Instructables

How to use 555 timers

Simple 555 timer curcuit. very basic. flash an led on and off.

video included
 
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Step 1: Get Parts

Picture of Get Parts
you will need:

- 1x ne/se 555 timer IC chip.
- 1x solderless breadboard
- 1x source of 8 or more volts (i had 18)
- 1x 5V voltage regulator (if you dont have one you can use a 6v lantern battery.
- 2x 0.5k resistor (you can use anything from 0.5 to 1.5)
- 2x resistor (i used 2 and 5k, it would be better to use higher values)
- 2x 47 Uf electrolitic capacitors. (these can vary)
- 1x flasher led (red)

Optional components:

- 1x power led(green)
- 1x 300 uf electrolitic capacitor (value can go lower, this just prevents spikes)
- 1x switch

Step 2: Make power supply

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(skip to 1.5 if you are using batteries)

insert your 5v regulator in the mannar shown below. this is the setup for the regulator:

pin function
1 input
2 ground
3 output
you read the pins from left to right on the front of the regulator

attach the wires in the picture. 18 volts positive goes to pin 1. ground goes to pin 2, and the 5v out goes to pin 3.

step 1.5

you can add an led and switch if you want. it makes it easier to debug not working circuits.
if you add an led you can test your circuit and regulator now

Step 3: Power your chip

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turn off the power and carefully insert your 555 chip on the board. you will have to bend the pins in slightly to get them to fit. try rolling it on the table GENTLY.

now. its on the board you need to connect the power to your chip.
here are the pins functions:


1 Ground
2 Trigger
3 Output
4 Reset
5 control Voltage
6 Discharge
7 Threshold
8 Vcc


the pins are labled 1-8 starting at the dot then going around the chip

so hook up +5v to pin 8
JerryBYong2 months ago

Hi I wanted to use the 555 timer for a solenoid because I wanted to simulate recoil for a prop gun. Is this possible? I think the solenoids require 12v

andrew101 (author)  JerryBYong2 months ago

It is possible. Will depend on what you want your 555 to do in the circuit.

the 555 timer can be used to time the solenoid opening/closing, say for example once every few seconds, or a few times a second. The 555 can also be used for "Pulse Width Modulation", if say you wanted it to return slowly or something.

If the solenoid works fine on 12 volts, figure out how much current it will draw at that voltage. Many solenoids draw over 500 miliamps, or even many amps depending on the purpose, and this kind of current would damage the 555 timer. You'll need to use a relay, opto-isolator, transistor (BJT or mosfet), or something of the sort to isolate the 555 from the solenoid to stop damage from happening.

nachoarr1 year ago
Hi I found your post very interesting to start my research with the 555 timer. I had the idea of using it to activate an step motor for a time lapse travel base that I would like to build. The only drawback I could find is using your post to promote a website that looks like a scam, selling a outdated version of a free flight simulator. (http://www.flightgear.org/) Kind of left a sour taste in my mouth after following your nice explanations. Regards
mykiscool2 years ago
Shag carpet in the background. Groovy
mcmahanly2 years ago
Or perhaps you know somewhere i can find this info?
mcmahanly2 years ago
A more accurate title for this instructable would be "How to assemble an LED flasher circuit using a 555 timer." Otherwise, I would suggest adding more information about the behavior of the 555 chip and what calculations/behaviors a person would need to know to make their own 555 circuit.
Very nice.. What few changes will be needed to run 12v. and make the LED steady, but blink, every 20-30 seconds or so. REASON : RED LED and fiber optics to appear as eyes watching in the night darkness and blinking > WHAT little animal could that be ?? A great "foundation" to start with... AGAIN - nice
andrew101 (author)  tinkerunique3 years ago
an R1 value of 100Kohm, a R2 value of 2Kohm, and a capacitor value of 470 microfarads will produce the following result:
On time (t1) is 33.2 seconds.
Off time (t2) is 0.651 seconds.
Duty cycle is 98.1%.
Frequency is 0.0295 Hz.

To experiment with values, use this website:
http://www.horrorseek.com/home/halloween/wolfstone/TechBase/com555_555TimerCalc.html
chaoschao993 years ago
can i change this from an LED to a pushbutton hack? as in use the wires that connect to the Led to hack a button so it presses every 3 or four seconds?
andrew101 (author)  chaoschao993 years ago
yepp you can use this for that. a common circuit example would be a rapid fire mouse button for games. what you need to look at is the button being triggered, a straight input wont work most of the time. for example, if the button is switching 5 volts and sending it to a controller, this will work, but if it is grounding it, or doing something else funky, it would be more effective to add some sort of electronic switch, such as a npn or pnp transistor. In curcuits that wont need to be totally accurate on timing could use a small relay to do the job.
im really not the best at electronics and all i want to do with this timer is connect it to a mouses left click so that like every four seconds. i took apart my mac mouse and i found that there is a 3 pin switch there. i was just going to randomly test the wires to find out which is positive and negative and then attach some wires from the breadboard where the LED should go onto the positive and negative of the switch.
andrew101 (author)  chaoschao993 years ago
Okay, its good that you are testing the positive and negative of the switch, but that might not work in all cases. I'm going to attach a picture of what i mean. Another thing that isn't shown in the picture, in some cases the person that made the device might have done some tricky stuff with their switches, in the example of a computer keyboard, everything has massive charliplexing, if that is the case you will need trial and error with transistors, or using relays would just work (but is slightly less timing accurate)
Switches.jpg
so im not ALL that smart so all i want to know if its possible
andrew101 (author)  chaoschao993 years ago
yea its totally possible.
sweet also, does lowering the number of ohms in the resistors make it flash less or more?
andrew101 (author)  chaoschao993 years ago
The less resistance the faster it flashes. The lower the resistance the quicker it is for the capacitor to charge and discharge.
thanks one last question, does the power source have to be 8 volts or could it be a 9 volt battery
andrew101 (author)  chaoschao993 years ago
Most 555 timers support having an input from like 5 to 12 volts. In my case i had an 18 volt input, so i used a power regulator to bring it down to 5 volts. you can power it with a 9 volt battery, but if you were connecting it to a mouse it could be damaged by 9v (depending on the components you used to connect it) but yea, a lot of people use 9 volts because they are easy.
thanks sooo much i built it and it works like a charm! i hope you like your patch! also i am having a small struggle trying to figure out how to make it so that the LED only lights up for about a second and stay off for about four....is this possible? if it is then tell me what two resistors i need to use. thanks a ton
andrew101 (author)  chaoschao993 years ago
There is some math involved to figure it out, or you can plug in the numbers to an online calculator like this:
http://www.horrorseek.com/home/halloween/wolfstone/TechBase/com555_555TimerCalc.html

