hybridfree/eevblog-posts huggingface dataset:
mCU recommendation with 4x >100kHz PWM - Page 1
Forum section: electronics / projects

author: drakejest
author_rank: Regular Contributor
timestamp: June 29, 2021, 01:42:34 pm
content: Hello i would like to ask for some micro controller recommendation with amust have:4x PWM pins >100kHz with 100 levels (about 7 bits resolution)1x SPI4x GPIO (12 GPIO in total)good to have:very compact - requires few components to functionrelatively cheaphas arduino IDE supportI actually tried looking for purpose built ICs but they are expensive so i am exploring a mCU approach of the problem if its cheaper to do it this way?

author: drakejest
author_rank: Regular Contributor
timestamp: June 29, 2021, 03:26:10 pm
content: The samd variant looks promising.

author: rstofer
author_rank: Super Contributor
timestamp: June 29, 2021, 03:51:28 pm
content: You didn't mention cost or package size...The chip in the Teensy 4.1 has 35 PWM pins and will clock at 150 MHz - presumably SystemClock / 4.https://www.pjrc.com/store/teensy41.htmlhttps://www.pjrc.com/teensy/IMXRT1060CEC_rev0_1.pdfAs uC's go, this one is pretty quick - 600 MHz - and it has a lot of memory.

author: ajb
author_rank: Super Contributor
timestamp: June 29, 2021, 04:57:22 pm
content: 100kHz * 8 bit resolution means a PWM clock of only 12.8MHz, that's practically nothing these days. If you need those four PWM channels to be synchronized then you might need to look for parts that have four compare channels per timer, which excludes some of the lower end 8-bit MCUs unless they support linking multiple timers.The Arduino support is probably the biggest limiting factor in your requirements. Cheap could be tricky given the current market situation with semiconductors. 12x total GPI means you're looking at ~20 pin or larger parts, so that's easy, SPI is almost a universal feature, and most MCUs require only a couple of passives.So I would suggest just looking for a list of Arduino-supported parts and start narrowing it down from there.
MCU timer modulo vs total counts - Page 1
Forum section: electronics / projects

author: Circlotron
author_rank: Super Contributor
timestamp: December 05, 2014, 03:54:12 am
content: For a HC908 timer it says "When the timer counter reaches the modulo value, the TOF flag is automatically set by hardware, and the timer counter resumes counting from $0000 at the next clock." To me that says if you set the modulo value to 20 then the counter repeats every 21 counts including zero count. Does that sound right?

author: Circlotron
author_rank: Super Contributor
timestamp: September 30, 2018, 09:27:31 am
content: Nearly 4 years, 659 reads and no replies!C'mon! Can't be that hard!P.S. I don't think there was a Microcontrollers & FPGAs section when I first posted this.

author: iMo
author_rank: Super Contributor
timestamp: September 30, 2018, 09:49:56 am
content: You wait 4 years to get such an answer?With modulo value "20" it will do 21 cycles.0-1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18-19-20-0-1-2..A mod-N counter stores an integer value, and increments that value on each clock tick, and wraps around to 0 if the previous stored value was N-1.

author: Circlotron
author_rank: Super Contributor
timestamp: September 30, 2018, 10:28:40 am
content: Quote from: imo on September 30, 2018, 09:49:56 amThese people think it will do it in 20 cycles, not 21.https://www.edaboard.com/showthread.php?77505-What-is-a-Mod-N-CounterSo do these:http://courses.cs.vt.edu/cs2505/fall2012/Notes/T36_Counters.pdfhttp://courses.cs.vt.edu/cs2505/fall2012/Notes/T36_Counters.pdf

author: Circlotron
author_rank: Super Contributor
timestamp: September 30, 2018, 10:38:53 am
content: Quote from: Circlotron on December 05, 2014, 03:54:12 amOr does that mean if the modulo is set to 20, when 20 is reached the TOF flag is set and the timer count is immediately reset to zero instead of staying at 20 because THE TIMER COUNT RESUMES COUNTING=FROM=$0000 AT THE =NEXT= CLOCK?"FROM" zero is the important word.

author: Benta
author_rank: Super Contributor
timestamp: September 30, 2018, 01:19:14 pm
content: It's what imo said.

author: Siwastaja
author_rank: Super Contributor
timestamp: October 03, 2018, 08:36:48 am
content: As a general note, things like these need to be tested. MCU documentation errors are very typical so that the hardware doesn't match the documentation. People on the forums are sometimes right from their own experience, but sometimes just read the same documentation you already are reading to write their reply. Even those experienced may remember it wrong. So when encountered with a question like this, spend the minute or two to test it, and remember to document the behavior as a code comment.Actual testing may also reveal totally unexpected behavior that's neither of the expected outcomes. For example, on AVR, a certain PWM timer mode (forgot which) gives very short pulses (skipping the prescaler!) when set to output "0", which is highly unexpected IMHO.
mcu video movie player - Page 1
Forum section: electronics / projects

author: 5282
author_rank: Regular Contributor
timestamp: October 06, 2016, 08:55:07 am
content: here is my first stm32 video player i running stm32 mcu on 42mhz only . reading data from sd using sdio

author: amyk
author_rank: Super Contributor
timestamp: October 06, 2016, 11:17:54 am
content: "only" 42MHz? How about 16 MHz on an ATmega32...

author: 5282
author_rank: Regular Contributor
timestamp: October 07, 2016, 11:10:31 am
content: i can play 1280*720 compressed MPEG-4 video @30fps with 16 MHz on two ATmega32 chips

author: Wilksey
author_rank: Super Contributor
timestamp: October 07, 2016, 04:50:37 pm
content: Are they open source?

