hybridfree/eevblog-posts huggingface dataset:
CCTV cameras - Powering them from the PC? - Page 1
Forum section: electronics / beginners

author: cs.dk
author_rank: Unknown
timestamp: August 16, 2015, 10:12:25 am
content: As subject.Is it safe to power CCTV cameras from the PC's PSU? I think the outer of the BNC is grounded to the chassis/earth. But is the negative of the PSU grounded to, or will something bad happen? I may just try to measure the negative rail with respect to ground?The cameras consume 200 mA (with IR leds on, IIRC) so the load isn't that big.

author: fcb
author_rank: Super Contributor
timestamp: August 16, 2015, 10:19:55 am
content: You might get ground-loops and noise. It's very likely that the BNC outer and the cameras 0V are the same.Also,if the cameras are exterior you should think about things like lightning strikes and EMC.

author: cs.dk
author_rank: Unknown
timestamp: August 16, 2015, 10:29:41 am
content: Thanks,The cameras will be outdoors.. I better find a suitable plugpack for them.

author: drcheap
author_rank: Newbie
timestamp: August 17, 2015, 06:32:56 am
content: FWIW, IP cameras with PoE support make this sort of thing a non-issue.But if you've already got the oldschool cameras that may not be an option.

author: Richard Crowley
author_rank: Super Contributor
timestamp: August 17, 2015, 06:36:45 am
content: Yes it is typically safe because the signal ground (the outer ring of the BNC/RCA/whatever connector is circuit ground. And all the power busses in the computer are referenced to that same circuit ground.At 200mA each, I agree that isn't much of a load so chances seem pretty good that a typical computer power supply would have sufficient surplus power.

author: cs.dk
author_rank: Unknown
timestamp: August 17, 2015, 12:27:45 pm
content: Well i've got 4 cameras and pc, software and a monitor for free. I did find a 12V 2A supply in my parts bin yesterday, so they're up runningIt's some Linux software I think, the PC can boot without HDD, so the OS may be in a ROM?
CD player went bananas - Page 1
Forum section: electronics / beginners

author: IvoS
author_rank: Frequent Contributor
timestamp: August 19, 2013, 06:43:54 pm
content: I have an old Denon CDP, was just curious about the clock frequency, sampling rate and how it works.. so I started probing around. When I touched one of the caps on the crystal side to check for the clock frequency, the platter stopped and the motor started to spin backwards like one million rpms . What the heck? I used my Rigol 1052 scope on both 1x and 10x probe settings, I could see some changes in signal when I put the probe 10x.How could that possibly happen that I totally confused the CDP just by probing it? Any idea?

author: Rerouter
author_rank: Super Contributor
timestamp: August 19, 2013, 07:21:43 pm
content: the capacitance either side of the crystal will likely only be 7-30pF, so loading it up with a x10 probe at another 30 odd pF is going to interrupt or possibly stop the oscillation,
cd4017 question...about reset pin - Page 1
Forum section: electronics / beginners

author: rhesus3000
author_rank: Contributor
timestamp: April 24, 2017, 11:18:35 am
content: I made new schematic for 4017 16 step sequencer. So i need to include a feature so i can reset it at 2,4,8 stages of 1st 4017 via a rotary switch.So...to reset it for 2 stages...i connected pin4 to reset via switch...ect. My question is this...at the same time as it resets from pin4 it is connected to output...soo will it reset normaly or reset and activate pin4 output at the same time? What the result will be? Do i need to reset it one pin below? Here is the schem.

author: BC109C
author_rank: Newbie
timestamp: April 24, 2017, 05:17:54 pm
content: I've just had a quick look at your circuit and there are a few errors.Your reset line cannot be left floating it has to be tied to ground via a resistor,10k fior example.You have not stated supply voltage and although some CMOS will work down to 3V youhave diodes D in your reset circuit. You have not stated their type but there willbe a voltage drop across them which you need to take into consideration if the circuitwas working on low voltage.Some rotary switches are make before break. This could cause your circuit to resetearly deending on counter output.Also rotary switches have contact bounce. This may be inportant depending on howfast you intend to clock your circuit.Reset on 4017 resets the output to "Q0"Q4 output would be high momentarily before the count is reset to Q0.That was just a quick glance and there may be points I have missed, hope that helps.

author: tooki
author_rank: Super Contributor
timestamp: April 24, 2017, 06:54:48 pm
content: Quote from: rhesus3000 on April 24, 2017, 11:18:35 amI happen to have been playing around with a 4017 a week or two ago. When you tie one of the outputs to Reset, obviously the output will go on just as BC109C said (it has to, how else would it trigger the reset?), but the reset reacts so fast that the resulting pulse isextremelysmall. So small that I could barely get my oscilloscope to trigger on it.I think what you are asking is this: if, say, output 4 is tied to Reset, will output 4 stay on for a full cycle, or does the reset occur immediately? No, it will not leave output 4 on for its full cycle, the reset happens immediately and output 4 will turn off as soon as the reset is detected.

