hybridfree/eevblog-posts huggingface dataset:
How to make a simple voltage measurement device - Page 1
Forum section: electronics / beginners

author: houkensjtu
author_rank: Contributor
timestamp: July 29, 2015, 12:56:26 pm
content: Hi there!I want to make a simple voltage measurement device myself which can:1. Measure a DC voltage range from 100-200V2. Have reasonable accuracy, say error less than 0.1%I thought a cheap multimeter may give me some idea so I tore down my multimeter, I expected that there would be an AD converter like chip, but the only thing I found is a single central chip(most likely a microcontroller) on the board.(you can find my photos in the attachment)Here is my question:1. What is the standard way to measure voltage in digital multimeter?2. How should I deal with the high DC voltage (because usually microcontroller can't afford that high voltage input)3. Is it better to use a seperate AD converter than using microcontroller's build-in AD converter?Thank you all!

author: Richard Crowley
author_rank: Super Contributor
timestamp: July 29, 2015, 01:57:11 pm
content: Quote from: houkensjtu on July 29, 2015, 12:56:26 pmMost lower-end DMMs have specialty chip like Intersil ICL7106. It handles everything from measurement to display-driving.QuoteSimple voltage divider. Add protection clamps (diodes, etc.) if there is danger of over-voltage.QuoteDoes the microcontroller's built-in AD converter meet your requirements?
How to make low current output for flyback transformer?? - Page 1
Forum section: electronics / beginners

author: claydioactive
author_rank: Newbie
timestamp: June 13, 2017, 09:01:44 pm
content: So Recently I have been wanting to make a Jacobs latter and I remembered I had a massive 26.5KV flyback transformer from a large crt projection television and figured It would be quite sufficient. I then had realized I had been told "If I catch you playing with lethal voltage, Ill take away all your equipment and components!". So I started thinking and remembered the overused term"its not voltage that kills its the current". So is there a way I could get a output below (Hopefully) 5 milliamps and still be able to make a good sized Jacobs latter?

author: MagicSmoker
author_rank: Super Contributor
timestamp: June 13, 2017, 09:12:01 pm
content: https://www.repairfaq.org/sam/jacobs.htm

author: Zero999
author_rank: Super Contributor
timestamp: June 13, 2017, 09:36:59 pm
content: It's a little more complex than that. The output current is not mains frequency AC so is less deadly. In any case, there's no easy way to reliably limit the current to a safe level, especially with an unknown transformer. Follow safe working practises you won't get hurt.

author: claydioactive
author_rank: Newbie
timestamp: June 13, 2017, 09:59:09 pm
content: Would It be possible to limit the input current extremely low using a current limiting resistor? And also, I have always wondered about power gain and loss from transformers. Lets say I input 10 volts 2 amps AC into a transformer and get 100 volts out. Does the amperage get converted into a higher voltage? I mean, Its impossible to gain energy in a transformer, Theres actually a loss right?

author: Zero999
author_rank: Super Contributor
timestamp: June 14, 2017, 06:37:54 am
content: Quote from: claydioactive on June 13, 2017, 09:59:09 pmOf course it's impossible to get extra energy from a transformer. In a perfect transformer, if the voltage is multiplied by 100, then the current should be divided by 100.In a real transformer, the voltage drops, as more current is drawn due to copper losses and leakage inductance. If you know the turns ratio, you could theoretically limit the current to the primary winding, therefore the current in the secondary by a factor of the turns ratio.
how to make smart doorbell like "RING" company - Page 1
Forum section: electronics / beginners

author: arpit
author_rank: Newbie
timestamp: January 14, 2021, 05:21:52 pm
content: Can anybody please help me to figure out how to make a smart doorbell, what all equipment are needed, inshort i want to make a same doorbell as like RING doorbell.I am 20 year old and does not have any electrical background but its just my startup idea and I genuinely want it to execute. please help me.Thanks in advance.

author: rstofer
author_rank: Super Contributor
timestamp: January 14, 2021, 06:13:14 pm
content: You can't possibly build one as cheap as you can buy one. However...I would use a Raspberry Pi with the Pi camera and WiFi. I'm not sure where I would get the power. If both sides of the 24VAC power are at the switch location, everything will work out fine. Otherwise, I might have to fiddle with the existing wiring.Then I would need some kind of power supply to take 24VAC and bring it down to 5VDC and not be totally inefficient. Probably some kind of switching power supply.ETA: You might try to Google for Raspberry Pi Door Camera or something similarhttps://www.bouvet.no/bouvet-deler/utbrudd/building-a-motion-activated-security-camera-with-the-raspberry-pi-zero
How to make the circut - beginner HELP - Page 1
Forum section: electronics / beginners

author: Crazyassmf
author_rank: Newbie
timestamp: February 05, 2019, 03:27:03 pm
content: Yo guys, I didnt know where exactly to put this topic, so I hope I've made the right choice.The problem goes like that: I wanted to make a led diode stripe, which works on 12V. What that basically means is that I have 12V power, and 12 led smd diodes (350mА, 1W, 3-3.4V) which I want to place in a row or next to each other just look like those house interior led stripes. But because Iam a dummy beginner, I had no idea how to do that until I found a online calculatorhttp://led.linear1.org/led.wiz, where I enter 12V Source voltage, 3V diode forward voltage, 350mA diode forward current (mA), 12 - number of LEDs in your array.I ended up with this:http://prikachi.com/images.php?images/568/9498568A.png.or the picture will be in attachements. First of all is this diagram correct? And how to make all the leds in one line not on 3 rows, how the diagram will look then? I know that I sound very silly, but if someone helps me with that I will be more than happy. Thank you in advance!!!

