hybridfree/eevblog-posts huggingface dataset:
selecting a switchmode IC based on pinout? - Page 1
Forum section: electronics / beginners

author: src1989
author_rank: Contributor
timestamp: January 27, 2022, 03:07:58 am
content: i'm looking for websites i can put pin numbers/configurations into to find a compatible switchmode chip; original DIP-8 IC has no part code.Pins 7/8 are commoned and are connected to the rectified mains via the primary winding. Pin 1 comes from rectified mains via a 3.3MegOhm resistor. pin 3 is GND. pin 4 N/C. etc. need to investigate the board again tomorrow...

author: elektrolitr
author_rank: Contributor
timestamp: January 27, 2022, 05:42:12 am
content: I used thishttps://remont-aud.net/ic_power/May be outdated, but so do most of the PWM chips

author: src1989
author_rank: Contributor
timestamp: January 27, 2022, 04:12:13 pm
content: cheers. i was getting confused by it's use of DRV. think i've found 2 compatible ICs...
Selecting an op amp...specification questions...output capability / GBW / etc - Page 1
Forum section: electronics / beginners

author: Skimask
author_rank: Super Contributor
timestamp: February 25, 2013, 12:59:04 am
content: Trying to select an op-amp that'll do what I'm needing.- Dual supply capable, e.g. +12v & -12v (or 15v if I can find one)- Source at most 120mA at the output with the output capable of staying fairly close to the rails, but by no means is it a requirement to get right to them...- Maximum gain will be about 10, no more than that- Maximum frequency input of about 20khzLooks like the TCA0372 will handle what I need.Trying to understand GBW now.The datasheet says GBW is .7Mhz thru the range of the device. If I'm reading it right, this means that at unity gain, I can feed a 700khz signal thru it without getting too much distortion. Similarly, if I'm trying to get a gain of 10, the maximum freq the opamp will work at is about 70khz.... Freq of input X gain = GBW...Is it that simple? I realize there's a bit of a fudge factor in anything like this (e.g. the GBW will likely vary with varying conditions, power supply, input impedance, output impedance, etc). So, is that simple Freq X gain = GBW a decent rule of thumb to go with?

author: w2aew
author_rank: Super Contributor
timestamp: February 25, 2013, 02:11:45 am
content: Yes, that's the simple rule of thumb. But of course, the devil is in the details. One more little point, the BW is the point where the response is down 3dB. The specs hold true under the conditions specified. There are usually characteristics curves that will show how some parameters change under different operating conditions. At the end of the day, it is always a good ideas to build and test, test, test.

author: Skimask
author_rank: Super Contributor
timestamp: February 25, 2013, 03:42:00 am
content: Good enough for me. It's not a critical item. The biggest requirement I'm having an issue with is the max 120mA load and trying to get a decent signal output at the same time.

author: w2aew
author_rank: Super Contributor
timestamp: February 25, 2013, 05:32:44 am
content: Agreed - +/-120mA output, and swinging close to rail-rail - that's a tall order.

author: Skimask
author_rank: Super Contributor
timestamp: February 25, 2013, 05:42:04 am
content: meh...close is a relative term too.If I get 10v on the output with 15v input at the 120mA load, I'll be happy. Anything more than that is icing on the cake...
Selecting board-to-board connectors - Page 1
Forum section: electronics / beginners

author: msr
author_rank: Regular Contributor
timestamp: October 31, 2012, 06:24:54 pm
content: Hello,Im designing a sensor's platform based on a stacked design, so I have two boards which I have to connect trough a board-to-board connector.I already spent dozens of hours trying to select the most appropriate connector but Im still not sure.Some specs Im looking for:- small (about 1cm on the wider side)- should provide a solid connection (a "click" sound)- 15~20 pins, 2 rows- stack height = 5~6mm- polarizedMy first choice was this (from FCI):20021221-00012C4LF20021321-00012C4LFBut they have only 12pin (pitch=1,27mm) and don't provide a solid connection.Then I tried some Hirose DF9 series but the stack height is < 5mm.Now Im using FCI Conan series (pitch = 1mm, 15pins):91910-21415LF91930-21115LFThese fit really well, but now Im worried about their availability.Im in Europe so my prefered distributors are Mouser and Farnell. But just Mouser keeps stock of these connectors and the current stock is ~500 or less. So, I guess if I want to make >250 boards I will get a problem, taking into account that each board has 2 connectors.So, I would like to ask you two questions:1 ) Based on the specs above, could you suggest me a good board to board connector? (which has good availability)2 ) What is the common practice on buying and maintaining connectors stock (from a commercial standpoint)? I guess relying on distributors is not safe.Thanks in advance for your help!

author: sacherjj
author_rank: Frequent Contributor
timestamp: October 31, 2012, 06:48:40 pm
content: Are you holding the boards together by any other means, or relying on the connectors?

author: msr
author_rank: Regular Contributor
timestamp: October 31, 2012, 06:52:09 pm
content: Quote from: sacherjj on October 31, 2012, 06:48:40 pmIm just relying on the connectors. The maximum number of stacked boards is TWO and they are very lightweight (PCB thickness = 0.6~0.8mm), measuring 45x25mm.

