Do you want to build a circuit that blinks a light? This inverter-based circuit is simple, and it’s small enough to fit on a breadboard.
The circuit uses standard basic electronic components and you can build it even if you have never built anything before. Check out the full build instructions in the video below:
Scroll down to find the complete circuit diagram, component list, and step-by-step instructions (in text-form) on how to build this circuit.
The Circuit Diagram
In the lessons, you learned that you needed an inverter for this circuit. But there’s one important point if you want to build this:
You need to use a Schmitt-triggered inverter. It’s an inverter where the voltage at which it switches from LOW to HIGH is higher than the voltage for switching from HIGH to LOW.
You’ll find the complete circuit diagram below.
The numbers next to each pin in the diagram represent the pin number on the integrated circuit. Click here for the pinout of the Hex Schmitt Trigger Inverter IC.
The Components You Need
| Part | Value | Note |
|---|---|---|
| – | Breadboard | Breadboard |
| – | 2 x Jumper Wires | Any stiff wire (22-23 AWG) |
| – | 9V Battery clip | To connect battery to board |
| BATT1 | 9V Battery | To power the circuit |
| U1 | 74C14 or CD40106 | Hex Schmitt Trigger Inverter |
| C1 | 100μF | Polarized capacitor |
| R1 | 10 kΩ | Any resistor type |
| R2 | 10 kΩ | Any resistor type |
| LED1 | Red | Standard LED (low power) |
These are pretty standard components that you can get from most places that sell parts for building electronics. I’ve created a page with a list of where to buy electronic components here. They’re also included in the Ohmify Beginner’s kit (except the battery).
Build The Circuit Step-by-Step
When you have the components in hand, you’re ready to build the circuit.
Not sure how the breadboard works? Then you might want to read How To Use a Breadboard first.
Step 1: Place the Integrated Circuit (U1)
Start with U1, the Hex Schmitt Trigger Inverter IC. Place it across the gap in the middle, with pin 1 in the upper left corner.
Step 2: Place the Capacitor (C1)
Next, place the capacitor C1. First, find the negative pin. It should be marked with minus or zero. Often the negative pin is shorter than the positive pin.
Connect the negative pin in the negative supply column. And connect the positive pin to the same row as Pin 1 of the IC.
Step 3: Place the Resistor (R1)
The resistor R1 should go from the input (Pin 1) to the output (Pin 2). Bend the legs of the resistor so that you can connect it from the row of Pin 1 to the row of Pin 2.
Step 4: Place the LED (LED1)
Next, connect the LED. The negative leg of the LED is the shortest one. Connect it to the negative supply column. Connect the longer leg to an empty row.
Step 5: Place the Resistor (R2)
The resistor R2 connects the output (Pin 2) to the LED. Place one leg of the resistor into the row of Pin 2. Place the other leg on the same row as the long leg of the LED.
Step 6: Connect GND to Minus
The GND (Pin 7) of the IC must be connected to ground. In this circuit, ground is the minus of the battery. Connect one end of a jumper wire to the same row as Pin 7. Connect the other end to the negative supply column.
Step 7: Connect VDD to Plus
The VDD (Pin 14) of the IC must be connected to the positive supply. Connect one end of a jumper wire to the positive supply column. Connect the other end to the same row as Pin 14.
Step 8: Connect the Battery
Finally, connect the red wire from the battery to the positive supply column. And connect the black wire to the negative supply column.
Your LED should start to blink.
Questions?
Did you build it? How did it go?
Let me know in the comments below.
Ed says
Hi
I’m looking to build a Star Trek TNG TRICORDER light and sounds,
But I’m not sure how to do it. Any information you could share, would be much appreciated. Or where I could find that information. They used to sell them on eBay, but I cannot find any.
bruce hull says
still struggling with the blinking light. My energy source is a solar light for area lighting with a 3.7 volt Li-ion 800 mAh rechargeable battery. it’s currently reading 2.11 volts. I’m not sure on the pin outs of the inverter. Actually I would love a pin out on the schematic.
Phil Karras, KE3FL says
7404 is the original TTL chip, look it up by searching on 7404 datasheet, in fact you can search on anything that way, 74c04 data sheet.
But pin 1 = input to first inverter, pin 2 = output of 1st inverter, the 74C04/7404, etc is a six inverter IC pin 7 = return/ground, pin 14 = Positive Voltage power source. For TTL 7404 that 4.75 – 5.25 volts, for 74C04 we know it’s at least up to 9V.
Inverter input pins
1
3
5
—-7 = Gnd
8
10
12
—-14 = + power input
Inverter output pins
2
4
6
—-7 = Gnd
9
11
13
—-14 = + power input
Ali Yoosuf says
it is very interested thank you so much.
Bruce says
Great information. I’m looking to have a LED blink but I want the LED to slowly light and then slowly go off. In a two second cycle loop. Any suggestions?
ArpitaS says
Maybe use a adruino board?
