hybridfree/eevblog-posts huggingface dataset:
L293D H-Bridge - peak-to-peak Voltage? - Page 1
Forum section: electronics / beginners

author: Didix
author_rank: Regular Contributor
timestamp: March 20, 2017, 06:41:36 pm
content: Hi thereI try to build a driver for a piezo buzzer driven by an ESP8266.What I am using is a L293D (http://www.ti.com/lit/ds/symlink/l293.pdf)My piezo is connected between 1Y (pin 3) and 2Y (pin 6).3Y & 4Y are not connected.The Voltage at VCC2 (pin 8 ) is 12V.Well, everything runs fine and the piezo drives my wife crazyHowever, when I hook up my scope between 1Y and 2Y I would expect 24Vpp (peak-to-peak).But what I am seeing is 12Vpp.Or is that a misconception?-Didix

author: Didix
author_rank: Regular Contributor
timestamp: March 26, 2017, 05:48:14 am
content: no activity -> case closed

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 26, 2017, 07:29:03 am
content: Uhhh, "between"?You can't clip probe ground onto a signal that's not ground... bad things will happen.Tim

author: Didix
author_rank: Regular Contributor
timestamp: March 26, 2017, 07:38:16 am
content: The scope is floating, so no common ground.Relative measurement should not be a problem.

author: tatus1969
author_rank: Super Contributor
timestamp: March 26, 2017, 08:38:30 am
content: it should be 24v p-p. sure your scope is floating? maybe a hidden ground from a usb connection? you can check easily by probing both outputs separately.

author: Didix
author_rank: Regular Contributor
timestamp: March 26, 2017, 08:42:26 am
content: Actually, one of the channels was not switching to hi.Now everything works as expected.Thanx for supporting!
L298N Motor Control Board - Diodes - Page 1
Forum section: electronics / beginners

author: berwick53
author_rank: Newbie
timestamp: February 27, 2015, 06:14:24 pm
content: I'm about to receive through the post a L298N motor control board that will be powered via two 6V 2800mAh batteries in series. Will I need a snubber diode to protect the batteries from back-emf caused through the inductive load aka the motors when the board is connected up? or do the LEDs/diodes on the board perform this function?The board in question.http://www.ebay.co.uk/itm/L298N-Stepper-Dual-H-Bridge-Motor-Driver-Module-Controller-Board-for-Arduino-UK-/291272112778?pt=LH_DefaultDomain_3&hash=item43d12bba8a

author: electr_peter
author_rank: Unknown
timestamp: February 27, 2015, 10:01:28 pm
content: L298N board from eBay has enough diodes to keep you from trouble. If you use rechargeable batteries, you don't have to worry about them recharging. Parallel diode serves to protect transistors from voltage spikes and from general EMI, not the batteries.In some circuits diode in series with a power source is used if there is significant inductance and PSU cannot take power back. Rechargeable batteries do not need series diode for most cases.
LM339 Question - Page 1
Forum section: electronics / beginners

author: junkandshitandjunk
author_rank: Newbie
timestamp: June 24, 2023, 01:22:43 pm
content: hello, can someone tell me what to change in this circuit to be able to work with 3.3v logic, now it works with 5v logic fine. Its simple Kline adapter.

author: RoGeorge
author_rank: Super Contributor
timestamp: June 24, 2023, 02:01:44 pm
content: Where it says "+5v" with red in the schematic, you need to apply only +3.3V instead of 5V. So, no changes to the schematic, only change the +5V with a +3.3V. After doing this, if you measure at the node between R5 and R6, it will be 1.5V instead of 2.5V.

author: junkandshitandjunk
author_rank: Newbie
timestamp: June 24, 2023, 02:27:44 pm
content: so easy, ok thanks i will try.

author: MasterT
author_rank: Frequent Contributor
timestamp: June 24, 2023, 03:07:00 pm
content: Be aware, that Common-mode input-voltage range according to data sheet LM339 is 0 - Vcc-1.5, so lowering power supply voltage down to 3.3V CM becomes 0-1.8V, and 0-1.3V over temperature range

author: magic
author_rank: Super Contributor
timestamp: June 24, 2023, 03:12:22 pm
content: The chip is powered from 12V so nothing will get loweredI agree with RoGeorge, this circuit looks like it will "just work" with any common logic voltage on the left side.

author: junkandshitandjunk
author_rank: Newbie
timestamp: June 26, 2023, 06:12:35 pm
content: Yes it works, thanks!
L3GD20H Gyroscope Help (SPI) - Page 1
Forum section: electronics / beginners

author: yash101
author_rank: Contributor
timestamp: May 14, 2015, 04:43:24 am
content: I need help in getting my gyroscope to work. The datasheet is here:http://www.st.com/st-web-ui/static/active/en/resource/technical/document/datasheet/DM00060659.pdfMy microcontroller is a Parallax Propeller. I am programming it in C (SimpleIDE) because I am a C/C++ programmer and it is first knowledge for me.I am trying to figure out how to read the X, Y and Z data from this device. I have CS mapped to Pin 0, MISO mapped to Pin 1, MOSI to 2 and CLK to 3.What would help my the most is if someone could help me understand how to read the data sheet and understand it.I do not know if the communication is MSB first or LSB first. I do not know how to initialize this device. Nothing. I am unable to follow the datasheet and understand how to use it.Thank You!

author: agehall
author_rank: Frequent Contributor
timestamp: May 14, 2015, 05:09:06 pm
content: Looking at figure 3, I'd say it operates MSB.