author: rob77
author_rank: Super Contributor
timestamp: October 07, 2016, 04:58:05 pm
content: Quote from: 5282 on October 07, 2016, 11:10:31 amhow on earth would you do that ? i'm open to learn something

author: m98
author_rank: Frequent Contributor
timestamp: October 07, 2016, 08:55:44 pm
content: Playing videothatfluid with an 8-bit Atmega is somewhere behind the voodoo corner just shortly in front of RF black magic...EDIT: Wait, there's code and schematics:http://blog.vinu.co.in/2012/06/avr-video-player-on-nokia-color-lcd.html

author: nctnico
author_rank: Super Contributor
timestamp: October 07, 2016, 08:59:29 pm
content: Quote from: m98 on October 07, 2016, 08:55:44 pmNotice the motion smearing? Reading raw data and dumping that onto an SPI display isn't that hard.

author: rob77
author_rank: Super Contributor
timestamp: October 07, 2016, 09:28:35 pm
content: Quote from: nctnico on October 07, 2016, 08:59:29 pmthat's all ok, converting a video to 132x132 pixels at 2 bytes per pixel and shoveling that to a display with a micro is not magic.... i'm interrested in the 720p Mpeg4 using 2 atmegas mentioned above.Quote from: 5282 on October 07, 2016, 11:10:31 amplease share it with us, i would really like to learn something

author: 5282
author_rank: Regular Contributor
timestamp: October 08, 2016, 01:56:50 pm
content: ok i will share
STM32F407 won't boot - Page 1
Forum section: electronics / projects

author: Geocheats2
author_rank: Newbie
timestamp: July 09, 2021, 08:26:26 pm
content: HelloI designed a board based on stm32f407 and while i am pretty happy it finally got delivered i don't seem to be able to boot itI am using the cheap ST-LINK v2 clones from the usual suspects and for some reason i don't seem to be able to get any output on the OSCI would love your helpPlease tell me what would you like me to upload i will start with the MCU SchematicPlease not that i haven't pulled up RST on +3V3 on the schematic but i do have on the board also i have tried connecting BOOT0 to GND and to +3V3 (not at the same time ofc)Looking forward to your repliesGeorge

author: julian1
author_rank: Frequent Contributor
timestamp: July 09, 2021, 11:36:49 pm
content: From memory..Does it answer back on the st-link? The external oscillator won't run unless the flashed code actually enables hse, so it's not a very useful test.boot0 should be pulled low. boot1 doesn't matter. reset should be pulled low, then high.Vref+ *and* I think vbat need attention, and are check by the st voltage supervisor, before it turns on the 1.2V core.check the voltages on vcap1 and vcan2. If they show 1.2V then the core mcu is powered on, and the issue is configuration/higher - eg. swdio wiring or boot0/reset.
Mean-Well LCM power supplies and DALI troubles - Page 1
Forum section: electronics / projects

author: BiggusDikkus
author_rank: Newbie
timestamp: July 29, 2021, 03:37:49 pm
content: Hi,anyone here have any experience with Mean-Well DALI-enabled LCM (LCM-25DA, LCM-40DA and so on) line of power supplies?I've installed several (all bought from the local designated Mean-Well dealer and their S/N checks out too) and for some reason they won't turn off. I can control them no problem but when I turn them off they still "glow" a little. I use them with Cree chips like the CXB1512 etc.Anyone getting any ideas?
Meaning and consequences of high voltage edge effect? - Page 1
Forum section: electronics / projects

author: kkkwj
author_rank: Newbie
timestamp: October 18, 2018, 01:34:09 am
content: I have recently heard about the Biefeld-Brown effect, the electrostatic effect, and the electrokinetic effect. (I think he played with all of them.) Anyhow, all of them involve high voltages, charges, and capacitors of various shapes. Apparently, it is important to avoid "edge effects" (whatever they mean) for some reasons (unwanted consequences). I can see why sharp edges at high voltages are more likely to generate corona effects and corresponding power losses from unwanted currents. But, I haven't been able to find out much on why "edge effects" are bad if sufficient anti-corona protection is in place so that obvious arcing and sparking and current does not flow. I'm working with 10-50Kv at less than a milliamp (eg. 100 or 200 microamps), on small devices about 6 inches in size, where all electrodes are encased in epoxy and have no contact with the air.Could anyone here shed some more light on this topic, or point me to some good web links on the topic? Thank you.

author: coppercone2
author_rank: Super Contributor
timestamp: October 18, 2018, 02:31:43 am
content: I think that the discharges mean that a stronger field is present, so you can be putting stress on the dielectric (better to design not to have stress) and it also might lead to dust accumulation thats non uniform and effected by a field, so you can have like, little dendrites/etc of dust form in these regions even if protected, which can do things like accumulate moisture and short out faster then uniform dust distribution.If a dielectric is under stress it might effect its properties (i.e. plasticizers or other plastics). The breakdown voltage might be lower in these areas too, so they are weaker when transients occur. There might be increased chances of crack formation in the material as well.also arcing is going to produce ozone and UV which like to destroy things. and slowly vaporize metal to possibly make conductive paths or change in surrounding materials which metrologically effect your circuit.
Meaning of 'NDK' in reference to PCB holes - Page 1
Forum section: electronics / projects

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: May 03, 2017, 11:35:40 am
content: A friend has a datasheet for a Phoenix connector that includes the attached, can anyone help in decoding what 'NDK' means?

author: Unknown
author_rank: Unknown
timestamp: May 03, 2017, 12:17:07 pm
content: Phoenix are German, so probably Nicht-Durchkontaktierten (sp?) i.e. non-plated through (holes).

