hybridfree/eevblog-posts huggingface dataset:
plz help i wanna measure L primary and L leakage - Page 1
Forum section: electronics / projects

author: navidrct
author_rank: Regular Contributor
timestamp: June 10, 2015, 09:40:09 am
content: hii wanna measure L primary and L leakage but i dont have RLC meter.how can i do that?

author: nfmax
author_rank: Super Contributor
timestamp: June 10, 2015, 09:58:30 am
content: Connect a known capacitance in parallel with the inductor to be measured, feed in a sine wave from a variable frequency generator through a high-ish resistance, and look for the resonant frequency using your 'scope. Or use a bridge!

author: navidrct
author_rank: Regular Contributor
timestamp: June 10, 2015, 10:08:55 am
content: can u explain deeper cause im new in this?a simple circuit probably work for me.thanks

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 10, 2015, 10:30:35 pm
content: http://seventransistorlabs.com/Calc/RLC.htmlUse a frequency generator and oscilloscope. You need a capacitor of suitable value, and may need a resistor (such as in the lower tests, which calculate Q as well).You will have to choose the capacitor based on the expected value of inductance, and what frequency it is expected to work best at. An iron core transformer will hardly do anything at 1MHz, while a ferrite cored inductor will probably look like a piece of wire at 1kHz.Tim

author: BennVenn
author_rank: Regular Contributor
timestamp: June 10, 2015, 10:34:32 pm
content: What equipment do you have? Scope, freq meter, multimeter?

author: navidrct
author_rank: Regular Contributor
timestamp: June 11, 2015, 04:44:09 am
content: i have oscop and multimeter

author: navidrct
author_rank: Regular Contributor
timestamp: June 11, 2015, 04:45:30 am
content: Quote from: T3sl4co1l on June 10, 2015, 10:30:35 pmthanks alot i'll test it
PM3295A OLED upgrade - Page 1
Forum section: electronics / projects

author: leogala
author_rank: Newbie
timestamp: May 05, 2017, 08:10:07 am
content: I upgraded the back-light displays of my PM3295 with OLED displays (see threadhttps://www.eevblog.com/forum/testgear/philips-pm3295-and-pm3295a/), as few people seem to be interested I share my experience and the project.I have to say that I finished the projects 3 months ago and I've already forgot some details... I'll try.The displays are low cost displays coming from china with i2c interface:https://www.aliexpress.com/item/1pcs-0-96-blue-0-96-inch-OLED-module-New-128X64-OLED-LCD-LED-Display-Module/32640627772.html?spm=2114.13010608.0.0.mKDtUGThe original LCD board makes use of a PCE2111 (attached datasheet) decoding a serial message and driving the five LCDs (see page 4 for the timing of the serial message). Unfortunately the serial messages are not documented neither on the scope service manual nor on the PCE2111 datasheet. I managed to reverse engineer the serial protocol, but I've not documented that, however you can understand what I discovered from the arduino source file attached.The idea is to use an arduino to decode the messages and drive the LCDs.I've included a schematic diagram and the arduino code. The code makes use of i2c library and adafruit library for the graphic display control.It is interrupt driven, as soon as the message arrives an interrupt is triggered, the message is decoded and sent to the correct lcd.While I was finishing the project I realized that arduino mini is a bit at its breaking point in terms of speed as the parser time is almost enough to process the next message when e.g. you roll the time base very fast, something faster could be better, anyway it works also with an arduino mini.For the mechanical installation I developed a 3d-printed support (see stl included), it replace the original LCD board almost perfectly.I know that the project is far from being well documented but I did it originally only for me and it works very well on my scope. I hope it can be of help for someone else.I'm available to help anyone willing to try the project but please don't ask me to open again the scope...Good luckLeonardo
pmos driver - Page 1
Forum section: electronics / projects

author: electros6
author_rank: Regular Contributor
timestamp: January 04, 2014, 11:40:12 am
content: Pleas somebody tell me how to drive Pmos . I want linear gate driver voltage to go to negative and positive to drive the pmos into full conduction and cut off linearly

author: dannyf
author_rank: Super Contributor
timestamp: January 04, 2014, 02:22:18 pm
content: How about an amplifier?

author: papo
author_rank: Regular Contributor
timestamp: January 04, 2014, 09:11:00 pm
content: I think it is not quite clear what you are looking for. First of all there exist single-chip gate drivers. These gate drivers allow you to switch fast, i.e. their low impedance deals with the gate charge. Furthermore they can level-shift a low-voltage control signal to the drive-level of the PMOS-gate.Are you looking for suggestions on these or do you want to build a driver circuit out of discrete parts? In any case, maybe some more information on your circuit and on what you want to achieve may be helpful to get answers.Also it is not quite clear to me what you mean by linear.Best regardsMatt
pmos latch switch - Page 1
Forum section: electronics / projects

author: Talseven
author_rank: Newbie
timestamp: September 21, 2020, 10:07:54 am
content: We have a power distribution board for our robot that is responsible for switching power to various modules (controlled via stm32 gpio). The first implementation was pretty simple. we used a high side pmos switch with an nmos controlling the gate of the load switch. Gate of the nmos being directly driven by stm32 (bss138 logic level nmos). The problem that we were facing with this was that whenever the board was reset due to lets say a watch-dog event or ota firmware update. The power to the entire robot was disconnected. So we wanted to build a latching circuit with an on and off circuitry." alt="" class="bbc_img" />The circuit isnt working as intended. The switch M3 is on by default and when M2's gate is driven high the switch is turned off but the latching action isnt acheived. As soon as the M2 gate is let go, M3 turns on again. M5 is actually CMPDM0072A and not BSS138. The circuit works fine on ltspice.At turn on, i know that the pmos is switched on momentarily due to the input voltage appearing across Vsg. Is this the reason why the M3 is turned on by default? since R5 feeds the output voltage back to the gate of M5. But this doesnt explain the turn on behaviour after the M2 gate is driven high and then low, the gate of M5 goes to 1.6V , M4, M1 and M2 are off.

