hybridfree/eevblog-posts huggingface dataset:
purpose of OPAMP in biasing TGA2227 - Page 1
Forum section: electronics / projects

author: john23
author_rank: Frequent Contributor
timestamp: September 04, 2024, 05:52:58 pm
content: Hello,I have created a circuit as shown below based on a tottaly wrong circuit i was given.My circuit created a delay from M12 and P12.LTSPICE file is attached.This circuit is supposed to bias the gate of TGA2227 with -2.5V.So i ahve -12V and i can create out of it -2.5V is many ways.I could do voltage divider, I can use LM337 regulator.What is the logic in using opamp and then resistor and zener diode to create -2.5V on the gate?(The schematics is wrong, i just need to understand the logic)Thanks.https://www.qorvo.com/products/p/TGA2227-SM#documents

author: David Hess
author_rank: Super Contributor
timestamp: September 05, 2024, 12:31:47 am
content: Quote from: john23 on September 04, 2024, 05:52:58 pmUsing an operational amplifier has the advantage of providing a very low impedance output, because the output resistance of the operational amplifier is divided by the excess gain.An operational amplifier can be combined with a zener diode in such a way that it not only buffers th e zener diode, but also biases it at a constant current.

author: john23
author_rank: Frequent Contributor
timestamp: September 05, 2024, 08:59:18 am
content: Hello, The opamp Is being used as a comparator.I have +12V pulse which come after -12V pulse.from +12V is need to supply the +5V for the drain of the amplifier.From the -12V I need to supply the -2.5V at the gate of the amplifier.What logic do you reccomend for the gate supllying?I need the negative input to be larger then the positive input so my output will be -12V.with zenner diode my output voltage will be constant.How do you reccomend to convert -12V output into -2.5V with the ability to tune the gate voltage?(keeping the low impedance advantage)I need somehow to do that Vg will be zero when M12 has not yet arived.I am not sure how to do it logiccaly.Thanks.Thanks.
Purpose of resistor on this circuit MOSFET source - Page 1
Forum section: electronics / projects

author: modnar
author_rank: Newbie
timestamp: October 13, 2017, 01:11:23 pm
content: Hi all,Firstly, I recently brought an oscilloscope (Rigol DS1054Z) thanks to a lot of information on this forum and couldn't be happier right now.I was wondering, what is the purpose of the resistor on this circuit, it's connected in between the source pin (N-Chan. MOSFET) and GND. The writing says "5W0=15RJ" - I did assume 15 ohms but the multi meter reads/flickers between 0.5 & 0.6 ohms. My multi meter connected together reads 0.5 ohms which made me wonder if this was actually a 0.15 ohms.So I guess there's 2 questions here, what value is this resistor really and secondly what purpose does it have?It's driving an 24V DC motor so I assume it's to help with some sort of oscillation ??Thanks!

author: RobK_NL
author_rank: Frequent Contributor
timestamp: October 13, 2017, 01:21:46 pm
content: My first guess would be that this resistor is used to measure the current through the motor. But without knowing anything about the rest of the circuit, it's just that: a guess.

author: rstofer
author_rank: Super Contributor
timestamp: October 13, 2017, 02:59:33 pm
content: Mouser shows the 15RJ resistor as 15 Ohms 2 Watt wirewound 5%

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 13, 2017, 05:32:31 pm
content: Yes, current limiting. How much depends on the applied Vg(on).Tim

author: modnar
author_rank: Newbie
timestamp: October 14, 2017, 07:56:41 am
content: There was more to it than I first thought. Both sides of that resistor go off, make there way through a path of resistors npn pnp caps until it hit's a CD4017BM Decade counter. Trying to put it on paper to see what's happening.Quote from: rstofer on October 13, 2017, 02:59:33 pmI did check that too, but I've a funny feeling this is a smaller resistor. I'm torn between thinking it's a 0.5 or 0.15 but then I'd expect R5 or R15. I've ordered some either way. I tried a 15 Ohms in my circuit but there wasn't enough to drive the motor. Wouldn't turn.

author: eblc1388
author_rank: Frequent Contributor
timestamp: October 14, 2017, 08:04:33 am
content: 5W 0.15R JSo, my bet is 0.15 ohm, 5W resistor.

author: ocset
author_rank: Super Contributor
timestamp: October 14, 2017, 11:40:43 am
content: I was going to say it might be part of an inrush limiting circuit, as dc motors a re just short circuits until they build up enough back emf by spinning fast enough. But the decade counter...ummm...is this motor being turned on and off in service?

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 14, 2017, 02:19:38 pm
content: Current sense resistor.

author: Zero999
author_rank: Super Contributor
timestamp: October 14, 2017, 10:38:36 pm
content: Is anything else connected to the source of the MOSFET?
Purpose of shorted CT through PCB? - Page 1
Forum section: electronics / projects

author: mluna
author_rank: Newbie
timestamp: March 19, 2020, 12:53:32 am
content: I was fixing an online UPS (APC brand), in which I came across this CT (ct2), shorted through the PCB on its primary. I wonder what's the purpose of doing this if there's no way current flow trough it so it can be sensed.

author: ahbushnell
author_rank: Frequent Contributor
timestamp: March 19, 2020, 01:03:04 am
content: Good question. Maybe the current divides between the trace and the transformer? This allows a smaller transformer?

author: Someone
author_rank: Super Contributor
timestamp: March 19, 2020, 01:15:06 am
content: PCB trace as shunt.

