hybridfree/eevblog-posts huggingface dataset:
How to attempt a laptop power control and supply, board level issue?  - Page 1
Forum section: electronics / beginners

author: mrme01
author_rank: Newbie
timestamp: November 04, 2018, 04:02:58 am
content: Hi folks, soon I hope to attempt a repair on a HP laptop, but I could do with some pointers, I have a soldering station, a pile of dead laptop boards from previous generations and a rather cheap, but working DMM, and the service manual PDF.Where should I start with where to look?I retired the machine when it had instant power off issues when tapped between the screen hinge and top of the keyboard, or some places on the palmrest, so a flex issue perhaps?Machine powers up, but no video, nothing on VGA/HDMI or the internal interface. Screen assumed known working, as it's an old one.Service manual can be found if [NB solutions]DAR18D.pdf searched for in your favourite search engine. Would attach, but too large.

author: 6PTsocket
author_rank: Regular Contributor
timestamp: November 04, 2018, 01:43:36 pm
content: The flex cable goes from the motherboard to the screen take it apart and try reseating it. If you can't get video out of the HDMI, the problem could be more serious. When I repaired my HP laptop with similar problems, the video processor had failed and I had to replace the motherboard. I don't know what model you have but there were issues with video failures because they ran too hot. Improvements by HP and after market additional heat sinking seemed to help. Are you a big gamer? That works the video pretty hard. Of course, the best I can do from this end is guess.Sent from my SM-G900V using Tapatalk
How to avoid capacitive loading when using my osciloscope - Page 1
Forum section: electronics / beginners

author: michalism
author_rank: Regular Contributor
timestamp: May 07, 2020, 12:58:14 pm
content: Hi all.I'm trying to find a way to ensure that I am not adding a capacitive load to a component when probing around with my osciloscope. You can refer to an older post of mine, where I fried an IC trying to figure out a problem:https://www.eevblog.com/forum/repair/ksger-t12-mini-soldering-station-doa/msg2459682/#msg2459682I have tried Google and searching here in the forum, but I did not find anything on this matter.Thank you!Michalis

author: Siwastaja
author_rank: Super Contributor
timestamp: May 07, 2020, 01:10:54 pm
content: Use x10 probe instead of x1. Those with selectable switches, glue or tape it in the x10 position. x1 is very rarely needed IMHO, and it's frustrating whenever your probe has accidentally changed to a x1 probe and your voltage values are 10 times off.If you still have too much capacitance, the options are:A cheap DIY "lo-z" probehttps://www.eevblog.com/forum/projects/lo-z-probe/which trades lower HF AC impedance for higher DC resistance,Or an expensive active probe which has a tiny FET amplifier in it.Cases where the 10-20pF of capacitance wouldkilla circuit are very rare, though. It's likely you did something else which killed your soldering station. Ground loop, for example. Or shorting two adjacent pins with the tip.

author: cdev
author_rank: Super Contributor
timestamp: May 07, 2020, 01:26:29 pm
content: You can make your own active (FET) probe for just a few dollars in partsBob Pease wrote about this.https://easyeda.com/andyfierman/project-g2QNnljhfhttp://www.introni.it/pdf/Bob%20Pease%20Lab%20Notes%20Part%208.pdfGood to put into a hand-friendly well shielded enclosure.

author: michalism
author_rank: Regular Contributor
timestamp: May 08, 2020, 04:54:07 am
content: Excellent! thank you both!
How to best make AG13 (LR44) dummy battery? - Page 1
Forum section: electronics / beginners

author: Greorge
author_rank: Regular Contributor
timestamp: May 02, 2014, 11:27:53 am
content: Hi all,I want to use 1.2V AA NiMh rechargeable battery instead of AG13 (LR44) alkaline 1.5V button battery for little alarm clock.I tried clock with 1.2 NiMh and it works well (keeps good time for a week already), but I just pushed wires behind battery seat terminals and it is easily disconnected when moved, so I would like to make it with good contacts.I can probably improvise-design something, but hope it was done before so would like to get some nudge in good direction.

author: SeanB
author_rank: Super Contributor
timestamp: May 02, 2014, 12:12:39 pm
content: Small block of wood or nylon with a metal plate top and bottom held to it with epoxy or other glue, with wires soldered to it. Cheap and reliable.
How to better focus laser beam? - Page 1
Forum section: electronics / beginners

author: Logan
author_rank: Frequent Contributor
timestamp: August 13, 2021, 02:40:04 pm
content: Hi guys.I have a high power IR laser works fine at short distance, but the beam gets too wide as the target distance increases(like 1 meter wide at 20 meters target). I already tried to adjust the focus but that's the best I can get. I think maybe the beam from the LD is just too large, or the lens is not optimized... How can I improve it? I want the beam width to be as small as possible even the target is far away.Thanks.

author: highpower
author_rank: Regular Contributor
timestamp: August 14, 2021, 12:16:45 am
content: I simply made a smaller aperture for one of mine. The smaller the beam angle however makes it harder to be seen at distance.

author: jmelson
author_rank: Super Contributor
timestamp: August 14, 2021, 02:11:53 am
content: Most laser diodes emit an elliptical beam. You need a sphere lens almost touching the front of the laser and then may need another lens some distance away. To get the smallest spot, you may need an aperture in front of the sphere. I did this with a laser photoplotter I built and had to defocus it a bit to make the spot larger than 0.001" diameter. The front lens was a 15 mm focal length, so the focus was about 1/2" from the front lens. But, the basic scheme is the same.Jon

author: Logan
author_rank: Frequent Contributor
timestamp: August 14, 2021, 05:39:29 pm
content: Quote from: highpower on August 14, 2021, 12:16:45 amThanks.But I don't want to waste the energy by blocking it, I want to refocus all energy into a smaller beam.