author: Kalvin
author_rank: Super Contributor
timestamp: September 21, 2020, 10:15:20 am
content: Not answering to your question, but something interesting is going to happen if you drive M1 and M2 "on" at the same time.

author: Talseven
author_rank: Newbie
timestamp: September 21, 2020, 11:22:16 am
content: Thank you for pointing it out." alt="" class="bbc_img" />
PMOS replacing - Page 1
Forum section: electronics / projects

author: snx
author_rank: Contributor
timestamp: April 15, 2019, 03:37:25 pm
content: In a microcontroller application, it is desired to power off a 3V3 DCDC converter and all the follwoing devices for saving power. The MCU must be kept alive for simple tasks which not require external devices. For this a 1V8 regulator is used. Also, if the input voltage is insufficient for the dcdc, the device will still run from the 1V8 regulator.For this i found an application note from ST, that lets you switch between two coin cells. They are using the P-Mosfet STS5PF30L. Sadly, this mosfet comes in SO-8 which uses up alot of board space if two are used one is almost the size of my mcu!! . Also its expensive.As a similar replacement i want to use the CSD25310 from TI.Attached you can find the ST app note for two coin cells, and the changes that i would use.Would this wort with a 3V3 and 1V8 Source and my mosfet of choice?

author: Wimberleytech
author_rank: Super Contributor
timestamp: April 15, 2019, 06:36:18 pm
content: Appears to me it would work. The TI mosfet has a lower threshold which is good since you are also lowering one of the cells.

author: Someone
author_rank: Super Contributor
timestamp: April 15, 2019, 11:23:57 pm
content: Some regulators allow you to eliminate the extra switches:https://e2e.ti.com/blogs_/b/powerhouse/archive/2014/08/26/how-to-improve-buck-converter-light-load-efficiency-with-an-ldo-part-1

author: snx
author_rank: Contributor
timestamp: April 16, 2019, 06:38:39 am
content: Yes i'm aware of this circuit. In my case, on the DCDC there are alot of devices (NFC Reader, Motor Drivers etc) all with a shutdown current of a few uA. If they are all kept on power, the current sums up to about 20uAIn my application, the DCDC will be shut down completely, and ONLY the mcu will receive the 1V8. The rest of the parts are not supplied, to get maximum battery life. Even if i would power all devices with 1V8, it would operate multiple devices out of their reccommend specs. So this is sadly no solution for my problem, i need to have mosfet.

author: Someone
author_rank: Super Contributor
timestamp: April 16, 2019, 10:40:30 am
content: Quote from: snx on April 16, 2019, 06:38:39 amIf the 1V8 regulator is only powering your mcu, then you need a power switch for the other (3V3) supply or possibly just a low voltage diode. But the switch on the 1V8 supply may be redundant depending on the 1V8 regulator you use.
PMP bus on non-PIC devices - Page 1
Forum section: electronics / projects

author: ricko_uk
author_rank: Super Contributor
timestamp: May 20, 2022, 09:28:07 pm
content: Hi,I need to drive a TFT display in MCU mode (with 8/9 or 16 bits bus) with very fast refresh rates.What is the bus that Microchip calls "Parallel Master Port" (PMP) called on other 32-bit micros? Micros made by either Microchip (i.e. "Atmel" series) and also by other manufacturers?I am not referring to the EBI, but just to the PMP-type. I think some other manufacturers call it 8080 but cannot find any on "Atmel" devices with that name either...Is it available on "Atmel" micros? PErhaps with another name?If not available on "Atmel" series then (as second options) by other ARM manufacturers?Thank you

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 21, 2022, 12:05:09 am
content: Well, the default is "bit bang", just set the GPIOs as needed and off you go. Good enough for a few MB/s even on AVR (well, afewmight be pushing it, but..). STM's is FSMC; I forget what ATSAMs call it? Some also have more advanced GPIO/PIO modes, like, the PIC32s can drive bus strobes automatically I think?, or when you have DMA you can dump out bus signals and data fairly easily without CPU interaction.Tim

author: ricko_uk
author_rank: Super Contributor
timestamp: May 21, 2022, 01:15:28 am
content: Thank you Timyes I initially thought to just do bit-banging, but it might not leave for much room for the micro to do other things especially if in the future we want to add more features.I was trying to find out others that use "bus-like" control so I can use it with DMA (finding a micro that has both) because I currently have a DSPI/SQI memory and ideally will then transfer images directly to the TFT without using the CPU much, allowing for future expansion and more responsiveness while still showing smooth graphics/animation.Thank you
PMT-xxx Inductors for EN55022 FIlter - Page 1
Forum section: electronics / projects

author: drtaylor
author_rank: Regular Contributor
timestamp: August 04, 2014, 06:21:52 pm
content: I'm designing an option for a product that will be rarely used. I decided just to use an off-the-shelf DC-DC converter. The design needs to pass EN55022 Class A. Since I just wanted to use the cookbook circuit I ran into a snag trying to find out what a PMT-047 inductor is and who manufactures it. Is this some kind of EU standard PN? I know it's a 10uH power inductor in a 0504 SMD package. But who the heck makes it eludes me. I have done all kinds of searches and ironically several of the DC-DC converter manufacturers call out the same inductor. Does anyone know a manufacturer of this part (PMT-047 or PMT 077)?

