hybridfree/eevblog-posts huggingface dataset:
PWM circuit - calculating capacity and resistance - Page 1
Forum section: electronics / beginners

author: Drake122
author_rank: Contributor
timestamp: February 21, 2018, 10:40:17 am
content: Hey guys!I was trying to make a PWM circuit, but don't really know how to calcaulate the discharge cap and the pot to use to be able to maximize its "bandwith". This test circuit I made in EveryCircuit only regulates the amps between 27.9 and 30. How can I make as close to 0 and 30 as it can get?

author: danadak
author_rank: Super Contributor
timestamp: February 21, 2018, 12:02:49 pm
content: Some questions -1) What is the bandwidth of the oscilloscope you are using ?2) You mention amps, what does total circuit schematic look like ?3) You referred to BW, normally a PWM is low pass filtered into DC. If you needit I have an ap note on calculating filter values which control ripple and settlingtime in the DC output.Another approach -http://www.instructables.com/id/Yet-Another-Simple-Pot-controlled-555-PWM-generato/Regards, Dana.

author: Drake122
author_rank: Contributor
timestamp: February 21, 2018, 02:15:05 pm
content: Thanks, but its just a testI'm trying to learn electronics, so for now, I just want to make that circuit, which I made in EveryCircuit work. Posted a screenshot. I'm not able to lower the amps on that lamp.
PWM control  - Page 1
Forum section: electronics / beginners

author: Jane
author_rank: Frequent Contributor
timestamp: July 18, 2023, 11:10:46 am
content: Does anyone know where I can find a list of laptops that does not use PWM to regulate the brightness of LCD and LED displays?I find one athttps://laptopmedia.com/top-laptop-p...t-on-eyesight/but it seems to be rather outdated.Thank you for help

author: Jwillis
author_rank: Super Contributor
timestamp: July 19, 2023, 01:44:03 am
content: I think what your looking for is DC dimming or commonly know as "Flicker Free". This has been used for some time over PWM.Have you looked at this ?https://www.notebookcheck.net/PWM-Ranking-Notebooks-Smartphones-and-Tablets-with-PWM.163979.0.html

author: Faranight
author_rank: Unknown
timestamp: July 19, 2023, 09:05:02 am
content: Ooh, yeah! I've grown a habit to manually dim the backlight of laptops on display in a store to see, if the screen flickers or not.Good to see I'm not the only one bothered by this shitty design and my eyes are suffering from the flicker.The other culprits being the automotive industry as a lot of car dashboards and some red backlights do the flickering.Thus, driving at night on a dark, but high-traffic road is a pain for me.
PWM Controller  - Page 1
Forum section: electronics / beginners

author: RiccardoR
author_rank: Newbie
timestamp: April 23, 2017, 08:41:24 am
content: Hi everyoneI'm new to building circuits and this siteI was looking for some help with my circuitI am currently get a square wave out of both 555 timers , and the motor also runs.My only issue I seem to be struggling with is that my variable resistor isn't working as it's doesn't want to vary the speed of the motorAny help would be greatThank you !

author: jb79
author_rank: Contributor
timestamp: April 26, 2017, 02:32:16 pm
content: Hi!A PWM control for a motor can be done with one NE555 only. For example, you could use this:http://www.555-timer-circuits.com/pwm-controller.htmlU1 should have a pullup on the trigger-input to be sure that the level is high enough if the output of U2 can't deliver the necessary current in high state. Otherwise that might cause problems.The values of the resistors and capacitors in the schematic should be ok, could you check if you insert the correkt one on the correct position in the circuit?You said you checked the waveforms, so you have an oszi available? If there is no error with the circuit you should see a different lengh of the pulses at U1 output when turning the poti.

author: rstofer
author_rank: Super Contributor
timestamp: April 26, 2017, 05:39:59 pm
content: U2 pin 3 (out) should have a free running square wave output. According to one of the online calculators, this should be about 7.8 kHz.U1 pin 3 (out) should have an adjustable width pulse, still at 7.8 kHz with a pulse width of 55 us (if I used the calculator correctly) at midpoint (5k). At 10k the width would be 110 us.http://www.ohmslawcalculator.com/555-astable-calculatorhttps://www.allaboutcircuits.com/tools/555-timer-monostable-circuit/

author: Zero999
author_rank: Super Contributor
timestamp: April 26, 2017, 06:14:59 pm
content: Alternative, just use the LM393, with one half configured as an astable and the other as a comparator. The duty cycle can easily be varied from 0% to 100%.
PWM Converted Into 4-20ma (Vs) 1-5V Converted into 4-20ma - Page 1
Forum section: electronics / beginners

author: ArduinoWannaBe
author_rank: Newbie
timestamp: January 28, 2014, 08:20:02 am
content: Hello Everyone,Background:I recently purchased a cheap relay board off of amazon, and the spec which I should have checked prior says it works off of 15ma-20ma signals. (Because a relay is ON-OFF) This doesn’t seem to make a lot of sense to me. Wouldn't be much easier to just make the board 0-5V or PWM much less work to switch a relay on or off that way I would think.Anyways back to my real question. According to Ohms Law V=IR so a 250 Ohm resister minus the resistance in the circuit (Could be hard to measure the resistance in the circuit). That should give me my 4-20MA out, because this is just on/off I think this should work with a couple of resister sizes.Secondly, I have seen people turning PWM into 4-20ma with a small R-C- Filter and then connecting to a Voltage-to-Current Converter like XTR110 which should work.What is the correct way to do this?This is just a demo setup so I think a crappy relay to save the wait time on component shipping is the way to go. When I build my final product I will not use 4-20 Output to a relay board.Am I missing an easier solution?CheersArduinoWannaBe

author: ivaylo
author_rank: Frequent Contributor
timestamp: January 28, 2014, 08:44:24 am
content: A schematic of what you are trying to do would help, but I can't even tell if you understand what "4-20mA" means (and if your final product is not going to use why even mention it here)...