author: yash101
author_rank: Contributor
timestamp: May 14, 2015, 05:26:24 pm
content: Thanks. Also, how do I initialize the device and begin retrieving values?I am initializing the CS and CLK pins. After that, what should I send it? 0b00000000 is what I am currently sending it because I do t know how to use it.

author: agehall
author_rank: Frequent Contributor
timestamp: May 14, 2015, 07:56:17 pm
content: Are you trying to use SPI or I2C? All you need to know is in chapter 5 and 6 of the data sheet, so you probably need to read up on those sections. They show exactly how you are supposed to transmit data to and from the device.Everything seems to be register based (I have just skimmed the data sheet, so there could be more "advanced" options too) so basically you send a read read command to the device and then you read back the data in the following clock cycles.

author: yash101
author_rank: Contributor
timestamp: May 14, 2015, 10:12:12 pm
content: I know, but I'm not able to understand the data sheet. Do you have any resource which will explain it step by step?

author: FreddyVictor
author_rank: Regular Contributor
timestamp: May 14, 2015, 10:30:17 pm
content: Quote from: yash101 on May 14, 2015, 05:26:24 pm1st of all, take a look at some code like this (for Arduino):https://www.nordevx.com/content/l3gd20h-gyrosince arduino has SPI built-in, you'll need to replace the SPI.transfer() function with your own bit-banging onean example is the bitbang() function here:http://hifiengineering.blogspot.co.uk/2013/07/bit-banging-serial-data-with-arduino.htmlyou'll need to set MOSI,SCK and CS as output and MISO as input pins (is that what you mean by initialize ?)I would start by writing some simple code to read the WHO_AM_I register whichshouldreturn 0b11010100 ( 212 )TBH, SPI isn't too easy via bit-bang method (Propeller chip seems very basic !), since your chip has i2c, maybe try that instead ?
L6470 - Sensorless Stall Detection - Page 1
Forum section: electronics / beginners

author: Flanbix
author_rank: Contributor
timestamp: August 12, 2014, 03:02:04 pm
content: Hi,I wonder if anyone have an experience with the Stall detection of the L6470. I can't find a way to make it detect properly when I stall the shaft by hand.Adjusting the stall threshold is tricky, the flag is either tripping while running with no load (Set too low) or not tripping at all (Set too high). There is no sweet spot.Does this feature only work when you are dealing with high current (lets say < 2A), so the change of current is actually meaningful. Or am i missing something...Thanks.

author: zerorisers
author_rank: Regular Contributor
timestamp: August 12, 2014, 03:32:43 pm
content: Code:Depending on motor speed and load angle characteristics, the L6470 offers a motor stallcondition detection using a programmable current comparator.When a stall event occurs, the respective flag (STEP_LOSS_A or STEP_LOSS_B) is forcedlow until a GetStaus command or a system reset occurs (seeSection 9.2.20 on page 66).Quote^^ Is it an internal or external comparator?This is the section of the datasheet I am looking at, it may help. Ill keep searching for more meaningful informationhttp://www.st.com/web/en/resource/technical/document/datasheet/CD00255075.pdfEDIT: Also can you include a circut diagram? That could also be beneficial.

author: Flanbix
author_rank: Contributor
timestamp: August 12, 2014, 04:06:22 pm
content: On page 8 of the datasheet you can see a "Current DACs & Comparators" block link to the "Current sensing" block, so internal one. I guess the threshold set in the register must be setting the DAC which set the threshold on the current comparator.I am using the evaluation board from ST, EVAL6470H.

author: zerorisers
author_rank: Regular Contributor
timestamp: August 12, 2014, 04:25:56 pm
content: QuoteHere is a quote with a diagram that appears to represent usage of the ADC for use of motor supply voltage compensation. Hope this is useful in some way shape or form.

author: srg0016
author_rank: Newbie
timestamp: October 06, 2014, 10:05:18 am
content: I have encountered with the same problem. I have found that L6470 rises FLAG (sets STEP_LOSS_A or STEP_LOSS_B bits of STATUS register to 0) much more often during normal operation with free shaft when motor is just accelerating or decelerating. To tell the truth, I haven't seen that L6470 rises FLAG with corresponding STATUS bits when I stall shaft by hand, what seems very strange. I have tried wide range of operating currents and current thresholds.Did anyone have success on this problem?
7805A vs L7805CV (Swap one for the other OK?) - Page 1
Forum section: electronics / beginners

author: DRTerabyte
author_rank: Newbie
timestamp: September 24, 2016, 05:06:13 am
content: I'm super new to this I'm sorry if this question has an obvious answer. I have a board with two 7805A Voltage Regulators I have several L7805CV Voltage Regulators I can swap the 7805A with. My question is would this be a good/similar replacement? If not, why? I tried looking at the datasheets on each but don't understand enough to see the difference. I see both are the same amp, voltage and pin out but everything else is chinglish to me. My reason for replacing them is the 7805A VR's seem to get super hot even with a heat sink on each, my hope is swapping them with newer VR's would help (will it?).Thank you for any help!Jose

author: Towz
author_rank: Contributor
timestamp: September 24, 2016, 05:24:46 am
content: Same chip, different manufacturer. Go ahead. However the L7805CV seems to have better documentation...If the regulator overheats you might want to use some thermal compound if you aren't. Maybe a bigger heatsink or a higher rated regulator. It might even be a problem within the circuit that is increasing the output current. Or an excessive input voltage.

author: DRTerabyte
author_rank: Newbie
timestamp: September 24, 2016, 06:50:41 am
content: Do you think it would help to swap it out? Or are the two going to put out the same heat?Thanks.

