hybridfree/eevblog-posts huggingface dataset:
Mixing old and new lead acid batteries in parallel - Page 1
Forum section: electronics / beginners

author: e100
author_rank: Frequent Contributor
timestamp: May 09, 2019, 08:53:51 am
content: Are there any disadvantages or issues if you put a new lead acid battery in parallel with an 8 year old lead acid battery?The goal is to have more Ah at the same voltage.I'll be individually charging them to the same voltage then putting them in parallel with a temporary resistor in between them to limit the current. Once equalised I'll just treat them as one large battery.

author: paulca
author_rank: Super Contributor
timestamp: May 09, 2019, 08:56:57 am
content: I believe the old battery will not hold it's peak voltage and will pull the new one down with it. So you will lose effective capacity on the new battery.My main solar battery when brand new would hold 13.1V for 24 hours after charge. Now, about 300 50% cycles in it drops to 12.9V within a few hours.You could test both your batteries, by boost charging them for an hour, then floating them for a few hours and finally leaving them overnight to see how they hold their voltage.

author: e100
author_rank: Frequent Contributor
timestamp: May 09, 2019, 09:26:50 am
content: Quote from: paulca on May 09, 2019, 08:56:57 amSo the new battery will be trickle charging the old battery, or is it more complex than that?

author: digsys
author_rank: Unknown
timestamp: May 09, 2019, 09:35:43 am
content: Quote from: e100Unknown, depends on the relative chemical states of the 2 batteries etc etc BUT, there will be some actual loss. Why not wear a 0.4V loss (Shottky diodes),or 0.6V loss (STandard diodes) - putting them on the OP of each battery. The "newer / better" one will do most the work for a while, until the "weaker / older"one catches up. Need more details on what you want to do - how they are wired, as there may be other choices.
Mixing Rosin Activated and No Clean Flux? - Page 1
Forum section: electronics / beginners

author: PotatoBox
author_rank: Regular Contributor
timestamp: August 07, 2021, 09:01:36 pm
content: Hello,I've been used an old roll of Kester 44 solder and it has been working fine, giving nice and shiny joints, but I had just noticed that my flux pen that I use, a No Clean Flux, is different to the Kester 44's Rosin Activated Flux and I have been mixing the two. Is this an issue?I was also given the advice that I should steer clear of Rosin Activated Flux and look for RMA or R type flux, as Rosin Activated is not suitable for stranded wires. Is this true? It's harder to find RMA or R type solder, as it seems that companies like MG Chemicals mostly offers only RA and No Clean solder and flux products.Thanks,

author: tooki
author_rank: Super Contributor
timestamp: August 07, 2021, 11:59:29 pm
content: I’m pretty sure that countless millions of stranded wires have been tinned with Kester 44 solder wire. Maybe it’s not mil-spec, but it’s absolutely fine in normal use.External flux is another matter: unlike the flux core inside solder wire, there’s no guarantee that external flux has reached the temperatures needed to neutralize it. This is at least as critical, if not more so, for no-clean than for rosin fluxes.MG Chemicals carries only a basic selection of solders. A full-service brand like Kester has multiple products within each flux category. So if MG doesn’t have what you need, just look at a brand that does.As for mixing flux types: my own research into the composition of fluxes leads me to believe that no-clean fluxes don’t really use any novel fluxing agents or activators. They just have generally much lower solids contents and little or no rosin/resin contents. What they do use are ingredients also found in rosin fluxes. I strongly suspect that the primary reason behind the “don’t mix flux types” warnings is the fact that it’s an untested, unquantified thing, and thus does not ensure process reproducibility, so their lawyers said to say it so nobody can complain.I would not, however, mix water-soluble fluxes with any other kind.
Mixing Silver & Leaded solder. - Page 1
Forum section: electronics / beginners

author: @rt
author_rank: Super Contributor
timestamp: March 08, 2016, 01:33:28 pm
content: Hi GuysWhen changing caps & such on the board I want to preserve,is it ok to solder with leaded solder on a board that still has residual silver solder?for the purpose of a lower molten temperature if there’s a next time?I’ve done it on protoboard, and the experimental new solder alloy seems to have the characteristics of leaded solderas far as molten temperatures are concerned.Cheers, Art.

author: matseng
author_rank: Frequent Contributor
timestamp: March 08, 2016, 02:22:08 pm
content: I've been using Kester solder for a number of years now with 2% silver, 62% tin and 36% lead. I got this particular roll by mistake and just used in without any special thought.Wikipedia says the following for this particular mix:QuoteSo it seems like it's good for SMD, and as equally bad for gold plated stuffs like the common Sn63Pb37 or Sn60Pb40
MKS 288 IEEE interface (RST39) - Page 1
Forum section: electronics / beginners

author: Crowbar
author_rank: Newbie
timestamp: October 14, 2024, 02:09:49 pm
content: Anyone ever see a manual???If anyone has a copy please advise.Thank you in advance.

author: Bryn
author_rank: Regular Contributor
timestamp: October 14, 2024, 05:30:13 pm
content: Try looking for one on MKS Instruments' website or if in doubt contact them about it...

author: Crowbar
author_rank: Newbie
timestamp: October 30, 2024, 01:47:35 pm
content: No Company left to call.
MLCC caps in series - Page 1
Forum section: electronics / beginners

author: SnakeBite
author_rank: Regular Contributor
timestamp: June 01, 2014, 11:24:49 pm
content: Hi,i saw in Dave's video about capacitor that if you put them in series you need to put balance resistors in parallel to them to avoid different voltage drop on the capacitors due to leakage. in the video he talks about electrolitic capacitor but do i need to do that with MLCC (multi layer ceramic capacitors) as well? bear in mind that the capacitors in my design is not used in high current or high voltage they just audio signal capacitors (filters). i'm putting them in series to get smaller capacitance.thanksIdo

author: Paul Price
author_rank: Super Contributor
timestamp: June 02, 2014, 12:18:15 am
content: no, not necessary to use resistors at all because there are no high voltages to distribute..

