hybridfree/eevblog-posts huggingface dataset:
Question on Calibration - Voltage Energy meter - Page 1
Forum section: electronics / beginners

author: Freshman
author_rank: Regular Contributor
timestamp: June 17, 2024, 11:41:21 am
content: I have this ATM90E26AS - Energy metering IC and this is the application note that decribes the process of calibration. (https://ww1.microchip.com/downloads/aemDocuments/documents/OTH/ApplicationNotes/ApplicationNotes/Atmel-46102-SE-M90E26-ApplicationNote.pdf)In this application note, on page 14, we see the steps they mention to calibrate the voltage.Ugain = ((24600 x Un)/(Vol_mea))So, as far as I understand, Ugain is a register and Urms is another register.As far as I understand, when the ATM90E26 is initially powered, there's some default value in the Urms register.Now, based on the input voltage that is given (220.024V, as given as an example in the application note), there will be a different value provided by the Urms register.Converting this Hex value from the Urms register to Voltage (as described in the app note), I can obtain a value which can be converted into Hex. And this is the final Hex value that needs to be written into the Ugain register for calibration. Please correct me if I am wrong.My question is,1. How can this approach be termed as calibration? I am given some voltage (220.024V) and just writing that in a register. I am not comparing or validating this 220.024V voltage value against any standard reference. I am also not conveying to the IC that this final Hex value which is being written into the UGain register corressponds to 220V. In that case, how is the calibration process termed as correct? Am I missing something to understand?

author: aliarifat794
author_rank: Regular Contributor
timestamp: June 19, 2024, 02:17:56 pm
content: You must apply a known and accurate voltage (220.024V in your example) to the IC. This accurate input voltage serves as your standard reference. By reading the raw value from the Urms register and using the known accurate input voltage to calculate the Ugain value, you are effectively calibrating the IC. The Ugain value adjusts the IC's internal scaling so that future measurements will be accurate. The accurate input voltage (220.024V) acts as a reference point. By applying this voltage and adjusting the IC’s measurements to match this reference, you are calibrating the IC.

author: kevin.gibbs
author_rank: Regular Contributor
timestamp: December 04, 2024, 02:55:50 pm
content: Obviously, a reference instrument is needed for calibration.1. In the example, 220.024 is the actual voltage measured by the reference instrument.2. 246.01 is the value measured by the ATM90E263. From this data, we calculate the correction, which we write to the Ugain register (31H)This is how I personally read it.
Question on capacitor voltage droppers in small power supplies - Page 1
Forum section: electronics / beginners

author: cravenhaven
author_rank: Contributor
timestamp: February 26, 2018, 03:24:35 am
content: I have just been repairing a couple of small 'embedded' power supplies that use a capacitor as the primary voltage dropper before rectifying and regulation. I notice that they commonly consist of a capacitor of about 0.5uf in series with a 2W resistor of 100+ohms and a diode and zener. What is the purpose of the resistor, why not just rely on the capacitor?. By my calculations the capacitor has an impedance of around 3-4Kohms @ 50Hz so what value does another 100 or so ohms add ?.ie:

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: February 26, 2018, 03:46:47 am
content: Limit inrush current.Transients.
Question on Class D amplifier high side  - Page 1
Forum section: electronics / beginners

author: poorren
author_rank: Newbie
timestamp: March 15, 2019, 03:59:10 am
content: Hello guys,Here's a design for driving sensor. To achieve high efficiency, I choose class D amplifier.The capacitive load will be driven by two complementary pulse, with 40us period, 20us phase offset, 2us pulse width. (V1 and V3)In ideally, the charge will be push forth and pull back from load.The issue now is the high side pmos could be switched on instantaneously.Based on simulation result, the pmos's drain will be pulled down when the high pulse is applied on Q5. (the high side is switch off before this moment.)The parasitic capacitor between drain and gate will pull down the voltage on gate, it's about ~23V (See attachment 2), and switch on pmos.Because the only charge path to this capacitor is through 20k resistor (R3), so, this errornous switch on period is relative long. And this will lead to large current and lots of heat.Note: I have add some circuit to help high side pmos accelerate switch off speed (Q3), but these couldn't help for this case.I wonder if there's way to avoid this behavior and keep high side pmos be queit and cool.Thanks advance!

author: Zero999
author_rank: Super Contributor
timestamp: March 15, 2019, 11:49:36 am
content: Where is the load? There's nothing to limit the current through C2. All that will happen is it'll pass large current spikes, which will heat up the transistors.As far as the dead time is concerned, why not just use a class D amplifier IC or half bridge MOSFET driver IC?

author: poorren
author_rank: Newbie
timestamp: March 19, 2019, 04:43:14 am
content: The load is a piezo ultrasonic transducer, so, I choose to model it with Butterworth-Van Dyke model, ie., C2//(R10-L10-C3). The real value is picked up from Murata's datasheet.The goal of my design is to drive transducer with high voltage (~200V) and fast slew rate pulse, while the output power is not high, several Watt.Because the input signal is pulse, which inherently looks like PWM, so the class d circuit is my first choice. And the final design would be full bridge driver to further lift the power.When I tried to design this circuit, I didn't find any class d power amplifier ic which could support such high voltage. The catelogue I searched is audio class d amplifer. Maybe I missed something, and went the wrong way. However, those audio power amplifier (Class AB or class D) are designed for high power, not for high voltage.Is there any off-the-shelf product for this design? I noticed tons of half bridge MOSFET driver for power supply, and I'm not sure if those drivers are suitable here.Anyway, thanks advance!!!The question for circuit now is when I switch on low side mosfet, the high side mosfet will errornous switch on, which waste lots of power and slow the discharge process. And I haven't find a way to eliminate it.
Question on Current Mirror - Page 1
Forum section: electronics / beginners