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: May 03, 2017, 01:40:48 pm
content: Thanks, that's what we thought it meant but it's good to get confirmation

author: Twoflower
author_rank: Frequent Contributor
timestamp: May 03, 2017, 05:22:46 pm
content: Sorry, but I can't come up with a better answer. But since everything else is written in English: Why did they kept this in German? And actually there is no German version of the drawing. So here's a small chance that this means something else. In doubt, I would suggest to contact them and get the final confirmation before you run into trouble with your design.@Tac Eht Xilef: Perfect translation! Nicht Durchkontaktiert is the correct German therm for one non-plated through hole, ending with -en means plural.

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: May 04, 2017, 11:28:14 am
content: My friend did contact Phoenix who said...QuoteHe's pretty much confirmed that 'NDK' means what we think it means because the connector came with a sample PCB and the holes marked 'NDK' in the data sheet are not through-plated on that sample.The idea that a German company uses a German abbreviation in the English documentation seems pretty dumb to me.

author: dave_k
author_rank: Frequent Contributor
timestamp: May 04, 2017, 11:32:44 am
content: Why or when would you use a plated through hole for a plastic support post? Seems pretty self-explanatory regardless of language

author: timb
author_rank: Super Contributor
timestamp: May 04, 2017, 12:01:33 pm
content: Quote from: dave_k on May 04, 2017, 11:32:44 amTo solder it to the board, duh!

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 04, 2017, 12:17:18 pm
content: Quote from: dave_k on May 04, 2017, 11:32:44 amHaving both plated-thru and NON plated-thru requires extra steps in the PCB manufacturing process which increases the cost of manufacture. Although it would appear to be essentially "standard" for all but the lowest-end PCB manufacture.
MeanWell DDR-240D-24 Railway power supply - Page 1
Forum section: electronics / projects

author: Simon
author_rank: Unknown
timestamp: November 27, 2019, 12:31:47 pm
content: I have a project where I need to step down from 72V to 24V and I have come across the mealwell DDR series of converters that are rail approved.Should they be trusted? I need to send them to a hot country.

author: dr.diesel
author_rank: Super Contributor
timestamp: November 27, 2019, 12:44:55 pm
content: I've not used that specific product, but I've used many many Meanwell products in the past, all good. I wouldn't hesitate to use anything they make.Lots of fakes out there though.

author: Simon
author_rank: Unknown
timestamp: November 27, 2019, 12:46:25 pm
content: Well we would purchase through someone like RS

author: nali
author_rank: Frequent Contributor
timestamp: November 27, 2019, 12:57:47 pm
content: Same as Dr D - I've used tons of Meanwell although not Rail products. Only in this country, but in bus shelter displays which can get pretty hot through their own power dissipation plus solar gain.I used to buy fromhttps://www.meanwelldirect.co.ukbased in Reading.

author: Simon
author_rank: Unknown
timestamp: November 27, 2019, 01:07:57 pm
content: well they don't have it but I can alway enquire.

author: Simon
author_rank: Unknown
timestamp: November 27, 2019, 02:11:48 pm
content: Actually I can get a 1kW melcher unit for the same cost per W as I need nearly 1kW anyway and you loose 10% the power when you parallel the meanwell supplies.
Meanwell NID100 DCDC module inductor type - Page 1
Forum section: electronics / projects

author: Romain
author_rank: Regular Contributor
timestamp: July 07, 2023, 08:27:32 am
content: Hi,I'm using the Meanwell NID100-12 module to step down 48V to 12V.In the datasheet they have a recommended circuit for EMC compliance with 3 added capacitors and one inductor.Capacitors are standard electrolytic.What type should the inductor be? Is this a choke? I'm not sure what to search for on Mouser.Datasheet link:https://www.meanwellusa.com/webapp/product/search.aspx?prod=NID100#1Thanks

author: CosteC
author_rank: Regular Contributor
timestamp: July 07, 2023, 08:43:22 am
content: L1 is common mode choke, judging from symbol.You need to find one with enough current capacity for your application and nominal 15 uH inductance, which is rather small value.MeanWell suggest use of NiZn core material for some reason. This shall be easy to meet too.

author: Romain
author_rank: Regular Contributor
timestamp: July 07, 2023, 12:20:18 pm
content: Thanks CosteC, that was helpful!I'm planning to use this:https://www.lcsc.com/product-detail/span-style-background-color-ff0-Common-span-span-style-background-color-ff0-Mode-span-Filters_Sunltech-Tech-SMW1006S220YTT_C878364.htmlIt's a 22uH common mode choke, couldn't find any 15uH.The core material isn't specified. How critical is this?

author: CosteC
author_rank: Regular Contributor
timestamp: July 07, 2023, 05:55:58 pm
content: If you do not need to cut costs wurth elektronik has far better datasheets. What you found shall work, yet it is EMC, only measurements will tell
Meanwell PSU fan output  - Page 1
Forum section: electronics / projects

author: joerice01
author_rank: Newbie
timestamp: April 11, 2021, 01:10:06 am
content: I'm currently building a project with the Meanwell EPS-120-27 power supply.There is a dedicated fan output rated at 12v 0.5A, however when I plug in my Sunon 12v 40mm fan it does not spin.I can feel it pulsing though.I measured the voltage of the fan connector as 10.8V and is within the tolerance of the stated value (-15% to +10%).When I power the fan by another source with 10.8V it turns on fine and only draws 0.050 amps.PSU Datasheet:https://www.meanwell-web.com/content/files/pdfs/productPdfs/MW/EPS-120/EPS-120-spec.pdfFan datasheet:https://docs.rs-online.com/1531/0900766b815d9a49.pdfIs there something I am missing here?Thanks in advance.