author: ok_cool
author_rank: Contributor
timestamp: October 16, 2015, 07:50:12 pm
content: I continue on this.So it is perfectly OK to use 16V ceramic caps in series to get higher than 16V? Looking to get 30V with 22µF ceramics.

author: tautech
author_rank: Super Contributor
timestamp: October 16, 2015, 08:05:17 pm
content: Quote from: ok_cool on October 16, 2015, 07:50:12 pmYes, but for 2 caps the total capacitance is havled:http://farside.ph.utexas.edu/teaching/302l/lectures/node46.html

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 16, 2015, 08:42:10 pm
content: Arguably, it might be more important, because although the leakage is lower (uA?), there isn't a self-balancing effect to it. And if one capacitor eventually ends up overcharged, its capacitance (and therefore the total capacitance) will drop precipitously , as the dielectric saturates. (There's absolutely no danger of breakdown -- a 16V cap might finally arc over beyond 100V.) So you'd still want resistors, but the values can be larger because the expected leakage is smaller.I would much better recommend using good old electrolytic or tantalum for your purpose, or if low ESR is needed, aluminum polymer.Tim

author: ConKbot
author_rank: Super Contributor
timestamp: October 17, 2015, 04:44:41 am
content: Be mindful that with dc bias, or if you're feeding that much signal in that you're needing 2 caps in series that high capacitance ceramic caps (x5r/x7r and related, and even more so y5v and z5u), the capacitance changes with voltage applied. Plus they can be microphonic. For filters and stuff in the signal path, stick with c0g/np0 ceramics or film capacitors.
MLCC meter recommendation ??? - Page 1
Forum section: electronics / beginners

author: Plankton
author_rank: Newbie
timestamp: December 05, 2012, 05:48:59 pm
content: I'm looking for a recommendation on an economic meter for measuring loose MLCC parts.Here are a couple of part numbers I would be measuring.GRM21BR60J226MELLL185R71A104MA01LYour input is appreciated.

author: robrenz
author_rank: Super Contributor
timestamp: December 05, 2012, 06:25:03 pm
content: This mastechseems to be pretty good+inexpensive and you can use tweezers with it. The tweezers can be calibrated out. If the tweezers are like the ones from my DE-5000 you will need to do a little filing of the tips to a smaller size to grab parts that small well. The tweezers also are flexible enough that you have to use a lot of manual finesse to keep the tips aligned on things that small The IET DE-5000 is also good but more expensive but with much higher accuracy specs.

author: Smokey
author_rank: Super Contributor
timestamp: December 05, 2012, 08:24:16 pm
content: Another way to ask this question which would probably get a lot more responses would be:"Looking for a capacitance meter that has probes which would be suitable to grabbing 0805 and 0603 surface mount caps in the range of 0.1uF to 22uF."That said, you can get tweezers probes that fit into standard multimeter probe spots if your meter already has the capacitance range and accuracy you need. The cheapest ones like these for 5 bucks from sparkfun kind of work, but really are pretty flimsy.https://www.sparkfun.com/products/11060You didn't say what accuracy you needed. If you can get away with that, it's a cheap solution. The next step would probably be an LCR meter that comes with decent tweezer probes.

author: Plankton
author_rank: Newbie
timestamp: December 05, 2012, 09:38:56 pm
content: The question is not about the probes. I'm told that to accurately measure MLCC devices I need a meter that has Automatic level Control (ALC) that monitors and adjusts the Vrms. I looked at the spec. sheet for the Mastech meter and it does not appear to have this feature.

author: Plankton
author_rank: Newbie
timestamp: December 05, 2012, 11:32:05 pm
content: I found a really good document that answered many of my questions regarding measuring MLCCs.Looks like I need an HP4284A 20 Hz - 1Mhz LCR Meter or equivalent.Anyone know of something like the HP4284A that can be had for under $5k. Gotta have ALC.Here's the link to the document on accurately measuring MLCC devices.http://www.samsungsem.com/customer/FAQ/Capacitance_Measurement.pdf

author: Smokey
author_rank: Super Contributor
timestamp: December 06, 2012, 12:27:01 am
content: Cool. Thanks for the link. That's really interesting stuff. Sorry, I didn't realize you had a specific feature in mind when you asked your question.That brings up some good points. With all the attention LCR meters have been getting around here recently, maybe someone should make a list of the features the cheaper ones are lacking that could effect measurement accuracy. Something like an LCR meter sticky thread or something.
MMBT vs. PMBT Prefixes for SMD Transistors - Page 1
Forum section: electronics / beginners

author: Farley
author_rank: Regular Contributor
timestamp: September 02, 2014, 08:38:04 pm
content: I notice there are (at least) two flavors of 3904 transistors with the SOT-23 footprint, MMBT3904 and PMBT3904. Comparing the NXP datasheets of each shows that the specifications appear to be the identical.Is there a difference I am missing between MMBT and PMBT versions of this particular transistor? I've read speculation that the first letter (M or P) might refer to the original manufacturer. I've also noted that the single unit price at both Mouser and Digikey is slightly less for the MMBT version.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 02, 2014, 11:18:02 pm
content: P for Philips (NXP).M for Motorola (On Semi), though everyone else makes MMBTs (and MMSD, and so on) too I think, so that one's more genericized I guess.Other examples: MPS, MPSA, MPSH, MMBTH, etc.There was a 2N3563 (something like a smaller, faster 3904), which was a TO-106 case (old 70s round plastic blob package), then the PN3563 (TO-92 -- as most PN's were: see also e.g., 2N2222 is TO-18 metal can, whereas the PN2222A is the TO-92 most people think of), and the Motorola MPS3563. Possibly others I don't know.Or the one popular in avalanche pulse generators: 2N2369 (TO-18), PN2369 (TO-92), PH2369 (Philips/NXP), MPS2369, etc.Tim
MN Taper Poteniometer - Page 1
Forum section: electronics / beginners

author: Jwillis
author_rank: Super Contributor
timestamp: September 14, 2020, 10:23:12 pm
content: I managed to figure out how to wire a Dual MN taper potentiometer for a balance control but I was wondering if anyone here knows of a symbol for this type so I can clarify my circuit diagram without extra notes . If a symbol does not exist how would you create one for an editor . Any suggestions?