author: graeme.c.payne
author_rank: Newbie
timestamp: February 05, 2019, 11:19:52 pm
content: The schematic diagram (what you have) does not necessarily have any relationship to the physical layout. You can do the layout any way you want as kind as is electrically equivalent to the schematic. Visualize it with longer wires and stretched out in a row. Just make sure the connections are the same as in the schematic.Sent using Tapatalk

author: Audioguru
author_rank: Super Contributor
timestamp: February 05, 2019, 11:35:48 pm
content: The LED wizard is stupid like most of them. What if the 12V is actually a little low at 11.5V and all the LEDs are maximum at 3.4V? Then they probably will be very dim.You should use a resistor value that has 3 volts across it. Then three 3.0V LEDs with a series resistor with a value of (12V - 9V)/350mA= 8.57 ohms (use 8.2 ohms) at 2W. When the 12V is a little low and the LEDs are all 3.4V then the brightness will be only a little dimmer.
How to make this Footprint for AD - Page 1
Forum section: electronics / beginners

author: mengfei
author_rank: Regular Contributor
timestamp: June 28, 2024, 03:40:36 am
content: i have scour the net for info but it's seems i cant get no satisfaction from where i amhttps://source.z2data.com/2020/4/7/2/20/36/767/3554352/TP102.pdfi'm not sure how this Macom RF Pulse Transformer is installed on a PCB.thanks for the ideas.& this one too, thankshttps://www.st.com/resource/en/product_presentation/new-molded-module-for-industrial-power-applications.pdfSB49W65M5AG

author: xvr
author_rank: Frequent Contributor
timestamp: June 28, 2024, 11:00:36 am
content: QuoteYou should manually bend its pins before soldering to PCB.https://matr.com/lead-forming/

author: Doctorandus_P
author_rank: Super Contributor
timestamp: June 28, 2024, 01:29:28 pm
content: I see a few options here. Most common is lead forming as xvr already mentioned (either in THT or SMT form). The other option is to route a hole in the PCB and put the thing in the hole.

author: mengfei
author_rank: Regular Contributor
timestamp: July 01, 2024, 12:48:10 am
content: thanks guys, will look into that, i just wished i could see one that is actually mounted either in PCB or off PCB
how to make this work on my win 11 lappy - Page 1
Forum section: electronics / beginners

author: silly sausage
author_rank: Regular Contributor
timestamp: January 20, 2025, 08:53:20 pm
content: I have this sdr from aliiexpress, any idea how i can use it on my win 11 lappy,ie drivers+ programs needed etc ? thanks.

author: coromonadalix
author_rank: Super Contributor
timestamp: January 21, 2025, 01:38:38 am
content: https://groups.google.com/g/gqrx/c/uf8fYPbcNnQhttps://www.sdrplay.com/sdruno/
How to manage custom HXTAL define in Keil for GD32f4xx.h [Solved] - Page 1
Forum section: electronics / beginners

author: seabea
author_rank: Newbie
timestamp: February 02, 2022, 12:37:56 pm
content: Hello,i have a application ported from Stm32 to GigaDevice32.Now i have left one problem with the HXTAL core clock which on our board is 25 Mhz but by default it is set to 8 Mhz.I'd like to use the SystemCoreClockUpdate function but this function has the define set to 8 Mhz.Since the gd32f4xx.h and the hal sources are writeprotected in the directory C:\Keil_v5\ARM\PACK\GigaDevice\GD32F4xx_DFP\2.0.0\Device\F4XX\Include\i don't see a proper way how to set this define to a custom value.I know from other libraries that there is prepared a header file to be defined by the customer, however the gd32 hal does not seem to have prepared such a custom config header.The header's are added to the project and managed automatically by the Runtime-Environment Manager Dialog of the development-environment (Keil). I guess it is not a good idea, to just copy all the source files into the project directory under source code managment?Does somebody know how this is intended to be used?

author: seabea
author_rank: Newbie
timestamp: February 02, 2022, 01:04:24 pm
content: Ah.... I have a solution. I did not know it is possible to assign a value to project's global defines but it is.So one can just define the HXTAL_VALUE=25000000 in the project settings...That was too easy..
How to measure 5V & 12V amps used on ATX PSU? - Page 1
Forum section: electronics / beginners

author: rthorntn
author_rank: Frequent Contributor
timestamp: July 11, 2021, 11:03:28 pm
content: Hi,Has anyone seen a good way to measure 5V & 12V amps used on ATX PSU, I'm using a bunch of 5V drives and I'm worried that I could exceed the 150W I have on the 5V line?I just bought TECPEL CA-60, are these any good for DC amperages, I powered it on and tried it briefly on the +5V conductor (U1272 set to mVA) and it didn't do much?If it should work, would I use it with a DMM (Agilent U1272A or EEVBlog 121GW), or should I use an oscilloscope (Rigol DS1102E or Tek 2465B)?Thanks.Richard

author: rstofer
author_rank: Super Contributor
timestamp: July 11, 2021, 11:49:23 pm
content: If you want to see what the waveshape looks like, connect it to a scope. Ordinarily, you'll just want the value and a DMM is the tool to use.On the high end, a HDD takes 9W of +12 & +5 combined. It's going to take a lot of HDDs to come anywhere near 150W.https://www.buildcomputers.net/power-consumption-of-pc-components.htmlOn the higher scale, 1mV<=>100mA, if you are measuring 2A, you would expect 20 mV. On the lower scale, 1mV<=>10mA, you would expect 200mV.

