hybridfree/eevblog-posts huggingface dataset:
Capacitance multiplier - do I need to protect the NPN using a diode? - Page 1
Forum section: electronics / projects

author: humbug11
author_rank: Newbie
timestamp: March 01, 2018, 06:49:08 pm
content: Hi,I'm experimenting with using a capacitance multiplier as a noise filter. It seems to work rather well, but one thing that I'm not sure about is if it is necessary to protect the NPN transistor from negative Emitter-Collector voltages. According to the DS, the maximum Emitter-Base voltage is 6V, which will be exceeded when removing the battery or if there is a large negative "spike" on "+Batt". However, only very little current can flow in these situations, as the total capacitance on the "V_BATT_FILT" net is in the order of 10uF.Will removing the battery or negative spikes damage the NPN transistor over time and is it necessary to protect it using a diode? If so, what diode would be best? Ideally, it should start conducting at a few volts in forward direction and the reverse voltage should be in the order of 40V.

author: Paul Price
author_rank: Super Contributor
timestamp: March 01, 2018, 11:12:43 pm
content: Adding a series >40V rated schottky diode to the +Bat input would protect this circuit from negative spikes and add only a minimal voltage drop. Anode of diode to +BAT

author: langwadt
author_rank: Super Contributor
timestamp: March 02, 2018, 12:17:24 am
content: NOTE: This message has been deleted by the forum moderator Simon for being against the forum rules and/or at the discretion of the moderator as being in the best interests of the forum community and the nature of the thread.If you believe this to be in error, please contact the moderator involved.An optional additional explanation is:

author: iMo
author_rank: Super Contributor
timestamp: March 02, 2018, 01:14:13 am
content: This seems to protect the npn transistor best.The diodes and transistor types an example only.Provided as-is, no warranties of any kind are provided

author: David Hess
author_rank: Super Contributor
timestamp: March 02, 2018, 12:00:45 pm
content: The capacitance you are multiplying can only discharge through the base-collector junction if the input voltage is removed which has the characteristics of a diode with a rating of the Ic (collector current) and Vcbo (collector-base breakdown voltage) of the transistor so it is very unlikely to be damaged. Collector-base junctions of transistors are sometimes used as high performance power diodes.The base-emitter junction is a different matter and is often protected by an anti-parallel diode between the base and emitter leads or base and collector leads. In a power transistor the base-emitter junction can actually sustain considerable reverse breakdown current without affecting the circuit however the high power resulting from the relatively high breakdown voltage can lead to thermal damage.
Capacitance on Fluke 17B - Page 1
Forum section: electronics / projects

author: grc
author_rank: Newbie
timestamp: May 08, 2011, 06:48:03 pm
content: Looking at the spec for capacitance they state "Capacitance : 0.01nF to 100uF" by under specs "Capacitance : 50nF / 200nF / 2uF / 20uF / 200uF / 20mF , +/-2% +5" Can you measure 20,000 ufd(20 mf) or 100 ufd?ThanksGeoff

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: May 08, 2011, 07:12:41 pm
content: It is advisable to post the link that you found the specs.Some information are about the display resolution, and others about the true measured values.

author: CoolBeer
author_rank: Newbie
timestamp: May 20, 2011, 07:19:36 am
content: It's 100uF, and with the tolerances on electrolytics being -20%+80%(on some), you could be unable to measure 100uF ones.
Capacitive feedback in TL497 inverter circuit - Page 1
Forum section: electronics / projects

author: guymo
author_rank: Regular Contributor
timestamp: October 03, 2018, 10:59:14 am
content: I'm looking at an old device (Pearl Syncussion percussion synthesizer) which uses a TL497 to generate a -8V power supply. Some recent clone versions of this have experienced problems with the TL497 becoming very hot and I'm trying to figure out why.The original schematic (attached) has a capacitor (C34) between the comparator input and the collector of the switching transistor and I am trying to figure out the impact of that. The TI app notehttp://www.ti.com/lit/an/slva143/slva143.pdfis very insistent that the voltage at the collector ought to be a sharp pulse wave, which seems unlikely with this cap in place. The same app note suggests using a diode for feedback to clamp the comparator input during the on-cycle -- schematic attached. It seems to me that using a cap in place of that diode will make matters worse rather than better.What purpose does that capacitor serve, and would life be better with a diode there as suggested in the app note?A related question: the datasheets suggest that one should not use the internal diode as a flyback when the device is employed in an inverting configuration; an external diode should be used instead. Any idea why?[If this belongs in Beginners please accept my apologies! I thought it was perhaps a little too technical for that.]
Capacitive  Power Supply - Page 1
Forum section: electronics / projects

author: Adwaittronics
author_rank: Newbie
timestamp: April 01, 2017, 05:35:57 am
content: HiI want to design a capacitive power supply , with i/p voltage as 90V to 270V and o/p voltage as 24V , how can I calculate maximum current of the circuit?I calculated the capacitance of the X-rated capacitor by the formula X = 1/(2* pi*f*C) where f=50-60Hz.Then calculated the current by the formula I = V/X , where V is the input voltage.Is this the correct way to calculate maximum current of the circuit ?In all the above calculation output voltage is not in picture , so am I right or wrong kindly explain.NOTE : for all the i/p voltages from 90V to 270V ,I want the o/p voltage to be 24V.

author: bitwelder
author_rank: Super Contributor
timestamp: April 01, 2017, 07:16:20 am
content: As that circuit will be exposed (and will expose you) to live mains, would you mind to explain a bit what do you want to use it for?