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 04, 2014, 09:54:12 pm
content: Dave,Can you post the specifications, or a link to the specifications, of the DC/DC converter that you are using?Regards,Jay_Diddy_B

author: Neilm
author_rank: Super Contributor
timestamp: August 05, 2014, 06:18:25 pm
content: +1 for more information.Is this radiated or conducted emissions? Or are you actually referring to the inductor used in the DC-DC converter? If the latter, then that value will come out of the circuit design depending on frequency, on time, output current etc. The actual inductor doesn't matter, although there are a couple things you can do to improve your chances of passing.1) Use a shielded inductor.2) If 1 is too expensive, then make sure the start end (nearest the core) is connected to the EMI hot end - the coils around it will act as a self shield and improve the emissions.3) Pay attention to the core material. Many are made with ferrite and the Ur of that will change with temperature. If what you want is for a filter this will have significant affects of the filter characteristics

author: drtaylor
author_rank: Regular Contributor
timestamp: August 08, 2014, 04:43:28 am
content: I think I have been misunderstood here. I'm using a predesigned module. It is relatively easy to design a CLC pi filter to pass EN55022. That's not my question. I just want to know the manufacturer of a PMT-049 inductor. Not because I can't find suitable inductors for this filter application, but because so many DC-DC module manufacturers call out the PMT-xxx series. Thinking these are so common that they would be dirt cheap since at least 4 DC-DC converter manufacturers are calling them out for input filtering, I just want to find the manufacturer of this specific part. I searched all over the web and cannot figure out who the maker of these parts is.
PNP saturation test the pulse delay - Page 1
Forum section: electronics / projects

author: john23
author_rank: Frequent Contributor
timestamp: August 24, 2024, 08:31:42 am
content: Hello,I have attached two LTSPICE files.There are two kinds of plots,saturated and non saturated shown below.I dont understand where is the significant delay in the signal in the saturated state.How can i see that there is stretch in the non saturated PNP?

author: David Hess
author_rank: Super Contributor
timestamp: August 24, 2024, 11:00:03 am
content: During saturation, excessive minority carriers are injected into the base. When the transistor is then shut off, the excessive minority carriers keep it turned on until they are removed, either by being swept out of the base or by their limited lifetime. The result is a delay time which is added to the off time.

author: wasedadoc
author_rank: Super Contributor
timestamp: August 24, 2024, 01:50:49 pm
content: One of the "tricks" in LSTTL is the effective placing of a Schottky diode from base to collector. Helps divert what would be excessive base current (ie carriers) through the collector instead.https://en.wikipedia.org/wiki/Schottky_transistor

author: john23
author_rank: Frequent Contributor
timestamp: August 24, 2024, 02:40:41 pm
content: Hello,I cannot see in the plots the ,Could you show in my plots where is the delayed off time?How can i see in my plots a situation with no delayed off time?Thanks.

author: Ian.M
author_rank: Super Contributor
timestamp: August 24, 2024, 03:06:03 pm
content: For easier comparison, your 'no-saturation' and saturation circuits in a single sim, together with a circuit implementing wasedadoc's suggestion to use Schottky clamping to desaturate by diverting excess base current.N.B. your 'no-saturation' circuit is impractical (even driving a current controlled load with negligible voltage drop) as at lower Rext it grossly exceeds theMMDT3906IC(max)of 200mA, and also the load current will have large variations from device to device and with temperature.

author: john23
author_rank: Frequent Contributor
timestamp: August 24, 2024, 03:39:13 pm
content: Hello Ian, could you reccomend a shottky diode i could use to desaturate my PNP?Thanks.

author: Ian.M
author_rank: Super Contributor
timestamp: August 24, 2024, 05:42:34 pm
content: Simply use your supplier's parametric search for one with the smallest junction capacitance with adequate reverse voltage and forward current (average at your worst case duty cycle), in a package you are happy with. Generally higher current diodes will have greater junction capacitance and if the diode has too much junction capacitance it can slow down the switching speed considerably as its effect on the base circuit is multiplied by theMiller effect.

author: David Hess
author_rank: Super Contributor
timestamp: August 25, 2024, 07:46:00 am
content: Two normal switching diodes may also be used as a Baker clamp if an additional diode voltage drop in series with the base is acceptable.
pocket sized 12V 300A battery pack - Page 1
Forum section: electronics / projects

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: April 25, 2014, 09:42:30 pm
content: What could possibly go wrong....?http://junopower.com/collections/automobile/products/jumpr-cars-best-friend-jumpstart-cars-on-the-go

author: PedroDaGr8
author_rank: Super Contributor
timestamp: April 25, 2014, 09:55:59 pm
content: Quote from: mikeselectricstuff on April 25, 2014, 09:42:30 pmAlready a thread about it here:https://www.eevblog.com/forum/chat/jumpr-by-junopower/

author: Zepnat
author_rank: Regular Contributor
timestamp: April 25, 2014, 10:43:07 pm
content: You would have better luck with 8 of these, in 2 parallel 4 series formation, but they are twice the price hmm.]http://www.fasttech.com/products/1683801]
PocketBeagle GUI - Page 1
Forum section: electronics / projects

author: Boscoe
author_rank: Frequent Contributor
timestamp: October 11, 2017, 08:59:38 pm
content: Hi all,I picked up one of these because they are cheap understanding it doesn't have any video connection to the MCU. I wanted to created a headless linux server using teamviewer to access the GUI on the PocketBeagle. But the problem is the LXQT GUI distribution doesn't have support for the Pocket and thus doesn't boot when I try. Does anyone know how I could get around this?Thanks

author: hermit
author_rank: Frequent Contributor
timestamp: October 11, 2017, 10:03:18 pm
content: I'm almost ready to pull the trigger on one of these because of price. I have BBB that I haven't really learned yet though. Basically just subbing to the thread because using the 'notify' sends email. Pretty big deficiency in the software or I haven't found the correct settings yet.

