2 pins to differentiate between the 2.One has the thermocouple in series, while the c210 has not.Search for yet another jbc controller on here, and you will find a lot

author: thm_w
author_rank: Super Contributor
timestamp: May 25, 2020, 11:25:47 pm
content: Some clone stations support it some do not.Either search for info on that specific clone, or post the details of the model here.I think the jabe does not:https://www.eevblog.com/forum/reviews/jabe-ud-1200-soldering-station-nice-jbc-clone/I think you'd be better off finding something that supports it or building your own. Modifying the clone means you'd have to reverse engineer it to do it properly.
Do larger toroid transformers have fewer secondary turns than smaller ones? - Page 1
Forum section: electronics / beginners

author: julian1
author_rank: Frequent Contributor
timestamp: August 16, 2016, 08:43:02 am
content: Looking at pictures of 300VA versus 160VA toroids on Ebay - and the larger ones appear to use fewer turns on the secondary (and presumably primaries too), for the same output voltage.Obviously the secondary is also a larger gauge and higher current carrying wire.Is this a general rule, and if so does that mean larger toroids would reduce the work required - if one wanted to adapt one by winding on additional secondaries at other voltage outputs.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 16, 2016, 09:19:19 am
content: For a given input voltage and frequency, and the same core material (almost always laminated iron), the number of turns is inversely proportional to the cross section of the core.Tim

author: Audioguru
author_rank: Super Contributor
timestamp: August 16, 2016, 04:14:52 pm
content: A transformer is not perfect, its windings have resistance that causes the secondary voltage to drop with a load. Its rated voltage is when it has its rated load.A large transformer has windings with low resistance so a 12V transformer might have a secondary that produces 13V with no load. A cheap small transformer has high resistance windings so it is made to produce maybe 15V with no load then its secondary has more windings than the larger transformer.

author: Dave
author_rank: Super Contributor
timestamp: August 16, 2016, 06:42:49 pm
content: Well, the peak magnetic flux density (B) in the core of the transformer will mostly be determined by the ferromagnetic material used for the core, but that value is usually going to be between 1.3T and 1.8T.If you compared two different size transformers made with the same core material, used on the same frequency and designed for the same peak flux density (B), then the higher power transformer is going to have a larger cross-section of the core, meaning that the peak magnetic flux is going to be higher, resulting in more volts per turn - meaning you need less turns around the core to achieve the same voltage on the output (exactly what you observed).The wire is naturally going to have to be thicker, because it needs to carry more current, since the bigger transformer is capable of delivering more power.

author: Seekonk
author_rank: Super Contributor
timestamp: August 16, 2016, 07:44:38 pm
content: I gave Tim a STAR just for managing to keep it to one sentence. I know how hard that was.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 16, 2016, 09:01:38 pm
content: Quote from: Seekonk on August 16, 2016, 07:44:38 pmI suspect my posts have an inverse-power law, where the average is "very long" and the outliers are the one-liners...Tim

author: Brumby
author_rank: Unknown
timestamp: August 17, 2016, 12:37:10 am
content: Quote from: T3sl4co1l on August 16, 2016, 09:01:38 pmFeeling rather self-conscious at the moment.....
Do Letter codes on PCBs denote OEMs? If yes how can I look them up? - Page 1
Forum section: electronics / beginners

author: cdev
author_rank: Super Contributor
timestamp: March 28, 2015, 09:28:53 pm
content: Is that common, it seems that on some Chinese origin PCBs especially I have noticed these codes.I am wondering if there is any master registry for these codes or whether they are just informal.
Do Lithium cells use electrolyte?  - Page 1
Forum section: electronics / beginners

author: Cliff Matthews
author_rank: Unknown
timestamp: January 06, 2020, 06:35:34 pm
content: Maybe what's mentioned as electrolyte here (at about 9:30) is some kind of a catalyst, and after spraying it in, all other operations must be done in a vacuum? The rest is quite entertaining but not too technical for non-chemistry folks like me. - Enjoy

author: andy3055
author_rank: Super Contributor
timestamp: January 06, 2020, 07:44:09 pm
content: Here is a nice explanation:https://www.energy.gov/eere/articles/how-does-lithium-ion-battery-workI think one can say that the basic principle is like most rechargeable batteries. Only that there are different elements in the construction. I just saw a nice tear down video from Dave just yesterday.