author: JPortici
author_rank: Super Contributor
timestamp: September 24, 2016, 06:52:45 am
content: prepare for trouble.we (different people) have had all sorts of problem with -CV regulators from ST lately, they seem to enter thermal protection much before what the datasheet says.also you can find that the TO-92 may have inverted pinout, for that refer to the datasheet(genuine parts from distributors. i'm suspecting a bad lot, didn't check the datecode, they went directly to trash.)

author: Towz
author_rank: Contributor
timestamp: September 24, 2016, 06:59:07 am
content: There is a small chance it might be a problem with the actual regulator and that the new one will solve it, but it seems far more likely that it's the actual circuit what overloads it. Might wanna measure if the voltage is dropping or if the current is too high.

author: Kleinstein
author_rank: Super Contributor
timestamp: September 24, 2016, 02:55:34 pm
content: The linear regulators get hot by design. Not much difference between different manufacturers.So unless the old one is broken, the new one will also get hot. It only helps to improve cooling, reduce the input voltage or reduce the current (Load).
Lab equipment for working with Motor controllers and drivers - Page 1
Forum section: electronics / beginners

author: SirRage
author_rank: Contributor
timestamp: July 29, 2021, 08:41:42 pm
content: Hey there!I really want to learn about motor controllers and in particular motor drivers. I'm new to hardware development but having fun learning it. This series was helpful as a primer,https://www.youtube.com/watch?v=gNpoTPzEkco,so now looking at trying to build some the circuits discussed in the video and dig up more material about the components.The components that I want to build and test would be: 3 phase inverter, buck converts connected and tie it together with a TI C2000 microcontroller. One of the reasons for tying the motor controllers closer together would be to sample both the rotor encoder and linear encoder to map deltas between them.I have SDG 1025 Arbitrary waveform generator and a Rigol DS 1054. I was thinking about getting a spectrum analyzer, just not sure how it would be helpful yet outside of electrical emissions testing. I was thinking about getting a better scope but not sure if a gigahert scope would really benefit me yet.The two bits of kit I was thinking about getting were: siglent SSA3021X Plus and a SDS2102X PlusThanks for the input!

author: rstofer
author_rank: Super Contributor
timestamp: July 29, 2021, 10:46:09 pm
content: Microchip has a lot of app notes on 3 phase drivers and such.Google for 'microchip 3 phase inverter' or something similar.

author: Ian.M
author_rank: Super Contributor
timestamp: July 29, 2021, 10:59:44 pm
content: If you will be working with voltages over 50V, much of your investment will need to be in enough differential voltage probes and isolated current probes, with sufficient bandwidth to monitor key parameters of all the phases of your drive's output stage. If its a direct from mains drive, the probes had better be at least Cat II rated, with an adequate working voltage margin above your worst-case DC bus voltage.Otherwise, *when* (not if!) your new drive design decides to convert itself to silicon shrapnel, its got a high probability of taking out your scope, and possibly its operator as well, leaving no signal data for a failure analysis, (and if you were dumb and won a Darwin award by floating your scope, no-one to do the failure analysis)!

author: SirRage
author_rank: Contributor
timestamp: July 30, 2021, 04:44:33 am
content: Thanks for the advice!I'm probably going to be okay with 25mhz probes. I don't think it would be any faster than that for my application. It is a bit expensive but 300 USD a prob is better than blowing something up.I'll see if I can build a low voltage version first. Just have to find a small AC servo motor I suppose.

author: mazurov
author_rank: Frequent Contributor
timestamp: July 30, 2021, 11:49:11 pm
content: You may want to also build a device similar to one in the picture. It's a "dummy load" for BLDC motor controllers. Left motor goes to the controller, right has its windings shorted together. Works very well :-).
Lab power supply and noise immunity - Page 1
Forum section: electronics / beginners

author: den
author_rank: Contributor
timestamp: March 06, 2019, 03:10:29 pm
content: Hello everyone.Short background first. We have here a test lab (equipped with sensors) which is located in a container like this:https://goo.gl/images/ZYWPxb. Over the container there is a ventilation AC motor. Driver for the motor (for controlling RPM) is inside the cell. There are two PSUs, one is some kind of PC supply with several volatge outputs, and one generic SMPS. Nothing is isolated. And as mentioned - we have different sensors there: pressure, temperature (thermocouples and thermistors), flow etc. The sensor signals are acquired by a computer. There are also mains sockets inside the lab, and also luminescent lights.Now, one problem we definetely have is noise in sensor lines from ventilation motor driver. Understandable why it is there, but I have no idea what to do with that. We also have noise when some other equipment swithes on, like CNC, which is nearby. Here I do not get why we see it - I thought the lab is kind of inside a faraday cage.So these are two direct questions - how to solve these problems?But I would like also to understand general stuff, like:- how lab mains earthing/grounding should be done? Is it important, or maybe not really?- Can bad grounding (rel. high impedance) create noise in sensor signal? I assume yes.- Sould PSUs in the lab be isolated or not?- If they are isolated - how can I read sensor voltages, if my computer (which does acquisition) is plugged into mains?- What are best pactices to sensor wiring, especially if I conatcntly have to connect additional stuff?- What are other very important points to take into account, which I am missing?Thanks in advance,Den
Lab power supply negative tied to gnd, two probes plus func gen on oscope OK? - Page 1
Forum section: electronics / beginners

author: Chris Bennett
author_rank: Newbie
timestamp: September 15, 2022, 04:56:59 pm
content: My first try at mixing these two devices together.I have a Hantek DSO2D15 which has a function generator.I have a Matrix MPS3005H-3.The power supply has two outputs plus a separate GND connection.If I understand correctly, the outputs are floating unless I tie the black to GND. Right?The oscope has two channels plus a function generator.I need to use both channels plus the function generator on the circuit (very simple, I'm a newbie.)I also need 5V from the power supply.The function generator will supply the variable voltage for the sine wave input.Does this do the trick?I just need to GND the negative on the power supply, then everything has the same GND voltage and I can use both probes?