author: David Hess
author_rank: Super Contributor
timestamp: March 20, 2020, 05:19:46 am
content: Based on using all of the connector pins, the traces will operate as a shunt resistance across the current transformer.
purpose of this resistor in a NAB tape preamplifier? - Page 1
Forum section: electronics / projects

author: SArepairman
author_rank: Frequent Contributor
timestamp: February 22, 2014, 01:00:06 am
content: Taken from the Ti datasheet.What is the purpose of the resistor in series with the 15nF capacitor in the feedback loop? I typically see feedback capacitors to reduce circuit bandwidth but why the series resistor? And the point of the 47UF capacitor to ground?

author: David_AVD
author_rank: Super Contributor
timestamp: February 22, 2014, 01:32:12 am
content: The 47uF acts as a low-cut filter. (more feedback at lower frequencies)I'd say that the 3.6K is to tailor the hi-cut response of the 15nF capacitor to better approximate the required curve.

author: SArepairman
author_rank: Frequent Contributor
timestamp: February 22, 2014, 02:45:04 am
content: Quote from: David_AVD on February 22, 2014, 01:32:12 amOh so its sort of turning a inverting amplifier into a high pass filter? (the 47uF)What do yoou mean by required curve?

author: David_AVD
author_rank: Super Contributor
timestamp: February 22, 2014, 02:56:43 am
content: The 47uF becomes less effective at low frequencies, so that means more feedback down low hence the high-pass effect.I believe the tape head requires equalisation as its own frequency response is not very flat. Google for tape head equalisation curve.
Purpose of welding transformer laminations together? - Page 1
Forum section: electronics / projects

author: rcbuck
author_rank: Frequent Contributor
timestamp: August 29, 2023, 10:17:58 pm
content: I took a non-working 18V, 20VA plug in transformer apart. I think it is the type that would normally be used for door bells or house number signs. They run 24/7 for years on end. This is the transformer:https://www.ebay.com/p/17041547028When I got it apart I found it is not repairable. Instead of the core laminations being interleaved, the I sections are butted up against the E sections. The I sections were then welded to the E sections so the core cannot be taken apart.Why would they do that? I would think the transformer would be less efficient with this type of construction. I have never seen this before. Even microwave oven transformers aren't welded together.

author: thm_w
author_rank: Super Contributor
timestamp: August 29, 2023, 10:20:33 pm
content: MOT cores are usually welded:https://electronics.stackexchange.com/questions/262187/why-there-is-welding-on-some-iron-transformers-corehttps://www.eevblog.com/forum/beginners/

author: Benta
author_rank: Super Contributor
timestamp: August 29, 2023, 10:35:09 pm
content: Quote from: rcbuck on August 29, 2023, 10:17:58 pmSimple. Much cheaper in production compared to mucking around with bolts and brackets. All the wall-warts, cheap chargers etc. I've seen have this.Magnetically there's a bit more loss, but those kind of transformers are running on the edge anyway.Interleaved EI transformers are a thing of the past, except for high power or audio.

author: rcbuck
author_rank: Frequent Contributor
timestamp: August 30, 2023, 01:59:29 am
content: Thanks for the answers. I knew some of the microwave transformers were welded but didn't think it was most of them.I've taken wall-warts apart but never paid any attention to the transformer. I'll look at it the next time I open one up.

author: jonpaul
author_rank: Super Contributor
timestamp: August 30, 2023, 03:25:56 am
content: Low cost, high volume fast assemby of stacked lams, by special robot welding machine, without EI lam interleave.Typically volumes 100K ..1M /year.Higher eddy losses,but as most are runhih on BH, closer to saturation sat,. Total losses Pcu, Pfe losses can be 10..20%Used in MOT microwave ovens, UPS uninterruptable PSU, old type linear (magnetic) arc and fluorescent lamp ballasts.The market remains very strong for mains frequency inductors, transformers and motors made of (14 mil) silicon steel laminationsamicalmentJon
Push Button Amplifier Controls? - Page 1
Forum section: electronics / projects

author: Chris56000
author_rank: Frequent Contributor
timestamp: May 03, 2021, 05:57:44 pm
content: Hi!Does anybody know where I can find project ideas for d.i.y. push–button up/down controls for volume, bass, treble and balance as well as push–button function selection?I know about the MAX5406/MAX5486 i.c.'s but the packages they come in are far too small for my eyesight!I'm looking for something either PIC or Arduino based, ideally with a bar–graph type LCD interface for a graphics LCD module, ideally with DIP or reasonably large smd audio controller i.c.'s without horrendous number of pins (one i.c. per function is fine)?Chris Williams
Push-Pull transformer calculation - Page 1
Forum section: electronics / projects

author: jamhough22
author_rank: Newbie
timestamp: January 14, 2021, 05:38:40 pm
content: Hi all, i’m new hereIm refining my design for a dc-dc isolated push-pull converter, that will boost 12v dc to +- 32.5v or 65v up to 300W. But need help with one formula for the transformer.Npri =Vin nomx10^8———————(4 x f x Bmax x Ac)Wherevin nom - nominal input voltage4 - is for square wave input switchingf - switching frequencyBmax - maximum flux densityAc - effective cross sectional areaIm using dual primary and secondary windings, I have made and tested a transformer already but played it safe in my design. However, i want optimise my design to fully utilise the core but not saturate it. (ETD39)Core half:https://uk.farnell.com/ferroxcube/etd39-20-13-3c90/ferrite-core-etd-3c90/dp/3056399?CMP=i-ddd7-00001003Bobbin:https://uk.farnell.com/ferroxcube/cph-etd39-1s-16p-c/bobbin-etd39-1-section-16pin/dp/3056314?CMP=i-ddd7-00001003My question is what is the switching frequency?Is it the frequency of a single winding or both?The mosfets are switching at 50khz (with dead-time) will the frequency be 100khz or 50khz?Thanks,James.