author: rthorntn
author_rank: Frequent Contributor
timestamp: July 12, 2021, 12:02:42 am
content: The drives I have (on spinup) are 0.75A at 5V so 3.75W.I have 48 of them...180W if they all spinup at the same time.

author: amyk
author_rank: Super Contributor
timestamp: July 12, 2021, 12:36:27 am
content: There's usually a jumper for "staggered spinup" setting, which you should enable if you have that many.On the other hand, unless your PSU is rated 150W "peak" instead of continuous, a brief 180W peak is unlikely to be a problem.

author: rthorntn
author_rank: Frequent Contributor
timestamp: July 12, 2021, 12:41:35 am
content: Thanks, 5V "Max" load 30A

author: JustMeHere
author_rank: Frequent Contributor
timestamp: July 13, 2021, 04:20:43 am
content: Run lm_sensors. You should be able to monitor the voltages via the OS.

author: JustMeHere
author_rank: Frequent Contributor
timestamp: July 13, 2021, 04:26:54 am
content: And seeing you have 48 drives, cooling is a must. I've learned that the hard way.

author: rthorntn
author_rank: Frequent Contributor
timestamp: July 13, 2021, 04:50:16 am
content: Thanks, I'm using a seperate PSU for the drives, its not powering a PC and so no lmsensors I'm afraid.Yeah, I have 3x120mm fast fans blowing on the drives, maybe overkill for winter here in Australia, I'm not actually sure heat is an issue with these drives, read average for each drive is 1.9W, they only do light reads, so worst case is about 90W for 48 drives. I feel like the metal JBOD chassis could easily dissipate 45W.

author: Monkeh
author_rank: Super Contributor
timestamp: July 13, 2021, 04:56:18 am
content: Quote from: JustMeHere on July 13, 2021, 04:20:43 amSeeing as no motherboard manufacturer in the world documents the input configuration of their hardware monitors, what makes you think that will work?
How to measure Allan deviation - Page 1
Forum section: electronics / beginners

author: Mrt12
author_rank: Regular Contributor
timestamp: February 16, 2018, 11:55:43 am
content: Hi,I have a GPS frequency standard and would like to use it as reference oscillator to measure the Allan deviation of another GPSDO I made by myself. Both oscillators run at 10 MHz.I have a HP 5316A as well as a HP 5335A counter, both can be used as time interval counters.So far I have found out that I should divide down both of my oscillators to 1 Hz and then use these two signals as start and stop for the TIC.However, from the TIC measurements, how do I find out the ADEV?

author: edpalmer42
author_rank: Super Contributor
timestamp: February 16, 2018, 04:11:08 pm
content: You need to get a program that does the calculations for you. I know that sounds a little silly, but it's the truth. The ones I know of are, in no particular order: Stable32, Timelab, Plotter, Alavar, Allantools. They're all free.Stable32 is the 'gold standard'. It used to be commercial, but as of Jan. 1, it's free.Timelab is the one I use most. It can gather data directly from many counters or it can use datafiles.Plotter is a nice program, but it isn't maintained anymore. The author passed away a few years ago.Each program has it's own strengths, weaknesses and quirks. Try them all and see what you like.Edit: Argh! I forgot that Lady Heather also does ADev. Sorry Pyro!Ed
How to measure an common collector's output impedance? - Page 1
Forum section: electronics / beginners

author: j1432
author_rank: Newbie
timestamp: March 23, 2014, 09:16:09 pm
content: Hi folks,I'm trying to learn a thing or two about electronics. Right now I am fooling around with common collector circuits. I know how to calculate the theoretical value for the output impedance of a common collector circuit but am stumped about how to actually measure the output impedance of a circuit that I have actually built. All of the references that I have found online say that I should first measure the output voltage with no load and then put a load on it that adjusts the output voltage to half of the original voltage. That resistance would be my output resistance.That strategy doesn't seem to work with a common collector circuit though. The behavior that I am seeing is that the common collector circuit will maintain its output voltage no matter what load I put on it until I reach a point where the circuit just can't keep up. At that point the bottom of my waveform starts to be clipped. If I go farther, the clipping level moves farther up the waveform but the non-clipped part of the waveform does not distort at all.So what should I do to measure my output impedance?Thanks in advance.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 23, 2014, 10:10:36 pm
content: "Half" is good if it's a linear (resistor, inductor, capacitor) network. You'll have a hard time doing that here, especially at DC, as Ebers-Moll says r_e is inverse exponential with i_c!So, you can AC-couple a small signal instead, perhaps 20mVpp. Use a 50 ohm function generator source, at say 1kHz, a nice large capacitor (with much less than 50 ohms reactance at 1kHz -- 47uF or more), and connect the emitter to the function generator through the capacitor in series. Adjust FG amplitude until you measure 10-20mV at the emitter. Disconnect cap and measure FG amplitude. Now you can set up the equations for a voltage divider, with the FG's source impedance and the emitter's load impedance, and solve for r_e.You can do the same setup in a SPICE simulator, but the signal level isn't important if you perform an AC Small Signal Analysis: in that mode, the simulator sets up the circuit as if all AC signals are "small", so you won't see nonlinearities.Tim

