hybridfree/eevblog-posts huggingface dataset:
variac wiring  - Page 1
Forum section: electronics / beginners

author: panzerfaust
author_rank: Newbie
timestamp: October 19, 2021, 08:56:41 pm
content: Has anyone connected their single phase variac input to 2 phase i.e between L1-L2 ?

author: Benta
author_rank: Super Contributor
timestamp: October 19, 2021, 09:13:11 pm
content: As you're in Sweden, I presume you have 3-phase 400 V mains. This means 3 phases wtih 230 V each to neutral.Unless your variac is rated at 400 V, connecting it to L1/L2 is a really bad idea.And not just because of the voltage, but also the complete lack of of a neutral voltage. Variacs are not isolated from the mains.Don't do it and stay alive.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: October 20, 2021, 03:31:27 am
content: Transformers have a pretty strict voltage limit.If you put too much voltage over it, the core goes into saturation, with the result that inductance drops a lot and it will start drawing too much current.Transformers are also frequency dependent.Simplistic view is that the amount of energy that can be transferred between 2 zero-crossings is constant, which means that at lower frequencies (50Hz) a transformer can handle less voltage then at higher frquencies (60Hz).

author: Vovk_Z
author_rank: Super Contributor
timestamp: October 20, 2021, 05:15:52 pm
content: Quote from: panzerfaust on October 19, 2021, 08:56:41 pmUntil it is not rated for that voltage it will burn.

author: TimFox
author_rank: Super Contributor
timestamp: October 20, 2021, 06:02:37 pm
content: Quote from: Doctorandus_P on October 20, 2021, 03:31:27 amThese points are very important. Since the core has a finite area and a saturation flux density (B-field), there is a maximum flux in the core before saturation. The voltage across the windings is the rate of change (time derivative) of the flux linking the windings (turns times core flux). The time rate of change depends directly on that flux and the frequency. Any voltage across the windings above that saturation limit essentially goes into air, and the current through the copper becomes excessive.
Varicap diode #question - Page 1
Forum section: electronics / beginners

author: M0BSW
author_rank: Frequent Contributor
timestamp: March 23, 2014, 12:18:02 pm
content: I have a circuit which states varicap diode its code is 1n4004, I looked it up and it says silicon regulator diode, well that 's not a varicap diode is it.

author: electronics man
author_rank: Frequent Contributor
timestamp: March 23, 2014, 12:36:09 pm
content: do you have a schematic?

author: SeanB
author_rank: Super Contributor
timestamp: March 23, 2014, 12:39:12 pm
content: It can be used as a varicap diode, as a varicap diode is a regular diode that is specced to have the quoted values of reverse bias capacitance on the junction. A typical signal diode has low capacitance, 3-4pF, and a power diode has higher.Typically 8-15pF at 4v according to this datasheet.http://www.diodes.com/datasheets/ds28002.pdfIf you want higher use a larger power diode, but YMMV. Leakage current as well will be a lot higher. Up to 50uA while a varicap can be a lot lower.

author: edpalmer42
author_rank: Super Contributor
timestamp: March 23, 2014, 05:10:29 pm
content: Check out these pages for info on using regular diodes as varactor (varicap) diodes:http://www.hanssummers.com/varicap/varicaporig.htmlhttp://www.hanssummers.com/varicap/varicapled.htmlEd

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 23, 2014, 11:00:02 pm
content: Beware that 1. no one publishes data on the Q factor of junction capacitance, because they don't need to, and 2. probably because they don't want to anyway. Schottky diodes, for instance, are oft quoted as saving reverse recovery losses; but the capacitance is so large (and probably lossy -- I wish I had numbers), they can actually perform worse in some circuits.Tim

author: Unknown
author_rank: Unknown
timestamp: March 24, 2014, 01:05:47 am
content: Quote from: T3sl4co1l on March 23, 2014, 11:00:02 pmAbout 10~15 years ago I compared the Q factor as varicaps on various power diodes I had lying around. I don't remember the exact diodes I used (certainly 1N400x, as well as others including some weird unmarked ones from my telco days & various stud rectifiers), and I definitely don't remember the exact numbers, but they were surprisingly comparable to typical low capacitance / low CRvaricaps. Even more surprisingly, devices of the same type were fairly consistent across batches & manufacturers. I wouldn't use them for front-end tuning, but they were certainly good enough for tuned oscillators and filters at a pinch.
Varifocal lens mount - Page 1
Forum section: electronics / beginners

author: mr_byte31
author_rank: Regular Contributor
timestamp: June 27, 2024, 10:26:19 am
content: Hi Folks,I am trying to make a small project using two lenses as shown in figure below.I have fixed lens and another movable lens which will go forward and backwards. its movement shall adjust how large is the laser beam on the wall.it was a nightmare to align the lenses and maintain a certain distance between them.I have two questions,1- how can I maintain an accurate measurements between both lenses ex. 2mm ?2- how to align the center of both lenses ?is there special tools for that?I was thinking about building a 3-D module for that but doesn't have any design in my mind that would make life easier...

author: jfiresto
author_rank: Frequent Contributor
timestamp: June 27, 2024, 10:38:49 am
content: You might be looking for an optical bench(Optische Bank).

author: Phil1977
author_rank: Frequent Contributor
timestamp: June 27, 2024, 10:40:40 am
content: I assume you are looking for a "kinematic mount". If it´s for private purposes, I´d search on ebay. Else Thorlabs or the other optical stuff suppliers are your friend.