author: Logan
author_rank: Frequent Contributor
timestamp: August 14, 2021, 05:40:28 pm
content: Quote from: jmelson on August 14, 2021, 02:11:53 amThank you, that sounds good, where can I buy such lens?
How to bias a common emitter amplifier without voltage divider network? - Page 1
Forum section: electronics / beginners

author: Dmeads
author_rank: Regular Contributor
timestamp: April 30, 2019, 07:19:40 pm
content: Hello All!In My Analog IC design class, we are learning about active loads with current mirrors. I want to simulate some of these in Ltspice.I am first working on a common emitter amplifier. I am having trouble setting the Vbe voltage to 0.7 volts. I read somewhere that you can still use the 4 resistor biasing network to set a base voltage, but the collector resistor can be an active load/current source. This still has 2 resistors tho (if the emitter resistor is a short).I know that in IC design, it is hard to build resistors onto a chip because they take up space, so I'm wondering if anyone knows any ways that involve an active load to set a base voltage/operating point for a common emitter amplifier? Or is this a case in IC design where you just have to use resistors?any .asc files would be appreciated!Thanks

author: Zero999
author_rank: Super Contributor
timestamp: April 30, 2019, 08:32:48 pm
content: The simple common emitter configuration is seldom used in ICs and certainly not in isolation. The problem is, the transconductance, therefore voltage gain, is so high, it's not possible to set VBE, without the transistor either being in cut-off or saturation.Most amplifier ICs have a differential pair at the input, essentially an op-amp. Quite often, as in the case with voltage regulators, it's buried with with inputs connected to a reference and potential divider.Awhile ago, I built a discrete op-amp, for educational purposes.Here's the LTSpice file. Note there is a common emitter amplifier in there, Q9, but it's within the feedback loop of the differential pair, which sorts the biasing out, with negative feedback.https://www.eevblog.com/forum/beginners/how-hard-is-it-a-make-a-transistor-opamp-like-lm358-chances-of-working/msg1403895/#msg1403895

author: Dmeads
author_rank: Regular Contributor
timestamp: May 01, 2019, 04:28:20 am
content: Amazing! thanks a lot! we just learned about the differential amplifier today!
How to blow an ESR meter - Page 1
Forum section: electronics / beginners

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: May 24, 2015, 08:55:00 am
content: Just a small post to tell how I manage to blow my $20 ESR meterI was testing a diode in a PSU. It was late, I was distracted and forgot to remove the tester hooks before switching on the PSU.There was a small bang!, a cloud of smoke and off was my meter.Two traces were black, but fortunately the traces were not cut.All the enamel was gone though.The atmega328 was dead, but as I had it on a zif socket, it just took me 10 seconds to plug it the other one I had. And its working again as new. This does not mean that ones wishes to do that everyday.
how to build a Portable hand held Video recorder and player with auto playback - Page 1
Forum section: electronics / beginners

author: 0john0
author_rank: Newbie
timestamp: August 05, 2019, 04:50:20 pm
content: Hello, I'm a newbie. I can use some help to guide as I attempt to research and build as I go.A want to build a small device no larger than say 4"x6"x1".It's function is to temporarily record video of any source (tv, computer, cam etc) for a user specified period of time. From seconds to minutes.It retains the recording in RAM until its scheduled time to playback. The RAM is then freed to continue recording the streaming video.It's basically a video delay switch box.This box would have a control to input the length to delay the playback from 0 to 5minutes.I making this with a friend for a magic act.I guess I would need:a micro controller to program what to do with the video stream data, where to store it, respond to the time delay input.need some kind of driver for the video(?)an input board that would allow inout of the time number (playback delay). Dial or digital etc.RAM large enough to record 6 minutes of 4K video stream . My guess is 2 Gigs of RAMI'll take one step at a time and practice with simple steps. First step tp practice is to build a simple video inputs to record and an output to play.Thanks in advance. I am sure that any comments i get will lead me to think and act on making something.Cheers~ John
How to cable this setup? - Page 1
Forum section: electronics / beginners

author: nukearts
author_rank: Newbie
timestamp: November 20, 2016, 10:01:43 pm
content: Hello,I am electronic music enthusiast and i am somehow getting more and more involved with vintage gear.Today i got this piece of Kit:A Heathkit FS-Breitband-Oszillograf de luxe IO-12Ehttps://goo.gl/photos/ZKAMrLbQGRNqFTKo9And it worksYeahBut i am not sure what the best option is to get the right cabling done for my intentions. I want to monitor my Audiooutput with this setup.So the vertical will be always a 1/4" TRS jack with the audiosignal. I have an RME Fireface 800 that is able to send out wordclock over BNC. I have thought of it is possible to use this wordclock signal for the horizontal input. But i am thinking how i make the cables right, that these banana plugs get the most directly connected without any great loss of shielding. (you see the photos.xD)greetings,Nuke

author: Ysjoelfir
author_rank: Frequent Contributor
timestamp: November 21, 2016, 12:08:28 pm
content: Hey mr Atomic BombAs far as I understood what you want to do I would suggest that the best way to achieve your goal would be a small opamp buffer driving the input of your scope. Even though the scope has a high input impedance which would indicate that it is no problem to connect it permanently parallel to your setup, I would expect some noise entering the audio line at the connection to the scope. That would also sort out the problem with the connections, just build it with two TRS jacks for input and output and two banana sockets for the connection to the scope. You coule even build it as a "plugin" for the scope, meaning to let some 4mm contacts protrude from the circuit in exactly the distance of the input ports of the scope. So you could plug the buffer circuit directly into the scope and wouldn`t have another pair of cables running around your setup.Edit: regarding your idea of using the worclock: as far as I understood what the wordclock is you can`t use that. It seems to be just a clock signal to syncronize every piece of equipment, there shouldn`t be any way of getting your actual audio signal from that.

