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What is PWM? Pulse Width Modulation tutorial!
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- Опубліковано 14 лис 2008
- I cover the basics of PWM and show you how to cheaply build a PWM circuit that can dim LEDs, control the speed of a motor, or control the power going to pretty much anything you want!
Circuit diagram: afrotechmods.co...
Check out my webpage for more easy videos about electronics! www.afrotechmod...
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You sir make the best electronics tutorials on the internet! Don't ever stop!
Very nice and clear presentation. Thank you very much. One good presentation is much more efficient for a beginner than reading 10 pages of silly text, and gives appetite for further helpful reading if needed.
Trust me I have been reading about PWM. For quite a bit for now. Nothing is as perfect as this video. The content the narration just perfect.
Why can't all tutorials be like this? Expanding slightly on the circuit construction would be the only added benefit here I can see. Kudos +Afrotechmods
Such simple straightforward explanation! So easy to brush up long forgotten knowledge! Thank you!!!
@blacklust007 Excellent question. The LM317 is a linear voltage regulator which is inherently inefficient. It burns up excess voltage as heat to get the output voltage you want. Power loss will be (Vin - Vout) * Iout. PWM is switching between fully off and fully on, so it will be much more efficient and generate less heat.
I built a PWM circuit using your diagram to control current flowing through a non-inductive piece of nichrome wire. Works like a charm. I picked a TIP141 NPN Power Transistor. Before using the 555 I tested it with a function generator and discovered the optimal switching frequency for PWM was about 1khz (close to what you have). In the datasheet TIP141 lists switch on time as 0.9μs and switch off as 11μs. I figured that by adding the values I'd get a full cycle of 11.9μs and a bandwidth cap of 84Khz, yet when cranking up the function generator, I found the real bottleneck to be closer to 8Khz. Pass that TIP141 wasn't able to keep up.
Am I calculating the full cycle wrong is the discrepancy caused by the fact my test conditions (load and base-emitter voltage) being different from those in the TIP141 datasheet?
@nonodalloo The main thing that will determine the current limit is the transistor you use. You should try find a low resistance N channel MOSFET, put a heatsink on it, and get a schottky diode rated for 5A to put in antiparallel with the motor.
When you noticed that this video was uploaded about 10 years ago 😂😂 but is more useful than the new ones around
@jwhill15 Sure. Use a separate power supply for the 555, (roughly 10V will do) and then 24V will go on the high side of the motor. Make sure the grounds are all connected.
thank you, i have a new knowledge after 10 year you upload this video on youtube
I tried this with a TLC555 and nope doesn't work! I kept trying and couldn't get it. So finally I ordered an NE555 and sure enough! it went from 0.2% to 99.9%! Lol, I guess you weren't kidding when you said it won't work will an TLC555. I'am gonna use this on my DIY electric go kart. Thanks Afrotechmods!
Thank you!!! The difference between using a voltage regulator or potentiometer and a pulse width modulator really cleared a lot of things.
It's awesome. I heard PWM many time but after watching this video I know that fully.
Thanks a lot.
You set new standards in clear communications. Stunningly good video. Thank you friend.
The PWM output goes though an inductor to a capacitor to filter the waveform into DC. Usually there is a Zener diode to clamp the voltage, but the efficiency is still really good at 80 - 90 percent. Look up the LT3505 chip for a typical example.
Yup. There's also loads of prebuilt motor controller solutions out there. Just search for motor speed controller. Also, check out Robot Marketplace.
@spelunkerd If you energize a coil like in a motor, what happens is, you establish a magnetic field across it. When the power pulse goes away, the field collapses back across the windings, inducing a voltage back across the coil. Depending the value of that coil, it can be a fairly high voltage. That voltage can destroy your transistor or FET so the diode blocks such voltage and sends it back to the coil to be dissipated instead of across your transistor. This effect is called "back EMF".
BEST VID EVER really i think it should be featured just because it is so awesomely professional
Awesome video. I already knew a fair amount about PWM and controlling it, but I needed something simple (ie a 555 circuit) for a single direction, single motor project, and this will work perfectly. Thanks much!
ok, this make's more logic to me. I am fighting with a pwm circuit now for 2 months, and all burned out. So now i will try this circuit, it looks more solid to me.
@spelunkerd Also what the diode does is help eliminate what are called eddy currents. Eddy currents flow any direction within a magnetic medium. These fields will collide with and interupt the fields that the control source feeds into it. At these areas of colision, heat is generated, and sometimes, lots of heat. Designers of motors and transformers design spacific shapes and other things into the magnetic medium, to eliminate eddy currents, thus reducing heat buildup.
You are the god of electronics , I simply am so attracted to the way you teach, that I would like to be your disciple for life. Thanks for the video that is to the point.
Hey, very good explanation and good images..
one can with good benefits replace the NPN Bipolar Transistor that you show on the image with a mosfet..
some of the main benefits are.
