hybridfree/eevblog-posts huggingface dataset:
Is this possible? - Page 1
Forum section: electronics / beginners

author: nadona
author_rank: Regular Contributor
timestamp: April 01, 2013, 06:16:41 am
content: To get a square wave output directly out of a crystal oscillator likethis one?

author: EEVblog
author_rank: Unknown
timestamp: April 01, 2013, 06:25:40 am
content: Yes, that's precisely what these oscillators give out.

author: nadona
author_rank: Regular Contributor
timestamp: April 01, 2013, 09:28:59 am
content: Thank you David!
Is this PWM controller? - Page 1
Forum section: electronics / beginners

author: Stan21
author_rank: Contributor
timestamp: May 01, 2022, 03:11:32 am
content: I have a pcb that controls a small electric motor speed with a pot.I tried to "reverse-engineer" connections diagram and this is what I got:Is this a PWM controller?

author: ledtester
author_rank: Super Contributor
timestamp: May 01, 2022, 04:02:23 am
content: No, the motor is continuously running and the pot has a direct control of its current.You can play with a Falstad simulation here:https://tinyurl.com/y55lpan5

author: Zero999
author_rank: Super Contributor
timestamp: May 01, 2022, 07:49:28 am
content: It's a magic smoke generator because the battery's polarity is incorrect.Even if the battery is connected correctly, it won't work very well because the motor current is dependant on the hFEof the transistors.Use a 555 timer. This circuit shows an incandescent lamp, which should be replaced with your motor and diode in reverse parallel.

author: strawberry
author_rank: Super Contributor
timestamp: May 01, 2022, 05:04:28 pm
content: Quote from: ledtester on May 01, 2022, 04:02:23 amNo current sense in circuit, regulates motor voltage across motor proportional to pot position
Is This Safe Way to Power Arduino Slaves? (I2C Powering 2 Pro Minis Off of Uno) - Page 1
Forum section: electronics / beginners

author: Potomac
author_rank: Regular Contributor
timestamp: September 13, 2016, 01:32:14 am
content: I have been playing around I2C with a master that is an Uno and 2 slaves that are Pro MinisWhen I first started (and executed the communication code correctly), I was powering the rails on my breadboard feeding into the VCC pins of the minis with 5V from a benchtop supply. (See Method 1 in the picture below)This is annoying and makes me have to sit next to the bench supply.Is it safe to instead use the 5V pin on the master Uno to power the rails that feed into the VCC pins of the Pro Minis?In theory I think this should be fine, but I am not sure. Will it exceed the current limits?See picture attached for visuals of what I'm trying to do

author: rrinker
author_rank: Super Contributor
timestamp: September 13, 2016, 01:46:52 am
content: For a trivial test where the most you are doing is lighting up an LED, you should be ok. But what you REALLY should do is feed your power supply rails to the breadboard, and tap off there to the Vin and Gnd on the Uno and power the Uno from the bench supply along with the Minis, then everything is turned on and off with one switch, or just by disconnected one of the pins from the bench supply.
Is this scope working properly - Page 1
Forum section: electronics / beginners

author: Rakcom
author_rank: Newbie
timestamp: December 25, 2018, 11:30:17 pm
content: Hi,I am in my second year of Electrical Engineering and I have just received my first proper scope. A Hantek DSO5072P (I also have a Pokithttps://pokitmeter.com/)Today I have been playing around with it and the Pokit by looking at a 0.5kHz square wave generated by a Raspberry Pi 3B+.This is what they have shownThe Hantek:The Pokit:I have also included the excel files that I got from the csv files that both have given me.What I find strange is that the Hantek peaks at 3.7V while the Pokit peaks at a more reasonable 3.37V. Both show a steady state at 3.3VBoth are DC coupled, in their normal mode, the Hantek has been calibrated, the Pokit is the 1MSps version, and I have kept their leads as straight as possible.My question is there a way to fix the Hantek, should I return it, or is the Pokit lying to me and this 0.4V spike is normal?

author: Tom45
author_rank: Frequent Contributor
timestamp: December 25, 2018, 11:38:12 pm
content: It looks like you need to adjust the Hantek's probe compensation.

author: Rakcom
author_rank: Newbie
timestamp: December 25, 2018, 11:45:30 pm
content: I just switched the probes to 1X mode and that fixed itAt Uni only a few of our probes have that selection slider so I seemed to have forgotten on it.Thanks

author: Tom45
author_rank: Frequent Contributor
timestamp: December 26, 2018, 08:09:46 am
content: While switching from 10x to 1x solved the immediate problem that you were seeing, in the long term you need to understand what is going on with scope probes.Your probe in 10x mode would have worked equally well if it had been compensated. And more to the point, a 10x probe will have higher frequency response and put less loading on your circuit. In most cases, a 10x probe is what you will normally be using.Do a search for oscilloscope probe compensation to learn about probe compensation. A good example is:The video is by W2AEW who is a Tektronix employee and is active on eevblog as well as being a good teacher.
Is this symbol for shielded cables ? - Page 1
Forum section: electronics / beginners

author: MathWizard
author_rank: Super Contributor
timestamp: February 20, 2022, 07:55:58 am
content: I was looking at a Heathkit radio and I see the symbol and C label of a capacitor, but with a wire running through it. There's a few on the top of the pagehttps://www.vintage-radio.info/download.php?id=780Down in the notes they use ( ) and say that's shielded cables, is that what those are ? ) (

author: oPossum
author_rank: Super Contributor
timestamp: February 20, 2022, 08:09:32 am
content: feedthrough capacitor

