Very simple PWM with 555...Modulate every thing

Picture of Very simple PWM with 555...Modulate every thing
Note:Any one can ask me for help.Don't comment me on my spelling and grammar.......Because my mother language isn't english.OK LETS GO

and also plz plz rate my instructable well

Hi every one.Today i'll show you how to make a PWM(pulse width modulation) out of a very famous chip 555(lm,ne any one will do) with some other parts offcourse.This is really simple and it is very handy if you want to control your leds,light bulb,servo motor or dc motor(brushless also works).
My pwm can only change the duty cyle from 10% to 90% it cant do nothing more!
Remove these adsRemove these ads by Signing Up

Step 1: What Is PWM

Pulse-width modulation (PWM) of a signal or power source involves the modulation of its duty cycle, to either convey information over a communications channel or control the amount of power sent to a load.The simplest way to generate a PWM signal is the intersective method, which requires only a sawtooth or a triangle waveform (easily generated using a simple oscillator) and a comparator. When the value of the reference signal (the green sine wave in figure 2) is more than the modulation waveform (blue), the PWM signal (magenta) is in the high state, otherwise it is in the low state.But in my pwm I will not use comparator.

Step 2: Types of pwm

Picture of Types of pwm
Three types of pulse-width modulation (PWM) are possible:

1. The pulse center may be fixed in the center of the time window and both edges of the pulse moved to compress or expand the width.
2. The lead edge can be held at the lead edge of the window and the tail edge modulated.
3. The tail edge can be fixed and the lead edge modulated.

Three types of PWM signals (blue): leading edge modulation (top), trailing edge modulation (middle) and centered pulses (both edges are modulated, bottom). The green lines are the sawtooth signals used to generate the PWM waveforms using the intersective method.

Step 3: How can PWM help us???

Power delivery:

PWM can be used to reduce the total amount of power delivered to a load without losses normally incurred when a power source is limited by resistive means. This is because the average power delivered is proportional to the modulation duty cycle. With a sufficiently high modulation rate, passive electronic filters can be used to smooth the pulse train and recover an average analog waveform.

High frequency PWM power control systems are easily realisable with semiconductor switches. The discrete on/off states of the modulation are used to control the state of the switch(es) which correspondingly control the voltage across or current through the load. The major advantage of this system is the switches are either off and not conducting any current, or on and have (ideally) no voltage drop across them. The product of the current and the voltage at any given time defines the power dissipated by the switch, thus (ideally) no power is dissipated by the switch. Realistically, semiconductor switches such as MOSFETs or BJTs are non-ideal switches, but high efficiency controllers can still be built.

PWM is also often used to control the supply of electrical power to another device such as in speed control of electric motors, volume control of Class D audio amplifiers or brightness control of light sources and many other power electronics applications. For example, light dimmers for home use employ a specific type of PWM control. Home use light dimmers typically include electronic circuitry which suppresses current flow during defined portions of each cycle of the AC line voltage. Adjusting the brightness of light emitted by a light source is then merely a matter of setting at what voltage (or phase) in the AC cycle the dimmer begins to provide electrical current to the light source (e.g. by using an electronic switch such as a triac). In this case the PWM duty cycle is defined by the frequency of the AC line voltage (50 Hz or 60 Hz depending on the country). These rather simple types of dimmers can be effectively used with inert (or relatively slow reacting) light sources such as incandescent lamps, for example, for which the additional modulation in supplied electrical energy which is caused by the dimmer causes only negligible additional fluctuations in the emitted light. Some other types of light sources such as light-emitting diodes (LEDs), however, turn on and off extremely rapidly and would perceivably flicker if supplied with low frequency drive voltages. Perceivable flicker effects from such rapid response light sources can be reduced by increasing the PWM frequency. If the light fluctuations are sufficiently rapid, the human visual system can no longer resolve them and the eye perceives the time average intensity without flicker (see flicker fusion threshold).

Voltage regulation:

PWM is also used in efficient voltage regulators. By switching voltage to the load with the appropriate duty cycle, the output will approximate a voltage at the desired level. The switching noise is usually filtered with an inductor and a capacitor.