author: David Hess
author_rank: Super Contributor
timestamp: January 06, 2020, 07:51:02 pm
content: The electrolyte has to be an organic solvent and not water because water will electrolyze at the operating voltage of the cell. Typically the organic solvent is flammable.

author: Cliff Matthews
author_rank: Unknown
timestamp: January 07, 2020, 01:14:41 am
content: Quote from: David Hess on January 06, 2020, 07:51:02 pmSince it's sealed, punctures provide both oxygen and if charged, current enough to ignite the solvent. Funny, when the word electrolyte is mentioned I would always associate it with hygrometers for testing auto batteries..

author: David Hess
author_rank: Super Contributor
timestamp: January 07, 2020, 03:59:18 am
content: I have a word of warning. If you rip a lithium polymer cell apart, the ones in the foil packages, then do *not* get the liquid electrolyte on your skin. I have had strong acid and strong base burns which were not as annoying.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 07, 2020, 04:07:46 am
content: Quote from: Cliff Matthews on January 07, 2020, 01:14:41 am"It's got electrolytes!" [while doing the hand gesture]From the reference movie "Idiocracy" (2006)

author: tszaboo
author_rank: Super Contributor
timestamp: January 07, 2020, 04:56:36 pm
content: Lithium cells have fire in them. That seems to be their base ingredient.

author: mikerj
author_rank: Super Contributor
timestamp: January 07, 2020, 05:34:25 pm
content: Quote from: RoGeorge on January 07, 2020, 04:07:46 amIt's got what batteries crave!

author: Siwastaja
author_rank: Super Contributor
timestamp: January 08, 2020, 09:04:00 am
content: Quote from: NANDBlog on January 07, 2020, 04:56:36 pmExcept some Ebay cells, which use Air, or even Earth (sand) as their main ingredient.
Do LM317 and LM337 SOT-223 Need Ground Plane to Regulate Properly? - Page 1
Forum section: electronics / beginners

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 01, 2012, 10:38:16 am
content: do they? or doesnt matter? its not mentioned in the datasheet, so probably ground plane is not needed/critical. but i would like to hear first hand experience. i have a circuit that run out of space so i cannot place LM317 and LM337 side by side with ground plane below. so what i do is i placed the LM317 above and LM337 directly below on bottom layer, so there will be no ground plane anymore. will this cause regulation performance issue on both +ve and -ve regulator?

author: Rerouter
author_rank: Super Contributor
timestamp: October 01, 2012, 10:55:55 am
content: in that case your more likely to see a little crosstalk between the regulators, but no a ground plane should not be vital, just make sure like the data sheet says you have some capacitance on the feedback pins, as it will minimise the effect,

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 01, 2012, 12:40:20 pm
content: Quote from: Rerouter on October 01, 2012, 10:55:55 amhow bad can it be? maybe it is wiser if i shift the LM337 so it will not be directly below the LM317? including the voltage adjust resistors?
Do magneto-resistive sensors get confused by high strength magnetic fields? - Page 1
Forum section: electronics / beginners

author: e100
author_rank: Frequent Contributor
timestamp: August 09, 2018, 03:59:06 am
content: I have a HMC5883L which gives sensible results when measuring the earth's magnetic field but gives erratic nonsensical behaviour once you have exceeded the 8.1Ga measurement limit and for several seconds afterwards. Is there some sort of recovery time or hysteresis effect?The datasheethttps://cdn-shop.adafruit.com/datasheets/HMC5883L_3-Axis_Digital_Compass_IC.pdfdoesn't say anything and I couldn't find anything on Google that talks about this.
DO MIPI M-PHY needs AC coupling capacitor on its Tx and Rx lanes? - Page 1
Forum section: electronics / beginners