author: Smokey
author_rank: Super Contributor
timestamp: October 31, 2012, 09:51:25 pm
content: Check out Samtec.http://www.samtec.com/They are great for all kinds of board-board connectors. You won't usually find them at distributors since they sort of make everything custom when you order it, but they are really good about providing samples and their lead times are usually really good.Check out their board-board connector selector wizard. You give it your parameters and it tells you the appropriate part numbers. Super handy.http://www.samtec.com/search/board_stacking.aspx

author: AndyC_772
author_rank: Super Contributor
timestamp: November 01, 2012, 07:25:56 am
content: The person you need to speak to is Jim at Toby Electronics:http://www.toby.co.uk/

author: Psi
author_rank: Super Contributor
timestamp: November 01, 2012, 07:43:32 am
content: If it's any help, here's how i mounted a button+led PCB vertically on to the main PCB for one of my projects.It's an 8x2 2.54mm pitch right angle header.But it's not removable without unsoldering.
Selecting drive current for opto reflective sensor - Page 1
Forum section: electronics / beginners

author: FrankT
author_rank: Regular Contributor
timestamp: May 14, 2013, 04:59:18 am
content: I'm building a circuit using a SFH 9240-Z Reflective Interrupter (http://www.mouser.com/ds/2/311/FH9240_Pb_free-39520.pdf) and I'm not sure what current I should be driving the emitter at.The data sheet mentions absolute maximum If=50mA. The parameters use If=20mA when measuring turn on/off times, and If=50mA when measuring Vf. I know that the lower the current, the longer the emitter will last.Is there a way to calculate the optimal emitter current?

author: David_AVD
author_rank: Super Contributor
timestamp: May 14, 2013, 06:16:12 am
content: I'd probably use 10mA but check for correct operation at 5mA as a safety margin.
selecting fuse value - Page 1
Forum section: electronics / beginners

author: V_King
author_rank: Regular Contributor
timestamp: July 26, 2013, 01:30:36 pm
content: Hello,trying to figure out what value fuse I should use for the circuit protection from the mains supply side.I've got a power supply unit, which supplies 12V 150mA to the circuitry. The unit does not provide any mains input requirements and I can not find any data sheet for it.Also, I found that it is recommended to have a fuse selected with constant load of 75%, and in other reseources they recommend to use the x2 rating fuse for the constant load.Any input is much appreciated.Cheers

author: Psi
author_rank: Super Contributor
timestamp: July 26, 2013, 02:08:37 pm
content: Does your device have a large inrush current. (like an audio power amp with large 10,000uF caps)If you have large inrush you'll want to use a slowblow fuse.The figures 75% -> 100% (1.3x -> 2x) are the typical ranges.If you have little to no inrush then 1.3x should work fine.

author: V_King
author_rank: Regular Contributor
timestamp: July 26, 2013, 04:40:06 pm
content: Thanks for the answer. I have two high value caps at the power input, so slow blow (same as time delay?) fuse it is. On the other hand, is there an easy to implement way to prevent the surge at the beginning of the cap charge and use fast blow fuses?I am more puzzled with selecting the current rating for the fuse.Power consumption at 12VDC and 150mA, is 12*0.15=1.8WSo at 240VAC RMS (340V true) I would get only 1.8 / 340 = 5.3mA (not taking phase into account)Even if the power supply efficiency is 50%, the current would be 11mA.I looked in the familiar output switch mode power supplies in farnell's catalogue and they show current input at around 50-100mA for 240VAC inputs. Would 100-150mA fuse would be the value to choose?

author: PuterGeek
author_rank: Regular Contributor
timestamp: July 26, 2013, 10:48:24 pm
content: The fuse rating depends on the fuse type, opening speed and the load. If you don't have input ratings you should at least measure the steady state current.If you look at the data sheet for a fuse you will find how long an overload takes to blow the fuse. For a typical 5x20mm medium acting fuse, a 400% overload will blow in 40 to 2000 ms while a 210% load will take a maximum of 10 minutes. A low current fast acting fuse takes 3 to 300 ms @ 400% and 30 minutes max. @ 210%.These values are from Littlefuse but should be typical.
Selecting fuse which do not burst like glass fuse - Page 1
Forum section: electronics / beginners

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: March 04, 2016, 04:23:51 pm
content: I have 220Vac/50Hz application which require a fuse in series in case of overcurrent. Earlier I was using glass fuse. But I have noticed whenever it blows it goes bang. I dont want that it create such bang.I have seen this video:& noticed that ceramic fuses dont create such noise when blown. Can I replace glass fuse by these.Disadvantage I read are:1. When ceramic fuse blows, there is no physical mark on cermaic to identify that it i blown. Only way is by multimeter. While glass fuse gets black & can be identified by eyes.2. Cermaic fuses are slower than glass fuse in breaking. Can it affect the circuit?Any other point, or any other fuse type which dont get blown by such noise.Input is 220Vac,50Hz, load is around 400mA.

author: mmagin
author_rank: Frequent Contributor
timestamp: March 04, 2016, 04:32:56 pm
content: A fuse with full specifications will not only give data on the current/time curve where it opens up, but it also gives a maximum current interrupting rating, that is how much current is available on the circuit and it is still capable of safely interrupting it (at the rated voltage). For example, I think those BS1362 fuses used in UK plugs are rated for 6 kA at something in excess of their mains voltage (260 volt?).It's not merely that the ceramic is stronger than glass, but there's various fillers which help quench an arc, like sand.