Eliminate the input resistor (known as a base resistor on a BJT)
Allowed faster switching speeds.
Lower on resistance
In most cases cheaper
Lower risk of thermal runaway (due to the thermal behaviour of a Mosfet)
Note that it is not possible to have a 0 to 100% duty cycle with only a 555.
@tjnlsn255 Both ways will work. But I would use the LM317 method because a stable voltage over time will mean the frequency and duty cycle won't drift as the batteries discharge.
Talk about short and sweet. This helped. Great video. Thanks for the upload.
OMG THIS IS MUCH MUCH EASY TO UNDERSTAND :)))))
compare to my lecturer who yelled at us :" GO BACK TO PRIMARY SCHOOL IF U DONT UNDERSTAND WHAT I'M TALKING!!"
:D
Goodness when you said "from Radioshack" I was like " Wait...how old is this?" and then I looked at the date, "Oh."
@Landotter1 What you will need to add is a biasing resistor to the drain of each of the FETs or the emitter of the bipolar transistors. This resistor should be roughly .1 - .5 ohm 5 - 10 Watts. Radio Trash used to sell them but I don't know, these days. Any hifi repair shop will stock them too. Any blown up power amp will have them. In the hifi world, they are called "emitter resistors"
hey...thanks for the video......very rarely do i find such a well explained video on youtube....cheers!
Change C1 to a lower value to raise the frequency. I'm not sure what the lower bound of the cap value is though. Any frequency above 20Khz or so will be inaudible. If you were using this circuit to control a motor, you could set the switching speed to something like 25Khz and you wouldn't hear a "switching whine."
Simplified, professionally done explanation. Thank you sir.
thank you. it was so comprehensive and fast!(Which is a good thing!)
where can I learn more and deeper about this topic?
Wow!! Great.....this is like a way to make the people to get understand. Thank you....
Huh! I haven't seen that 555 astable multivibrator configuration before. Definitely gonna write that down.
Your demo and voice are magnificent, thank you for interpretation.
Thank you so much. Very easy to understand what the PWM is!
Desde Guadalajara, Jal. MEXICO, Lo probé en el simulador PROTEUS y todo bien gracias.
@Afrotechmods nice job educating people . Keep it up!!
Never mind turns out it does work I got a big n-channel MOSFET that can handle about 5 to 12 amps with a small fan and heatsink to control the speed of a homemade trolling motor
wow, thats great! i understand a lot more if your were the instructor of our technical school. thanks Sir!
Working on one right now!
Thank you for the wonderful video about PWM. Could you please explain to me what's the purpose of the 10nF caps on the 555 timer pins 2 and 5? Thanks!
Thank You for the very good explanation of PWM.
There is another Circuit that I found that uses a Pulsed Signal at 9 to 12 volts Via the 555 Timer to Technically increase the MCD (MilliCandela) on the LED. It pulses it in such a way so it cant overheat the LED Which allows more Current Going to it.
in your video you have the 555 timer and the led's being powered by the same 12v source. When you Modulated that into a lower voltage signel wouldn't that also lower the voltage feeding the 555 timer.
much better explanation than my lecturer
Succinct, descriptive, excellent.
you should definitely write a book with electronic experiences and link it to your videos on youtube to understand electronic concepts.
thank you. cool stuff. it was of particular utility for you to mention that it works up to ~15v. that pre-empted my question concerning whether this would be safe to use with an SLA such as in a car, where it could be up to13.6v or so.
Awesome vid. Thanks for sharing your valuable time and knowledge.
@Aviator14 I think the advantage of this is that with the rheostat, you're generating heat because the extra voltage goes through a resistor, instead of not being used at all like in the PWM circuit. Someone correct me if I'm wrong :)
Wow I just learned something lol. That actually made a lot of sense. I have a question, do lift switch dimmers use PWM too? Is this why CFL bulbs tend to flicker? If so, would using multiple step down transformers (though impractical) to lower the voltage make a CFL bulb dimmer without flicker?
it is too good and very helpful for me.
@Afrotechmods So technically, there is no limit to the amount of Voltage & Current one can PWM with the 555 timer IC, as long as your electronic components are electrically capable on the high side of the motor? Then in that case you would switch it "on" & "off" (like your transistor video) or using an IGBT (Insulated-Gate Bipolar Transistors) [Which btw, some can even go as high as a rated current of 1,200A & a maximum voltage of 3,300V] or a relay for heavier loads. :)
Thanks for the video. I love the circuit diagram !
Great video fellow VAIO user. Thanks for the tutorial.
What if I want to have a pulse with 1.5T? Would I need capacitors or how would the circuit change?
How about doing a part 2 vid on basics on feedback so when heavy loads are applied, the duty cycle will increase to a set value and change back to low load value and no baby sitting. Think a 556 timer will do that right? I forgot...