author: mr_byte31
author_rank: Regular Contributor
timestamp: July 01, 2024, 09:31:22 am
content: Many thanks all for the comments.optical bench is a very good solution for experimentation. I didn't know about it. Thxkinematic mount is my way forward but it is very expensive. I found other options on thispagewhich include many options for lenses mounts.I am not sure why all optical stuff are expensive and not easy to find.But your answers definitely helped me.

author: jfiresto
author_rank: Frequent Contributor
timestamp: July 01, 2024, 12:44:20 pm
content: Quote from: mr_byte31 on July 01, 2024, 09:31:22 amYou might investigate a less accurate xyz stage(Lineartisch). On ebay.de, I am finding some in the EU, probably Chinese-made, for 110~120 euros.
VDO-2072A - Page 1
Forum section: electronics / beginners

author: hhanoem
author_rank: Newbie
timestamp: February 19, 2014, 09:40:08 pm
content: Does someone have the schematics for the VDO-2072A

author: electronics man
author_rank: Frequent Contributor
timestamp: February 19, 2014, 09:43:39 pm
content: Why have you made a poll with the same 2 questions?

author: c4757p
author_rank: Super Contributor
timestamp: February 19, 2014, 09:47:21 pm
content: Wait! I picked the wrong one! How do I change my vote???

author: hhanoem
author_rank: Newbie
timestamp: February 19, 2014, 10:06:10 pm
content: sorry, new here. i did not know how it works yet.
Vehicle Back-up Sensors - Page 1
Forum section: electronics / beginners

author: Falcon69
author_rank: Super Contributor
timestamp: January 16, 2018, 04:27:20 am
content: Hi Guys.For the last few months I have been working on a design for some new bumpers for my truck.But, I've run into a problem.The factory rear back-up sensors are not going to work. Does anyone here know anything about them? Are they all pretty much the same?What I need is some that mount flat and flush, unlike the factory ones that mount into a plastic piece, and are angle to fit the factory bumpers. There are plenty on eBay, but I don't want to purchase until I know if they fit or not.Here's a pic of the rear bumper design. The truck is a 2007 Ford F250 Super Duty Diesel. I know this isn't an automotive forum, but this is electronic related.Thanks in advance if you can answer this. Post some links of ones on eBay you think may work just fine. Thanks!

author: mc
author_rank: Regular Contributor
timestamp: January 16, 2018, 11:49:31 am
content: They all typically work on the same principle, but I've got no idea on interchangeability, and it's not the kind of information that's likely to be publically available.Unless you're willing to experiment, butchering the existing ones to fit the new bumper would probably be the most reliable option.

author: Falcon69
author_rank: Super Contributor
timestamp: January 18, 2018, 12:56:46 am
content: I'll try ordering one, with a flush mount retainer, and see if it can operate on my truck. If not, I guess I'll have to try and see if I can modify my factory retainer clips for the sensors to make them flush mount.
Vehicle Dual Battery Charger for AGM 2nd Battery - Page 1
Forum section: electronics / beginners

author: birdie
author_rank: Contributor
timestamp: August 29, 2014, 04:07:51 am
content: I have recently purchased a PowerSonic 120AH AGM PDC-121200 battery to use as my 2nd battery in my vehicle and campsite power when we get to camp (for running my fridge and lights).My question is about charging the battery in the vehicle (2008 MY09 Mitsubishi Pajero). I have had so much conflicting advice as to what is required for the dual battery charging system.Some people are telling me I must go with a DC-DC charger like a CTEK D250S or Redarc BCDC1220 as they are designed for batteries like AGM batteries with features like bulk, float, etc. So they charge the AGM battery to 100% and then float to ensure maximum cycles...Other people are saying it would be fine just to use a Voltage Sensitive Relay like a Redarc SBI12 which will allow much more current so charge quicker. The same people say the battery will float itself because of the chemistry in the battery. They also say that the DC-DC chargers are not needed for the older/regular style alternators with a fixed voltage (which my vehicle has) (instead the new ECU/temp controller alternators), and that the "hype" about needing a DC-DC charger for an AGM battery is just advertising hype...I'm so confused as to what is needed to ensure my AGM battery is charged fully and has the best life.Can you please advise me which way to go?

author: David Hess
author_rank: Super Contributor
timestamp: August 29, 2014, 04:55:35 am
content: AGM and gelled electrolyte batteries have different charge characteristics than flooded cell batteries. To get the best life out of them, I would use a dedicated charger rather than relying on the vehicles charging system.

author: birdie
author_rank: Contributor
timestamp: August 29, 2014, 05:23:00 am
content: Quote from: David Hess on August 29, 2014, 04:55:35 amSo a DC-DC charger rather than a VSR which basically connects the 2nd battery in parallel with the main starting battery only isolating the 2nd battery when the vehicle is turned off (to prevent accessories on the 2nd battery from draining the starting battery).