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: March 06, 2016, 02:15:41 pm
content: I had 250V,0.750A glass fuse. We were shorting the output to see if fuse works correctly by limiting ac current to max 5A. This was for testing only so that in case any thing goes wrong what can happen.It burst like bang.I will replace it with ceramic fuse.

author: Jeroen3
author_rank: Super Contributor
timestamp: March 06, 2016, 05:03:50 pm
content: If you don't want a bang, search for higher rupture or breaking capacity fuses. Or maybe consider a MCB. (circuit breaker)And:1. Add a power-ok light to your product.2. They don't have to be, such as the unicorn hair fuses in your multimeter.
Selecting IC for auto-switch to battery, in case of mains(dc) absent - Page 1
Forum section: electronics / beginners

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: September 14, 2020, 11:47:20 am
content: 1. I have a system, where:a) Input SMPS is 11-14V, where it is used to charge battery with 2.5Amps and supply 12.5Amps to load also.b) SMPS is used to charge lithium battery via LM3478 and dedicated charging IC.c) When SMPS is present, it should supply to both load(12.5Amps) & charge battery. Battery should not be connected to load.d) In case SMPS is absent, emergency , then load should shift to battery in that case only.2. Buck-boost LM3478 is for maintiaing voltage 12.6V & boost LM5155 for load voltage 12.3V/12.5Amps.3. Precondition is:a) Shift battery to load in case of smps absent only.b) GND need to be common for all, so high side fet need to be chosen.4. I checked Linear Technology LTC4414, it supply this diagram:a) Can i avoid diode UPS840(or whatever equiavalent of 12.5A), since SMPS will not allow reverse current in any case?b) It has P-channel mosfet for drive, my laod current is 12.5Amps, so is there any other IC or way where I can use N-channel on high side?c) Any other better solution for this?

author: rohmeooo
author_rank: Newbie
timestamp: September 15, 2020, 02:51:10 am
content: 4) a. SMPS may not allow reverse current when operating normally, but it may not have that functionality without input power. Basically, is it happy with voltage on it's output and nothing on it's input.4) b. You should be able to find a suitable PMOS for 12V/12A. eg SI7157DP-T1-GE3 has <2mOhm resistance for 288mW of loss at 12A (.2%), seems reasonable to me. Or browse for better herehttps://www.digikey.com/short/z280z7However, these devices actually operate in a sort-of linear mode, so you can't just put a super low resistance FET down and expect it to operate at RDSON.Look at V_fr and V_RTO in the electrical characteristics table. Basically, the FET will regulate to 10-32mV forward voltage--that's your "ideal diode"'s forward voltage, irrespective of min RDSON. So whether it's got 1A or 12A, it'll drop 32mV. at 12A that's 32mV/12A = 2.7mOhm. Basically, it does you no good to get a FET lower than ~2.7mOhm. In other words, at 12A you're losing 12A*32mV = 384mW--doesn't matter how many FETs you put in parallel. Seems reasonable to me (still ~.3% loss)There are similar devices with a charge-pump for driving NMOS. Or with lower forward regulation voltage. Don't know off the top of my head but "power path controller" "power OR controller" "ideal-diode controller" are your search terms.Also some with 2 outputs or you can just put 2 of the LTC4414 in parallel. See figure 1 of the LTC4414 datasheet. Bear in mind the higher voltage prevails so your SMPS will have to always output more than the battery.Why not always run from the battery, letting the input power provide as much current as is needed to keep the battery topped off?
Selecting ptc resettables for home made arduino - Page 1
Forum section: electronics / beginners

author: amateur_25
author_rank: Regular Contributor
timestamp: April 04, 2012, 02:48:02 pm
content: HiI've decided I'll put ptc fuse before the regulator that way it should protect my entire circuit right?I know the genuine arudino use a 500ma fuse. So do I just get one for 500ma tripping current?

author: djsb
author_rank: Super Contributor
timestamp: April 04, 2012, 04:10:25 pm
content: In my experience you need to choose one by actually testing it with a power supply and an ammeter. I have resettable fuses fitted to some boards at work which are rated at 500mA but they actually trip at around 750mA. They do not go from fully open circuit to fully closed either. There is a gradual increase in resistance as the fuse gets hotter and it can hold a steady temperature. At a certain point (which you need to measure) the resistance increases exponentially and the fuse goes open circuit. You need to measure the HOLDING current (at your specified voltage) and the TRIP current. There are values mentioned in the data sheet but I wanted to test things for myself (better safe than sorry).David.

author: westfw
author_rank: Super Contributor
timestamp: April 05, 2012, 12:36:51 am
content: A fuse (and especially a PTC resettable) is generally too slow to protect your circuit, but most definitions. Hopefully it will be enough to protect the device (eg your laptop) powering your circuit, or at least the environment around the two of them from the fire that might otherwise result.(for instance, AFAIR, the PTC in the official Arduino boards was added because shorts on a protoboard were causing "unprotected" laptops to reset when the 5V voltage dropped.)
Selecting replacement battery management IC - Page 1
Forum section: electronics / beginners

author: FrankT
author_rank: Regular Contributor
timestamp: July 30, 2021, 11:41:32 pm
content: I was replacing the batteries in my Fly12 (bicycle light/camera) - a pair of batteries in parallel, with a management PCB, when I stupidly forgot the circuit is under power and grabbed then with metal clamps - lots of sparks, no smoke, but the circuit no longer works.I reverse engineered the circuit and it looks identical to the samples in chips like this (sot-26 version)...https://datasheet.lcsc.com/lcsc/1804140042_Diodes-Incorporated-AP9101CK6-ADTRG1_C151339.pdfThe problem is, there are many variants of chip with different charging characteristics - in this datasheet about 60 (starting on page 12).The markings on this chip is Y1AF.Does anyone know an easier way of finding this exact chip (I've just spent an hour scanning datasheets).Alternatively, can someone recommend a chip with a safe set of protection parameters to work with a pair of NCR18650B in parallel?Thanks,Frank
Selecting Replacement Electrolytic Capacitors - Page 1
Forum section: electronics / beginners