author: j1432
author_rank: Newbie
timestamp: March 24, 2014, 04:14:48 am
content: Thanks!
How to measure attenuation on a digital scope - Page 1
Forum section: electronics / beginners

author: Aeternam
author_rank: Unknown
timestamp: June 22, 2016, 08:54:51 am
content: Hey gang,Quick question: how do you measure the attenuation, in %, of two signals on a digital scope? See attached image: I'd like it to tell me that channel 1 is attenuated blah % in regard to channel 4.Any ideas? (Yes I tried to RTFM but it's not all that clear, at least to me)

author: Rerouter
author_rank: Super Contributor
timestamp: June 22, 2016, 09:07:10 am
content: as the 2 signals are in phase, see if it has a math function, A pk2pk - B pk2pk / Apk2pk (peak to peak)

author: Mechatrommer
author_rank: Super Contributor
timestamp: June 22, 2016, 12:08:45 pm
content: since your reference is CH4, so CH4 is the divisor...((2.5 - 2) / 2.5) * 100 = 20% attenuated.

author: Aeternam
author_rank: Unknown
timestamp: June 25, 2016, 10:53:10 am
content: Quote from: Mechatrommer on June 22, 2016, 12:08:45 pmOf course. I should have been able to figure this out by myself.Thanks!Also I found that my scope has a built in function to do this, it's called "Ratio Y".
How to measure current draw of a brushed DC motor? - Page 1
Forum section: electronics / beginners

author: BlackICE
author_rank: Regular Contributor
timestamp: February 16, 2024, 08:46:02 am
content: I have a brushed DC motor that is claimed to be 350W connected to a 600w 13.5V SMPS. I tried to measure the current draw using a oscilloscope and Hantek CC650 DC clamp probe. That show a lot of high frequency noise. So I tried measuring the voltage drop over a 0.00171 shunt that I had. That also proved to have a lot of noise. The noise readings mask out any useful measurements. I used another handheld DC clamp meter that maxs out at 20A. That one did read some values before displaying overload.I found info like this on the web saying to add 10-100 nf caps across the brushes and both brushes to GND. Will this really work? What are the best values to use for the caps? If it won't likely work I don't want to tear the machine apart to try.https://forum.arduino.cc/t/measuring-noisy-dc-motor-currents/638872/6

author: Benta
author_rank: Super Contributor
timestamp: February 16, 2024, 11:16:29 am
content: Those caps are pretty much mandatory for small brushed DC motors.They remove RF noise stemming from commutation and brush fire. The risk is high that radio communication can be disturbed ifyou don't mount them.I normally use 100 nF directly across the poles and 2 x 22 nF from each pole to the motor case.

author: beanflying
author_rank: Super Contributor
timestamp: February 16, 2024, 11:25:42 am
content: Depends on the actual motor you are using but in days gone by we used to use a bunch of Mabuchi 540 sized motors for earlier R/C electric aircraft. At 6 or 7 cells (circa 7-8V fully loaded) and 20-25 amps the sparking wasn't to bad but push that to 12 and it became horrid. Typically we ran three Caps, the two lower ones to the can and the third between the terminals to reduce it. We did also run more upmarket larger Can brushed motors to around 30V and 50-60A but they were a very different beast in price and build quality, still used a similar capacitor filter on the backend as the smaller ones.Are you running a filter on your CRO input? If not a lot of the high frequency hash will also be coming from your supply in your readings.
How to measure current of pulsed damped sinusoidal wave? - Page 1
Forum section: electronics / beginners

author: nsled
author_rank: Contributor
timestamp: October 16, 2023, 02:59:46 am
content: Can I measure a sinusoidal pulse with a shunt resistor and oscilloscope? Do I require a special shunt to deal with the quick polarity changes?I've been looking for "high frequency shunt resistor" amounst other terms but I'm not really coming up with anything. From what I've been reading the resistor must have as close to zero inductance as possible.Pulse out of transformer in the range of about 100v @ 10kHz.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 16, 2023, 03:02:50 am
content: Yes?10kHz doesn't need particularly low ESL, you can use almost anything for that. If you have sudden changes or harmonics, that's another matter. You can also compensate an R+L shunt with an R+C lowpass filter, where the time constants match.Note the oscilloscope requires a common-ground signal, or must be floated (preferably a portable battery-powered scope, or a fancy kind with isolated channels). Common mode errors are the most common cause of spooky bouncing signals seen most anywhere in a circuit.Tim

author: TimFox
author_rank: Super Contributor
timestamp: October 16, 2023, 03:32:27 am
content: The posted image came out total black.Do you want to measure current, rather than voltage, out of the transformer?If so, what current range do you need to measure?
how to test leaking capacitors using DMMs? - Page 1
Forum section: electronics / beginners

author: elex_enthusiast
author_rank: Regular Contributor
timestamp: November 07, 2013, 01:09:23 pm
content: hi there,im quite confused on how to test leaking capacitors using my DMM..i used to determine leaking capacitors using an analog multimeter using resistance function but i have no idea how to perform such test using a digital meter.....please give me hints..any tips would be greatly appreciated...

author: Anks
author_rank: Frequent Contributor
timestamp: November 07, 2013, 02:47:35 pm
content: Are you referring to coupling caps leaking DC?