author: Adwaittronics
author_rank: Newbie
timestamp: April 15, 2017, 10:54:32 am
content: Quote from: Adwaittronics on April 01, 2017, 05:35:57 amCan anyone provide full bridge capacitive power supply circuit and how to apply KVL and KCL to it during positive half cycle to deduce voltage and current values?

author: Zero999
author_rank: Super Contributor
timestamp: April 15, 2017, 12:49:16 pm
content: Microchip made an application note about this awhile ago:http://ww1.microchip.com/downloads/en/AppNotes/00954A.pdfHow much current do you need?

author: Benta
author_rank: Super Contributor
timestamp: April 15, 2017, 06:54:41 pm
content: It's not hard to design, but with realistic capacitor values the max. output current is below 20 mA.
capacitive power transfer - Page 1
Forum section: electronics / projects

author: jmole
author_rank: Regular Contributor
timestamp: November 26, 2013, 04:33:17 am
content: was thinking about this conceptually, but figured I'd ask a wider audience.Is is possible to power an LED (at 5mA or so) with a capacitively coupled, single-ended signal? I.E., could you run one wire to a chip with some rectification/filtering circuitry and LED, and power it?

author: ejeffrey
author_rank: Super Contributor
timestamp: November 26, 2013, 05:25:07 am
content: Capacitively coupled, yes. Without a return path? No.

author: pinkysbrein
author_rank: Contributor
timestamp: November 26, 2013, 02:08:36 pm
content: You could use parasitic capacitance to ground as the return path(ie. Attach a large piece of metal to the other side of the LEDs, you need 2 because the current is AC.)

author: IanB
author_rank: Super Contributor
timestamp: November 26, 2013, 09:44:40 pm
content: Yes, you could in theory, but you would be getting into borderline RF territory.At "low" frequencies, I don't think a single ended (one wire) path would get you anywhere close to the kind of delivered power (5 mA through an LED) you are asking for.As far as "run one wire to a chip with some rectification/filtering circuitry and LED, and power it" -- no, not unless you create a secondary two wire power supply for the chip and LED system tapped off the one wire power supply.Why did you want to do this? I think the reason you don't see it in practice is because there are simpler and more practical engineering solutions to the problem of an isolated power supply.To visualize how such a circuit might work, consider the antenna section of a radio receiver. The antenna couples an AC signal into a coil, and an output signal is tapped off that coil, filtered, detected and amplified. However the antenna signal is tiny and delivers very little power.If you took the same basic circuit and coupled the AC signal into the "antenna" through a capacitor rather than by radio waves you could get the result you are looking for. But I think it would be cumbersome and inefficient.

author: Zero999
author_rank: Super Contributor
timestamp: December 09, 2013, 04:59:16 pm
content: Connect a Schottky diode in reverse parallel with the LED and you have a very simple voltage doubler.
Capacitive sensor guard traces - Page 1
Forum section: electronics / projects

author: carnaval
author_rank: Newbie
timestamp: October 01, 2019, 08:33:16 pm
content: Hey folksI'm trying to design a capacitive displacement sensor for fun and I have a couple questions related to guard electrodes.The setup is quite standard, there are two PCBs that are moving wrt each other. The top board has all the electronics and is measuring the capacitive coupling between two copper fills (see schematic).Now, for this to work I want the capacitance formed by the two electrodes to be proportional (as much as possible) to their area of overlap. My understanding is that it's a good idea to add guard traces to avoid boundary effects and get some noise shielding.For the top board I can directly connect the guards to a low impedance reference potential (ground), however I'm not sure what I should be doing for the bottom board.Since it's moving around, it has no direct connection to the main circuit (the signal is sent back through another pair of electrodes with a constant overlap that are not on the schematic).So I see only a couple options :- Don't put guards around the bottom electrode, but it seems to me that I would get boundary effects (for example on the right in the drawing)- Have a "ground electrode" on both boards facing each other and connect the bottom guards to that, however the coupling between them would only be a couple pF at most and it would require reducing the area of everything else. That would make the whole thing more sensitive to noise.- Something I'm overlooking ?I'm also wondering about having a "ground" plane on the bottom side of the bottom board. Sounds good in principle for shielding but wouldn't it make thing worse if its only connection to the circuit ground was through a ~5pF capacitance ?I have to admit that I'm a bit in over my head with all this. I've been trying to get a better feel for it using field solvers but it's either quite a hassle or expensive ;-)

author: carnaval
author_rank: Newbie
timestamp: October 05, 2019, 04:07:51 pm
content: For example in this picture (from some paper) I don't understand to what potential you would connect the guard electrodes on the rotor.It seems to me that if you leave them floating they would just act as parasitic capacitance and spread the signal around.

author: glentek
author_rank: Regular Contributor
timestamp: October 06, 2019, 08:46:28 pm
content: These application notes might help you:http://www.ti.com/lit/pdf/snoa927http://www.ti.com/lit/an/snoa928a/snoa928a.pdfhttp://www.ti.com/lit/ug/tidu736a/tidu736a.pdf
Capacitive Touch LCD Question - Page 1
Forum section: electronics / projects

author: bobbbyyy
author_rank: Newbie
timestamp: July 25, 2013, 09:52:49 am
content: Hello,A project I'm involved in requires an LCD panel with touch capability. The design requires a screen size ranging from 2.4 inches to 3.5 inches across.The problem is that all of the screens I've been able to find on the internet use resistive touch instead of capacitive.Since most modern touch screens use capacitive technology, is anyone familiar with any TFT LCDs that come with capacitive touch sensors?Thanks