author: fourtytwo42
author_rank: Super Contributor
timestamp: January 15, 2021, 08:18:00 pm
content: Tis the period of the peak flux density in one direction to the same in the opposite direction.

author: Benta
author_rank: Super Contributor
timestamp: January 15, 2021, 09:41:23 pm
content: Your questions are impossible to answer without knowing the topology of your design. I can give general a comment though: using two primaries is mostly not the best way for efficiency: double the amount of copper, double resistance, double filling of the bobbin.But there are rare instances where it can make sense.

author: jamhough22
author_rank: Newbie
timestamp: January 15, 2021, 11:37:54 pm
content: Benta - i did say it is a push pull, centre tapped primaries to v+, switching alternately each winding to ground, the core will hence have alternating pulses in opposite directions. I currently have 3 windings for each primary and 20 turns on the secondary.

author: Benta
author_rank: Super Contributor
timestamp: January 15, 2021, 11:56:14 pm
content: Something like this (except your secondaries are different)?Magnetically very inefficient regarding core size and copper use.

author: jamhough22
author_rank: Newbie
timestamp: January 16, 2021, 11:28:26 am
content: Yes just like that, i might even split the secondaries for an option of a split rail supply if i ever need one.During testing on my current setup i have managed to get over 80% efficiency and thats just with breadboard and soldered wires everywhere, cannot test at full load tho in this setup.

author: strawberry
author_rank: Super Contributor
timestamp: January 16, 2021, 11:40:24 am
content: saturation is not affected by secondary load but by primary voltage and PWM duty cyclemonitor primary current waveforms with scope if saturation happen at max voltage and duty cycle and temperaturegood calculator for smps ExcellentIT
Pushbutton and Time-based Power On/Off for Arduino - Page 1
Forum section: electronics / projects

author: wholder
author_rank: Regular Contributor
timestamp: June 11, 2017, 09:16:14 pm
content: I’ve designed a small circuit you can build which lets you power an Arduino On, or Off by pushing a button, or responding to an external signal, such as from a sensor. You can also use this circuit with a Real Time Clock (RTC) module to power on an Arduino at a particular time, or date and time and then lets the Arduino power itself off when done. The circuit consumes only microAmps when off, so you can use it to build systems that can run for months using ordinary batteries.You can find out more by watching the following videos on myYouTube Channel:Or use the following two links to read the more in-depth articles that accompany these videos on my Blog,Wayne's Tinkering Page:Article: Pushbutton Power Switch for ArduinoArticle: Time-based and Low Power Techniques for ArduinoI've written an Arduino library to make implementing pushbutton power control easy and a separate Arduino library for the DS3231 RTC module to simplify time-based control as well. I hope you find these useful. If so, please comment here, or on the YouTube videos.Wayne
Putting powerLED/hddLED/reset sw/power sw on the back of ATX computer case. - Page 1
Forum section: electronics / projects

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: February 23, 2022, 04:50:53 am
content: I have a old beige box that I use to torment hardware and software. I sometimes find that I would like to have those front panel switches on the back.I've got this: (a two-switch/two-LED kit that I will eventually mount into a blank expansion card bracket.)https://www.ebay.com.au/itm/403479799774However, I would still like to keep using the front switches and LEDs if possible. Do shortish 'Y' spitters for this pin pitch exist?Can you think of any problems that I am likely to strike by piggy-backing the LEDs and switches?

author: SeanB
author_rank: Super Contributor
timestamp: February 23, 2022, 05:16:29 am
content: Switches no problem, and the LED's just put a 220R resistor in series with the leads for the front and back LED's, so that they will at least illuminate somewhat evenly.
PV monitor design help - Page 1
Forum section: electronics / projects

author: texane
author_rank: Regular Contributor
timestamp: June 12, 2016, 07:13:23 am
content: Hi everyone,the summer is coming, and I set a small PV installation consisting ofa small photovoltaic panel, a 12V 6ah battery and a charge controller(http://www.steca.com/index.php?Steca-Solsum-F-en).I would like to add a monitor to measure PV, battery and load voltageand current.It looked easy at first, and I designed a microcontroller based circuit.It is powered by the battery, and connects all thef PV-, BAT- and LOAD-together, to have a common reference point with acted as my circuit GND.But then, I looked inside the the PV charge controller. I noticed that itdoes not connect the PV-, BAT- and LOAD- together. Instead, it connectsPV+, BAT+ and LOAD+ together, allowing to use low side power mosfets withreduced RDS(on). Anyway, PV-, BAT- and LOAD- must not be connected together,and my circuit is thus invalid !The following diagram may help understanding the setup:Thus, I must use PV+, LOAD+ and BAT+ as a common point. For my circuit 5Vpower supply, I can use a polarized DC/DC. But then, my circuit VSS is such thatPV- ~= -14V, and LOAD-, BAT- = -7V. It makes the voltage measurement stageexpensive to design compared with an unipolar configuration. Esp. since I now haveto find bipolar instrumentation amplifiers with a negative common voltage range largeengouh ...The circuit I have in mind:How would you design the voltage measurement stage ?Any advice is welcome !Cheers,
PWB Bed Of Nails Tester Project, Frequency Counter, ADC, and FSM - Page 1
Forum section: electronics / projects