author: MathWizard
author_rank: Super Contributor
timestamp: February 20, 2022, 09:01:12 am
content: Ok thanks, I don't remember hearing of them beforehttps://www.utmel.com/blog/categories/capacitors/what-is-feedthrough-capacitor
Is this the 8002A chip? - Page 1
Forum section: electronics / beginners

author: Azhar
author_rank: Regular Contributor
timestamp: June 04, 2017, 01:42:50 pm
content: I need to replace this unknown chip, it's an Audio Amplifier, I can see only the last 3 symbols on the chip and after I did some googling, I believe it is the 8002A Audio Power Amplifierbut I am not 100% sure. what do u guys think? is it the 8002 or something similar?thanksdatasheet:http://www.shenzhensum.com/products/datasheet/8002(2.0W).pdf

author: grumpydoc
author_rank: Super Contributor
timestamp: June 04, 2017, 01:53:03 pm
content: It would seem to fit

author: Azhar
author_rank: Regular Contributor
timestamp: June 05, 2017, 07:21:15 am
content: that's what I think, I ordered the replacement and will see

author: stj
author_rank: Super Contributor
timestamp: June 05, 2017, 07:48:46 am
content: lift it, the part number may be printed on the board - it seems that way for the other components.

author: Azhar
author_rank: Regular Contributor
timestamp: June 05, 2017, 07:54:15 am
content: thanks, i didn't pay attention to the prints, awesome
Is this the right switch for me? AV project - Page 1
Forum section: electronics / beginners

author: leham
author_rank: Regular Contributor
timestamp: July 02, 2017, 05:51:37 am
content: Helooo!I'm currently working on a personal project that involves RGB videoRather than spending stupid money on SCART cables, I'm using cheap old VGA cables, buy them in bulk cheap asOk, so sucks for me because 99% of "VGA" cables aren't 1:1, so I need to run external 3 core cable for audio, not a big deal as thats cheap too and most "vga" cables only have shielding on the RGB lines ...ANY WAY on topic:I have up to 10 devices I want to connect to a single SCART input on the TVusing a common ground for everything, I'll need 7 wires per deviceHow can I switch between a bunch of these devices?ie: VIDEO Player (rgb) 1of10 > Switch box> single SCART input on TVI found these:https://www.aliexpress.com/item/10-Pcs-12-Pin-On-On-2-Position-4P2T-4PDT-Mini-Vertical-Slide-Switch-0-3A/32547019978.htmlThey are only 4PDT, could I just use 2 switches and either switch two per input or physically join them?Or I found these>http://www.goldmine-elec-products.com/prodinfo.asp?number=G20041What would be better?Thanks

author: leham
author_rank: Regular Contributor
timestamp: July 02, 2017, 06:30:11 am
content: OR should I just buy two of these?https://www.aliexpress.com/item/2017-Newest-Arrival-8-Port-VGA-SVGA-Switch-Box-8-Input-1-Output-VGA-Monitor-Share/32813199093.html

author: Benta
author_rank: Super Contributor
timestamp: July 02, 2017, 09:40:32 am
content: What AV devices do you need to connect?Reason for my question is, that practically all the consumer AV devices (VCR, DVD, TV etc) I've seen do not provide RGB at the SCART connector, but only CVBS+L+R, so you'd only need a 3-pole switch (plus perhaps the control line)If you're working with professional equipment, it's a different story, of course.

author: sokoloff
author_rank: Super Contributor
timestamp: July 02, 2017, 12:47:13 pm
content: I've used Extron matrix switchers with good effect to switch RGBHV (and some would also switch audio) signals before for home theater application. They're good kit and dirt cheap now.Look on Ebay for "Extron Crosspoint" or "Extron RGBHV matrix" or similar search terms.If you're near Cambridge, MA, I can sell you a working one cheap, but they're cheap enough on Ebay (the shipping can be high, because they're bulky).
Is this the right way to wire thermostat input / output? - Page 1
Forum section: electronics / beginners

author: petreza
author_rank: Contributor
timestamp: December 17, 2019, 08:54:52 pm
content: I have this thermostat that uses one of those finicky universal outputs. The contact is not very good, sparks fly/buzzing sound, see the left top corner of the gray plastic - it has melted. This is with the heater at the lowest setting - 500W.When I looked at the internal cables that connect the input (jack)--(relay)--(output jack) something struck me as odd - the right input (red) is connected to the left (red) output.1. Is this how it is supposed to be - mirror image?When I plug in cables in both input and output:I get continuity between these two wires:2. Also, just to confirm - the relay connects/disconnects the blue and the yellow - the red one that goes in the back is just to power the thermostat/relay?

author: GerryR
author_rank: Frequent Contributor
timestamp: December 17, 2019, 11:32:16 pm
content: It looks to me that your relay is switching the neutral (Blue) instead of the hot (Red). From your picture with the meter, the hot and neutral are swapped. By convention (and the way you have them marked), Red is Hot, Blue is Neutral and Green is Ground. The relay should be switching the hot, at least that is how it is normally done.

