Very Simple PWM With 555...Modulate Every Thing





Introduction: 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!

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

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

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 $$$$

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 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



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    131 Discussions

    Good job son! What magazine was it and what issue? I'd like to see the article!

    I don't care if you're 15 or 50, plagiarism is uncool. You need to cite your source(s), young man.

    1 reply

    it's not plagiarism! It's information; its not your fault either rather; professor's at many universities talk a lot of nonsense as if they were the inventors of things; they good at talking but hardly do any thing!! The instruction above is for education purposes only... remember!!! & he is not trying to sell you stuff! "So called purists are very keen to spread this idea of plagiarism and try to poison brains whilst they base all their rubbish theory on the work of others & why not student loans who have to furk out large sums of money for the fat cows at "Universities" (money making schemes in broad day light)...( hope people don't get the amp with everyone and heat the ceiling as it may come down!)


    11 months ago

    Hey Shams

    Which book are you using?

    Where did you get the picture in step 5?


    1 year ago


    I'd check your source circuit diagram again. The 555 data sheet states that pin 5 be connected to GND where the diagram in your post has it connected to Vcc. also it has not taken into consideration pin 7. Good work though.

    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?

    3 replies

    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

    Warehouse tug-motor fork lifts have 2 VDC batteries and they output 50-100Amps!

    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.

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

    1 reply

    Why the speed range?

    My daylight running lights operate at 4 Hz (four flashes per second) and the highest I use, at night, is 20kHz.

    If you search the EDN web site, and others, and look under 'electric bikes' and 'electric wheelchairs' you will find plenty of ideas.

    One site, from Australia, has a powered skate board (or whatever they are called) and has a complete D-I-Y 3-part articles.

    Hi shams, can i use the buck converter(LM2596) as a pwm?
    Led spot lights on my motocycle flickering when its engine is on . In my mototorcycle its a 12v 9amp battery. Pls replay. Thanks.

    I have a Kymco - 100% LED. My build.

    You have to remember that a battery's voltage can vary under normal conditions between 11-16 VDC depending upon engine speed. The voltage is even lower under start conditions.

    A typical 3-pin regulator has about a 2V drop between input and output - so the output will vary between 9-15VDC.

    Likely you have LEDs in series, Therefore, rearranging the series combinations to reduce the number of series LEDs will make them brighter (don't forget to make adjustments in the supply circuits) and your 'hog' will always supply sufficient current to drive the LEDs.

    I also picked up the power for my running light spots from where the generator output is fed to the battery. Be careful if you mess with the generator connections - one connection on modern machines is dedicated to the ignition feed.

    BTW, modern cars with super-bright LEDs cheat, often they are using a buck-boost power source and the LEDs are running as high as 60 Volts!

    Drive safe.

    Is there a better explanation somewhere. The diagram of the 555, doesn't line up with the real chip, so is confusing as hell to 99 out of 100 people!!!!! Then, you don't use the standard symbol for a potentiometer. Where is your pot? Then, no simple summary for beginners: of what capacitor goes where: between what pin and which battery poll...Also, a more flashlightaholics know the 555 should be controlling one amc7135 (10 cent chip), which should regulate a newer 225 lumen per watt Souel white led, or a 202 lpw Cree xp-l v6 led. The leds you choose are 20 lumen per watt, and aren't current constant, independent of the battery voltage. The amc is one watt or 340 milliamps. the amc needs the 555 for dimming. ...Also, no mention of heatsinking anything. Does the 555 need heatsinking? All leds need heat sinking, as does the amc's need 5 sq cm. Most flashlights run too many amcs and don't heatsink. Also, still chasing the 100 lumen per watt setups, rather than 200 lumen per watt setup. And so there is a need to make our own controllers. Will take more research to figure out the wiring, as this page falls short and needs an update.