author: Luminax
author_rank: Regular Contributor
timestamp: March 01, 2017, 05:21:57 am
content: Greetings esteemed engineers and hobbyist folks at this great forum!I am currently building/attempting to build a tester which is proposed to be Stand-Alone (No other equipments/Computer/etc required) Controller connected to the Bed of Nails jig in question, and is proposed to be centered around the Mid to High range PIC microcontroller.I was torn between posting this topic here or the Microcontroller sub board, but as I will be discussing other topics such as Peak Detect-and-Hold circuit and just life in general(you know...rants...) I decided to post it here.This is more of an invitation to discussion post in which I'll post my progress as I have time to and asks for advice and pointers from you folks and discuss the various problems and pitfalls and hopefully finding the right solutions for it.TL;DRMy project consists of the following :1) Pin Jig to connect to test points on the PWB Under Test2) Main controller system, based on PIC18/PIC24/PIC323) Frequency Counter either using a sequential logic synchronous counter (ex: 74LV161) in a dual 'capture' mode and feeding the result to the control system or:4) Frequency Counter using the internal ECCP(Enhanced Capture/Compare/PWM) module of the PIC Microcontroller5) ADC Interface to read various points on the PWB Under Test (3~5 points, either using multiplexed single ADC using external multiplexer, or connecting 3~5 ADC channels and multiplexing in software6) Switching/Multiplexing module for emulating switch press and various other stuffsThe PWB(s) Under Test are mostly IR-remote with the following typical specifications :1) Supply power VDD of 2.4~3.2 (Typical/Function Spec states 3.0 +- 0.05)2) IR Carrier Frequency of roughly 37.9kHz3) Ceramic Resonator ranging from 1MHz to (allegedly highest) 8MHz4) Secondary Crystal Oscillator (or Primary in the case of some PWB) of the RTC type (32.768kHz) usually /128-ed to provide the 256Hz5) Infrared LED usually PWMed from a typical consumer-grade microcontroller (Panasonic, Renesas, etc) through a transistor and a current limiting resistor in the range of 1~2.7 OhmAnd so I begin this post as a journey into the whole tangled mess of product/system design with the following goal in mind:1) Creating an at least readable technical documents on the whole process and/or Project planning documentation2) Documents the whole prototyping/testing process3) Learn something out of all this!I am currently looking back at FSM and implementing it phase-by-phase throughout the entire process...she's a long road to travel... and with that, I go to my lunch break
PWL Editor - for LTSpice, Microcap and others - Page 1
Forum section: electronics / projects

author: justanothername
author_rank: Regular Contributor
timestamp: September 20, 2025, 05:37:08 pm
content: Hi.I hate to write PWL data for Spice so i hacked together a editor for this.You can find it here:https://github.com/dotmjsc/PWL_Editor[ Specified attachment is not available ]At least in microcap the pwl file can then be linked as stimulus for your simulation:

author: justanothername
author_rank: Regular Contributor
timestamp: September 22, 2025, 01:52:05 pm
content: Update in v1.4:Undo/Redo supportSelection from plot
PWM and overvoltage fault detection - Page 1
Forum section: electronics / projects

author: gaminn
author_rank: Frequent Contributor
timestamp: August 22, 2019, 01:24:49 pm
content: Hi,I created this schematic and I'm not sure if it does what I want. It is 74AHC123A dual monostable multivibrator. There are two inputs:1) LED_OVERVOLTAGE: high when there is overvoltage, low when the voltage is normal2) LED_PWM: 10 kHz PWM (that controls LED driver)There is one output, LED_FAULT. I want LED_FAULT go high when there is either LED_OVERVOLTAGE (immediately, without any delay, thus it is connected to reset input of the multivibrator) or when LED_PWM is stuck for several periods (this is set by R7/C5) in low or in high state.Will it work or can you help me modify it?
PWM channels in ATTiny25/45/85 - Page 1
Forum section: electronics / projects

author: JJalling
author_rank: Unknown
timestamp: August 19, 2013, 08:02:42 pm
content: Hi all,I can't figure out how many individual PWM channels (HW) the ATTiny25/45/85 has. In Atmels parametric search, the number is 4, but it seems like it's only 2 when i look in the datasheet .IMO, Microchips solution on showing the available peripherals and what pins to use in a table, is WAY better.:http://www.atmel.com/Images/Atmel-2586-AVR-8-bit-Microcontroller-ATtiny25-ATtiny45-ATtiny85_Datasheet.pdfBR Jonas

author: lapm
author_rank: Frequent Contributor
timestamp: August 19, 2013, 08:20:24 pm
content: Based on datasheet (Page 1.)QuoteNot sure how ever if you can use all 4 at same time. Haven't used Atmel parts that much myself.

author: madires
author_rank: Super Contributor
timestamp: August 19, 2013, 08:31:07 pm
content: Each timer has two output registers to control two output pins, i.e. one timer provides the clock for two output pins and the PWM ratio is defined by the dedicated output compare registers. Please read the sections for the timers very carefully, it will take some time to understand the concept. The nice thing is that all AVRs (Tiny and Mega) share the same concept with minor differences.

author: hans
author_rank: Super Contributor
timestamp: August 19, 2013, 08:44:06 pm
content: – 8-bit Timer/Counter with Prescaler andTwo PWM Channels– 8-bit High Speed Timer/Counter with Separate Prescaler•2 High Frequency PWM Outputswith Separate Output Compare Registers• Programmable Dead Time GeneratorSo 2 PWM channels are generated from timer 0, and 2 PWM channels from timer 1. You need both timers for 4 PWM outputs.However, because the device only has 8 pins, most functions are multiplexed. From pin table at page 2:PB5 contains no PWMPB4 contains OC1BPB3 contains OC1B InvertedPB2 contains no PWMPB1 contains OC0B or OC1APB0 contains OC0A or OC1A invertedSo you can only get 3 PWM outputs from this chip at one time. PB4, PB0, PB1.