author: Rerouter
author_rank: Super Contributor
timestamp: January 28, 2014, 09:00:43 am
content: 4-20mA is an industry standard signal, the purpose of that relay would be something like a high alarm (a sensor reading over ~75%)as for driving it, if you have access to both ends, or even just the bottom end, then a single op amp current sink (look at daves dummy load) will fit the bill, even using that 250 ohm resistor as the measuring resistor if you want to keep the 1-5V signal logicJust please search this site a bit, there are 20 odd threads showing the small tweaks that had to be done to make them stable (Dave oversimplified the schematic) which also include working component combinations,

author: ArduinoWannaBe
author_rank: Newbie
timestamp: February 02, 2014, 05:27:03 am
content: Thanks Rerouter!I will read the artical. Just looking for the best practice to make my prototype work well for testing.CheersArduinoWannaBe
PWM current impact on power supplies - Page 1
Forum section: electronics / beginners

author: Rigolon
author_rank: Regular Contributor
timestamp: September 21, 2018, 07:09:18 pm
content: Hello everyone,I'm having some doubts on some details of how a PWM signal works. I understand some of the basic knowledge, e.g. a component that is capable to withstand a maximum forward current of 100mA is able to withstand 1A if the signal has a small duty cycle.What I am confused is about:* This is applied for every component?* If the maximum current rate is 100mA, I could use any current as long the Irms = 100mA? For example use a 1A with 10% D.C. ou 2A with 5% D.C.?* Is there a frequency limit where this 10% D.C. of 1A draws more than 100mA, or it doesn't matter the frequency it will always draw 100mA? (In this supposition the components immediately rise and fall with the signal, it does not have rising or falling time)* And the most important thing, if I use a 10% D.C. signal at 1A, do I have to use a 1A power supply or does a 100mA could be use?

author: oPossum
author_rank: Super Contributor
timestamp: September 21, 2018, 07:42:03 pm
content: In switching power supplies using MOSFETs the current will typically be well below the continuous rating to ensure it stays out of the saturation region.Infrared LEDs can usually handle substantial pulse currents. Up to 1A for a 5mm package is not unusual.You have to carefully read the spec sheet for a specific part to know what it can do.

author: P_Doped
author_rank: Contributor
timestamp: September 21, 2018, 08:14:07 pm
content: Components which are often subjected to pulsed currents will have a separate pulsed current rating.This current is not as simple as your PWM fractional scaling, unfortunately.The limiting factors can include internal element heating, electromigration, and other physical phenomena.But, the good news is that the pulsed current will (should?) be higher.As Raven said, check component datasheets.I did 1 quick check on an n-channel MOSFET and it was rated for 10A continuous and 26A pulsed (pulse width limited by thermal temperature ratings)...
PWM frequency versus clock speed - Page 1
Forum section: electronics / beginners

author: Simon
author_rank: Unknown
timestamp: January 12, 2010, 08:22:49 pm
content: what sort of relationship is there between the clock speed and the maximum PWM frequency of a pic ? (12F615 / 16F88 in my case) and not only the maximum PWM frequenct but resolution and frequency versus clock speed ?

author: jahonen
author_rank: Super Contributor
timestamp: January 12, 2010, 08:53:37 pm
content: The PIC timer counts Fosc/4 rate (or lower with prescaler), so with 4 MHz clock, the timer clock frequency is 1 MHz.PWM frequency is same than timer rollover-rate, which in turn is timer clock/(counts per rollover), so if you have 1 MHz timer clock and timer has 256 counts (8 bits resolution), the PWM frequency will be ~3.9 kHz.Regards,Janne

author: Simon
author_rank: Unknown
timestamp: January 12, 2010, 09:24:46 pm
content: aha right I though it was something like that I just didn't realise that there was the 4X prescaler, so if I was going to sacrifice resolution say make it 7 bits I could run at a frequency of 7.2 KHz ? (given the 4 MHz clock and /4 prescaler)

author: jahonen
author_rank: Super Contributor
timestamp: January 12, 2010, 09:30:20 pm
content: 4 MHz was only an example. 16F88 runs up to 20 MHz, so maximum timer clock is 5 MHz. That gives you 19.5 kHz PWM frequency @ 8 bits resolution.Regards,Janne

author: Simon
author_rank: Unknown
timestamp: January 12, 2010, 09:57:28 pm
content: Yes I see, what I'm saying is can I sacrifice resolution for frequency ? if it comes down to counts can I say a clock speed of 4 MHz 1 MHz counter 3.9 KHz frequency @ 8 bits, or 7.2 KHz @ 7 bits ?