author: bob91343
author_rank: Super Contributor
timestamp: September 14, 2020, 10:35:51 pm
content: What is MN?

author: ledtester
author_rank: Super Contributor
timestamp: September 14, 2020, 10:39:44 pm
content: Graphs of different tapers:http://www.alpha-products.com/cd_catalog/new_catalogs/Pots/tapers.htm

author: ledtester
author_rank: Super Contributor
timestamp: September 14, 2020, 11:40:24 pm
content: After much googling my understanding is that a "MN taper potentiometer" is actually two pots which are linked:https://www.bourns.com/docs/ProAudioDocs/bourns_pdb182_blend-balance_guitar_pots_appnote.pdfOne pot has a M-taper and the other has a N-taper. Is that correct?

author: bob91343
author_rank: Super Contributor
timestamp: September 15, 2020, 03:25:10 am
content: Okay then, a typical stereo balance control.I have seen them on diagrams with a resistor halfway and a straight line the other half, and ganged with another with the reverse setup.

author: Jwillis
author_rank: Super Contributor
timestamp: September 15, 2020, 07:38:23 am
content: Quote from: ledtester on September 14, 2020, 11:40:24 pmNot quite . They can be single or dual gang but usually the dual gang is sold . From 0% voltage to 100% voltage only 50% of the pot is turned to the centre indent. After the indent its 100% voltage from 50% to 100% turn of the pot. With a dual pot you configure it so that at the indent both pots pass 100% voltage. When you turn the pot one way one pot decreases the voltage while the other pot remains at 100% voltage through the turn . When you use them in this configuration for balance you get no losses in one channel as the other channel is turned down in volume . The same happens when you turn down the pot the opposite way to lower the volume of the other channel other channel.But I got thinking it would be easiest just to change the identifiers on the legs . Centre would become source and the other legs would become M and N . For a dual MN it could be drawn like below .What do you think?

author: ledtester
author_rank: Super Contributor
timestamp: September 15, 2020, 08:42:49 am
content: Quote from: bob91343 on September 15, 2020, 03:25:10 amI think this method most unambiguously identifies the two terminals.
MOBILE PHONE APPS ON YOUR COMPUTER - Page 1
Forum section: electronics / beginners

author: MrsR
author_rank: Regular Contributor
timestamp: May 13, 2014, 09:10:59 am
content: Hi! Guys,This may be of some help to beginners and experienced alike.The program is calledBLUESTACKSand there are a number of free APPs that make things a little easier when checking or designing circuits, like voltage divider calcs. colour codes number codes for Metalized Ceramic Capacitors, 555 timer circuit passive values even a circuit designer assistant. So try it. I have just used an APP. to help with the calculations on passives while designing a 10 LED Tacho for a single Cylinder bike In LTSPICE IV and saved a couple of hours working out Inverting voltage on 5 Dual LM393 Comparators etc. (I found an easier way using a LM3914 Linear Bar/Dot 10 LED driver)BLUESTACKS is easy to down load and has a short cut for your computers DESK TOP.HAVE FUNRachael

author: electr_peter
author_rank: Unknown
timestamp: May 14, 2014, 06:52:52 pm
content: Thanks for a link MrsR.One may think that there is little value in using smartphone apps on PC, but there are at least 2 major ways it can be very useful:app developers can check their app without smartphonesome programs can be accessed only through smartphone apps (I don't know why, really)
Mobile Stepper Motor Driver Project / Use of membrane buttons - Page 1
Forum section: electronics / beginners

author: Jasonkandefer
author_rank: Newbie
timestamp: April 29, 2024, 02:28:16 pm
content: Hey! New here, I’ve been a lurker for a while and decided to make an account and ask a few questions.About a year and a half ago, I came up with an idea for a tool that I could use at work (commercial HVAC technician) to be able to calibrate and diagnose issues with Electronic Expanion Valves. These “EEVs” use a stepper motor to open or close valves to meter refrigerant. I’ve dabbled with Arduino and breadboards before this, and was finally able to come up with a working prototype that used numerous premade pcbs (boost/buck converters, Arduino nano boards w/ breakout pcb, external battery life indicators etc) obviously having this many separate boards all being manually wired together was not a good option as it was fragile and buck/boost converters were melting if I hooked up to an EEV that drew a tad to much power. I dabbled with having guys on fiver make me some actual PCB prototypes, but after spending 5-700$ on having boards ordered an assembled through JLPCB, I still didn’t have a working prototype, which leads me to the old saying “if you want something done right do it yourself” so I downloaded kicad, started watching youtube videos, and began prototyping simple PCBs until I started getting the hang of it. Well, 7 months after downloading kicad I have a pretty complex PCB using an ATMEGA328P-AU & an A4988 stepper driver IC. The atmega chip produces a contact 330Hz square wave for the a4988, and also controls the button logic for enable/direction & speed controls MS1,2 & 3. The board is powered from a 3S AAA 3.7v battery pack delivering 12.4VDC to the PCB, an ATTINY and a low quiescent linear regulator is used for turning the device on an off, the ATTINY stays in sleep mode until the button connected to one of its pins is pressed and held for 1 Second, it then wakes up, and outputs 5v to the gate pin on a SOT223 2N2222 Transistor that makes contact between battery ground, and the ground plane on the PCB, enabling 12VDC to the rest of the board. Another 1 second press will then shut the board off.My real question here is since I also dabble in Cad, (solidworks & shapr3d) I’ve designed a case for this project, but I want it to be sleek, and durable. So I’d like to implement the use of a custom membrane switch keypad. I’ve looked at some websites and seen I can have them prototyped for around 300 USD. Has anyone had a custom membrane keypad made? I have & can use photoshop to design the button graphics, and can design the schematics for the buttons aswell, would this cut down cost? What is the process of having these keypads made? Any suggestions for an easy to work with company for making these?Thanks.