author: JJalling
author_rank: Unknown
timestamp: August 20, 2013, 09:07:56 am
content: Thanks for sorting it out for me guys. I'll have to find another chip then.bR Jonas

author: Psi
author_rank: Super Contributor
timestamp: August 20, 2013, 10:35:23 am
content: I use the ATtiny44A quite often for random stuff.It's small, cheap and has all the general stuff... ADC, Serial (USI), 8bit timer, 16bit timer, analog comparator.Both of the timers have 2x output compare units for PWM (4 channels total).They're also on separate pins, so you can use them all at once.
pwm controller for a soldering iron - Page 1
Forum section: electronics / projects

author: m3vuv
author_rank: Super Contributor
timestamp: April 27, 2020, 11:23:57 am
content: Hi all,i would just like your views on this idea,Due to the lockdown stuck at home with hardly any of my lools,my solder station is with them!,in the meantime i have this iron but no controller :https://www.ebay.co.uk/itm/Soldering-station-iron-handle-24V-For-936-ESD-937-928-926-852-852D-R/153308326131?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649im using it from a homebrew psu,it works fine but as there is no control it gets way too hot!,would one of these work to aler the temp?:https://www.ebay.co.uk/itm/12V-24V-36V-Pulse-Width-PWM-DC-3A-Motor-Speed-Regulator-Controller-Switch-I2A7/184112843172?epid=1969130781&hash=item2addfb09a4:g:DFYAAOSw-a5eEIBzits just untill i can get my tools back.,cheers.m3vuv
PWM Fan Controller - how to get a stable frequency? - Page 1
Forum section: electronics / projects

author: Didix
author_rank: Regular Contributor
timestamp: May 01, 2015, 05:49:32 am
content: Intel's specification for 4-Wire Pulse Width Modulation (PWM) Controlled Fans asks for a 25kHz modulation:http://www.formfactors.org/developer/specs/4_Wire_PWM_Spec.pdfNidec proposes a NE555 based circuit:http://www.nidec.net/apps.htmThis circuit works for my fan - so far that's fine.However, the frequency strongly changes when changing the duty cycle (10kHz .. 20kHz).How could I do better to get a much more stable frequency when changing the duty cycle (by using a NE555)?-Didix

author: void_error
author_rank: Frequent Contributor
timestamp: May 01, 2015, 06:09:02 am
content: Move the 1k resistor from the output to the wiper of the 100k pot, that way any load at the 555's output won't affect the frequency that much. In other words, short the 1k resistor and put one 1k resistor between the 100k pot wiper and the TRIG-THRES node.

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 01, 2015, 06:28:23 am
content: The inverter in the fan motor won't mind a big swing in PWM frequency. In fact, after the input level converter, it most likely either goes into a low pass filter or a gated counter, with maybe a few Hz of control bandwidth.

author: Didix
author_rank: Regular Contributor
timestamp: May 01, 2015, 01:39:41 pm
content: Meanwhile I have replaced the capacitance to 300pF.To neglect the influence of the load I have removed it.This does not heavily change the fact, that the frequency covers that wide range (21..38kHz).I have also moved the 1k resistor as proposed to the wiper.This changes the effect when having the load connected a little (24..36).However, when the load ist unconnected I still see the same wide range (21..38).-Didix
PWM Fan Controller TACH questions - Page 1
Forum section: electronics / projects

author: Christopher
author_rank: Frequent Contributor
timestamp: January 27, 2016, 07:30:56 pm
content: I've been looking at designing a FAN controller which will vary the speed of an 80mm computer fan.This is fine, I can use a micro and a MOSFET to switch the return of the fan using a high-frequency PWM signal...Now my question is, I want to possibly look at the tach signal to make sure the fan is not stalled, unplugged or is going too slow and needs replacing.It is my understanding these pins are an open collector which is active low normally and is released when the rotors go past the hall sensor. Fine.Now surely when the Mosfet is off in my (crude) diagram, there is a current path thru. the tach pin to let some current flow through keeping the fan on?!Also, as a seperate Q, how are modern optos in terms of speed so I can isolate the fan from the control circuitry?

author: oPossum
author_rank: Super Contributor
timestamp: January 27, 2016, 09:43:49 pm
content: Much easier to use a 4 wire fan if you want PWM control and good quality tach signal.For a 3 wire fan the + supply should be adjusted with a linear circuit rather than PWM so the tach will work properly.
PWM fan - Page 1
Forum section: electronics / projects

author: pappkopp
author_rank: Contributor
timestamp: August 19, 2013, 01:12:01 pm
content: Hello!So here is the deal i have an HP Procure Switch (2810) and there is two pissnoisy 40mm fans. And i'm swapping them out with some 2x noctua 120mm.They are standard 3pin PWM but the problem is that the motherboard in the switch isn't powerful enough to power the fans.My plan is to power the fans with a external powersupply but again more problems, if there is no fans connected to the Switch there is a crazy warning light that flashes.Is there anyway to power the external fans and feed the pwm signal into the onboard headers of the switch? Or maybe make a dummy signal maker for the fans?Kind Regards

author: mariush
author_rank: Super Contributor
timestamp: August 19, 2013, 02:12:27 pm
content: Theres no such thing as standard 3 pin pwm.computer fan pinout is always : ground (black), voltage (red) , tachometer (white/yellow), pwm (green/blue)tachometer is signal from fan to the pc reporting speedpwm is signal from motherboard to fan to adjust its speed.the picture in your post is not correct from a wire color perspective.If your noctua fans have 4 wires, you could take out the 3rd wire (tach) and attach it to the connector for the 40mm fans and power the fans separately.But before you do that, you should check to see if the third wire is a classic tachometer or not - some 40mm fans don't report the rpm (rotations per minute) but rather just send a 5v signal or something similar when they're spinning, nothing when they're blocked. If that's the case, connecting the tachometer wire from a pc fan won't help. Get a multimeter and check between ground and that third wire to see what dc voltage you get there with the old fans. If it's a constant 5v or something similar, then it's not a standard pc fan style connection.If the thing still complains with the rpm wire connected, it may have some current sensing... in that case you could fake a fan using a basic resistor between ground and voltage of that connectorUse the classic formula V = I x R and fake a fan using 0.1A for example ... check the fan voltage ... 12v / 0.1 = 120 ohm power = 0.1x0.1x120 = 1.2w so a 3w resistor would do.
PWM Filter for fan input - Page 1
Forum section: electronics / projects