author: hurricanehenry
author_rank: Regular Contributor
timestamp: March 15, 2017, 12:20:08 am
content: Hihttps://en.wikipedia.org/wiki/Current_mirrorI am wondering why it works. It seems flawed.The transistor on the left side, has base current coming through Iref.Since Iref splits the current between its NPN collector, and its base, AND the base of the NPN transistor on the right-hand side, it seems there is adeficitof current.I would understand it a bit better if the two transistors were FETs but they are BJTs and thus they draw current into the base.So why would the output current exactly mirror Iref, if the base of the output NPN is using a bit of current from Iref?

author: David Hess
author_rank: Super Contributor
timestamp: March 15, 2017, 01:14:05 am
content: Quote from: hurricanehenry on March 15, 2017, 12:20:08 amThe output current is not exactly the input current for the reason you identify; the base current contributes an error. In many applications this error is either insignificant or overwhelmed by other errors. There are refinements of this circuit which compensate for the base current error.https://en.wikibooks.org/wiki/Circuit_Idea/How_the_Wilson_current_mirror_equalizes_the_currentshttps://en.wikipedia.org/wiki/Wilson_current_mirrorhttps://wiki.analog.com/university/courses/electronics/text/chapter-11

author: hurricanehenry
author_rank: Regular Contributor
timestamp: March 15, 2017, 02:41:17 am
content: Thanks very much.I had been bothered by this for a long time because its name is "mirror" and most people I talked to seemed to think it did just that. So I was worried I didn't understand it or something, even though it violates KCL.I will check on the enhanced circuits you posted.

author: hurricanehenry
author_rank: Regular Contributor
timestamp: March 15, 2017, 02:49:59 am
content: Ok I got it. The Wilson version is definitely better.It first takes in base current from the reference, and then gives it back out, equally (assuming ideal and equal transistor gains).

author: w2aew
author_rank: Super Contributor
timestamp: March 15, 2017, 06:38:22 pm
content: Here's a video I did on current sources and current mirrors.

author: lordvader88
author_rank: Frequent Contributor
timestamp: March 16, 2017, 06:51:27 am
content: If there's a university library close by, visit it. The other day I was skimming through a whole book on current mirror's and reference voltages, and they had a few books on that.I copied down a few circuits to experiment with, but haven't made the time yet.
Question on digital isolator - Page 1
Forum section: electronics / beginners

author: Freshman
author_rank: Regular Contributor
timestamp: October 08, 2024, 10:46:27 am
content: I am using this IC for Isolated CAN interface (https://www.nve.com/Downloads/il5xx.pdf) - IL514E.My question is, we are giving 3.3V to VDD1 and isolated 5V to VDD2. Whether there's an internal level shifter? Or is VDD2 a supply output?Also, can this isolator support CAN-FD speeds?

author: Andree Henkel
author_rank: Regular Contributor
timestamp: October 08, 2024, 11:07:30 am
content: you need to give 2 supplies, if they are of different level, then the isolator does level shifting too.I don´t know the requirements of CAN-FD,but IL514 datasheet says:2M Bit per Second max data rate - is what it can provide25ns propagation delay - which may matter in some corner circumstance in case you are doing bidirectional over longer cable and maybe have additional latency10ns pulse distortion should not matter as 2MB at 50% duty cycle is 250ns pulse length

author: Terry Bites
author_rank: Super Contributor
timestamp: October 10, 2024, 02:58:45 pm
content: Either side can be powered from 3.3 or 5V or 3.3 on one side and 5V on the other. What ever suits you.Its a really crap data sheet in this respect with no real information on powering it.You need to power both sides of the isolator with supplies that are isolated from each other.The isolator output levels will depend on the choice of Vdd2.

author: Nominal Animal
author_rank: Super Contributor
timestamp: October 10, 2024, 06:46:07 pm
content: I prefer to use TI ISO67xx (1.65V to 5.5V, 50 Mbits/s) or ISO77xx (2.25V to 5.5V, 100 Mbits/s) isolators, especiallyISO6721andISO7721having one channel in each direction. The datasheets (linked, PDFs) are rather clear in my opinion, as a hobbyist myself.Each side requires their own isolated supply, referenced to the signals on that side, defining the voltage levels on that side. Each side also has their own ground, to which the supply and signals are referenced to.You need to add a 0.1µF = 100nF X7R/C0G/NP0 capacitor between each supply and ground, but that's it. CAN is explicitly mentioned as one use case. Mouser sells these for under 1€ apiece in lots of 100 or more, so they're not that expensive either.The two last digits specify the number of channels and the number of channels in the 2-to-1 direction. Add a Q suffix for automotive versions.
Question on grounding PSU - Page 1
Forum section: electronics / beginners

author: ChrisLX200
author_rank: Unknown
timestamp: February 10, 2018, 02:38:14 pm
content: OK so I'm putting together a PSU consisting of a 48V Mains supply, and a DPS5015. The input to the 48v supply is obviously L & N and whilst there is a third terminal there is no connection from it to anything on the PCB, so the wire from the mains input I will use to ground the chassis. On the output of the 48v supply there is + and - plus a GND terminal, but the input to the DPS5015 just has +IN and -IN. So is this GND left unconnected? I added some pics which may help... Thnx
Question on high-bandwidth DIY 21:1 scope probes - Page 1
Forum section: electronics / beginners