author: muthukural001
author_rank: Regular Contributor
timestamp: May 09, 2019, 05:34:11 am
content: Hello All,I have seen that USB 3.1 and PCIe 3.0 have AC coupling capacitor on its Txp and Txn. But, I want to know that MIPI M-PHY of UFS memory needs that. MIPI CSI that is based on D-PHY does not have AC coupling capacitor on its Tx lane and Rx lane...So, anyone has worked on MIPI M-PHY help me on this?I have one more question, why USB 2.0's D+ and D- lines do not require AC coupling capacitor on them?Thanks,Muthu
Do modern residual current trip devices (RCDs) contain more than just coils? - Page 1
Forum section: electronics / beginners

author: e100
author_rank: Frequent Contributor
timestamp: August 06, 2023, 07:00:04 am
content: A Google image search for "RCD circuit diagram" just gives simplified diagrams with the potentially interesting bits depicted as relays or simply boxes labelled 'electronic circuit'.If they do contain active electronics how do they make something that is expected to be 100% reliable for 30+ years?If the diagrams are to be believed, the electronics are only ever powered up during a fault condition, therefore there is no way of doing a periodic self test.

author: Kleinstein
author_rank: Super Contributor
timestamp: August 06, 2023, 07:09:42 am
content: There are different types. Some contain only passive parts (transformer, special "relais" to release). Others contain electronics - in Germany this are mainly those in extension cables or as an in between plug.The RCD circuit are supposed to be tested regularly.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 06, 2023, 09:33:25 am
content: Mostly electronics AFAIK, a small amount. Example:https://patents.google.com/patent/US5757598A/enI don't know the whole patent history (of this type of device), 1996 looks rather new to me, but I'm sure similar things can be found going back a bit further.And yep, they are generally quite reliable. It's a simple function, made from robust parts, and not subject to much heat (except when it fails to operate, in which case, replacement is likely..).The TEST button generally wires a resistor between lines, through the current transformer(s), so that it's literally testing at rated current. Electronics are always active and ready to fire. (What happens to that resistor when it fails to operate? Well, it gets hot...)Tim

author: gf
author_rank: Super Contributor
timestamp: August 06, 2023, 09:57:29 am
content: In some countries (e.g. Germany), the standards require certain types of RCDs to trip independently of the presence of mains voltage (at least for AC residual currents) - this rules out purely electronic devices.

author: Jeroen3
author_rank: Super Contributor
timestamp: August 06, 2023, 01:22:28 pm
content: Quote from: e100 on August 06, 2023, 07:00:04 amThey don't, you're supposed to test them monthly and have them measured every 1 to 5 years, depending on the circuit they're on.

author: MathWizard
author_rank: Super Contributor
timestamp: August 06, 2023, 07:27:17 pm
content: The GFD plugs in my house trip, just from plugging a vacuum cleaner into it, turned off. IDK if that's some inductive effects, or insulation leakage, etc.
Do multiplexers for photodiode arrays exist?  - Page 1
Forum section: electronics / beginners

author: e100
author_rank: Frequent Contributor
timestamp: September 30, 2016, 04:29:52 pm
content: A Google search turned very little.Are analogue switches too leaky.Are mechanical/reed switches the only viable option?Mike

author: Kleinstein
author_rank: Super Contributor
timestamp: September 30, 2016, 04:54:24 pm
content: CCD detectors are a kind of mulitplexer for photodiode arrays.It depends on the current levels how much leakage you get, you just can not have very low on resistance and low leakage at the same time. So in principle CMOS switches could work with photo-diode arrays.There are some switched intergrators to measure very small photo-currents - so there are really low leakage semicondctor switches (could be JFET or MOS). However the chips I know are rather expensive.

