# 555 Timer Flashing Led Circuit

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## Introduction: 555 Timer Flashing Led Circuit

Simple 55 timer circuit built for the august Jameco build night.

simply take a 555ic, 3 resistors a capacitor and wire as shown.

## Step 1: 555 Led Flasher

Simple circuit from the jameco build night.

555 timer ic
2x 1k resistors
1x 470k resistor
1 led.
1uF Capacitor

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## Questions

Nice schematic work. 10x,

So R3 is your current limiting resistor for the LED strings right?

I am ordering TLC555CP because the specs say 2v -16.5v. Sounds cool because I want my circuit to run on a +3.7v coin cell....Hopefully I can make one that flashes a blue led something around 2 Hz ~ 10 Hz.

Had to figure out the different pin configuration for my particular 555, but got it working in only a few minutes. Thanks for the ible!

What do you mean by your particular 555, all 555's share the same pin out . There are 556's which have 2 - 555 circuits and there pin out is different because they are 14 pin instead of 8 and there is a quad version also. Pin 1 is ground ( has a dot near it),2 is trigger,3 is output, 4 is reset, 5 is control, 6 is threshold, 7 is discharge, 8 is + voltage supply.

Wt i gotta do if i hv to add 18 led instead of 1?

555 IC's have a maximum Voltage supply rating of 18 volts for the standard IC, 15 for the CMOS version. That means complimentry metal oxide, LED's require dropping a specified voltage across the LED. You can use up to 4 in series while using 15 to 18 volts for the supply of the circuit. If you are using white LED's the Vdrop is average of 3.3 volts, that gives you a Vdrop of 12.2 volts ( close enoug ). A resistor that will allow 20 milli amps the pass through the LED's is needed, get the formula for calculating the value of the limiting R and apply it to you circuit. To use 18 LED's , you should run 6 parrallel strings of 3 LED's connected in series and supply the circuit with 12.6 volts to 18 volts, remember the higher the voltage you supply ( up to 15, which is a good place to stop for any of the IC versions) and adjust the Limit R value accordinly. The standard 555 will handle 200 milli amps but it is not wise to force it to do this without using a buffer transistor connected to the output # 3 term. It will get hot. CMOS versions will not handle anymore than 100 milli amps. Do like the reply in the post above this one says and follow the math formulas, from a book about electronics. And pay attention to the data specs for the components you use.

what voltage should the LED be rated for? If this is obvious sorry im a noob at circuitry.

LED's have different Voltage drops accross them, the is a formula for calculating the resistor needed to limit the current which is supplied to them, usually 20 milli amps or less. If you are using 9 volts for the power supply about 680 to 820 ohms will give you a good range for the LED. 12 volts , do not use any thing less than 1000 ohms.The 555 IC is rated for 18 volts maximum, I would never use more than 15 volts which would require at least 1200 ohms , 1500 is better. Also you need to know how the wattage of the circuit is. That is volts times amps, most of the time you can use 1/8 watt resistors for single LED's but using 1/4 watt will keep you out of trouble better. Get some books and study them so you know what and how to do things when working with Electronics, and learn about data sheets and specifications for the parts you will be using.