author: Short Circuit
author_rank: Frequent Contributor
timestamp: July 25, 2013, 11:37:23 am
content: Here's one that is easily availablehttp://www.newhavendisplay.com/capacitive-touch-tft-nhd35320240mfatxlctp1-p-5204.html
Capacitive touch panel - Page 1
Forum section: electronics / projects

author: metRo_
author_rank: Regular Contributor
timestamp: November 13, 2013, 01:52:42 am
content: Hi,Why can't I find capacitive touch panel for lcd of 3 or 4 inch size? i seach for capacitive touch panel on ebay, should I use other term?Thank you

author: codeboy2k
author_rank: Super Contributor
timestamp: November 13, 2013, 02:09:51 pm
content: are you looking for just the panel? it's easy to find many complete LCD displays and touch panels for iphone, samsung etc.If you're looking for just the capacitive overlay, it's harder because of the "noise" to you, of all the phone LCD replacements with capacitive panels.use the - operator...i.e. search for "capacitive panel -samsung -iphone -att " and keep adding -WORD to narrow it down.

author: metRo_
author_rank: Regular Contributor
timestamp: November 13, 2013, 10:30:54 pm
content: I was thinking about the noise too and that should be the main reason to not have to many touch capacitive panels.

author: Gall
author_rank: Frequent Contributor
timestamp: November 14, 2013, 02:36:39 pm
content: Try to get a replacement touchscreen for some kind of Chinese tablet or smartphone. Many of them are I2C. I can recommend a 7'' one (Teclast P76Ti replacement touch panel, "narrow" connector variation) but smaller glasses do exist, too. Search them at aliexpress.com.
capacitive touch PCB design - Page 1
Forum section: electronics / projects

author: PerranOak
author_rank: Frequent Contributor
timestamp: September 12, 2021, 04:19:33 pm
content: I want to incorporate a capacitive touch sensor as part of my PCB design. I want it to be constructed entirely from the traces on the PCB and not an actual component. I use easyEDA that is on the JLCPCB site.I don't want to map-out the traces myself but would rather use a design that's already done.However, when I search on the site I can find nothing. To be honest, I don't even really know what to call it and so can't search properly.Are there typical designs around that I may be able to import into easyEDA?Cheers.
Capacitive touch sensor on a dense 4 layer pcb - Page 1
Forum section: electronics / projects

author: Unknown
author_rank: Unknown
timestamp: November 26, 2015, 02:00:45 pm
content: Hi,In a project i'm designing i have a pcb in an ABS case 45x45x20mmm with 3mm tick walls and because the case is water proof i have to use two capacitive touch sensor on the top side as user interface.I've never implemented a touch interface and after reading some docs i have some doubt.My pcb is 4 layer and i was thinking of using separate ICs to read the sensors.The doubts that i have are:1) what pcb stack-up should i use?a doc by microchip suggests:• Layer 1 (top): Capacitive sensor pads.• Layer 2: Capacitive sensor traces.• Layer 3: GND plane, except under capacitivesensor pads. Every effort should be made to keepthis ground plane contiguous. This is especiallytrue for the area under the capacitive sensingcontroller.• Layer 4 (bottom): All components, any LED signaltraces, power traces, and communication traces.All the breakout boards that i have seen have an hatched ground under the sensors, example:http://www.adafruit.com/products/1375.I was thinking this stack up:• Layer 1 (top): Capacitive sensor pads.• Layer 2: GND plane, hatched under the sensor pads• Layer 3: Power traces• Layer 4 (bottom): All components, signal traces and the sensors IC that like the breakout that i linkedare very close to the via connected to the sensor pads.2) For space constraint i have to put other traces and components (ideally only the sensors IC) on layer 4 under the sensors. Is this a "deal breaker"?Sorry for the long topic and bad english.Thanks for the help.
Capacitive touch under silicone near LED array? - Page 1
Forum section: electronics / projects

author: clem
author_rank: Newbie
timestamp: July 17, 2014, 05:02:32 am
content: I'm working on a project that need a simple touch interface. Minimally a single touch, but I'd prefer to be able to detect a left swipe, right swipe and a tap.The design has a silicone overmold, a plastic support frame and a rigid-flex PCB. The rigid-flex PCB has a discrete LED display and the touch sensing region needs to be above the LED display. I had hoped to rely on an accelerometer to provide tap/tilt user input, but a touch interface would be preferred.There isn't much room between the LEDs to put capacitive touch interface between the pixels. One thought is to put an ITO/PET film above the display, so the stack would be silicone overmold, PET film, flex PCB, plastic mechanical support. It appears that the dielectric is suitable for capacitive touch, so that shouldn't be a problem.The big issue is trying to put a capacitive sensors in close proximity to the LEDs. I'm driving the LEDs using several AMS AS1130 crossplex LED drivers. This driver sinks one of its outputs and then sources or floats the other 11. It relies on being able to reverse bias the LEDs to get 12*11 LEDs with only 12 pins. As the LEDs are PWMed they will be changing capacitance which is an issue for the touch controller. An atmel app notehttp://www.atmel.com/Images/doc10752.pdfsays that you can bypass the LEDs with ~1nF to provide a low impedance path as seen by the sensor. Adding a small bypass cap on each of the driver outputs would be reasonable, but it is unclear to me if this is sufficient.Another option is a resitive touch interface, but I'd rather avoid having to pull gestures from x,y data and I'd assume that the restive touchscreen would be more expensive.Any ideas on how best to tackle this problem? Has anyone tried something like this?
Capacitor and Inductor Types and Tolerances - Page 1
Forum section: electronics / projects

author: bentx0rx0
author_rank: Contributor
timestamp: March 16, 2014, 06:12:15 am
content: I'm looking for a 68uF capacitor(preferably nonpolar) with a 5% tolerance, 200nF and 300nF with 5% tolerances, and inductors in the 8uH range with a +/- 0.1 uH range. They're requested in an IEE standard, but I can't find anything with close to that level of tolerance on mouser or digikey(5% v 20%). Is that a totally unrealistic tolerance to expect, or am I just missing them someplance. Electrolytic, Ceramic, Tantalum, I couldn't find anythingThey'll be operating in a power supply. Simulations seem to indicate that it won't matter, but I am curious why they included those values