author: Marco
author_rank: Super Contributor
timestamp: September 30, 2016, 05:03:31 pm
content: Just use a FET with sufficient (or some extra) capacitance. The current will go into the capacitor instead of leaking through it.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 30, 2016, 06:43:09 pm
content: Any device that performs "current steering" will do. Assuming you don't need current integration right at the diode (which is what the CCD does: the integration is always in progress, with a sample-and-reset event every so often when you scan it).A differential pair (using BJTs or FETs) can be generalized into a 1-of-N selector. Drive the selected base/gate with logic high (assuming NPN/Nch and a sinking current tied to the common emitters/sources), and the others low. (A standard e.g. 74HC238 will perform the 1-of-N selection.) The current will be drawn through the respective collector/drain terminal.An example application would be a tuned circuit on each output terminal, so that only radio signals that match up in frequency and in phase with the selector get detected. Using a 1-of-4 counter/decoder, the outputs will be selected sequentially, in quadrature; if opposite pairs (0 and 2, 1 and 3) are linked to balanced tuned circuits, you have a synchronous quadrature detector!Tim

author: Silverio
author_rank: Newbie
timestamp: October 06, 2016, 12:44:09 am
content: The key with photodiodes is to convert the current generated to voltage properly. Usually some amplification is done at the same time. In the past I've had some success using CMOS analog multiplexers for switching the signal coming from an opamp that converts the photodiode current to voltage.
Do slow op amps filter out noise? - Page 1
Forum section: electronics / beginners

author: AQUAMAN
author_rank: Regular Contributor
timestamp: May 21, 2021, 09:04:39 pm
content: If I have an op amp with a BW of 5khz into an ADC, will that op amp filter out noise at say 1Mhz?

author: penfold
author_rank: Frequent Contributor
timestamp: May 21, 2021, 09:58:11 pm
content: The short answer is generally yes. But I wouldn't rely on that as an excuse not to filter out noise as early as you can in the signal chain. There are still ways in which HF noise can be troublesome and ways that parasitic elements of the resistors can cause the gain to increase slightly at HF... but whether that is a problem to your circuit is rather circumstantial.

author: Vovk_Z
author_rank: Super Contributor
timestamp: May 22, 2021, 02:59:47 am
content: Yes and no. It depends. :-)

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 22, 2021, 06:57:16 am
content: Opamps can rectify high frequencies. Classic example is old bipolar amps like LM358, in the presence of frequencies over 100MHz (probably over 10MHz even). The input stage acts like a diode into a capacitor, rectifying RF. Thus, RF adds to the signal like a voltage offset.JFET and moreso MOSFET types are less prone, and many precision amps these days have some manner of internal filtering, which the datasheet reports (immunity at fractional GHz and up).The best idea is always to filter your signal down to only what's needed.Tim

author: David Hess
author_rank: Super Contributor
timestamp: May 23, 2021, 01:41:08 am
content: Limiting operational amplifier bandwidth limits noise, and some amplifiers, like the LT1097, give access to an "overcompensation" pin which allows this.
Do SSR require current limiting in some fashion? - Page 1
Forum section: electronics / beginners

author: ryanmills
author_rank: Unknown
timestamp: July 10, 2019, 05:29:34 pm
content: I'm pretty sure the answer is no. But I just made some real basic stupid mistakes and before I move on I wanted to give some EE's a chance to use the RTFM emoji.Do solid state relays with a MOSFET (specifically PhotoMOS AQY211EHAX) output require any current limiting on the output? My first setup was with an LED and obviously it needed a current limiting resistor. However i'm also going to drive an incandescent bulb and a small DC motor. I assume its just going to be like driving anything else regular MOSFET?

author: MagicSmoker
author_rank: Super Contributor
timestamp: July 10, 2019, 06:10:52 pm
content: Unless the datasheet says it is fully protected against shorts, overcurrent, overtemperature, etc., then assume current limiting is up to you.EDIT - I checked that datasheet for you and it is not protected.