author: jahonen
author_rank: Super Contributor
timestamp: January 13, 2010, 03:52:59 pm
content: Certainly you can make trade-offs between resolution and frequency. PIC16F88datasheettable 9-3 @ page 87 lists some combinations @ 20 MHz. Resolution does not need to be integer number of bits, for example setting PR2 to 99 yields resolution of log2(99) ~= 6.64 bits.Regards,Janne
PWM-ing a MOSFET for control of capacitor charge rate? - Page 1
Forum section: electronics / beginners

author: HwAoRrDk
author_rank: Super Contributor
timestamp: June 21, 2017, 08:33:07 pm
content: Hi all. I was thinking again some more about what I was trying to accomplish in what was described in a previous post of mine (thread here) - using an analog mux to switch between various fixed resistors in order to alter the timing of an RC circuit. It occurred to me that, fundamentally, all I really need to accomplish is to control the current flow going into the capacitor.So, the idea I came up with today was simply PWM-ing a MOSFET on/off at a variable duty cycle in order to control the current flow. It seems so simple, it's almost stupid! I don't know why it didn't occur to me before.The circuit I came up with is as follows:I have an N- & P-channel pair to switch the current, with the 0-5V square wave to be generated by microcontroller. Lowering the duty cycle should lengthen the charge time, and vice-versa. A 100% duty cycle should leave the P-channel FET on, giving me my 'zero' setting that I talked about before.I simulated the circuit, and it seems to work fine and do what I want. It also appears to handle the negative voltage (caused by the other side of the cap changing polarity when the 'home' switch is tripped) without issue. But I can't help feeling that there's some "trap for young players" that I'm missing, and that there may be other considerations to be taken into account.My concerns:- The simulator shows that both 'FETs spend a fair amount of time in linear mode (in fact, the N-channel seems to spend all its time like that). I gather that MOSFETs produce more heat when in linear mode. Will this be a problem? Or is it relative to current flow? We're only talking a couple of mA at most here for either of them.- Will I be reducing the lifespan of the capacitor with this circuit? It is my understanding that excessive ripple current causes capacitors to heat up. Does that apply here? I don't want to prematurely degrade this particular part as I'm trying to not do any modifications or have any adverse effect on the existing componentry.
PWM, mosfet and strange electronic load behavior - Page 1
Forum section: electronics / beginners

author: Peter_O
author_rank: Frequent Contributor
timestamp: January 16, 2021, 06:34:41 pm
content: I'm driving a low cost IR540 mosfet module with an Arduino PWM output, set to 128 of 255, which is some kind of 500 Hz sqare signal.A 100 Ohm wire resistor as load gives the expected results.(12V DC for load circuit)CH1 (yellow) is the PWM outputCH2 (purple) is the voltage loss over the Mosfet, so the upper level is switched off, lower level is switched onExchanging the 100 Ohm resistor with an Array 3710A DC load, configured as 100 Ohm Resistance, gives this result:Switch off of the load happens to be a slow linear descent.This behavior is the same for different mosfets and with a function generator replacing the Arduino.The switch off slope tends to normal when increasing the load or decreasing the PWM Frequency.Is a DC load so "DC" that it can only be used in strictly DC setups?What is happening here?What is my mistake if any? What could I improve?

author: ledtester
author_rank: Super Contributor
timestamp: January 16, 2021, 11:11:14 pm
content: Keysight has an excellent white paper entitled "Electronic Load Fundementals":https://www.keysight.com/us/en/assets/7018-06481/white-papers/5992-3625.pdfJust supply an email address to download it.It shows the configuration of the control circuit used in the various modes -- constant current, voltage, resistance, power.On page 8 about CR mode it states:QuoteWhat they may be hinting at is that CR mode is not well-suited for a rapidly changing supply such as you are presenting to it.Another concern I have is the arrangement of your circuit. Is this how things are set up?Code:Vsupply --- Array --- IRF540 --- GNDI think it's meant to be used like this:Code:Vsupply --- ... --- Array --- GNDOn page 9 of the Keysight white paper is this schematic of a DC load in CR mode:If the IRF540 is below the Array you'll be severing the load's connection to ground at the purple mark. But that ground connection serves as a reference for all of the voltages used by the controlling op-amp and if it is allowed to float I wouldn't be surprised to see unexpected behavior.

author: Peter_O
author_rank: Frequent Contributor
timestamp: January 17, 2021, 09:32:52 am
content: Thank you for the extensive answer and taking the time to write it!As a newbie it's difficult to judge symptons right and your answer sheds a lot of light and helps me on.The keysight paper is a valuable hint and will be today's sunday reading.Your "ground" argument is striking. These little Arduino world mosfet modules all seem to be kind of similar.Here are the schematics of the module used in the example above:Great forum. Thanks again, ledtester!
PWM Noise/whine while on motor; why human ear hear them - Page 1
Forum section: electronics / beginners

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: April 13, 2016, 05:14:05 am
content: When I drive motor with PWM from MCU I heard a whine sound. Several people suggest to increase the PWM freq above audible range of human i.e 20Khz.But one thing I dont understand human ear heard sound when there is compression/rarefaction around local region.But PWM freq let say at 5Khz is electrical freq. It is not making any compression/rarefaction nearby. Then why this noise & how do human ear heard these?Edit: Then if I rum MCU core at 10Khz low freq then it should also make noise? But when I do it, it dont make any noise

author: ataradov
author_rank: Super Contributor
timestamp: April 13, 2016, 05:47:57 am
content: Quote from: Vindhyachal.takniki on April 13, 2016, 05:14:05 amWhen you feed frequency to a speaker it is also electrical. The speaker is designed to convert most of it into the sound. The motor is designed to convert most of it into a torque. But most is not all.In case of a motor you are energizing a winding and it is attracted to a permanent magnet. This is what makes the sound.

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: April 13, 2016, 06:01:57 am
content: Also magnetostriction?