(just found it on google)

in the case of this video this is what the 555 is configured to do:
On time (t1) is 0.228 seconds.
Off time (t2) is 0.0651 seconds.
Duty cycle is 77.8%.
Frequency is 3.41 Hz.

hope that helps you find what you need.
ok so i am so thankful for your help im working on it as we speak, also what happens if you run it without any resistors?
andrew101 (author)  chaoschao993 years ago
it would just go ballistic i think, im not exactly sure, it might damage parts so i wouldn't recommend it....
as in would there be enough power to connect the curcuit
milsorgen4 years ago
 So if you were using say a USB port of your computer you wouldn't need a voltage regulator would you as it provides a fairly consistent 5v, right?
andrew101 (author)  milsorgen4 years ago
yes you could do that.

but if your driving anything other than leds do not use usb power, you could risk damage to your computer with things such as motors.

just make sure the circuit is built before you apply power and it should have no problems with this circuit though.
zybro andrew1013 years ago
What's the risk of running motors with USB power? How can you reduce or avoid the risk?
andrew101 (author)  zybro3 years ago
USB can only supply 500mA of current, and most motors will use a lot more then that. Because of this your motors cant run well because they cant get enough energy. Another thing is the huge voltage spikes that come off coils. The motors have coils inside that upon being disconnected from the power source (when the motor turns around) will create massive voltages back thru your electronics (in this case the computer) that can be fixed with a simple diode placed the opposite way across the motor's contacts.
 but well, can u suugest how to choose resistor.... i have a 9v supply....and a led....which uses 3.3v...and 20mA.......what is the resistor used...?
and how we come to know that LEd use 30mA?????
andrew101 (author)  13thThief4 years ago
well if you have a 9v supply, and your leds require 20 ma, then your resistors should be 450 ohms. how do i know this? simple calculations, here goto this site, it does it for you:

http://www.sengpielaudio.com/calculator-ohm.htm

(put in 2 known values and it gives you 2 others, so for example in goes volage and amperage, and out will come your resistance. note: amperage is in AMPS, and 20 ma is 0.02 A!)

now you could go searching everywhere for a 450 ohm resistor, but the standard resistor size for leds is normally a 470 ohm resistor, that will protect most leds at low voltages. so if you have a 470 ohm resistor that is good, just as long as it is not a value below 450 you are set.
have fun!
 UR right :-)
Colonel884 years ago
I did the same exact circuit again, but with some revisions.

I didn't put in power source; used 2 AA batteries.
Put in a jumper from pin 4 to +.
No capacitors for spike control.

It works fine now, before it didn't work correctly.
andrew101 (author)  Colonel884 years ago
2 AA batteries provide 3 volts, that is the minimum possible voltage to power the circuit I believe. so it will only operate for a short time, and once it dips below 3 volts it wont work right.

and the 2 capacitors are there because i had a very VERY bad power supply.
Colonel884 years ago
Very good job i used to know how to make this, then forgot, the nyou helped me remember again :D. Now i shall make a... CUSTOM RAPID FIRE MOUSE, to use with counter strike sources double pistols :D
andrew101 (author)  Colonel884 years ago
yes, rapid fire buttons are AWESUM
JUST MADE IT. Does like 65 clicks per 10 seconds on avg. Thanks for schematic!
andrew101 (author)  Colonel884 years ago
nice, so are you using a transistor to trigger the button?

i have a mouse that had a rapidfire button built in. (it only gives you 3 clicks though, i might mod it yet)
No, I just linked the output to the negative of the left mouse button.

IE Before you bridged the gap in mouse button and electricity flows to negative from positive, not you just flow electricity to negative 6.5 times a second.
knektek4 years ago
if you get the 555 timer to be working at a fast enough pace, you wouldnt need a resistor and it will appear to be running normally. like a joule thief.
phillyj4 years ago
Excellent job, friend. I was able to use my new breadboard also. Thanks
phillyj phillyj4 years ago
Here's a video I made. I used a variable resistor to change the hertz. Couldn't find my other switches so I used a rotary switch pulled from a mouse. 9V batt. much better than wall wart i.e. much smaller+less wire.

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