author: Grimmer04
author_rank: Newbie
timestamp: February 09, 2025, 06:52:57 pm
content: Repair is complete and the tape deck is working well. While fixing the issue with the PS I found that the 6 caps I pulled were slightly bulged or leaking. I replaced them all. This has me thinking that all the other electrolytics are probably shot too. As I was building my list of replacements needed, I thought to myself that this would be so much easier if I just get all the same voltage and just match the uF. All of the capacitors except 2 that are actually in the audio path are polyester film and tiny value ceramics. Most of the electrolytics that are in the amplification circuit go to ground. My question is. Would getting say all 16v capacitors be detrimental? The voltage values vary from 6.3v to 16v. I would certainly match the uF and keep an eye on the ESR. I would buy audio grade even though I suspect that is not really needed in this case.Thanks,

author: Xena E
author_rank: Frequent Contributor
timestamp: February 09, 2025, 08:38:16 pm
content: The range of working voltages you have there won't make any functional difference if they are all the same voltage rating.Buy decent quality ones of course, (Rubycon are my favourites), but as you say they are all basically supply filtering then getting super duper audiophile types is up to you, but perhaps not necessarily needed.X

author: tester43
author_rank: Regular Contributor
timestamp: February 10, 2025, 02:02:24 pm
content: check, for example- if non of them is non-polarized.- distance between terminals- temp ratingIn general, when you select them from options, you will find several "the same" capacitor with differences in physical sizes

author: Grimmer04
author_rank: Newbie
timestamp: February 10, 2025, 06:49:30 pm
content: They all visibly look the same with a 5mm lead spacing. Thanks for the help, this will be a good time saver.

author: Laval
author_rank: Regular Contributor
timestamp: February 10, 2025, 06:58:34 pm
content: QuoteThese are the important parameters. Some brands of capacitors (Nichicon for example) also have a series often denoted by 3 letters (UHE, ...). They mean geneal purpose, low esr, etc. You may want to pay attention to this in some cases.

author: wraper
author_rank: Unknown
timestamp: February 10, 2025, 07:01:17 pm
content: Higher voltage is fine, as long as they fit. Any capacitors will work, but it's preferable to use long life series from a decent brand if you care about them lasting for decades.
Selecting right buffer for dac - Page 1
Forum section: electronics / beginners

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: March 16, 2015, 08:13:46 am
content: I am using TI's Dac8568 (16 bit 0-5V).I need a buffer IC at output of each dac.1. Buffer IC should be operate from single supply 5V.2. Able to supply upto 10mA (flexible on this spec)3. Rail to rail; full 0-5V4. Low offset5. Temp: -40C to +85CI looked at EL5127 & MAX4208.1. EL5127 is low power & rail to rail. When load is +5mA the drop is 80mV.2. MAX4208is very low pwer, low offset, rail to rail. Only thing I didn't find the drop in output voltage with load?Any other buffer which I can select for better performance with 16bit dac.

author: Psi
author_rank: Super Contributor
timestamp: March 16, 2015, 08:46:49 am
content: Be aware that even rail-to-rail opamps don't got all the way to the rails.

author: JoeN
author_rank: Frequent Contributor
timestamp: March 17, 2015, 03:56:12 am
content: Is this a troll?That DAC already has buffers on every output and they aren't optional so whatever you add afterwards is just going to make the buffer's spec worse. But the spec of the built-in buffers is actually pretty decent. Read the datasheet.
Selecting right digital buffer - 20us switching - Page 1
Forum section: electronics / beginners

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: January 01, 2015, 05:12:32 pm
content: 1. I have a microcontroller programmed to switch 16 I/O pins at 20us interval to drive certain load at each pin. I have to operate at 3.3V.2. Now I want to buffer the MCu pin from load with a buffer.'3. I have been reading about TI's SN74ALVC16244A. It is 16 bit buffer, with 3ns Tpd.4. What will be each pin max drive current when all pins are turning on at same time. Datsheet says +-24mA drive, is it for all pin together or individual?5. Any other better buffer?

author: tggzzz
author_rank: Super Contributor
timestamp: January 01, 2015, 05:30:37 pm
content: Quote from: Vindhyachal.takniki on January 01, 2015, 05:12:32 pm24mA/pin, but that varies with supply voltage, you mustn't exceed total package power and supply current limits, and you'll have to be very careful to mitigate ground bounce.

author: dgtl
author_rank: Regular Contributor
timestamp: January 01, 2015, 05:33:50 pm
content: What kind of loads are you driving? Push-pull output needed? Or just separate transistors or transistor arrays?

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: January 02, 2015, 04:38:37 pm
content: I have to drive a npn transistor which is used as switch
Selecting right soldering bit - weller - Page 1
Forum section: electronics / beginners

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: December 25, 2014, 06:36:01 am
content: 1. I have a weller soldering station & need to search between right soldering bit.2. I have to select bit for WSP-80.3. I solder component liken QFP , SOT-223 , So-8 , TSOT23-5 & smd resistor & caps of 0603 , 0805.4. I have attached the pdf for the range of bits from which i can select.5. I have reading below website:http://www.hakko.com/english/tip_selection/work_drag.html#type_bSo I think Shape B will be best suited for my requirement.6. So from attached choices,I have chosen"T005 44 489 99 , LT 1A , Round tip , width - 0.5mm , length = 14.0mm"7. Any suggestions?