author: AmnevaR
author_rank: Contributor
timestamp: April 11, 2021, 09:04:37 am
content: It's weird. Have you tried to put some load on power supply when the fan is connected to it?

author: BrokenYugo
author_rank: Super Contributor
timestamp: April 11, 2021, 02:00:54 pm
content: I'm assuming you're testing this fan supply with no load on the main output?Note how in the block diagram the fan supply has no regulation. With little to no load on the main rail only a very small amount of current will be available on the fan supply, since only a very low amount of power is being driven into the switching transformer.The 10.8 volts you measured would probably disappear if you put a test load on the fan output, something like a 220 ohm 1 watt resistor. Put a few watts load on the main output and it will come right up.

author: joerice01
author_rank: Newbie
timestamp: April 11, 2021, 10:28:35 pm
content: It only has a dps3003 buck at this point. I'll load that up and see if it comes on. I did try it with a small fan and that came on with no load. Must be just big enough to need it.Thanks

author: NiHaoMike
author_rank: Super Contributor
timestamp: April 12, 2021, 03:22:39 am
content: Maybe the fan output supplies more current as the supply heats up?

author: TimNJ
author_rank: Super Contributor
timestamp: April 13, 2021, 12:57:21 am
content: Motors always draw more current to start them up. Usually stall current and start-up current are roughly the same. You'd think with enough bulk capacitance on the fan supply that it should be able to supply the transient start-up current...but maybe not.I looked at some images of EPS-120. I don't see any electrolytic caps near the fan output connector. Maybe it's just 1 or 2 1206 caps on the bottom, in which case, would probably not have enough storage to supply the start-up current.Just a guess.
Meanwell RPS or EPP Series SMPS Voltage Hack? - Page 1
Forum section: electronics / projects

author: AJ3G
author_rank: Regular Contributor
timestamp: December 07, 2022, 10:13:46 pm
content: All:Before I start tearing these apart, I thought someone might have done this modification or hack to the RPS or EPP Series Meanwell supplies. I am trying to determine which resistor provides the shunt regulator feedback. I am trying to increase a RPS-500-18 or EPP-500-18 output voltage to 22 - 23VDC. I have looked at the output section of the supply and the capacitors look more than able to handle this small increase in voltage.Normally I would have no problem just going in and tracing this out, but this supply is compact, and looks to be spring loaded (figuratively speaking). I would prefer not to take of the shields and heat sinks to probe around if I can avoid it.Thanks!Rich

author: TimNJ
author_rank: Super Contributor
timestamp: December 07, 2022, 11:16:01 pm
content: They are LLC resonant designs. You are asking to operate with 'step-up gain', which means it will probably be operating below the resonant frequency. May or may not be a problem, but it's a little different than modifying the output voltage on duty-cycle/PWM controlled topologies. Plus, you don't know how close they are running the synchronous MOSFETs to their max ratings, so on and so forth. I guess you accept these risks.Anyway, I think there a potentiometer fitted on all of these by default, right?Check the RPS-500/EPS-500 spec. For 18V, the adjustment range is just 17.1~18.9V (and maybe for reasons like the above). For 24V, the adjustment range is 22.8~25.2V. Sounds like you should start with the 24V as a base instead.

author: ajb
author_rank: Super Contributor
timestamp: December 08, 2022, 02:23:43 am
content: As TimNJ notes most of these have adjustment pots and will often reach outside of the specified range IME. If you need more adjustment range, there are some models that allow the output voltage to be externally controlled over a larger range. IIRC the RSP-1000 and SPV-300 both have that feature.

author: AJ3G
author_rank: Regular Contributor
timestamp: December 08, 2022, 02:31:26 am
content: All:Thanks for the response. I suppose I could start at 24V. I had hoped I could simply modify the the 18V variant and then return to 18V when I need it.Rich

author: ssashton
author_rank: Frequent Contributor
timestamp: April 07, 2023, 09:38:56 pm
content: Digging up an old trad - I am looking at using these supplies. What is the difference between RPS and EPP?Thanks!

author: tooki
author_rank: Super Contributor
timestamp: April 07, 2023, 09:46:33 pm
content: Quote from: ssashton on April 07, 2023, 09:38:56 pmRPS is medical safety rated. EPP is standard industrial.
Meanwell sine inverter--information needed - Page 1
Forum section: electronics / projects

author: iXod
author_rank: Frequent Contributor
timestamp: March 19, 2019, 04:09:10 am
content: It's a TS-1000-124A, a "true sine", 120VAC 1000W output, 24VDC input.I'm looking for a schematic of this or other Meanwell sine inverter:https://www.meanwell.com/webapp/product/search.aspx?prod=TS-1000Anyone familiar with how similar these Meanwell sine inverter input voltage stages are (rectification & input to the "chopper")? Would a 24VDC unit work on 12VDC? Or might these boards be made for several DC voltages and populate (or not) certain components?I don't have the unit but am contemplating that it may somehow be useful on 12v, maybe derated.Thanks.

author: iXod
author_rank: Frequent Contributor
timestamp: March 19, 2019, 04:28:45 am
content: Thanks for your reply.If we talk about only taking, max, half power from the output (probably 400W), doesn't that change the input demands?

author: iXod
author_rank: Frequent Contributor
timestamp: March 19, 2019, 04:39:26 am
content: FYI, this unit is 120v output.2:1 means that with half DC input voltage, the AC output voltage will also be half (60-ish VAC)?Just trying to follow along...Thanks.