author: Nusa
author_rank: Super Contributor
timestamp: December 18, 2019, 01:07:21 am
content: So-called universal outlets can't get the polarity right for all countries, because all countries are not consistent. However, IEC inputs ARE consistent in polarity, if not voltage. Assuming, of course, that the IEC input cords are wired correctly, which they occasionally aren't.So yes, when you're using a US plug, you're getting hot and neutral swapped. Which could be dangerous with some devices. If you're never going to travel internationally with this device, I'd suggest correcting it.
Is this transformer powerful enough? - Page 1
Forum section: electronics / beginners

author: illusive
author_rank: Regular Contributor
timestamp: February 04, 2018, 02:13:16 pm
content: Hi everyone,I'm DIY-ing a soldering station. The soldering iron i've bought is the SP-90B which has 90 watt rated heater. The resistance of the heater at room temperature is about 1.9ohms. Originally i've planned to use 100VA 24AC transformer but now i have second thoughts. I did some basic tests with a 100VA 24VAC transformer - the startup current at 24 degrees is about 8.23A rms, the voltage drops to about 22V rms. As the temperature increases logically the resistance of the heater does as well and the current drops. The target temperature of 350 degrees is reached for 12 seconds at which point the current is about 4.3A rms, and the heater resistance is 4.4ohms. The resistance measurements are taken from UNI-T 139C multimeter, so they can be a bit off, the V and A measurements are from a oscilloscope. I know this is overloading the transformer, but the idea is that that much power will be drawn only for the first 12 seconds at startup. Then just a small bursts of power will be required to maintain the temperature.The original station, that this iron is made for, claims heat up time of 10 seconds, but i don't know to what temperature is the iron set up to. The transformer inside looks about the same size as mine 100VA one.The soldering station controller is not build yet, so i cannot test the thermal preformance of the transformer under real world usage conditions with the soldering iron, so i was wondering if someone with more experience with power transformers can give me advice.Thanks!

author: Zero999
author_rank: Super Contributor
timestamp: February 04, 2018, 03:38:18 pm
content: It should be fine. Transformers can withstand short overloads with no problems.

author: David Hess
author_rank: Super Contributor
timestamp: February 05, 2018, 06:46:44 pm
content: I agree; it will work fine. Once the iron heats up, the duty cycle is low.
Is this Triac toast ? - Page 1
Forum section: electronics / beginners

author: MathWizard
author_rank: Super Contributor
timestamp: August 28, 2024, 02:13:41 am
content: I have a 40A heater triac here, and out of circuit it reads 10's of Megaohms between M1, M2 for both polarities.Same for M2 to Gate, and over the 4V limit for diode mode. Shouldn't that be a diode drop?And M1 to gate reads 30 ohms, both ways. So isn't that fried ? It was hard to desolder, took awhile, IDK how much I would trust it now anyways. But yeah before I took it out, I could see a 24R reading 13R, so yeah it's the M1-G doing it.

author: bostonman
author_rank: Super Contributor
timestamp: August 28, 2024, 02:56:24 am
content: My feedback won't help, but I went through similar measurements with a TRIAC and was told measuring the resistance isn't accurate.I don't remember the exact series of events, but remember thinking similarly to what you're expecting.

author: floobydust
author_rank: Super Contributor
timestamp: August 28, 2024, 03:49:59 am
content: I've measured ~100Ω Gate-MT1 on good triacs likeBTA41.It's as if they have a gate resistor there to increase dV/dt rating. Open everywhere else, a bit of leakage over 20MEGΩ MT1-MT2.If your gate-MT1 is nearly shorted, I'd expect the triac to not trigger.If in doubt run it on AC with a lightbulb, even 12V is OK for a test.

author: MathWizard
author_rank: Super Contributor
timestamp: August 28, 2024, 05:58:39 am
content: Ok I'll try my Triac tester circuit. The heater was getting stuck on, but everything on the PCB's looks ok so far.Well it seems to be working with a DC voltage of 16V in my tester, I get over 100mA total one way, and 82mA with the opposite polarity, and the correct LED lights up. I still might replace it and keep it for something much lower current, after taking a few minutes to desolder it, w/o the heatsink on it.
Is this USB cable properly shielded? - Page 1
Forum section: electronics / beginners

author: Anakiev
author_rank: Contributor
timestamp: January 07, 2025, 03:59:27 pm
content: Hi, can someone more experienced to say if this cable was properly shielded?I am replacing the USB connector of an old keyboard. It's a "low-speed USB device". Between the four USB conductors "VCC,D-,D+ and GND" there is a bare wire which I called "sh" (in yellow on the picture). Which is connected directly to GND inside the keyboard and to the outer metal body of the male USB connector. There is also a foil around all conductors I called "sh2" (in blue on the picture).There is no continuity between the blue "sh2" foil and yellow "sh". Shouldn't "sh2" and "sh" be connected together for proper shielding?Thank you.

author: Faranight
author_rank: Unknown
timestamp: January 07, 2025, 07:53:38 pm
content: How should a cable shield be connected to a device? To the ground on the peripheral? To the ground of the computer? To the ground on both ends? Well..."A cable shield should have a 360° connection to the chassis of the electronic device. The chassis acts like a Faraday cage, the cable shield is just an extension of that cage." - Rick Hartley

author: radiolistener
author_rank: Super Contributor
timestamp: January 08, 2025, 05:02:07 am
content: Quote from: Anakiev on January 07, 2025, 03:59:27 pmI think no. But it depends... If you decide to connect them together, it should be done on one side of the cable only, otherwise it may lead to interference issues due to common mode currents.

author: Anakiev
author_rank: Contributor
timestamp: January 08, 2025, 05:50:19 pm
content: Thank you for the replies. I've tried to connect the foil to the metal body of the USB connector but while soldering and putting the connector together the foil torn appart and I've cut it. It may still touch the metal but I can't test without poking into the cable or destroying the other end. I've soldered the bare wire "sh" to the USB and I think now is like it was original.My biggest concern is that the data signals may interfere another devices.
Is this Vpp is normal for Owon SPE - Page 1
Forum section: electronics / beginners

author: u666sa
author_rank: Frequent Contributor
timestamp: August 14, 2023, 07:12:47 pm
content: Can it be made less? How?