author: nanofrog
author_rank: Super Contributor
timestamp: December 25, 2014, 07:17:46 pm
content: Chisel types (type D on the Hakko page) make better general purpose use tips IME. You'll want a few different sizes, say 1.6mm and 2.4mm at the very least (LTA & LTB respectively; there are smaller and larger), so you can match the tip size to the pad/hole being soldered (want them to be as close to the same as possible).You might also look into drag soldering, which they offer a couple of special tips for performing this particular technique (LTGW & LTGW2; there's a spoon/well in the end of a it that holds a molten ball of solder). A very fine tip can be useful for tacking the corners.

author: zapta
author_rank: Super Contributor
timestamp: December 25, 2014, 10:01:04 pm
content: You can see here drag soldering with hoof tip. Very useful.

author: VK5RC
author_rank: Unknown
timestamp: December 25, 2014, 11:33:45 pm
content: +1 for small chisel tip, the flat surface on a chisel means if you need to transfer some heat eg ground plane you can, a round tip doesn't do heavier heat transfer well.Had a wsp80 for 7 years, love it.

author: LabSpokane
author_rank: Super Contributor
timestamp: December 26, 2014, 07:24:16 am
content: +2 on the chisel. I think a 1.6mm is best all around, but you might want one step smaller for SMT work.

author: Howardlong
author_rank: Super Contributor
timestamp: December 26, 2014, 07:41:55 pm
content: I run both an LT1 and an LTB on two irons.The LT1 is for delicate work and the LTB when a bit more heat transfer is needed.

author: tautech
author_rank: Super Contributor
timestamp: December 26, 2014, 08:45:35 pm
content: Best advice is to avoid any tips with a profile like the first one on page 1.They might be OK for very fine work but their heat transfer is poor.LT K is the best type profile for heat transfer and as others have said a chisel end is the most preferred.I find a knife like LT KN (last page) useful occasionally for rework, you can heat both pads of passives and wipe or pick them off.
Selecting Right value of PSC and ARR values for timer - Page 1
Forum section: electronics / beginners

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: July 05, 2020, 08:02:28 am
content: I am using TIM3 of Stm32f407ve MCU.CPU is running at 168Mhz and clock to TIM3 is 84MhzNeed to select right values of PSC and ARR for accurate timing.is this correct assumption?Time_us = ( (psc+1)*(arr+1) ) / 84Mhz ??

author: Siwastaja
author_rank: Super Contributor
timestamp: July 05, 2020, 08:15:15 am
content: A counter-question:You have reached a very logical formula with your own thinking. Why not just do the last step, and test it and see if it gives what you expect?Test it with fairly low values of psc and arr so that you easily see if your formula has an off-by-one error or not. (For example, if you use arr=60000 and your idea of +1 is wrong, the difference is only 0.002%, not easily measurable, but if you set arr=10 you already see 10% error if this is the case.)
selecting smd capacitors by series - Page 1
Forum section: electronics / beginners

author: Douglas
author_rank: Newbie
timestamp: April 10, 2022, 05:35:57 pm
content: i am replacing bad smd capacitors on a bose radio cd. the cd player skips rubycon and panasonic have lots of series... how do i select the best smd capacitor for my use?should i choose the smd capacitor by the materials it is made with example polymer etc. is there explanations for there series thanks i am a bit confused

author: inse
author_rank: Super Contributor
timestamp: April 10, 2022, 06:04:59 pm
content: In detail, this is a difficult question.If you want to make sure to select the appropriate part, you would have to look it up in the service manual.The suppliers have different series specific for ESR, lifetime, temperature rating, size, mounting options and more.Polymer caps have an excellent ESR, but suffer from leakage current, so ideal for power supply filtering but inappropriate for signal path or timing applications.
Selecting the correct adapter for my Amprobe TMD56 data-logging thermometer - Page 1
Forum section: electronics / beginners

author: Teemosan
author_rank: Newbie
timestamp: May 01, 2017, 02:05:19 am
content: Hi all,I'm new to the site.I just bought an Amprobe TMD56 data-logging thermometer. This device here:http://www.amprobe.com/amprobe/usen/hvac-tools/thermocouple-thermometers/amp-tmd-56.htm?pid=73414It takes 4 AAA batteries, but has an optional DC adapter input. In the manual it lists the adapter specs as:DC IN: 12Vdc, 150mA,It's positive (internal) polarity, jack size 3.5mm x 1.35mmI guess I don't understand this correctly, because I thought if the device ran on 4 x 1.5v AAA's it would require a 6V adapter. For amps I'm guessing it'll only draw what it needs so if I get an adapter that's = or > 150mA it would be OK. Is that correct?So first I need to clear up my misunderstanding of the difference between the devices battery operated voltage and the adapter voltage. Or is there even a difference?Then I need to get a correct adapter. I see a lot of these multi adapters on Amazon, eBay, etc - devices like this:https://www.amazon.ca/IKOCO-Universal-Regulated-Replacement-Electronics/dp/B01JFZ8BO2/ref=sr_1_48?ie=UTF8&qid=1493597032&sr=8-48&keywords=12v+adapterWould something like that work?Thanks

author: Paul Price
author_rank: Super Contributor
timestamp: May 01, 2017, 02:14:20 am
content: The output voltage is stepped-down in the instrument to a regulated voltage near the battery voltage and that is why it is 12V, which is a convenient off-the-shelf and popular spec. which also possibly lowers cost. You could use probably anyregulated12V adaptor you can find that matches the connector and has >150mA output on your instrument since the power requirements are very low and almost any 12V wall-wart or brick regulated 12V power supply is rated >150ma.