author: sycho123321
author_rank: Regular Contributor
timestamp: October 12, 2017, 05:34:15 am
content: I'm not familiar with the pocketbeagle itself but you should just be able to install whatever desktop environment you want over ssh on a supported distro. But if it's going to be a headless server, why waste resources on running a gui?

author: ahbushnell
author_rank: Frequent Contributor
timestamp: October 12, 2017, 01:07:11 pm
content: Quote from: sycho123321 on October 12, 2017, 05:34:15 amHe probably needs a GUI.I run VNC on the BBB. It should run on the Pocketbeagle also.https://arazblog.wordpress.com/2014/06/22/how-to-setup-vnc-server-on-beagle-bone-black-debian/
POE adapter performance - Page 1
Forum section: electronics / projects

author: IconicPCB
author_rank: Super Contributor
timestamp: August 20, 2017, 11:29:01 pm
content: I have been asked to to asses "quality" of a POE adapter consisting of some transient suppression circuitry ( gas arrester and solid state suppression TVS diodes).I understand insertion loss and cross coupling are likely to be an issue.What do the tests consist of?Is there a single test that would offer an insight into how the adapter willperform?Is it possible to use a loop through test ( using two NICs) and perhaps measure BER ?Looking forward to an education...

author: IconicPCB
author_rank: Super Contributor
timestamp: August 21, 2017, 09:50:30 pm
content: bump?

author: nctnico
author_rank: Super Contributor
timestamp: August 21, 2017, 09:55:13 pm
content: I'd use a network analyser to measure the impedance versus frequency. Up to 200MHz is more than enough for 100Mbit ethernet.

author: drussell
author_rank: Super Contributor
timestamp: August 22, 2017, 03:21:41 am
content: Quote from: IconicPCB on August 20, 2017, 11:29:01 pmSure! Put some in operation at your organization for a few years and see what transpires!You need to supply some better metrics as to what constitutes "performance"...Will it supply some voltage to the device? Probably...Will it interfere with data communications on the wire? I certainly hope not!Could you be more specific?
PoE Flyback Transformer Selection - Page 1
Forum section: electronics / projects

author: veryevil
author_rank: Unknown
timestamp: March 05, 2018, 11:32:20 am
content: Hi, I'm new to flyback power supplies and I'm currently designing one for 22-57Vin and 24Vout @ 0.5A or 1A.I'm looking at using Linear Techs ideal diode bridge IC LT4321 (Click Here) and their PoE PD IC LT4276 (Click Here).My plan is for it to be Class 0 or Class 1 with size being the constraint, mainly the transformer.I have found the following transformer and want to check a couple of things: Wurth 7491195224 (Click Here)The winding ratio listed on the datasheet 6:9:9:4 is that N1:N2:N3:N4 meaning primary N1 to secondary N2 is 6:9 Secondary N2 to N3 is 9:9 and Secondary N3 to Auxiliary N4 is 9:4?Also does this provide 2 independent 24V @ 0.5A feeds or is that assuming N2 and N3 are connected in parallel? If not will this transformer give me 24V @ 1A if connected in parallel?It does seem small to be able to handle 24W which is what makes me question it.Cheers

author: veryevil
author_rank: Unknown
timestamp: March 07, 2018, 07:53:05 am
content: One and only Bump.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: March 08, 2018, 01:28:47 am
content: Quote from: veryevil on March 05, 2018, 11:32:20 amHi,The transformer is the correct size. If you look at the 25W demo boards listed here:http://www.linear.com/product/LT4276#demoboardsAnd you look up the transformers, you will see that they are a similar size.The transformer secondary windings should be connected in parallel. This gives the best magnetic coupling between the primary and the secondary.Page 23 of the LT4276 datasheet shows the schematic that you need.It use a Wurth 750314782 transformerLink:http://www.we-online.com/web/en/passive_components_custom_magnetics/products_pbcm/product_spotlight/lt4276.phpRegards,Jay_Diddy_B
POE IEEE 802.3af pad spacing - Page 1
Forum section: electronics / projects

author: Samuel Kälin
author_rank: Newbie
timestamp: October 24, 2019, 12:16:39 pm
content: Hi everyone,I don't use forums very often, so please bear with me.I am designing a Arduino-compatible ESP32-based POE as a hobby project. It is an isolated power design that should fit the IEEE 802.3af standard.The first Prototype is already here and working (mostly).For the second Version I decided to switch the POE-Ethernet jack to a low-profile variant, so that Arduino-Shields actually fit onto it.The best one I found ishttps://www.digikey.ch/product-detail/de/w-rth-elektronik/7498210220A/732-10843-ND/6598165(Datasheet:https://katalog.we-online.de/pbs/datasheet/7498210220A.pdf).In the datasheet it states that it is IEEE 802.3af compliant.Now my problem:The data- and the power-pads are incredibly close together. Wouldn't that lead to a lower than 1500V rms isolation if I lead the data-lines to the other side of the isolation-zone? Do I need to add a Signal-Transformer despite already having one integrated into the Ethernet-Jack?Does anyone have any experience with the required pad-spacing?I appreciate every answer, thanksSamuel
POE Isolated flyback transformer wiring - Page 1
Forum section: electronics / projects

author: tomshirvo
author_rank: Regular Contributor
timestamp: November 05, 2024, 08:40:46 am
content: Hi All,I have this schematic I am using for my own design.They show the use of PA2369NL as the transformer.The issue I have is that they show to use pins 6 & 10 as if they are a single winding.The actual datasheet for the PA2369NL shows that there are two windings that sit inside each other 6 & 9 + 7 & 10.Do you think the schematic has just left out joining pins 7 & 9 to make the winding as one?Thanks in advance.