author: m k
author_rank: Super Contributor
timestamp: May 07, 2024, 10:43:43 am
content: Quote from: Jasonkandefer on April 29, 2024, 02:28:16 pmMore like Projects and Designs stuff.Click report and request moderators a change.
Mobile telephone LCD issue - Page 1
Forum section: electronics / beginners

author: steve30
author_rank: Frequent Contributor
timestamp: February 05, 2013, 07:04:53 pm
content: I just got a nice old Motorola mobile phone off ebay.Unfortunately, the LCD display is a bit dodgy.See the attached pics to see the issue. Does anyone know, is it likely a problem with the LCD, its cable, or the driver board? Sometimes squeezing it a bit makes a few pixels come on and a few others go off, but I've not got all of them to work yet.Thankssteve30.

author: PA0PBZ
author_rank: Super Contributor
timestamp: February 05, 2013, 07:18:33 pm
content: I think it's the cable, it looks like the self-adhesive (or glued on) one. Had the same problem with a display some time ago, and AFAIK there's not much you can do about it apart from pressing the contacts down and hope for the best.

author: Bored@Work
author_rank: Super Contributor
timestamp: February 05, 2013, 07:43:42 pm
content: Depending on make, model and age you sometimes get spare displays for older phones rather cheap. Try to google an LCD display for your make and model.

author: marshallh
author_rank: Unknown
timestamp: February 05, 2013, 08:38:19 pm
content: Try using a rework station or localized heat on the wide flat adhesive ribbon... after you've removed it from the rest of the phone!Judging by the small connector it probably has a COG controller with spi or i2c host interface.

author: steve30
author_rank: Frequent Contributor
timestamp: February 06, 2013, 06:15:38 pm
content: I reckon its the cable.Would heat likely do anything? Doesn't look like they are soldered.

author: steve30
author_rank: Frequent Contributor
timestamp: February 06, 2013, 09:09:45 pm
content: Well, I attacked it with my soldering iron, and the display is much better now. Just one line is missing. Probably because I damaged a trace on the cable.
MOC 3023M - Page 1
Forum section: electronics / beginners

author: ASHU
author_rank: Contributor
timestamp: July 11, 2015, 04:13:10 pm
content: I am new to electronics.Just wanted to know if I can directly provide 240Vac to the anode of MOC-3023M or should I use a resistor in between?also will a zero crossing IC like MOC-3042M work on the same voltage?I have read the datasheets but I don't understand every part of it, still learning.Thanks in advanceLink to datasheet-MOC-3023M :http://www.farnell.com/datasheets/1806097.pdfMOC-3042M :http://www.farnell.com/datasheets/1639837.pdf

author: Roeland_R
author_rank: Regular Contributor
timestamp: July 11, 2015, 08:26:47 pm
content: Max voltage between anode and cathode is 1.5 Volts. Don't use higher voltage. It is an LED on the primary side!

author: Hideki
author_rank: Frequent Contributor
timestamp: July 11, 2015, 09:31:47 pm
content: It is meant to be used in "reverse" compared to what you want: To use a microcontroller to control 120/240VAC, and absolutely NOT to use 120/240VAC to control a microcontroller.

author: ASHU
author_rank: Contributor
timestamp: July 12, 2015, 05:51:08 am
content: Ooooo like thatThanksAny idea What can i use for my purpose?

author: Hideki
author_rank: Frequent Contributor
timestamp: July 12, 2015, 06:35:12 pm
content: Are you not happy with any of the suggestions you already received in your other threads?

author: ASHU
author_rank: Contributor
timestamp: July 12, 2015, 07:50:36 pm
content: No i wasBut it's too difficult to find ic like that where I live and online ordering was getting expensiveSo I started looking for some cheap alternative
MOC-7811 IR Opto-Isolated Slot Sensor MTBF, Sensitivity of signal due to bending - Page 1
Forum section: electronics / beginners

author: kfc_n
author_rank: Contributor
timestamp: June 18, 2015, 03:16:23 am
content: Good day,I need help on these details regarding MOC-7811 IR OPTO ISOLATED SLOT SENSOR:1.) MTBF in terms of hours used?2.) Sensitivity of sensor when it comes to bending of receiver and transmitter pole, tolerance in distance? thanks3.) Does anyone here has a copy of product catalog of MOC-7811 IR Opto Isolated Slot Sensor?Thanks and more power!
MOC3041 BTA26 strange behavior - Page 1
Forum section: electronics / beginners

author: gj.gj
author_rank: Newbie
timestamp: June 02, 2018, 12:01:19 pm
content: Hi,I am trying to build a fairly simple circuit but it is behaving in a very strange way.fig2.png is the schematic.When I connect R10 the triac conducts immediately despite the optocoupler state.Without R10 the triac does not conduct but the opto is not able to drive it even though the pin 1 and pin 2 are controlled correctly with 10-20mA through the diode.Any help to troubleshoot is welcome.