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: April 13, 2016, 12:13:40 pm
content: thanks

author: BobsURuncle
author_rank: Regular Contributor
timestamp: April 14, 2016, 04:49:06 pm
content: Is the noise coming from the motor or PWM. Capacitors can whine due to piezo electric effect, especially MLCCs.

author: Audioguru
author_rank: Super Contributor
timestamp: April 15, 2016, 01:42:00 pm
content: The brushless DC motors on my electric radio controlled model airplanes twitch and play a little song to tell me they are booted up and ready to go. They whine at about 4kHz (the PWM frequency) when running.

author: rstofer
author_rank: Super Contributor
timestamp: April 15, 2016, 02:30:33 pm
content: Increasing the frequency also increases the percentage of time the driving devices (MOSFETs?) spend in the transition region (switching). This increases heating. With a production MOSFET driver, the transition region can be quite narrow. They are capable of dumping AMPS into the gate. Many times hobby circuits can't dump that much gate current and the transition region is a good deal wider. Driving a MOSFET directly from a uC is about as bad as it gets in terms of switching time and heating.
PWM of a High Torque DC Motor - Will I damage it? - Page 1
Forum section: electronics / beginners

author: K1JOS
author_rank: Regular Contributor
timestamp: October 29, 2014, 04:41:03 am
content: I have an antenna rotor that with a 12vdc supply will draw about 7-8 amps to rotate a load of up to 30 kilo's (65 pounds). It makes a single 360 revolution very fast in just several seconds. I would like to slow it down and was thinking to use something like PWM. The motor is controlled by a microprocessor (PIC) based regulated supply that uses a few MOSFETs for the solid state relays. I would like to use the existing controller but it has some limitations. There are only 3 buttons on the user interface to the controller for ON (Clockwise), ON (Counter-clockwise) or OFF. However, the user interface also has a PIC which sends a constant stream of datapackets serially to the motor controller. Commands for ON (CW), OFF or ON(CCW) are in one of three specific data packets. These data packets are about 5 msecs in duration (fixed at 9600 baud) but each packet is sent repeatedly in a stream every 250msecs. So the fastest cycle of an ON-OFF-ON sequence would take about 3/4 second. I want to slow down the motor by 50% but I don't want to damage it as it has no mechanical brake. ANy suggestions how to best implement this ?

author: johansen
author_rank: Super Contributor
timestamp: October 29, 2014, 06:28:39 am
content: Seems to me you can program software pwm to slow the motor down--or hardware, using a (God forbid) 555 timer as an oscillator of fixed duty cycle.Pwm frequency can be anything from 1khz to 20khz is practical.solid state relays are usually pretty slow but 1khz pwm should be achievableseems to me it would be very useful to vary the speed, can you rewrite all the code?

author: bigsky
author_rank: Regular Contributor
timestamp: October 29, 2014, 09:35:54 am
content: One thing to note is that PWM can cause motors to overheat - the motor is getting full voltage but isn't turning as fast so its back EMF is lower and the current is higher. Also any cooling fan on it won't be turning as fast. But I doubt an antenna rotator will be running for long enough for this to be an issue.

author: bktemp
author_rank: Super Contributor
timestamp: October 29, 2014, 12:26:35 pm
content: If the motor has some interference-suppression capacitor build in, this small capacitor often overheats if driven by pwm.

author: K1JOS
author_rank: Regular Contributor
timestamp: October 29, 2014, 01:34:34 pm
content: Quote from: johansen on October 29, 2014, 06:28:39 amThe motor controller PIC is proprietary so I cannot re-write the code but I can control the ON and OFF impulses sent to the controller. However these can only be sent every 250msec so the fastest ON-OFF cycle would be about few cycles per second... does not seem like much to gain. Not ideal, but I was thinking to try sending sequences of 2 ON packets followed by 1 OFF packet - i dont know how much inertia there will be in the motor mechanism but it may be enough to slow it down at least 30%? My only other option may be to redesign it from scratch - maybe a nice Winter project...
PWM or change resistors for a "led blinky" project. - Page 1
Forum section: electronics / beginners

author: hamster_nz
author_rank: Super Contributor
timestamp: October 10, 2018, 11:32:14 pm
content: I'm working on a battery-powered LED blinky trinket, controlled by an ESP32 module and a 150mAhr LIPO - the runtime needs only be a couple of hours at most, while a conference talk is in progress.It is just 10 LEDs that need independent blinking, each LED will be on it's own I/O pin. I have no plans of using the WiFi or BlueTooth at the moment. The hardware will be given away, so the new owner can run MicroPython on it. Because of this changing of module isn't really in scope.This is most likely a trivial question, but is there any merit (in regard to battery life) in increasing the LED's current limiting resistor, allowing the PWM duty cycle to be increased for the same brightness?I am pretty sure that it will make little (if any) difference in battery life if I run an LED at 2.5mA @ 50% duty cycle, vs 5mA @ 25% duty cycle... but wondering if anybody has actually done the legwork?The only merit I can see would be if no PWM was needed, so the ESP32's processor could be put to sleep, saving 40 or 50mA. Must read the docs - maybe there is a slow clock or partial sleep mode that would still allow for PWM.I'll be building 5 blinkies, so I there is any merit I will be able to test the theory by loading different ones with different resistors & firmware and actually testing.