author: nukearts
author_rank: Newbie
timestamp: November 22, 2016, 08:19:21 pm
content: Thank you very much for the answer Ysjoelfir.I realize now how much of a bad Idea the horizontal sync with the samplerate is. And I need to think of more about what I wanna see on the oscilloscope to bring it maybe to topic here.The Vernier frequency of this scope should go down to 30Hz. So i have a very short timewindow for seeing more of a waveform then just a cycle. Seems that i need a modern scope for getting more than one cycle of audiowaveform (if i assume things right now).greetings,Nuke
how to calculate blocking capacitor? - Page 1
Forum section: electronics / beginners

author: matise
author_rank: Contributor
timestamp: August 20, 2018, 08:38:26 am
content: hi.i have this max2650 amplifier and i want to know what value i need for its blocking capacitor.this is what the datascheet says:As shown in the Typical Operating Circuit, the MAX2650 is easy to use. Input and output series capacitors may be necessary to block DC bias voltages (generated by the MAX2650) from interacting with adjacent circuitry. These capacitors must be large enough to contribute negligible reactance in a 50Ω system at the minimum operating frequency. Use the following equation to calculate their minimum value:cblock = 53,000/f = (pf)where f (in MHz) is the minimum operating frequency.im to new to this to understand how to calculate that.if my freq. is 18Mhz...will it be 53/18 and 2.9 pF for capacitor?or:(53000/18000000 = 2.9 -03 is 2.9 nF)?what is the correct calculation?

author: Zero999
author_rank: Super Contributor
timestamp: August 20, 2018, 09:37:33 am
content: The capacitor should be big enough to pass the lowest frequency of interest.The cut-off frequency, i.e. the point where the amplitude is reduced by a factor of 0.707 can be calculated using the following formula:FC= 1/(2πRC)Where R is the load resistance and C is the capacitance.Rearrange for C:C = 1/(2πFCR)Choose a cut-off frequency of half the lowest frequency of interest, round the capacitor value up to the nearest E3 value and the capacitor will be more than big enough.

author: capt bullshot
author_rank: Super Contributor
timestamp: August 20, 2018, 09:58:37 am
content: This particular 53,000pF means 53nF. In other parts of the world (including where I live) it'd mean 53pF.So your minimum capacitor value calculates to 53/18 nF (2.9nF, same result as Hero999 for 3 Ohm reactance). In practice, a 10nF or 100nF will do the job well.

author: vk6zgo
author_rank: Super Contributor
timestamp: August 20, 2018, 10:19:21 am
content: Quote from: matise on August 20, 2018, 08:38:26 amThe first answer is incorrect.The second answer is correct, but they assumed you would, by using the frequency in MHz, get a result for C in pF of approx 2900 pF which (in your case),you would convert into nF.By expressing f in Hz, instead, your result was in uF, which you converted to nF,still getting the same answer.

author: matise
author_rank: Contributor
timestamp: August 20, 2018, 11:56:48 am
content: thank you all for answers!
How to calculate effective resolution of ciruit - Page 1
Forum section: electronics / beginners

author: embedded.world@aol.com
author_rank: Contributor
timestamp: June 10, 2014, 06:49:04 am
content: I am using 24 bit adc ADS1247 to measure voltage drop across thermsistor by passing current through it.http://www.digikey.com/product-detail/en/PR103J2/615-1069-ND/2651611Since thermistor value gets very large so I connected a 20K fixed resistor in parallel with it.1. Now my current source is 50uA with initial error is +-6% with temperature drift +-100ppm/C.2. Voltage reference is 2.048V with +-10mV & drift is +-15ppm/C.3. Resistor = 20K +-0.01% with drift +-5ppm/C.4. PGA = 2, operating range = -40C to +60C.5. Minimum voltage step need to measure = 75uV.Questions:1. How to calculate effective resolution I will get finally.2. Do I need any other factors to consider besides I mentioned above.3. Do final resolution is equal to ENOB?4. Will I be able to achieve minimum voltage step = 75uV with this adcCrosspost:http://forum.allaboutcircuits.com/showthread.php?p=736107#post736107

author: Dago
author_rank: Frequent Contributor
timestamp: June 10, 2014, 11:19:28 am
content: Start here:http://en.wikipedia.org/wiki/Propagation_of_uncertainty

author: woodchips
author_rank: Frequent Contributor
timestamp: June 11, 2014, 08:53:07 am
content: Provided the maximum voltage across the thermistor is less than about 600V, then yes. This is simply 75uV times 24 bit ADC resolution, + or -.Is this useful? No.What is more useful is what accuracy you can achieve, not to mention precision and repeatability. Resolution on its own is meaningless, just replacing a 16 bit ADC with a 24 bit ADC increases the resolution, but not necessarily accuracy, precision or repeatability. This is where you have to take into consideration the individual errors of each component.
How to calculate heatsinking with no package thermal resistance data? - Page 1
Forum section: electronics / beginners