author: Dave
author_rank: Super Contributor
timestamp: November 07, 2013, 02:53:08 pm
content: Connect the DMM in series with your charged capacitor and connect both to that same voltage you charged your cap to.The DMM has to be set to DC voltage. By knowing the input resistance of your DMM and by reading the voltage on it when the circuit settles, you know the leakage current through you cap.

author: robrenz
author_rank: Super Contributor
timestamp: November 07, 2013, 02:59:57 pm
content: Why not just use the same setup with the DMM in current mode measuring leakage current directly?

author: Dave
author_rank: Super Contributor
timestamp: November 07, 2013, 03:09:06 pm
content: Silly me, I just assumed his meter wasn't capable of measuring currents that low, because he was asking the question.

author: mos6502
author_rank: Frequent Contributor
timestamp: November 07, 2013, 07:31:26 pm
content: 1. Apply a voltage to the cap (a 9v battery is handy for this) and measure the current. You probably need a uA range for this.2. Use the resistance mode. As soon as you touch the probes to the cap terminals, you should see the resistance become very low and then slowly increase into the single digit megaohm range. If your meter shows a low resistance value the cap is leaky.
how to measure low resistances accurately -tutorial-  - Page 1
Forum section: electronics / beginners

author: ali6x944
author_rank: Frequent Contributor
timestamp: January 30, 2016, 03:45:44 pm
content: hello everybody,i found this really nifty trick in the form to measure low resistances accurately with a multimeter, it's called 4-wire measurement or Kelvin sensing, this will be a summery for that, check it first .Here:https://www.eevblog.com/forum/testgear/question-11059a-kelvin-probe-set/msg821592/#msg821592it is basically a will known value current source that has also known voltage -low voltage like 2v would be great- connected in series to the resistance you want to measure, and a multimeter connected in parallel to the resister , the meter should be set to the dc voltage measuring rang , it should be ideally set to the mili or micro volt set, but mili volt set work for most time, now measure the voltage drop across the resister.now it becomes straight forward ohms law:IR=VSO,V/I=Rand because we know the current flow through the resister and we measured the voltage drop across the resister, we use the equation above to get the resistance.soexample:

author: Brumby
author_rank: Unknown
timestamp: January 30, 2016, 03:54:10 pm
content: It's a very well known measurement technique. There's been a discussion on getting Kelvin probes somewhere here recently....Here:https://www.eevblog.com/forum/testgear/question-11059a-kelvin-probe-set/msg821592/#msg821592

author: ali6x944
author_rank: Frequent Contributor
timestamp: January 30, 2016, 03:58:30 pm
content: OH...this is just a summery for that.thanks man for noticing me

author: Brumby
author_rank: Unknown
timestamp: January 30, 2016, 04:12:56 pm
content: It's part of the broader subject of remote sensing.Precision power supplies, for example, will have a set of 'sense' wires that you connect to the device under test (DUT) which detect the actual voltage at that point, rather than internally. This bypasses the problem of the voltage drop in the leads from the power supply.

author: ali6x944
author_rank: Frequent Contributor
timestamp: January 30, 2016, 04:44:34 pm
content: wow! that is amazing! i didn't know that, thanks manbut i was thinking how to use an op amp to sense the voltage instead of a multimeter?

author: uncle_bob
author_rank: Unknown
timestamp: January 30, 2016, 05:50:01 pm
content: HiOne caution it a "tutorial" sense:The order of lead attach to the load is quite important in a Kelvin setup. The isolation of the leads is a critical part of all this. The "assumptions" include cool stuff like zero current in the sense leads and zero voltage delta between the load and the sense point.-----If you go the sense lead on the power supply route - be careful there as well. A fully isolated sense lead (like I just recommended above) is *not* a good idea on a power supply. There you want some sort of protection so the supply does not go nuts if a connection breaks.Bob

author: ali6x944
author_rank: Frequent Contributor
timestamp: January 31, 2016, 05:26:50 pm
content: thanks uncle_bob
How to measure power in watts in a power supply with current limiting? - Page 1
Forum section: electronics / beginners

author: skillz21
author_rank: Frequent Contributor
timestamp: November 05, 2018, 12:13:37 pm
content: Have a look at this situation. I have a variable power supply connected to an AC-DC power supply which is rated for 20V 3A, or 60 watts. Now on my variable power supply, I set the voltage to 6 volts and current limit to 10 amps, and I put on a load that draws this amount of power. Now at this point, the current limiting would kick in, which drops the voltage down to somewhere near 100ma. In this situation, how much power would the variable supply be drawing from the main one? Would it still be 60 watts? (give or take a bit for power loss)

author: Zero999
author_rank: Super Contributor
timestamp: November 05, 2018, 12:26:03 pm
content: You haven't provided enough information to answer the question. Is it a switched mode or linear power supply?You also seem to have confused Volts with Amps.

author: skillz21
author_rank: Frequent Contributor
timestamp: November 05, 2018, 10:03:18 pm
content: The main PSU is a laptop power brick, and the board I'm asking about is a switching power supply (a buck-boost DC to DC converter).

author: ArthurDent
author_rank: Super Contributor
timestamp: November 06, 2018, 12:16:03 am
content: You have 60 watts input times the conversion efficiency so you won't get 60 watts out. More realistic you could get 6 VDC at 9 A max, not 10.