author: rhesus3000
author_rank: Contributor
timestamp: April 24, 2017, 08:14:29 pm
content: Quote from: tooki on April 24, 2017, 06:54:48 pmYEAAAAAA THANK YOU!!!!Quote from: BC109C on April 24, 2017, 05:17:54 pmVery helpfull!!!! Is this the floating reset you were talking about. And yes...i will delete those diods (1n4148)..you are right about the voltage drop i made a mistake!!!! And the Vdd would be eigher 5..or 9...it dependsONE MORE QUESTION...would cutting down vdd to second 4017 successfully "turn it off"...i mean would it be the same as taking it off the board physiclly?
CD4026 - Page 1
Forum section: electronics / beginners

author: neo
author_rank: Super Contributor
timestamp: November 18, 2016, 02:23:01 am
content: Here is yet another question that makes me feel like an idiot, with the cd4026 i built a test circuit to become more familiar with how it works. My circuit works but what i cant figure out is that it doesn't just tick, if i get it counting it will stay counting but i have to jump start it by pressing my fingernail into its side which works for a test circuit (if not finicky) but is obviously impractical in a clock. My top two ideas are that it either needs a large value decoupling capacitor, i tried 1 nf to no avail, or i missed something important. I'm using my arduino to pulse it if that matters for this question.EDIT: i solved it
CD4053 replacement for higher bipolar signals - Page 1
Forum section: electronics / beginners

author: belzrebuth
author_rank: Frequent Contributor
timestamp: February 17, 2021, 01:34:49 pm
content: Hi all,I've got a bidirectional switch circuit that I'd like to adapt to switch signals up to 24Vpp or so (+12V to -12V).The circuit now works with a CD4053 which has an absolute max rating of 20Vpp so I wouldn't like to stress it.What would be a suitable replacement that could work a spdt switch?I've got some DG411 and DG202 switches that I could try but these are spst.I've also got a DG409 that looks like it could work but I'm a bit baffled on how to wire it.

author: Kleinstein
author_rank: Super Contributor
timestamp: February 17, 2021, 03:01:14 pm
content: For a single SPDT switch there is the DG419, as a smaller brother to the DG409 (which is more like the higher voltage analog to the CD4052).The DG202 would need some extra logic - the DG203 should be a mix of NO and NC swiches, so easy to combine.

author: belzrebuth
author_rank: Frequent Contributor
timestamp: February 17, 2021, 04:41:57 pm
content: Thanks!Perhaps I've got some of those dg419 stashed in here somewhere. I'll try and post back later.There's also the DG333 (quad spdt) but these are kind of expensive.
CD405xB CMOS Single 8-Channel Analog Multiplexer/Demultiplexer - Page 1
Forum section: electronics / beginners

author: SrgiO
author_rank: Newbie
timestamp: February 12, 2020, 09:26:56 am
content: Hello, I was browsing my DDS140 oscilloscopy and I understood (more or less) its structure.But I cannot understand what it is for (in which part of the signal acquisition block diagram) the CD405xB CMOS Single 8-Channel Analog Multiplexer / Demultiplexer is involved.Thank you very much for reading me.Greetings.

author: DTJ
author_rank: Super Contributor
timestamp: February 12, 2020, 09:33:55 am
content: Perhaps an image of the schematic would help people to help you.

author: SrgiO
author_rank: Newbie
timestamp: February 12, 2020, 09:48:04 am
content: Thank you for your response, I have read in this forum the thread dedicated to my oscilloscope, but I did not want to duplicate information, so I have not added things that were already there.The only thing I know is what I already have, but I also think it's a good idea to put the most significant links here to help.https://www.eevblog.com/forum/testgear/sainsmart-dds120-usb-oscilloscope-(buudai-bm102)/https://sigrok.org/wiki/SainSmart_DDS140Thank you.

author: SrgiO
author_rank: Newbie
timestamp: March 03, 2020, 09:46:46 am
content: Is it possible that my question should be asked elsewhere?Thank you!

author: SrgiO
author_rank: Newbie
timestamp: April 20, 2020, 03:43:27 pm
content: After so long I have managed to understand what function these MUX have.I found the schematic of a similar digital oscilloscope that made me understand it even better.https://ibb.co/LtKBfJHOne mux adjusts the gain and another adjusts the measurement range.After this, new questions are opened to me ... Is it the correct way to do it for greater accuracy?I saw the video: How-To-Reverse-Engineer-A-Rigol-DS1054Z and it seems that the best option is to design an opAmp with current mirrors.But I can't find this part where he explains it to be adjustable gain.Greetings and thanks!
CD4060 frequency/ocialiation configuration - Page 1
Forum section: electronics / beginners

author: bitman
author_rank: Unknown
timestamp: January 22, 2018, 04:25:49 am
content: I know it's an old chip - but I am struggling with how to set R1, R2 and C to get a needed frequency. I understand I can use a crystal, but for now I'm trying to understand the values. From my own experimentation there are some limits that aren't clear to me - so I wondered if there isn't better (for dummies kind) materials explaining the relationship between the R and C values. I don't get a traditional RC formulator to work, mostly because there are two resistors and well, I find lots of different setups out there that aren't matching the datasheets including pulling the C to ground through a diode ... anyway ..Question: What formular should I use to calculate R/C for a given frequency? Let's say I want the pulse on pin 11 to be 1Mhz - how do I determine the C and R values? Reading the very old fax/photo copy TI uses, I see the following (which is hard for me to grasp):Rs is 2Rx to 10RxT = 2.2 RxCxWhich R is this talking about? Rs barely seem to have an effect on the frequency - Rx seems to cut out the frequency when I get close to 200Khz on Q4. I'm using a 10pF cap and using less than 2.2kOhm as Rx just makes the oscillation stop. I've tried 5v and 10v input - this is definitely a circuit that gets more stable at higher voltages, but 5v is what I'm trying to make it work at.The datasheet also have two different max values for frequency on the input (one says max 3.5 Mhz, the other says "3.5Mhz->7Mhz). Since this is ancient documentation/chipset I'm obviously not reading it right, so I'm hoping for some guidance on how to read this so I can set things to the proper values.Thanks.