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: March 16, 2014, 12:00:34 pm
content: Hi,Can you share the IEE standard? We might be able to analyze the circuit and figure out what the tolerances mean. We can then help with component selection.Regards,Jay_Diddy_B

author: bentx0rx0
author_rank: Contributor
timestamp: March 16, 2014, 04:12:27 pm
content: Not IEEE, but Qihttp://www.wirelesspowerconsortium.com/downloads/wireless-power-specification-part-1.htmlI'm looking at design B1.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: March 17, 2014, 05:01:03 pm
content: Aluminum electrolytics won't have close tolerance or stability. 68 uF is large for a film, but you could make it up from smaller ones, or look for a motor cap. You might find that an OSCON would also do the job if you select it. Even tantalum might be OK if you select it. It's common when making up reference circuits to select parts for the value you need, as finding close tolerance parts at reasonable prices in small quantities off the shelf can be near impossible.

author: Zero999
author_rank: Super Contributor
timestamp: March 17, 2014, 07:57:42 pm
content: Quote from: Jay_Diddy_B on March 16, 2014, 12:00:34 pmThey probably mean a preferred value, i.e. for 20% tolerance a value which is 10, 15, 22, 33, 47 or 68 multiplied by a factor of 10.
Capacitor between isolated grounds in smps. - Page 1
Forum section: electronics / projects

author: Kokoriantz
author_rank: Frequent Contributor
timestamp: July 08, 2025, 01:24:10 am
content: I bought a strange 600w 48v psu from Ali. The output is shown bellow. There is a 2.2nF capacitor between the output ground and the mains rectified ground, isn't it electrocution element if the earth is missing on the output ground?

author: wraper
author_rank: Unknown
timestamp: July 08, 2025, 01:30:04 am
content: Is it the first time you see SMPS? It's very rare to not have it, and it needs special measures such as shielded transformer to avoid using it. Capacitor is safety rated and has low enough capacitance for leakage current to be safe.

author: Kokoriantz
author_rank: Frequent Contributor
timestamp: July 08, 2025, 03:17:24 am
content: I do have several, they have the earth along the 2 ac. If I don't earth the smps, I get buzz. I even have a fix 13.8v, if I don't plug the earth and touch the supply with bare feet, I get electrocuted.This one doesn't have the earth, I wonder if I should add 2 10nf after the CM choke and earth the common lead as usually done.
Capacitor charger  - Page 1
Forum section: electronics / projects

author: Momeries
author_rank: Newbie
timestamp: June 30, 2023, 07:00:46 pm
content: Iam trying to make very fast charger for my 1000 Uf 450 V capacitorI saw this video on youtubehttps://youtu.be/ug82NsxXL94He managed to charge 1500uf 450v capacitor in just 2 secondsFortunately he shared the schematic, but it is little bit confusedCan someone explain the concept of this?

author: wasedadoc
author_rank: Super Contributor
timestamp: June 30, 2023, 07:27:51 pm
content: It is just a boost converter. A 555 is the oscillator which drives the FET on and off. When it switches off there is a large positive voltage spike at its drain. That goes through the diode to charge the capacitor. The other IC is used as a comparator which stops the oscillator when the capacitor has reached the desired voltage.The schematic is slightly confusing as the difference between an intentional blob to indicate a connection and the increased blue intensity where two lines cross (no connection) is not as clear as it should be.

author: Momeries
author_rank: Newbie
timestamp: June 30, 2023, 08:10:52 pm
content: Thanks for explanationDo you think it will work fine with no excessive heat on mosfet?I had a yh11068a it is boost converter up to 390v it worked very great at the beginning but after some days seem the comparator damaged at higher voltage and the boost goes up to 600v so i am trying making my own one
capacitor code EM? (silver mica) - Page 1
Forum section: electronics / projects

author: SArepairman
author_rank: Frequent Contributor
timestamp: January 10, 2014, 11:33:44 pm
content: I have some silver mica capacitors, +-1% 10nF.The brand is unknown unfortunately. they do say EM on them.Does anyone know what it could mean? Is this a voltage rating? A manufacturer?I assume its not the tolerance because it says10000+-1%EM

author: SArepairman
author_rank: Frequent Contributor
timestamp: January 10, 2014, 11:35:45 pm
content: oh solved, its a manufacturer, El Meneco.
capacitor decade box, parallel design considerations - Page 1
Forum section: electronics / projects

author: SArepairman
author_rank: Frequent Contributor
timestamp: January 25, 2014, 03:43:59 am
content: So I have a fair bit of old but good film capacitors, 10n's and 1uF right now, I am looking to getting some 1n and 100n capacitors as I can get them pretty cheap on ebay, 5$ worth is all I need.I wanted to make a decade box that uses dip type switches to link more capacitors in parallel, but I was wondering the effect of a stub, half a capacitor connected to the circuit, disconnected on one side. What is the effect on the circuit of having 40 of these stubs? I don't have a network analyzer...If the effect is significant I could just double up on the switches, so I can completely disconnect the device from the circuit using two switches. It's a bit more of a pain in the ass.I planned to house the thing inside of a tea tin and use banana connects to interface it to the circuit under test. Maybe I would even add 10uF tantalums to get to 100uF (I bought a bunch of old tantalums on ebay really cheap)I have air variable capacitors that cover me up to 100pF, but I would like to extend my capabilities.I know this thing will be crude as hell but I'd imagine it would come in some use, I found my air variable capacitor useful for audio phase trimming.* I suspect I will never use this thing but I went LCR meter crazy since I got me de-5000**im really lying to myself about this ever being useful arent I.