author: wraper
author_rank: Unknown
timestamp: June 02, 2018, 12:04:38 pm
content: QuoteYou connected the triac a wrong way around. Swap A1 and A2 pins.

author: matseng
author_rank: Frequent Contributor
timestamp: June 02, 2018, 02:57:14 pm
content: Quote from: wraper on June 02, 2018, 12:04:38 pmWould that really matter for a four-quadrant triac?

author: wraper
author_rank: Unknown
timestamp: June 02, 2018, 03:05:20 pm
content: Quote from: matseng on June 02, 2018, 02:57:14 pmIt matters for any triac. You cannot just switch the terminals around. Voltage on gate should always be applied in reference to A1(MT1) pin.

author: matseng
author_rank: Frequent Contributor
timestamp: June 02, 2018, 03:18:32 pm
content: Hmmm... Yes that seems reasonable. It was 35+ years since I read up about the workings of triacs so I forgot most of it - [ Teh old people are stupids ;-) ]. But it's slowly coming back to me now. Thanks.

author: gj.gj
author_rank: Newbie
timestamp: June 02, 2018, 05:33:33 pm
content: Quote from: wraper on June 02, 2018, 12:04:38 pmThat was it.Thanks
Modding an auto on/off LED night light - Page 1
Forum section: electronics / beginners

author: EvilGeniusSkis
author_rank: Regular Contributor
timestamp: July 20, 2015, 08:57:38 pm
content: I have some LED night lights that turn off during the day by way of an LDR and some other bits. I've got some projects I would like to use the night lights to turn on and off, but I am wondering if it would be safe. i measured the voltage between the led and live and came up with 2Vac. Seeing as the projects I want to use these in are just led based I was thinking of just connecting them in place of the stock leds. the other possibility i have come up with is using something else to power the project and using an optoisolator with the night light to switch the project.Pics:I've never seen this type of label for a UL listed product before

author: Zero999
author_rank: Super Contributor
timestamp: July 20, 2015, 10:14:11 pm
content: It's certainly a capacitive power supply which will not be isolated. The whole circuit should be treated as though it's mains.Yes, you probably could replace the LDR with an optocoupler.Have you tried reverse engineering the schematic?

author: edavid
author_rank: Super Contributor
timestamp: July 20, 2015, 10:21:56 pm
content: Quote from: Hero999 on July 20, 2015, 10:14:11 pmI don't see how that would work - what would be the light sensor?Instead, he would need to put the optocoupler's LED in place of, or in series with, the original LED.But, it's probably just as easy to use an LDR to control the new project.

author: Zero999
author_rank: Super Contributor
timestamp: July 20, 2015, 10:38:28 pm
content: Quote from: edavid on July 20, 2015, 10:21:56 pmI thought he wanted to replace the light sensor with a signal from another circuit.
Modding E3620A - Page 1
Forum section: electronics / beginners

author: 3141592
author_rank: Regular Contributor
timestamp: June 19, 2014, 02:43:03 pm
content: Hello everyone,I'm thinking of making the current limiting (which is supposed to be set at a constant 1.05A) on my E3620A PSU adjustable, by swapping the current limit calibration trimpots for some multiturn ones, or something along these lines. Now I have already posed this question to others, and they said that this might cause trouble with the current limiter's frequency compensation resulting in overshoot and oscillation along with possibly making the switch to CC mode slower. So I've put the project on hold. My question is whether if this is true? If this is true, what is the purpose of the frequency compensation in a current limiting circuit and what does it do exactly?I was thinking of measuring the step response with the current set to a low value to test this, but I have no digital scope at hand to do this.I hope I've posted this in the right section, thanks for any input.
Modding Netgear Switch for 5V - Page 1
Forum section: electronics / beginners

author: Driver
author_rank: Unknown
timestamp: June 20, 2016, 12:10:29 pm
content: Hello,I have an old Netgear switch that I need to embed in to a project and as such would like to power it from 5V DC. Unfortunately the Netgear is spec'd for a 7.5V supply and it won't operate when only fed 5VDC.It has aAP34063dc-dc chip, which had 3.3V on Pin 2 when fed by the original supply. So after disconnecting the original supply, I got my own LM2596 regulator board and fed 3.3V to this pin - which in turn makes unit work off my 5V supply.Questions:1. Is this mod correct? Whilst it appears to be working fine, should I bother to disconnect/isolate the original dc converter chip? I noticed I then had ~2V on the original 7.5v input connection2. Or does anyone have a better idea to mod the onboard regulator's input spec?
Modding Registered/Buffered DIMM Memory Possible? - Page 1
Forum section: electronics / beginners

author: sean0118
author_rank: Frequent Contributor
timestamp: May 12, 2015, 12:29:41 pm
content: I'm guessing this is a long shot, but is there a way to disable the register on registered/buffered computer DIMM memory?I've found a datasheet for the type of register I meanhere. I can't see any glaring DISABLE function...If there is a solution I'm guessing it's near impossible due to the use of SMD BGA packages? Thoughts?
Model rocket launcher? - Page 1
Forum section: electronics / beginners

author: Jeff eelcr
author_rank: Frequent Contributor
timestamp: July 30, 2022, 12:22:31 am
content: Someone has just asked me to help them build one from predesigned planswith a few modifications they would like.Nothing major however the first thing I noticed was the input +12V has azener diode 8.2V first then a 1K resistor then a green LED to ground doesanyone know why this zener would be put in series like this to ground?Circuit power is taken directly off the input before the zener.Jeff