author: electr_peter
author_rank: Unknown
timestamp: August 30, 2023, 10:17:37 pm
content: Try enabling AC coupling and zoom in more, then you will get more accurate (and likely much lower) noise estimate.
Is UNI-T UTP1306S a good lab PSU ? (feedback needed) - Page 1
Forum section: electronics / beginners

author: TheQuentincc
author_rank: Newbie
timestamp: January 26, 2021, 08:18:57 am
content: Hi, I was looking to buy a pretty cheap lab psu in order to diagnosis shorted computer stuff to fix them (like on 12v plane or even lower one like 1v max), I found the UNI-T UTP1306S which is a 32V 6A PSU for about 75€ shipped by amazon, I already heard about UNI-T multimeter being quite good quality but I never heard of their PSU, I couldn't find a review here, the only one I found was a youtube video that said it was a good PSU, but that's only one review, also it seems like there is a "flaw", like settings are reset after power is cut, for exemple you set 5v then you shut down the PSU, at the next power up it would ramp to 10+v, is there a way to tweak/modify the firmware to fix this ?I was wondering if anyone here got this PSU to share some feedback, specially if it's a good bang for the buck and if the firmware can be tweaked to fix this voltage at startup issue.

author: FrankyRC
author_rank: Newbie
timestamp: January 29, 2021, 04:58:51 am
content: I am also interested in a review
ISE Meter - Page 1
Forum section: electronics / beginners

author: rafik
author_rank: Contributor
timestamp: February 10, 2022, 03:22:23 pm
content: Hello, I have an ISE meter with two bad caps C29, C37, there is a diode that seems to be bad too CR6; Could someone tell me what their equivalents are in mouser or digikey. I send you photos of these components. I will be really grateful for your help.73!
ISMIEC 32bit or 64bit for UCS500-M - Page 1
Forum section: electronics / beginners

author: Mandami
author_rank: Newbie
timestamp: October 09, 2019, 03:31:34 pm
content: Hello,Does someone have an old version of the ISMIEC software for UCS500-M test equipment, working on 32 bit, and it could be shared ? The one I have has been installed long time ago on some old machine and it is 16-bit. Because of that I cannot use it on 64-bit OS without making use of a 32-bit VM.Thank you.
iso image creation - Page 1
Forum section: electronics / beginners

author: abdullahseba
author_rank: Frequent Contributor
timestamp: June 05, 2014, 10:39:43 am
content: is there any soft ware that will convert a bootable hardisk/usb to a bootable iso image

author: Shock
author_rank: Super Contributor
timestamp: June 05, 2014, 12:25:13 pm
content: Imgburn will allow you to do it and it's free (and safe).In my opinion the best burning software out there.When you choose the menu option - create an image file from files/foldersYou will see an advanced tab and bootable disc tab, here you can enable the iso image as bootable.You can extract (dump) the boot info if required from an existing drive or image.Most operating systems have low level way of dumping the boot info this in the OS itself so even if imgburn can't dump it within the program you can get around it and just use Imgburn to select it for inclusion.I've made bootable CDs and DVDs images this way from windows and linux works great.Get help on their forums if you need further assistance.

author: abdullahseba
author_rank: Frequent Contributor
timestamp: June 08, 2014, 08:36:26 am
content: Quote from: Shock on June 05, 2014, 12:25:13 pmthank you
iso9001 compliant assets and products tracker - Page 1
Forum section: electronics / beginners

author: dima2000star
author_rank: Newbie
timestamp: June 28, 2019, 04:56:32 pm
content: Hi!I have a small electronics design company and found to be valuable to be iso9001 compliant.We started from documenting processes in Confluence and it works Ok for documents so far. As for PCBs and products, we make(small quantities) I can not find a proper tool to track them, track modifications, defects, etc... everything that is iso9001 require for internal assets and customer products tracking.What do you guys use?

author: vk6zgo
author_rank: Super Contributor
timestamp: June 29, 2019, 01:45:50 am
content: Quote from: dima2000star on June 28, 2019, 04:56:32 pmRemember, iso9001 does not imply anything about the quality of the final product, only that you are using the same process for each unit, each time, & have a paper trail that says so.You can make a terrible product which is impeccably iso9001 compliant.I worked for a company which was wildly enthused about becoming compliant, but had real problems with their process & ultimate product, but refused to fix them, as that would make their process less "trackable".I left before they achieved compliance.

author: dima2000star
author_rank: Newbie
timestamp: June 29, 2019, 02:58:32 pm
content: Thank you for your reply.I'm more talking about something which would allow me to track all equipment like for example oscilloscopes and schedule their service or calibration times. It can be done with some stickers of course, but I would like to put everything in a single database, setup notifications and person responsible, who will get notifications. It would be also good to link it to our processes description in Confluence.Also, our customer requires their materials and equipment tracking which would be also nice to put into the same system....
Isolate filtered and non-filtered supply - Page 1
Forum section: electronics / beginners

author: sparksflying
author_rank: Contributor
timestamp: November 16, 2013, 12:13:14 am
content: Hello, I am modifying a roller-door controller and want to use it's existing power supply to drive my stuff. The circuit simply switches unfiltered 24Vrms to a motor via a relay when you want to open the door.My low power circuit runs on 12V, so in my first attempt I simply put a big capacitor across the rectifier output and a 7812 to drive my modification. When I operate the door, the motor runs significantly faster than before, I assume this is because it used to run off unfiltered power and now has pure DC going to it.How do I tap off the unfiltered signal and create an isolated filtered rail for my mod?I have tried putting in an RC filter in LT spice, but the unfiltered rail still gets affected.I have drawn a picture of what the circuit looks like.