One method measures the output voltage. When it is lower than the desired voltage, it turns on the switch. When the output voltage is above the desired voltage, it turns off the switch.

Variable-speed fan controllers for computers usually use PWM, as it is far more efficient when compared to a potentiometer.

Audio effects and amplification:

PWM is sometimes used in sound synthesis, in particular subtractive synthesis, as it gives a sound effect similar to chorus or slightly detuned oscillators played together. (In fact, PWM is equivalent to the difference of two sawtooth waves. [1]) The ratio between the high and low level is typically modulated with a low frequency oscillator, or LFO.

A new class of audio amplifiers based on the PWM principle is becoming popular. Called "Class-D amplifiers", these amplifiers produce a PWM equivalent of the analog input signal which is fed to the loudspeaker via a suitable filter network to block the carrier and recover the original audio. These amplifiers are characterized by very good efficiency figures (e 90%) and compact size/light weight for large power outputs.

Historically, a crude form of PWM has been used to play back PCM digital sound on the PC speaker, which is only capable of outputting two sound levels. By carefully timing the duration of the pulses, and by relying on the speaker's physical filtering properties (limited frequency response, self-inductance, etc.) it was possible to obtain an approximate playback of mono PCM samples, although at a very low quality, and with greatly varying results between implementations.

In more recent times, the Direct Stream Digital sound encoding method was introduced, which uses a generalized form of pulse-width modulation called pulse density modulation, at a high enough sampling rate (typically in the order of MHz) to cover the whole acoustic frequencies range with sufficient fidelity. This method is used in the SACD format, and reproduction of the encoded audio signal is essentially similar to the method used in class-D amplifiers.

Speaker:Using pwm it is possible to modulate arc(plasma) and if it is in the hearing range,it can be used as a speaker.Such speaker are used in Hi-Fi sound system as tweeter

COOLLLL right?

Step 4: Thing you will need

Picture of Thing you will need
because it's a simple one chip circuit you won't need lots of part

1.NE555,LM555 or 7555(cmos)
2.two diodes 1n4148 is recomended but you can also use 1n40xx series diodes
3.100k pot(volume control pots are good for this circuit)
4.100nf green cap
5.220pf ceramic cap
7.power transistor
Easy right?

Step 5: Building it $$$$

Picture of Building it $$$$
Just follow the diagram and put all parts on the breadboard.Recheck every thing twice before you power it up.if you want to drive efficiently and control the brightness of a light source or a motor you can only put a power transistor on it out put but if you only want drive a light source or a motor efficiently then put a higer rating cap 2200uf is recomended.If put this cap and drive a motor on 40% duty cyle then your motor will be 60% efficient at almost same speed and same torque.Go build it now

there is two video.you can watch how pwm works.and my pwm really works with out any op amp
1. u can see the fan starts to spin 1/2 sec then is starts to spin on 90 % duty cycle
2.u can see the leds blinks like the blinker of cars the it is on 80% duty cycle

P.S:plz plz rate this instructable with higher rating.I'm only 15 years old.Good-bye

my next instructable will be a arc speaker with pwm

1-40 of 113Next »
ddanial0141 month ago

Hello.. i want to drive a diode with input of 1.5amp and 12 volt so can i do it using this circuit if so then how much amount of current do i have to give as input

Can you show me how to build a PWM that can take 110V DC at 15A? For a go kart.

yaly5 months ago

What's its output frequency please? I need something more than 20 Khz preferably 40 Khz

dsamsudin9 months ago

couldn't download the videos, corrupted

shiv.ram.7909 months ago

well can u please tell me in detail that how it can be used to drive a brushless dc motor?

shams (author)  shiv.ram.7909 months ago
You see,there are 3 wires in a typical dc brushless motor. positive,gnd and pwm....you have to connect a stable positive and gnd connection then connect the pwm wire to the output of this circuit

Are you sure it will really work? Because to run a bldc motor, you must need to find the position of the motor. Then you have energize the coils based on that location by using sensors or without sensors.