author: Teemosan
author_rank: Newbie
timestamp: May 01, 2017, 02:43:38 pm
content: Paul, thanks, I appreciate you taking the time to answer, and the explanation. Easier than I thoughtI'll get one based off that info.thx,TimEdit: Also, being new to the forum, I can't see a way to select best answer or mark as solved. How do I do that, or do the mods close out the threads?
Selection of low power converter for a battery powered project - Page 1
Forum section: electronics / beginners

author: ChenBH
author_rank: Newbie
timestamp: July 30, 2020, 08:42:47 am
content: Hi, hope you are all good.I'm designing a 12V battery monitor board that should measure the battery's voltage once an hour and send it via 433Mhz RF signal.I'm using the TPL5110 timer chip to cut power once the MCU is done (5-10 sec working time once every hour, not transmitting the whole time).(Attached a system schematic)When transmitting or receiving, the whole system draws 100 mA max. When "sleeping" the current is the TP5110's Iq (50nA).I currently use TI's LMR33610 Step-down Converter just to stay in the 70-80 percent efficiency but I surely have second thoughts about this.Will a voltage reg be better in terms of efficiency? are there (ultra) low power lines for Step-Down and voltage regs which can be used for 50nA to 200mA?Do I really need the 50+% efficiency for 50nA @ 5V which in turn be 25nA max @12V 70Ah battery?Thanks and good health,Chen

author: VooDust
author_rank: Regular Contributor
timestamp: July 30, 2020, 10:24:20 am
content: I could be wrong but I think at 50nA none of the efficiency curves apply. Also, quiescent current of the converter probably outweighs 50nA by orders of magnitude.I like the project idea. Is it for car battery monitoring?

author: ChenBH
author_rank: Newbie
timestamp: July 30, 2020, 02:45:13 pm
content: Yes,that's a caravan's battery.We forgot the 12V switch on one time too many.Well, it sure looks like all the switching regulators are ommiting the sub 1mA range in their efficiency vs output current, where a pretty linear curve is appearing.
Selective Zero Point Switching - Page 1
Forum section: electronics / beginners

author: TheDood
author_rank: Regular Contributor
timestamp: September 15, 2019, 05:38:26 am
content: Say you have an AC signal at 100hz. Is it possible to pick the exact oscillation that you zero point switch? If there's 100 oscillations per second, could you switch at the zero point of every 1st & 23rd osscillation, for example? Is there such a device or cct that is commonly used that accomplishes this?

author: gigabyte091
author_rank: Contributor
timestamp: September 15, 2019, 06:21:01 am
content: You could use zero cross detection circuit, and then feed that signal in arduino where you can count pulses and switch output when you want (eg. 1 and 23rd zero cross of the AC signal)

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 15, 2019, 06:36:36 am
content: You may be missing some terminology:Oscillation: an alternating phenomenon, usually periodic.Cycle: a full... cycle, of an oscillation.Also, what would the 1st and 23rd cycles be referenced to? If the oscillation is steady state, it doesn't really have a beginning or an end. (An ideal sine wave, for all times t < 0, is identical to all times t > 0, give or take a simple symmetry.) Would the count repeat immediately, so the 24th cycle from one count is the first cycle of the next count, and so on? Or should there be some dwell in there also, in which case how much?But in any case, yes, that's a thing: a cycle-skipping controller, is typically used for AC loads, that have high power factor, and large time constants, so that the skipped cycles average to a smooth output. In short: heaters, thermostats, that sort of thing, are a prime application.The pattern of cycle-skipping may resemble PWM, or a sigma-delta converter, or anything else that works.PWM would run, for a duty cycle 0 <= D <= 1: on for N*D cycles, off for N*(1-D) cycles, for a total (repeating) period of N cycles, or a frequency of F_mains / N.Sigma-delta is something of an approximation method, which can give lower ripple than PWM. A running average is calculated by the controller, and the output is turned on or off depending on whether that average is above or below the setpoint.The simplest, commonest circuit you could make, that accomplishes this, would be a simple hysteretic controller (i.e., a sensor's output is compared to the desired setting, and this turns the output on or off directly), paired with a zero-crossing switch. Downside, this gives much slower cycles, and quite a lot more ripple (fluctuation in sensed value), than a PWM or SD control would. (Most home thermostats do operate this way, in part because the furnace or A/C should not be switched on and off too quickly.)Tim
Self Biased Zener Voltage Reference - Page 1
Forum section: electronics / beginners

author: soligen
author_rank: Contributor
timestamp: July 16, 2015, 11:16:51 pm
content: HI EEVBloggers. First time poster here.I'm not only new here, but also to electronics as a hobby. I've been watching many videos and googling to learn as much as I can, and I find EEVBlog a great resource. I am very much a beginner.I have been playing with voltage and current regulation, and decided to find a way to refine my voltage reference. I've been researching ways to do this without simply buying a voltage reference (learning more this way) and I found the diagram below that I think fits what I am trying to do very well, as I am likely to have an extra op amp to use. The only issue I have with this is the calculation for C. Being an inverse of the time constant, I just cant seem to come up with values that seem reasonable. If this instead were RC >= .001 then a 10k resistor gives a .1uF capacitor, which is reasonable. But, the formula in the diagram boggles me.Can anyone help me understand this? Is the formula on the diagram correct? I don't really understand why the capacitor is needed.original page:http://www.embedded.com/electronics-blogs/embedded-round-table/4425816/2/Voltage-referencesThanks

author: TimFox
author_rank: Super Contributor
timestamp: July 17, 2015, 01:35:06 am
content: The equation for Rf x C is wrong (dimensionally inconsistent).Probably should have been Rf x C > 1 msec.E.g., 10 k ohm and C > 0.1 uF.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 17, 2015, 01:47:11 am
content: FYI, LMCxx won't give best results here -- high noise voltage. A bipolar amp with e_n/i_n ~= Z of the circuit will do best.Unless it's a buried zener, this is probably orders of magnitude away from useful, though. In which case, even a LM358 should be sufficient.Tim