author: sync
author_rank: Frequent Contributor
timestamp: November 16, 2013, 12:39:11 am
content: Use a diode between the unfiltered DC and the cap. The cap will be charged through the diode. But it prevent that current flows back.Edit: There is a problem. When the 24Vrms are rectified and filtered it's about 33V DC (Vpeak = 1.4 * Vrms). A 7812 has a absolute maximum rating of 35V input. That's too close. The transformer can probably output more than 24Vrms (no load, high mains voltage).How much current needs the 12V circuit? Keep in mind that a linear regulator must dissipate the difference of input and output voltage into heat.

author: sparksflying
author_rank: Contributor
timestamp: November 16, 2013, 01:21:42 am
content: Thanks! It worked, such a simple solution.Sorry, I lied on my schematic, I actually used an LM317 with resistors because I didn't have a 7812 lying around (luckily I didn't have one). Seems as though the 317 can handle up to 40V.The device only draws 9mA, a TO-220 should easily handle that with no heat sink.P.S. My project was converting an old DIP switch coded door controller to a rolling code remote system, works great!Thanks again sync

author: SeanB
author_rank: Super Contributor
timestamp: November 16, 2013, 08:03:41 am
content: Most rolling code receivers are rated to operate from a power supply ranging from 8-30V AC or DC, as they have an internal rectifier and regulator. The ones I know that do that are the Centurion ones, and almost all of the fixed code ones as well.

author: sparksflying
author_rank: Contributor
timestamp: November 17, 2013, 11:41:25 am
content: Quote from: SeanB on November 16, 2013, 08:03:41 amI got this one off ebay:http://www.ebay.com.au/itm/290982492193It apparently uses the Microchip HCS301 KeeLoq Code Hopping Encoder.http://ww1.microchip.com/downloads/en/devicedoc/21143b.pdf
Isolate uart of two MCu - Page 1
Forum section: electronics / beginners

author: A2
author_rank: Contributor
timestamp: July 28, 2014, 08:15:20 am
content: I have to isloate uart of two MCU with the help of optocoupler.I have made a circuit which I had attached.is it the correct way to do?For me its looks ok.

author: David_AVD
author_rank: Super Contributor
timestamp: July 28, 2014, 08:33:59 am
content: I assume that you're not wiring those 4 pin connectors 1-1 ? (one is "upside down")

author: David Hess
author_rank: Super Contributor
timestamp: July 28, 2014, 04:29:16 pm
content: That looks like it will work but it will be slow.It may be worth studying how the MIDI interface works. It uses optocouplers for isolation at each receiver.

author: mij59
author_rank: Frequent Contributor
timestamp: July 28, 2014, 05:41:40 pm
content: Hi,For "high speed" you could use a 6N137 opto coupler, or digital isolators like the AD ADUM series.

author: David Hess
author_rank: Super Contributor
timestamp: July 28, 2014, 06:21:58 pm
content: If the optocoupler provides access to the base of the transistor like the CNY17 does, then there are various options to speed it up if additional signal conditioning is added. Usually this takes the form of resistance between the base and emitter to lower the storage time but since this lowers the gain, additional external amplification is needed.For slow applications, this is not needed.

author: fcb
author_rank: Super Contributor
timestamp: July 28, 2014, 06:58:55 pm
content: It all depends on data rate (baud). Your 10K pull-up on the photo-transistor looks a bit small in my experience.

author: David_AVD
author_rank: Super Contributor
timestamp: July 28, 2014, 09:12:45 pm
content: I use 6N137 optocouplers for up to 250Kb (DMX) speeds.
isolated coupling signals - Page 1
Forum section: electronics / beginners

author: doobedoobedo
author_rank: Regular Contributor
timestamp: March 29, 2020, 04:15:58 pm
content: I need to couple a signal generated by an MCU to emulate an analog sensor.It's a crank position sensor and has one connection to ground and the other to the PCM of the car, it's activated by a toothed wheel passing. The most common way these sensors are read is by zero crossing detection so I need to produce both positive and negative voltages as seen by the input to the PCM. I'd like to avoid using a separate power supply.Scope trace from the sensor with me cranking the engine by hand (hence the low frequency)I'm considering using a small transformer, would this be the best way?

author: StillTrying
author_rank: Super Contributor
timestamp: March 29, 2020, 04:31:46 pm
content: Just AC couple the ~2 Vpp to ~5 Vpp signal.

author: doobedoobedo
author_rank: Regular Contributor
timestamp: March 29, 2020, 04:39:35 pm
content: Could you expand? Do you mean through a cap?

author: StillTrying
author_rank: Super Contributor
timestamp: March 29, 2020, 04:51:30 pm
content: Yes, at a guess a 10uF with the +ve end connected to the MCU would do for starters.The MCU's output might need some voltage protection from noise spikes even if the engine's not running.

author: doobedoobedo
author_rank: Regular Contributor
timestamp: March 29, 2020, 05:12:01 pm
content: Cool I had considered capacitive coupling but wasn't sure about it.There will be no engine. I need to spoof the signal so that other systems will come online, traction control being the main one, power steering also only gets switched on with a running engine too, although I have proven CAN messages to switch than on independently.

author: Zero999
author_rank: Super Contributor
timestamp: March 30, 2020, 09:00:57 am
content: Capacitive coupling can also work, but it's obviously not truly isolated.A small audio transformer will work.