author: Rerouter
author_rank: Super Contributor
timestamp: January 25, 2014, 04:14:19 am
content: The switch when open circuit will be a few pF, so it will still be in circuit (dip switches have a very tiny separation distance) as for stubs just what kind of frequencies are we dealing with here? they dont start working until the skin effect is wider than your trace?

author: SArepairman
author_rank: Frequent Contributor
timestamp: January 25, 2014, 09:22:59 am
content: I know but sometimes you see those crazy PCB antennas, I thought maybe the foil on the capacitor could lead to those kinds of things happening.I guess thats only at really high frequencies where the decade box would be useless?

author: Rerouter
author_rank: Super Contributor
timestamp: January 25, 2014, 10:00:34 am
content: if the trace length is less than 1/10th the length of the wavelength then impedance doesn't matter to a signal thus no tuned antennas and such, though if you do want to chase that, have a look on the datasheet (good luck on Chinese caps) for the self resonant frequency, this is where if it did form a tuned LC circuit the noise would come from (probably in the mid to high MHz) now if this frequency is out of 70-190Mhz then radio will not be a problem either, and if it is, model in the inductance of your wires and you will probably suddenly be below it,
Capacitor discharge circuit - Page 1
Forum section: electronics / projects

author: brakee
author_rank: Newbie
timestamp: December 22, 2018, 05:35:24 pm
content: Hi guys,I would like to build a circuit to discharge a set of capacitors connected to an high frequency AC supply (schematic attached below). In this schematic, one capacitor is charged during the positive half cycle, and the other during the negative half cycle. The idea then would be tosense the charging (positive slope) of one capacitor (for example, the one on the left), and this should trigger a discharge of the right capacitor through say, an SCR. Then the right cap would start charging back up, and this should trigger the discharge of the left one. Ideally, the output would look like something resulting from a unsmoothed full-wave rectifier, with all positive peaks.Does anybody with more experience have a suggestion on what would be a good sense/trigger circuit to accomplish this? Voltages across the capacitors (uF range) would be in the 30V range, frequency would be around 100 kHz. Thanks in advance
capacitor experiment - Page 1
Forum section: electronics / projects

author: Capernicus
author_rank: Frequent Contributor
timestamp: September 10, 2021, 05:44:07 am
content: I hope this is proof enough, I can show the schematic if you want.

author: xavier60
author_rank: Super Contributor
timestamp: September 10, 2021, 05:48:47 am
content: Audio is still crap.

author: jonpaul
author_rank: Super Contributor
timestamp: September 10, 2021, 06:15:42 am
content: Impossible to see any clear video, out of focus and constantly moving. Audio horribleUnclear what OP is doing.Suggest to OP to learn how to shoot a video before post.Suggest to Group Moderator to screen for unviewable or forbidding video posts.Kind Regards,J
Capacitor for A4988 Vmotor input - Page 1
Forum section: electronics / projects

author: metRo_
author_rank: Regular Contributor
timestamp: April 17, 2014, 11:47:25 am
content: Hi,I'm selecting a motor for Vmotor input voltage of aA4988. Did a search at mouserhttp://pt.mouser.com/Passive-Components/Capacitors/_/N-5g7r?P=1z0wrk9Z1z0x565&Ns=Pricing%7c0and found tantalum cheaper than electrolytic. They are ok for that king of application?Thank you
Capacitor Identification - Page 1
Forum section: electronics / projects

author: ElektronikLabor
author_rank: Regular Contributor
timestamp: April 17, 2017, 02:46:52 pm
content: Hello,is it possible to find out the P/N of this capacitor?It's a 1.5µF one.Is it right that it's voltage rating is 250V?What is the manufacturer?I can't find any with similar shape AND ratings.Dimensions:LxWxT: 17mm x 15mm x 8mm (0.67'' x 0.59'' x 0.315'')Thanks!

author: gamalot
author_rank: Super Contributor
timestamp: April 17, 2017, 03:42:13 pm
content: Panasonic ECQE2155KFhttps://industrial.panasonic.com/ww/products/capacitors/film-capacitors/film-cap-electroequip/ecqef-dc-rated/ECQE2155KF

author: ElektronikLabor
author_rank: Regular Contributor
timestamp: April 17, 2017, 06:05:38 pm
content: Thanks gamalot!
Capacitor Identity Mystery Solved - Page 1
Forum section: electronics / projects

author: calzap
author_rank: Frequent Contributor
timestamp: March 04, 2014, 06:23:27 pm
content: Last December I asked for help in identifying several capacitors(https://www.eevblog.com/forum/projects/name-that-cap!/msg340184/#msg340184). One of two that weren't identified is the brown ceramic shown below. I had speculated that it might be a Matsushita, but wasn't convinced because the M wasn't fully enclosed in a box (see pic of a black Matsushita capacitor below). Or maybe it was a stylized version of the CM that many manufacturers use to indicate ceramic multilayer. In January in response to Dave's teardown of a Sennheiser microphone (blog 571), I asked what the tin can was that appeared at about 17:40 into the video and speculated that it might be an oscillator (see pic below). I quit following the thread after a couple of days, but then just looked again, and sq6rdy has posted a reply that it is a SAW filter made by muRata. Sq6rdy is absolutely right; that's what it is. However, the muRata logo on the can looks a lot like the one on the brown capacitor. A little searching turned up a pic of a recently made muRata cap (see blue cap below). I'm convinced that my cap was made by muRata. Double thanks to sq6rdy.Mike in California