author: ejeffrey
author_rank: Super Contributor
timestamp: July 10, 2019, 06:14:16 pm
content: Nothing special. If you are running off of mains or any other circuit capable of delivering massive current into a fault you need a fuse. Solid state relays tend to fail short circuit rather than open -- if a failed short is hazardous you need some ability to do a safety cutout -- for instance if you are controlling a heating element you might want a thermal fuse.They are MOSFETs, so they are more susceptible to transient overvoltage compared to mechanical relays or TRIACs. When interrupting an inductive load you will want snubbers, just as with any other MOSFET.

author: ryanmills
author_rank: Unknown
timestamp: July 10, 2019, 09:50:59 pm
content: Thank you, just feeling like an idiot today and wanted to check.

author: Zero999
author_rank: Super Contributor
timestamp: July 11, 2019, 08:08:42 am
content: Quote from: ryanmills on July 10, 2019, 05:29:34 pmMake sure the relay can pass enough current to drive the load and it will be fine. The load resistance will limit the current to a safe level.If you're asking about protecting the SSR from faults, then the only thing which can offer any kind of protection is an electronic overcurrent protection circuit. A fuse, circuit or PTC resistor will be far too slow to protect a solid state relay from damage, due to the load drawing too much current.Finally, the input of the AQY211EHAX and many solid state relays is just an LED, which of course needs a current limiting resistor.
Do these caps appear authentic? - Page 1
Forum section: electronics / beginners

author: OpenCircuit
author_rank: Regular Contributor
timestamp: September 24, 2025, 12:23:00 am
content: Needing to replace some caps on an old XBOX console. Thankshttps://www.amazon.com/Nichicon-3300uf-Capacitor-Radial-Leads/dp/B01DYJERPC?crid=16L14NCPR7RZ0&dib=eyJ2IjoiMSJ9.vYrWDyS9ytI-EEqxB4icO_md8XvzkXjbeX2jWHPMt7XrgvwqFnUc8x0h5ob3lXhqsboJPL88Cgoqk9ksMurYuk17XuKEGNIcPD2Hvj1nzDv6kz7fExN2xAp6gsohcJMH2X8nVGHxASuV8wSiwy1VkT61j3aDAkDRGVM608Nc8Cz3-Ggj23TwpadLQ37uQRzmPk-yrhymEs1GbKdu-o8xBOL7Y51WUO4f4P-ywT0TMyA.Y6-OK2zgri0adQsZWlmdadEneMsgVmPBf0bbREJ7y6k&dib_tag=se&keywords=Nichicon+3300uf+10v+Capacitor&qid=1758671785&sprefix=nichicon+3300uf+10v+capacitor%2Caps%2C173&sr=8-1

author: MrAl
author_rank: Super Contributor
timestamp: September 24, 2025, 09:49:03 am
content: Quote from: OpenCircuit on September 24, 2025, 12:23:00 amHi,This may or may not help, but you can always test a few to see that they are up to specs. I'd say a lot of electrolytics can vary but probably not more than 10 or 20 percent. You'd have to test for capacitance, ESR, and leakage current at the rated voltage or just under that. You might test for ESL too if you are up to it.

author: wraper
author_rank: Unknown
timestamp: September 24, 2025, 10:03:08 am
content: Not suitable even if genuine. You need low ESR series.

author: ahsrabrifat
author_rank: Regular Contributor
timestamp: September 27, 2025, 02:35:18 pm
content: If you want to use it as a substitute, compare physical size/dimensions. Check ESR specs (lower is generally better for power circuits). Verify that the lead spacing and orientation suit your board
do transistors need a reverse current protection?? - Page 1
Forum section: electronics / beginners

author: Adhith
author_rank: Frequent Contributor
timestamp: October 19, 2017, 06:29:23 pm
content: hello everyone..I'm having a doubt regarding transistors. Suppose I'm trying to light up a 12v LED strip by switching a transistor (BJT) with a signal also, the same strip is powered by switching another transistor with a separate signal. So in this case if at an instinct only one transistor is switched on then, is there any possible chance of damaging the other transistor with the reverse current and should I avoid it by placing a diode??

author: wraper
author_rank: Unknown
timestamp: October 19, 2017, 06:53:26 pm
content: Do you mean 2 transistors in parallel with each having it's base controlled separately?

author: Adhith
author_rank: Frequent Contributor
timestamp: October 21, 2017, 02:08:41 pm
content: Quote from: wraper on October 19, 2017, 06:53:26 pmYes that is what i meant. I think its an OR gate right??