author: doobedoobedo
author_rank: Regular Contributor
timestamp: March 30, 2020, 11:28:52 am
content: Quote from: Zero999 on March 30, 2020, 09:00:57 amAudio transformers were what I was originally looking at, but was looking for viable alternatives. The main thing is getting the zero crossing from a +5V (or 3.3V) input signal. The MCU will already have a common ground with the rest of the car. I'm going to try the cap first as I have some on hand.I could possibly have used a better headline.
Isolated DC-DC Convertors / Why more than one +Vin/-Vin? - Page 1
Forum section: electronics / beginners

author: john21443
author_rank: Contributor
timestamp: April 22, 2018, 04:16:01 pm
content: I have noticed that with isolated DC DC converters that there tends to be duplicated input pins. For example, 2 pins labeled as +Vin. Is this just a convention? Because higher amperage is required on the input side only? Some other reason?Here is an example:http://www.meanwellusa.com/productPdf.aspx?i=858#1Page 4 contains the pin out.Thanks,John

author: Eka
author_rank: Regular Contributor
timestamp: April 22, 2018, 09:37:50 pm
content: Quote from: john21443 on April 22, 2018, 04:16:01 pmAll depends on the maker, and the format of the converter. I've usually only seen multiple pins on the outputs. Usually to high of current for a single pin is the reason for multiple pins. Some standard formats have multiple input and output pins specified.For the part you listed,Quotesums it up.
Isolated dc-dc/minimum load - Page 1
Forum section: electronics / beginners

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: March 16, 2015, 08:28:49 am
content: 1. In one of my circuit I need isolated dc-dc converter.2. Input is 4.5 to 6V & output required is 5V.I have selected a 9V dc-dc & then will use a linear regulator to generate +5V afterward.3. I had looked at Murata's NDY0509C , it will do the purpose. But only probelm I see is minimum load current. (55-83mA)4. My circuit has low power consumption. System remian in sleep for most of time.5. Does that mean I have to put a resistor to ground at output of dc-dc, so that it can maintain minimum load all the time.e.g in my case R = 9V/83mA = 108 ohm.6. Is there any other dc-dc for this purpose I can select

author: langwadt
author_rank: Super Contributor
timestamp: March 16, 2015, 09:53:49 am
content: Quote from: Vindhyachal.takniki on March 16, 2015, 08:28:49 amhow much power do you need?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 16, 2015, 12:43:57 pm
content: Yup. So... don't do that?Find a DC-DC that's actually rated for low current. Preferably with a regulated output, no minimum load requirement, and good efficiency at light loads. And use as small a device as you can... if it's "low power", do you *really* need three friggin watts isolated?If nothing else, you can roll your own. You might use one of those "micropower" switching controllers, that goes into pulse-skipping mode when lightly loaded. Beware that the voltage sense / feedback circuit will probably need continuous power, however (usually to light an LED that throttles down the controller's output; so the LED needs maximum current (~mA?) exactly on light loads!).Tim
Isolated DC/DC converter help - Page 1
Forum section: electronics / beginners

author: Sultanpepper123
author_rank: Regular Contributor
timestamp: April 22, 2020, 11:22:10 am
content: Hello, I would really appreciate if someone would share his insights on whether an isolated DC/DC converter of a fixed output (12V) can sustain that output even when input is lower than 12V, the datasheet says the input range 9-36 VDC which may be the answer but i would really like to get a confirmation if possible.Also a side question, this datasheet does not indicate any input or output filters or recommended capacitors for optimal operation except a 10F MLCC at the output , any recommendations on this ? my thought was to throw a few bulk capacitors at the input/output and call it a day.DC/DC ConverterDatasheet

author: Vovk_Z
author_rank: Super Contributor
timestamp: April 22, 2020, 11:57:58 am
content: There can be two types of isolated DC-DC. First is unegulated so output will depend on input (strictly or slightly). Those type devices are short input range rated, for example 12VDC/12VDC rated.But if they are rated 9-36 VDC(wide input range) to 12V - they must be regulated.

author: Sultanpepper123
author_rank: Regular Contributor
timestamp: April 22, 2020, 12:07:30 pm
content: Quote from: blueskull on April 22, 2020, 11:56:46 amThank you for sharing your time and insight, will throw a few caps on the input and output. Regarding the input requirements, do you think i might experience any problems if the input voltage gets less than 12V(input) ? .Quote from: Vovk_Z on April 22, 2020, 11:57:58 amThank you sir for sharing your time and insight, do you think i might experience any problems if the input voltage gets less than 12V(input) ? .

author: Sultanpepper123
author_rank: Regular Contributor
timestamp: April 22, 2020, 12:16:03 pm
content: Quote from: blueskull on April 22, 2020, 12:11:57 pmThank you sir , really appreciate it
isolated dc/dc converter input capacitors and output ferrite beads  - Page 1
Forum section: electronics / beginners

author: V_King
author_rank: Regular Contributor
timestamp: March 04, 2019, 01:55:01 pm
content: Hello,I want to incorporate 3x isolated dc/dc converters to give me galvanic isolation and all required voltages for a small control board.I have two questions as follows:1. For power inputs, the manufacturers recommends certain capacitor values, but if I have three DC/DC converters in parallel, do I put same value capacitor in front of each dc/dc converter, or do I put one same value or bigger cap? All manufacturers give max input/output capacitances, so I want to avoid instability issues.2. Same for the power input fuse as above. Do I triple the current requirement, or put three fuses for each of the DC/DC converters3. Finally, I've read application note from analog devices, recommending to use ferrite beads after dc/dc converter and LDO to reduce the ripple and noise. Application note says the ferrite bead impedance @ freq. must be matched to the dc/dc converter switching frequency. But all dc/dc converters I find are around 100kHz and ferrite beads rated at 25MHz and above. have I misread something, or am I looking at the wrong ferrite beads? Or in real life, a few paralleled caps should do the trick?The power supplies are going into powering op-ams and ADC analogue side.Thanks
Isolated Flyback with PWM controller  - Page 1
Forum section: electronics / beginners