author: Salitronic
author_rank: Contributor
timestamp: November 05, 2024, 11:15:07 am
content: If available you should check the layout, it is not uncommon that schematic symbols are simplified out of laziness or other practical factors. It could be the footprint assigns pin designator 6 to both pads 6 and 7 and designator 10 to both pads 9 and 10. I've seen this (and admittedly done so myself - although not as misleading as in this case) a few times. Definitely not ideal.However, you are correct that 6 with 7 and 9 with 10 should be paired together.

author: tomshirvo
author_rank: Regular Contributor
timestamp: November 05, 2024, 11:01:20 pm
content: Thanks for your help SalitronicI ended up desoldering the transformer and verifying that use they are setup in parallel.
PoE Isolation and 802.3af/at; IEC60950-1 - Page 1
Forum section: electronics / projects

author: garboui
author_rank: Regular Contributor
timestamp: November 04, 2016, 11:29:50 am
content: Trying to get my head wrapped around the 802.3af and IEC609050-1 specifications for PoE I am unsure is having the PD power supply must be isolated.In the case of an IP phone that is plastic, does not connect to other equipment and <12W it does not require an isolated supply. For higher power devices >12W this seems like not the normal practice. It seems to me that if a product only have the single Ethernet jack and can be designed to pass 1500VAC hipot from chassis to jack contacts then isolation is achieved and standards are satisfied.Has anyone here had experience with certifying PoE devices before?

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 05, 2016, 06:44:14 am
content: Why would a desk phone need more than 12W?
PoE module for Arduino Ethernet  - Page 1
Forum section: electronics / projects

author: SPRX
author_rank: Regular Contributor
timestamp: October 25, 2014, 04:35:17 am
content: I am looking for a PoE module (conforms to the standard IEEE 802.3af) for Arduino Ethernet shield (or for new Yun), but bit surprise and bit hard to find it. Sparkfun has a datasheet for module Ag9000-S, but nowhere to buy the beast.If anyone ever played with PoE with Arduino Ethernet, please help.

author: pmcouto
author_rank: Unknown
timestamp: October 25, 2014, 02:29:39 pm
content: Take a look here:http://au.element14.com/jsp/search/browse.jsp;jsessionid=C4DINJAOLY1JKCWNBBTBFWI?N=0&Ntk=gensearch&Ntt=infomart&Ntx=mode+matchallpartial&exposeLevel2Refinement=true&suggestions=false&ref=globalsearch&_requestid=34083

author: westfw
author_rank: Super Contributor
timestamp: October 25, 2014, 10:48:29 pm
content: Small quantities can be ordered directly from the manufacturer (Silvertel. Who seem to be the only player I've found in this 'low power PoE PD Module" market.)http://silvertel.com/products/poe-power-over-ethernet/26-poe-modules/162-ag9000.html(note the existence of a ~30% cheaper "newer model." I don't know if it's pin-compatible, though.)

author: SPRX
author_rank: Regular Contributor
timestamp: October 26, 2014, 12:19:24 am
content: Thanks Pmcouto and Westfw, and both modules looks quite similar.Ordered couple of newmodel Ag9712-S and Ag9712-M from silvertel.com. These modules are limited to class-0, and is suitable for on-board power requirement. Pins seems compatible.
PoE or DC Jack Priority Circuit - Page 1
Forum section: electronics / projects

author: ElDuderino
author_rank: Newbie
timestamp: April 14, 2025, 08:35:06 pm
content: Hi all,I’m working on a redundant power design based onSilvertel’s app note, using the AG9205 PoE module (+5v_POE on schematic below) and a Murata OKL-T/3-W12P-C 12V to 5V DC/DC converter. PoE should have priority: if both power sources are present, PoE should remain active and inhibit the 12V path via Q1.Here’s my question:Should I add a second diode at the output of the Murata module to prevent backfeeding into the PoE path?Currently, I have one Schottky diode (SS34-E3/57T) at the output of the AG9205 (PoE), but no diode on the output of the Murata module. I’ve noticed some strange behavior when both supplies are present, and I’m wondering if backfeeding from the Murata into the PoE path might be the cause — even with the AG9205 output diode in place.Would adding a second SS34 (after Murata VOUT, before merging into the system +5V rail) solve this? Or is something else likely at play?Any advice appreciated!Thanks.

author: ElDuderino
author_rank: Newbie
timestamp: April 15, 2025, 04:04:13 pm
content: bump!

author: spostma
author_rank: Regular Contributor
timestamp: April 22, 2025, 04:22:15 pm
content: The OKL-T/3-W12 datasheet does not talk about backfeeding, but high efficiency step-down converters generally are of the synchronous bridge-drive type, and those should not be reverse-powered.But I would use a 12V PoE module and let that feed the DC-DC converter to avoid 5V switching.You could use the auxiliary contact of the DC power socket to do the 12V power switching,or use a diode in the 12V supply if you want.
PoE+ Splitter Design - Page 1
Forum section: electronics / projects

author: Jon Chandler
author_rank: Frequent Contributor
timestamp: December 04, 2019, 08:17:39 pm
content: I'm working on a Raspberry Pi 4 project where I may need the higher wattage of PoE+ rather than straight PoE. The design of the enclosure doesn't make it possible to expose the Raspberry Pi's ethernet jack and I have concerns about a non-PoE+ jack supplying PoE+ currents.Conceptually, a splitter seems pretty straight forward. Use a PoE+ RJ-45 jack with magnetics, a Silvertel or similar PoE buck module with required bridge rectifiers connected to the centertaps, and connect the RJ-45 outputs across to a standard RJ-45 jack (pin 1 to pin 1 and so on).Am I overlooking something?Thanks,Jon
PoE with auxiliary input, to isolate or not - Page 1
Forum section: electronics / projects