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: July 17, 2015, 02:21:45 am
content: Hi group,I believe that Rs, which is the start-up resistor is shown in the wrong position. It should be connected from cathode of the Zener to Vdd.Rs is normally much greater in value than Rbias. This is done to reduce the variation in Zener current with changes in Vdd.The whole idea of the circuit is to operate the Zener diode at constant current.Regards,Jay_Diddy_B

author: soligen
author_rank: Contributor
timestamp: July 19, 2015, 12:07:02 pm
content: Thanks for the help.No, this is not a buried zener, bu tthanks for mentioning it, as I didn't know what one was until I looked it up.I'll be using a TLC272 op amp (at least to start) because it is what I have.I'll be experimenting now. I'll post back when I have something.
Self-flashing LED oscillates when in OFF state of cycle - Page 1
Forum section: electronics / beginners

author: ResR
author_rank: Regular Contributor
timestamp: February 01, 2016, 08:58:11 am
content: I was testing two different self flicker LED's with a piezo element parallel to the LED with current limiting resistor to power supply to listen what sound it makes and I found out that L-56BSRD/B has odd oscillation when it is in off state, it sounded like two different frequencies - one short clicking sound 4 times per light cycle (clock signal?) and other was high pitch sound that turned off when the LED went on. Can anyone check this with an oscillator and can it cause interference to other microcontrollers? Could it have a built in microcontroller? I always thought it had something easier like astable transistor oscillator in IC form until now.

author: amyk
author_rank: Super Contributor
timestamp: February 01, 2016, 09:14:57 am
content: I remember reading somewhere that flickering LEDs may use the same chips as in musical greeting cards, so you may hear a familiar tune from them, although if you don't hear anything recognisable it could be that they use the defective ones which still have some sort of output.

author: Zero999
author_rank: Super Contributor
timestamp: February 01, 2016, 09:23:44 am
content: The part number he gave is just a normal flashing LED.http://www.farnell.com/datasheets/1864128.pdfIt could be a number of things which is causing this. The astable multivibrator inside the LED probably runs at a much higher frequency, than the flash rate and is divided down. It's possible the peizo is oscillating because of some non-linear effect inside the LED. Perhaps removing the piezo and looking at the waveform on an oscilloscope would provide a more clear picture.
Selfdesigned Mosfetdriver Board - Page 1
Forum section: electronics / beginners

author: fancy_user_01
author_rank: Newbie
timestamp: January 09, 2023, 03:12:36 pm
content: Hello,I am a new member of the community.I am here because I have a problem with my own designed board.It is a mosfetdriver board based on the UCC27517, which I combined with a IRL520 to control LED strips.The LED strips are controlled over the website I made with an ESP8266.A couple of weeks ago, the board arrived already assembled from jlcpcb...connect everything up and as soon as I touch/connect anything to the terminal,where the microcontroller signal is supposed to go, the LED goes on. Even though it is supposed to be off.When I connect the ESP I/O pin, nothing happens either. The LED goes on as soon as it touches something connected to ground and I don't understand why.So my question is, why does the LED go on when it is not supposed to?And how do I troubleshoot something like this?video:https://imgur.com/a/LaI8IxlI added the schematic, pcb layout and a wiring schematic drawn on kicad.I hope I was able to express myself well enough and that I am just overlooking something silly...because I am starting to loose my mind!

author: BillyO
author_rank: Super Contributor
timestamp: January 09, 2023, 04:13:54 pm
content: It looks like it should work.Have you measured the signal coming from your ESP?Also, it might be handy to include a macro shot of the built up board.

author: alexanderbrevig
author_rank: Frequent Contributor
timestamp: January 09, 2023, 04:29:06 pm
content: You connect GND to the ESP too right?

author: fancy_user_01
author_rank: Newbie
timestamp: January 09, 2023, 06:05:47 pm
content: Ooooh damn it, that is the solution.It is amazing how I manage to overcomplicate things...Thank you anyways.
Selfmade USB-Cable Troubleshooting - Page 1
Forum section: electronics / beginners

author: rudepurple
author_rank: Newbie
timestamp: May 08, 2020, 12:07:43 pm
content: Hello everybody,i have some trouble with a selfmade usb cable. I want to charge my Sony Hdr-AS50 Actioncam(https://www.sony.com/electronics/actioncam/hdr-as50) with a powerbank(https://www.anker.com/store/powercore-13000/A1215011). Using the original cable that came with the power bank everything works fine but not with my selfmade one. Even weirder is that both cables work with a older power bank.I am using a A-Type Connector and a Micro-B Connctor (The orignal cable uses the same). The wiring is done to the following schematic:Using a voltmeter i reasured the pinout of the two cables is identical.Can someone please explain me this behaviour?

author: Mp3
author_rank: Frequent Contributor
timestamp: May 08, 2020, 12:22:40 pm
content: Your schematic is not in your post.I am going to guess that your diy cable has the wrong resistance from end to end and the smarter power bank is checking this and refusing to charge it

author: rudepurple
author_rank: Newbie
timestamp: May 08, 2020, 12:27:55 pm
content: i ran into trouble with google drive there.Should be fixed now.The cable in the image is my second attempt. I cut the original cable and just shortened it and put my own connectors on it. Shouldn't the end to end resistance stay the same?Thanks!