author: malagas_on_fire
author_rank: Frequent Contributor
timestamp: November 06, 2018, 12:27:28 am
content: Plus the losses in heat, depending on the load applied ., cable length, section, when power delivering is max out.
How to measure s-param of a device with Z0 other than 50 ohms  - Page 1
Forum section: electronics / beginners

author: Ayush.Paudel@cllnk.com
author_rank: Newbie
timestamp: May 16, 2025, 05:17:15 pm
content: Hi all,I am trying to measure some 3M PCIe flex cable with characteristic differential impedance of 85 ohms. When I plug it in the TDR, I can see the impedance is centered around 85 ohms but my insertion loss and return loss are not good. My understanding is that the VNA doesn't understand what numerical impedance is but maps it using four reference points (open, short, load, matched). The "load" given by the eCal module is 50 ohms (100 ohms differential). So if that is the case, wouldn't the system see any impedance other than 100 as mismatched? If this is the case, how can we measure the s-parameters of the 85 ohm DUT?I have tried changing the system impedance (Z0) in the PNA, but it doesn't have any effect on the s parameters. We have the Agilent PNA-X and a Agilent 50-ohms eCal kit (0-70 GHZ).If you say create your own SOLT or TRL calibration kit, how do terminate the load since soldering wouldn't work well at up to 67 GHz. Thank you in advance.

author: radiolistener
author_rank: Super Contributor
timestamp: May 16, 2025, 05:47:40 pm
content: From an impedance standpoint, yes - any mismatch from the system reference impedance Z0 will cause reflections. However, it's important to understand that the magnitude of those reflections depends on how far the DUT impedance deviates from Z0. A small mismatch results in relatively minor reflections.That said, impedance mismatch is only one source of signal degradation. Even a perfectly matched cable can exhibit insertion and return loss due to conductor losses, dielectric absorption, and radiation losses - especially at high frequencies and in flexible cable constructions. So it's entirely expected that a real-world cable will show higher losses than an ideal, lossless transmission line with the same characteristic impedance.It’s also important to note that when measuring a device with a characteristic impedance different from the VNA impedance (in your case 50 Ω), the measurement uncertainty can increase due to mismatch errors. However, in practice, the difference between 50 Ω and 85 Ω is relatively modest, so the impact on measurement accuracy is generally minor and may not be a significant concern
How to Measure Static Electricity? - Page 1
Forum section: electronics / beginners

author: MistaMun
author_rank: Contributor
timestamp: September 10, 2015, 11:34:14 pm
content: Hi!Right now, I am trying to make "something" that creates enough static electricity to pick on small molecules with negative charge. So in retrospect, I thought rubbing some fur on the PVC piping might be the best way to start out to learn the concept of static electricity.So the question, how do I measure what polarity the PVC pipe is charged to and how much it is charged? As I said, the small particle that I am trying to collect has negative charge and I need a way to make sure the charge on the PVC piping is always going to be positive.

author: IanB
author_rank: Super Contributor
timestamp: September 11, 2015, 12:30:47 am
content: Quote from: MistaMun on September 10, 2015, 11:34:14 pmThe sign of the charge you get depends on the two things you rub together. For example if you rub wool on glass the glass will end up with a positive charge. If you rub wool on rubber the rubber will end up with a negative charge.(If you rub fur on PVC piping the piping will get a negative charge.)You can discover the sign of an unknown charge by using a known charge. Like charges repel, unlike charges attract. However, a charged item will attract an uncharged item, so using repulsion is probably the best choice.Measuring the amount of charge will be very difficult since the amount of charge is very small.http://esdsystems.descoindustries.com/whitepapers/wp_Tribocharging.html

author: Mr.B
author_rank: Unknown
timestamp: September 11, 2015, 12:52:40 am
content: Dave uses a Surface DC Voltmeter inhttps://www.eevblog.com/forum/blog/eevblog-768-cordless-anti-static-wristbands-busted!/to measure the static charge.I don't know if it will do the job...

author: MistaMun
author_rank: Contributor
timestamp: September 11, 2015, 12:58:54 am
content: Quote from: Mr.B on September 11, 2015, 12:52:40 amSo in the lab, I can use these Vernir LabQuest charge meters.http://www.vernier.com/products/sensors/crg-bta/Will they do the job? They aren't the best equipment but for my purpose of finding the polarity, would this be ok or is this device irrelevant of what I am trying to find?

author: IanB
author_rank: Super Contributor
timestamp: September 11, 2015, 01:26:41 am
content: Quote from: MistaMun on September 10, 2015, 11:34:14 pmQuote from: MistaMun on September 11, 2015, 12:58:54 amIf you check out the link I provided you will find that the charge on the surface of a PVC pipe is always going to be negative.To get a surface with a positive charge you will need to use glass, acetate or nylon.

author: flynwill
author_rank: Regular Contributor
timestamp: September 11, 2015, 04:13:35 am
content: You might build one of these:http://amasci.com/emotor/chargdet.htmlNot particularly quantitative, but simple to build and can easily detect static fields (and deduce their polarity).
How to measure the current of a PWM signal? - Page 1
Forum section: electronics / beginners

author: owin
author_rank: Newbie
timestamp: September 19, 2023, 01:59:54 am
content: Let's say I have 12v at 1000Hz and 50% duty. How would one measure the output current?Would i receive an accurate reading if I hook it through a clamp multimeter? how should that reading be interpreted?I mean if it says 10A, does this mean its a pulsed 10A current, or that 10A is the average thus its actually pulsed 20A?