author: Jakethepython
author_rank: Newbie
timestamp: September 20, 2020, 04:31:05 pm
content: I have a small 12 VDC fan that i am running from a PWM out of PIC24 Micro. It is being switched through a MOSFET on the Low side. The problem is normally the system is running as 12VDC Some applications will require a 24VDC input. I have a voltage sense that will put my PWM to 50% creating an average voltage of 12 VDC. The 24 volt spikes are killing the fan though. what is the best way to go about smoothing the voltage out of the PWM to be DC voltage.

author: S. Petrukhin
author_rank: Super Contributor
timestamp: September 20, 2020, 11:51:25 pm
content: Quote from: Jakethepython on September 20, 2020, 04:31:05 pmPWM always has the same amplitude, equal to VCC but different filling, i.e. the time during which this voltage is connected to the load. To reduce this amplitude, you can use the LC filter as an integrator or LL / CC divider, calculating the reactance.

author: Jakethepython
author_rank: Newbie
timestamp: September 21, 2020, 01:53:49 am
content: You're English is fine. The only problem with an LC filter based on Frequency is that it will always chop the voltage so when i have a 12V amplitidue it will make it seem like a 6 volt. Unless I am doing something wrong.Thanks in advanceJake

author: S. Petrukhin
author_rank: Super Contributor
timestamp: September 21, 2020, 02:07:32 am
content: Quote from: Jakethepython on September 21, 2020, 01:53:49 amI made a little mistake-RC filter. Not every PWM can withstand the load on the LC. See how class D amplifiers generate output voltage. You can even use a TDA amplifier with a standard datasheet circuit to generate the desired DC voltage using PWM. And any step-down pulse converter.

author: David Hess
author_rank: Super Contributor
timestamp: September 21, 2020, 03:10:03 am
content: An LC filter will do what you want. Essentially PWM driving an LC filter is the output stage of a buck switching converter with an output voltage equal to the input voltage times the duty cycle.
PWM Generator IC Selection - Page 1
Forum section: electronics / projects

author: scootermcgoober
author_rank: Newbie
timestamp: November 09, 2012, 08:44:50 pm
content: So I've been using the PCA9685 for PWM generation for a while now (for driving LED strips); but I would like to add a circuit which can control triacs for dimming incandescent fixtures. Its my understanding that in order to dim the triac must be switched in sync with the zero-cross time of the AC. So I guess what I'm looking for is a multi channel PWM generator IC (which can be controlled over SPI or I2C) which supports synchronization via an input. The input would be a zero-cross detector off a low voltage transformer. This could easily be done with a microcontroller but I would prefer an off-the-shelf solution. Any thoughts? Currently I'm running this on a raspberryPi; I like the PCA9685 because its a set and forget operation; just set the duty cycle of the outputs and let it run.

author: penfold
author_rank: Frequent Contributor
timestamp: November 11, 2012, 05:36:04 pm
content: I have not personally come across any ICs that meet your needs, the latest phase angle controller I've come across used an 8-pin microcontroller.If you're not too afraid of analogue circuits (the most set and forget of them all) you could use an I2C/SPI DAC to control a 'voltage controlled dimmer' (<- a search term that should produce some of them)
PWM instead of DC voltage? - Page 1
Forum section: electronics / projects

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: February 19, 2015, 01:10:46 am
content: Hello,I was wondering if it would be possible to power electronics using a very high 90+ % duty cycle square wave as PWM instead of DC voltage.I know my flashlight has PWM modes to reduce brightness but can it be used as a DC power supply for example?

author: Whales
author_rank: Super Contributor
timestamp: February 19, 2015, 02:36:06 am
content: For dumb loads like LEDs and motors it's fine as long as your PWM frequency is high enough to not cause issues.If you want to make a voltage rail for ICs then it needs to be more stable (each pulse could reset the device). You can't just dump the PWM into a capacitor -- it'll charge up to full voltage but pull higher current during the "on" times to make up for the difference. There is probably a really nice solution to this I don't know of

author: rexxar
author_rank: Frequent Contributor
timestamp: February 19, 2015, 02:56:27 am
content: Quote from: Whales on February 19, 2015, 02:36:06 amYou could probably use the PWM as part of a SMPS, but by then the cost of the extra components is a lot more than just a simple linear regulator.Why exactly do you want to do this? Just to get a variable power supply? If you don't need more than 1A or so, just use an LM317, or any of the endless variety of adjustable linear regs.

author: cc83
author_rank: Contributor
timestamp: February 19, 2015, 05:43:07 am
content: you could try a low pass filter to smooth out the PWM, I have used that from a MCU to a opamp with good results before. There are some more complex filters but then it starts to get expensive.