Can you describe how the frequency of the PWM effects the load and how I should choose what freq I want to use ? or suggest another article ?
Awesome video!!! I have been searching the web to see if I can get an answer to this question:
If I connect 120v AC mains through a transformer with a 1:1 wind ratio, then through a full wave rectifier, can I PWM the resulting voltage to control the speed of a 1200 watt, 10 amp DC motor? The PWM logic will be created using my Raspberry Pi and an NPN transistor to flip a Solid State Relay rated for the proper voltage and current of the motor. It's my understanding that the rectified voltage will still oscillate up and down, but I am planning on sticking a 250v 1000uF capacitor in parallel with the voltage coming off the rectifier, as well as a flywheel diode across the motor leads. Will that PWM signal be enough to create a moderately smooth motor speed?
I am using python on the Raspberry Pi to change the frequency and duty cycle of the logic. I have a program to increase/decrease motor speed from user input on the Pi.
Anyhow, I hope this isn't too involved of a question for the comment section.
I love your videos, so many of them have helped me. Thanks so much Afrotechmods!
Sounds like you are attempting to regulate the speed of a 90VDC/18amp treadmill motor. Not an easy task.
Very concise and informative. Thank you!
short durantion and very helpful... awesome.
So if you can control the speed of a motor using pwm, how would you control the direction the motor is rotating? Would I need to use an h-bridge for that
yes h bridge is used to change direction of motor bcoz it changes polarity very very fast
this circuit works well with TIP120 at 4.5 volts, as you said
very nice! now you should make a video on how to generate pwm through software :)
It's a quite old electronics video when it mentions Radioshack
This was a fantastically informational. Thank you
I like this video, well done and explained.
Nice, clear and concise. Thanks
Thank god for your videos and thank UA-cam for 0.75 speed.
The potentiometer will heat up even at slight loads. On the other hand, by heating, it consumes power = not efficient.
Thank u for explaining in detailed manner
Can this circuit be used as a trigger circuit? Say connect the output to a DC-DC solid state relay to get a variable duty cycle output of the relay? I am trying to get a variable 15 volt trigger voltage to operate an air solenoid on and off fast.
short ,clear understandable thank you .
SO AFROMAN, this combined with a mosfet or op amp or some amplifier can get me a much higher power PWM wave, hopefully if it has a high enough switching frequency. Now since you're talking about this switching power supplies, what happens if I put an inductor and a diode? Then feed that output into the input, so it can keep it correct. So I can make a switching power supply with ARDUINO??????
Obrigado pela partilha, meu amor. Foste muito querido. E o video é muito informativo e explica de uma forma simples e eficaz. Gostei. Amo-te.
Fantastic tutorial! very clearly explained, but a few questions; how many led's could you control using this PWM? (Im looking at controlling a large array of leds) Also, could this pwm control a 12v motor without any troubles?
It´s good, but Can you put the circuit diagram or another link to watch it please?
Really thank you. Just I got a trouble With the resistence bulbs, we see an annoying flicker.
nice video thanks for the upload. Could you do a video on AC PWM for a motor?
the radioshack near me closed :(
I get all my stuff on either amazon or direct from China if it is bulk components.
This might sound like a dumb question, but if I put a capacitor in series with the output pin line, would i get a straight DC voltage based on the duty cycle (For example, If I feed a 5V PWM signal with a 50% duty cycle, would I get a straight 2.5v DC supply with a capacitor?)
Dear Sir, If you don't mind, I want to ask something... Why need PWM? Why I can't use just only a Potentiometer ? to increase or decrease the voltage?
Perfect explanation. Thank you!
As custom you videos are very helpfull. Thanks a lot.
Bwahha Ghetto hardware fun. Think I found a favorite channel.
Thanks for sharing it with us!
Thank you, Afroman! That explains a lot!
Cheers!
Good but what if I need to control a 20v bolt motor
I know I can use a MOSFET to handle the roughly 3amp current draw, but wil this circut work with a 20v load
Great tutorial, thanks for posting it!
Thanks for the video. Do you know how we could change the shape of the pulse waveforms, especially in pemf device circuit?
Thanks for the great video. I have seen PWM commonly used for electric actuator motors they get 24V AC common and 0-10 dc analog input so how analog input changes the speed of the motor that is already using 24 V AC current what kind of control they use? Thanks in advance
The 50K pot changes the duty cycle but which component determines the frequency of the signal and how to change it? Please give some details,thank you
Why not just use a potentiometer to adjust voltage? What is the benefit of making a squarewave and adjusting the PWM?
Great videos.I learned a lot from them
it ther any app or website that can calculate the capacitors, resistors and potentiometre values for the frequencies you're looking for ?
amazing explanation
i love your video style!
very fruitfull tutorial.Thanks