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

3 Steps

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
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girrrrrrr2 says: Feb 8, 2009. 8:27 PM
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 in reply to girrrrrrr2Feb 16, 2010. 4:50 AM
@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 in reply to deepanjan91Mar 7, 2010. 11:01 AM
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 in reply to girrrrrrr2Jun 29, 2011. 11:54 AM
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
dannyces says: Jun 16, 2010. 4:32 PM
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 says: Apr 6, 2010. 10:51 PM
How can I add to this circuit thermistor for fan control?
Jodex in reply to 1lolooApr 7, 2010. 12:30 PM
Replace the pot with the thermistor and then it will run slower or faster in different temperatuers depending on your thermistor.