author: Zero999
author_rank: Super Contributor
timestamp: January 22, 2018, 09:10:04 am
content: The maximum frequency depends on the power supply voltage, temperature and varies from IC to IC.Low values of C and R will give unpredictable results, as the parasitic capacitance and output resistance of the gate will start to dominate. To get frequencies above a few hundred kHz, you need to use an LC oscillator, crystal or ceramic resonator. It even implies this on the data sheet. "RC oscillator frequency of 690kHz min. at 15V" At 5V the maximum RC oscillator frequency will be lower.http://www.ti.com/lit/ds/symlink/cd4060b-mil.pdfHere's a tutorial on LC oscillators with CMOS gates.https://wiki.analog.com/university/courses/alm1k/alm-lab-21

author: danadak
author_rank: Super Contributor
timestamp: January 22, 2018, 11:53:35 am
content: How accurate do you want the frequency to be ?The period for 1 Mhz , T = 1 / F = 1 uS.So 1 x 10-6= Rx x CxThat being said max F is 810 Khz at Vdd 10V, even lower for 5V.https://www.electronicspoint.com/threads/74hc-oscillator-how-fast.282578/Hero999's recommendations to use LC or crystal make much more sense. And considerusing a 74HC4060 vs the CD4060.Regards, Dana.
CDI Component identification - Page 1
Forum section: electronics / beginners

author: aroumeliotis
author_rank: Newbie
timestamp: April 17, 2020, 01:02:42 pm
content: Hi people!I recently found an interest in electronics and been trying to learn by repairing electronics of friends or whatever I find interesting and manage to get my hands onSo I got hold of an analog AC CDI from a 3 cylinder outboard from the 90's. Managed to remove the this black silicone to reveal the board and the electronics but got stuck when I found couple of components that I'm not familiar with, or just could not figure what they are. They are both TO-92 packages and here is what I know about them.1. SCR5 162 from Motorola. This is probably the easy one, tested it and seems behave like an SCR thyristor. Searching online this has been discontinued since 2005 but I can find no datasheet nor do I know what it could be replaced with. I've seen the BT151-800R commonly used in CDI's.2. The second part is also TO92 but letters and numbers are not visible unfortunately... I removed from the circuit the suspected as problematic and another one assumed working. So I tried to perform some test to figure what they are. With the multimeter in diode mode they only conduct between the 2 left side leads, both ways2.1 The suspect measures voltage drop of 0.245 V no matter of the polarity2.2 The assumed working measured 0.191 V, again polarity doesn't affectAny help would be very welcome!

author: Manul
author_rank: Super Contributor
timestamp: April 17, 2020, 01:47:27 pm
content: I have little idea about CDI in general, but about your TO-92 measurement I can say, that some discreete semiconductor packages have integrated resistors. In that case diode mode may be showing voltage drop of that resistor and not the semiconductor junction itself. So check with ohm meter and see, maybe it shows some typical resistance like 4.7K or something.
CE amplifier ac analysis - Page 1
Forum section: electronics / beginners

author: barak198
author_rank: Contributor
timestamp: April 07, 2016, 06:36:43 am
content: Hi everyoneI need some help with CE amp ac analysis , I wanted to use the model I added to the circuitbut I am not sure how to find RB ( usually RB1 RB2 are in paralel in ac but not in this case )thank you all

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: April 07, 2016, 09:15:39 am
content: Millers Theorem? Pretty hazy here, it's been a long time.https://wiki.analog.com/university/courses/electronics/text/chapter-9

author: danadak
author_rank: Super Contributor
timestamp: April 07, 2016, 10:25:28 am
content: http://www.bu.edu.eg/portal/uploads/Engineering,%20Shoubra/Electrical%20Engineering/2461/crs-11966/Files/ECE312_lec04.pdf

author: LvW
author_rank: Frequent Contributor
timestamp: April 08, 2016, 07:36:55 am
content: Quote from: barak198 on April 07, 2016, 06:36:43 amIn your equivalent small-signal linear circuit all capacitors are assumed to represent short circuits.For this reason, also in this casae you are allowed to consider R2 in parallel to R3.The circuit has only DC feedback for operational point stabilization.However, what is the value for Rc in your equivalent diagram?And what is the operating frequency (role of C3)?

author: orolo
author_rank: Frequent Contributor
timestamp: April 08, 2016, 08:47:35 pm
content: Note that the amplifier lacks an emitter resistor. If you calculate r_pi, you will get something in the order of 2K, which will dominate the amplifier's input impedance. RB is well over 30K at audio frequencies so, compared to r_pi, it is not that relevant.
CE pre-compliance testing: Converting an oscilloscope into a spectrum analyzer? - Page 1
Forum section: electronics / beginners

author: Pack34
author_rank: Frequent Contributor
timestamp: February 18, 2016, 03:23:42 pm
content: I made the necessary changes to what I "think" should improve the overall performance and get the product to pass but I have no way to do any real testing without taking it to someone or buying a spectrum analyzer.I have a nice agilent o-scope that has what I think to be a really good FFT measurement. Would it be as simple as attaching an antenna to an amp and plugging it into my scope to get a general idea of what I'm looking at. This wouldn't be to replace pre-compliance testing but a way to quickly validate in-house that "this change makes it works" and "this change makes it better." To get some immediate feedback.I've found some cheap $100 USB ones but I'm not sure I would trust it as much as if I could get my o-scope to do it.Would this work? Or should I just look at picking up a cheap spectrum analyzer off of ebay?