author: David Hess
author_rank: Super Contributor
timestamp: August 29, 2014, 02:36:52 pm
content: Quote from: birdie on August 29, 2014, 05:23:00 amYes. Some charging systems intended for flooded cell batteries will shorten the life of an AGM battery considerably.Automotive charging systems for flooded lead acid often have a fixed float voltage setting of 14.40V (2.40V/cell), and a direct replacement with a sealed unit could spell trouble by exposing the battery to undue overcharge on a long drive.http://batteryuniversity.com/learn/article/absorbent_glass_mat_agm
Vehicle lights - Page 1
Forum section: electronics / beginners

author: aerondon
author_rank: Newbie
timestamp: August 31, 2020, 02:11:45 am
content: Hello,I would like to get some advice and maybe to see if someone can check over my design work?I have a basic setup of a few power regulators and a VU meter chip.The basic design idea is that using a switch you can decide between bar or dot mode. Also an RC network in order to create a slower rise in voltage, to get that sequential effect.What I need to work out is if the resistor attached to pins 6&7 is adequate current limiting for my ss8850s? Or do i have to add a 1k to all of the base pins of my fets?From what I have read, the resistor on 6&7 is designed for "brightness" on the led, which should translate to current flow through my transistors.Its my first proper design on paper and have started to build it, just need to make sure there is nothing silly in my design I am missing.https://photos.app.goo.gl/CvCr5eJgJy5XSWk69Thanks again.
Velleman HPG1 1Mhz Pocket Function Generator - Page 1
Forum section: electronics / beginners

author: tony3d
author_rank: Frequent Contributor
timestamp: November 29, 2013, 11:23:13 pm
content: Hi all, has anyone used this pocket function generator? Is it ok for a beginner hobbiest? I can get it new for $104.

author: Stonent
author_rank: Super Contributor
timestamp: November 29, 2013, 11:44:22 pm
content: You can buy or build an XR2206 function generator for very cheap. Less than 20 in parts. The chip sells from 3 to 10 dollars depending on what options you have. Couple that with about 5 or 6 resistors, 3 potentiometrrs , a few quality capacitors and 12 to 15 volt supply source and you've got a 2 MHz generator.

author: Smokey
author_rank: Super Contributor
timestamp: November 30, 2013, 03:59:30 am
content: The main thing that would be a deal breaker for me is the 8Vp-p output voltage. The square wave rise/fall times being 0.2uS isn't anything to write home about either.Now if you know that won't be a limitation for whatever you are going to use it for then ya, it's a nice small package especially if you need to use it in the field or something.

author: Six_Shooter
author_rank: Regular Contributor
timestamp: November 30, 2013, 04:11:57 am
content: I haven't used that particular function generator, but I have looked at it and considered it myself. I decided to pass on it because of the 8 Vpp limitation and some other reasons that I don't recall right now.I do own a Velleman PC based O-scope, and would not recommend it to anyone. I think it's just inherent to how most PC based scopes work, but my experience has been less than pleasing with this. I still use it, because it's currently the only (working) O-scope I own.You will have to look at what you need in a function generator, and decided if it will be good for you.I have since bought an Elenco XR2206 based function genertor kit, that I aso would not recommend, well, it's better than nothing, but my plan is to rebuild it, using some different components and add to the circuit based on the datasheet for the XR2206 IC, and couple that with another XR 2206 IC I received recently and some other parts to make my own custom 2 (or 3) channel function generator. Rolling your own can be fun and you will learn something from it.

author: hiddensoul
author_rank: Regular Contributor
timestamp: December 26, 2013, 12:30:54 am
content: I own the velleman HPG1 and it is great for field work, yes it has limitations but it is pretty rugged for the price and is in a nice package. The battery pack is replaceable, it uses a pack of NiMh AA's cant recall if it is 2 or 3 but easy enough to repack if needed.

author: tony3d
author_rank: Frequent Contributor
timestamp: December 26, 2013, 04:25:52 am
content: Quote from: hiddensoul on December 26, 2013, 12:30:54 amGot one for Christmas. I like it so far.
velleman PCSU1000 pc dso - Page 1
Forum section: electronics / beginners

author: m3vuv
author_rank: Super Contributor
timestamp: April 23, 2022, 04:56:48 pm
content: has anyone used one of these,if so how do they compair to a propper 60mhz dso?

author: Doctorandus_P
author_rank: Super Contributor
timestamp: April 23, 2022, 05:29:52 pm
content: Looks like a toy.(But I do not have, nor used one).But it's vertical range of only 5mV to 2V per division shows it does not have a proper front end and it only has a buffer length of 4k and a sample rate of 50MHz.Those are laughable spec's for these days.On top of that, all USB scopes are cumbersome to use. Having some real buttons to push and turn are a much better user interface for an oscilloscope.PC based scopes are mostly useful where the PC connection outweighs the lack of ergonomics of a decent oscilloscope.I had a look at a bunch of websites, and before I found a place that had it, I saw a bunch of "not available" and "discontinued" listings.If you really want a PC based scope for cheap, then consider the Hantek 6022BL. It's also not a "decent" scope, but it costs around EUR 60 and for that price it may be worth the gamble.If I'd want a decent PC based scope, I would probably buy one fromhttps://www.picotech.comThey have a fairly good reputation.But if you want some decent bandwidth and sample depth, then it costs as much as any benchtop scope.Unless you have a real good reason for wanting such a scope, a separate benchtop scope with integrated LCD and panel with buttons should always be your first choice.Ignore the "fnirsi" garbage, but apart from that, decent scopes start at around EUR250 these days.