author: comfortcube
author_rank: Contributor
timestamp: September 10, 2021, 08:56:08 pm
content: I've seen in more than a few places now something like this:http://jahonen.kapsi.fi/Electronics/DIY%201k%20probe/In the places I've seen, it's always a 1k or 950ohm in series with the source, which gives 21:1 or 20:1 division when the scope input is 50ohm terminated. However, I'm just wondering if there's good reason to this choice of ratio? Like say 20:1 division would be too much for the signals I'm looking at and I don't have a low-noise pre-amp at hand (can be made ofc) - then would say a 10:1 ratio work - i.e., 450ohm instead of 950? Or 50ohm, to get 2:1? Or what about just straight probing with no discrete resistances other than the 50ohm terminator?I'm guessing the biggest factor here is loading of the source? And 950ohm/1k is kind of a balance between loading the source and voltage division ratio?

author: iMo
author_rank: Super Contributor
timestamp: September 10, 2021, 09:10:46 pm
content: A discussion on it is herehttps://www.eevblog.com/forum/projects/cheap-wideband-121-oscilloscope-probe-for-logic-signal-applications/

author: David Hess
author_rank: Super Contributor
timestamp: September 10, 2021, 11:07:24 pm
content: 450 ohms for a 10x probe has a load resistance which is a little too low for most applications and 4950 for 100x has too much attenuation and problems with compensation, so 20x is a better choice if the weird multiplier is acceptable.

author: comfortcube
author_rank: Contributor
timestamp: September 10, 2021, 11:38:52 pm
content: Oh I gotta get better at searching! I had tried "DIY scope probe" and "DIY high-bandwidth probe" but couldn't find what I was looking for. Maybe I was blind too, that's entirely possible. Thanks!

author: tggzzz
author_rank: Super Contributor
timestamp: September 11, 2021, 08:02:50 am
content: Quote from: comfortcube on September 10, 2021, 11:38:52 pmThere are links to a few other DIY probes here:https://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/
Question on oscillators ? - Page 1
Forum section: electronics / beginners

author: wael
author_rank: Contributor
timestamp: October 10, 2017, 09:19:29 pm
content: Hi,I'm trying to understand the attached oscillator , when i removed the R2 resistor it stopped oscillating ,(don't know why)My question is :1. How to simply understand/analyze such circuits ?2. Why removing the R2 makes it stop oscillating ?3. Changing the Q2 PNP have a very strange effects ?4. Also changing the inductor to a resistor has a strange effect ?Attached is a ltspice circuit if you wish to test it.Regards,Wael

author: ataradov
author_rank: Super Contributor
timestamp: October 10, 2017, 09:46:16 pm
content: 1. Just follow each transistor on their own.2. You are removing the feedback loop by completely removing R2.3. If you are changing it 1:1 (just plug a different transistor into the same circuit), then you are violating basic transistor use principles, so I'm not sure what you have expected?4. Inductor is a timing element here, so changing it to a resistor will just make this circuit go into some sort of stable state, or some sort of oscillations depending on stray capacitance and inductance. LTSpice may not be able to simulate this accurately.

author: wael
author_rank: Contributor
timestamp: October 10, 2017, 09:59:52 pm
content: Many thanks, but could you explain how this feedback works, i know that since it's pnp it's on, i don't get why it gets off.

author: ataradov
author_rank: Super Contributor
timestamp: October 10, 2017, 11:00:53 pm
content: In a steady state, L2 is a short, so Vb(Q2) is V1 / 2 because of the R1/R2 divider. This is enough to keep Q2 open, but that also opens Q1, which tries to pull Vb(Q2) to ground, but L resists this change, creating delay. Eventually Q2 will close, which will close Q1, and R1+R2 will start charging the inductor, which it will also resist. But eventually Vb(Q2) will rise again, and the cycle repeats.Attached is a bit easier to read version of the schematic.

author: medical-nerd
author_rank: Regular Contributor
timestamp: October 11, 2017, 08:51:27 am
content: HiyaThank you atarodov for explaining why the circuit would oscillate, can you explain the purpose of the diode across the inductor please?Cheers

author: wael
author_rank: Contributor
timestamp: October 11, 2017, 09:09:40 am
content: Hi,The diode in this configuration is to eliminate flyback (voltage spikes when the magnetic field collapses), it's a flyback diode.Regards,Wael

author: medical-nerd
author_rank: Regular Contributor
timestamp: October 11, 2017, 11:08:06 am
content: HiyaMuch obliged, I've only looked at typical rf oscillator circuits so far. I'm familiar with their flyback use in relays and it did look familiar. I didn't realise that they were used in oscillators for this purpose as well.Cheers

author: ataradov
author_rank: Super Contributor
timestamp: October 11, 2017, 04:19:33 pm
content: Quote from: medical-nerd on October 11, 2017, 11:08:06 amEven in this simulation you can see that V(ind) is ~1.5V + 0.7V = 2.2V. Where 0.7V is a diode forward voltage.
Question on Oscilloscopes - Page 1
Forum section: electronics / beginners

author: OzTech
author_rank: Newbie
timestamp: January 11, 2015, 08:39:12 am
content: Dear EEVBlog communityWould just like to ask a question on whether the Hameg Analogue Oscilloscopes are a good brand. My University is giving me some as they are going to throw it away or donate it. They are willing to give me one. I will take it no matter what the answer is. So Are Hameg a good brand of Oscilloscopes? I do not know the specs sorry!Will I be able to learn and teach myself how to use one with the older analogue oscilloscopes? Apparently they are harder to use.PS: Are they worth any profit?Thank you.