Have you really tested it in a brushless motor?If so can you please post me the circuit? Thanks..

shams (author)  shiv.ram.7909 months ago

Yeah I am sure,if I wasn't sure I would'nt have said it in the first palce !Those circuits are integrated in almost every BLDC motor.The circuit analyses the width of the given pulse and changes the speed of the motor.You can try is too if you have a BLDC motor (cpu fan,pc exhaust fan,rc bldc motors etc).

you can also control a servo with pwm the same way

Okay got it. So I need to connect my bldc motor and ESC with this circuit to control it. Am I right?

I am looking for a circuit to drive an IGBT or MosFet. The goal is to regulate a battery 3-4.2 volt input 0-100%. @ full charge it must handle 150 watts output @ 100% on time. Additionally I would like the control to be push button as opposed to a variable resistor. with a digital % power led display. Is this to complicated?

shams (author)  thekraftyrhino1 year ago
I dont get it....what kinds of batteries are you trying to use? Cause i dont think you will be able to get 150watt of output from a typical battery which would supply 3-4volt
Not typical they are Turnigy 60amp 160 amp burst rated output LiPo. IT is 3.7 volts (4.2 hot off charge) we currently use it wired thru a solid state relay. trying to explore moving to a 2s battery that has higher compacity. making the device Variable from 3-6 volts with PWM MosFet or IGBT is our mission. I am able to use your 555 to cut cycle time to our desired area but we want more control and without the dial rheostat.

Hi Dilshan, I am building a battery powered LED torch with 4X1.2V 1200mA batteries, and 3X3W LEDs I am trying hard to find a driver which could do the job of connecting them together

the LEDs I have are,
LED, HIGH POWER, 5000K, 70CRI, 275LM
LED Colour: White
Luminous Flux @ Test: 369lm
Forward Current @ Test: 1A
Forward Current If Max: 1.2A
Forward Voltage @ Test: 2.86V.

could you please help me what should be the specifications of the driver??

shams (author)  selvam123451 year ago

Dilshan ? Whats that ? And how did you connect your LEDs ?Are they in series or parallel ?
IMO driving high powered LEDs need critically engineered drivers. I will advise you to use LED driver chips or LED driving module ! :)

Sorry about the name being mixed up
I have no idea about whether to connect the LEDs in parallel or series.and yes i understand i should get an LEd driver chip,

The question is what should be the output characteristrics of the chip and can these LEDs can be powered at all by the batteries that I have.

May thanks for the comment though :)
shams (author)  selvam123451 year ago


as you can see you will need a 100% efficient driver which doesnt exist.so you will need higher voltage or higher amp

I will suggest you to hook your LEDs in series as parallel is not as efficient as series

you can use one of these drivers



I have found a couple of drivers, which seem to fit my design of 4X1.2V batteries

the problem here is all these drivers are meant for applications(flahlights) here only one LED is used

now, should i use the one which provides a constant current of 1A (http://dx.com/p/5-mode-led-driver-circuit-board-for-flashlight-dc-3-6-9v-106487#.UyBVtfmSxWY)and connect the LEDs in series


should I go for a driver which provides 3A and connect the LEDs in parellel (http://dx.com/p/t6-2500-3000ma-3-mode-regulated-led-driver-circuit-board-for-diy-flashlight-4-5-18v-128269#.UyBWW_mSxWY)

shams (author)  selvam123451 year ago

you cant just hook up leds in parallel cause you will run into the risk of burning out the leds. You will have to connect resistors to each led if really want to conncet them in parallel

shams (author) 1 year ago
shams (author) 1 year ago
plapić1 year ago

which power transistor did you use??
and where does it go in the schematic??
please respond quickly

shams (author)  plapić1 year ago

ummm tip 32 maybe....but you can use any transistor provided it meets your spec.The base of the transistor is tied to the output of the circuit

NIce tutorial, I have a question if you don't mind: I have a 555 connected to a transistor hooked to a small HF transformer . When I change the pulse width manually say from 58% to 80% and keeping the same 25khz frequency, the secondary voltage drops to very very low instead of increasing. I am utterly confused
jackricci2 years ago
dude you are dominating the electronics game for a 15 year old
shams (author)  jackricci2 years ago
Thnks man !............ i am now 19 :)
IronWill3 years ago
Good job.
Would you be so kind as to please tell me the title of the textbook you are referencing?
it looks like a really useful book.
jhaneyzz3 years ago
I think I get it all until it comes to connecting the TIP31. I am trying to dim a 12v lamp. Low voltage bulbs used along walkways.