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 21, 2017, 10:15:24 pm
content: That is called wired-OR, yes.To be perfectly correct, it's wired-OR when the inputs are positive logic and the output is negative logic; otherwise, it's wired-NOR (all positive logic) or wired-NAND (all negative logic). These are just Boolean identities (read more about the subject, and reason it out -- all will become clear.)There is no reverse current, because neither transistor is driven to negative voltage in the process. If a transistor were voltage-output, it would; but it's not, so it doesn't.Tim

author: Adhith
author_rank: Frequent Contributor
timestamp: October 22, 2017, 04:26:13 pm
content: Quote from: T3sl4co1l on October 21, 2017, 10:15:24 pmThank you very much T3sl4co1l for your suggestion. let me check on Boolean identities to get a more clear picture.
Do you forget to connect power and or probes, and then wonder whats wrong ? - Page 1
Forum section: electronics / beginners

author: lordvader88
author_rank: Frequent Contributor
timestamp: September 16, 2017, 03:39:25 am
content: All too often I'll forget to re-connect a ground wire to something, and then wonder....now whats wrongReminds me off forgetfulness...like forgetting to take the cap off the camera, or opening a window before shooting

author: Electro Detective
author_rank: Super Contributor
timestamp: September 16, 2017, 03:52:07 am
content: Overconfidence ?in a hurry for circuit satisfaction (aka please work!),in a big hurry to finish and move on to the next project,too many drinks last night,a poor memory or needs a defrag,the phone rings...Distracted by noisy irritated Saturniansdumping crashed Cassini parts in the drivewayWelcome to 'what's wrong?' Snafu in electronics

author: Assafl
author_rank: Frequent Contributor
timestamp: September 16, 2017, 08:21:16 am
content: I have the solution.Build a really good power amplifier. Using the expensive Motorola output devices. Given the carelessness, you'll fry the output devices.Buy new ones, fry them again.Pretty soon you'll start paying attention.

author: bd139
author_rank: Super Contributor
timestamp: September 16, 2017, 08:52:09 am
content: Regularly! I spent half an hour last night trying to work out why my filter's insertion loss was -40dB rather than the expected -0.5dB. Turns out I had connected the breadboard's -V to the earth binding post rather than the negative one on the power supply. The entire signal was coming via the feedback loop hence the fact it was actually registering something. The power consumption of the circuit is so little that it doesn't register on my bench supply's current meter.
Do you know of a 4  digit 7 segment display that work on 3.3v? - Page 1
Forum section: electronics / beginners

author: Ram80
author_rank: Contributor
timestamp: July 18, 2024, 04:55:37 pm
content: I need a 4 digit 7 segment display that runs off a coin battery , 3.3v from jlcpcb , do you know of such a display?

author: JustMeHere
author_rank: Frequent Contributor
timestamp: July 18, 2024, 05:18:47 pm
content: There should be plenty out there. Digital watches have been around for 50 years now. If you're using a coin battery, you will need to use LCD and not LED.