author: tautech
author_rank: Super Contributor
timestamp: January 11, 2015, 09:21:38 am
content: Hameg is a well reknown brand, by all means grab one.Check out the Oscilloscope training thread in the Beginners board.When you know just what you have, manuals should be available from one of the links in the Repair board.

author: OzTech
author_rank: Newbie
timestamp: January 11, 2015, 10:16:26 am
content: Thank you Tautech (that name simularity)All good! Will do. Cannot wait to use this old piece of technology

author: lapm
author_rank: Frequent Contributor
timestamp: January 11, 2015, 01:18:21 pm
content: Take it.... Universities usually have good stuff, thanks to having good money to buy stuff originally.
Question on output signals from spectrum analyzer - Page 1
Forum section: electronics / beginners

author: BravoV
author_rank: Super Contributor
timestamp: April 26, 2018, 12:34:00 am
content: My spectrum analyzer has these two output signals (quotes from the manual) :- IF OUT 10.7 MHzIF out is 50 Ohm, 10.7 MHz IF output that is the down-converted signal of the RF input of the analyzer. This output is taken after the resolution bandwidth filters and step gains and before the log amplifier.- VIDEOVIDEO out provides detected video output (before the analog to digital conversion) proportional to vertical deflection of the trace. Output is from 0V to 5V.Both also have this same description applied :Amplitude correction factors are not applied to this signals. The output signal will be blanked occasionally during retrace by the automatic alignment routine.When or where to use these signals usually ?

author: w2aew
author_rank: Super Contributor
timestamp: April 26, 2018, 12:59:20 am
content: Quote from: BravoV on April 26, 2018, 12:34:00 amOutputs like these aren't used very often, but here's an example for each that I've seen used over the years. These examples would be used in Zero Span mode.The IF output can be connected to a receiver for demodulation, using the SA as a tuner.I've seen the video output connected to strip-chart recorder to track the long-term variation of a particular signal's amplitude.

author: BravoV
author_rank: Super Contributor
timestamp: April 26, 2018, 02:05:56 am
content: Quote from: w2aew on April 26, 2018, 12:59:20 amGreat, really never thought of that on my SA. As mine capable of AM & FM demodulation, am I correct if it can be used sort of wide band snooping on analog radio signal ? CMIIWQuote from: w2aew on April 26, 2018, 12:59:20 amOk, I can't think of the practical use for this, at least for me for this moment.Thank you for the answers Alan.

author: dmills
author_rank: Super Contributor
timestamp: April 27, 2018, 01:01:32 pm
content: Those outputs are a bit like the Z axis input on a 'scope, not something you need often, but when you do need it you are very glad it is there.Same thing with sweep trigger input on an SA or VNA and the DC bias inputs on a VNA test set, they let you do things otherwise impossible or very difficult, but those things are a once in a blue moon sort of thing.Regards, Dan.

author: BravoV
author_rank: Super Contributor
timestamp: April 28, 2018, 04:44:48 am
content: Quote from: dmills on April 27, 2018, 01:01:32 pmDan, which one exactly ?As enthusiast, could you can give an example specific case on this measurement ?Quote from: dmills on April 27, 2018, 01:01:32 pmDo you mean ports like these two labelled "Ext trig" & "Swp Gate" ?
Question on Resistors (Compound) - Page 1
Forum section: electronics / beginners

author: codemonkeyrawks
author_rank: Contributor
timestamp: July 18, 2018, 04:05:02 am
content: I have a quick question about Metal Oxide Resistors:A repair project (amp) I am working on calls for a 3W (10Ω RSS P type) Metal Oxide Resistor. Looks like it needs to be around 200 F at most I was curious what the "RSS P-Type" is referring to. Does anyone know where I might find two resistors in matching up.

author: Jwillis
author_rank: Super Contributor
timestamp: July 18, 2018, 05:39:15 am
content: RSS are small sized metal oxide film resistors.Metal oxide handle higher temperatures than carbon or thin film . For example a 1/2 watt RSS is the same size as 1/4 watt RSF. I believe P type resistors increase resistance as the temperature rises. So really what your looking for is 3 W metal oxide resistor in a smaller form than a standard.

author: codemonkeyrawks
author_rank: Contributor
timestamp: July 18, 2018, 01:11:10 pm
content: I think I will see if I can find some online (tricky to find) - I could see this because of the tight spacing on the board I am working on and when I measure a few other's that are similar the temp sits around 160 F but they are also +73V and -73V rails vs being on +2V rail on the final output but at a high current.My best guess is that this acts as an overload :https://www.manualslib.com/manual/1132095/Alto-Pbm8-250-Mkii.html?page=16#manual- (R1_22) back into the circuit or a final filter stage.Thank you!
Question  on schematic snippit in Art of Electronics - Page 1
Forum section: electronics / beginners

author: Dan Moos
author_rank: Frequent Contributor
timestamp: June 06, 2023, 12:05:37 am
content: I'm looking at at figure 9.18 on page 610 of the third edition. Voltage regulator chapter.What is the purpose/function of Rc and Cc. The 'c' in the part reference suggests to me that this is a compensation filter, but if so, how does it work? From my understanding of what an lm317 looks like internally,this wouldn't be a miller cap.I also thought it might be a noise filter, which would make sense as it is a small signal controlling a large voltage, and noise error would be greatly amplified.Thanks!