author: pqass
author_rank: Super Contributor
timestamp: July 30, 2022, 01:28:15 am
content: To limit the current to the LED by cutting 8.2V off the top?I'm not sure why it would be necessary; 2.2mA vs. 10.2mA (without zener). Too bright maybe?But then the 1K resistor could just be replaced with a 4.7K to achieve the same result.http://www.falstad.com/circuit/circuitjs.html?ctz=CQAgjCAMB0l3BWcMBMcUHYMGZIA4UA2ATmIxAUgoqoQFMBaMMAKGwBYQAvOgOzoBODPNBThw0DGHbYEKPGGLyw8FI3JUUseDt35OIsay4hZYlCk5nwhTdz6DholgCVTc8GDHW8VPyHYqLygQmAQWAXdzSyiQeTwQlTgWMEJvD3jY7GxCOJAAEzoAMwBDAFcAGwAXBgq6fMTQ2FYAcyycrI8-Ngwqa2Z0o1txboAHANSbKnZJi04IMYncuaW4vASFqBZxmeX11ezczcgWAHcDjutDrfPdtYTrTJPb2ZjHmOfV1L6Pb5uKDBHYYIYJ-T4IQH3CjBJ5nAG5a4g7wdE7jCF7BLo0wdY7beFTfGZXHYXrQozBJEE3FtSmI4LWbqpMSUzK0jpiQqlSo1OoNIJNSCsSKUv4s-ZBeCuMmeZnBXyhAJBMT+MJ4lAIZYxdUInGhOHa7EIjzXT4GlbvTgnIA

author: Jeff eelcr
author_rank: Frequent Contributor
timestamp: July 30, 2022, 03:48:00 am
content: Thats all it does and it makes no sense doing it.The 3 other LEDs use only a 1K and are around the same forward voltage.I think they were tring to have overvoltage protection but as this should passup to 50A they did not know how to add it.I also wondered if it was some type of protection in test mode but it has no effectthere either.Jeff

author: Ian.M
author_rank: Super Contributor
timestamp: July 30, 2022, 05:33:43 am
content: It would prevent the green LED lighting below about 10V Vin, so may serve as a low battery indicator. Attempting to launch with too low a battery voltage could result in a potentially dangerous hang-fire.

author: Gyro
author_rank: Super Contributor
timestamp: July 30, 2022, 10:16:11 am
content: Yes, it's a low battery indicator.

author: Jeff eelcr
author_rank: Frequent Contributor
timestamp: July 30, 2022, 12:11:04 pm
content: Thank you.Now it makes sense and very simple.Jeff
Modeling Converter Load Changes - Page 1
Forum section: electronics / beginners

author: sean0118
author_rank: Frequent Contributor
timestamp: May 30, 2014, 02:23:42 pm
content: Hi everyone,I have a pretty basic question for you. At the moment I'm simulating an LLC resonant converter of my own design. It all seems to be working fairly well... except changes in load.I just want to see how it reacts if the load is changed form say 100% to 50%. However, at the moment I just switch one off and the other on. Which of course means the load changes instantaneously causing a large voltage spike.What's a better way to model a load change? Some sort of transition period where it ramps down from 100% to 50%? How fast are load changes expected to happen in real life?
Modeling Depletion Mode MOSFETS using LTspice? - Page 1
Forum section: electronics / beginners

author: sean0118
author_rank: Frequent Contributor
timestamp: November 16, 2015, 12:44:06 pm
content: Hi everyone,I have made component models in LTspice before, but this one has me stuck. What parameter in the model makes it operate as a depletion mode MOSFET? (as in, not enhanced mode)I have seen it suggested online that a negative values for Vth is what's needed (for an NPN), but this doesn't make any sense to me. There should be no threshold voltage, NPN depletion mode MOSFETs conduct with the base at 0V...Any ideas?

author: c4757p
author_rank: Super Contributor
timestamp: November 16, 2015, 01:07:25 pm
content: No, that's still accurate. They still have a threshold voltage - N-channel depletion MOSFETs do indeed conduct with the gate at 0V, but stop conducting at a certain negative voltage. That's the threshold voltage. If you look at the ID(VGS) curve of a depletion-mode MOSFET, it's just shifted to the left from that of an enhancement-mode MOSFET.

author: sean0118
author_rank: Frequent Contributor
timestamp: November 16, 2015, 01:22:34 pm
content: Quote from: c4757p on November 16, 2015, 01:07:25 pmAh, of course! Thanks I was somehow thinking of it all backwards, makes sense now. (I was thinking for a Vth of -3V in LTspice it would conduct even more at -4V, not the case obviously)

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: November 16, 2015, 01:24:54 pm
content: To the OP,What kind of circuit are you modelling? switching behaviour or small-signal?Can you provide the part number of the part that you want to model?Regards,Jay_Diddy_B
Modeling electric current - Page 1
Forum section: electronics / beginners

author: spacedementia87
author_rank: Contributor
timestamp: August 23, 2016, 11:46:43 am
content: Aimed at school teachers to help explain electric current, but some light find this usefulhttp://www.talkphysics.org/articles/webinar-modelling-electric-current/Sent from my ONE A2003 using Tapatalk

author: edy
author_rank: Super Contributor
timestamp: August 23, 2016, 09:15:32 pm
content: Interesting model... you can do the same with a peg-board. However, it seems like a lot of work for a model that doesn't explain very much or let you provide many useful analogies. Sure, the marbles are "resisted" in their flow down-hill ("across a voltage difference") by the pegs ("atoms").But I'd like a model which shows flow through a circuit, performs some work (like spinning a wheel), and returns the marbles back to their starting point (can use a hand-cranked lift to demonstrate a battery). The "potential" energy here or voltage/EMF would then be likened to the gravity that is making the marbles roll down-hill. Sure you can put them through some resistive elements like a peg-board, but no marble model will really truly reflect what is going on. Even water/pipes analogies are good up to a point, but they are messier to create models of for a class and have kids play with it. So I like the marbles idea... just needs a bit more to it.
Modern LCD control - Page 1
Forum section: electronics / beginners