author: Mad ID
author_rank: Regular Contributor
timestamp: October 21, 2016, 08:28:59 am
content: Hi,I'm designing a device which can be powered either by PoE or auxiliary DC input. Device has no other connections and is housed in a plastic enclosure.Ethernet requires 1500Vrsm isolation. This device will be used in buildings for access control. I was thinking of using regular non-isolated buck which would be fine if the DC input always comes from an isolated AC adapter.I presume that buildings could have 12/24V non-isolated wiring and this would break my isolation?Can someone with more experience with PoE give some suggestion on this matter, i.e. should I use a flyback because of the aux DC input?There are solutions like LM5071 which has PoE controller and PWM IC with support to aux input..Thanks.
Point to Multi-Point Communication - Page 1
Forum section: electronics / projects

author: jmdejoanelli
author_rank: Contributor
timestamp: March 02, 2013, 10:45:17 am
content: Hi all,So I've been wondering how point to multipoint communication works. I have had a bit of a google around, and it seems most topologies use a system of time division multiplexing which makes perfect sense. But how does a new device connecting to the network know which time slice to use?I'm guessing some kind of handshaking occurs at connection, where the client introduces itself to the host and the host allocates a frequency channel or time slice to that client. But what happens if two clients happen to try to connect to the host at the same time? Wont the handshaking be corrupted?Any help clearing this up for me would be appreciated.Thanks,Josef

author: PA0PBZ
author_rank: Super Contributor
timestamp: March 02, 2013, 10:49:31 am
content: These kind of problems are mostly solved by a random wait time when a collision occurs, so that both clients will not try again at the same time.

author: Rerouter
author_rank: Super Contributor
timestamp: March 02, 2013, 01:34:30 pm
content: or you could use similar to the can bus, where following a signal to say its initialised on the line, it spits out its serial number and reads back while doing it, if any high bits are read back as low, it waits till the other devices with a lower serial number is allocated and tries again (though with can it has a set ID, but serial numbers can be a convenient non repeating id)
Poker Chip Scale - Page 1
Forum section: electronics / projects

author: Dellyjoe
author_rank: Regular Contributor
timestamp: September 03, 2024, 11:39:34 pm
content: Hello everyone,I’m excited to dive back into my project phase, and recently, I’ve developed a keen interest in poker.I’m planning to build a scale that can weigh poker chips and determine their value. Imagine a rectangular felt mat with designated areas for $1, $5, $25, and $100 chips. When you place the chips in their respective areas, the scale will calculate the weight, determine the value, and display your total chip value.This will be phase one of the project. It’s straightforward and should help me get back into the swing of things.In phase two, I aim to add a feature for tracking turns. When it’s my turn, the system will announce how much I’ve contributed to the pot, so players don’t have to manually calculate the total.Previously, I’ve used a Teensy 4.1 microcontroller, and I plan to use it again for this project. However, I’m looking for a scale that can detect differences as small as 10 grams. Does anyone have recommendations for such scales?Thanks in advance for your help!

author: Dellyjoe
author_rank: Regular Contributor
timestamp: September 04, 2024, 01:27:09 am
content: Maybe I can usehttps://www.adafruit.com/product/4540?gad_source=1&gclid=CjwKCAjw59q2BhBOEiwAKc0ijYyKOkbL-aU_GcItk23YGDMj0K-TjVh6OhVCjrJKCfo-Gr5hsWSTPhoCEJsQAvD_BwEbut I also sawhttps://www.amazon.com/Icstation-BF350-Strain-Pressure-Sensor/dp/B01MY6F9EN/ref=pd_bxgy_d_sccl_1/131-7688119-4447769?pd_rd_w=rvMFd&content-id=amzn1.sym.f7fa8b58-6436-47b8-8741-9e90c231669e&pf_rd_p=f7fa8b58-6436-47b8-8741-9e90c231669e&pf_rd_r=HJCNT2Q57SSCCM2Y49A2&pd_rd_wg=Lbojr&pd_rd_r=642c4e58-527b-43c9-8f73-0959a33f0595&pd_rd_i=B01MY6F9EN&psc=1the amazon ones look really small and not sure how well they would work.Anyone have any suggestions on Load cells?Thanks in advance,Joe
Polarity of Magnetics (Ethernet) - Page 1
Forum section: electronics / projects

author: GFTCTP
author_rank: Newbie
timestamp: March 18, 2021, 02:10:40 pm
content: Hello everyone,I'm designing a ethernet PCB with LAN9354 and i have a doubt in polarity of magnetics.The evaluation board schematic has the follow wiring (between PHY/SWITCH and MAGNETICS):And the connector that I would be use:My doubt: In evaluation board, the polarity in magnetics is on TD+ and RD+, and the polarity of chock mode is near to RJ45 side. In my connector JXD0-2005NL, the polarity of magnetics is oposit... Whats wiring option is correct (option1 or option2)?Thanks in advance.

author: ajb
author_rank: Super Contributor
timestamp: March 18, 2021, 02:46:16 pm
content: The magnetics don't care about the polarity of the pairs, in fact the PHY doesn't care either (well, maybe some PHYs do, but that would be very unusual). Even if you use the 'right' polarity throughout your design, it may end up connected to another device that has the polarity swapped, so it really doesn't matter. PHYs are generally designed to tolerate this, so you're free to swap polarity within pairs in whatever way makes your layout easier. You can even swap TX and RX pairs if your PHY supports auto MDI-X, which most do these days, but check the datasheet to be sure. Usually it's enabled by default, if not you can use the PHY's management interface to configure it.EDIT: just noticed your part number, the LAN9354 actually calls out automatic polarity correction along with auto MDI-X in the first page of the datasheet. That's unusual, most devices don't even mention polarity correction because it's just assumed, except maybe in calling out a bit in a status register that indicates the link polarity. I guess someone wanted to fill out the feature list a little to make it look better