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 04, 2014, 06:43:04 pm
content: That black part looks more like a MOV.

author: calzap
author_rank: Frequent Contributor
timestamp: March 04, 2014, 06:49:02 pm
content: Yup, you're right; the black part is a MOV.Mike in California
capacitor in opamp feedback - Page 1
Forum section: electronics / projects

author: electros6
author_rank: Regular Contributor
timestamp: January 07, 2015, 08:28:59 am
content: Hi guys,I many instruments where the reference value is compared with the actual value using op-amp and it is used to drive transistor of mosfet. I such opamps a capacitor is used in the feedback loop to reduce the gain at higher frequencies. how to design such capacitor in the feedback loop.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 07, 2015, 09:19:29 am
content: The pole must be positioned either above or below the dominant pole of the driven system (transistor and whatnot). Usually by a factor of 3 or so.Or better yet, a pole-zero pair (using an R+C instead of C alone) can be positioned so that the zero cancels the system pole, and the remaining dominant pole sets the desired/required roll-off frequency.I don't know what your transistor is driving, but a typical example would be a constant current sink, where the series resistor and gate capacitance form a dominant pole.Tim
Capacitor is not fully charging to trigger SCR - Page 1
Forum section: electronics / projects

author: DDT
author_rank: Contributor
timestamp: February 01, 2017, 12:39:04 am
content: There is a problem with this circuit. The original document specified 3V for power supply. However, the capacitor 13 is only charges to around 0.6v and then stops when I used 3V, and it doesn't trigger SCR 7. I tried 9v and it works sometimes with this voltage. When I disconnect the gate of SCR 7, it seems to be charging fully. I am using TICP106D SCR. In the original document the SCR was BRY55. Both are sensitive gate SCR as far as know, so they should be interchangeable. Both have max Igt 200uA. I don't understand why the current is leaking this much through the gate. Do you have any suggestion? Disregard the rest of the circuit as they have no effect on capacitor 13. I am making this on a breadboard. Thank you.

author: Andy Watson
author_rank: Super Contributor
timestamp: February 01, 2017, 01:12:27 am
content: Has this ever worked? The schematic looks wrong.With only 3V available and 4M7 (R 12) there will less than 1µA available for the gate current. If SCR 7 did trigger it would not latch because of R 8 - this would limit the current to about 100µA - the SCR requires mA (usually tens of mA) to hold-on.How is the other SCR triggered? Its gate voltage is limited to about 1/3 of the base-emitter voltage transistor 22.

author: DDT
author_rank: Contributor
timestamp: February 01, 2017, 01:33:46 am
content: Thank you Andy. I believe the current required for triggering the SCR is coming from capacitor 13 when it's fully charged. Then it goes through resistor 8 etc. This is the arming delay period for alarm. It actually works with 9V. Holding current for sensitive SCRs is low. The other SCR also works, it conducts when break wire 10 (or NC switch) is broken. While charging, lamp 18 is on then goes off when capacitor charged. Transistor 22 won't let capacitor charge by conducting to ground if beak wire 10 is faulty when the arming button 15 is opened, which also cut off lamp 18. This let you know that break wire is faulty,
Capacitor leakage tester (concept design) - Page 1
Forum section: electronics / projects

author: taydin
author_rank: Frequent Contributor
timestamp: September 17, 2019, 09:55:40 pm
content: I was thinking about the conceptual design of a capacitor leakage tester and came up with a design like below:The user will enter the test voltage (and possibly the capacitance in order to give a hint to the device about how long the test will take. But this isn't critical). For example, for a 63V electrolytic, the user might enter 55V (or even 63V).I'll let the DUT charge up to the test voltage over a low noise, low tolerance shunt resistor. While charging, i'll monitor the current using a very high input inpedance, low noise inamp. If the current goes down and settles below a configurable limit (1 µA maybe) the capacitor will be considered leak free. Otherwise it will be considered leaking.But here is one thing that I'm not sure. Let's say the user has set a too high test voltage, for example 80V. Given that the capacitor is being charged over a relatively high resistance shunt, the current will be limited quite a bit. But the capacitor will probably start conducting. So my question is, in a current limited scenario, will a voltage above capacitor limit kill the cap? Or will the cap conduct at the high voltage, and then recover after the voltage is removed?
Capacitor Leakage Tester - Page 1
Forum section: electronics / projects

author: AngraMelo
author_rank: Regular Contributor
timestamp: November 23, 2018, 05:56:01 pm
content: Hello friends,Im building this circuit but I have a couple of questions.About the resistor divider for the current meter: If V+ is around 330V, I believe there will be a rather large current going through those resistor, but thehe is using regular 25 turn trimmers and 1/4w resistor. What am I missing?at 2:34 of this video you will find the schematic

author: 001
author_rank: Super Contributor
timestamp: November 24, 2018, 06:40:24 am
content: Quote from: AngraMelo on November 23, 2018, 05:56:01 pmIt is leakage tester, not a short circuit checker, so do not worryQuote from: AngraMelo on November 23, 2018, 05:56:01 pmIt is hard to see schematic in video for my old eyes

author: AngraMelo
author_rank: Regular Contributor
timestamp: November 24, 2018, 05:29:33 pm
content: Thank you!
Capacitor Manufacturer Search - Page 1
Forum section: electronics / projects

author: aw_rw1
author_rank: Contributor
timestamp: March 05, 2019, 04:07:05 pm
content: Does anyone know the manufacturer of this capacitor? The logo of the manufacturer has an "E" on a side of a cube. Three sides of the cube can be seen. The two of the sides are blank and white.