Ajaz Amin says
U can use a dimmer led instead but that will blink rapidly and slowly light off
AlbeOutlaw176 says
Yes I have a Comment why don’t you build it step by step show how to build it not just to show it light up ?
admin says
I just updated the article with step by step instructions. Hope you’ll find it useful!
bruce hull says
OK, list the parts and where I can get them. I would have loved this sixty years ago but right now I want to finish my prioject AND I do see future projects that wil required me to dig a bit deeper.
admin says
Hi Bruce,
Here’s a page with several options on where to buy the components from:
https://www.build-electronic-circuits.com/buy-electronic-components/
Best,
Oyvind
Niladri Patra says
Hi,
I want to make 3v LED Flash light with LDR.
This type of light is using fishing purpose in sea.
Regards
Niladri
Ben says
I am still unsure about how the voltage interacts with the inverter. If I track the current, it leaves the positive pole of the 9V and travels directly to the inverter (at the input labelled 14). I assumed that this was the power supply to the inverter and would be constant. And that this voltage would exit through the output labelled ‘7’ and return to the battery. Is this an activating voltage that would then cause the inverter (with no initial voltage at the input labelled ‘1’) to output a voltage at ‘2’, which would loop around and cause the inverter to switch, initiating the on/off loop? Sorry if this is confusing…
admin says
The pins 14 and 7 are for powering the inverter. When the output is HIGH, it’s from here the output gets its voltage and current, yes.
bruce hull says
OK…update. I triple checked the schematic and used a couple of combinations. First I used a 9 Volt battery with the solar light and later on LED and in both setups I got a strong resulting illumination. I then used the solar panel with the 2.1 volts with both LET setups and got a average illumination result. The appears to be a slight flickering of the lights but it is very low and fast. Hard to detect at first. What is next?
Bruce
admin says
Check out the datasheet for the chip:
https://www.mouser.com/ds/2/308/mm74c14-1193355.pdf
From there you can see that the chip needs at least 3V. So 2.1 will probably give unreliable results.
bruce hull says
I appreciate your response and that makes sense regarding the voltage level but I had the same results when I substituted a nine volt battery as the power source. My power source is a yard light that comes on at night and goes off during day light hours. The light works fine in the constantly on position but I can’t get the slow on and off that I need for my project. Any suggestions as to possible substitution?
admin says
Are you saying that your circuit is not blinking when you use a 9V battery? One potential error is that the LED draws too much current. Try replacing the resistor in series with the LED with 2000 ohms.
If it’s still not working, measure the battery voltage when it’s connected to the circuit. If it’s less than 9V, you might have a battery that is almost dead. Try replacing with a new one.
bruce hull says
new 9 v battery. I really need to get this to work with the solar panel so the batteries will recharge. the rechargeable batteries are 3.7 V. back to the drawing board.
bruce hull says
So basically for this project to work as designed I need to use the solar panel (Wal Mart outdoor light) Which is powered by a 3.7 Li-ion battery. There’s lots of sunlight in south Mississippi. Will that work with your design?
admin says
The circuit in this article should work fine with voltages above 3V. But you might need to adjust the resistor for the LED.
bruce hull says
It Works but it is blinking a little too fast. What rate resistor do I need to use instead of the 470?
admin says
It’s the 10k resistor or the capacitor you need to change to change the speed. You can for example try doubling the resistor value to 20k.
The 470 resistor sets the brightness of the LED.
Garry Cronin says
hi Oyvind,
I notice in your “Basic Electronic Components” ebook you provide a schematic for a Blinking LED using a 555 Timer IC. Can you compare and contrast the pro’s and con’s of building it that way, compared to the way you show here in this article please?
thanks
– Garry
admin says
The inverter uses less components. But other than that, for blinking an LED they’re pretty much the same.
Robert B Moore says
A step by step assembly video or series of drawings would certainly help this old person. I find it difficult to tell where to hook the components up on the breadboard.
FYI: I hope to use a modified version of this circuit to drive five LEDs on the rear pair of arms on my first quadcopter.
admin says
Hey Robert, I just updated the article with step by step instructions. Hope you’ll find it useful!
ArpitaS says
The video is not there for me.
admin says
It’s a youtube video. And it’s there. Maybe you’re on a network that blocks youtube?
Openplanet says
With all due respect, nowhere do you explain the THEORY OF OPERATION of this circuit! Without this, how can a novice possibly understand HOW and WHY it works?!
I’m a long time electronics hobbyist, so it’s no problem for me. But I’m quite amazed at the absence of an EXPLANATION in what is supposed to be a LEARNING thing.
admin says
This is how to build it. The lessons on how it works can be found here: https://www.build-electronic-circuits.com/free-email-course/
Mary Patience says
Would the LED still blink if I eliminated the inverter and worked with only the battery, capacitor and resistors?
admin says
No. The inverter is the key to the blinking.
Robert Barton says
I don’t have a cd40106 or a 74c14. I do have a 74ls14 but even with a new battery the led just lights for a moment and then goes out. If I remove and reconnect the battery the light lights for a second and then goes out.
Is it possible the LS version of the 74 14 is not compatible?
thanks.
admin says
The 74LS14 will only work with a 5V power supply, not 9V. If you switch to a 5V power supply instead of the 9V battery it should work. You might need to reduce the resistor value for the LED a bit.