author: Greg Robinson
author_rank: Regular Contributor
timestamp: June 10, 2020, 10:27:09 pm
content: Hi everyone.I'm working on an application that requires a FET be used in it's linear region, so need to calculate thermals for heatsinking.I came across the On Semi2SK3746, it has appropriate voltage, current, dissipation ratings, a DC SOA curve that allows me generous derating and a reasonable price.However, the datasheet does not indicate any thermal resistance data, only max channel temp, ambient and case temperature derating curves.There is no RθJC, RθJA, RθCS specified.I thought that perhaps On Semi might have further data on the specified package (TO-3P-3L) like some other manufacturers, but if they do I haven't had any luck finding it.Is this a case of comparing to other devices in the same package, finding a worst case and assuming that? How does one approach thermal design when such info isn't provided?Thanks for any guidance or insight!

author: langwadt
author_rank: Super Contributor
timestamp: June 10, 2020, 11:19:32 pm
content: the de-rating curve and max Tch should provide a starting point, i.e. 60W @ 80'C -> 60W/(150'C-80'C) = ~0.85C/W

author: Greg Robinson
author_rank: Regular Contributor
timestamp: June 10, 2020, 11:27:57 pm
content: Ah, thanks very much! Knew I must've been missing something obvious.
how to calculate lpddr5's bank capacity ? - Page 1
Forum section: electronics / beginners

author: letflying
author_rank: Newbie
timestamp: July 25, 2025, 09:30:41 am
content: For example, Micron's Chip is shown below.In the red region, there are 8 banks, so the bank capacity = 1GbBut the row and column product is 32768 * 64 = 2MbSo, the R&C product must multiply array prefetch bits to get the 1Gb capacity. Why?

author: BrianHG
author_rank: Super Contributor
timestamp: July 25, 2025, 09:08:14 pm
content: Quote from: letflying on July 25, 2025, 09:30:41 amYou forgot to include the burst and bank address space.2^(15rows +6 columns) = 2megs x16bits = 32mbit x 2^(3banks + 5burst) = 8192mbit, or, 1 gigabyte.
How to calculate RC constant with 2 capacitors? - Page 1
Forum section: electronics / beginners

author: deer_force_1
author_rank: Newbie
timestamp: January 16, 2018, 06:03:26 pm
content: Hi all, I'm having trouble calculating the RC constant of this circuit. Is it correct that you have to replace the voltage source with a short circuit and combine the resistors connected across the terminals of the capacitor? For only C1 or C2 I see that the RC constant is ( R1 || (R2+R3) )*C1, and similarly for C2 ignoring C1, but how can I calculate the RC constant of the whole circuit?Thank you

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: January 16, 2018, 07:15:04 pm
content: This circuit is not a single pole/zero circuit. Hence it can't be described with only one timeconstant... Unless C2 is so small it is not dominant?

author: Wimberleytech
author_rank: Super Contributor
timestamp: January 16, 2018, 08:16:10 pm
content: Quote from: TheUnnamedNewbie on January 16, 2018, 07:15:04 pmThis is correct!
How to calculate RSSI and Distance - Page 1
Forum section: electronics / beginners

author: vishal
author_rank: Regular Contributor
timestamp: March 28, 2017, 04:58:52 am
content: HiI am working in a mesh network..I need to calculate the RSSI and distance to localise an end device.I read the register value in the device to know the RSSI.Form this how can I convert it into RSSI in dBm and how this RSSI can be used to determine the x,y coordinate to locate a device.I read about the triangulation method.its not applicable here..Taking 3 points is difficult.Can you specfy a method for calculating the same.

author: ataradov
author_rank: Super Contributor
timestamp: March 28, 2017, 05:17:10 am
content: There is no correlation between distance and RSSI that will let you determine the location with any sort of accuracy.There are solution that are RSSI based, but they mostly suck, and require very careful antenna design.Why do you think that triangulation will not work? Measure RSSI to/from 3 other devices and some simple algebra will let you know relative position of the device in relation to the other 3. This assumes complete lack of noise and totally onmidirectional antennas, which never happens in real life.

author: tggzzz
author_rank: Super Contributor
timestamp: March 28, 2017, 08:24:25 am
content: Quote from: vishal on March 28, 2017, 04:58:52 amNot possible. The randomness of the radio propagation channel prevents it. Initial search terms: "multipath propagation" and "fresnel zone".Be grateful for multipath propagation; if it didn't exist, neither would cellphones and WLANs.
How to calculate the current in a PWM LED driver circuit - Page 1
Forum section: electronics / beginners

author: nathanpc
author_rank: Unknown
timestamp: October 11, 2015, 02:26:11 am
content: I've been fascinated by the simplicity of the driver circuit based in theYX8018in the prominent solar garden lights, they were able to simplify the circuit a lot in a simple boost topology by just running at fixed frequency and using the LED as the output rectifier. I was interested in building my own circuit using a 555 timer driving a small transistor, just to learn more about the topology, but in my research I was not able to find a equation, or at least a simpler explanation between the frequency, input voltage, and inductor value to be able to calculate the output current to the LED. Could someone help me understand how I can calculate the output current given these parameters?The closer I got to an answer was by reading theSLVA372C App Note, in the equations section, the inductor ripple current:Il = (Vin * D) / (f * L)Plugging the values I tested on my solar light's circuit:Il = (1.5 * 0.5) / (200000 * 330 * 10^-6)Il = 0.0107But when I measured the current to the LED using my DMM I got 6.3mA.