author: tsman
author_rank: Frequent Contributor
timestamp: March 05, 2019, 04:09:32 pm
content: https://www.electrocube.com/documents/electrocube-230-232a-series-metallized-polyester-capacitors.pdf
capacitor marking on a MICA Cap question? - Page 1
Forum section: electronics / projects

author: innkeeper
author_rank: Unknown
timestamp: August 03, 2018, 03:57:45 am
content: i ahve a bag full of these mica capsthere marked as follows220 ±5%EMok so 220 means 220pf and +/-5 is the tolerancebut what does the EM mean?there are no other markings on this cap, no voltage markings, brand names etc.I am guessing EM may be a voltage rating code???anyone know more?

author: Unknown
author_rank: Unknown
timestamp: August 03, 2018, 07:59:29 am
content: Manufacturer. "EM" = Elmenco (Electromotive Corporation). Owned by Arco, then later IEC Servicemaster.

author: innkeeper
author_rank: Unknown
timestamp: August 03, 2018, 04:25:41 pm
content: awesome thanks!
Capacitor Marking Question - Page 1
Forum section: electronics / projects

author: bostonman
author_rank: Super Contributor
timestamp: February 11, 2022, 10:20:13 pm
content: I have four surface Mount can type capacitors and two I think I figured out the marking and the other two I’m uncertain about.100 gHB N23 - I assume this is 100uF and small g is 4vR47 63 - I assume this is 0.47uF 63v47 CHB. E70 - no idea if I use the C, E, or H for the voltage47 CHB. N92 - no idea if I use C or H for the voltage.Since E70 and N92 are in common places, I assume these three digits are code markings and I’d use the one of the letters in the previous three digits.Thanks in advance

author: bostonman
author_rank: Super Contributor
timestamp: February 13, 2022, 03:06:46 pm
content: I solved this issue.This link provides a good amount of information:https://console5.com/wiki/Installing_Capacitor_Kits#SMD_Cap_CodesThe issue: the 47uF were the main caps in question (the others I just needed confirmation) because they were physically two different sizes, however, both had CHB on them. Turns out they are both 16V but physically different sizes to accommodate the tight fit area.
Capacitor noise in switch mode power supply - Page 1
Forum section: electronics / projects

author: shadewind
author_rank: Frequent Contributor
timestamp: March 08, 2011, 12:43:06 am
content: I'm building a power supply circuit using a National Semi LM2676 switching regulator. The output capacitor is this one:http://se.farnell.com/jsp/search/productdetail.jsp?SKU=9692150When I load the power supply down pretty hard (2.7A or something like that) I get a weird whining noise which drops in pitch from the output capacitor. It seems to be the output capacitor because doing the same thing with the capacitor removed (it produces horrible output of course but it's just for testing) makes no noise.What is causing this? That kind of load is outside of the specs for my component choices of course but I'm still curious of the exact cause.

author: tecman
author_rank: Frequent Contributor
timestamp: March 08, 2011, 01:02:38 am
content: It is not that unusual for caps to "sing". I am not sure, but it could be due to magnetostriction. (Just got a trade journal at work today with an article on cap noise in power supplies, focused mainly on ceramics which have piezo characteristics). Usually the solution is to parallel a number of caps to attain lower esr and handle higher ripple currents. Also your cap seems to be a bit light on its ripple current capability. With the current you are drawing, this can lead to short like of the cap. At those power levels, I would recommend paralleling 3 or 4 of those caps.paul

author: shadewind
author_rank: Frequent Contributor
timestamp: March 08, 2011, 01:23:56 am
content: I'm not going to draw that much current later, that was just for testing. Is the noise because of the higher ripple current when drawing more output current? According to the data sheet, the ripple current is about 30% or the load current.

author: Franki
author_rank: Regular Contributor
timestamp: March 08, 2011, 02:40:26 pm
content: Have you checked the voltage on the cap @ 2.7A? I shuldn't wonder if it sings if voltage is above or a little below 25V when you are having ripples in there.

author: shadewind
author_rank: Frequent Contributor
timestamp: March 08, 2011, 05:56:55 pm
content: I'm outputting 5V so I seriously doubt that.

author: shadewind
author_rank: Frequent Contributor
timestamp: March 09, 2011, 12:56:09 am
content: I finally have a Rigol DS1052E on the way so hopefully, my switcher design will be much less of a guessing game.
Capacitor Polarity Question - Page 1
Forum section: electronics / projects

author: bostonman
author_rank: Super Contributor
timestamp: February 22, 2022, 12:28:52 am
content: I have a silly question about C90 in the attached (circled in red).This is the power supply section from a C64, and I want to confirm why the positive side is on the left. Usually if I see a capacitor in series, it's non-polarized, and, a polarized capacitor always connects to the positive; unless it's a negative voltage then the positive is to ground.This could be an incorrect statement, but this may be a first time I've seen a polarized capacitor in 'series'.I forgot the name of that circuit, however, I'm assuming the positive is on the left because it's the higher voltage, correct?