author: m3vuv
author_rank: Super Contributor
timestamp: April 23, 2022, 06:21:08 pm
content: will give it a miss then as i already have 3 dso's and 2 analog scopes,cheers anyway.
Velleman VTSS5 locking nut replacement - Page 1
Forum section: electronics / beginners

author: pfm
author_rank: Regular Contributor
timestamp: February 16, 2024, 05:49:50 pm
content: I lost the locking nut of my Velleman VTSS5 soldering station. I cant find the exact replacement either but I do see the Weller KN60 which "looks" identical. Can someone who has experience with both soldering irons/stations say if they are interchangeable ? Or if you have a Weller and can measure the exact inside/thread diameter of the nut and the threads on the iron as well that would be very helpful too.Thanks!

author: Jwillis
author_rank: Super Contributor
timestamp: February 18, 2024, 11:29:09 pm
content: Quote from: pfm on February 16, 2024, 05:49:50 pmThere is a vendor on Ebay that sells packages of tips that include a nut.https://www.ebay.com/itm/371651448665Not the cheapest solution but at least you get the right part your looking for. Or you could ask the vendor if he or she sells just the nut.
Vendor snapped PCB - Page 1
Forum section: electronics / beginners

author: joshua1909
author_rank: Newbie
timestamp: September 25, 2023, 02:10:39 pm
content: Hi!I'm currently working on a side project reverse engineering a circuit. The vendor has snapped off part of the PCB where the MCU test points are. Kind of like this:I'm getting by through scratching the board to expose copper and using some pretty fine probes to attach, but it's less than idealThought I'd see if this is a solved problem? Is there something else people do in this situation?Thank you!Josh

author: BrokenYugo
author_rank: Super Contributor
timestamp: September 25, 2023, 02:59:50 pm
content: Assuming no internal layers.Glue it back together (5 minute epoxy? IDK) with some added reinforcement along the edges, then scrape back the solder mask and solder short chunks of wire to bridge all the breaks, use as normal.Or solder on lengths of suitably fine wire and terminate to a header or whatever, be mindful of straining a connection like that though, or fix the wires with hot melt glue or something so they can't easily rip off the board along with a chunk of that trace.

author: BILLPOD
author_rank: Frequent Contributor
timestamp: September 25, 2023, 05:23:08 pm
content: Good Morning joshua1909, and bill the vendor for a new PCB, plus labor for for installation.

author: liaifat85
author_rank: Regular Contributor
timestamp: September 28, 2023, 08:50:27 am
content: You should complain to them ASAP. Did you do any video at the time of unboxing it?

author: joshua1909
author_rank: Newbie
timestamp: September 28, 2023, 11:50:40 pm
content: Hey all!Thanks for the replies. The vendor isn’t at fault, the device is functional and I actually think it’s a “feature” because they don’t want the board reverse engineered.Sorry for the misleading picture, I don’t actually have the section that was snapped off, I think it was just headers to CWD pins. The PCB break looks like that picture though.

author: Infraviolet
author_rank: Super Contributor
timestamp: September 28, 2023, 11:57:05 pm
content: Do you have both sides of the snapped board? Or is this a situation where you have one half and are trying to gues at what the other may have contained?

author: joshua1909
author_rank: Newbie
timestamp: September 29, 2023, 12:27:50 am
content: I’ve traced the snapped traces back and they are the 2 CWD pins. I don’t have the section that was snapped off.

author: joshua1909
author_rank: Newbie
timestamp: September 29, 2023, 12:29:02 am
content: I’m pretty sure it was just headers to connect to debug during manufacturing, then they snap it off when they ship it.

author: joshua1909
author_rank: Newbie
timestamp: October 01, 2023, 11:51:08 am
content: Yeah that is one positive!Thanks all for the replies.
Ventilation Holes On Soldering Iron - Page 1
Forum section: electronics / beginners

author: Kagord
author_rank: Contributor
timestamp: June 26, 2020, 01:14:07 pm
content: Hi,I'm new at this, I was thinking of taping up the ventilation holes on my soldering iron to make it hotter, as I'm having some trouble melting my lead solder. Is that a good idea? It has holes that looks like this.

author: Ysjoelfir
author_rank: Frequent Contributor
timestamp: June 26, 2020, 01:26:54 pm
content: If you have one of those flesh burning wood carving chisels you should think about getting a decent one, instead of doing a hackjob like thatI think those holes are there so that the temperature drop towards the handle is big enough to not burn yourself - well, at least if you know where to grab that thing.

author: Benta
author_rank: Super Contributor
timestamp: June 26, 2020, 01:47:53 pm
content: I wonder where they get those soldering operators with asbestos fingers...

author: Gyro
author_rank: Super Contributor
timestamp: June 26, 2020, 04:45:40 pm
content: Quote from: Kagord on June 26, 2020, 01:14:07 pmYou will probably enjoyhttps://www.eevblog.com/forum/chat/stock-electronic-image-fails/

author: Bud
author_rank: Super Contributor
timestamp: June 26, 2020, 05:20:52 pm
content: Quote from: Benta on June 26, 2020, 01:47:53 pmAll of the magic is in the Yellow protection glasses

author: Zero999
author_rank: Super Contributor
timestamp: June 26, 2020, 06:28:30 pm
content: Quote from: Kagord on June 26, 2020, 01:14:07 pmIf you can hold the soldering like that, then it's either broken or not turned on. It should get so hot you'll burn your hand and any tape covering the holes!
Verilog code required  - Page 1
Forum section: electronics / beginners

author: Gurumurthy
author_rank: Regular Contributor
timestamp: June 21, 2023, 01:28:46 pm
content: HI AllI want verilog code for state machine which detects sequence 0101 with mealy and moore model. I want to understand what is the difference while writing verilog code and seeing the output in wave form veiwer.The problem is no book shows the difference. The difference is in moore-output depents on state and mealy- output depends on state and present input. I want to understant this with an example which explore all the points. Sorry and thanks you in advance.

