41 LED Flasher Circuit Using 555 IC





Introduction: 41 LED Flasher Circuit Using 555 IC

I made this as a quick project I made to use a lot of the LEDs I recently got. It basically connects via a 555 8 pin IC and allows for adjusting the time between the flashings by changing the resistor or capacitor values. It provides for a cool looking effect in a dark room. Use your favorite color LEDs and enjoy!

Step 1: Gather the Parts

Okay, so let's beign.
Here is what you will need:

1 - Timer 555 8 pin IC
1 - 2N3905 PNP general switching transistor
1 - 2N3053 NPN general purpose amplifier (I dont know if this is a switching or amplifer but I used MPSA2222A instead and it worked fine, I also tried 2N3904 and it worked, but a littler worse than the one I used)

20 - red LEDs (although you can use any color choice you want)
20 - blue LEDs (although you can use any color choice you want)
1 - LED (this is used to verify if your circuit works, can be any color)

1 - 1uF Electrolytic capacitor
1 - .1uF disc capacitor

1 - 150k resistor
1 - 4.7k resistor
1 - 160 ohm resistor
1 - 220 ohm resistor (although I used a 160 ohm)
20 - 100 ohm resistors (I didnt have 20 so I used 10 of 100 ohm and 10 of 120 ohm)

1 - 6V source

Step 2: Build the Circuit

So here is the layout of the circuit. It is pretty basic. Here are some notes so you can better understand what is going on.

The notes were taken from the page mentioned later.
"Two sets of 20 LEDs will alternately flash at approximately 4.7 cycles per second using RC values shown (4.7K for R1, 150K for R2 and a 1uF capacitor). Time intervals for the two lamps are about 107 milliseconds (T1, upper LEDs) and 104 milliseconds (T2 lower LEDs). Two transistors are used to provide additional current beyond the 200 mA limit of the 555 timer. A single LED is placed in series with the base of the PNP transistor so that the lower 20 LEDs turn off when the 555 output goes high during the T1 time interval. The high output level of the 555 timer is 1.7 volts less than the supply voltage. Adding the LED increases the forward voltage required for the PNP transistor to about 2.7 volts so that the 1.7 volt difference from supply to the output is insufficient to turn on the transistor. Each LED is supplied with about 20 mA of current for a total of 220 mA. The circuit should work with additional LEDs up to about 40 for each group, or 81 total. The circuit will also work with fewer LEDs so it could be assembled and tested with just 5 LEDs (two groups of two plus one) before adding the others."

Step 3: Modify the Final Project

Here is the final product of mine. I have added a switch but that is not mandatory.

Okay, now editing the flashing rate is easy. You only need to change 1 or more of the 3 values of R1, R2, and C.

Use these equations to do so.

Positive Time Interval (T1) = 0.693 * (R1+R2) * C (time first set is flashing)
Negative Time Interval (T2) = 0.693 * R2 * C (time other set is flashing)
Frequency = 1.44 / ( (R1+R2+R2) * C) (flashes per second)

Step 4: View the Final Product

Here is a video of my final result. The colors I chose made it look like a police light. I should have thought this through and not have chosen those colors together :)

This project was found at http://ourworld.compuserve.com/homepages/Bill_Bowden in a beginners 555 timer circuit page.

I bought the LEDs from http://www.abctronics.com



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    127 Discussions

    can you put any ammount of voltage or current through this circuit.

    please tell me you do a step by step guide as this is exactly what i'm after for a cosplay build


    what is the purpose of the 100 ohm resistor in the circuit?

    the link is not work ,

    I want to see the result ???

    Dear Sir please tell me the circuit diagram for making string light of 20 led light with blinking

    If I'm trying to get LEDs to flash at different rates, will I need several different timers or is there a timer that offers several rates for flashing?

    Hi! Just a Suggestion Here,,,,I built this little baby and noticed one thing,,after leaving this circuit on i noticed the transistors were getting warm especially the 2N3053 (Max Ic of 600 M.A.) To Alleviate the Problem I subbed 2N3053 for Tip31(Power transistor,,,Ic of 3 amps) and 2N2905 for TIP41 (Power Transistor Ic of 3 amps) 2 advantages here,,,,, 1) Transistors will remain cooler here. 2) you will be able to add a pile of extra Led's to this circuit and the Tip's should be able to Handle the extra loads.. This is still a really Good Instructable,, but If we can improve the circuit why Not??!!?? We might be able to double or even triple the Led output and the TIP's should be able to take it!!! Supes this is a SUPER INSTRUCTABLE!!!

    4 replies

    If I use the TIP31 and TIP41, can I use 100mA LED per stripe? and if so, how many?
    I would like to use this project to be seen day, like the LED traffic lights.

    @luis..Hi!!,,,,, I checked the Data Sheet for the Tip41 and if properly Heat Sinked for DC,,Ic= 6A and Pulsed Ic=10A If you used Ic=6A the max stripes @100ma would be 6 / .1 =60 but I would use only 30 so I would provide the Transistor with proper headroom as to not push the Tip 41/42 into DESTRUCTIVE MODE!!! Remember The 555 Timer can source or sink 200ma so that is where the Tip 41/42 come into play..I hope This helps you!!!! If you don't use a Transistor with proper power ratings you will cook this 555 into the danger zone!!!

    Thanks for respond.
    I put the TIP31 and TIP41 with 160 ohm resistor in each transistor base. I use two 100mA LEDs per stripe with 15 ohm resistor, for 5 stripes in parallel . My power supply are two 3.7v ultra fire batteries to get 7.4v. I don't know if the base resistor in the transistors are correct. I'm getting 6.7v to 36.5mA in the 555 output, I suppose its correct to the 200mA limit. Should I use heatsink for transistors?
    PD. I don't know to much about electronics.

    Hello sir i m very interested in learning electronics works so please tell me about my questions my second question is how can check a 555 I.C With multi Meter???

    2 replies

    I dont know if you would be able to read the pulses of a 555 ic using a multimeter. But if you have acess to an oscilloscope you more than likely would be able to see the pulses on it. I have never done such a thing, but Im sure its likely.

    I used a Logic Probe connected to pin 3 of the 555 timer to "see" the Pulses..Just a Suggestion!!!

    i dont want switching between red and blue i want combine flickering of 41 leds what can i do

    plz.. tell