author: iXod
author_rank: Frequent Contributor
timestamp: March 21, 2019, 03:17:39 am
content: The manufacturer confirms that the transformer is different for the 12 and 24v input inverters.
Meassuring transformer turns ratio without the core? - Page 1
Forum section: electronics / projects

author: Deactivated-1
author_rank: Frequent Contributor
timestamp: October 08, 2022, 06:27:16 pm
content: So I am winding an L-core transformer but I forgot to meassure the voltage ratio before taking it apart, and I dont want to put it back together so as to not break the insulating layer on the core plates too much.could I just power the primary with a lower voltage, and then wind some wire around it? just having an air core transformer?

author: Benta
author_rank: Super Contributor
timestamp: October 08, 2022, 07:53:38 pm
content: With the core out, lower voltage and higher frequency will also work for getting the pri/sec ratio.

author: gbaddeley
author_rank: Regular Contributor
timestamp: October 08, 2022, 10:32:30 pm
content: Put a loose stack of lams in the primary core and power it using a low voltage eg 12v 60hz. Wrap 10-20 turns of hookup wire as a dummy secondary with a 100 R load. This will give a good idea of the T/V ratio.

author: The Electrician
author_rank: Frequent Contributor
timestamp: October 09, 2022, 02:32:39 am
content: Quote from: ELS122 on October 08, 2022, 06:27:16 pmYou say that you are "winding". Will you be using a new bobbin? Do you mean "re-winding" on the old bobbin? Just what do you plan to do? Are you going to keep the primary and re-wind a new secondary? Or are you going to replace both windings?Have you already removed the existing seconday winding? If you haven't, then you can count the secondary turns and knowing the rated secondary voltage and primary voltage, you can calculate the turns ratio.

author: The Electrician
author_rank: Frequent Contributor
timestamp: October 09, 2022, 02:55:31 am
content: Is that all you have to say to my questions? Can't you figure out how to substitute "bobbins" for "bobbin" in my post? Have you destroyed the existing secondary(s)?

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 09, 2022, 03:28:52 am
content: You can put a Hall sensor into the hole and use that to determine the approximate turn count of each winding by measuring how much current it takes to change the output of the sensor.

author: The Electrician
author_rank: Frequent Contributor
timestamp: October 09, 2022, 05:02:30 am
content: Don't worry about the insulating layer on the laminations. At the very least they will have a coating of steam oxide. The better laminations have a coating of Carlite, which is magnesium silicate. You should see how laminations are shipped to transformer manufacturers. They come by motor freight, and they're stacked in a long cardboard box with nothing between the individual lams. They are subject to a lot of shaking and vibration, and they are not damaged by all that rubbing against one another. If the secondary is still there you could just put about 90% of them back in and that way you wouldn't have to jam the last few in. That would be enough core to let you measure turns ratio in the usual way. The insulating layer on the lams is much more rugged than you might think, and it won't be hurt by re-inserting then several times.
Measure CAN bus resistance on a "live" circuit  - Page 1
Forum section: electronics / projects

author: tru3533
author_rank: Regular Contributor
timestamp: September 10, 2023, 01:21:42 pm
content: How do you measure CAN bus resistance on a "live" circuit?I see that Peak have the mini diaghttps://www.peak-system.com/PCAN-MiniDiag-FD.490.0.htmlAnd it can measure CAN termination resistance.Seeing it demonstrated on a live network, you can hear a relay switching in and out when measuring the resistance.Any idea how this can be done?
Measure corrosion between copper wire and steel pipe - Page 1
Forum section: electronics / projects

author: jegjessing
author_rank: Newbie
timestamp: March 29, 2021, 11:13:23 am
content: HiI'm desperately trying to figure out how to measure the corrosion done on a steel pipe, that has a copper wire in some foam insulation between the copper wire and the steel pipe.I've read that one should use a zero resistance amperemeter but I have not found a circuit that does this without a third connection where one also measures the voltage.Does anyone know of a circuit that measures this?I guess can't rely on a voltmeter, since this will put a resistive load on the material.In short. I'm clueless :-)Thanks in advance

author: LaserSteve
author_rank: Super Contributor
timestamp: March 29, 2021, 01:48:54 pm
content: You need a Potentiostat. Then you need a Corrosion Scientist or Corrosion Engineer to help you interpret the results. Yes, the reference electrode will also be needed. I'll ask at work, where we train Corrosion Engineers, but due to the presence of the foam, your going to need a specialist.Steve

author: RCO_JOE
author_rank: Newbie
timestamp: March 30, 2021, 02:56:51 pm
content: I've got a 10 year result of steel strapping on a copper pipe with and without foam between the two in certain areas in my HVAC lineset run if you need some photos. The copper pipe (soft solid copper) has not been penetrated even with 50c 98% humidity (typical leaking dryer vent) environment. The last time I checked, it's the copper that is corroding.
Measure current of high voltage tiangle wave? - Page 1
Forum section: electronics / projects

author: kenw232
author_rank: Contributor
timestamp: May 15, 2015, 04:16:50 pm
content: I have a .66uF capacitor bank discharging into a pulse transformer. Vpeak is 1000V. The math equation I = C x (dV ÷ dt) should tell me the current being discharged from the cap bank which is I = .66µF x (1000Vpeak ÷ 19.5ms) = 33.8mA (my frequency is 50Hz and period is 19.5ms for a triangle wave). But when I put my DC ammeter in series it reads about 62mA.Why the difference? Shouldn't my ammeter read 33mA? Does anyone know what I'm missing here?