author: ejeffrey
author_rank: Super Contributor
timestamp: June 21, 2023, 02:57:44 pm
content: This sounds like a homework problem, can you show what you have so far? Like any verilog code or just the state diagrams?The main difference is that the moore state machine output is one cycle delayed relative to the mealy, but the mealy has combinatoric logic on the output signal so it can have glitches if driving an output directly or worse timing if driving another flip flop.

author: ejeffrey
author_rank: Super Contributor
timestamp: June 21, 2023, 03:01:44 pm
content: Sorry I should clarify:A Moore state machine can have combinatoric logic on the output although often it does not. Specifically a mealy state machine has combinatoric paths from the input to the output. That is what can generate long combinatoric paths that are hard to meet timing.

author: Gurumurthy
author_rank: Regular Contributor
timestamp: June 21, 2023, 03:10:27 pm
content: Sir,In both the cases output comes after a clock cycle. What is the mistake in Moore machine? How to correct it.Moore machine_101::https://www.edaplayground.com/x/NStcMealy mahine::https://www.edaplayground.com/x/ptp4

author: radiolistener
author_rank: Super Contributor
timestamp: June 22, 2023, 06:39:32 am
content: I think this is because your Mealy Machine implementation is not optimal. But this is interesting subject. I just realized that I'm not familiar with Mealy and Moore Machine properties and how to convert from one to another. Needs to learn it...
Very confused by DMM reading of Drain Current on NMOS circuit  - Page 1
Forum section: electronics / beginners

author: Mattjd
author_rank: Regular Contributor
timestamp: March 18, 2017, 04:47:33 pm
content: 0down votefavoriteHello I am working on a lab that pertains to the IV characteristics of n type MOSFETS.The lab calls for recording the value of the drain current while increasing VDS/VGS from 0 to 6 volts in steps of 1 volt.I constructed this circuitAs I increase the voltage for VDS/VGS I am experience I weird issue with the Drain Current readings. It issue is that it is not very stable at all. The current is constantly changing. What I mean by constantly changing is that when I up the voltage from 5 to 6 volts, the current obviously jumps but then quickly plummets close to 40 mA in a matter of seconds, without anything else changing.I took a video of it.https://youtu.be/-LMfpRZQWVAis there anything I can do with the circuit to fix this?

author: rstofer
author_rank: Super Contributor
timestamp: March 18, 2017, 04:53:09 pm
content: What limits the current (and heating)?In theory, the MOSFET is conducting as much current as the supply can produce in short circuit.In any event, it looks like a heating related issue to me. Does the device start cool and get hotter?

author: Mattjd
author_rank: Regular Contributor
timestamp: March 18, 2017, 04:59:31 pm
content: Quote from: rstofer on March 18, 2017, 04:53:09 pmWhy yes it does. I just left my finger on it for the entire increase from 0 to 6 and it got very hot around 5 volts.So, to get the most accurate readings, should I wait a certain amount of time in between readings?

author: Kleinstein
author_rank: Super Contributor
timestamp: March 18, 2017, 05:04:27 pm
content: The circuit might pic up some external noise / Rf signals. Due to nonlinear response this can end up in changing the "DC" reading too. If the drain side load with the meter turns resonant, there is a small chance is might even oscillate.For the higher currents there might be self heating that can shift the curve. Also air drafts might change the temperature. Waiting a well defined time might help. This could be either very slow or up to pulsed measurement with a faster meter.If might help to keep the mobile phone away from the circuit or at least switch to flight mode.It also depends on the voltage supply how stable the driving voltage can be. It does not look that bad.

author: Mattjd
author_rank: Regular Contributor
timestamp: March 18, 2017, 05:12:11 pm
content: Yeah I was using my second DMM to measure the temp, it reaches 100 Centigrade at 5 volts, rather fast too. Its probably best if I just take the measurements fast and record the temperature also. Then just talk about it in the write up.
Very hot heating element wire lead connections - Page 1
Forum section: electronics / beginners

author: corrado33
author_rank: Frequent Contributor
timestamp: February 24, 2016, 05:56:30 pm
content: Hi all,I need some ideas. I have a furnace that gets up to 1000 C and I need to attach leads to parts of it. The connections will also get up to around 1000 C so I can't simply solder it. I have been using completely physical connections but after a while those break off. My NiCr wire is getting shorter and shorter so I need a more permanent connection. (It's actually Kanthal wire, but the same principle.)Tomorrow I'll have access to a spot welder, so I will try that. However today I think I'm going to experiment with melting the wires together. I have some extra wire that I can use as practice. Basically I was going to attach some leads a cm or so apart on two separate pieces. Physically hold the wires together somehow, then pass a crap ton of current through it. (10A maybe?) I don't have any power supplies that'll go above 12A unfortunately. Well, none at work (home is a different story, but that's in my house, which I'd like to not burn down.)Any other ideas? Do you think melting them together will work? Do you think I'll be able to melt them?I could always use a couple of car batteries if my power supplies can't provide enough power... I mean, that short of a piece of wire is essentially a short circuit, so I should have no trouble getting many many amps to flow through it.Yes, I realize this sounds like a terrible idea. But at this point I have few other choices. The first choice is the spot welder tomorrow though. This melting idea is only a backup plan.

