Simple (and dirty) Pulse Width Modulation (PWM) With 555 Timer

Simple circuit for DC Motor speed control (fan speed control, light / LED dimming and etc) using the 555 timer.

Also a good starting point for novices wanting to get their hands dirty with the 555 timer IC. Some would argue that this is not the most efficient approach, but hey (read the title), it's simple, and it works.

Check the video out.
More images and description here.

Pulse Width Modulation (PWM)

Put simply PWM is the process of switching power ON and OFF to a device in pulses at a specific frequency. Same approach used in commercial light dimmers, DC motor speed controller, CPU fan speed controllers and etc.

That's what we seek to achieve here.

Step 1 Part List

Part list

1) 555 timer IC - 1
2) 100K variable resistor - 1
3) 1N4148 Diode - 2
4) 100nF capacitor - 2

The 555 Timer IC

The 555 timer is arguably one of the most popular IC ever made. There are thousands of resources online if you're interested to delve deeper into the subject. I'm just going to give the simple description directly relevant to the build

PIN 1 - Ground
DC Ground

PIN 2 - Trigger
When LOW, it causes the Output pin to go HIGH. Activated when voltage fall
below 1/3 of +V.

PIN 3 - Output
Output is HIGH when Trigger pin is LOW. Output is LOW when Threshold pin is
HIGH. Output is LOW when reset pin is LOW.Output pin is able to source or sink
current.

PIN 4 - Reset
Short to +V when not in use.

PIN 5 - Control Voltage
Grounded through a capacitor when not in use.

PIN 6 - Threshold
When voltage reaches 2/3 of +V, this pin will cause Output to be driven LOW.

PIN 7 - Discharge
Grounded when Output pin goes HIGH.

PIN 8 - +V
DC Power

Comments

[Homepwner]

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[Chein]

Something like Fritzing http://fritzing.org/ may help you a bit i think.. It has a pretty neat breadboard view feature

[Homepwner]

I've been checking out some other schematics that I found easier to comprehend.
yours is different then the ones I'm used to and I think that is part of my problem.
Thanks for the link! it sounds awesome.

[budhaztm]

ok so with the caps do you mean 100 microfarads or 100 nanofarads? im building this for a very large science project which i will post online. thanks for help

[jamesjamesjames]

what is the advantage of this over just a motor and a pot?

[pauls_boat]

using a motor and a pot when you slow down the motor the extra power is just turned into hear in the pot using this when you slow the motor you are just turning it off and on very fast and dont wast the extra power

[solaralternatives]

Paul meant to say (waste) heat.

[mnova]

I only have a 20K pot but the circuit still works if I give the motor an initial spin.

How can i increase the power output on this circuit?

[solaralternatives]

Use it to drive a cheap power transistor

[jagzi]

Hi,
We are connecting a motor to the circuit, shouldn't we attach a protective diode for taking care of the back EMF ? Please clarify.
Thank you in advance .
Jagzi

[nseguin]

Hi, I'm new to electronics and have given a shot a building this. Unfortunately my local Source didn't have the exact list of what I needed. I used 2 100uF capacitors, 2 1N4001 diodes and a 3W pot. When I try and control a small motor, no success. I'm using a 12V battery. Any ideas or suggestions?

[camservo]

I'm also new. I built this circuit and noticed that, while I had a 12v source, the output was only in the realm of 1v. Not sure where the drop came from. Might be a mistake I made, might be part of the design.

[simonrc]

Hi and thanks for the instructable! I would like to add a photoresistor in order to modify pwm speed by light intensity, but I'm not quite sure where to put it - in between IC pin 3 and center of pot? I would be most grateful for help! thanks!

[btdzimba1]

I tried simulating the circuit before i built it and noticed that the 100k pot doesnt seem to do anything

[girrrrrrr2]

is there a way i could get you to add a pic of the chip with the wires on it because this is just a little confusing to me... (my first try with a 555)

[deepanjan91]

 @girrrrrr2 : count/number the pins of the IC in ascending order and counterclockwise from the notch. There must be a notch on the IC. Hope this helps

[girrrrrrr2]

true true...
i was just kinda wanting a pic with it all hooked up so i could see this is what i want to achieve.

[edalgetty]

a friend of mine told me this: just draw the 555 and then draw the circuit around it, its a little tedious but i think its really worth it

[BG79]

Hi. I tryed to make this, but instead of reduce or increase leds brightness it just turns it on and of with a little delay. Any bet where I went wrong?

And is there a way to make this PWM outputs ~ 500mAh? I´m trying to use it into a superled, but 200mAh is too low. Tkz.

[zs]

if i made 2 of these, and instead of a motor i used a speaker, would it be similar to a extremely basic droning machine like the Grendel drone commander?

[robot1398]

good project.
works great

[dannyces]

ok so i just tried this and i get nothing.... i mean i get the led to light up but i get no change when i turn the pot??????

[1loloo]

How can I add to this circuit thermistor for fan control?

[Jodex]

Replace the pot with the thermistor and then it will run slower or faster in different temperatuers depending on your thermistor.

[livehybrid]

Hi there,
Thanks for this - I have made 3 of them.
I am hoping you may be able to help with my problem.
I have numerous RGB LEDs which I will be connecting in parallel.
They have a common -ve, therefore instead of using pin 7 to control the brightness I use pin 3.
This works fine at the moment for one RGB LED with 3 of these PWM however I want to add a number of other LEDs...
Can you suggest how I might do this? Would I need to add an amplifier or transistor? if so, how would I go about this? Obviously it needs to cope with the frequency...

Many thanks!!

[alienmeatsack]

This simple PWM looks like it should be capable of something I've been asked to investigate by my brother.

He wants to take an old video camera and hack the motor that drives the playback/record, adding a pot so he can change the speed.

I think this looks like it could do that. I assume I will probably need to add some kind of switch to turn it off/bypass it for normal speeds. And something to keep anything from getting fried.

The only real thing I would be concerned about is burning out the motor. It's not like it would be something I could just easily replace. Ya know?

Anyone have any suggestions/recommendations in regards to this particular use?

[shams]

Hey any one don't hook up a motor with this circuit it will fry the chip.use a transistor

[cdousley]

i keep thinking your picture is edward cullen im glad its not. twilight isnt that cool really.

[shams]

 nope bro IT's chris redfield

[Resident Expolsives Expert]

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[shams]

any one!low power 2n2222a.med power tip31/32.high power 2n3055 or any mosfet with driver

[stefannasehi]

how much power is low, medium, or high? is low 1.5v, medium 9v, high 12v? where would you put it?

[shams]

nope I'm talking about current rating not voltage !

[Derin]

No,it's the amount of watts it can switch.

[fallenspirit123]

Oh... and by the way, how do u use a transistor for this circuit?(i might know some ways but making sure)

[fallenspirit123]

actually it depends on the motor and voltage

[12V]

i have made 2 of these and they worked (c1 was 220nf) but they died when i connected them to my 12v battery it is supposed to be for up to 18v?

[GorillazMiko]

Nice Instructable. I hope I can try this out, looks a bit complicated for me though. +5/5 stars.

[thermoelectric]

You can do it, just buy the parts and follow thw instructable, thats what it's there for isn't it

[Resident Expolsives Expert]

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