author: Zero999
author_rank: Super Contributor
timestamp: May 15, 2015, 05:19:17 pm
content: Have you taken into account the meter will measure the average current?

author: kenw232
author_rank: Contributor
timestamp: May 15, 2015, 10:40:53 pm
content: Yes, is and average not the same thing? I mean when someone says they want a current reading is that not the absolute number of coulombs for 1 second? which is best expressed as amps whether an average or not, it should be roughly the same thing assuming the waveform is consistent.I'm simply trying to find a way to experimentally (so with an ammeter) confirm the math. My DC ammater doesn't cut it for some reason like I said. Should I be using a different kind of ammeter do you know?

author: Vgkid
author_rank: Super Contributor
timestamp: May 16, 2015, 12:46:06 am
content: It might be easier to measure with a o-scopenote t1/T is the duty cycle.http://masteringelectronicsdesign.com/how-to-derive-the-rms-value-of-a-triangle-waveform/

author: kenw232
author_rank: Contributor
timestamp: May 16, 2015, 01:34:59 am
content: Thanks, I seen that. Using an oscilloscope to measure current with a small resistor is apparently difficult at these voltages (1000V).

author: Marco
author_rank: Super Contributor
timestamp: May 16, 2015, 02:11:03 am
content: You put the resistor between ground and the transformer, say a 1 Ohm resistor .... you can use a diode to clamp the voltage across it if you fear a couple 100 Amperes are somehow going to make it past the transformer.

author: kenw232
author_rank: Contributor
timestamp: May 16, 2015, 04:26:05 am
content: Quote from: Marco on May 16, 2015, 02:11:03 amThen I measure the voltage across the 1 Ohm resistor with my scope. But won't the voltage drop across the resistor be too insignificant if its 1000V waveform going into the transformer?

author: Marco
author_rank: Super Contributor
timestamp: May 16, 2015, 04:35:08 am
content: Depends on your scope, mine has a 2mv per div range (with the 1x attenuation setting on the probe/scope). You could use an opamp to amplify it or use a bigger resistor (but then you couldn't clamp with a diode any more, would need to use a zener/TVS ... and the burden voltage starts becoming significant).

author: Vgkid
author_rank: Super Contributor
timestamp: May 16, 2015, 05:33:32 am
content: I would use an opamp as an amplifier. As your frequency is not very high, most opamps would do.
measure current with Hall effect Current Sensor - Page 1
Forum section: electronics / projects

author: anishkgt
author_rank: Frequent Contributor
timestamp: October 13, 2018, 03:33:23 pm
content: Hi All,i am trying to measure an AC current from Microwave transformer (which is rewound to be used a spot welder) at the secondary. With a bulb in series at the primary i get current reading of 19A.How do i measure it with a Hall effect current sensor (http://www.tamuracorp.com/clientuploads/pdfs/engineeringdocs/L06PXXXS05.pdf).I get 1.46A in the serial monitor with the below code.Code:const int TRIAC = A1;const int VIN = A7;float voltage;byte cal = 0;unsigned int maxReading = 0;unsigned int minReading = 1023;unsigned int reading = 0;void setup(){Serial.begin(115200);pinMode(TRIAC, OUTPUT);//pinMode(Isense, INPUT_PULLUP);}void loop(){if (cal == 0){ cal = 1;digitalWrite(TRIAC, HIGH);reading = analogRead(A2);Serial.println("Calibrating.....");while (millis() < 1000){voltage = analogRead (VIN);}digitalWrite(TRIAC, LOW);float current = (voltage / 1024.0) * 5.0;Serial.print("Current: ");Serial.print(current,2);Serial.println("A");}}

author: duak
author_rank: Super Contributor
timestamp: October 13, 2018, 05:20:01 pm
content: A description or sketch of the circuit would be useful.The current sensor will produce an AC waveform centered around half its power supply voltage. Do you have an AC-DC converter to convert the AC output of the current sensor to DC for the A/D converter?The code looks like it will print the last sample at the end of a one second period. I think I see a number of other problems in the code, however, I don't know enough about the various definitions to say for sure.Cheers,

author: anishkgt
author_rank: Frequent Contributor
timestamp: October 13, 2018, 07:43:55 pm
content: Code:void loop(){if (cal == 0){int counter = 0;cal = 1;digitalWrite(TRIAC, HIGH);int i;for (i = 0; i <= 10; i++){int Vin = analogRead (VIN);voltage = Vin;voltage += Vin;//Serial.print(i);//Serial.print(" ");Serial.println(voltage);}digitalWrite(TRIAC, LOW);}}Here is the revised code. I was hoping with this sensor i could straight away get voltage reading corresponding the ac current. What more would i need to get a current reading ?
Measure insulation resistance on high voltage water cooled resisitor? - Page 1
Forum section: electronics / projects

author: max_torque
author_rank: Super Contributor
timestamp: December 09, 2016, 06:21:13 pm
content: I'm think of using some water cooled resistors as a load, and they will have a max of around 500Vdc driving current through them.Although the claimed resistance between the water channel and the actual resistance (wire wound) element is huge (>10E8 ohms) i'm wondering if a failure case exists from an overheated resistor getting shorted to the water channel, and hence the cooling water loop itself?Of course, we can use silicone pipes to interlink the resistors to the water distribution manifold, but the actual water itself will be conductive (it's around 50:50 water/glycol).Without buying anoff the shelf Isometer, anyone got any clever ideas to monitor leakage currents or measure the impedance between coolant and HV ?(guess a CT around the DC link in-out wires a-la RDC kinda device could work??)