author: Tomorokoshi
author_rank: Super Contributor
timestamp: February 24, 2016, 06:15:11 pm
content: Do you have a picture of the area where those connections would be made?Perhaps look into the methods used for welding the tips of thermocouple wire together.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 24, 2016, 08:54:06 pm
content: AFAIK, crimping is used for those.Take the wires out of the hot zone, and use much heavier metal (thicker = less heat dissipation, more thermal conductivity) to make the joint. Thermal cycling and oxidation are the problem, even if it's all refractory metals.Also mind that Kanthal is brittle after use, IIRC, so you might not be able to service it...Tim

author: Shadetreeprops
author_rank: Regular Contributor
timestamp: February 24, 2016, 11:54:46 pm
content: Quote from: corrado33 on February 24, 2016, 05:56:30 pmFirst use large physical connections to extend your wires back out, cover with heat shrink, Then purchase REFRACTORY LINING..and insulate the wires with it. wrap with metal tape, and put a metal mesh insulator around it. then pad the area where the heat comes from with more REFACTION insulation. This stuff can withstand these temps, and should then stop the damage to the wires.just like in really high end Arch welders, you can sometimes find it with the refraction lining in them. or like my digital smelting furnace, they have to protect the wires with that stuff from the heat..melts everything up to platinum like nothing.
Very low current measurement. How to? - Page 1
Forum section: electronics / beginners

author: Ludo3.14
author_rank: Newbie
timestamp: July 11, 2016, 07:10:01 pm
content: Dear all,I'm trying to develop a miniaturized picoammeter to measure very low current (in the order of nA) to be analyzed and transmitted.Keithley 6485/6487 are way too big for my purpose.Do you suggest any particular hardware (opamps) that are both small and effective?Thank you in advance!

author: Kleinstein
author_rank: Super Contributor
timestamp: July 11, 2016, 07:18:14 pm
content: The circuit of choice is usually a transimpedance amplifier with an CMOS OP. Suitable OP's could be LMC6001, LMC6041, LMC6062 and similar. A few nAs is not even that low - so even simple CMOS types like MCP6001 , TLC271 might be good enough.

author: uncle_bob
author_rank: Unknown
timestamp: July 11, 2016, 11:44:50 pm
content: HiIs the current ground referenced or is it running between two nodes that need to be isolated?Is there already power associated with those nodes (if they are floating)?Lots of possibilities ....Bob

author: danadak
author_rank: Super Contributor
timestamp: July 12, 2016, 01:24:18 am
content: Bob Pease discussion on this -http://electronicdesign.com/test-amp-measurement/whats-all-femtoampere-stuff-anyhowWhat's All This Teflon Stuff, Anyhow?http://electronicdesign.com/test-amp-me... uff-anyhowWhat's All This Femtoampere Stuff, Anyhow?http://electronicdesign.com/test-amp-me... uff-anyhowRegards, Dana.
Very low-power voltage reference ICs - Page 1
Forum section: electronics / beginners

author: raff5184
author_rank: Regular Contributor
timestamp: March 10, 2020, 10:15:43 pm
content: Hi I need to generate a reference voltage to be given in input to a low power comparator IC such as an LMV7291 or a TLV3201.The reference voltage can be a standard 1.2V-1.5V value or an adjustable oneI'm looking for one or two different devices:1) something (very) low-power in the order of microamps or a couple of mW top.2) if it even exists, I also need a device that with a lowsupplyvoltage, e.g. 0.8-1V, lower than the reference, can still give an output voltage of 1.2-1.5V, again absorbing as little current as possible. Of course I'm aware that the extra voltage has to come from somewhere

author: Zero999
author_rank: Super Contributor
timestamp: March 10, 2020, 10:32:40 pm
content: There are plenty of low current, low voltage reference ICs available. The TLVH431 springs to. mind.Unfortunately all reference ICs need a higher supply voltage, than the output voltage. To create a higher voltage, some sort of voltage booster is required. At very low currents, a charge pump is probably the most suitable. It works by charging capacitors in parallel and connecting them in series to produce a multiple of the input voltage. I can't think of any which will work at under 1V though.

author: not1xor1
author_rank: Frequent Contributor
timestamp: March 11, 2020, 06:26:53 pm
content: Quote from: Zero999 on March 10, 2020, 10:32:40 pmLM385 and the likes require just 10µA to work properly that is 10 times less current than TLVH431

author: k8byp
author_rank: Newbie
timestamp: March 13, 2020, 05:31:11 pm
content: 10 turn precision potentiometerthats how i do it!

author: Siwastaja
author_rank: Super Contributor
timestamp: March 13, 2020, 05:35:02 pm
content: 2) instead of using higher reference voltage, scale the signal voltage (which is compared against the reference) down.