author: gcewing
author_rank: Regular Contributor
timestamp: October 11, 2018, 10:37:55 am
content: From what I've heard, in theory the LEDs should be slightly more efficient if you run them near their maximum rated current and use pulse width to control the brightness, but it won't be a big difference. Like you say, you might gain more by being able to shut down the processor if the pattern isn't changing.
PWM or Constant Current for LED - Page 1
Forum section: electronics / beginners

author: BSYS
author_rank: Newbie
timestamp: February 18, 2022, 07:37:05 pm
content: Hello Everyone,I am trying to drive a high power LED.The Max DC Forward current is 1500mA, and the peak pulse current is 5000mA.However this is to much for my application, and i am looking to drive it at 100 or 200mA.I already have a constant current driver that works fine at 200mA, but i am wondering if a PWM solution pulsing a 1500mA current into the LED would be more suitable ?I am also worried about color shifting, is driving the LED at such low current compared to it's max rating affecting the emitted wavelenght ?Is PWM better at keeping the indicated wavelenght in the datasheet ?Thank you everyone for your help

author: tooki
author_rank: Super Contributor
timestamp: February 18, 2022, 07:47:06 pm
content: PWM is better for color accuracy and efficiency; constant current is less likely to flicker. (But if you do high speed PWM, like the ~25kHz PWM I did for some lighting at home, flicker is entirely eliminated and audio frequency switching is avoided.)
PWM pure sine inverter filtering question. - Page 1
Forum section: electronics / beginners

author: firewalker
author_rank: Super Contributor
timestamp: August 09, 2013, 02:04:24 pm
content: I am designing a demo for a really simple PWM (32 kHz) pure sine inverter. It produces a clean 50 Hz 230 Volts sine wave.In order to achieve the clean sine I had to add some extra capacitance (C1,C2,C3,C4). I had in front of some 100 nF/250 volts polyester caps and used those.Is there a proper way to calculate the values for the caps (or any other filter) and the R4 resistors? It is transformer depended?

author: Marco
author_rank: Super Contributor
timestamp: August 09, 2013, 02:16:44 pm
content: You are using the magnetizing and leakage inductance of the transformer to form part of the filter, so yeah it's transformer dependent ... also load dependent.As for R3/C4 ... are they really necessary?

author: ResR
author_rank: Regular Contributor
timestamp: August 09, 2013, 03:00:02 pm
content: R3 is probably 10 ohm 2 watt resistor for protection. It can be left out. C3 is parallel with a battery, no need for a big capacitor unless the cables are extremely long between battery and circuit. C1 and C2 depends on the transformer. I can't find R4 on the schematic.

author: firewalker
author_rank: Super Contributor
timestamp: August 09, 2013, 05:53:06 pm
content: Thanks you guys. R4 was a typo it should be R3.Alexander.
PWM signal causing RF interference.  - Page 1
Forum section: electronics / beginners

author: torch
author_rank: Frequent Contributor
timestamp: May 23, 2014, 05:10:52 pm
content: I have an irritating buzz when tuned to an AM station, particularly a weak station. It came with the car and survived replacing both the radio itself, the antenna and the antenna lead. A PO already installed a capacitor and inductor on the power supply wire. The buzz affects AM only, does not vary with engine speed and disappears if the antenna is unplugged. It is not apparent with the key set to ACC, but is definitely there Key On Engine Off.Pulling fuses, one by one revealed the buzz is related to the Variable Effort Steering. Looking at the Factory Service Manual, I think it's probably generated by the PWM output controlling the steering pressure. The FSM indicates the PWM frequency is 60Hz.I'm thinking a ferrite bead will not be effective at that frequency, so perhaps a small capacitor between the VES output and ground might attenuate the RF signal. Of course, if it's too big, it might damp the PWM signal too much and affect the steering. So my question is: how would you approach this problem?

author: AG6QR
author_rank: Frequent Contributor
timestamp: May 23, 2014, 05:21:31 pm
content: The PWM is 60 Hz? or 60 kHz?Regardless, what you need to get rid is the portion of the signal that interferes with broadcast radio, which will be in the range of roughly 540-1700 kHz. A ferrite bead may not do much at the fundamental frequency (especially if it's 60Hz), but it still could help attenuate those troublesome harmonics. I think that might be the easiest and least disruptive thing to try as a start.

author: torch
author_rank: Frequent Contributor
timestamp: May 23, 2014, 09:14:15 pm
content: Quote from: AG6QR on May 23, 2014, 05:21:31 pmNo, it's definitely in the FSM as "Hz" not "kHz". I thought it might be a misprint, but elsewhere in the fault diagnosis it talks about injecting a 30 Hz signal with a signal generator and slowly increasing to 60 Hz. So the manual is self-consistent. That said, it's raining outside so I haven't dragged out a scope to check it myself.

author: Mosaic
author_rank: Regular Contributor
timestamp: May 23, 2014, 10:28:08 pm
content: There's a solenoid valve run by that 60Hz signal that is causing the harmonic into the AM band. You need to snub the coil on that solenoid as close to it as u can as the interference is propagating into the wiring harness.

author: torch
author_rank: Frequent Contributor
timestamp: May 24, 2014, 02:28:41 am
content: Reading the FSM again, I realized that the 60 Hz is not the output frequency, just a test frequency. Since there was a break in the rain, I crawled up under the dash, moved the fuse box out of the way and back-probed the output with a VOM frequency counter. The output is actually 251 Hz.Oddly enough, when I was done, the buzz was gone. There must be a loose connection somewhere but no amount of wiggling wires will bring it back.I hate intermittent faults.
PWM Signal Generator in reverse polarity mode - Page 1
Forum section: electronics / beginners

author: VanillaIceCream
author_rank: Contributor
timestamp: July 11, 2021, 10:35:35 am
content: Can I switch the output ports of this PWM motor driver module to get out a negative PWM signal for my motor without destroying anything in the module?I found no info about it on the sellers page.PWM Module:https://www.amazon.com/dp/B07XR9B1RN/ref=cm_cr_arp_d_product_top?ie=UTF8&language=en_US

author: Benta
author_rank: Super Contributor
timestamp: July 11, 2021, 06:21:03 pm
content: I've no idea what you mean.0...100% can be reversed to 100...0% PWM for a "negative pulse" PWM, if that's what you need.