author: WattsThat
author_rank: Frequent Contributor
timestamp: September 19, 2023, 03:02:07 am
content: Yes, it is 10 amps, there is no other interpretation. The power changes with the duty cycle but not the amps that flow when on.A clamp on ammeter may not give an accurate reading at 1000 Hz, you’d have to know the frequency response of the measurement device to state measurement accuracy.

author: DavidAlfa
author_rank: Super Contributor
timestamp: September 19, 2023, 04:04:53 am
content: You'd need a true RMS dmm, others might measure peak, average... go figure.

author: bdunham7
author_rank: Super Contributor
timestamp: September 19, 2023, 04:20:49 am
content: Most current clamps and clamp meters aren't going to do what you want here. You'll also need to decide whether you want to measure the average current or TRMS--it matters depending on what you are doing. If you are charging a battery, you'd be interested in the average current. If you are heating something, you want to know the RMS current. Once you've decided, you can decide on an appropriate metering setup that will give you what you want.You'll need a DC-capable current clamp with a 10kHz or higher bandwidth to get a reasonable result. Then, if you want TRMS, you'll need a meter with a TRMS AC+DC function (not very common), otherwise for average DC you'll need a meter with a reasonably good AC current BW so that you know that you aren't losing too much in the shunt and input circuitry. A DSO is actually a pretty good substitute for a DMM in this case if you can live with 1-2% accuracy.
How to measure unity gain frequency in unity fb configuration? - Page 1
Forum section: electronics / beginners

author: kankanas
author_rank: Contributor
timestamp: July 04, 2020, 12:46:48 pm
content: Hello,My query is related to the circuit configuration needed to check unity gain frequency of an opamp. I tried to find and verify(from datasheet) the unity gain frequency of an OPAMP by putting it in inverting configuration with a gain of 20 and then with noninverting configuration with 31 and with another gain so far in these two configurations. Mostly it validates with the datasheet.Now the query is, is it possible to measure the unity gain frequency with buffer configuration(i.e ideal unity feedback configuration)?As in the unity feedback case, the maximum gain starts itself from 0dB, remain flats up to certain frequency, and then attenuate. Which location of frequency should we consider to actually refer it as unity gain frequency?Thanks in Advance.KS
How to measure  - Page 1
Forum section: electronics / beginners

author: Jane
author_rank: Frequent Contributor
timestamp: November 21, 2015, 09:20:26 pm
content: I need to measure pressure in a device - see the attached picture of that device .The clamp is used to move the bar up and down.Is it possible?Thank you

author: MagicSmoker
author_rank: Super Contributor
timestamp: November 21, 2015, 09:28:07 pm
content: A strain gauge is the first thing that comes to mind. [edit - more specifically, a "load cell"]P.S. - try to use a more descriptive subject title in the future. Just adding one more word to this one - pressure - would attract more attention, I suspect.

author: tggzzz
author_rank: Super Contributor
timestamp: November 21, 2015, 09:38:06 pm
content: Pull the lever with an old fashioned mechanical spring balance, and measure the force. Knowing the mechanical advantage in the linkage, you know the force on the plate. Knowing the area over which that force is exerted, you know the pressure.Or, depending on the details of what is being compressed, you could stick a balloon under the plate and measure the air pressure, or search catalogues for load cells and pressure sensors.
How to model transformer in KiCad 9.0 for SPICE simulation - Page 1
Forum section: electronics / beginners

author: jj5
author_rank: Unknown
timestamp: September 03, 2025, 11:04:22 am
content: Hi there. I have a project lab like the one shown below and I want to model the transformer it uses in KiCad 9.0 for SPICE simulation. Can someone please tell me which symbol and settings should I use for that? I'm not sure what the specs of this "transformer" are. It seems to only have a primary winding with a center tap and no secondary, is that right? I used my LCR meter to test the inductance and I got these results:Left (18) to Center (19) = 960 mHCenter (19) to Right (20) = 960 mHLeft (18) to Right (20) = 3.6 H

author: ahsrabrifat
author_rank: Regular Contributor
timestamp: September 03, 2025, 03:01:53 pm
content: Place two standard Inductor symbols (place them so you can clearly name them L1 and L2).Connect them like this:Left node — L1 — Center node — L2 — Right node.

author: jj5
author_rank: Unknown
timestamp: September 03, 2025, 03:12:19 pm
content: Thank you! I also added a line for mutual inductance:K1 L1 L2 0.98

author: radiolistener
author_rank: Super Contributor
timestamp: September 04, 2025, 05:17:26 am
content: Quote from: jj5 on September 03, 2025, 11:04:22 amYes, you also neet to add coupling between inductors.But LC measurements depends on frequency, so it's better to load s2p file taken with VNA for better simulation
How to mount heatsink on GBPC-package rectifier - Page 1
Forum section: electronics / beginners

author: seb1982
author_rank: Regular Contributor
timestamp: June 16, 2013, 02:43:11 am
content: Hi all!I'm about to make a homebrew prototype PCB for something which starts by rectifying AC from a mains transformer. The bridge rectifiers I've got are these GBPC-W packaged ones from RS:http://docs-europe.electrocomponents.com/webdocs/0dad/0900766b80dadbc1.pdf(<-- link to .pdf datasheet)There'll be a max current of 3 Amps through it, and I'm probably going to have to have a fan inside the enclosure anyway, so I was hoping to get away with keeping it mounted on the PCB, with its own heatsink on top. My question is: how do I mount it best on the PCB with the heatsink?I note from the datasheet that it has a hole for a #10 imperial screw, which seems to be as near as dammit 5mm. Should this screw "bite" into the sides of the hole in the rectifier, or fit through it easily?Also, should the screw be a self-tapper and actually screw through the heatsink & rectifier into a pilot hole in the FR4 PCB, or would this stress and shatter the PCB? Should it pass easily through the PCB and then be tightened with a nut on the bottom?As you can see, I've no idea, so any help would be greatly appreciated! I was just planning to use a finned heatsink with some compound. Also, if anyone happens to be able to recommend a heatsink from RS for this purpose, that'd be great too, but I'm sure I can find something anyway.Thanks ever so much for your help.