author: raff5184
author_rank: Regular Contributor
timestamp: March 13, 2020, 06:10:36 pm
content: Quote from: not1xor1 on March 11, 2020, 06:26:53 pmGrazie I'l try itQuote from: k8byp on March 13, 2020, 05:31:11 pmI need a small IC, (about 3mm x 3mm or so)Quote from: Siwastaja on March 13, 2020, 05:35:02 pmJust a voltage divider with resistors? A more efficient way of doing it?Quote from: blueskull on March 13, 2020, 05:41:28 pm1) Would this require current <mA?2) what type of harvester could you suggest? I'm only familiar with the LTC3588-1 mounted on thehttps://www.analog.com/en/design-center/evaluation-hardware-and-software/evaluation-boards-kits/dc2042a.htmlor the Texas Instruments BQ25504

author: Siwastaja
author_rank: Super Contributor
timestamp: March 13, 2020, 09:07:23 pm
content: Quote from: raff5184 on March 13, 2020, 06:10:36 pmThat should usually work out, unless you have a difficult combination of requiring high input impedance, high speed and low noise.If you end up using very high resistor values (several megaohms) to reduce the loading of the signal, then you may want to look at the bias current specifications of the comparator.
Very simple memory controller - Page 1
Forum section: electronics / beginners

author: pigtwo
author_rank: Regular Contributor
timestamp: August 19, 2013, 05:20:36 pm
content: Hi everyone!So a while back I started working on a very (VERY) simple breadboard computer. I ran into some problems when trying to write to memory. In my first attempt I didn't even have a memory controller and I just tied CS low and let fate determine if my address lines would settle at the same time(and instantaneously). And unsurprisingly they did not.Now I'm trying to make a very simple memory controller that will unassert CS while memory is not being used. Then during a write cycle, it should keep CS low and give the address lines time to settle. Then assert CS for a little bit, then unassert CS again before the end of the write cycle.The best way I've thought to do this is to have a separate clock that runs at 8 times the system clock. Then load a shift register with a pattern like '11000011' and have the output of the shift register go to the CS pin of the memory. The shift register would get the 8 times clock so that in one write cycle(IE one system cycle) it would shift all the way through that pattern.One of the problems I have with this is that I initially have to load that pattern into the shift register. But since i only have to do it once in the beginning, I don't mind just putting a button on the bread board and pressing it every time.So before I try to build this, I wanted to check here and see if there is a better(IE simpler) way to do this or if there is any obvious problems with this design.Thanks!

author: Unknown
author_rank: Unknown
timestamp: August 19, 2013, 05:30:00 pm
content: What CPU are you using? What memory chips? Got a schematic of what you've made so far?

author: pigtwo
author_rank: Regular Contributor
timestamp: August 19, 2013, 06:33:42 pm
content: I'm not using any pre-made CPU, I made it out of a couple of multiplexers and logic gates. I'll post a picture of the CPU(although ALU is probably a better name) and the whole schematic. The picture of the whole thing includes part of memory controller I was testing but I didn't like how complex it was.I'm using HM6116P-4 memory chips.This is my first attempt so it is ridiculously simple. It has a 4-bit data bus and a 16-bit instruction bus. I haven't implemented any segment registers or anything so I am stuck at a max of 16 instructions/data locations. Which I know is stupid but, I'm more just doing this for fun.
Very small wireless charging circuit (and battery) - Page 1
Forum section: electronics / beginners

author: Purduephotog
author_rank: Regular Contributor
timestamp: August 14, 2024, 06:03:48 pm
content: I'm looking to implement a very small wireless charger for a dog collar- swapping out 3x mercury batteries is a PITA, and since I can't fit a liion cell in there without flipping the battery posts- I might as well see what I can cram in there.Now I know they can be made very small for earbuds and watches, but most of what I've seen is fairly large Q-type compatible.Has anyone put together something like this and if so, which did you use? Bonus if it's from Aliexpress for ease of ordering.-and yes, I could put a tiny little liion charger board in there, or a BMS for an 18650 cell, and wire some prongs out- but where would be the fun in that?Thanks!

author: Infraviolet
author_rank: Super Contributor
timestamp: August 17, 2024, 07:20:14 pm
content: Before making any decisions, look carefully at the power consumption of the collar (is this one of those LEDs flashing at night sort so you can see which bushes the dog has rushed in to), and how long it has to run for between charges.You'll need to fit in a big enough battery for that, then make further room for wireless charging circuitry. The simplest wireles charging would be done with a big coil on the charging device, which is set up as the inductor in an LC parallel tank circuit. The device then has it's own LC parallel tank tuned for the same frequency, potentially using a purchased inductor as its coil (10mH coils with diameters around 1cm, lengths around 2cm... can work so long as not shielded), this picks up an AC signal which you need to rectify to DC with which to then power a battery charging circuit (designed for whichever battery chemistry you're battery uses). There will always be more losses of power during charging, due to the intermediate steps of DC-->AC in charger's LC tank-->induced AC in device's LC tank-->rectified DC than there would in just supplying DC to the battery charger circuit in the first place.These four videos, and I know video is often less helpful then a written article with images, give some useful info. They were ones I found in my bookmarks history, having read up on LC induction for another reason a while back (I built an absolute angle inductive resolver).
VERY unusual UC2845 based push-pull power supply? - Page 1
Forum section: electronics / beginners

author: LinuxHata
author_rank: Frequent Contributor
timestamp: March 31, 2023, 04:22:40 am
content: Hello.Got a bunch of 12VDC "Industrial" power supplies. These are branded "SANPU" and model is S350-12.I decided to have a look on internals, to get know, how well they are made, etc.I was expected to see a typical KA7500b circuit, but it's internals really amazed me!First of all, there is UC2845, which is by no means a push-pull controller.2nd, it's output is complimented with additional output stage, built using PNP+NPN transistors, which drive a transformer with two output windings, which are connected to each mosfet, respectively. Mosfets are connected to individual windings of "big" transformer.There is an additional winding on big transformer, which, thru the 7812, supplies the PWM chip and other components with the power.All other parts of circuit, including secondary side, are pretty "normal"So what circuit is this? just two flyback output stages driving a single transformer, or they managed to pull out the incredible and make forward converter with UC2845?photo of PCB is attached.Anyone has circuit for such power supply?