author: TerminalJack505
author_rank: Super Contributor
timestamp: October 11, 2015, 03:11:27 pm
content: Those equations look similar to ones I used inthis post.I don't think they will work in your case, however, since you need a constant output current and the equations are for a constant output voltage.Since you are basically operating the converter as an open loop (that is, no feedback) you should probably just pick some particular fixed parameters (switching frequency, inductor size, etc.) and then tweak the duty cycle until you get the desired result. This is something that you would need to do anyway since there will be variations in the parameters and there's no control loop to compensate for the variations. This likely won't satisfy your intellectual curiosity but will help you get the project done.For another example of using the 555 to drive LEDs with a constant current, see the attached. This circuit has the advantage of having a control loop. It could be easily modified to allow for dimming as well.
How to calculate the noise in LTSpice of an LT1021 buffer amplifier. - Page 1
Forum section: electronics / beginners

author: blackdog
author_rank: Frequent Contributor
timestamp: January 21, 2020, 12:18:19 pm
content: Hi,I'm a beginner in LTSpice and I can't figure out how to tie an LT1021-7V reference to my circuit and then look at the total noise.I'm developing a reference buffer to scale a 7V reference to 10V.The reference buffer must be idiot proof and have the lowest possible noise contribution.There are some more requirements I have but that will come later when I show you the whole thing here on the forum.The schematic below is not complete, the protection is not in the schematic.First the schematic where now is an LT1021-7 is placed at the input of the buffer and the not working comand for measuring the noise.The picture below is of the noise behavior of a noiseless 7V voltage source so not the LT1021-7, this is my reference.The intention is that I want to see the difference with a real reference, so I don't have to make adjustments if the reference circuit used, if the LT1021-7 or other Reference is dominant for the noise behavior of the whole circuit.So I would like to know if it is possible, of the present voltage references in LTSpice, to show their noise in my schematic and how I do it in the simulation command.This command that I already modified in several ways does not work:.noise V U3 dec 100 1 1000Do the voltage reference in LTSpice have a noise parameter?ThanksKind regards,Bram

author: blackdog
author_rank: Frequent Contributor
timestamp: January 21, 2020, 02:25:18 pm
content: Hi 3roomlab,Thanks for the awnser, do you know if the LTZ1000 has a noise profile?Kind regards,Bram

author: 3roomlab
author_rank: Frequent Contributor
timestamp: January 22, 2020, 12:39:21 am
content: Quote from: blackdog on January 21, 2020, 02:25:18 pmi tried [.noise] for some diode, it has a noise plot. but i have not seen a LTZ1000 noise model.most of the time i use BV and AC = 10uV for estimation.* for reference, the AD587 model looks like it has accurate noise parametersand the chart looks similar to 1021https://www.analog.com/media/en/simulation-models/spice-models/ad587.cir** added BV alternative
How to calculate the NTC ot Potenciometer as a thermal switch? - Page 1
Forum section: electronics / beginners

author: Chriss
author_rank: Frequent Contributor
timestamp: December 10, 2016, 09:39:59 pm
content: Hi!I have to make a simple circuit with UA741 OPAMP, NTC and a potentiometer for temperature monitoring.I have an 2K2 NTC which would be connected to one gate and I have to put some potentiometer to theother gate of the UA741.With the potentiometer I should adjust the temp between 30-60C or something around.So, here I need some help.What value of the potentiometer should I use to have a larger step of temperature adjustment.I mean, I won't does If I move the potentiometer 1mm left or right does the temp moves 30C etc.I played around with several potentiometer but it went over my head and I have no usable info also...Any advice which value should I use of the potentiometer to have a nice path in temperature until I move the potmeterwould be great for me.Thanks for any advice.My best regards.

author: mikerj
author_rank: Super Contributor
timestamp: December 12, 2016, 08:47:09 pm
content: When a potentiometer is driving a high input impedance (like an op-amp input) then the total resistance value of the potentiometer makes no difference to it's output voltage range.Vout = R2/(R1+R2) * Vin where R2 is the lower part of the resistance track in use, and R1 is the upper part. You should be able to see that changing the total resistance value (R1+R2) will have no effect on the output voltage since the ratio stays exactly the same.The way to restrict the output voltage range is by by adding fixed resistors in series with each end of the potentiometer track connections. e.g. if you had a 10k potentiometer and added 10k resistors either end of it, the voltage output range would be 1/3*Vin to 2/3*Vin.
How to calculate the op-amp output bypass for a buffered voltage or virtual GND - Page 1
Forum section: electronics / beginners

author: pg
author_rank: Newbie
timestamp: November 12, 2024, 09:34:23 am
content: I need a low impedance (reference-)voltage as well as a virtual ground. The classic way is to use an op-amp for that. I guess the simplest way is to use an op-amp that is stable with any capacitive load and put a C right at the output. But if the op-amp is not sable or an additional series resistor (along some clamping) is needed for protection, the arrangement show in the image is common.I will use some generic 5V 1MHz R2R op-amp (not decided which) and R1 will be small (10R..50R) to keep some of the R2R output range.But how to calculate the other values? I guess R1*C1 is the main factor that determines the frequency with the highest output impedance.I found something inhttps://www.analog.com/en/resources/analog-dialogue/articles/ask-the-applications-engineer-25.htmlbut Ro is unknown is my case and the doc does not explain why the values are chosen that way.Is there a good recipe how to choose the values (time constants R1*C1 and R2*C2) for a given op-amp speed?