author: ledtester
author_rank: Super Contributor
timestamp: September 15, 2022, 05:03:50 pm
content: Attached the ground clip of one of your oscilloscope probes to the negative of the power supply.This is a more direct way of connecting the two grounds together.

author: Chris Bennett
author_rank: Newbie
timestamp: September 15, 2022, 05:18:16 pm
content: Oh, that sounds much better!
Lab power supply PS303D and powerware 9120 (700w) UPS - Page 1
Forum section: electronics / beginners

author: Hrvoje-CRO
author_rank: Contributor
timestamp: November 20, 2014, 05:24:38 pm
content: Hi again!Sometimes when i switch on my PS303 0-30V/0-3A lab PSU, UPS shows message "Bus unbalance!!!". So, is it possible and normal situation in which that power supply draws too much current in start? Due to magnetization of transformers core?Thank you!

author: con-f-use
author_rank: Unknown
timestamp: November 20, 2014, 09:08:20 pm
content: Yes, it's called inrush current.

author: SebG
author_rank: Regular Contributor
timestamp: November 21, 2014, 01:32:12 am
content: In power supplies, usually the inrush current is due to filtering capacitors, on the DC side, being charged. The capacitors would be somewhere on the order of few mF (=1000uF).David has a video where he talks about inrush current:
lab psu's - Page 1
Forum section: electronics / beginners

author: silly sausage
author_rank: Regular Contributor
timestamp: January 16, 2025, 11:25:50 am
content: I notice most variable lab power supplys are 0-30v, Why 30v and not say 50v,is there a reason or convention they all seem to be 30v max, I notice either linear or switchers are like this, Why is that so?.

author: wraper
author_rank: Unknown
timestamp: January 16, 2025, 11:45:13 am
content: Generally more than 30V is rarely needed. When you increase voltage, you need to reduce maximum current if you make PSU with the same power rating, it's a tradeoff and 30V is basically a sweet spot for general use. Unlike 30V, 50V is dangerous and needs much more precaution when used.

author: radiolistener
author_rank: Super Contributor
timestamp: January 16, 2025, 12:02:49 pm
content: 30V is classified as safe voltage for humans, higher voltage may cause serious damage to your heart and may lead even to death.As you probably know, for high-humidity environments such as showers, saunas, or swimming pools, electrical lighting operating at 36V AC is also used for the same reason - to ensure human safety.Additionally, most electronic devices are designed to operate at standard voltages such as 3.3V, 5V, 6V, 8V, 9V, 12V, 13.8V, 14.4V, 18V, and 24V. Therefore, a 30V range covers the needs of nearly all such devices with a small margin.

author: Konkedout
author_rank: Frequent Contributor
timestamp: January 16, 2025, 07:47:01 pm
content: Quote from: radiolistener on January 16, 2025, 12:02:49 pmI agree with all of the above. I happen to have an old linear regulated Chinese made bench power supply. It is 0-50V at 3 Amps. ITHINKI purchased it from MPJA many years ago. I have never opened it up, but my ears tell me that it somehow uses relays to switch transformer taps as the output voltage is varied. This would limit the power dissipation in the linear regulator. This aspect works pretty well.I do not like the current limiting characteristic as the output simply shuts down when the current limit is exceeded. You cannot use the output current limit to set it as a constant current source.Also the voltage adjustment potentiometer is noisy. But this is probably a matter of using a cheap component rather than any issue with the architecture of the power supply.
Laboratory Exercise 1: Multimeter  for beginners - Page 1
Forum section: electronics / beginners

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: May 15, 2011, 06:26:01 pm
content: I had found an very well written document, about the basics of measurements and multimeters .I did read it all , and it was an interesting read , even for me that I am 42 years old,and away of the theory about measurements , that the school class provides .And so I am suggesting it, to all who needs a good memory refresh.Or even to the ones who need to learn some basics , found only in the school class.http://www.google.gr/url?sa=t&source=web&cd=24&ved=0CC8QFjADOBQ&url=http%3A%2F%2Fwww.mit.tut.fi%2FMIT-1016%2Fmultimeter.pdf&ei=zA3QTcqNIsmeOr6lsPYM&usg=AFQjCNFyIBb0teKKtqJCTPLZcuH0HcP4zw
"Labs" for learning how to use Spectrum Analyzer - Page 1
Forum section: electronics / beginners

author: zitt
author_rank: Regular Contributor
timestamp: July 23, 2019, 10:26:32 pm
content: I'm getting old.Back in the late nineties when I was in college... Oscilloscopes and volt meters were common place. I know how to use both these instruments.I didn't major in RF design; so I didn't have any real exposure to Spectrum Analyzers.There have been more than a couple of cases in the recent year or two where a SSA would have been useful.Example: Detecting that a crystal clock is actually operating. IE no frequency shift with scope probes attached.Example: Detecting that my BlueTooth radios are actually transmitting where I think they are.Example: DC 2 DC power supply workBut I didn't have a SSA. I solved that problem and now have a CMU200 on my bench - but I've done nothing more than stick an antenna on it and verify some of the radio spectrum had a peak where my Wifi is transmitting.Is there any high school / college level "lab experiments" documented anywhere that people would recommend?I want to get more comfortable using this instrument and maybe learn what not to do. I'd even like to learn a little bit about antenna design if the advanced portions of the "lab" cover it. I'm not really interested in Youtube videos as primary source of information. I'm more interested in hands on usage of my instrument. That said; if there is "lecture" on youtube with hands on lab work "offline" that would work.