author: Neilm
author_rank: Super Contributor
timestamp: February 18, 2016, 07:15:37 pm
content: You may not need the amp - it would have to be a good one that would work at many MHz. It is possible to make a small antenna from a piece of wire and plug directly into the scope. Even the scope probe just lying next to or nearby can pick up enough information. That being said, small antenna kits are not that expensive.

author: KJDS
author_rank: Super Contributor
timestamp: February 18, 2016, 08:24:38 pm
content: You'll save a huge amount of time and effort picking up a spec ana
CE/CB BJT Amplifier(s) + Load Lines!  - Page 1
Forum section: electronics / beginners

author: NoFilter
author_rank: Contributor
timestamp: March 08, 2019, 02:50:32 am
content: Hi all,This diagram from a lab assignment is not making sense to me...any help would be greatly appreciated.I don't understand what ICMAX*Reis and why it appears on this diagram. Even if it should be on the diagram, why is it only Reand not RDC? Shouldn't VCEminbe from 0V to ~0.3V?When calculating Reand Rc(Re is maximized with respect to Rc), this equation is used:I've tried leaving the term I don't understand out (probably a bad idea lol), which causes either Rc or Re to be negative and I have tried calling it ICMAX*RDC, which results in two negative resistances...Side question:For a Common base amplifier, would RACinclude Rs (the signal resistance)? Thus should be RC||RL+ Re||Rs?Thanks a ton!
Cell monitor help retry - Page 1
Forum section: electronics / beginners

author: syncro
author_rank: Newbie
timestamp: April 06, 2018, 01:58:35 am
content: Lots of views but no response to my original post, thought it may be due to people not being able to easily look at the schematic, so trying again with a pngHello allI'm attempting to modify a cell monitor circuit that I found on github.[urlhttps://github.com/scttnlsn/cell-monitor].Apparently Scott has his boards talking to an Arduino and is going to build a separate microcontroller board to complete his project. I'd like to do similar, but one step at a time.Since I bottom balance the cells and thus dont need a balance circuit, there are enough pins on the tiny 85 to drive a high and low voltage cutoff. So I added 2 TLP175A photorelays, the output of which will trigger a relay which in turn deactivate the contactors on either the charge or discharge circuit. While the cells power the board, the outputs are driven by a separate 5v supply, shared with relays and eventually the controller. I also added a fuse and laid everything out so the boards can be assembled onto the cells with the connectors lined up so they can be neatly wired up in a daisy chain.This all sounds good to me, but I really have no idea if Ive chosen the right coupler, and it wouldnt suprise me to hear Ive made some elementary errors, let alone the pcb since Ive never tried to lay one out before. I'd be very appreciative if anyone took a look at the attached files and gave an opinion
Cell Phone battery Faulty? - Page 1
Forum section: electronics / beginners

author: robylr
author_rank: Newbie
timestamp: September 14, 2015, 05:11:32 am
content: I`ve use a Samsung Galaxy Core I8260L for a year now and out of the blue the phone started to restart for no reason and at random times.I reset the phone to Factory default and even Format and load a new ROM without the carrier`s apps. Removed the SD card and didn´t install any apps. The problem is that the cell Phone keeps restarting and even freezing when taking calls, typing, unlooking or just sitting on my desk.I did test the battery to check if it was bulge or had any visible damage and it has none that i can see. The phone was never droped since I bought it.The question: is There any way a battery can be broken somehow that can´t be visible and still work? and if there is how can I test it?

author: jitter
author_rank: Frequent Contributor
timestamp: September 14, 2015, 05:52:29 am
content: Does it still do this when you connect it to the charger?

author: robylr
author_rank: Newbie
timestamp: September 14, 2015, 07:57:26 am
content: It does. I tried both usb and the charger that came with the Phone and still resets just by sitting there.It holds charge not like new but it lasts like 14 hours

author: wraper
author_rank: Unknown
timestamp: September 14, 2015, 08:00:34 am
content: Quote from: robylr on September 14, 2015, 05:11:32 amNo, if battery is bad, phone will just shut down, not freeze or restart.

author: kripton2035
author_rank: Super Contributor
timestamp: September 14, 2015, 08:47:19 am
content: I had a bad battery on a consumer's macbookpro that randomly made the mac hang or restart, even with the power supply connectedif you can try another battery this would solve the question... if it's not the battery then the phone has to be changed

author: mikerj
author_rank: Super Contributor
timestamp: September 14, 2015, 09:26:58 am
content: It's much more likely to be a hardware fault such as a bad solder joint on a UCSP device.
Cell phone battery internal circuit - Page 1
Forum section: electronics / beginners

author: Bibiricat
author_rank: Contributor
timestamp: November 26, 2013, 06:33:30 pm
content: Hello.I recently got 2 dead cell phone batteries and pulled the internal PCBs from them.I was wondering if i can attach one of them to a 1 cell Lipo to protect it while i charge it with a USB 5v 1 cell charger and discharge it with a 5v usb boost converter.Any info would be welcomed.First pcb: (sorry for the bad focus)http://postimg.org/image/gkdryl3xj/Second PCB (from a Samsung phone)http://postimg.org/image/6o67s4xvr/Charginghttp://www.ebay.com/itm/170926767910?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649Discharginghttp://www.ebay.com/itm/400345678301?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

author: ohmineer
author_rank: Contributor
timestamp: November 26, 2013, 09:53:04 pm
content: I wouldn't trust a circuit like this without testing it first because using a battery outside reasonable limits can have a fatal end.Cell specs usually indicate what values for each particular model should be considered as thresholds and protection circuit should be chosen to meet them.In any case if you are able I test the circuit and check that it's working and that protections are conservative, maybe you could use it (for example: Charge cutoff voltage 4.25v, discharge cut-off voltage 2.75v, over current 2 A and proper delay times for all of them)

author: amyk
author_rank: Super Contributor
timestamp: November 27, 2013, 07:36:58 am
content: Depending on how much current you want to draw, a cellphone battery protector may have its short circuit trigger set too low - as they're usually used at a discharge rate of far less than 1C.Don't rely on the protection circuit to prevent damage from overdischarge.