author: barshatriplee
author_rank: Regular Contributor
timestamp: June 06, 2023, 07:55:23 am
content: Hi, I think you forgot to attach the picture.

author: armandine2
author_rank: Frequent Contributor
timestamp: June 06, 2023, 09:10:07 am
content: or thinks everyone has the pdf from the internet

author: srb1954
author_rank: Super Contributor
timestamp: June 06, 2023, 10:15:19 am
content: Quote from: Dan Moos on June 06, 2023, 12:05:37 amIt is for compensation of the control loop. Although the LM317 normally doesn't need external compensation this circuit adds extra loop gain, from the LM358, and extra phase shift through the DC-DC convertor so additional compensation is required to stabilise the overall feedback loop.The capacitor Cc rolls off the gain to reduce the loop gain at higher frequencies to give the feedback loop sufficient gain margin. Unfortunately, it also adds an additional 90 deg of phase shift which degrades the phase margin and hence the loop stability. The addition of Rc compensates for this by adding a zero in the compensation ultimately reducing the extra phase shift introduced by Cc and enhancing the phase margin.

author: Dan Moos
author_rank: Frequent Contributor
timestamp: June 07, 2023, 01:37:23 pm
content: Perfect answer! Thank you!
Question on selecting FETs - Page 1
Forum section: electronics / beginners

author: redgear
author_rank: Frequent Contributor
timestamp: October 01, 2019, 09:02:00 am
content: I am building a BMS based on one of Ti's reference designs --TIDA-00792.I need help choosing the right FETs for the charge and discharge control. I will be using a 7s pack with a nominal voltage of 25.9v and a maximum of 28.7v. My motor draws a max current of 15A and I don't expect the current to go more than 20A even after considering the other electronics.The above design I linked to uses twoCSD19536KTTin parallel for charge and discharge. The FETs are rated at 100v Vds with a continuous drain current of 192A at 100deg.I think this is a overkill for my system and increases the BOM cost.Do I really need two FETs in parallel to handle the current and heat?I am trying to hit a sweet spot between BOM cost and reliability.Is it ok to look for FETs rated for or above 60v(more than 2x my max) with Id more than 50A(more than 2x my max) ?I have shortlisted a few FETs, want to know which one to pick and how many(in parallel). I am open to suggestion outside this list too.Vishay Siliconix SQR70090ELR_GE3- 100v 50AVishay Siliconix SQD50034EL_GE3- 60v 68AVishay Siliconix SQM60030E_GE3- 80v 120AVishay Siliconix SQR97N06-6m3L- 60v 56AThanks
Question on USB Hub - Page 1
Forum section: electronics / beginners

author: Freshman
author_rank: Regular Contributor
timestamp: May 29, 2024, 12:09:02 pm
content: In this device checklist link:https://ww1.microchip.com/downloads...lateral/SchematicChecklistUSB2512BQFNRevA.pdfI see there are three different modes of configuring the VBUS_DET pin.My questions are :1. Does the self-powered, bus-powered, etc.. mean that the "Hub" is being self-powered or bus-powered? Or does it mean the "device" connected is self powered or bus powered?2. What is the purpose of VBUS_DET pin and what advantages are there in each configuration mode?

author: ataradov
author_rank: Super Contributor
timestamp: May 29, 2024, 01:51:14 pm
content: 1. This is obviously for the hub side. The diagrams don't even include the device ports.2. In the bus powered VBUS_DET is used to detect the actual bus voltage via a resistive divider. In the self powered mode it is just connected to the common 3.3V supply.The first case is when you use this as a regular hub with a USB connector on the host side. The second case is when you connect this hub to an MCU on the same board, for example. In this case there is not really a VBUS between the MCU and the hub.The device side VBUS is completely separate from any of this.
Question regarding display backlight - Page 1
Forum section: electronics / beginners

author: Freshman
author_rank: Regular Contributor
timestamp: August 28, 2024, 09:36:00 am
content: I have a display that mentioned LCD supply current and backlight current.To calculate the overall current required by the display, I hope adding both the above currents should be correct.However, while checking the LED Forward Current section, I see that for Iled, 0V/0% duty the current is high and for 100%duty, the current is low. Is this a typo? Or am I missing to understand something.

author: Rerouter
author_rank: Super Contributor
timestamp: August 28, 2024, 12:03:39 pm
content: At a guess its a derating curvee.g. it wont overheat at 50% at X current, so at lower duty cycles you can run higher current

author: tooki
author_rank: Super Contributor
timestamp: August 28, 2024, 11:45:28 pm
content: Quote from: Freshman on August 28, 2024, 09:36:00 amWe are not clairvoyant. You need to share the datasheet with us.
Question Regarding Pull down on Load Switch Enable - Page 1
Forum section: electronics / beginners

author: jayalt
author_rank: Contributor
timestamp: January 14, 2023, 06:05:50 pm
content: I have an MCU GPIO acting as the control pin to a load switch enable. The load switch enable is active-high, and therefore majority of the time I have the GPIO pulled low on the MCU side, and will enable the GPIO when I want to turn on the rail.I seem to have omitted a pull-down resistor on this particular rail. I’m a relative beginner, and I understand pull down/up resistors can help a pin always be in a defined state - I’m not so much concerned about this as my device is always on, and the MCU will always be controlling the pin.However, I’m a bit confused on the current path now that the pull down resistor is gone. Am I at risk of damaging my load switch if I drive the enable pin directly at VDD with no external resistor? How can I figure this out if so?