author: mindcrime
author_rank: Unknown
timestamp: July 24, 2019, 01:57:55 am
content: No hands-on "labs" per-se, but this book looks like it might be useful. It's from Keysight, but at first blush, it doesn't appear that it's specific to their instruments:http://literature.cdn.keysight.com/litweb/pdf/5952-0292.pdfSomething similar from Anritsu:https://www.naic.edu/~phil/hardware/Misc/anritsu/SpectrumAnalyzer_basis_of.pdfAnd Rohde and Schwarz have their version:https://rotorlab.tamu.edu/me459/NOTES%206%20Measuring%20with%20modern%20spectrum%20analyzers_Educational%20Note.pdfAs do Tektronix:http://engineering.case.edu/lab/circuitslab/sites/engineering.case.edu.lab.circuitslab/files/docs/Real_time_Spectrum_Analyzer_Fundamentals_-_Tektronix.pdfThis looks like it may be closer to what you're looking for:http://propagation.ece.gatech.edu/ECE4370/labs/LabSpectrumAnalzyer.pdfMaybe between all that you can piece together something useful?Outside of that, there are one of two Youtube videos that might be helpful:
LabVIEW Help Needed - Willing to Pay - Page 1
Forum section: electronics / beginners

author: fourierpwn
author_rank: Regular Contributor
timestamp: April 29, 2017, 11:48:38 am
content: Hi all,I am wanting to do some instrument control within LabVIEW. I am quite inexperienced with said program and I am struggling to wrap my head around it.I am wanting to control a FFT analyser (set frequency sweep, averaging, etc), which I have some existing code which does the job that is written in ChSciTE (very little online support for this). However, this code is on a very old laptop and all attempts at transferring it to a newer PC have been unsuccessful.Is anyone here competent with LabVIEW for instrument control to the point that they are confident that they can help me to convert said code into the LabVIEW environment? If so, I would be willing to pay for your efforts.If you are interested, please send me a PM and I can send through the existing code and we can go from there.My apologies if this thread is in the wrong forum.
LabView Software - Page 1
Forum section: electronics / beginners

author: patry017
author_rank: Newbie
timestamp: November 28, 2014, 06:04:20 am
content: HI Mr Davidwould be able to do videos on Labview TutorialsCheersRP

author: awallin
author_rank: Frequent Contributor
timestamp: November 28, 2014, 06:20:30 am
content: if you do programming tutorials for hobbyists, you can't really focus on a commercial programming language where the 'compiler'/IDE costs many keur?!?
Lambda power supply and tenma multimeter - Page 1
Forum section: electronics / beginners

author: Unknown
author_rank: Unknown
timestamp: May 26, 2013, 07:26:43 pm
content: Hi all,I don't know if I would class myself a "beginner", but I'm more of a hobbyist at the moment (a linux administrator by trade) and am building up a lab, so I guess this is as good a place as any.I picked up a Lambda LQ-534 power supply for $70 at a surplus place, works perfectly. It has a voltage and current dial. What do you think of this model, and do you think the amp/voltage measurements it gives out can be trusted?I also am considering picking up a tenma bench multimeter for repair cheap. It's a bench style. What do you think of this brand?I must confess I picked up one of those cheap chinese multimeters (a Mastech MY-62) before I watched Dave's review of cheap chinese multimeters. I can't afford much better right now, though, so I guess this will have to do. I wish I could pick up a better one but I guess that will just have to wait.Thanks, and Dave, I particularly enjoy not turning it on, and instead, taking it apart. My workbench is full of stuff I didn't turn on.Oh, and I picked up one of those Tektronix TDS-340A oscilloscopes. Any thoughts on this model? Worst case, it was cheap...

author: MasterOfNone
author_rank: Regular Contributor
timestamp: May 26, 2013, 10:30:45 pm
content: Quote from: duskglow on May 26, 2013, 07:26:43 pmTenma is basically the name Farnell uses for equipment it rebadges. The Tenma Multimeters seem to be the same as the UNI-T brand and UNI-T make some great meters for the price. One thing about the Bench Multimeters, if it has an Orange and Grey case (aka the new UNI-T bench meters) then checkout its size, because these thing are huge. But don’t worry too much because if your running out of space you can always make four legs for that baby and turn it into a dining table.

author: Unknown
author_rank: Unknown
timestamp: May 26, 2013, 10:48:05 pm
content: Cool, thanks. The multimeter I'm looking at has a bum display but I figure as multimeters go that's probably one of the easiest things to fix.It's hard kitting up a lab for cheap, but I'm learning, it's very doable as long as you don't go after the latest and greatest.Thanks for the dining table suggestion.This one doesn't have the orange case, though.
Lamp for working on photopolymer film - Page 1
Forum section: electronics / beginners

author: edmundopt
author_rank: Regular Contributor
timestamp: February 10, 2014, 02:30:43 am
content: I have lots of non etched boards, I mean, the cooper is all there but they lack the UV resist. I bought Positive 20 spray and had very good results with it, but its winter now and I tried to spray some boards inside and it is ... messy!Anyway, I have bougth this stuff :http://www.ebay.co.uk/itm/Photopolymer-Film-Photo-imageable-Dry-Film-Resist-for-etching-pcb-gravure-/261329310887?pt=UK_BOI_Electrical_Components_Supplies_ET&var=&hash=item3cd870d4a7]http://www.ebay.co.uk/itm/Photopolymer-Film-Photo-imageable-Dry-Film-Resist-for-etching-pcb-gravure-/261329310887?pt=UK_BOI_Electrical_Components_Supplies_ET&var=&hash=item3cd870d4a7]http://www.ebay.co.uk/itm/Photopolymer-Film-Photo-imageable-Dry-Film-Resist-for-etching-pcb-gravure-/261329310887?pt=UK_BOI_Electrical_Components_Supplies_ET&var=&hash=item3cd870d4a7To work with the positive 20 I use 4 white led lamps, the instructions on this one say "under yellow light or in shaded room", I suposed it's ok to use led lamps... Anyone with experience out there ?