author: Bibiricat
author_rank: Contributor
timestamp: November 27, 2013, 11:40:14 am
content: Thank you for your input.I will test them and see what they do. I'll post some feedback soon.

author: G7PSK
author_rank: Super Contributor
timestamp: November 27, 2013, 03:43:59 pm
content: Many of those boards are the reason the battery is dead, the voltage gets to low or high and the chip on the board inside the battery package shuts down never to be restarted.

author: peter.mitchell
author_rank: Super Contributor
timestamp: November 28, 2013, 07:30:15 am
content: Additionally, those boards, unlike what most people think are a "last line of defence", most phones ect will go into a low voltage sleep mode when the battery gets low, those boards are there only to prevent this tiny quiescent current completely flattening the battery - often, their cut-offs are far below and above recommended cycle life voltages, because that is usually controlled by another bit of smarts in the device.
Celling Fan  - Page 1
Forum section: electronics / beginners

author: Jbliss
author_rank: Regular Contributor
timestamp: February 23, 2016, 01:05:08 pm
content: This might be the wrong place.I have taken out a celling fan in my house due to renovations and i get reading of 24 -25 volt AC across the fan wires and if they are disconnected then none of the fans in that part of the house work. I have looked up 24v AC fans and can't find anything. is this 24v being created from a transformer in the celling oranyone with any knowledge of fans care to help

author: Dave
author_rank: Super Contributor
timestamp: February 23, 2016, 01:15:31 pm
content: It's probably voltage induced from the nearby wires. Some meters have a low impedance mode for these exact occasions, it makes the input impedance of the meter just low enough (about 2k, IIRC) to put a bit of load on the measured nodes, so the ghost voltages disappear.I can't say I would advise you to attach a resistor between the wires and try remeasuring. You wouldn't want things to blow up in your face, should you make a mistake.

author: Jbliss
author_rank: Regular Contributor
timestamp: February 23, 2016, 01:18:44 pm
content: Thanks Davewhats weird is they have to be connected for the fans to work?
Center tap transformer - measuring inductance - Page 1
Forum section: electronics / beginners

author: justinjja
author_rank: Regular Contributor
timestamp: June 03, 2023, 03:28:15 pm
content: I'm measuring the secondary of a ~1kw 60hz transformer,between the 2 secondary legs I get 0.22H, seemed reasonable.But measuring between each leg and the center tap and I get no inductance, just a small resistance.Is that normal?I was expecting to get 0.11 H between each leg and the center tap.I was thinking it was the meter, so I hooked up an AC voltage and confirmed the meter isn't wrong, rather my understanding must be wrong.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 03, 2023, 03:43:24 pm
content: With a coil the inductance is proportional to the number of turns squared. So the expected inductance is 0.055 H for each half. An iron core may be slightly nonlinear and the inductance reading may not be that accurate.

author: justinjja
author_rank: Regular Contributor
timestamp: June 03, 2023, 04:01:08 pm
content: Oh right,The meter reads inductors an order of magnitude smaller than 0.055H,Seems like I should still at least get something?

author: Jwillis
author_rank: Super Contributor
timestamp: June 03, 2023, 05:13:32 pm
content: Just a shot in the dark here. Does your meter have both an Auto function and manual function? I know with mine that sometimes when values are very low, I can get resistance readings from inductors when in Auto mode but get proper inductance reading in manual mode. You can get weird readings as well if the frequency is set to low or to high.Also try doing calibration before doing your test. This will often settle down meters that get a bit erratic.Inductance changes with frequency. Some inductors are sold to have a specific value at a specific frequency. You can find some with the same inductance values but are at different test frequencies. The standard 1kHz test does not always work. For laminated transformers its best to test at the lowest frequencies of 100 or 120Hz.Hope this helps some.

author: justinjja
author_rank: Regular Contributor
timestamp: June 03, 2023, 06:49:56 pm
content: Figured out my issue, was testing in series with a light bulb at 120v 60hz (lol)Treating the bulb as a resistor in my calculations,But really a small change in voltage was changing the bulb's resistance.Using a 1k resistor and I get 14mH for the full transformer and 2.8mH between the center tap.EDIT:Oh my I'm using one of those cheap T4-LCR meters, so it can't be trusted for any level of accuracy.
Center-tapped Transformer Help - Page 1
Forum section: electronics / beginners

author: pieshower
author_rank: Regular Contributor
timestamp: April 14, 2022, 12:56:10 pm
content: Hello everyone! I am currently researching camera flash circuit designs and would like to build my own custom one. However, I am unable to find a source that details how to calculate the output voltage for the 22nF capacitor.

author: bob91343
author_rank: Super Contributor
timestamp: April 14, 2022, 04:34:34 pm
content: You need to rephrase your question. I don't understand what you are asking. Further, there is no indication of turns ratio of the transformer.

