Instructables

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!
 
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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.
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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 days 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 days 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)  thekraftyrhino6 months 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.
selvam123457 months ago

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
Series: LUXEON TX
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)  selvam123457 months 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 ! :)

selvam12345 shams7 months ago
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)  selvam123457 months ago

3x3watt=9watt
4x1.5x1.5=9watt

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
http://www.ebay.com/itm/50W-Constant-Current-LED-D...

http://www.ebay.com/itm/30W-White-High-Power-LED-L...

http://www.ebay.com/itm/10W-Cool-White-20000K-High...

selvam12345 shams7 months ago

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

or

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)  selvam123457 months 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) 7 months ago
shams (author) 7 months ago
plapić8 months ago

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

shams (author)  plapić8 months 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
jackricci1 year ago
dude you are dominating the electronics game for a 15 year old
shams (author)  jackricci1 year ago
Thnks man !............ i am now 19 :)
IronWill2 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.
jhaneyzz2 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!

Help!
jhaneyzz,

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.
boredomandi2 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!
camservo2 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)  camservo2 years ago
Actually its kind a complicated...because leds on led monitors are in matrix so u cant dimm them without complicated digital circuit....
rakesh911183 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)  rakesh911182 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,
hubi3 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)  hubi3 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)  shouldawoulda3 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.
shams (author)  shouldawoulda4 years ago
nope it cant be done.Because pulse modulation's frequency  will cause intefierence in your AC frequency thus you wont get the rated voltage and power ....actually it will pump more voltage to your electronic equipment because of high frequency...and smoke every thing
hubi shams3 years ago
Sorry,
but this is onlythe half story,
it is possible to use PWM on AC, but it isn´t that easy, the PWM Frequency has to be high enough, synchronized to AC and you need special switch, since you can´t use a mosfet to switch AC. A Mosfet in a bridge amplifier from + to - output and the ~ connected in series to supply and load should do.
If you weren't new to electronics I might suggest that you design a device to do this. As Shams says you can't modulate AC but you could rectify your AC to DC to charge a large battery bank and then build yourself an adjustable inverter. Basically you'd build a giant uninteruptable power supply. To buy one for your entire home would likely cost a small fortune but you might be able to build one yourself much cheaper. I don't think that's a simple project though. So I guess the short and sweet answer is still no. At least it would be for me... I'm lazy and that's a lot of work haha!
BG793 years ago
Hello. Is there a way to make this PWM output ~ 500mAh? I´m trying to use it into a superled, but 200mAh is too low. Tkz.
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