author: sleemanj
author_rank: Super Contributor
timestamp: February 10, 2014, 04:34:19 am
content: Dry film is not that sensitive. Work under ordinary household lighting, close the curtains to keep out sunlight. That's all.See my tips:http://sparks.gogo.co.nz/dry-film-tips.pdf
lamp Touch Sensor boards comparison - Page 1
Forum section: electronics / beginners

author: iceblink
author_rank: Newbie
timestamp: February 10, 2015, 04:19:54 pm
content: Hi, hope this 1st post is ok and in the proper section.I have recently replaced a blown touch sensor in a lamp with a cheap generic model from ebay but I am a little worried that the cheap ebay replacement may not be safe. The replacement is on the left in the photo () and the old touch sensor, which blew, is on the right. The old one looks to have thicker wiring and better quality components (but it blew anyway) - can anybody advise if there are major safety issues I should be aware of. (The wire colours do not match between the two sensors, but the wiring diagrams seemed identical, just needed to switch around the colours, I can post the wiring diagrams if that would help)

author: SeanB
author_rank: Super Contributor
timestamp: February 10, 2015, 05:05:30 pm
content: Old sensor likely has only a blown triac, which is easy to replace. Likely blew with a lamp failing as well.

author: iceblink
author_rank: Newbie
timestamp: February 10, 2015, 05:18:14 pm
content: You mean that little 3-pronged black component? It has part number BT131 09 - can't find the exact part number in the uk after a quick search - I guess 09h is the same.If it's just a few pence I'll try replacing it(and yes, the sensor blew when I tried to remove an old bulb without switching off the power - duh!)

author: SeanB
author_rank: Super Contributor
timestamp: February 10, 2015, 07:06:51 pm
content: BT131 triac, A little 600V 1A triac.http://www.nxp.com/documents/data_sheet/BT131-600.pdfThe 09 is likely a manufacturer batch code. So long as when it died it did not kill the controller micro it will work with just a replacement. When it failed I guess the lamp was on all the time, or did you blow the little device open or blow a track off the board.

author: iceblink
author_rank: Newbie
timestamp: February 10, 2015, 09:04:01 pm
content: Thanks, I can get one of those for 99p, but will probably wait until the replacement fails and then try a repair. When it failed it was plugged into the power socket, but the bulb had blown, I unscrewed the bulb and there was a little spark when I did this - but i suppose it could have failed when the bulb blew, I'll never know. There is no sign of any damage on the board, I assume it is a failure of one of the more delicate components.I was wondering what the big copper coil and the large yellow cubic component were for on the older board - and that quality looking shiny blue capacitor? The components on the replacement board all look cheap in comparison, but the replacement has been working finr for over a week. (Note this touch sensor has 3 levels of brightness)
Lan filter. LFE9219C-R. What is the CT connection for? - Page 1
Forum section: electronics / beginners

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: December 16, 2020, 04:48:55 am
content: I have a intel PCI express network interface card with 4 separates NICs. I removed it from a frankenrouter during a dust-bunny cleanse.There are 4 LFE9219C-R chips. I looked at the data sheet.https://www.datasheets360.com/part/detail/lfe9219c-r/3428566239311195102/What I like to know is what the center tap is used for. I thought that you just connect the diff pairs to one side and the rj45 to the other side.?

author: m k
author_rank: Super Contributor
timestamp: December 18, 2020, 03:56:00 pm
content: I've never thought much about it eighter.It's a form of termination.Nowadays it must also support other stuff.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 18, 2020, 09:53:36 pm
content: That's not a filter, it's just a normal transformer set... don't know why they call it that. It doesn't specify any more than the standard Ethernet performance specs.The media-side CT chokes allow common mode currents (RFI, ESD, etc.) to be sunk to ground, away from the PHY. Typically a 50 ohm resistor links these to a common node, which is bypassed to ground with 1nF 1.5kV to sink ESD current.The common mode choke (CMC) in series to the transformer improves immunity. Transformers are hard to make perfectly balanced, so this helps improve that. This could be considered filtering -- but it's still not special to this part, it's quite standard in Ethernet magnetics.Why do all the chokes go on the media side?The primary side CT is usually bypassed to ground. On 10/100 PHYs, it's usually tied to +V as well. The electrical length of these windings and traces (either side of the CT) is critical, because driving one pin low causes the other pin to rise and this reaction is delayed by the electrical length (propagation delay) of that path. It only behaves as a CT transformer for pulses longer than that delay, and so this delay needs to be minimal, to achieve high baud rates.So, the media side can afford more electrical length, because it's supposed to be balanced, and any error or delay gets filtered out (to some extent; a sensitive radio receiver can still pick up what's left!). The PHY side can't afford any, so gets the simplest case (single CT winding).Tim