author: ataradov
author_rank: Super Contributor
timestamp: January 14, 2023, 06:28:18 pm
content: By drive directly to VDD you mean output high from the MCU? In this case there is no risk of damage. If you are driving a strong level from the MCU, then pull-up/down resistors are not doing anything. The goal of the resistor is to set a defined level while MCU is not actively driving the output.But overall details may depend on the switch. The switch may not like to have intermediate/undefined level and you will have that while MCU is starting up, for example.

author: joelaguirre92
author_rank: Newbie
timestamp: January 14, 2023, 07:02:36 pm
content: Hi jayaltIt s a good question because every time is important be carefully how we are using our MCU GPIO.Almost MCU have pull-up outputs. I mean every time the outputs are ON. I would need know what kind of MCU are you using to confirm that. In addition you can configurate by software the kind of pin outs using a register bits.If you are pulling up the MCU outputs you can connect this way.(MCU with pull up )I have seen many circuits controlling MOCs circuits that way, but you need be carefully what is the max current your MCU canR2 as looks in the picture, you should calculated. While MCU output is HIGH and EQUAL to V1 there are not current.It would be nice if you share us some diagram or schematic about how are you plugin.Hope you are wellmcu with pull up.png(7.8 kB. 529x426 - viewed 118 times.)mcu with pull up.png
Question regarding scope capture  - Page 1
Forum section: electronics / beginners

author: jayalt
author_rank: Contributor
timestamp: March 20, 2023, 09:15:13 pm
content: Trying to understand this difference I am seeing on my oscilloscope.I am debugging a marginal issue. I see a brighter-colored section at the beginning of power-on of my voltage rail via my oscilloscope. This is significant to me because it ONLY exists when the device goes on to later fail. I have attached the "passed" instance in comparison, where the voltage rail is duller in color.I'm trying to understand what the difference is that is resulting in this different/brighter color? This could potentially lead me to narrow down the root cause of my issue.When I try to zoom in, the waveforms begin to look exactly the same. But there is a clear difference when zoomed out.

author: m k
author_rank: Super Contributor
timestamp: April 01, 2023, 04:18:42 pm
content: My first guess is that it's a scope thing and nothing to do with the measured signal.
Question Regarding Switches - Page 1
Forum section: electronics / beginners

author: edb1984
author_rank: Contributor
timestamp: March 15, 2016, 01:53:06 pm
content: Hello AllPlease can someone be of assistance?i would like to make a switch box for my HIFI, i would like it to match some of my other vintage equipment but i cant really find anything like it in the commercially available units so i would like to do my own.i want to keep it very very simple and i have the ideas in my head but would like some help on the switches.i want a old fashioned style "clunky" latching switch for each channel.my question is - what is the switch i am looking for? i remember on old record players the kinds of switch that switched the input and as you pushed say "Tape" switch then the "Tuner" switch would pop out so both channels are not on at the same time.does anyone know what kind of switch this is and have a link to some more info on them? - i am happy searching for myself but i cant get started as i dont know what kind of switch i am looking for !Also, just as a afterthought - would i need to switch both left/right and earth from each input or would i keep earth common along all inputs and just switch the left/right channels?(Please forgive my ignorance an or lack of the correct terminology)Thank you in advance for any help

author: w2aew
author_rank: Super Contributor
timestamp: March 15, 2016, 03:05:05 pm
content: Sounds like you're looking for ganged push button switches, like these:(google: ganged push button switches)http://www.switchcraft.com/Category.aspx?Parent=655https://www.surplussales.com/switches/swpushb-2.htmlhttps://www.surplussales.com/switches/Closeups/swp-90084-B18_L.htmlhttps://www.westfloridacomponents.com/SW095APD/Gang+Switch+8+Position+Push+Button+4PDT+PSC84422.htmlhttp://www.surplusgizmos.com/Comax-6-Gang-Push-Button-Switch-25v-DC-1-Amp_p_2514.html

author: alanb
author_rank: Frequent Contributor
timestamp: March 15, 2016, 03:06:48 pm
content: http://uk.farnell.com/multi-station-switchesThis may be what you are looking for.

author: edb1984
author_rank: Contributor
timestamp: March 16, 2016, 01:10:37 am
content: GREAT !!!! that was just what i was looking for! thanks Guys!
Question regarding two scopes - Page 1
Forum section: electronics / beginners

author: dmkfeatf14
author_rank: Newbie
timestamp: February 23, 2019, 06:57:25 am
content: Hello eeevblog family,I was given two scopes and don't know which one I should keep and donate the other.These are the two scopes that I was given:Tektronicx 2215Phillips/Fluke PM3375Which one should I keep? They both work and the one that I keep will be my very first scope that I use and own.TIATom

author: Shock
author_rank: Super Contributor
timestamp: February 23, 2019, 07:47:42 am
content: Keep both, if you upgrade to a more modern digital storage oscilloscope or a better analog oscilloscope later you can replace them.