author: jonpaul
author_rank: Super Contributor
timestamp: March 18, 2021, 03:46:53 pm
content: The transformer for isolation and Z match is center tapped and the dots show the winding starts. The windings are correct.Ethernet and many other protocols are using Manchester, phase or other modulation that is not ploarity of signal sensitive.Finally the CM choles dots show the windings are bifilar and wound in the same sense to forma a CM choke.However the CM choke dots can be either to left or right as long as both are in the same direction.Hope this clarifies,Jon

author: nctnico
author_rank: Super Contributor
timestamp: March 18, 2021, 10:43:30 pm
content: Quote from: ajb on March 18, 2021, 02:46:16 pmI'd be careful with swapping polarity. By definition all ethernet cabling has a fixed polarity. Maybe it matters for 10Mbit which uses a different encoding.To the OP: polarity of transformers doesn't matter for as long as the dots line up with the same signal (+in to +out). Also make sure to include TVS diodes and the option to insert EMI suppression beads in the lines between between the magnetics and the phy. Otherwise you might not pass testing as this crappy range of (formerly SMCS) ethernet chips push out a lot of HF junk.
Pololu VNH5019A, 8.5V at PWM = 0? - Page 1
Forum section: electronics / projects

author: MartinFO
author_rank: Contributor
timestamp: April 10, 2025, 04:38:54 pm
content: Hi GuysThe application/background is not important, but usually it is interesting to know, so here you have it.I have designed a tester for proportional valves, using the ESP32. The valve runs on 24V and takes a -10 to 10V signal input (0-10V with switching polarity). It also have a similar feedback signal, which I measure with a ADS1115 (with a voltage divider to adjust to VDD). I use the VNH5019A (on a Pololu module,https://www.pololu.com/product/1451) to generate the control signal. That way I can have 24V as the input and limit the range to -10 to 10V with the PWM signal.I have strange problem though. When INA and INB are LOW, the output is 0V (great), when I switch one of them HIGH the output goes to 8.5V (negative if I switch INA and INB), eventhough the PWM is 0. If I sweep the PWM 0-100%, the output sweeps from 8.5-24V. I cannot get it below 8.5V.I have tested with two different module - same results. I have measured the PWM to 0.0 - 3.3V. The module is powered (VDD) via the ESP32 3.3V pin.I have only connected VDD, GND (the GND is common, but the other pin is not connected) INA, INB and PWM. I tried pulling ENA/ENB high via a 10kO resistor, but that did nothing.I have tried different PWM settings, higher resolution and lower frequency, here is an example.#define PWM_CHANNEL 0#define PWM_FREQ 20000 // 20 kHz, suitable for motor control#define PWM_RESOLUTION 8 // 8-bit (0-255)#define PWM_PIN 5 // PWM for VNH5019A#define IN_A 18 // Direction pin A#define IN_B 19 // Direction pin B// Set up PWM on PWM_PINledcSetup(PWM_CHANNEL, PWM_FREQ, PWM_RESOLUTION);ledcAttachPin(PWM_PIN, PWM_CHANNEL);For testing I use this in the loop (with a delay when finished):for (int duty = 0; duty <= 255; duty++) {ledcWrite(PWM_CHANNEL, duty);delay(10000 / 256); // ~39ms per step for 10s total sweep}Do you have any idea of what could be the issue?Br. Martin
Poly fuse in old school fuse form factor - Page 1
Forum section: electronics / projects

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 23, 2015, 05:40:49 am
content: Are there resettable fuses that fit into standard AGC 6x32mm or the shorter 6x20mm fuse holders?This seems like a great idea to have a resettable fuse you could install in older equipment.I guess you could build one with a through hole part and a dowel, or something else.
Polymer Electrolytic Ripple Current Low Frequency - Page 1
Forum section: electronics / projects

author: KarlM
author_rank: Newbie
timestamp: August 29, 2018, 03:35:26 pm
content: I often use polymer electrolytic caps in power supply designs because of their high ripple current handling. I am looking at a new design with multiple frequency components in the current and noticed how the ripple current rating drops significantly as the frequency reduces. One for example is 4Arms at 100kHz but only 0.2A at 120Hz, 1/20 reduction.Looking at normal electrolytics the ripple current rating at 100kHz is lower but the drop is much less as the frequency reduces. 2Arms at 100kHz and 1A at 120Hz, only 1/2 reduction.Clearly the polymer caps are optimised for the higher frequencies in switch mode power supplies but was wondering if any one knows the mechanism within the capacitor that is behind this?Karl

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 29, 2018, 05:12:32 pm
content: Sure. Polymer values are much smaller; have you checked what ripple voltage would be at that frequency?This brings dielectric loss into play. Dielectric loss looks like an R+C in parallel with the main C, with the extra C being small (about tan 𝛿 times main C).Or if you stick with ESR (beingequivalentseries resistance), the ESR rises at low frequencies.So the key is that the ripple voltage rises at low frequencies, while the Q factor stays roughly constant (Q ~= 1 / tan 𝛿).Knowing Q factor, you can calculate loss. Find the reactive power, then multiply by tan 𝛿 to get the real power (loss). Reactive power is V*I (more or less), so once you know ripple and capacitance, you know this.Tim

author: David Hess
author_rank: Super Contributor
timestamp: August 29, 2018, 06:30:54 pm
content: Like T3sl4co1l says, ESR varies with frequency and is higher at lower frequencies. In demanding applications if it is not specified at the operating frequency, then it should be verified through measurement under the expected operating conditions.
Polyolefin "marine" heat shrink - Page 1
Forum section: electronics / projects