author: Terry Bites
author_rank: Super Contributor
timestamp: April 14, 2022, 05:52:35 pm
content: http://www.electroniq.net/power-supply/dc-dc-converters/12-v-xenon-flasher-circuit-project.htmlQuick answer, a few volts.https://www.physicsforums.com/attachments/fflash1-gif.154165/

author: CaptDon
author_rank: Super Contributor
timestamp: April 14, 2022, 09:16:38 pm
content: That transformer would definitely NOT be 'CENTER' tapped. The base drive portion would consist of just a few turns perhaps 10 to 15 and the portion above it generating the high negative voltage may have hundreds of turns. Who made the transformer? What is the turns ratio of all three sections?

author: MikeK
author_rank: Super Contributor
timestamp: April 14, 2022, 11:49:20 pm
content: FWIW, one of The Signal Path's first videos covered the flash circuit of a disposable camera. At the very least he provides some good information.
Center Tapped Transformer vs Dual Secondary Transformer for Split Supply - Page 1
Forum section: electronics / beginners

author: bitshift
author_rank: Regular Contributor
timestamp: January 08, 2016, 07:50:16 am
content: Hey guys,I would like to build a small linear bench power supply with one positive channel and one negative channel referenced to a common ground. With a center tapped transformer, the center tap becomes the common ground. From what I understand, you can use a transformer with dual secondaries and connect the + side of one of the secondaries to the - side of the other secondary and use that to create the common ground for the split supply.Is there any downside or potential traps for young players using a dual secondary transformer in such an application?

author: Zero999
author_rank: Super Contributor
timestamp: January 08, 2016, 09:00:22 am
content: It makes no difference whether a centre tapped or dual secondary transformer is used.The only problem with a dual secondary transformer is getting the phasing wrong but that just means it won't work. Reversing the connections to one secondary would solver the problem.

author: bitshift
author_rank: Regular Contributor
timestamp: January 08, 2016, 09:17:13 am
content: Thanks for the replyJust wanted to be 100% sure before fiddling with the mains.Just to be clear by phasing you mean that if you choose to connect the wrong secondary wires together the AC will destructively interfere and you would get 0V?

author: Zero999
author_rank: Super Contributor
timestamp: January 08, 2016, 09:20:10 am
content: Quote from: bitshift on January 08, 2016, 09:17:13 amYes, connecting the wrong secondary wires together would result in 0V.

author: bitshift
author_rank: Regular Contributor
timestamp: January 08, 2016, 09:21:20 am
content: Awesome, thank you

author: IconicPCB
author_rank: Super Contributor
timestamp: January 08, 2016, 09:33:37 am
content: Split windings give you the option of setting up independent supplies which do not necessarily have to be connected at some notional "centretap" position. They could be used as two independent supplies powering say two circuits.

author: Gyro
author_rank: Super Contributor
timestamp: January 08, 2016, 09:55:18 am
content: With dual secondary you also have the option of switching them to give you a supply that can either provide a full output voltage or half the output voltage at twice the current. As previously mentioned, the ability to provide two independent floating supplies is also very useful.

author: dom0
author_rank: Super Contributor
timestamp: January 08, 2016, 11:00:13 am
content: Take a look at the HP 6236B or HP E3630A

author: Brumby
author_rank: Unknown
timestamp: January 08, 2016, 11:17:44 am
content: Quote from: IconicPCB on January 08, 2016, 09:33:37 amA big +1 for this.
Ceramic Axial Bead Capacitors - Page 1
Forum section: electronics / beginners

author: jheatac
author_rank: Regular Contributor
timestamp: August 16, 2024, 01:31:20 am
content: I'm just looking over a board and there are 4 yellow ceramic bead capacitors - axial through hole. They are in locations marked as a capacitor, but the markings have 4 digits ands everything I find says that ceramic capacitors only have 3 digits.Markings are:K5R printed above 103MFC3 printed above 1004TV2 printed above 1001What are the ratings, please?

author: tooki
author_rank: Super Contributor
timestamp: August 16, 2024, 02:03:54 pm
content: First of all, 4-digit codes do exist, but the last digit is always a letter, indicating tolerance. 103M, for example, means 10nF 20%.https://www.digikey.com/en/resources/conversion-calculators/conversion-calculator-smd-capacitor-codeHave you desoldered the caps to make sure these are the only markings?Is it possible that 1004 and 1001 are not values, but date codes? (4th and 1st weeks of 2010, for example.)K5R is Kemet code indicating 50V, X7R. See page 5 inhttps://archive.org/details/manuallib-id-2597468/page/4/mode/2up?q=K5R(Screenshot attached.)Some googling suggests TV2 might be a tantalum, but this is not confirmed.
Ceramic cap microphonics in a high-vibration racecar - Page 1
Forum section: electronics / beginners

author: kevinchen
author_rank: Newbie
timestamp: November 10, 2013, 05:49:23 am
content: Hi all,I've been lurking unregistered to find answers to electronics questions for awhile, but I didn't see that this one had been answered before!I'm designing a switching power supply to power the digital logic of a racecar from the car's 12-V battery. I'm planning to use ceramic caps on the input and output, but I heard on the Amp Hour that they have problems with microphonics, especially the X7R ones.Since there will be a lot of vibration (compared to a consumer car, ours feels like it has no suspension, and needs to drive at 60mph/100kph), I was wondering if this is serious enough to reduce the quality of the converter's output. Thanks for your help!Kevin ChenColumbia Univ. Formula SAE TeamSwitching IC datasheet:http://www.ti.com/product/LM22672-Q1

author: tszaboo
author_rank: Super Contributor
timestamp: November 10, 2013, 09:21:35 am
content: Check out this datasheet:http://www.linear.com/product/LT1964They measured the noise for certain vibration (tapping the capacitor with pencil). It was 1 mV peak to peak. Even if you multiply the noise 100 times, you are still well within the region of any digital IC.If price is no object, AVX and Kemet has capacitors which are on lead frame, which supposed to decrease the microphonics effect, or clever mounting of the PCB can help. Or buy millitary/aerospace rated caps.