author: Ian.M
author_rank: Super Contributor
timestamp: February 23, 2019, 09:39:34 am
content: TheTektronix 2215is a good quality 60MHz dual channel delay timebase CRO that you are likely to be happy with as your main analog scope for years to come. As delay timebase CROs in good condition are becoming harder to find at a reasonable price you'd be stupid to let it go.The Philips PM3375 is an ageing MSO, from the era before DSOs were good enough to stand on their own without falling back on operating as an analog CRO. Its digital side has only 4096 8 bit words of sample memory shared between both channels, and its 100 Msamp/s max sample rate limits its effective digital bandwidth to about 10MHz. The added complexity of its digital side will make it much harder to keep in good working order long-term.Although the PM3375 has slightly better analog specs than the 2215, its let down by the complexity of its digital controls and the lack of a analog delay timebase with vernier controls. Its certainly better than no scope at all, or a low end 20MHz CRO or bargain basement USB or handheld DSO, but I wouldn't keep it a day longer than it took to acquire a reasonably modern DSO (USB or standalone) with more sample depth and the capability to export data and screeenshots, then find it a scopeless new owner.Learning to 'drive' a classic analog CRO like the 2215 will help you understand the use of scopes in general, and should stand you in good stead in future adventures with modern DSOs.

author: David Hess
author_rank: Super Contributor
timestamp: February 23, 2019, 10:20:39 pm
content: Keep them both and put the one you are not current using in an out of the way closet or shelf as a backup since they are both old.

author: dmkfeatf14
author_rank: Newbie
timestamp: February 24, 2019, 04:44:51 am
content: Thanks everyone for your valuable suggestion, I have decided to keep the Tektronix 2215 and donated the Phillips PM3375.
Question related to "Do I need to use optical isolators to connect two probe.." - Page 1
Forum section: electronics / beginners

author: nzo
author_rank: Regular Contributor
timestamp: September 22, 2015, 05:13:05 pm
content: I came across theseUSB isolatorson EBay recently, manufactured byAnalog Devices. Here's what they look like and this is the circuit for them. Might such a device help withNeverDie'sproblem? Haven't tried them myself yet. What do you think?Thanks all.

author: michaeliv
author_rank: Frequent Contributor
timestamp: September 22, 2015, 06:07:58 pm
content: No this wouldn't help.USB isolators isolate digital signals with a common ground.That scenario is about measuring 2 analog signals that do not share a ground - so basically 4 analog signals(or maybe 3) to a common ground and then doing some subtractions on that ... if that makes sense.But if instead of a digital isolator you would have an analog isolator .. then that would be a differential probe .. and you could use 2 of them to measure that scenario.

author: jitter
author_rank: Frequent Contributor
timestamp: September 22, 2015, 06:13:31 pm
content: Quote from: nzo on September 22, 2015, 05:13:05 pmI have worked with exactly this IC in a USB-interface to create galvanic separation between the device and the PC.It works OK, but one thing to keep in mind is the limited speed. Even though it's compatible with USB 2.0, max speed is "full" (i.e. 12 Mbps).Here'sthe datasheet.No, it won't help with that particular problem. In that thread a single scope is used to simultaneously probe two signals which do not have a common reference. All channels on a scope (except maybe a few handhelds) have all channels connetcted to the same reference, which in turn is connected to safety earth.The USB isolator only creates a separation between e.g. a USB device and a PC.
Question relating to delaying 555 timer pulse - Page 1
Forum section: electronics / beginners

author: krappleby
author_rank: Contributor
timestamp: March 24, 2020, 10:04:44 pm
content: Hi everyone,im a beginner in electronics, and im currently working on a project and need a little bit of advice. I have a 555 timer circuit which creates a pulse, i need to break that pulse into two seperate signals, however the 2 set of pulses need to be delayed by 5 pulses...for example1 2 3 4 5 6 7 8 9 etc0 0 0 0 1 2 3 4 5 etcany ideas on the best way to do that.. I was debating using some sort of logic and relay, but im sure there is an easier method.once the fifth pulse on the first signal is recieved, i need the second set of signals to activate from then on as well.. so both lines will be creating a pulse from the 555 timer, but the second line cannot start until the first five pulses have been processed..thank you for your timekeith

author: TerminalJack505
author_rank: Super Contributor
timestamp: March 24, 2020, 11:33:51 pm
content: Here's one possible way to do it. (See attached.)

author: krappleby
author_rank: Contributor
timestamp: March 24, 2020, 11:46:12 pm
content: Quote from: TerminalJack505 on March 24, 2020, 11:33:51 pmHi I understand most of this but what is the CP1 Low (pin)i can see how this would register 1 pulse at Q4, but what is the CP1 pin..? is that some sort of lock?and what would that IC be, as looking at decade counters i cant see one with a second clock pulse pin.. cheers

author: TerminalJack505
author_rank: Super Contributor
timestamp: March 24, 2020, 11:58:25 pm
content: The IC is the 4017 decade counter. You could also use a 4022.That is the Clock Inhibit pin. Pin 13. (I'm not sure why it has that name in the simulator.)If the pin is held high then the counter won't advance. So, once the counter gets the 5th pulse it will stop counting and the Q4 pin will remain high.
Question:  Solar panel discharging  battery - Page 1
Forum section: electronics / beginners