author: Mp3
author_rank: Frequent Contributor
timestamp: May 08, 2020, 12:46:35 pm
content: It probably should be the same resistance then. I imagined you used some different cable.and what happens you connect ID to ground?

author: rudepurple
author_rank: Newbie
timestamp: May 08, 2020, 01:02:11 pm
content: I was thinking about the ID pin too, but according to the usb standard it only should be pulled to ground in order to get a host cable.Probing the working cables shows that ID and GND are not connectedI get some deviating measurements on the resistance of the diy cable. So for now i will further investigate the resistance idea following this website:https://www.tablix.org/~avian/blog/archives/2019/06/measuring_usb_cable_resistance/. I am using cheap connectors. Mayber that is the problem.Thank you.More ideas are still welcome

author: Mp3
author_rank: Frequent Contributor
timestamp: May 08, 2020, 01:28:56 pm
content: Quote from: rudepurple on May 08, 2020, 01:02:11 pmGood luck. I know the ID pin is not needed by the usb standard, but Sony is well known for ignoring (or deliberately messing with) wiring/protocol standards

author: jc101
author_rank: Frequent Contributor
timestamp: May 09, 2020, 10:33:34 am
content: Is the D+ and D- really crossed over like that?Might mean the camera detects the wrong type of charger, although if they both measure the same...Also try without any D-/D+ connected at all, that should delivery 500ma if the camera is willing to take it.
Semaphore time out or Oddly behaving micro SD card - Page 1
Forum section: electronics / beginners

author: G7PSK
author_rank: Super Contributor
timestamp: March 26, 2015, 09:41:16 am
content: Not sure under what category this should be if at all on this site, so its here as I do not understand whats going on which makes me a beginner.I have just purchased an 64 GB micro sd card from Ebay for under £5. I thought that it could well be less than the claimed size and was interested to see but that is not the case. when I came to try and load large files onto it they failed to load and I got the message "semaphore failure" I tried the card in a USB adapter and the same files loaded without any trouble. Anyone have any ideas as to what is going on, I have tried the SD card on 2 computers with the same message coming up on the same files the card appears to function correctly in a camera as well as in the usb adapter

author: marshallh
author_rank: Unknown
timestamp: March 26, 2015, 08:03:50 pm
content: Throw the card in the trash, you can't trust it. It's probably a 1GB card with hacked CSD register to report a different size.Some readers try to enumerate the card size by reading the last block. Obviously in this case this would be off in nowhere-land.Semaphores are not explicitly used for card communications. Sounds like a higher level software stack is choking somewhere.There are all manner of ways the card could fail in one reader but work in another.

author: G7PSK
author_rank: Super Contributor
timestamp: March 26, 2015, 09:27:59 pm
content: I sent it back, but in a USB adapter I put several videos onto the card totalling nearly 8GB and it was not full but as an straight micro SD it would load or read the files.
Semi-homemade 19V Adjustable bench PSU - Page 1
Forum section: electronics / beginners

author: antolanca
author_rank: Contributor
timestamp: February 27, 2014, 09:15:50 pm
content: Hello everybody.Right. I want to build a Bench PSU using a laptop charger and connect a couple of LM317's to adjust current and voltage.The charger has got 19V 3.95A (from my toshiba satellite) and I want 1A at at least 12V.Now comes the tricky part.I'm expecting to have a voltage drop because of the LM317's so the max. voltage will probably be 12 to 15V.It's the amps that mess me up.Acording to Ohm's law I would need a 19R 19W Load Resistor to get 1A which is my target. But the output of the transformer is 75.1W.Now, how much power and resistance do I need to get the 1A?I've laded a schematic to give you a better idea. the load resistor is on the left.Thanks

author: Zepnat
author_rank: Regular Contributor
timestamp: February 27, 2014, 09:33:20 pm
content: The 19vpower supplycharger should be regulated and not need any load resistor just get rid of it it will waste power. If the charger has 3.95A available the limiting factor will be the LM 317 which I think output up to about 1.5A before self limiting.

author: mos6502
author_rank: Frequent Contributor
timestamp: February 27, 2014, 10:41:28 pm
content: Bad, bad, bad idea to use the LM317 for current adjustment. The droput voltages add up. You'll end up getting maybe 10V out of your 19V. In addition, the current sense resistor will dissipate a lot of heat.Either use one LM317 and forgo the current adjustment. That will get you a decent, usable 1.25-15V/1.5A supply with your 19V input. Or use a different regulator. The LM723 would be a good choice. It has the advantage of having the pass element separate so you can choose that for the current you need. It also has a current limit settable by a resistor. You could make the current limit switchable with a toggle switch by using different resistors.

author: rdl
author_rank: Super Contributor
timestamp: February 27, 2014, 11:35:50 pm
content: You would get 12-15 volts out. The problem is that you have made the current limit adjustable. That 5k pot is going to have to be capable of carrying the maximum current. It is probably better to use a pass transistor with an op amp for the current limiting, something like what is shown in the data sheet on page 21.
Semiconductors for low temperatures (military grade?) - Page 1
Forum section: electronics / beginners

author: PP7BB
author_rank: Contributor
timestamp: October 25, 2016, 10:09:47 am
content: I am confused. Usually I do not need semis for low temp but now my project require to use them.For ICs situation is clear - in datasheet must be written range of temperatures which must comply to design requirements.What about diodes and transistors? I usually see only maximum allowed junction temperature. Does it mean that such device can work only from 0 not for sub zero temperatures? Sorry guys question is little bit stupid but I have never made anything for less-than-zero.