author: jpanhalt
author_rank: Super Contributor
timestamp: July 11, 2021, 06:51:45 pm
content: In addition, it may depend on whether the motor case/frame is "ground." In other words, motor ground and your PWM source share a ground.

author: ledtester
author_rank: Super Contributor
timestamp: July 11, 2021, 06:56:27 pm
content: Do you mean you want to create a PWM signal between 0 and -5V instead of between 0 and 5V?Then you might try this which doesn't require a negative rail:https://electronics.stackexchange.com/a/221425/95488The output won't be able to provide a lot of current, but into a high impedance input it should work.

author: VanillaIceCream
author_rank: Contributor
timestamp: July 15, 2021, 03:59:15 pm
content: Quote from: ledtester on July 11, 2021, 06:56:27 pmYes exactly, thanks.
PWM signal on MCU with I/O pin - Page 1
Forum section: electronics / beginners

author: Aswinth
author_rank: Newbie
timestamp: March 28, 2020, 10:35:13 am
content: Hi I am trying to control a servo motor with a microcontroller. I recently learned about servo motors and that we need something called PWM (Pulse Width Modulation) signal to control it. So I started reading about PWM signals and found this articlehttps://circuitdigest.com/tutorial/what-is-pwm-pulse-width-modulation.As you can see they or almost everywhere they only tell what PWM is and how it looks and works. No one tells how to generate it. At the end of the link they tell we can do it with microcontroller like Arduino, PIC, STM etc but i do not want to use the in-built funtion.The reason is I am collaborating on this project with my Prof. and he is using all the PWM pins to control mosfet so i have to use only the GPIO pin.

author: Ian.M
author_rank: Super Contributor
timestamp: March 28, 2020, 11:25:45 am
content: A Futaba compatible RC servo signal is *NOT* normal PWM. Seehttps://en.wikipedia.org/wiki/Servo_controlYou need to generate a repeating train of pulses with exact on time (ON=logic '1'). The off time beteen pulses is non-critical, so long as you stay within the minimum and maximum pulse rate limits for the servo you are using. Generally, nearly all servos intended for RC applications will accept a 50Hz pulse rate (20ms frame) +/-10%, and its usual for modern servos to accept significantly faster pulse rates to decrease response lag.The on time directly commands the servo position. 1.5ms is so-called 'neutral' usually mid-travel, and the range 1ms to 2ms typically gives about 90 deg of rotation though the scaling factor is not well standardised. The pulse widths required to reach the mechanical limits are even less well defined, and it should be noted that many cheaper servos can be damaged by persistently trying to drive them into their mechanical limits.Depending on the servo, as little as 5us of pulsewidth jitter can produce a noticable half degree twitch of the output shaft, so generating a servo pulse purely in software is not practical on any MCU that is servicing other interrupts. Also, at maximum pulse width, the timing loop that generates it will take up over 10% of your CPU time. Therefore as a minimum for a practical implementation, you need an interrupt-capable hardware timer for the pulse width, (and preferably also for the repetition rate), and a core architecture that permits a low and predictable interrupt latency so the ISR servicing the timer interrupt and generating the output pulse on an I/O piun doesn't add significant jitter. If your application has other interrupts, they must either be disabled during the whole of the pulse on time, or the MCU must have interrupt priority levels with the servo timer interrupt at the highest (active) priority level.
PWM speed control frequency of modern 4 wire computer fans? - Page 1
Forum section: electronics / beginners

author: e100
author_rank: Frequent Contributor
timestamp: January 09, 2021, 04:56:08 pm
content: The original spechttps://wiki.kobol.io/helios4/files/fan/4_Wire_PWM_Spec.pdffrom 2003 says the PWM speed control carrier has to be between 21 and 28kHz.Do modern fans with their onboard driver circuitry still need such a high frequency?If they are more tolerant of lower frequencies, how low can you go?

author: Benta
author_rank: Super Contributor
timestamp: January 09, 2021, 07:37:32 pm
content: If you're talking fans for PC enclosures or other computer cooling, it's 25 kHz nominal (21...28). For interchangeability purposes, I'd expect all such fans to adhere to this specification.If you want to operate outside this spec, it's on your own risk.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: January 11, 2021, 09:59:00 am
content: Those fans are (usually) very simplistic devices.They started with two wires, and in the fan there was just a HALL sensor and a transistor, and even those could run on whatever frequency you put in them.Then came the need for some speed feedback, and for that a third wire was added to break out the signal from the HALL sensor.This had a little problem though, because there was no speed feedback during the "off" time of the PWM cycle.So a 4th wire was added, so the HALL sensor always has power and can give back speed information.But the fan itself is still very simple, not much more then a permanent magnet, an electromagnet a HALL sensor and a transistor as a power switch.Unless of course you have some kind of fancy fan. They may have built in temperature controllers, LED lighting an all bets are of.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 11, 2021, 10:08:05 am
content: Doctorandus_P described the situation as it was some 15 years ago.Now, for about a decade, almost all fans have more control than that, including stall detection, auto-retry, some have better modulation for the transistors.Out-of-spec PWM may still work, though. Or may not.

author: SVFeingold
author_rank: Frequent Contributor
timestamp: January 11, 2021, 11:31:04 am
content: Quote from: Siwastaja on January 11, 2021, 10:08:05 amNot to mention that basically all "DC" fans are brushless and include the requisite driver. Even the cheapest $1 fans on Digikey.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 12, 2021, 09:11:00 am
content: I thought that was obvious to everyone.But the early BLDC fans worked like Doctorandus_P described, basically just the hall sensors controlling the transistors directly. That of course counts as a "driver".Modern drivers are a bit more complex because why not, they use ICs anyway so extra features come basically for free.
Pwm to analoge - Page 1
Forum section: electronics / beginners