author: Jiimbo
author_rank: Newbie
timestamp: August 12, 2023, 06:35:00 pm
content: Hi From CanadaI'm a retired Printing Press mechanic but very much lack any electronic knowledge so please be gentle with meI bought a 2.5 watt solar 12 volt battery about 6 years ago and it did the job until the sun went down then it started to discharge the battery. Never returned it and I decided to play with it again and it did the same on a small 12volt battery I use for my trailer camera.Charger Specs.12 volt 2.5 Watt max.180 mAmeter reading in bright sun approx. 26 voltsMy Questions:Is there a short and simple option like a charge controller for such a small unit?If I cant use a Charge controller could I install a Blocking Diode on the positive lead and if so what size diode should I get?If the diode would work could I just put short lead and clamp on the diode and clamp it to battery then clamp lead from solar charge to the diode lead? Obviously I'm looking for an easy resolution to the problem because this unit will not see a lot of use.Thanks in advanceJiimb

author: Faranight
author_rank: Unknown
timestamp: August 13, 2023, 05:43:27 am
content: If you're charging the battery directly from a solar panel, make sure the panel's Voc doesn't exceed the battery's maximum allowable voltage. Yours appears to do so (26V vs 12V !!!).Solar panels are actually diodes, so yes, they will discharge the battery when connected directly. That's why there should be a schottky diode present in the loop to prevent reverse current. Some charge controllers may need such a schottky on the panel while others may not because they're using their switching mosfets to act as a barrier against reverse current (depending on what IC or topology they use). Your best bet would be to use a MPPT controller. I'm currently working on some of my own boards for small PV panels, but not for high voltages like 26V. Try looking on ebay or aliexpress, there should be some modules available for your application.

author: Xena E
author_rank: Frequent Contributor
timestamp: August 13, 2023, 05:51:22 am
content: If you're topping up a big beefy lead acid vehicle starter battery, (or a high capacity leisurebattery), on this little panel, then a series diode will be fine. Try a generic old fashioned 1N4004 or similar, with the cathode (end with the band) connected to the battery +, and the anode to the + output of the panel.

author: RoGeorge
author_rank: Super Contributor
timestamp: August 13, 2023, 10:43:59 am
content: The current is very small (for a typical 12V Pb based battery), so clamping a series diode should be OK.
Question - Page 1
Forum section: electronics / beginners

author: tony3d
author_rank: Frequent Contributor
timestamp: December 07, 2013, 06:42:35 pm
content: I'm thinking about buying Engineeringshock.com's 400f super capacitor battery with voltage booster,and I was wondering if it's ok to lay the pin side of the boards on my Antistatic mat while charged up? The mat should be totally non conducting right, or should I put a piece of thin cardboard on the mat first? The bank has 4 400f caps, wouldn't want to short them out in way. Here's a linkhttp://www.engineeringshock.com/super-capacitor-battery-bank--booster.html

author: Nerull
author_rank: Frequent Contributor
timestamp: December 07, 2013, 07:04:10 pm
content: ESD mats work because they are slightly conductive. Likely not enough to cause problems, but you might want to check it. Different types of mat material are more conductive than others.

author: tony3d
author_rank: Frequent Contributor
timestamp: December 07, 2013, 07:15:09 pm
content: I don't seem to be getting any conducting according to my meter. I think I'll go with the cardboard on op just for an added layer of protection. I plan on mount booth boards on a project box eventually.

author: tony3d
author_rank: Frequent Contributor
timestamp: December 07, 2013, 07:16:39 pm
content: Quote from: tony3d on December 07, 2013, 07:15:09 pm

author: nanofrog
author_rank: Super Contributor
timestamp: December 07, 2013, 07:31:34 pm
content: Assuming it's a 2 layer rubber mat, the top layer is static dissipative. Bottom layer is conductive, so you'd be OK so long as any signal isn't contacting the bottom layer (i.e. mat upside down).

author: Nerull
author_rank: Frequent Contributor
timestamp: December 07, 2013, 09:21:02 pm
content: The static dissipative layer in a dual layer mat is still conductive, just not as conductive as the bottom layer. Conductive mat material is generally in the range of 105ohms or less while dissipative is 105to 1011ohms. Higher resistances are insulative mats and will not disperse static charges, and they are not suitable for general electronics use.A mat that is too conductive will conduct static charges too quickly, damaging components that may be charged before contact with the mat, so you are unlikely to see a benchtop mat with low resistance - unless you flip a two layer mat upside down, anyway. The idea is to gently remove charge.
Questions about a MG811 module - Page 1
Forum section: electronics / beginners

author: quitenothing
author_rank: Newbie
timestamp: March 21, 2017, 06:01:44 pm
content: Hello,I want to do a CO2 monitor based on a MG811 sensor and an Arduino UNO card.I found a module but the schematic seems "weird" from my point of view.www.dfrobot.com/image/data/SEN0159/CO2%20Sensor%20V1%20SCH.pdfI see a LM358, but according to the MG811's datasheet (image.dfrobot.com/image/data/SEN0159/CO2b%20MG811%20datasheet.pdf) the impedance of the amplifier should be about 100G and the input current below 1pA. These values do not fit with the 20nA and 100M of the LM358.After some searches, I found a better circuit (http://sandboxelectronics.com/?p=147) which uses a LMC662 (closer to the sensor requirements).But I still have some questions:- why a resistor is added just before the non-inverting input? The LMC662 input bias current is very low (2fA), so why? And why 1k?- why a such amplifier circuit? It looks like an old NAB filter. Is it used to filter anything from heater power supply (I doubt it since it works at about 450kHz) ?Thx for any input.

author: quitenothing
author_rank: Newbie
timestamp: March 23, 2017, 08:10:34 am
content: Instead of a link to a PDF file, here's the circuit as attachment.