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: December 18, 2020, 10:42:43 pm
content: Thanks. that's a very good explanation.
language settings for oscilloscope - Page 1
Forum section: electronics / beginners

author: saminator.84
author_rank: Newbie
timestamp: May 13, 2014, 08:52:57 am
content: does anyone know how to change the language from chinese to english on a UNI-T UTD2102CEL oscilloscope? or does anyone know of a link as to where i can find out how to?

author: 128er
author_rank: Regular Contributor
timestamp: May 13, 2014, 02:58:38 pm
content: http://en.lmgtfy.com/?q=uni-t+utd2000+user+manualSecond result, maybe page 55/59.
Laplace SA3000 vs Siglent ssa3032x spectrum analyzer - Page 1
Forum section: electronics / beginners

author: Naumy
author_rank: Newbie
timestamp: January 19, 2018, 10:39:16 am
content: Hello,I am new to the field of Spectrum Analyzers. I have to test a weighing indicator for Truck scales. A local dealer has suggested us to buy a Laplace SA3000 EMC Analyzer which is quite costly. I searched and found Siglent ssa3032x spectrum analyzer for lower cost as i need to test for the conducted and radiated emissions. Can anybody tell me if Siglent analyzer would be sufficient for this job or if Laplace Analyzer is better, as I need an analyzer for pre-compliance EMC testing in my lab. I have to check everything as per the CE marking standards.Thanks

author: danadak
author_rank: Super Contributor
timestamp: January 19, 2018, 11:54:21 am
content: A general purpose spectrum analyzer is suitable for EMC. The conductedstraight forward to do, the radiated requires a calibrated antenna for thespectrum being analyzed. I used in mid 70's an HP141T to do this to pass FCCtesting. And a Singer antenna. Times have changed however so standardyou have to meet should align with analyzer specs, sensitivity, noise floor,BW.If there is complex modulation standards to meet that might require a morecapable analyzer. Or if analyzer of choice is not sensitive enough then youmay need a calibrated external amplifier.Regards, Dana.
lappy charger barrel jack - Page 1
Forum section: electronics / beginners

author: m3vuv
author_rank: Super Contributor
timestamp: February 26, 2022, 08:19:12 am
content: H all,i have a dell inspiron 1720,trouble is te wires break in the charger cable,where they enter the barrell conector,this leads to charger not beeing recognised,means it will power the laptop but wont charge the battery,is there a name for te connector so i can fit a replacement,or a way of bypassing the data center pin,ie does the lappy pull it low etc?,TIA

author: DavidAlfa
author_rank: Super Contributor
timestamp: February 26, 2022, 12:40:23 pm
content: Sure, you'll find them in ebay/Aliexpress. Ususally the most accurate search is "DC jack". Ex. "DC jack Inspiron" or "DC jack Dell".When I repaired these things, we had a many types of them, people broke them very often.In most cases, the damage was caused by those universal chargers using tip adapters, making a very bulky plug that made lot of strain onto the connector.Avoid those like walking on lava. Some completely damaged the board by ripping off part of it or burning the connector due poor connection.We sold brand/model specific compatible chargers, much cheaper but providing the same functionality and connection quality.Those customers learned the lesson and very rarely had that problem again.

author: BrokenYugo
author_rank: Super Contributor
timestamp: February 26, 2022, 09:19:15 pm
content: I usually hop on eBay and buy a pigtail to splice on, or sometimes it ends up cheaper buying a whole shock hazard/house fire grade charger just to cut the cable off.If you're really in a pinch it is possible to carve all the rubbery crap away and solder to the actual barrel part.

author: m3vuv
author_rank: Super Contributor
timestamp: February 27, 2022, 06:05:58 am
content: i cut away all the plastic/rubber and put in a new wire,it works ok now,tink i will make a mold and fill it with hot glue to support where the wires solder onto the barell.

author: m3vuv
author_rank: Super Contributor
timestamp: February 28, 2022, 04:01:07 am
content: The dc jack inspiron come up in searches as the pc end,i need the power block end!

author: m3vuv
author_rank: Super Contributor
timestamp: February 28, 2022, 04:01:57 am
content: Ie the male end!

author: tooki
author_rank: Super Contributor
timestamp: February 28, 2022, 11:22:31 pm
content: Then don’t search for “jack” (which normally means the socket — the UK is a bit odd in using “jack” or “jack plug” to mean the plug) but for “plug”…

author: mikerj
author_rank: Super Contributor
timestamp: March 01, 2022, 04:07:08 pm
content: I'm having the exact same problem, but with my father's Samsung laptop. The DC plug for this is an unusual size (5.5mmx3.0mm) and I've had no luck finding a pigtail or a solderable plug anywhere in the UK. Aliexpress list a pigtail, but don't want to wait two months for delivery so I've just ordered one of those super crappy set-your-house-on-fire Chinese chargers that I'm going to cut the cable off and splice it into the original.
lappy charger rfi - Page 1
Forum section: electronics / beginners

author: silly sausage
author_rank: Regular Contributor
timestamp: February 08, 2025, 10:51:24 am
content: My lappy 150w power adapter/charger wipes out hf signals here with s9+ of noise, whats the best way to stop it killing my swl, I have tried ferrites on the input+output wires but no change, is there another way to stop or lower the rfi it produces on hf ?.