author: Kleinstein
author_rank: Super Contributor
timestamp: November 12, 2024, 08:03:45 pm
content: The usual rule of thumb is to have R2*C2 slightly larger than R1*C1. The inclusion for the extra R_out of the OP-amp may already be more than needed.When using a R2R OP-amp, be careful of the transition region (often some 1 V from the positice supply) most RR OP-amps are pretty awful in that range. This could be an issue with a reference voltage.

author: Smokey
author_rank: Super Contributor
timestamp: November 12, 2024, 08:10:32 pm
content: You should be able to simulate this. What opamp?

author: David Hess
author_rank: Super Contributor
timestamp: November 12, 2024, 09:56:23 pm
content: Quote from: pg on November 12, 2024, 09:34:23 amThe speed of the operational amplifier does not matter much, however in my experience the R2*C2 time constant needs to be 4 to 10 times longer than the R1*C1 time constant for acceptable transient response. I am more likely to use this circuit to drive an output signal rather than a virtual ground.I think better for a virtual ground is to use just an aluminum electrolytic or solid tantalum capacitor directly across the output. If the capacitance is large enough, then combined with RO, it will produce dominant mode compensation and gain will fall below 1 before 90 degrees of phase shift so no oscillation will occur.

author: Zero999
author_rank: Super Contributor
timestamp: November 13, 2024, 12:27:54 pm
content: What's the virtual ground used for?If its just connected to some other op-amps, same as the op-amp in the virtual ground, then there's little point in adding a capacitor on the output.
How to calculate torque - Page 1
Forum section: electronics / beginners

author: jismal
author_rank: Contributor
timestamp: February 12, 2019, 09:13:20 am
content: Hello GuysCould you please help me selecting the motor. I need to know the torque required for the motor.#1 Cylinder is about 1.5kg#2 and the l clamp is of 2kg

author: madires
author_rank: Super Contributor
timestamp: February 12, 2019, 10:45:48 am
content: Basic physics:F = m*a (in this case: a = g)M = h * F

author: Mechatrommer
author_rank: Super Contributor
timestamp: February 12, 2019, 11:08:03 am
content: torque = force x lengthgravitational force as madires stated = m.g (mass x gravitational acceleration) = weight.you need to breakdown your system into several simpler parts so you can determine their centre of gravity (COG) one by one. from there you can get length from COG to rotor and perpendicular length to vector of gravity. multiply weight with that perpendicular distance, add them all for every breakdowned parts (additive if same rotational direction, subtractive if counter rotation) you'll get total effective gravitational torque... well, for longer answer... attend a class.

author: Nusa
author_rank: Super Contributor
timestamp: February 12, 2019, 11:53:04 am
content: Torque required for the motor to do what in how much time?You need to define the task the motor is required to accomplish.
How to calculate total amps required for various voltages? - Page 1
Forum section: electronics / beginners

author: shai
author_rank: Contributor
timestamp: January 19, 2019, 08:50:15 am
content: Say I have 12V for power, but I have a PCB with loads that use 3v, 5v and 12v. How do I figure out the total amps all the loads consume? Do I do 3V x amps = watts and then add up all the watts and divide by 12v to figure out the total amps? Is watts used as a common denominator? Thanks!

author: Rerouter
author_rank: Super Contributor
timestamp: January 19, 2019, 09:03:46 am
content: in this case it would be (3V x amps) / efficiency = input watts, then input watts / 12 = input amps.your probably using switchmode regulators, but they are not 100% efficient so they will pull a bit extra than just the load watts would say.

author: Ian.M
author_rank: Super Contributor
timestamp: January 19, 2019, 02:05:38 pm
content: If there are any linear regulators, their input current is their output current + their quiescent current (usually negligible). The difference between their input and output powers (calculated from V*I) is thrown away as heat.

author: shai
author_rank: Contributor
timestamp: January 20, 2019, 12:02:12 am
content: Hi, thank you for the help, but I am confused what you mean by efficiency? I'm using a linear regulator, specifically the LM1117. Can you please post an example calculation on how I can figure out how much 12V amps I need to feed the PCB if I have a 12V 2A component and a 3V 0.5A component?

author: sleemanj
author_rank: Super Contributor
timestamp: January 20, 2019, 12:05:57 am
content: Since you are only using linear regulators, just sum all three (load) currents. Input current = output current for a linear regulator, ignoring quiescent.

author: Rerouter
author_rank: Super Contributor
timestamp: January 20, 2019, 12:07:12 am
content: Linear regulators essentially burn off the voltage difference as heat, so a 0.5A load on 3V draws 0.5A at 12V, and burns 4.5W of heat in the process.Be aware this will put your regulator into thermal shutdown if your not careful, that is a lot of heat.

author: james_s
author_rank: Super Contributor
timestamp: January 20, 2019, 04:17:16 am
content: Think of linear regulators as automatic series resistors that adjust their resistance as needed to maintain the specified output voltage into whatever load that is on it. The current through any point in a series circuit is the same, therefore the current at the input of a linear regulator must equal the current drawn from the output.