author: mariush
author_rank: Super Contributor
timestamp: June 16, 2013, 03:12:42 am
content: Technically, for 3A those don't require heatsink... look at the graph on second page. Especially with a fan moving air through the case, the rectifier shouldn't heat that much.But anyway, the diameter is 5.08mmDepending on heatsink i'd just use a 3-5mm screw (with maybe washers on both sides and locking washer on the heatsink side) and I'd use some regular thermal paste/grease between the heatsink.These look nice if you'd use some adhesive tape to glue them to the rectifier:http://uk.rs-online.com/web/p/heatsinks/5040700/I'd probably use something like this (if i were to be forced to get from rs) :http://uk.rs-online.com/web/p/heatsinks/0402951/- it's 19x22 mm , so fits within the footprint of the rectifier, hole pretty much in the center (4mm diameter)

author: seb1982
author_rank: Regular Contributor
timestamp: June 17, 2013, 12:32:50 pm
content: Apologies for not replying sooner - I suddenly came down with a rather nasty stomach bug!Thank you so much for that comprehensive answer - lots of very useful thoughts there, and I really appreciate it.Thanks.

author: madires
author_rank: Super Contributor
timestamp: June 17, 2013, 01:16:58 pm
content: For vertical mounting there are heatsinks with two studs (to be soldered on the bottom layer) or two mounting holes (or the profile provides some places to force a self-tapper in). In any case use the PCB more like a washer, i.e. if you're using self-tappers you need something solid on the other side of the PCB.
How to mount Li-Po battery on PCB? - Page 1
Forum section: electronics / beginners

author: VEGETA
author_rank: Super Contributor
timestamp: May 11, 2025, 09:47:52 pm
content: Hello,I am looking into using a square shaped Li-Po battery in one of my upcoming projects which its PCB is so crammed.I searched for a special connector to mount these type of square or rectangle batteries but could not.My current solution is 3D printing but I'd like to avoid it if possible. Maybe a retaining clip or so can be used.for your kind help.thanks

author: TERRA Operative
author_rank: Super Contributor
timestamp: May 11, 2025, 11:06:34 pm
content: I have usually seen double-sided tape used to hold the prismatic pouch-type lithium batteries in place, from cheap ebay stuff, all the way to mobile phones.

author: VEGETA
author_rank: Super Contributor
timestamp: May 12, 2025, 06:05:04 am
content: Quote from: TERRA Operative on May 11, 2025, 11:06:34 pmIs there any reliable method the PCB assembler can do?The user is the one who will purchase the battery and install it, therefore the assembler won't. Is there a standard known way the pcb makers and assemblers use? like 3M tape pasted but not peeled? I am trying my imagination here.I do not use modern laptop or phone so I did not see the battery inside. but it is good to know from those who experienced this.

author: TERRA Operative
author_rank: Super Contributor
timestamp: May 12, 2025, 10:58:41 pm
content: Best thing is to just ask the PCB assembler. I'm sure they can handle putting some double sided tape on the PCB. You can even put an outline in the silkscreen to show the exact location.
How to move forward in electronics - Page 1
Forum section: electronics / beginners

author: Abayomi
author_rank: Contributor
timestamp: May 14, 2016, 09:25:26 pm
content: Hi! I already know the basics of electronics, I can solder, identify component, test component, build some simple projects provided there circuit diagram is correct. The only thing bothering me now is how can I develop my own circuit diagram to work for a specific purpose, I just don't want to be a copy cat building on someone else's circuit diagram. I want an Expert, experienced answer please.

author: tggzzz
author_rank: Super Contributor
timestamp: May 14, 2016, 09:38:25 pm
content: Everybody builds on other people's circuits. Some improve them, some use them in new ways, some use them to do something useful.

author: rstofer
author_rank: Super Contributor
timestamp: May 14, 2016, 09:53:26 pm
content: At some point, you move from "technician" to "engineer". Usually after a boat load of math. This is especially true if you want to work with analog signals and tuned circuits or, especially, filters.There is a very nice analog circuits course over at Digilent Inc. "Real Analog" here:https://learn.digilentinc.com/classroom/There some algebra going on in the first several sessions - pretty mild stuff.There are thousands of tutorial on the Internet. Pick a topic and somebody has a tutorial.If you want more in-depth opinions, you need to describe which part of the electronics sand box interests you. There's a world of difference between microwave communications and FPGA design.

author: rstofer
author_rank: Super Contributor
timestamp: May 15, 2016, 01:17:23 am
content: There have been some threads lately about "The Art of Electronics" and "Learning The Art of Electronics" books. These are excellent sources of information although I have neither.I'm not certain the "Learning ..." is the same edition as "The Art ...". It may be for the original version. Check it out."Learning ..." is all about building stuff and analyzing the results.Search this forum for more information.