What is PWM? Pulse Width Modulation tutorial!

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...

[@Afrotechmods]

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[@bizzlemedia]

You sir make the best electronics tutorials on the internet! Don't ever stop!

[@fahmylina123]

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.

[@SohamSinha]

Such simple straightforward explanation! So easy to brush up long forgotten knowledge! Thank you!!!

[@aadarshshetty]

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.

[@TravisCrowder]

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

[@Afrotechmods]

@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.

[@Afrotechmods]

@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.

[@enilenis]

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?

[@Zarif3]

Thank you!!! The difference between using a voltage regulator or potentiometer and a pulse width modulator really cleared a lot of things.

[@frankcastle4814]

When you noticed that this video was uploaded about 10 years ago 😂😂 but is more useful than the new ones around

[@shahzadm8461]

I'm getting started on electronics and find this one of the best channels on the subject. Also good humor and excellent voice talent.

[@ducbui1833]

thank you, i have a new knowledge after 10 year you upload this video on youtube

[@robertcreed8962]

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!

[@tobyhallam4750]

You set new standards in clear communications. Stunningly good video. Thank you friend.

[@Afrotechmods]

@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.

[@AltRage]

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.

[@piyushpv]

It's awesome. I heard PWM many time but after watching this video I know that fully. Thanks a lot.

[@steffankaizer]

BEST VID EVER really i think it should be featured just because it is so awesomely professional

[@Dosbomber]

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!

[@Landotter1]

@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".

[@sponkii]

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.

[@Landotter1]

@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.

[@G-Code_official]

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.

[@Afrotechmods]

Yup. There's also loads of prebuilt motor controller solutions out there. Just search for motor speed controller. Also, check out Robot Marketplace.

[@claudiaftprivacy6478]

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.

[@Landotter1]

@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"

[@tushargt88]

hey...thanks for the video......very rarely do i find such a well explained video on youtube....cheers!

[@ashwath123456]

Talk about short and sweet. This helped. Great video. Thanks for the upload.

[@Afrotechmods]

@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.

[@haladappajm3601]

Wow!! Great.....this is like a way to make the people to get understand. Thank you....

[@TheGuyOnThePE]

thank you. it was so comprehensive and fast!(Which is a good thing!) where can I learn more and deeper about this topic?

[@bboyzhauchia]

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

[@omaanko]

Thank you so much. Very easy to understand what the PWM is!

[@FRRRRAAANNK]

Simplified, professionally done explanation. Thank you sir.

[@AMHASSAAN]

Your demo and voice are magnificent, thank you for interpretation.

[@cameraman1234567890]

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

[@jarrettdoesstuff2318]

Huh! I haven't seen that 555 astable multivibrator configuration before. Definitely gonna write that down.

[@emiltech2]

wow, thats great! i understand a lot more if your were the instructor of our technical school. thanks Sir!

[@ciudadanoalerta3673]

Desde Guadalajara, Jal. MEXICO, Lo probé en el simulador PROTEUS y todo bien gracias.

[@wilrecar77]

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."

[@seannot-telling9806]

Thank You for the very good explanation of PWM.

[@SporkSchivago]

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!

[@JordanEdmundsEECS]

Succinct, descriptive, excellent.

[@waotop]

it is too good and very helpful for me.

[@jorgewashington2981]

Awesome vid. Thanks for sharing your valuable time and knowledge.

[@iamabhi223]

short durantion and very helpful... awesome.

[@sudhanvagokhale9908]

@Afrotechmods nice job educating people . Keep it up!!

[@photoleif]

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.

[@Afrotechmods]

Working on one right now!

[@cameraman1234567890]

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.

[@averagemale2000]

I like this video, well done and explained.

[@antegas]

As custom you videos are very helpfull. Thanks a lot.

[@johnshelley2919]

Thanks for the video. I love the circuit diagram !

[@MrZeus7]

@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 :)

[@sy_ox]

@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. :)

[@pitabreado]

Very concise and informative. Thank you!

[@fakeapplestore4710]

the radioshack near me closed :(

[@markj.9177]

I get all my stuff on either amazon or direct from China if it is bulk components.

[@aaronlowe3156]

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?

[@preethamreddy9662]

Thank u for explaining in detailed manner

[@ishman1]

Great video fellow VAIO user. Thanks for the tutorial.

[@vivianzhang8287]

this circuit works well with TIP120 at 4.5 volts, as you said

[@jdennee]

very nice! now you should make a video on how to generate pwm through software :)

[@jimcovert5640]

Thanks useful for understanding dc motors in appliance's

[@yunusemreates6976]

very fruitfull tutorial.Thanks

[@gushurtado705]

This was a fantastically informational. Thank you

[@danielwalker5682]

Nice, clear and concise. Thanks

[@Shawn_White]

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.

[@rusencav]

short ,clear understandable thank you .

[@thedojoclub]

amazing explanation

[@Servant1978]

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.

[@paulmeynell8866]

Very nice project thank you

[@LNasterio]

much better explanation than my lecturer

[@Landotter1]

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...

[@frostseer]

Great videos.I learned a lot from them

[@MrSomeone4321]

PWM is oslo used in D Class Amp ;) nice tutorial! Tnx!

[@Good-Enuff-Garage]

great explanation

[@valko007]

this is a very well explained tutorial A+

[@Linrox]

nice video thanks for the upload. Could you do a video on AC PWM for a motor?

[@tylerrogers4664]

Perfect explanation. Thank you!

[@thanadams]

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!

[@RiaRadioFMHD773]

Sounds like you are attempting to regulate the speed of a 90VDC/18amp treadmill motor. Not an easy task.

[@bcsupport]

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 ?

[@FinancialConsultdotcodotza]

What if I want to have a pulse with 1.5T? Would I need capacitors or how would the circuit change?

[@thestylesworld]

Thanks for the video. Do you know how we could change the shape of the pulse waveforms, especially in pemf device circuit?

[@krishath7085]

Great video. many thanks

[@bocskai98]

The potentiometer will heat up even at slight loads. On the other hand, by heating, it consumes power = not efficient.

[@FutureAIDev2015]

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

[@letsstartsharma6679]

yes h bridge is used to change direction of motor bcoz it changes polarity very very fast

[@Landotter1]

@scrapkilla321 Depending on the circuit topology (design) you may have multiple FET's. In the case of the single transistor with a 555 timer, if you put output transistors in parallel, they all share the total load equally, in theory, but nothing is perfect. :-) If you have a 5 amp load and you put 5 transistors, each transistor carries 1 amp and the associated heat dissipation with 1 amp. If you just have 1 transistor, that single transistor must bare all of the heat and current.

[@daxweb]

i love your video style!

[@saadamiens]

you should definitely write a book with electronic experiences and link it to your videos on youtube to understand electronic concepts.

[@mateobalcorta9480]

Bwahha Ghetto hardware fun. Think I found a favorite channel.

[@prateeksabharwal1]

such an informative video! thank you so much!!

[@tricaltricks6319]

very nice one..thank you...!

[@StupidIdiot12345]

Very well made video.

[@AxelTiger]

Great tutorial, thanks for posting it!

[@VideoNinja117_Plays]

Goodness when you said "from Radioshack" I was like " Wait...how old is this?" and then I looked at the date, "Oh."

[@LucasLessio]

Thank you, Afroman! That explains a lot! Cheers!

[@siiimonz]

I actually did like to learn about PWM! :)

[@AxelTiger]

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?

[@NoorquackerInd]

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??????