author: bson
author_rank: Unknown
timestamp: January 20, 2019, 07:19:25 am
content: Quote from: shai on January 20, 2019, 12:02:12 amCurrents add regardless of voltage, so you need 2+0.5 = 2.5A.
How to calculate type III compensation network for Buck-Boost DC/DC converter? - Page 1
Forum section: electronics / beginners

author: Komajster
author_rank: Contributor
timestamp: January 24, 2021, 02:34:58 am
content: Hello!I'm trying to design a circuit based on Linear Technology's LTC3533 Buck-Boost DC/DC Converter (https://www.analog.com/media/en/technical-documentation/data-sheets/3533fc.pdf) for my own project. One of the last things I have left to do is to calculate the feedback loop compensation network (datasheet page 14, I need the Vout to be 5 V, so I can't use the stock values from demonstration circuit that's designed for 3.3 V output(https://www.analog.com/media/en/technical-documentation/eval-board-schematic/DC999A-SCH.pdf)). I want to use the type III compensation due to its advantages described in the datasheet. I have calculated the most convenient feedback resistor divider values to be 620 kΩ and 200 kΩ, but I don't understand how this compensation network works and what to do next. I have found two application notes talking about these circuits (https://www.infineon.com/dgdl/an-1162.pdf?fileId=5546d462533600a40153559a8e17111aandhttps://www.ti.com/lit/an/slva662/slva662.pdf), but I still can't get it. What are the poles and zeros of the compensation? I think they define how the internal op-amp gain curve looks, but why is this curve represented by frequencies and why would I want to change it with this compensator?I know that Linear Technology has this tool called "LTpowerCAD" that presumably would let me calculate the component values for this compensation network easily, but the LTC3533 is not included there and even if it was I still wouldn't understand how this circuit works. Also I'm 17 years old if that changes anything
How to change between different capacitance values with an MCU? - Page 1
Forum section: electronics / beginners

author: Hbst1
author_rank: Newbie
timestamp: April 03, 2022, 04:04:10 pm
content: Dear community,New hobbyst's question here.I am measuring low voltages (mV range) with an analog frontend of which the digital high pass filter is configurable by capacitor values.0.1 uF stands for 5 Hz1 uF for 0.5 Hz10 uF for 0.05 Hz filter.Instead of soldering a capacitor with a fixed value, i would prefer a way that allows me to change between these values with a microcontroller.Are there non-mechanical switches for such a purpose or could perhaps MOSFETS be used for this purpose?Which way should one prefer to do that?

author: Alti
author_rank: Frequent Contributor
timestamp: April 03, 2022, 04:50:33 pm
content: I think you cannot beat 4051/4052/4053 muxes in such applications. Designed exactly for this purpose. There are dozens of variations, from 1.8V up to 18V. Start from 74HC4053.
How to change politary of a circuit  - Page 1
Forum section: electronics / beginners

author: 1makermold
author_rank: Contributor
timestamp: May 29, 2019, 02:33:23 am
content: How could I change the polarity of this circuit, to use PNP transistors

author: Pooldawg
author_rank: Contributor
timestamp: May 29, 2019, 03:15:09 am
content: Quote from: 1makermold on May 29, 2019, 02:33:23 amWithout seeing what the two rail inputs are doing, it is a little tough.You can simply swap in the transistor, however your "enable" for the transistor will also be swapped. When it is a low, the transister will turn on, and when it is a high, it will turn off. Vs now it is off when low and on when hi.This simple video may help you:

author: MarkF
author_rank: Super Contributor
timestamp: May 29, 2019, 03:32:15 am
content: Is this for Lionel Model Railroad? Is it DCC?This takes some thought. I re-arranged the circuit to make it clearer to me.

author: mikerj
author_rank: Super Contributor
timestamp: May 29, 2019, 11:58:36 am
content: What is the problem with using NPN transistors?

author: 1makermold
author_rank: Contributor
timestamp: May 29, 2019, 12:23:31 pm
content: Yes this is a circuit for Lionel trains that run on 0-18 vac. It is not DCCWhat it does is when it gets a signal of positive dc voltage to the outside rail it turns on the optocoupler and it turns on the whistle, I would like to reverse the polarity so when I send a negative dc voltage to the outside rail it would activate a bell.

author: MarkF
author_rank: Super Contributor
timestamp: May 29, 2019, 06:35:22 pm
content: A little research here. How are you going to generate the signals?http://www.trainfacts.com/trainfacts/?p=330https://ogrforum.ogaugerr.com/topic/lionel-sound-activation-buttonhttp://doerry.org/norbert/train/SpeedandDirectionalControlofAmericanFlyerTrains.pdfPages 39 and 40.

author: MarkF
author_rank: Super Contributor
timestamp: May 29, 2019, 07:09:11 pm
content: I simplified version of your circuit

author: 1makermold
author_rank: Contributor
timestamp: May 29, 2019, 07:29:08 pm
content: I tried that one i couldn't get it to work, I am sending a signal kind of like the one that you have posted, but I use a 10 vac transformer and a bridge recitfer and a make shift polarized capacitor, when I get some time I will make a drawing of it

author: MarkF
author_rank: Super Contributor
timestamp: May 30, 2019, 04:09:04 pm
content: Quote from: 1makermold on May 29, 2019, 07:29:08 pmThere's not a lot of difference between the two. The problem might have been that the 2N3904 doesn't have enough gain.Does this circuit have to fit inside the locomotive (or tender)?One quick thought without any investigating, you might try a second copy of the circuit with the rail wires reversed.Since it's a DC shift of the AC, just reversing the inputs would see the opposite DC shift.Really need to see how you are generating the rail power or at least your waveforms.