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: February 26, 2013, 11:38:48 am
content: Hello im working on a project at school an i need to interface my arduino with a high power speed controlerThe speed controlers that i have are controled by a potentiometer to control te motors speed, my arduino gives out a pwm signal at 5v and the speed controler works off of 24-36vI was thinking of a digitalpot but im unsure if this will work or not as i seam to remember them only working to the control voltage. How could i go around doing this as i dont want to go te route my teacher sugested(servo motor attached to a pot to turn it)

author: psycho0815
author_rank: Regular Contributor
timestamp: February 26, 2013, 12:21:13 pm
content: to answer that one would need more info about the speed controller. Preferably schematics. What does the Poti actually do? Does it act as a voltagedevider or as a current limiter? in the first case you could use the pwn and a lowpassfilter to generate a voltage and possibly an opamp to amplify it to the required level. In the second case, you might be able to use a mosfet as a variable resistor, but without more information on the motordriver that's mostly speculation.

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: February 26, 2013, 04:46:09 pm
content: the speed controller uses a twist grip to control the speed which has a pot as a potential divider inside. unfortunately i do not have a schematic for iti do however have one that is less powerful than the one i am using which i also do not have the schematic for.the only information that i have is that the voltage coming from one of the pins for the potentiometer is 24v for the motor that i will be using. and the arduino is 5V for the pwm.

author: AndreasF
author_rank: Frequent Contributor
timestamp: February 26, 2013, 07:32:42 pm
content: Quote from: carbon dude oxide on February 26, 2013, 04:46:09 pmHave you actually measured this voltage (the 24V)? If not, that would be the first thing you should probably do.
PWM to DC control voltage? - Page 1
Forum section: electronics / beginners

author: dentaku
author_rank: Frequent Contributor
timestamp: June 15, 2013, 02:00:58 am
content: I'm wondering if there's a simple basic way to take a PWM signal and convert the pulse length (I'm assuming that's what you call it) to DC voltages?In other words, as I modulate the pulse width, the output of the circuit would be a DC voltage to goes up and down depending on the pulse length of the input.This would be useful for creating crude Control Voltage messages from an audio signal coming from a soft-synth.

author: Psi
author_rank: Super Contributor
timestamp: June 15, 2013, 02:18:28 am
content: Yes, this is very common and sometimes called a PWM DAC.The simpliest way is to put the i/o pin PWM signal through a lowpass filter (resistor and cap to ground)egA good starting point might be using a 100Hz low pass filter and a pwm frequency at maybe 4khz.The higher your low pass filter frequency is the faster your dc signal will respond to pwm changes.HoweverThe closer your low pass filter frequency gets to your PWM frequency to more ripple you will get on the DC output.

author: Jebnor
author_rank: Regular Contributor
timestamp: June 15, 2013, 04:57:51 am
content: A simple RC lowpass circuit as Psi suggests will work. A 2 or 3 stage could work too. That just means that you put 2 or 3 or more low pass RC filters back to back.Although quite a read, there a couple people have a great discussion about this topic in this post about a precision power supplyhttps://www.eevblog.com/forum/projects/general-purpose-power-supply-design-7488/. The PWM & filter discussion starts about page 5 or 6. (Yes there are 23 pages)

author: dentaku
author_rank: Frequent Contributor
timestamp: June 26, 2013, 02:48:58 am
content: I finally took the time to experiment with this tonight and I got some interesting results. I can filter out most of the highs with a simple low pass filter and get a smooth change in voltage while modulating the Pulsewidth of a software synth with an LFO but if I change the values of the resistor by using a pot instead I can get some fun harsh sounding stuff happening too. I'm using this to modulate the frequency of a 555 multivibrator through pin 5.It's like a modular synth built from salvaged parts
PWM - Page 1
Forum section: electronics / beginners

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: December 07, 2012, 02:21:12 am
content: I want to control a 1ST PC CORP. AFC1212DE-PWM but not sure how? Are there any simply pwm that can handle 12v and 3 amps or is there a better way? I could apply full power but don't want it to take off and be loud as hell ... Could I just use lower voltage with a 4 wire pwm fan???

author: Psi
author_rank: Super Contributor
timestamp: December 07, 2012, 03:23:41 am
content: If you power a PC fan from the 5V supply instead of the 12V supply they are much quieter but still move a reasonable amount of air.

author: T4P
author_rank: Super Contributor
timestamp: December 07, 2012, 05:42:54 pm
content: Is it a 4 wire fan? If it is just clock PWM without a cap in between from a 555 PWM circuit on the PWM pin, problem solved i guessIt's usually connected to the switching mosfet/transistor in the fan (I doubt they would use a transistor on the AFC but surely i have a few FFBs lying around)
PWMing a LED driver. Is it a bad idea? - Page 1
Forum section: electronics / beginners

author: fubar.gr
author_rank: Unknown
timestamp: January 03, 2016, 12:36:14 am
content: I have ordered a LED light that according to specs can work with DC voltages from 9 to 33 Volts. This makes me suspect that there's a proper driver enclosed and not simply some current limiting resistors.The light is sealed and I won't have access to its internals. Can I dim it by simply PWMing the power supply voltage? Or is this going to mess up the driver circuit?

