The first step in building any electronic circuit, after you have decided what it is going to do, is to design and draw a circuit diagram from which you can build the circuit. I have already calculated the component values for you and tested it to make sure it should work for you. Actually the theory and calculations involved in this circuit are very simple which is exactly how I like it.

Don't worry too much if you don't understand what all the symbols mean yet because you don't need to for this project. You should be able to follow along with this circuit build easily without referring to the circuit diagram.

Astable multivibrator oscillator circuit diagram

R2, R3
10k Ohm resistor: Brown - Black - Orange.

R1, R4
470 Ohm resistor: Yellow - Violet - Brown.

C1, C2
Electrolytic capacitor. Note this component must go in the correct way round. The black band generaly denotes the -ve end of capacitor.

D1, D2
Light Emitting Diode. Note this component must go in the correct way round. The larger electrode inside the LED is generaly the -ve side of the device.

T1, T2
Transistor. Note this component must go in the correct way round. Check the package of your transistor and be careful to get the Collector, Base and Emitter into the correct position.

V1
9 volt alkaline battery.

Snap on 9 volt battery connector.

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Tagged: Basic Electronics Electronic Projects Simple Electronics Projects Multivibrators Astable Multivibrators Led Projects Simple Electronic Projects

Comments (5)

Topic: How To Build An Astable Multivibrator Circuit Without Solder

5/5 (1)

Amalia (US) says...

Can anyone tell me how to place 2 toy DC motors on the breadboard so that they intermittently go on and off like the LEDs? Or is this not possible? I want to use it to power a toy that zig zags. I'm going to try it anyway tonight but I would like help on where to connect the motors on the breadboard since I am a novice. Thank you.

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19th August 2019 8:10pm

Richard says...

An excellent little circuit! Thanks. I shall be using this for a dummy alarm. Any ideas how long the nine volt battery will last (i.e how much current does the circuit consume)?

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6th August 2015 3:56pm

Steve (UK) says...

Hi Richard,

As it stands the circuit consumes about 15mA and if the battery is alkaline with a capacity of 625mAh then it should last approximately 30 - 40 hours.

You can try increasing the values of the two collector resistors R1 and R4. Common high efficiency LEDs will still glow brightly with only 1mA so try replacing the 470 ohm resistors with 4.7k ohm. This theoretically should allow the battery to last for up to 600 hours.

Steve

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6th August 2015 11:34pm

James says...

Wow, super cool... my first brush with electronics! I am curious, how can you change the rate of flashing? Also, how would you apply this circuit to producing a audible noise (sine wave)? Again, thanks so much!

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23rd November 2014 8:59pm

Steve (UK) says...

Hi James, I'm so pleased that I've interested you in electronics. You are where I was 50 years ago. The flashing rate is controlled by the two pairs of resistor/capacitor R2/C1 and R3/C2. Increase the values of the two capacitors to slow the flashing rate. Decrease the values to increase the flash rate. You cannot use this circuit to produce a sine wave but you can make it produce audible signals. Signals become audible at around 5Hz to 16KHz. If you decrease the capacitor values so ... Read More

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23rd November 2014 11:46pm

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