author: Benta
author_rank: Super Contributor
timestamp: February 22, 2022, 12:52:17 am
content: The positive is on the left, because there's a"+" symbol there.Nothing wrong with the schematic, it's a charge pump voltage inverter circuit.

author: bostonman
author_rank: Super Contributor
timestamp: February 22, 2022, 02:09:50 am
content: I meant electrically why is it on the left?What is the reason it's not connected to the right side instead?

author: ledtester
author_rank: Super Contributor
timestamp: February 22, 2022, 02:30:20 am
content: It's essentially because the left side of the cap is connected to the "+" terminal of the bridge CR4 (through a diode). That means it will always be greater than either of the AC inputs (pins 2 and 4). Since the right side of the cap is connected to pin 4 it makes sense to have the left side of the cap to be +.

author: Damianos
author_rank: Frequent Contributor
timestamp: February 22, 2022, 01:19:50 pm
content: Have a look hereVoltage doublerespecially the two first circuits. Study them a little and then add the rest of the circuit (its easier to do that step by step).
capacitor pulse continuety question - Page 1
Forum section: electronics / projects

author: john23
author_rank: Frequent Contributor
timestamp: September 17, 2024, 04:37:00 pm
content: Hello, When i will build it in my lab and i will turn on the power supply.I have a pulse goint from R10 into C4.capacitor has the tendency to be continues with voltage , so id there is a voltage jump on one side it will transform to the other side .So the quetion is about the capacitor.When we send a pulse on P12 How C4 will behave?What is the exact physical behavior of this capactior C4 in this situation?Thanks.

author: PGPG
author_rank: Frequent Contributor
timestamp: September 17, 2024, 10:38:10 pm
content: Quote from: john23 on September 17, 2024, 04:37:00 pmIf you measure voltage referencing it to GND than capacitor connected to GND can't transform pulse to the other side as the other side is GND and measuring GND against GND you will have 0V (until we don't consider GND connections impedance).During fast pulse at P12 you can ignore resistors here. C1 is loaded through Q1 b-e diode. V1 source dV/dt and its internal resistance and C1 internal resistance and Q1 serial resistance of b-e diode will be factors limiting the current.Circuits should not be designed the way then on power on such big capacitors are loaded throug b-e junction.

author: john23
author_rank: Frequent Contributor
timestamp: September 18, 2024, 09:04:18 pm
content: Hello , What about the situation when i move C4 to be parralel to R10.There is a basic law regarding capacitors shown below."The principle of continuity of capacitive voltage says: In the absence of infinite current, the voltage across a capacitor cannot change instantaneously."looking at the following situation how does the capacitor acts?one leg feel rise of zero to 12V what does the other leg get because of that and why?
Capacitor selection in triac chopper w/ RFI filter & snubber - Page 1
Forum section: electronics / projects

author: iroc86
author_rank: Regular Contributor
timestamp: November 22, 2019, 02:35:27 pm
content: I'm designing a simple triac chopper circuit for use as an AC motor speed controller. The input is 120 VAC and the load will draw 1 A or less. I want to include an LC filter on the input side for RFI suppression and an RC snubber for the inductive load. I'd like to get some advice on selecting the proper type (not value) of capacitors to use in each portion of the circuit.I've attached a generic schematic below. It's essentially the same as a common lamp dimmer circuit. L1/C1 is the input suppressor, C2/C3 are the triac trigger caps, and R3/C4 is the snubber.I know that C1 should be X2-rated because it's across the line, but I'm less sure about C2, C3, and C4. These caps should probably be film/foil to handle the surges from operating the triac, but is an X/Y class rating necessary? I recognize that the safety classes only describe the failure mode, not the use case, but they're still technically an across-the-line application even though the caps are in series with resistors and other components. Does it really matter whether they fail short (X) or open (Y)? I've also read that safety capacitors are intended for line suppression and aren't really designed for snubber circuits and whatnot.I took apart a commercial lamp dimmer and found a circuit similar to the one I'm building. The equivalent of C1 is a boxed film cap (no safety rating from what I could tell) and C2/C3 are dipped film/foil, but who knows the composition. Just looking for some guidance on best practices... I'd appreciate any input.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 22, 2019, 03:14:10 pm
content: Only across the line in the sense that, when the TRIAC is completely off, most of the line voltage drops across them; but they don't need to be X2 rated, because the transient voltage is limited by the TRIAC. (Instead of avalanche breakdown, thyristors latch on when subjected to overvoltage.)So any PP or PE film cap rated >=250VAC and xVDC (where x is the TRIAC DC/peak rating) should be fine.The trigger caps can be lower voltage, but being smaller, probably doesn't matter much in terms of size or cost. DIACs are usually what, 20-30V?Tim

author: iroc86
author_rank: Regular Contributor
timestamp: November 23, 2019, 07:59:36 pm
content: Thanks for the help, Tim! I hadn't considered the relationship between triac breakdown voltage and the capacitor rating, but it makes sense.I ended up going with general-purpose PP caps rated at 630 VDC / 400 VAC for the triac trigger and a "pulse" cap for the snubber, just for good measure, since its dV/dt rating was an order or magnitude greater than the general-purpose part (1000 vs. 116 V/µsec). I still picked up an X2-rated safety cap for the RFI suppressor, but I think the other caps are a better fit for their respective applications.