author: GuilTy
author_rank: Contributor
timestamp: June 12, 2016, 06:15:27 pm
content: I have a Flyback converter, which is isolated, and I want to design the PWM controller which controls the PWM of the transistor. I am using the K factor method. The input voltage is 15V and the output voltage is 3.3V. I am using an error OPAMP type 3. The output voltage is 3.3V. I've calculated the components of the OPAMP(resistors and capacitors) using matlab.I'm using a triangle signal asa a carrier, and the control signal is generated by the error OPAMP type 3. I believe that something is wrong with the control signal(printscreen attached). The control signal is the one with red.Can someone tell me if it is correct, or if it is not correct what have I done wrong and why the control signal looks like this?Thanks,G
Isolating a TO3 transistor from a heatsink - Page 1
Forum section: electronics / beginners

author: electronics man
author_rank: Frequent Contributor
timestamp: July 03, 2014, 04:51:38 pm
content: I am building a power supply and I am using a 2N3055 npn transistor as a pass transistor. I know I can isolate it from the heatsink using sil pads but the transistor must be screed to it however this would foul any isolation. How do I successfully isolate the transistor from the heatsink?

author: Jorpy
author_rank: Contributor
timestamp: July 03, 2014, 05:00:21 pm
content: You can either use nylon screws or go for shoulder washers

author: mariush
author_rank: Super Contributor
timestamp: July 03, 2014, 05:02:58 pm
content: Just like you isolate to-220 devices.Rubber or plastic tubes/spacers that would separate the screws from to-3 package:http://uk.farnell.com/multicomp/3-38-32gfn/bush-to-3-pk10/dp/936637You drill hole in the heatsink that's larger than the diameter of this plastic tube, you put two of these in the holes of the to-3 and now the metal screw doesn't touch the to-3 package.

author: electronics man
author_rank: Frequent Contributor
timestamp: July 03, 2014, 05:05:31 pm
content: Quote from: mariush on July 03, 2014, 05:02:58 pmthe heatsink i am using is predrilled

author: wraper
author_rank: Unknown
timestamp: July 03, 2014, 05:08:03 pm
content: And if transistor dissipate a lot of heat better use mica pad + thermal paste as it will give much better result.

author: mariush
author_rank: Super Contributor
timestamp: July 03, 2014, 05:12:36 pm
content: So make the holes larger or cut the spacer to the thickness of the to-3 case, you're only interested in not allowing the screw to touch the to-3 package, the screw can touch the heatsink.If you can't imagine it, you have below a picture showing to-220 packages insulated from heatsink.. first and third have that spacer that stop the screw from touching the metal pad of the chip, the spacer doesn't go through the heatsink, it goes just deep enough to touch the sil pad..btw here's something cheaper but they only come with one spacer, but you can get lots of those for the price of the pack i linked to above:http://uk.farnell.com/multicomp/mk3301/insulating-kit-mica-to-3/dp/520172
Isolating battery from circuit during charging - Page 1
Forum section: electronics / beginners

author: Phaedo
author_rank: Contributor
timestamp: April 04, 2023, 05:30:58 am
content: Hello,I have a circuit which is powered by a 12V(1.3 Ah) rechargeable battery. I want to disconnect the battery from the circuit when it is being charged.I want to use the idea with the DC jack mentioned here :https://www.eevblog.com/forum/beginners/isolating-battery-input-from-dc-jack-input-on-a-pcb/So when I plug in the charger jack the battery will get charged, while the circuit is disconnected ( by disconnecting the negative ) . Is there any downside to this approach ?Any circuit ideas for providing a LED indicationONLYwhen the charger jack is plugged in , so that the user is not left in the dark as it were.

author: Peabody
author_rank: Super Contributor
timestamp: April 04, 2023, 02:41:20 pm
content: The more typical setup would have the external power source recharging the battery and powering the load at the same time, so the user would have no downtime. Could you provide more information about your power source, charger, and circuit?

author: Phaedo
author_rank: Contributor
timestamp: April 05, 2023, 04:18:02 pm
content: Hello Peabody,Thanks much for replying.QuoteIt is not so important that, though it might be useful. Predominantly the product will be used in battery power.I am using a LT1117 to derive 5V from the 12V SLA battery. LT1117 (5V) has a absolute maximum of 15V , so I wanted to avoid charging the battery and powering the circuit simultaneously.The charger is one of those COTS wall wart chargers.The LT1117 during operation will power a microcontroller (MS51PC0AE) and 16x2 LCD with a backlight. There is a pressure transducer with a 4-20mA , which will be powered directly from the battery, it is rated for a maximum of 30V.I am just gathering ideas, not yet drafted a schematic as of now.Do let me know if I have missed anything.
Isolating battery input from dc jack input on a PCB - Page 1
Forum section: electronics / beginners

author: sean87
author_rank: Regular Contributor
timestamp: August 03, 2016, 01:03:11 pm
content: I want to design a PCB which gets powered from 6xAA batteries or a 9v wall adapter. I am wondering how to isolate these 2 supplu inputs from eachother, so that only one should work? I was thinking about some diodes but how?