author: Jeroen3
author_rank: Super Contributor
timestamp: December 09, 2016, 06:38:50 pm
content: If you are afraid of such failure mode, you could consider an RCD. However, care must be taken that you buy one suitable for DC.You can diy an megger using an isolated voltage source and (u)current meter.Eg: backlight inverter.But, that is far from safe compared to a real megger. Which should be in your toolbox if you work with >100V regularly.They don't have to be expensive.http://nl.rs-online.com/web/p/insulation-testers/8937922/

author: max_torque
author_rank: Super Contributor
timestamp: December 09, 2016, 06:45:11 pm
content: Yes, we have all the usual test equipment like Meggers etc.I'm looking for a permanent installed solution that will open a safety contactor if excessive ground leakage is determined. The Resistor bank is controlled by a micro controller anyway, so adding leakage detection should be easy.....It certainly needs to work with DC, so no simple "common mode" style passive current transformers will work, but perhaps using a low range LEM hall effect CT might ?Ie DC bus + and - wires both through CT, amplify output, and trip safety contactor if it goes over some set point etc.Can probably arrange some sort of auto-zero type affair where the output of the CT is read whilst the contactor is open at power on, and that value becomes the "zero" leakage value?

author: Kevman
author_rank: Regular Contributor
timestamp: December 09, 2016, 07:20:33 pm
content: So basically you need a DC GFCI?You might be able to find such a thing by looking at the solar industry. For instance, here's one that's rated to 300V. Might be able to find a higher voltage one somewhere. I doubt it will be cheap.http://www.midnitesolar.com/productPhoto.php?product_ID=252&productCatName=Breakers&productCat_ID=16&sortOrder=4&act=p

author: Wolfram
author_rank: Frequent Contributor
timestamp: December 10, 2016, 12:46:37 pm
content: Quote from: max_torque on December 09, 2016, 06:45:11 pmThe CTSR 0.3-P seems like a good candidate. Vacuumschmelze have some similar ones on the market as well, but they are more expensive.
measure negative voltage  - Page 1
Forum section: electronics / projects

author: electros6
author_rank: Regular Contributor
timestamp: January 06, 2014, 02:02:27 pm
content: Hi guys ,In my power supply project I want to measure negative voltage using uc . somebody please tell me how to convert negative voltage to positive.I tried to convert negative voltage using LM358 as negative amplifier with a gain of -1 but when I tried to connect the output voltage of my prototype via voltage divider network , but when I connect the voltage at the divider output to opamp the voltage drops to - 0.66V and that - 0.66v convert 0.66 voltage via the inverting amplifier.please guide me

author: tszaboo
author_rank: Super Contributor
timestamp: January 06, 2014, 02:07:15 pm
content: You divide it to a known positive voltage, and you put a diode protection on it to the microcontroller's power rails. no opamp is needed.

author: Rerouter
author_rank: Super Contributor
timestamp: January 06, 2014, 02:21:37 pm
content: You offset the output of your op amp to half supply (in this case i guess your running 5V, so that would be 2.5V) by summing it with an op amp,note in the image you would need to either buffer what your taking in, or increase the 2 resistance values to a point where the source impedance is minimal in comparison,

author: electros6
author_rank: Regular Contributor
timestamp: January 06, 2014, 02:49:31 pm
content: I am running the opamp from + and - 12V supply and I want to measure dc voltage

author: Rerouter
author_rank: Super Contributor
timestamp: January 06, 2014, 02:57:51 pm
content: still to the same effect, say your micro runs on 5V, then you would sum with 5V, you can then measure +- 5V (signal gets divided by 2), you just need to scale in software so that 2.5V corresponds to your 0V,
Measure power mVA (Watt) with a 121gw - Page 1
Forum section: electronics / projects

author: chlor
author_rank: Newbie
timestamp: November 10, 2018, 03:09:20 pm
content: As my old multi meter is more than 20 years old and can not measure power, I gave myself a 121gw for birthday present.One thing I will use it for is educating my kids but the instructions for measure power is not that easy to understand. Please find a suggestion attached.

author: Benta
author_rank: Super Contributor
timestamp: November 10, 2018, 04:23:26 pm
content: The idea is to measure voltage and current simultaneously, which your setup also shows.Note that you only measure apparent power (VA), not real power (W), so this only works with resistive loads.

author: coppercone2
author_rank: Super Contributor
timestamp: November 10, 2018, 05:22:39 pm
content: great scott !

author: coppice
author_rank: Super Contributor
timestamp: November 10, 2018, 05:34:22 pm
content: I just looked at the manual for the 121GW, and it is not very clear about connecting the meter for power measurements. I would have expected the COM terminal to be connected to the load, and the mA/uA terminal to be connected to the source. However, the connection arrangement you show is what the manual implies, without showing in a nice clear picture. Does the meter measure voltage between the V/ohms terminal and the mA/uA terminal when in VA measurement mode, or is the burden voltage of the current measurement not compensated for?

author: picburner
author_rank: Frequent Contributor
timestamp: November 10, 2018, 05:59:16 pm
content: The connection in the figure corresponds to the power in mW(mVA)Connecting to the 500mA (low burden) terminal the power will be in W(VA).The connection of the DUT and the power supply in the figure are correct.