author: SeanB
author_rank: Super Contributor
timestamp: November 10, 2013, 10:07:56 am
content: When you make the board glue the caps to the board, and use a flexible conformal coat ( you will need a conformal coatr in any case for automotive use) so just choose a reenterable coat for the board. As well use some flexible mountings for the electronics boards in any case. If you are stuck go look at how VW mounts the engine management units in a VW Golf/rabbit/Polo/Seat in the top of the engine bay, and look at the flexible mounts they use, as well as how they use ceramic capacitors inside.Scrapyard and buy some broken boxes and tear apart for tips.

author: Zero999
author_rank: Super Contributor
timestamp: November 10, 2013, 05:44:02 pm
content: Put an electrolytic and small ceramic in parallel. The electrolytic will short the noise created by the ceramic to ground and the ceramic will have a lower impedance, especially at high frequencies.

author: kevinchen
author_rank: Newbie
timestamp: November 10, 2013, 05:58:53 pm
content: Thanks for all your advice, everyone!
Ceramic Capacitor Arrangement; what series do you guys use - Page 1
Forum section: electronics / beginners

author: T4P
author_rank: Super Contributor
timestamp: May 19, 2012, 05:17:07 pm
content: I use "E4" for my electrolytics but am having a hard time deciding what series to use, whether to use E6 which i can fit with the remaining space i have or E12 which i can fit also but which one makes more sense and is more economical to useMy resistor series as recommended by dave

author: Zero999
author_rank: Super Contributor
timestamp: May 19, 2012, 10:51:17 pm
content: I've never heard of E4 before, normally electronics are found in E3, less often E6, occasionally E12 and very rarely other odd values.As a general rule, you only need E3 between 10nF and 1uF as this range is normally only used for supply decoupling, below 10nF you may want to go with E12 or even E24 but it depends on what you're doing,

author: T4P
author_rank: Super Contributor
timestamp: May 20, 2012, 05:16:03 am
content: Quote from: Hero999 on May 19, 2012, 10:51:17 pmit was "devised" as a e-cap sorting by meBut i guess i will use E6 because i have been doing weird stuff that requires more then just 3 values.

author: Zero999
author_rank: Super Contributor
timestamp: May 20, 2012, 11:45:11 am
content: It depends on what's most inconvenient for you, stocking loads of values or using two components in series/parallel to get the right value. It's possible to make any E12 value pretty accurately from just two E3 values or any E24 value from two E6 values. The attached table shows this with resistors but it'll work with capacitors, if they're connected in series rather than parallel or vice versa.

author: T4P
author_rank: Super Contributor
timestamp: May 20, 2012, 02:28:36 pm
content: I think E3 will be fine
Ceramic capacitor marking help - Page 1
Forum section: electronics / beginners

author: Crambone
author_rank: Frequent Contributor
timestamp: November 20, 2021, 01:39:01 am
content: I have 2 ceramic capacitors marked :CM.02MZ5UI measured the capacitor and it reads .02uf but I need to know the voltage?

author: TimFox
author_rank: Super Contributor
timestamp: November 20, 2021, 04:43:24 am
content: CM means "Ceramite", a brand now owned by Vishay.They make a lot of capacitors, so you may have to read through a lot of datasheets on their website.

author: Zero999
author_rank: Super Contributor
timestamp: November 20, 2021, 10:42:55 am
content: The voltage is often not marked on ceramic capacitors.How big is it?Even if it's very small, it'll be rated to over 16V, perhaps 50V.

author: DC1MC
author_rank: Super Contributor
timestamp: November 20, 2021, 10:48:28 am
content: For once wikipedia has an useful article about Z5U dielectric:https://en.wikipedia.org/wiki/Ceramic_capacitor

author: Chris_D
author_rank: Regular Contributor
timestamp: November 20, 2021, 01:02:18 pm
content: From recent experience I also know that CM can mean : 'Murata', if the M is embedded in the C (C stands for company I suppose).

author: TimFox
author_rank: Super Contributor
timestamp: November 20, 2021, 03:02:51 pm
content: Yes: Ceramite uses a straight "CM" marking, not embedded.
Ceramic capacitors with Z as tolerance. What does it means? - Page 1
Forum section: electronics / beginners

author: sean87
author_rank: Regular Contributor
timestamp: July 11, 2011, 12:59:00 pm
content: Hi all,In one of my expiriment boards a ceramic capacitor with written value of "104Z" is broken and I have to replace it. I think this is a 0.1µF Cap, but I am not sure what is that Z is standing for. On the net it is written +80% and -20% tolerance also it says these capacitors are Assymetric?? Can somone explain this please and can I replace this with a 104K cap?Thanks.

author: Zero999
author_rank: Super Contributor
timestamp: July 11, 2011, 05:32:22 pm
content: Tolerance is the acceptable range of values the component can have, in order for it to pass QA.K is 10% so is a suitable replacement for +80% -20%

author: sean87
author_rank: Regular Contributor
timestamp: July 11, 2011, 07:08:37 pm
content: So Z means it can be +80% more or -20% less than actual value?