John says
My light came on but did not blink. Only after I put in a different converter of the same type did it work. Maybe a faulty component? How robust are they? I had to squash the legs to get the inverter onto the breadboard. Took me a bit time to get it to work but it did eventually !
admin says
They are pretty robust. But you can break them if you connect to a higher Vcc voltage than they are rated for. Ex the 74LS14 only works with 5V, while the 74C14 works with up to 15V.
A typical error is connecting the chip upside down.
Chuck Lowe says
It was great to see the light blink. It looked like the capacitor was in parallel so I pulled
it out of the circuit and the light went steady. I am enjoying your course and look forward to learning as I grow older. I figure electronics will keep my brain healthy. I ran across an old gentleman back in 1960 who had a mantra he lived by; Sinesco Disens ( I grow old learning.) I think he is right.
Chuck Lowe
admin says
That’s great to hear, Chuck! And there’s always more to learn in electronics =)
Bob Compton says
Correction: He stays young learning!
Beau says
My first circuit! Eureka, a blinking light. Great lessons. Thanks Øyvind.
admin says
Nice! Congrats!
Azli says
Hi there,
I find your circuit very easy and straightforward. I found another method of slow blinking/blinking led circuit. Using BC 547, 100μF, 555 timer and some resistors.
My question to you is, could you help me out to design a circuit to fit in 40 LED with a function of slow blinking?
Ken M Takemoto says
Success! I assembled the components per the tutorial, and it worked the first time.
The battery connector that came with my kit has a barrel type connector on the end, versus red and black wired pins, but that can be worked around. What I’d like to know is how to insert a button switch (4 prong) with a button into the circuit so I can turn it on and off easily. First electronic project I have ever done.
admin says
Congratulations!
To add a button you can move the long red wire that goes to the upper right corner of the chip. Have that red wire go to one side of your switch instead, and connect a wire from the other side of the switch down to the upper right corner where the red wire was connected before.
Best,
Oyvind
Vip says
Can you please explain the working
admin says
You can learn it through the free email course: https://www.build-electronic-circuits.com/free-email-course/
Maybin says
What does these initials stand for
GND
VDD
admin says
It’s the negative (GND) and positive (VCC) voltage connections.
Sam Vanroy says
Using a SN74LVC2G14DCKR, powering with a 3.3v supply to mimic dev board vcc, same circuit. Using a 50 Ohm resistor on the led but can’t figure out the R1 and Cap. I’ve tried many but the led keeps blinking too fast. I’m not grasping the logic of how I should alter the values to slow down the cycle.
admin says
Hi Sam, the higher values you choose for R1 and the cap, the slower the LED will blink. If you are using 100 µF now, try with 1000µF.
Robert VanHeule says
this is the blinking light circuit I build this. cool and neat to build the circuit
Nisar says
I am unable to get the IC 74C14 from the market. But I did find IC 74HC14N, but LED is not going to ON or blinking
admin says
It should work, but note that the 74HC14 only supports a power supply of 2V to 6V. If you connected 9V you might have broken the chip.
Teslāfæn says
I think for teaching beginners about blinking a light, the relay method is better than this.
The ‘Hex Schmitt Trigger Inverter IC’ is hard to find both online and offline. (I didn’t try offline. )
admin says
You’ll find it as 40106 or 74xx14 (where xx can a number of different letters)
Lawrence says
Hi Oyvind, just tried the circuit, I’m using the sn74sl14n, the led just stays on I’m using the 10k on pins 1 and 2 with a 1k from pin 2 to the led, and using 5 volt power supply.
admin says
Hi Lawrence. The sn74ls14n only supports up to 0.4mA output current when output is high. Since you are using a 1k resistor for the LED, you would need 2-3mA to turn on the LED.
The simplest solution to this is to use a 10k resistor instead of the 1k resistor. This will only work if your LED lights up with only around 0.3mA, but many LEDs will work.
Stuart says
I have just built the flashing led using the Schmitz trigger. It works fine but the led is quite dim.
admin says
Great! And yes, the LED will be dim because of R2. 10k is quite high for an LED. You can try with 1k – although depending on which schmitt trigger chip you have it might or might not work. If you have 74C14 it will work. If you have cd40106 it might not work.
The “best” solution is to add a transistor as a switch to turn on and off the LED – then you can have it as bright as you’d like.
Stuart says
Thank you
Fire69 says
Hi,
Tried building the circuit in Tinkercad (I don’t have the inverter yet) but it’s not working.
Could you maybe have a look at it? I can’t find what I did wrong…
https://www.tinkercad.com/things/kdtHfpGMp3r-powerful-trug/editel?sharecode=n5-AFg6EjbR35YzR_qdvH61AsksPEz2fXSrFzwzWGyY
Bhushan says
Thanks sir for making electronics simple..
I want your help..
In this circuits I used 555 timer to blink..
It works…
Then make alternate blinking with 2 leds.
Then make dual alternate blinking all works great…
..
So I want make finally to blink four leds with different times..
I connect capacitor and resistor by calculating time constant one of those led at one transistor and one at the sides of another transistor…
It doesn’t work…
What’s wrong…
Please describe..