author: Poe
author_rank: Frequent Contributor
timestamp: October 13, 2015, 02:29:17 am
content: I'm trying to learn more about modern LCD monitors and how they're controlled. Eventually I'll tear one down and poke around for wave forms and such. If anyone could point out my mistakes or link to a source, or a teardown someone else has already done... that would be wonderful.I think I understand up to the LVDS. After that point in the control chain, I'm lost.Originally I thought the driver IC controlled grey-scale for each unit/sub pixel via PWM.i.e. ON = Light, OFF = No LightThis is apparently incorrect.Now from what I gather, each pixel's plate charge is adjusted, which in-turn 'twists' the light more or less, which in-turn increases or decreases the amount of light going through the polarizer... right?Each LCD driver IC adjusts each pixel charge to ~8 bits of accuracy via it's OWN DAC?! That's a lot of DACs.Although from what I gather, each DAC is only 4bits and is simply like a fine adjustment? The most significant 4bits select a rough voltage level from ~16 preselected (resistor set) voltage levels. This rough adjustment is largely responsible for gamma correction? The 4bit DAC simply adds a small voltage offset?How far off am I? If that's how they adjust gamma, then how is it changed in software?I read that most modern TN panels are only 6 bits versus the 'true 8bit' IPS panels. Is this simply because TNs are faster and they can get away with more dithering? Is it simply a limitation of the LCD driver circuitry and a TN panel could have eight bits of greyscale?

author: amyk
author_rank: Super Contributor
timestamp: October 13, 2015, 04:12:09 am
content: Yes, there are many DACs in parallel in the source drivers.Give these documents a good read...http://web.nchu.edu.tw/pweb/users/fansen_wang/lesson/7043.pdfhttp://www.ti.com/litv/sgls099http://lcd-module.de/eng/pdf/zubehoer/hx8218a.pdfhttp://ee.cust.edu.tw/ee/91-93%E5%90%84%E9%A1%9E%E8%AC%9B%E5%BA%A7%E8%B3%87%E6%96%99/051117%E7%A0%94%E8%A8%8E%E6%9C%83/%E8%98%87%E7%B4%94%E8%B3%A2/LCD%20Source%20Driver%20Design.pdfhttp://www.ti.com/lit/pdf/sgls116http://www.microtipsusa.com/pdf/HX8643A.pdf

author: Poe
author_rank: Frequent Contributor
timestamp: October 13, 2015, 12:55:13 pm
content: Thanks. I'll give them a read.It's amazingly more complex than I would have thought.P.S. Do you happen to have any info on large format RGB LED displays (like jumbotrons) or OLED displays as well? Thanks again.

author: amyk
author_rank: Super Contributor
timestamp: October 15, 2015, 02:45:24 am
content: For OLEDs you can look at driver IC datasheets (like this one). Mike has some good videos on large multiplexed LED displays:
Modified sine wave inverter questions - Page 1
Forum section: electronics / beginners

author: TheAmmoniacal
author_rank: Unknown
timestamp: April 27, 2014, 09:00:55 am
content: Just a couple of quick questions, would it be a good idea to use a power inverter (12VDC-230VAC) for mains experiments on the desk? (And testing transformers)I see many (if not most?) outputs a modified sine wave, could this be destructive to some electrical appliances or equipment made for a pure sine? What would be some devices made for 100-240 VAC that could not be used with a modified sine wave?Also, would such a sine be correctly transformed again, rectified and regulated?Thanks!

author: Halfdead
author_rank: Contributor
timestamp: April 27, 2014, 09:31:51 am
content: Some PFC devices don't get along with modified sine wave power supplies.

author: Rerouter
author_rank: Super Contributor
timestamp: April 27, 2014, 11:16:37 am
content: a number of power tools get upset by them, more so in how they sound while running, equally no matter what phone charger i use on one i cannot use the touch screen of my phone (likely due to noise injection)some devices that use transformers can also get a little warmer as its passing DC current more than it is AC,
Modified switch-mode PSU question - Page 1
Forum section: electronics / beginners

author: dr_p
author_rank: Frequent Contributor
timestamp: November 20, 2012, 01:17:55 pm
content: I've modded a fixed 19V, 3A power brick to give variable output. It has no over-voltage protection, just a TL431 and optocoupled feedback. I also replaced the caps with 63V rated ones.Question is how much voltage can I safely set it to? It goes to at least 50-60V if I turn the pot all the way up. I'm figuring I'm all fine provided I keep it below the max power is was designed for. I intend to increase the current sense resistor in order to lower the (fixed) current limit. For instance, if I double the voltage to 38V, I'll also lower the current limit from 3A to 1.5A.I don't have a scope, but I think ripple will go up as well.Will this work?

author: dr_p
author_rank: Frequent Contributor
timestamp: November 20, 2012, 02:23:13 pm
content: Good point about the optocoupler's current. I will recalculate the resistor.Yes, I also noticed the cheap nature of the PSU - current sense resistors are half the required power, input filtering was missing on the PCB, caps are low quality, HV separation is very good except for a trace crossing all the way to the secondary for the Y cap.then it gets to 1mm. But it's better quality than most chinese POS.So maybe the saturation is the reason why it will not go lower than 5V, even if it should decrease to 2.5 (the TL431's internal reference). And it's not stable there, I have to raise it a bit to achieve regulation. Is there any way to measure that the core is saturated?
Modify a retro (old ghetto blaster) with Bluetooth  - Page 1
Forum section: electronics / beginners

author: Johadart
author_rank: Newbie
timestamp: June 29, 2024, 10:21:58 am
content: Hi, I’m trying to find how I can add Bluetooth to an old ghetto blaster, all still works fine, even the twin tape decks, but as we all know, cassettes aren’t made nowadays, any help using 240v would be appreciated, thankyou in advance..