author: ejeffrey
author_rank: Super Contributor
timestamp: July 11, 2011, 07:22:55 pm
content: Yes. That is a common tolerance rating on capacitors intended for power supply filtering, including a lot of aluminum electrolytics. The tolerance doesn't matter much, and especially extra capacitance almost never hurts.
Ceramic caps and high voltages - Page 1
Forum section: electronics / beginners

author: Ekuryua
author_rank: Newbie
timestamp: October 28, 2010, 01:52:09 am
content: I've been searching for a while but can't find much info about actual breakdown voltages of the typical ceramic caps that come around(class I, I believe). Anyone would have any idea?I've read 300-400V, but that seems quite low.Another question I had was how much does capacitance change with voltage with ceramic caps.Thanks for any more info.

author: Hewitson
author_rank: Contributor
timestamp: October 28, 2010, 02:49:23 am
content: This particular brand (which I often use as they're stocked at Jaycar) are rated at 500V.http://www.suntan.com.hk/Ceramic-Capacitors/TS15.html

author: Time
author_rank: Frequent Contributor
timestamp: October 28, 2010, 02:55:09 am
content: You can get ceramic capacitors well into the 40,000 volt range. They are called 'door knob' capacitors because they look like door knobs. Not sure if that answers your question.

author: Hewitson
author_rank: Contributor
timestamp: October 28, 2010, 02:58:42 am
content: These particular ones are rated for 50kVDC, don't look much like a doorknob to me though

author: Ekuryua
author_rank: Newbie
timestamp: October 28, 2010, 03:09:04 am
content: Thanks for pointing out some higher voltage ones:)Any recs of where to get any of those in EU/with decent s&h fees?

author: Time
author_rank: Frequent Contributor
timestamp: October 28, 2010, 03:16:34 am
content: Quote from: Hewitson on October 28, 2010, 02:58:42 amI seriously doubt that capacitor is rated at 50kVDC. You can't always trust the generic picture for products on distro sites. If you examine that picture closely it says "500V". 50kVDC is enough to breakdown the air between those leads.I am not sure about where you can get them in EU. The brands I am most familiar with in the 10s of kV range are TDK and Murata though. General Atomics makes good HV capacitors with higher capacitances but they are expensive and not usually ceramic. Capacitors of this sort are typically expensive and can't fit into the typical hobbyist budget ($50-100 USD).

author: Hewitson
author_rank: Contributor
timestamp: October 28, 2010, 03:45:45 am
content: QuoteI was wondering why it looked exactly the same as a cap I recently pulled out of a 240VAC circuit!

author: Zero999
author_rank: Super Contributor
timestamp: October 28, 2010, 09:24:31 pm
content: The photo says 500V and there's a difference between the withstand voltage which only has to be for just over a µs and the working voltage which is continuous.Attached is a paper which explains the requirements for different classes of capacitor.
Ceramic Crystal Resonators - how to test themU - Page 1
Forum section: electronics / beginners

author: Jane
author_rank: Frequent Contributor
timestamp: June 10, 2024, 08:33:56 am
content: How can I check if NSB 455J 455KHz Ceramic Crystal Resonator works? The resonator is in remote control that does not work.Is it possible to unsolder it, connect 3V to it and measure it with scope - if there are 455kHz?Or must be that Ceramic Crystal Resonator in a electronic circuit for testing?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 10, 2024, 08:50:43 am
content: It's a resonator; it will pass or shunt frequencies near the resonant frequency, when included in a transfer network. It's a passive device, DC bias does nothing.Setting it up as an impedance divider, from signal generator, to resonator, to resistor, to GND, and probing the resistor voltage, will show the pass resonance peak. Typical impedance is a few kohms, and a comparable resistor is suggested. Beware, bandwidth can be quite narrow (high Q) so a precise and stable generator is needed.Tim

author: wraper
author_rank: Unknown
timestamp: June 10, 2024, 09:01:42 am
content: It could be rattling inside when shaken, sure sign of it's death. They usually die when remote is dropped AFAIK.

author: Gyro
author_rank: Super Contributor
timestamp: June 10, 2024, 09:14:23 am
content: 455kHz ceramic resonators are so cheap that it is simpler just to replace it. Also check for evidence of previous battery leakage, any electrolytic capacitors, PCB cracks etc.

author: SeanB
author_rank: Super Contributor
timestamp: June 10, 2024, 09:19:43 am
content: Cheap enough that repair by replacement is worth it, as they will often crack internally when dropped, not enough to rattle, but enough to change oscillation or not oscillate at all. Easiest test for a remote control is a mobile phone camera, point at lens and press button, and if there is a flickering blue light (IR filter and beyer filter response means the camera thinks the light is blue) then you know both IR emitter and most of the remote works, so if receive is not working then resonator has shifted frequency. Grab a used one from another scrap remote, because we all have old remotes that work, but not the equipment they went with, and do a transplant.Remote controls are simple, common faults are worn buttons, dead batteries, cracked solder joins on the battery contacts or LED, and a dead 100uF 3V capacitor. Fatal is the control IC failing, as those are often blob on board, or a cracked PCB.

author: Jane
author_rank: Frequent Contributor
timestamp: June 13, 2024, 09:34:14 am
content: Thank you for replies.I bought a replacement. But it is yellow and marked 455 kHz - CSB455 , while the original was green and marked like NSB 455J 455KHz . Are they the same?