author: Ian.M
author_rank: Super Contributor
timestamp: August 03, 2016, 01:14:03 pm
content: The usual approach is to simply connect the battery negative via the switched contact on the jack. When the DC jack plug is inserted the batteries are automatically disconnected.

author: Buriedcode
author_rank: Super Contributor
timestamp: August 03, 2016, 01:15:06 pm
content: Several options. The most common for battery/DC jack powered devices is to use the DC socket's normally closed switch to route the ground of the battery to the ground of the circuit. When a plug is plugged in, this is disconnected and the outer connection of the DC plug is connected to circuits ground - disconnecting the battery.Other options are, use a diode on each power input with their cathodes connected - the higher voltage supply with be the one that powers the circuit. The downside with that is, you'll lose ~0.6V (~0.2-0.4V for schottky diodes) of the battery voltage, which for portable applications just reduces battery life/efficiency.https://tangentsoft.net/audio/cmoy/bitmaps/diode-or-bridge.pngMore complicated (but still straightforward) options are to use a P-channel MOSFET on the battery input, with its gate pulled down to ground with a resistor. The gate can be pulled 'high' (so the FET is off) when power is applied to the DC jack, using transistors to invert the signal.Like i said, many ways to do this, its a question of efficiency, cost, but by far the most common is using a DC socket with switch:

author: Brumby
author_rank: Unknown
timestamp: August 03, 2016, 03:41:09 pm
content: Quote from: Ian.M on August 03, 2016, 01:14:03 pmQuote from: Buriedcode on August 03, 2016, 01:15:06 pmThe switched socket has been around for decades. Easy solution with effective isolation of the batteries when the adapter plug is inserted. Not fancy, just effective.

author: johnkenyon
author_rank: Regular Contributor
timestamp: August 05, 2016, 02:31:35 pm
content: Quote from: Brumby on August 03, 2016, 03:41:09 pmWith the added advantage that for many power connectors you get the functionality for free, or for no more than pennies compared to an unswitched connector.
isolating i-v amplifier output from scope input - Page 1
Forum section: electronics / beginners

author: gus789
author_rank: Contributor
timestamp: March 28, 2015, 11:31:39 pm
content: Hi I'm running into a problem with a current to voltage amplifier (an old commercial unit from Dagan with gain ~ 1V/nA). I am monitoring square current pulses through a 1GOhm resistor by going from the amplifier output to the oscilloscope (agilent 54600) with a 1ft long bnc cable. The pulses look as expected (square waves) down to 200mv/div on the scope, but at lower mv/div the pulses show severe (damped) ringing. I suspect that the input capacitance of the scope is changing as I go below 200mv/div, and that the change doesn't play well with the i-v amplifier output. Does anyone know of a way to eliminate this problem? A friend mentioned that there are ic's out there that can drive arbitrary capacitive/inductive loads while always presenting a fixed impedance to the amplifier output - any ideas as to the part no for such an ic? Thanks!

author: ConKbot
author_rank: Super Contributor
timestamp: March 29, 2015, 12:50:08 am
content: Try using your scope probe instead of a bnc cable snd see if it improves. Or if the amplifier allows it, use 50 ohm termination on the scope. What sort of pulse rates / rise times are you looking at? It may give more of a clue as to what could be the problem.

author: gus789
author_rank: Contributor
timestamp: March 29, 2015, 02:34:09 am
content: Thanks - indeed using a 10X probe seems to fix the problem, at the expense of extra noise. I will try and find a 1x probe to see if that helps. The bandwidth of the amplifier is 10kHz (can be set to lower by changing an output filter setting but changing it does not seem to affect the ringing problem) and I am looking at pulses with < ~500us rise and fall times. 50 Ohm termination is not supported by the amplifier (put a termination in and it removes the ringing but also changes the V/nA scaling). I think I found the ic I refer to in the previous post - LT1010 - Fast 150mA Power Buffer.
Isolation between logic and high voltage traces and grounds - Page 1
Forum section: electronics / beginners

author: Pack34
author_rank: Frequent Contributor
timestamp: September 03, 2015, 10:10:07 pm
content: I have some 150V traces on a circuit board that's being controlled with 5V logic and op-amps. For the higher voltage lines, I have the ground piped through the boost converter so I have a controlled path for the return current. I wanted to keep everything as low noise as possible and felt that the return for something like this going under my analog circuitry would be bad news. They both share a common ground, but that just doesn't meet until the input (star configuration). I also wanted to isolate the switching boost converter as much as possible.How much isolation is enough? We're talking about <1mA of current and I've setup a solid 15mil isolation but I just wanted to be that it's enough before I had it made. This is the first time I'm working with voltage this high and wanted to be sure to keep noise to a minimum.Any advice?

author: fivefish
author_rank: Frequent Contributor
timestamp: September 03, 2015, 10:27:41 pm
content: Why not use an optocoupler?

author: Chris C
author_rank: Frequent Contributor
timestamp: September 04, 2015, 01:14:14 am
content: In terms of preventing arc-over, here's an article on the topic, which also provides a handy calculator:http://www.smps.us/pcbtracespacing.htmlFor 150V peak, a bare metal trace requires 24 mils clearance. If coated (solder resist), 16 mils. If there are any holes in the solder resist, use the higher number near those holes.If AC line powered, consider if a spike might drive your peak voltage higher, and adjust as needed. A MOV might be a good idea to limit the possible peak voltage.

author: Pack34
author_rank: Frequent Contributor
timestamp: September 04, 2015, 01:48:22 pm
content: Quote from: Chris C on September 04, 2015, 01:14:14 amThat is precisely what I was looking for! Thanks Chris!