author: fubar.gr
author_rank: Unknown
timestamp: January 03, 2016, 02:15:18 pm
content: Quote from: blueskull on January 03, 2016, 12:48:50 amThanks.
PWS-2K04A-1R Breakout Board - Page 1
Forum section: electronics / beginners

author: Underscore
author_rank: Newbie
timestamp: November 04, 2023, 04:51:13 am
content: Hello!Though I did do a quick search beforehand, I'm not quite sure if this has been asked here before.Does anyone have any sources on how to make a power supply breakout board, particularly with Supermicro's PWS-2K04A-1R? I don't currently own the product myself, but if anyone knows any way to convert the power supply's goldfingers to multiple PCIe connectors, it would be greatly appreciated.Here are some images if it will be of any help:a)https://i.ebayimg.com/images/g/fRoAAOSwQxZk2ou2/s-l1600.jpgb)https://i.ebayimg.com/images/g/ji8AAOSwOQFka9kz/s-l1600.jpgc)https://i.ebayimg.com/images/g/FOEAAOSw~QBkkdGv/s-l1600.jpg(sending the images normally took too much space on the post)Thank you in advance.

author: eleguy
author_rank: Regular Contributor
timestamp: November 04, 2023, 07:54:40 am
content: Could you concern soldering the cables directly on to the board? In addition - as some likely this unit could act as the "normal" atx psu - you may have to short corresponding "PS_ON" pad to ground. Otherwise it could be that it does not fully start and just gives some short of low current stand up (usually 5V) power. Follow the traces and/or use multimeter and you will figure out. Pinouts of the 6/8 cables can be found from the net.

author: j1772_EVSE
author_rank: Newbie
timestamp: November 11, 2023, 09:18:55 pm
content: I've been looking at this power supply so I could use a Level 2 EVSE to charge my RV's batteries.I've come across these links about how to make it work....https://www.robotics.net/hacking-supermico-12v-power-supply/https://www.reddit.com/r/AskElectronics/comments/3hedav/help_current_sharing_12v_server_psus_for_desktop/Let me know what you figure out.
PXX time in datasheets - Page 1
Forum section: electronics / beginners

author: kirill578
author_rank: Newbie
timestamp: March 03, 2012, 12:46:01 pm
content: Hey, There is some sort of time constant in datasheets between pulses like P5A or P15, I've attached an image of it.What does it mean and how do I convert it to seconds.(I could not find any expiation of it in the datasheet itself).here is the datasheet:http://ww1.microchip.com/downloads/en/DeviceDoc/39622L.pdf

author: Psi
author_rank: Super Contributor
timestamp: March 03, 2012, 01:27:13 pm
content: Bottom of the datasheet, page 42 and 43.It lists all the Pxx values in 2 tables and shows their timing requirements.P5A has to be more than 40ns
Pythan based GUI for embedded testing - Page 1
Forum section: electronics / beginners

author: rakeshm55
author_rank: Regular Contributor
timestamp: September 16, 2017, 01:00:41 pm
content: Hi,I am new to Python..I have an embedded board for which i need a host GUI to1. Test the board2. Program firmware etc.I have used tkinter library for developing simple GUI ...Which will be asuitable library for the same...with good documentation

author: Jeroen3
author_rank: Super Contributor
timestamp: September 16, 2017, 01:10:54 pm
content: LookupPyQT.
Python error; 'NoneType' object has no attribute 'after' - Page 1
Forum section: electronics / beginners

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: July 11, 2015, 04:57:49 pm
content: I got error while coding in python.Need to print same random value again & again.Code:from Tkinter import *import Tkinterfrom random import randintclass App1(Tkinter.Tk):def __init__(self, master):Tkinter.Tk.__init__(self,master)self.master = masterself.label = Label(self , text = "Voltage" , font = ("Helvetica",32))self.label.grid(row = 0)self.reading_label = Label(self,text = '0.0' , font = ("Helvetica",110))self.reading_label.grid(row = 1)self.update_reading()def update_reading(self):value = randint(0,9)reading_str = "{:.2f}".format(value)self.reading_label.configure(text = reading_str)self.master.after(1 , self.update_reading)root = App1(None)root.title("Option")root.geometry("320x240")root.mainloop()I gor error message:Traceback (most recent call last):File "/voltmeter.py", line 26, in <module>root = App1(None)File "/voltmeter.py", line 16, in __init__self.update_reading()File "/voltmeter.py", line 23, in update_readingself.master.after(1 , self.update_reading)AttributeError: 'NoneType' object has no attribute 'after'

author: IanB
author_rank: Super Contributor
timestamp: July 11, 2015, 06:25:00 pm
content: Quote from: Vindhyachal.takniki on July 11, 2015, 04:57:49 pmPresumably you have narrowed it down this far?I don't know enough about what you are doing to say why 'after' is not defined. Where is 'master' defined?

author: c4757p
author_rank: Super Contributor
timestamp: July 11, 2015, 07:16:26 pm
content: Have you even tried to follow through your code?Code:root = App1(None) # here None is "master"class App1(Tkinter.Tk):def __init__(self, master): # you passed in None for master hereself.master = master # so now self.master is None...self.update_reading()def update_reading(self):...self.master.after(1 , self.update_reading) # self.master is still None here...AttributeError: 'NoneType' object has no attribute 'after'"'NoneType' object" (None) indeed has no attribute 'after'. You can't say None.after()... You might want to try passing in something other than None...

author: bson
author_rank: Unknown
timestamp: July 11, 2015, 07:27:38 pm
content: tk=Tkinter.Tk()root=App1(tk)See:http://zetcode.com/gui/tkinter/introduction/BTW, as a convention, 'root' refers to the root window, which is your display background. It's what's (conceptually) returned by Tk(). Your app is a child of this, and it would make sense to call it something other than 'root'. Also, as the examples on the link above show it's generally referred to as an application's parent window, so calling it "parent" is the most straightforward (compared to "master").