author: Seppy
author_rank: Unknown
timestamp: February 20, 2015, 12:10:37 pm
content: Are you asking whether you can directly connect a PWM signal to a device multiply the supply voltage by the duty cycle %?While you can make the energy delivered from a PWM equal to the energy delivered from a DC voltage often this isn't possible.This is just related reading stuff, don't worry about it if your not interested in the theory:If you would like to use it as a DC power supply, you could do the normal ladder network style LC filters there:http://en.wikipedia.org/wiki/Electronic_filter_topologyA buck convertor uses an LC circuit for just this purpose and many buck convertors infact use PWM controllers:Buck Convertor WIKIhttp://en.wikipedia.org/wiki/Buck_converterExample PWM BUCKhttp://www.ti.com/lit/ds/symlink/tps5110.pdfIf you simply want to use a PWM output as a DAC none of what I have said above is really necessary:Connect a simple RC low pass filter (go for a highish value of R, let the micro max current output dictate this value) to the output and level shift + amplify with an Op-Amp. This may or may not be acceptable in your application.Many times 100% duty cycle is acceptable, I'm guessing your worried about power dissipation. The power dissipated is very heavily determined by the load and the supply voltage for the PWM waveform.What kind of load are you planning to connect a PWM waveform to?
PWM Investigation - Effective Voltage & RMS - Page 1
Forum section: electronics / projects

author: Noah
author_rank: Newbie
timestamp: November 22, 2013, 10:45:30 am
content: Hello guys!I'm interested in PWM stuff and I have a simple question: How do I calculate the effective voltage of a PWM and how can I measure it?I tried different measuring methods: A PWM at 50Hz, 20% and Vpp = 2V. The true RMS Fluke multimeter shows the same AC voltage with a Offset 0V and a Offset of -1V. But this can't be true because the most 'part' of the period is at -1V...? The Agilent Oscillospoe measures also different values...I there a formula to calculate this or does anyone have experience in PWM effective voltage?

author: mjrandle
author_rank: Contributor
timestamp: November 22, 2013, 10:09:12 pm
content: Yes there is, Google "rms square wave duty cycle".Regards,Mike

author: w2aew
author_rank: Super Contributor
timestamp: November 22, 2013, 10:52:59 pm
content: You may want to view my video on the topic of RMS voltage. The first part of the video talks about what RMS means and shows some examples of calculating RMS for sinewaves. Then I talk about square waves (that are balanced around ground), and then I talk about digital pulses, like PWM pulses which have their "low" value equal to ground, and some high value equal to Vp. The video shows that the RMS value of a PWM signal such as this is Vp * sqrt(duty_cycle). The discussion of PWM waveforms begins at about 6:45 in the video.

author: The Electrician
author_rank: Frequent Contributor
timestamp: November 23, 2013, 06:32:47 pm
content: Quote from: Noah on November 22, 2013, 10:45:30 amWhat is the model number of your Fluke? If you get the same value for offset and no offset, you probably haven't set your Fluke to measure "True RMS AC+DC"See post #39 of this thread:https://www.eevblog.com/forum/chat/how-can-i-test-if-a-dmm-is-reading-in-true-rms/msg167774/#msg167774Also see:https://www.eevblog.com/forum/testgear/testing-dmms-rms-measuring-capability/msg171733/#msg171733
PWM mosfet driver die - Page 1
Forum section: electronics / projects

author: lostsoul
author_rank: Newbie
timestamp: May 11, 2020, 10:13:37 pm
content: Hi everyone,since some time i am fighting with this driver, i need to control a blower (hvac), it is brushed motor, inrush current bit lower than 18 amps, pwm from PIC running at 20 kHz. I've try with some chineses H Bridge (using only half), single mosfet, parallel mosfet, always fries after few minutes. I have a basic osciloscope ( hantek measure DC only?)in the pictures, yellow line is source PWM (after driver IR4427) and green on the motor (measure mosfet drain, inverted probe), this driver was the last, with H bridge there were clean flat signal on motor.PIC uses soft start (low duty cycle and increase slowly until desired duty)what am i failing ?Thanks

author: Picuino
author_rank: Super Contributor
timestamp: May 11, 2020, 11:19:27 pm
content: How is the wiring?Cables should be short and avoid large loops

author: WattsThat
author_rank: Frequent Contributor
timestamp: May 12, 2020, 01:38:12 am
content: The yellow trace is the gate drive? It appears to be 5 volts peak to peak if I’m reading the display correctly. If so, that’s probably the issue as the IRF3205 requires 10 volts on the gate to fully form the channel.

author: lostsoul
author_rank: Newbie
timestamp: May 12, 2020, 09:37:46 am
content: Quote from: Picuino on May 11, 2020, 11:19:27 pmCable to circuit has around 1m, and driver to the motor around 30cmQuote from: Picuino on May 11, 2020, 11:19:27 pmYellow is signal coming from PIC to both inputs os gate driver (IR4427), green probe connected to low side of motor

author: Picuino
author_rank: Super Contributor
timestamp: May 12, 2020, 01:13:21 pm
content: The green line shows two strange behaviors.The top of the signal shows an oscillation of about 50kHz and should be flat. So I said there must be stray inductances in the cables (they are a bit long)At the bottom you can see a small step as if the mosfet did not switch completely well until the end of the cycle.One reason I can think of for those mosfets to burn out is that the switching can be very fast and a short circuit occurs while the recovery time of the diodes. But those diodes are quite fast and the Mosfets very robust.Another reason may be spurious switching voltages caused by stray inductances in the cables. The cable from the mosfets to the diodes should be as short as possible (few millimeters). Or else add a Snubber network to the mosfet.
PWM period control with rotary encoder - What does a user expect? - Page 1
Forum section: electronics / projects

author: 741
author_rank: Frequent Contributor
timestamp: August 19, 2019, 03:28:31 pm
content: I've written code to support altering PIC161x PWM period (and duty) via a rotary encoder.For the duty it seems clear the user does indeed want to adjust dutytime, so encoder movement maps simply to duty change. For the period, I am uncertain what seems natural.As I tried adjusting PWM period, I found I actually expected control of frequency, but only to get to a ball-park value. After that, and with the 'scope timebase set appropriately, I then required good control of period.Because f = 1/t, it takes ages to wind frequency down to minimum, but going from half to full frequency is very fast.Perhaps slow turns imply period-centric control, fast turns imply frequency-centric control?