author: Gyro
author_rank: Super Contributor
timestamp: July 18, 2024, 05:21:24 pm
content: The first thing you need to do is look at the capacity, acceptable current, and discharge voltage curve of the coin cell. Gut feel is that you're not going to get any significant operating time. I suspect that you're more in LCD territory.You really need to provide more detail before anyone can help. What sort of display are you looking for? The number of single dumb 7 segment displays is almost endless (you are shooting yourself in the foot a bit by looking for a 4 digit one). Are you looking for something with a built-in decoder of some sort, or one that you will multiplex drive from microcontroller pins?Edit: Sorry, my brain read LED for some reason. Reading your other posts, it looks as if they may all related to a single project. It would be helpful if you kept them all in one thread to allow people to understand the context.
Do you layout to reduce stencil size or spread out parts? - Page 1
Forum section: electronics / beginners

author: alank2
author_rank: Super Contributor
timestamp: June 25, 2015, 11:59:28 am
content: I'm working on my second SMT pcb and the pcb because of a few parts that need to be in specific places is quite a bit larger than the parts going onto it, roughly 100 mm x 90 mm. My question is, is it easier from a stencil perspective to try to fit all the stenciled parts in a smaller area, or spread them out over the larger area of the pcb? Any thoughts?

author: m98
author_rank: Frequent Contributor
timestamp: June 25, 2015, 10:00:48 pm
content: That depends on your design requirements. But why should it make a difference for the stencil how you place the parts?

author: H.O
author_rank: Frequent Contributor
timestamp: June 26, 2015, 05:18:16 am
content: Theoretically, a rotational misallignment of the stencil of x degrees makes the problem worse on a big board compared to a small. Of course, in practice you just tweak it untill it's "spot on". I wouldn't let that aspect "drive" the part placement.

author: zapta
author_rank: Super Contributor
timestamp: June 26, 2015, 05:31:53 am
content: If the stencil costs you by area (e.g. oshstencil.com) then smaller = less expensive.

author: Muxr
author_rank: Super Contributor
timestamp: June 26, 2015, 06:37:04 am
content: There are so many other factors that i find more important when placing parts than to worry about the stencil size. I spend so much time worrying about not painting myself into a corner leaving room for modification on a working design, efficient manufacturability, mechanical design, interferences, stray capacitance, the length of traces and also the board size as the cost cutting measure that the stencil size doesn't even enter the list of concerns.Considering that it's usually a one time fee, I wouldn't worry too much about it.
Do you recognize this circuit? - Page 1
Forum section: electronics / beginners

author: OlivierNum
author_rank: Newbie
timestamp: May 29, 2013, 01:28:23 pm
content: Hi,I have some problem identifying this circuit. What it does is when I apply a frequency of 50% duty cycle on the input, I can modify the duty cycle changing the R3 (or the cap value).Do you know the name of this circuit?Thanks

author: Paul Price
author_rank: Super Contributor
timestamp: May 29, 2013, 01:54:24 pm
content: You can also change the duty cycle by changing R72 or R1. I would call this circuit a duty-cycle modifier circuit.

author: Rufus
author_rank: Super Contributor
timestamp: May 29, 2013, 02:58:48 pm
content: What I would call it is a completely shit drawing.After re-drawing it it becomes recognizable as some kind of pulse stretcher. It delays rising edges by about 100us and falling edges by about 2ms.

author: OlivierNum
author_rank: Newbie
timestamp: May 29, 2013, 03:06:08 pm
content: Yeah thanks for the compliment...Care to upload an awesome drawing of yours?

author: c4757p
author_rank: Super Contributor
timestamp: May 29, 2013, 03:29:49 pm
content: Quote from: OlivierNum on May 29, 2013, 03:06:08 pmWell, the way you draw a circuit is important for being able to recognize the parts. How's this? Now you can see all the RC relationships and the signal path - the signal charges C4 through R3->D4A, discharges C4 through R72, is pulled up by R1 in the absence of a signal input, and is clamped to VDD by D4B.Excuse the wrong diode symbol and the wrong name for the rail...(Edit: fixed)If I were drawing this into a full, proper schematic, I'd go one step further and annotate it with the voltage thresholds and the expressions for the delay constants.Also, for noise immunity (and depending on how well the power rail is decoupled), I'd reroute C4 to ground instead of VDD. Won't make a difference at all in operation. Otherwise you're AC-coupling any power supply noise into the signal. Of course, a Schmitt inverter won't be too susceptible to that.