author: retiredfeline
author_rank: Frequent Contributor
timestamp: June 29, 2024, 10:58:21 am
content: You can buy bluetooth receiver modules from Aliexpress for not much that accept a BT connection and put out line level output. All you need to do is find a way to power the module and feed the audio to the amplifier in the ghetto blaster.Here's an example of one:https://www.aliexpress.com/item/1005003780419402.htmlYou can use a regulator IC to get 5V if the ghetto blaster electronics uses a higher voltage. Hopefully it will be negative ground. The output can go to the switch that selects the audio source, replacing the cassette deck input. I wouldn't worry about controlling power to the module, its current consumption will be negligible.

author: RoGeorge
author_rank: Super Contributor
timestamp: June 29, 2024, 11:38:47 am
content: Does it has to be Bluetooth? Sometimes I do this:The World's Simplest Hack: iPod Party AmplifierRoGeorgeRoGeorge

author: Andy Chee
author_rank: Super Contributor
timestamp: June 29, 2024, 03:13:15 pm
content: Quote from: Johadart on June 29, 2024, 10:21:58 amThere are several ways to skin a cat....Start with a schematic, without it you will have to rely on your analytical skills in order to find the tape audio signal into the source selector switch. This is where you will disconnect the tape audio and connect your Bluetooth audio.You'll also need to find a suitable voltage source for your Bluetooth module. The source selector switch sometimes switches power on & off to the tape head amp and motors, but it may also be the tape deck buttons (play, rec, rewind, ffwd).HOWEVERBy far the easiest solution might be to use a Bluetooth car cassette adaptor.

author: pienari
author_rank: Regular Contributor
timestamp: June 30, 2024, 09:38:59 am
content: I have used bt module like this.Bluetooth 5.0 Board Module 3.7-5V XY-BT-Minihttps://a.aliexpress.com/_EQcCrfV

author: BeBuLamar
author_rank: Super Contributor
timestamp: June 30, 2024, 10:30:13 am
content: If you want bluetooth then of course there are small bluetooth receiver that you can use. You can use the cassette adapter like others have said but you can use an FM transmtter connect to your source device and use the FM radio of the ghetto blaster to receive.

author: geggi1
author_rank: Frequent Contributor
timestamp: June 30, 2024, 12:31:27 pm
content: Check if it got a line in of some kind. Then you can either hack in to the circuit or use a external battery powered bluetooth sound card.Another option is to get one of these microwatt FM transmitters and use the reciever.
Modify AC/DC supply from 6.5Vout to 6Vout - Page 1
Forum section: electronics / beginners

author: gkmaia
author_rank: Frequent Contributor
timestamp: January 19, 2019, 05:11:21 am
content: I am trying to understand the following circuit but really stuck on how the NCP1203 controller works here.so that is an existing power adapter I have at home and I traced the PCB to understand better the circuit.Seems the NCP1203 works as an oscillator so current can flow through the transformer.But I cannot see anywhere a voltage regulator here.Also what seems to be the feedback coil in the transformer has pin1 not connected to anything.Is there a way to use NCP1203 to regulate the output voltage or it's purely based on whatever comes out of the transformer?Also, will the addition of a pF cap in parallel to EC3 will make the output more stable?

author: wraper
author_rank: Unknown
timestamp: January 19, 2019, 05:29:19 am
content: All you need to do is use zener with lower breakdown voltage. Basically it acts as voltage reference. Once output voltage increases current through it and optocoupler emitter increases. On the other side of optocoupler, controller IC reduces duty cycle in response to that. To reduce output voltage by 0.5V, you need zener with 0.5V lower breakdown voltage.

author: wraper
author_rank: Unknown
timestamp: January 19, 2019, 05:32:54 am
content: BTW on input voltage side circuit has very serious errors. But I won't comment on that further as I'm going to sleep.

author: gkmaia
author_rank: Frequent Contributor
timestamp: January 19, 2019, 05:38:19 am
content: Quote from: wraper on January 19, 2019, 05:32:54 amThat is just copy and paste from the existing power adapter's pcb. I did not come up with this design i am just reverse engineering it. but thanks for the feedback!

author: Zero999
author_rank: Super Contributor
timestamp: January 19, 2019, 11:03:16 pm
content: I think you made a few errors tracing the PCB.The GND pin isn't connected and VCC doesn't look right. The circuit is probably similar to the one on the data sheet, which can be found using a search engine:https://www.onsemi.com/pub/Collateral/NCP1203-D.PDFTake another look at the PCB and compare it to the data sheet schematic. There will be a few differences but it should be similar.wraper is right, the zener diode is used for feedback and the voltage can be changed by replacing it with one with a different breakdown voltage. What are you powering with this PSU? It's likely 6.5V vs ^V won't make any difference.
Modify Daves Soft latch power switch to require longer buttonpressing. - Page 1
Forum section: electronics / beginners

author: ulfpe
author_rank: Newbie
timestamp: April 19, 2016, 12:47:36 pm
content: Hello, I need a soft latch power switch, I found Daves excellentcircuit.I need to modify it a bit, I would like the button to be pressed about 3 seconds before the mosfet turn on and pressing about 2 seconds will shut it down.How do I modify it to have this functionality?

author: veryevil
author_rank: Unknown
timestamp: April 19, 2016, 04:33:42 pm
content: My first guess would be adding a large value cap to the base of the NPN transistor which the 100k Pull up on the other side of the switch will charge?EDIT: Seems to work - See Spice Attached. Added 10u Cap and modded 100k to 1Meg

author: ulfpe
author_rank: Newbie
timestamp: April 28, 2016, 11:19:09 am
content: Thanks!