author: amyk
author_rank: Super Contributor
timestamp: April 01, 2023, 12:22:06 am
content: Doesn't sound all that unusual. Look for "two switch forward" here:https://danyk.cz/s_atx_en.html

author: jonpaul
author_rank: Super Contributor
timestamp: April 01, 2023, 12:23:58 am
content: we used double Foward since 1990 in 700 W 35A medical.Simple ,reliable and efficientJon

author: LinuxHata
author_rank: Frequent Contributor
timestamp: April 01, 2023, 06:22:43 am
content: I know about "two switch forward" type of power supplies, but this is NOT a "two switch forward" circuit. In "two switch forward" circuit, the primary winding is single, connected between the transistors, but in my case it is double winding, center tap going to positive, and two windings going to transistors, like you would do in a push-pull circuit, this is why I asked.

author: jonpaul
author_rank: Super Contributor
timestamp: April 01, 2023, 12:27:06 pm
content: OP, just trace the power circuit of the PCB, takes you 10 min.Post circuit trace and both sides of unitj

author: dobsonr741
author_rank: Frequent Contributor
timestamp: April 01, 2023, 09:17:42 pm
content: Is there an inductor on the secondary side, direct connected to the secondary without a cap connected first? It would indicate forward, otherwise it’s a fly back.In other words, if the series inductor on the secondary just an LC filter to the DC output it’s a fly back. If the inductor is in the same topology as in a buck converter, it’s a forward.

author: amyk
author_rank: Super Contributor
timestamp: April 02, 2023, 04:24:56 am
content: Quote from: LinuxHata on April 01, 2023, 06:22:43 amIs it a half-bridge then? Like others have said, post a schematic if you want some more identification/discussion.
Very very simple circuit to test oscopes wanted - one resistor ? - Page 1
Forum section: electronics / beginners

author: ez24
author_rank: Super Contributor
timestamp: May 23, 2015, 06:00:34 pm
content: HiI have a Wavetek 145 and a Rigol DS1054Z. I ordered a DS112 chinese scope ($50).http://www.aliexpress.com/item/DSO112-Touch-Screen-2-4-TFT-Mini-Digital-Oscilloscope-Pocket-Oscilloscope-2MHz-2-5Msps/32257827169.htmlOh no - no longer available !I want to do some simple tests to take pictures of waveforms on the DS112 (if I get it) but I want to be careful and not hurt anything. Based on a previous post I think I hooked up my Wavetek wrong to the Rigol (power problems) using a BNC to BNC.So I am thinking of connecting the Wavetek at a low Vpp ( 1 Vpp ? ) across a 1 k resistor using a BNC to alligator lead. Then probe across the resistor with both the Rigol and DSO112 to check the waveforms from the Wavetek on both the Rigol and DSO112.Someone here would like to see what the DSO112 can do, so I would like to do some very very simple meaningful tests. Any suggestions?Please no - 33rd harmonic of the 2nd nyquest quantum wavelet in it's 3rd orbital spin because I do not have a Tek AGO3000.thanks

author: Electro Fan
author_rank: Super Contributor
timestamp: May 23, 2015, 11:11:34 pm
content: I think if you connect your Wavetek to your Rigol with a BNC to BNC cable it is highly unlikely that you will hurt anything.Just set the Wavetek at 1Vpp and 1kHz with a sinewave and see if the Rigol shows you 1Vpp and 1kHz. If it shows you a different voltage it's probably because of what was discussed in other thread (you need a 50 ohm feed through terminator on the Rigol input). But even without the terminator you won't hurt anything, you just won't get an accurate voltage reading.Try it with and without the 50 ohm terminator. Then keep the 50 ohm terminator on the Rigol and proceed as follows:Try changing the frequency on the Wavetek and see what happens on the Rigol. Then try changing the voltage on the Wavetek and see what happens on the Rigol. Then try changing the Wavetek from a sinewave to a square wave and see what happens on the Rigol. Then leave the Wavetek alone and start playing with the controls on the Rigol and get familiar with what they do.Let us know what you learn.
Very Very Very tiny SpDT switch - Page 1
Forum section: electronics / beginners

author: Falcon69
author_rank: Super Contributor
timestamp: November 12, 2013, 12:06:29 am
content: I am looking for a very small switch. SPDTI've tried the usual places, eBay, Digikey, Mouser, etc. They don't have any small enough. The smallest I found was 1.2mmx3mmx7mm. HxLxWhttp://www.ebay.com/itm/10pcs-On-Off-2-Position-1P2T-SPDT-Horizontal-Miniature-SMT-SMD-Slide-Switch-/310759174022?pt=LH_DefaultDomain_0&hash=item485ab0af86I need them smaller than that for my application.Any Ideas?

author: elgonzo
author_rank: Unknown
timestamp: November 12, 2013, 12:27:11 am
content: I don't know how small the switch should be, but the ALPS SSAJ120100 has a length of only 6.5mm (inclusive solder leads).Mouser:http://www.mouser.com/ProductDetail/ALPS/SSAJ120100/?qs=sGAEpiMZZMtHXLepoqNyVRqEPgx26l6VFyhJPmjLgOI=