I tried to connect the power transistor based upon what little I could see in the picture, and I ended up frying the 555.

Could someone help me figure out the correct schematic. It would seem to differ significantly from the "magazine article" diagram, given the picture shows a power transistor as well as a 2200uF cap!


What kind of power transistor are you using? Is it a FET? I believe the problem you are experiencing is due to high current during the power transistor turn-on.

This is most likely exceeding the drive capabilities of the 555 and is frying the chip.

I believe the solution for you (if you are using a FET) is a proper mosfet driver IC. The PWM signal from the 555 would hook into the driver, and the driver would control your FET.

An additional benefit of dedicated drivers is that a faster on/off transition decreases switching losses, and thus reduces the heat on the FET. I recommend taking a look at Linear Technology parts, as their data sheets are excellent, and their free circuit simulator (LTSpice) is also very good.

This IC: http://www.linear.com/product/LTC4441 Might be close to what you need...

Good luck!
I'm using a TIP32 just like in the picture. This is a standard pop voltage regulator.

But I don't see any guidance in how to place this in the schematic.
boredomandi3 years ago
you need to control the current not the voltage with leds! check onsemi part NSI45030AT, the data sheet explains it very well. once you have a maximum current then(say 30 mA) use the 555 to change the voltage. and shams your engish is just fine!
camservo3 years ago
Any suggestion on how to modify this to be used as a dimmer circuit for the backlight on an LED monitor? I've measured the LEDs at 32v. I'm still learning electronics, but I've seen dimmable monitors go for 4000 dollars!
shams (author)  camservo3 years ago
Actually its kind a complicated...because leds on led monitors are in matrix so u cant dimm them without complicated digital circuit....
rakesh911184 years ago
Dear I have made PWM with 555, and its working good as power supply m using 12V 1Amp. adapter available in market for CCTV cameras it's around Rs.75 to Rs125/- only. I have made this 39 LEDs (3LED in series with 47E resistance in 13 parallel lines ) in 1" PVC baton used in Electric wire fitting on walls. My Qus. is if we glow the LED array on full brightness with PWM, is it will long lasting. Becoz if we run array with more current, the LEDs go burn or go dim after few days. I set it on 9.5V (3 leds=3.1vX3Leds=9.3V) But its light is not much bright at this level. I have used white LEDs Ratting 3 to 3.2V and 10ma. Pls suggest on what level of voltage I have to set for long life and good bright light.
shams (author)  rakesh911183 years ago
yes it might be....bt leds are very sensitive to current changes...u may need a current regulator..to make it longer lasting....or you have to use resistors with but efficiency will be low
Is it possible to wire this up with a NPN transistor rather than a PNP ? I want to drive a 1A 12V motor. Thanks,
hubi4 years ago
This is a cool circuit for dc motor speed regulation, i have built it and tested with a dremel like tool.

Tipp for your next plan, you can use 2 *555.
The first one will run in astable mode the 2nd one is a voltag econtrolled monostble, triggered by the first one.
A nice Tool for this is 555timer pro from http://www.schematica.com/
for your purpose the free demo would be sufficient.
shams (author)  hubi4 years ago
Thanks.I will consider using it
Hello, your post said I could ask,,here goes!   I am new to electronics though of middle age,,"GUESS",,  I am wanting to pulse modulate my service meter to my home to reduce cosumption to EVERYTHING,, is this possible or am I going to have to cut my power line from my "Cap Rock power Company" to eliminate there constant greedy grasp to my wallet?
shams (author)  shouldawoulda4 years ago
no you cant pwm AC...sorry bro...its impossible...only DC
you actualy can, but you have to get the phases to stay in tuned, which is harder than dc where you done have phases.
1-40 of 113Next »