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 10, 2018, 07:39:10 pm
content: Quote from: Benta on November 10, 2018, 04:23:26 pmThe Mooshimeter can measure real power since (IIRC) it has dual ADCs. Does the 121GW only have a single ADC multiplexed between current and voltage and it turns out the mux is too slow to handle real power measurement?

author: Benta
author_rank: Super Contributor
timestamp: November 10, 2018, 07:46:32 pm
content: Quote from: NiHaoMike on November 10, 2018, 07:39:10 pmNormally DMMs use a dual-slope converter (=slow). AC is measured using a front-end, either just a rectifier or a TRMS converter. No matter which, in the end it's a DC measurement. Multiplexing between the two DC values is simple.
Measure small current with high and changing common mode - Page 1
Forum section: electronics / projects

author: Wipffinder
author_rank: Newbie
timestamp: November 27, 2019, 01:26:29 pm
content: Hi folks,For some time I am thinking how to design a measurement circuit and after learning that there a still great Forums in existence I wanted to ask your wisdom about it.Measurement to do:Measure small current signal (10µA – 100µA, precision of 5% is sufficient) at frequencies in the range of 10kHz – 400kHz with a common mode voltage that changes (20V/µs – 40V amplitude).The common mode voltage is a trapezoid and measurement are taken when the common mode voltage is constant (but immediately after a flank).How to output measurement:The current should be converted to a voltage free of common mode voltage for reading with an ADC.Restriction:Not more than 100Ohm in series if a shunt is used (1mV – 10mV voltage drop)What I fought about or tried:1. Using difference amplifier (INA157, LT6375 etc.) and a shunt. The problem is that this amplifiers are quite noisy (LT6375) or their common mode rejection at higher frequencies is not good enough (INA157)2. Making a differential amplifier with a matched resistor network and a low noise high CMRR Opamp. -> CMRR is a problem3. Hall sensors are slow or lack resolution, instrumentation amplifier may be restricted in common mode rangeIt is for a science project I want to do.What general measurement method is best suited? Do you have any suggestions? For now I only tried the shunt – difference amplifier combination and it somehow works but noise is too big for my 5% requirement.Have a nice daynking how to design a measurment

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 27, 2019, 01:49:41 pm
content: Use an active I/V converter (on the order of 1-10V full scale voltage) with its ground connected to the source side, you'll need an isolated power supply to run it, such as a DC/DC converter or even batteries. It would also be a good idea to shield the entire I/V converter assembly with the shield connected to the source side. Then use a differential amplifier to isolate the output.

author: Marco
author_rank: Super Contributor
timestamp: November 28, 2019, 02:51:56 am
content: Quote from: Wipffinder on November 27, 2019, 01:26:29 pmHow fast is the edge? If it's relatively slow you could just AC couple both sides of a shunt down.
measure the inductance of stator of a BLDC motor - Page 1
Forum section: electronics / projects

author: amirkargar110
author_rank: Contributor
timestamp: September 29, 2018, 07:42:46 am
content: Hi,I want to know how to measure the inductance of stator of a BLDC motor?

author: Benta
author_rank: Super Contributor
timestamp: September 29, 2018, 09:51:58 am
content: Just measure over two phases.
Measure the LED - Page 1
Forum section: electronics / projects

author: chris0147
author_rank: Newbie
timestamp: July 14, 2018, 07:59:59 pm
content: Hi all,I need your help as I am stuck and I dont know where to start. I have got four blue leds diode that come with dark blue led lights that I really want to get the same led colours for my 3 fans, but I have got no idea what the wavelength for that blue led lights.I have attached the pictures for you to take a look.I am not going to take out the LED diode yet until when I have been advice to do so. I think the wavelength is between 450nm to 470nm but I am not too sure. Do you know how I can find out what is the wavelength for that LEDS?If you know how I can find out what wavelength for that blue leds, I would be very grateful for that useful information.Thanks in advance

author: janoc
author_rank: Super Contributor
timestamp: July 14, 2018, 09:05:26 pm
content: I have replied to your PM. Please, don't spam/PM your problems to random people. That's pretty rude, IMO. I also don't come to you demanding your help with fixing my car.I am copying the PM reply here too so that others don't need to repeat the same thing.Quote
Measure VCE/IC and BVE/IB using DAC - Page 1
Forum section: electronics / projects

author: Fab64
author_rank: Newbie
timestamp: December 21, 2019, 02:54:31 pm
content: Hi all,I need some help from you expert engineers.I need automatically measure VCE / IC and VBE / IB of a big bunch of transistors under specified Vcin and Vbin. See attached circuit diagram #1.Since Vcin and Vbin can be either positive or negatice voltages I chose an ADC (ADS122C04,http://www.ti.com/lit/ds/symlink/ads122c04.pdf) capable to work with such voltages.To stay in the ADC's maximum voltage ranges I tested two different solutions:Use two voltage dividers one for AIN0 and the other for AIN1. But, any small mismatch between resistors values leads to very high errors.Use a virtual ground tied to AIN1 and a single voltage divider for AIN3. This works well to measure VCE and IC, I get values very close to what I measure with my bench multimeter (see output #1).Problem is with IB and VBE. Following the same approach used for IC/VCE I should tie VGND to the base, shorting base and collector.To overcome this issue, I used an IC switch (ADG1636,https://www.analog.com/media/en/technical-documentation/data-sheets/ADG1636.pdf) to switch AIN0, AIN1 between collector and base. I chose that because the low series resistance.See attached circuit diagram #2.Everything works well up VC = 2.6 - 2.7V after that the measured current get smaller than the actual value (see output #2).I understand that the switch has a series resistance which get larger when voltage increases but, since the current on AIN0 and AIN1 is quite small, I thought it shouldn't impact the measurements.I stuck here.I need any advice either to get rid off the switch and read VB/IB without shorting base and collector or make the switch working up to larger voltages.Thank you in advance.