author: rhodges
author_rank: Frequent Contributor
timestamp: August 19, 2019, 03:59:01 pm
content: I am currently working on a PWM project for controlling a small motor and pump. I am using a combination display and keypad, but I can easily pretend I am turning a knob.I just picked 10khz and it looks pretty good on the scope. For my project. But as you imply (I think), it might be useful to change the PWM frequency to find what is ideal. And then, control the duty cycle. Maybe even going back and forth repeatedly.So I would like to see a display that I can switch between duty cycle and PWM frequency. The button on the rotary encoder would be an obvious way to switch back and forth. The display would show maybe "F" and "P" (assuming a simple 7-segment module) to indicate frequency or PWM duty. Yes, it should be obvious that a 3-digit number (0% to 100%) is duty cycle and a 5-digit number is a frequency... But why not?
PWM TO DC LC filter inductor considerations? saturation vs rating - Page 1
Forum section: electronics / projects

author: SArepairman
author_rank: Frequent Contributor
timestamp: January 22, 2014, 01:21:28 am
content: So I would like to do a relatively high voltage high current LC filter connected to a IGBT.Inductors are pretty mysterious to me, it looks like I need 2 inductors in the 0.3mH range to make a 3rd order LC filter. to filter ~10KHz switching frequency PWMed to DC.I wanted these supplies to put out like up to ~4 amps @ rectified mains voltage (~170v)When I look at digikey I see current rating and current saturation, should both of these values be chosen to be greater then four amps?http://www.digikey.com/product-detail/en/AIRD-03-331K/535-11337-ND/2660627Will this work? Do I need to consider core material in my application? Are there any traps for young players here?

author: Harvs
author_rank: Super Contributor
timestamp: January 22, 2014, 01:46:55 am
content: In a round about manner it sounds like you're building a Buck converter. Would that be the case?Tt would be worth also considering mosfets, 170V isn't actually that high, and most commercial PSUs at twice that voltage are still using mosfets. What's the input voltage?Sizing up parts for a buck converter is pretty straight forward given a set of requirements, and there's plenty of app notes out there (and many many books).But to answer your questions about inductor ratings. The current rating is the DC current at which the device will reach max operating temperature given a specific ambient temp (e.g. usually 25c) due to the copper resistance. The Saturation current is the peak current where the core material moves out of the relatively linear region on the BH curve. In short, your RMS current can not be higher than the current rating (in fact you need to de-rate that for ambient temp and add margin,) and the peak current should be kept well below the saturation current.

author: SArepairman
author_rank: Frequent Contributor
timestamp: January 22, 2014, 01:51:13 am
content: Quote from: Harvs on January 22, 2014, 01:46:55 amYea I guess I am just designing a ghetto buck converter with no real feedback that can do up to rectified mains voltage, the idea is to have it run off mains with no transformer or anything. I am using a IGBT because I have IGBT and driver handy. This fits my design goal perfectly, I have no need for anything more advanced.

author: johansen
author_rank: Super Contributor
timestamp: January 22, 2014, 04:47:03 am
content: you need more like 5 mH, for 20% current ripple.plug your own numbers in here:http://www.daycounter.com/Calculators/Switching-Converter-Calculator.phtml
PWM to Reverse bias Fairy Lights  - Page 1
Forum section: electronics / projects

author: 24602
author_rank: Contributor
timestamp: February 05, 2021, 12:18:01 am
content: Hey AllBeen thinking of this one randomly over a year or so. Trying to come up with a LED (strip) dimmer to fairy light circuit.These fairy lights have two "circuits" by the means of reverse biasing half of the LEDs and driven +-30V switching one set or the other. I have attached oscilloscope shots of what's coming out of the existing power supply.Any idea how to convert 2x PWM signals to the fairy lights, First thoughts would be a H bridge but when using two PWM inputs there would need to be something so they don't try and turn on at the same time.Any ideas would be appreciated

author: langwadt
author_rank: Super Contributor
timestamp: February 05, 2021, 12:33:56 am
content: what's the problem with them turning on at the same time?

author: 24602
author_rank: Contributor
timestamp: February 05, 2021, 12:51:07 am
content: Quote from: langwadt on February 05, 2021, 12:33:56 amWouldn't that be shorting the power rails out internally of the H Bridge?

author: langwadt
author_rank: Super Contributor
timestamp: February 05, 2021, 12:56:41 am
content: Quote from: 24602 on February 05, 2021, 12:51:07 amif you turn on both top and bottom transistor on one side of the bridge it shorts the supply

author: penfold
author_rank: Frequent Contributor
timestamp: February 05, 2021, 02:17:54 am
content: If you have complete control over the PWM generation.. then you can use one leg of the H bridge to select "polarity" and toggle it alternately high/low per cycle and use the other leg to do the "timed pwm"If your PWM signals are synchronised on the rising edge, use one to drive the clock input of a d-type flipflop to generate alternating Q/(not)Q signals which are used to enable tristate buffers on the actual PWM signals, with the output of the tri-states jointed together, it'll alternately select one of the PWMs and the Q or (not)Q from the flipflop can do the polarity select. It limits you to 50% duty cycle on either polarity if you're using fixed frequency, but you could do something clever with allowing for a variable frequency to give more "contrast"