author: 1makermold
author_rank: Contributor
timestamp: May 31, 2019, 12:18:28 am
content: This circuit fits inside the tender, if you switch the wires around the circuit doesn't work
how to change run length at ModelSim.  - Page 1
Forum section: electronics / beginners

author: hatokay
author_rank: Newbie
timestamp: January 04, 2019, 04:04:21 pm
content: hey guys, dose someone has any idea how to change the run length time at the software ModelSim form ns (nano seconds) to ps (pico seconds).i have 10.4a version and i have the run length thing stuck on ns when i need ps.thx for the help.

author: Bassman59
author_rank: Super Contributor
timestamp: January 04, 2019, 11:26:39 pm
content: Quote from: hatokay on January 04, 2019, 04:04:21 pmThat's not the "run length." That's the simulator resolution.Create a Simulation Configuration. (Right-click in the Project area, choose "Add To Project," choose "Simulation Configuration.") Give your configuration a name. Choose the top-level entity and architecture (generally your test bench file's entity). You should see "Resolution" in the lower-right corner. It is usually set to "Default." Change it to whatever you like.When you double-click on a Simulation Configuration, the vsim command is executed. But the simulation has not started running yet. Add signals to the waveform viewer and the typerun {runtime}into the transcript/terminal window. You can give that run time any units you like, like for instance run 10 ms simulates the first 10 milliseconds.

author: hatokay
author_rank: Newbie
timestamp: January 05, 2019, 11:05:01 am
content: Quote from: Bassman59 on January 04, 2019, 11:26:39 pmthank you so much man! you helped me alot
How to change the direction of the current in a control system? - Page 1
Forum section: electronics / beginners

author: SatoruSatake
author_rank: Newbie
timestamp: November 11, 2014, 12:03:34 pm
content: Hello everyone,!I was given a hard question from my "control system" professor ,the question is: there are two input through a op-amp(+12Volt and -12Volt),so, how to achieve that "when the +12V through the circuit, the current has a deriction, and when the -12V is applied, the current has another direction?" Can I use the "Howland Current Pump"? If not, what can I choose?Thank you!

author: Andy Watson
author_rank: Super Contributor
timestamp: November 11, 2014, 12:34:34 pm
content: Yes, the Howland configuration would be good.It does depend on the magnitude of the current you are controlling. At low levels of current you could also look at transconductance amplifiers - like LM13700, or CA3080.

author: SatoruSatake
author_rank: Newbie
timestamp: November 11, 2014, 01:06:24 pm
content: Thank you Andy! I got it!
How to charge batteries from PSU without blowing up PSU - Page 1
Forum section: electronics / beginners

author: skillz21
author_rank: Frequent Contributor
timestamp: October 23, 2019, 06:51:17 am
content: I have seen some videos online where people have broken their power supplies from charging batteries. My question is, if I wanted to change a battery with a lab bench power supply, how can I make sure that my power supply won't blow up?

author: spiette
author_rank: Newbie
timestamp: October 23, 2019, 06:55:37 am
content: Without knowing the battery type and chemistry the only thing I can offer is use a diode in series to block any reverse current into the PS.

author: skillz21
author_rank: Frequent Contributor
timestamp: October 23, 2019, 07:03:39 am
content: Ok, so would just adding a diode work for the following batteries?:- 3.7v lithium-ion- 12v lead acid

author: JohnPen
author_rank: Regular Contributor
timestamp: October 23, 2019, 08:17:47 am
content: The best way is to set your PSU to the relevant voltage before connecting it to the battery. Typically 13.8v for the normal 12v car battery. This will be roughly replicating what the alternator provides in normal driving conditions. If your PSU has current limiting available you can control the charge rate with that providing you have set the PSU output voltage to ~13.8v or slightly above. The use of a series diode offers protection of the PSU and prevents the battery voltage from possibly damaging the PSU. If you have set the PSU output voltage to be greater than the battery voltage there is not a problem. Similarly for 3.7v Li cells etc the PSU output voltage should be ~4.2v. Note if you do add a series diode you will typically need to increase the PSU output voltage a further 0.6v (schottky ~0.2v) to cover the voltage drop across the diode and the diode must be able to manage the maximum charging current.John

author: soldar
author_rank: Super Contributor
timestamp: October 23, 2019, 08:20:38 am
content: Set voltage to a voltage somewhat higher than battery. (Essential)Set current to a value safe for battery and for power supply. (Essential)Make sure PSU is protected against back voltage from battery. (The truth is that I never do this.)

author: mikerj
author_rank: Super Contributor
timestamp: October 23, 2019, 12:28:59 pm
content: What often kills power supply's when charging batteries is connecting the battery whilst the PSU is turned off, or turning off the PSU while the battery is connected. Some PSUs tolerate this, some don't.
How to charge multi cell li-ion battery pack ? - Page 1
Forum section: electronics / beginners

author: gabri.peic
author_rank: Regular Contributor
timestamp: February 21, 2020, 08:05:22 pm
content: Hi i am making a portable Bluetooth speaker for which I need around 24v battery pack.I am planning on using 6 18650 cells in series. But how do i charge them? I want to have built in mains power supply in the speaker so when I plug it in it charges the battery and switches over to powering directly from the power supply. So can i just solder BMS to batteries and charge them through constant current board with 25.2v and than just use Relay to switch all the electronics to power supply when i plug it in the wall.