author: OlivierNum
author_rank: Newbie
timestamp: May 29, 2013, 03:45:27 pm
content: Thanks!

author: Rufus
author_rank: Super Contributor
timestamp: May 29, 2013, 04:22:59 pm
content: Quote from: OlivierNum on May 29, 2013, 03:06:08 pmThe scribble on my pad looks like this:

author: oPossum
author_rank: Super Contributor
timestamp: May 29, 2013, 04:46:50 pm
content: It's missing a ground node.

author: c4757p
author_rank: Super Contributor
timestamp: May 29, 2013, 05:02:58 pm
content: Possibly, but as far as I can tell without seeing the schematic, it makes sense as it is. Besides, then R1 and R3 don't really make much sense, unless the signal input was AC coupled. No point in bias resistors on a DC coupled signal.

author: MrsR
author_rank: Regular Contributor
timestamp: May 29, 2013, 05:21:33 pm
content: You took the circuit from the board and that is what you do when debugging a circuit, Draw the circuit you are working on then move onto the next section untill you find the fault that is what all good Techs. do if they don't have a schematic to work from.ALL THE BESTRachael
Do you see any corrosion here? - Page 1
Forum section: electronics / beginners

author: isthiscorrosion
author_rank: Newbie
timestamp: June 15, 2023, 04:54:35 pm
content: Apple claims there's water damage. I claim there isn't. They say there's corrosion. Do you see it in the world's worst photo they supplied? Thanks so much!This is a link to the photo and I've attached it as well:

author: tooki
author_rank: Super Contributor
timestamp: June 15, 2023, 07:42:59 pm
content: The photo does suck, but yes, that does look very much like the water damage I’ve seen in modern devices (including Apple ones). The DC power causes rapid electrolytic corrosion, way more than you might imagine.

author: jpanhalt
author_rank: Super Contributor
timestamp: June 15, 2023, 07:50:26 pm
content: What's your point? Regardless of what an army or anonymous contributors say, Apple has the last say. Do you think you can sue Apple on that basis?There are other avenues to get satisfaction from Apple. Have you explored them? Before doing anything, read your contract with Apple. Recently, I had an issue with Verizon. As I studied my options, I chose one. Verizon agreed with my logic and refunded me -- even slightly more than my estimate.
do you think tms28f512 eeprom is OTP ? ( READ ONLY ) ?? - Page 1
Forum section: electronics / beginners

author: fadyeid
author_rank: Contributor
timestamp: May 27, 2017, 09:48:18 am
content: I have got 10 pcs of eeprom 28f512 I cant flash them I could read ok but when trry to write gives errors to verifyI use tl866 programmer alsois it read only ?

author: danadak
author_rank: Super Contributor
timestamp: May 27, 2017, 11:32:15 am
content: Looks like a standard flash memory, 10K erase/program cycles.http://html.alldatasheet.com/html-pdf/55446/AMD/AM28F512/47/1/AM28F512.htmlRegards, Dana.
Do you use concave or convex resistor arrays and why? - Page 1
Forum section: electronics / beginners

author: alank2
author_rank: Super Contributor
timestamp: August 25, 2014, 12:08:22 pm
content: Do you use concave or convex resistor arrays and why?

author: AlfBaz
author_rank: Super Contributor
timestamp: August 25, 2014, 01:42:29 pm
content: I had no idea those terms even existedThe first 2hits on googleseem to suggest convex has manufacturability and inspection advantages that the concave don't

author: charlespax
author_rank: Regular Contributor
timestamp: August 25, 2014, 04:40:36 pm
content: Here's aconvex vs. concave resistor array comparison(PDF).Summary of convex resistor array advantages:- 5-sided vs. 3 sided termination gives better solderability- Larger gap between terminations reduces solder bridging- Better view for visual inspection- Larger terminations increase reflow soldering self-alignment- Better part availability (70% of market)- Lower cost in generalI'm not sure if concave resistor arrays have any advantages. My guess is if you have an application where a concave resistor array is better, you would already know it.