author: jaapweel
author_rank: Newbie
timestamp: April 14, 2013, 08:12:45 pm
content: The other day, I was at Harbor Freight (a discount tool store, for those not in the US), and I picked up a box of assorted bits of heat shrink. What I didn't notice when I grabbed it off the shelf is that it was labeled as "marine" heat shrink. And believe it or not, this stuff is actually better than regular heat shrink.For one thing, it's polyolefin rather than PVC. As anybody knows who has tried to shrink PVC heat shrink with a lighter, the temperature where it starts to shrink is awfully close to the temperature where it starts to decompose into smelly and no doubt unhealthy gases. With the polyolefin, I was not able to get it to that point with a lighter. That makes it much easier to work with if you don't have a hot air station on hand.Also, it shrinks more, which is useful for things where you have a cable that already has connectors on both sides and you need to get the heat shrink all the way down to the diameter of the cable. For instance, in the attached picture, I used a piece of heat shrink to permanently attach an old-Magsafe-to-new-Magsafe adapter to an Apple old-Magsafe cable, also reinforcing the cable at the point where the shoddy Apple strain relief always fails. The smallest heat tubing in the box that just fit around the adapter actually shrank down almost as far as the cable. There's a small gap, but that filled up with the hot-melt adhesive that lines the inside of the tubing.
polypropylene capacitor capacity  - Page 1
Forum section: electronics / projects

author: sdancer75
author_rank: Frequent Contributor
timestamp: October 09, 2025, 10:28:37 am
content: What is the capacity of this part 1μF or 0.1μF ?Thank you

author: moffy
author_rank: Super Contributor
timestamp: October 09, 2025, 10:48:07 am
content: 105 = 1uF

author: sdancer75
author_rank: Frequent Contributor
timestamp: October 09, 2025, 10:53:13 am
content: Quote from: moffy on October 09, 2025, 10:48:07 amI think that this is the climactic class, i.ehttps://www.acdcshop.gr/content/EPCOS-B3292_series.pdfSpecificationsManufacturer EPCOSCapacitor type polypropyleneCapacitor kind X2Capacitance 330nFOperating voltage 305V ACTerminal pitch 22.5mmTolerance ±20%Body dimensions 6 x 15 x 26.5mmLeads dimensions len. 6mmClimate class 40/105/56 (IEC 60068-1)Mounting THT

author: gamalot
author_rank: Super Contributor
timestamp: October 09, 2025, 10:56:59 am
content: Here's everything you need.https://au.element14.com/epcos/b32922c3224k289/cap-0-22-f-10-pp/dp/2525341

author: gamalot
author_rank: Super Contributor
timestamp: October 09, 2025, 10:57:51 am
content: Quote from: sdancer75 on October 09, 2025, 10:53:13 amYou're fast! but wrong

author: sdancer75
author_rank: Frequent Contributor
timestamp: October 09, 2025, 11:01:41 am
content: Quote from: gamalot on October 09, 2025, 10:57:51 amYou are saying that is 0.22μF?

author: gamalot
author_rank: Super Contributor
timestamp: October 09, 2025, 11:03:05 am
content: Quote from: sdancer75 on October 09, 2025, 11:01:41 amNever mind, I amde a mistake ....

author: gamalot
author_rank: Super Contributor
timestamp: October 09, 2025, 11:07:42 am
content: Those text on the top side, I couldn't read them clear, if it is something like H4-U1, then it is most like 0.1uF one.

author: sdancer75
author_rank: Frequent Contributor
timestamp: October 09, 2025, 11:11:47 am
content: Quote from: gamalot on October 09, 2025, 11:07:42 amI read the same H4-U1, but I can not understand the marking's meaning. How can I translate the H4-U1 to 0.1μF? Any guide/info about this?

author: gamalot
author_rank: Super Contributor
timestamp: October 09, 2025, 11:13:36 am
content: Quote from: sdancer75 on October 09, 2025, 11:11:47 amU1 = u1 = 0u1 = 0.1u

author: sdancer75
author_rank: Frequent Contributor
timestamp: October 09, 2025, 11:19:52 am
content: Quote from: gamalot on October 09, 2025, 11:13:36 amExcellent thank you :-)
Polystyrene capacitor voltage ratings "GX" - Page 1
Forum section: electronics / projects

author: mc172
author_rank: Frequent Contributor
timestamp: March 22, 2021, 08:28:48 pm
content: I've got some axial polystyrene capacitors that got given to me in a bundle of other bits and bobs. All that's written on them is the value (510 pF) and "GX", which I'm assuming is a voltage rating. Does anyone know what this means please?

author: srb1954
author_rank: Super Contributor
timestamp: March 23, 2021, 05:43:08 am
content: Quote from: mc172 on March 22, 2021, 08:28:48 pmThe G might represent the tolerance: 2%.

author: lordium
author_rank: Regular Contributor
timestamp: March 23, 2021, 09:20:25 am
content: Yes the G is 2%, the X was harder to look up since not that common it seems, but some datasheets says the second one is voltage range (Z=30V, X=160V, V=400V, U=630V etc)

author: mc172
author_rank: Frequent Contributor
timestamp: March 23, 2021, 10:16:04 pm
content: Brilliant, thanks chaps.
Pomona 6442 13mm Tip Reach, SMD Micro Grabber - Page 1
Forum section: electronics / projects

author: ebclr
author_rank: Super Contributor
timestamp: October 18, 2016, 04:23:03 pm
content: I really nee thatBut no way to pay 390 USDhttps://www.amazon.com/Pomona-6442-Reach-Micro-Grabber/dp/B00CO9E236%3FSubscriptionId%3DAKIAIQOZMKEPEBLOIJBA%26tag%3Dterapeak08-20%26linkCode%3Dxm2%26camp%3D2025%26creative%3D165953%26creativeASIN%3DB00CO9E236