author: CaptDon
author_rank: Super Contributor
timestamp: February 08, 2025, 02:41:44 pm
content: In the end I just got a different better built charger from my local computer rebuilder / refurbisher. You would have to get inside your charger and add all kinds of R.F. bypass capacitors and maybe ferrites and even then your wideband hash will only reduce to S5. If you have a local computer guru that hords all kinds of stuff then take your laptop and a portable AM radio to the shop and try some different voltage/current compatible chargers. Your problem is common among folks who use laptops to run RTTY or FT-8 or even SSTV/FAX/CW. Sometimes you just have to fall back on a fully charged set of batteries when an excellent RFI proofed charger is unobtainium. Cheers mate! B.T.W. ALL of my noise free chargers have the mains earth ground carried through to the return side (negative power return / shield) of the D.C. output!! Some folks here argue that such chargers don't exist blah blah blah but I can tell you that my most useful chargers are wired that way and I insist on it when I connect my laptops to my recording studio or venue sound systems.

author: temperance
author_rank: Super Contributor
timestamp: February 08, 2025, 02:52:05 pm
content: The flashlight fish in my minds aquarium don't understand much of what you wrote.The lappy probably means laptop. The S9+ maybe some phone or something. But what is swl.

author: CaptDon
author_rank: Super Contributor
timestamp: February 08, 2025, 03:16:52 pm
content: Google SWL, Short Wave Listening no, it has nothing to do with the ocean. S9+ again could Google. Signal Strength S9 is often represented as 50 microvolts at 50 ohms at the input connector of the receiver. Lappy, kind of a U.K. term for laptop.

author: temperance
author_rank: Super Contributor
timestamp: February 08, 2025, 04:41:26 pm
content: Google SWL:Société Wallonne du LogementSafe Working LoadSecurity wholesale limitedStichting Welzijn Lingewaardpage 1 to page 15 search result are mostly about safe working load. Page 18: the ScottishPower Women's Premier Leagues9+everyone knows what s9+ returns for the first 10K search results.Lappy > laptop supply, s9+,... swl, rfi. Maybe the lappy supply is disturbing the wifi or something.Not everyone is a HAM. Some are silly sausages.
lappy power brick - Page 1
Forum section: electronics / beginners

author: p.larner
author_rank: Frequent Contributor
timestamp: October 23, 2023, 06:34:07 pm
content: my lappy power brick gives s9+ of noise on most hf bands,it already has ferrites on the lead to the pc,would putting 2 shottky diodes back to back in the power lead(240v) earth wire?.

author: Thunderer
author_rank: Regular Contributor
timestamp: October 23, 2023, 11:33:39 pm
content: So, you have a HF radio that picks-up lot of noise from your SMPS.Well, if it is not picking it from your supply, it will get it from LED lights, TV SMPS, neighbors power supplies, etc. The times for clean HF reception ended like 30 years ago.In the meantime, maybe going into countryside, use more aggressive NB filters.PS: The lappy PSU has already a rectifier bridge from the mains, so adding new diodes will make a dangerous improvisation with no benefits at all.PPS: If this post is linked to the isolation transformer topic, I guarantee you will not solve any problem with isolation. You may add a common mode filter (see here some detailshttps://www.coilcraft.com/en-us/edu/series/a-guide-to-understanding-common-mode-chokes/). But, I highly doubt you will get rid of the culprit.

author: themadhippy
author_rank: Super Contributor
timestamp: October 23, 2023, 11:49:51 pm
content: QuoteAnd how good is your earthwire continuity if both diodes go open circuit?

author: p.larner
author_rank: Frequent Contributor
timestamp: October 24, 2023, 01:33:21 am
content: well ive opened the lappy psu,out dropped the can of a 25v 470uf cap,i replaced that,also removed the mains socket and fitted a fused mains filter on the top of it,this is from an old piece of test gear,the cover is now covered in aluminium tape connected to the mains earth,will test it later.
Laptop battery cell replacement with smartphone battery ? - Page 1
Forum section: electronics / beginners

author: cowboysaif
author_rank: Newbie
timestamp: July 11, 2019, 03:45:02 pm
content: Hello,I am totally inexperienced with electronics. Let me explain what i am trying to do.My laptop battery was discharging very quickly, so i thought of a battery replacement. While doing so, i investigated whether the battery cells can be replaced instead.The battery is 3220 mAh @ 11.4v.There are 4 cells in the battery, each cell has 11.93Wh @3.8VEach cell has a positive and negative terminal. There is a piece of electronics on the positive(?) terminal though. Please see the picture below.I have no idea about this things, but whats stopping me from soldering a regular 3.8v smartphone li-ion battery ?

author: capt bullshot
author_rank: Super Contributor
timestamp: July 11, 2019, 03:54:46 pm
content: Yes, one can replace individual cells in a battery (better all of them at the same time) to rescue an otherwise unobtanium or ridiculously expensive battery. Been there, done that. Wouldn't recommend you to do so for the lack of experience - it's definitely not an absolute beginners job, too many things to consider and too many things that could go wrong.BTW an 11.4V battery consists of three cells, not four.

author: Audioguru
author_rank: Super Contributor
timestamp: July 12, 2019, 01:16:45 am
content: The label on the battery says it is charged at 13.05V which is 4.35V per cell. A new kind of lithium chemistry (Si-Graphene) can be charged that high. Ordinary lithium cells (lithium cobalt-oxide 4.20V when fully charged) explode or catch on fire if they are charged that high.Your laptop probably has a charger that can charge the new battery chemistry but it would overcharge and blow up ordinary lithium batteries.Caution: There are also newer lithium batteries (lithium iron phosphate) that must be charged to 3.6V when fully charged.

author: amyk
author_rank: Super Contributor
timestamp: July 12, 2019, 02:14:31 am
content: There's apparently even 4.4V lion cells available now...