Picture of USB Blinky
My projects typically involve many LEDs and microcontrollers. However sometimes I just love the simplest of things with LEDs.

One of the very basic LED circuits is a blinky using astable multivibrator. This is the circuit that I've made - with hand drawn and etched PCB and with incandescent lamps - when I was in high school for a PCB making contest and won. I guess it still has sentimental value for me.

Now with LEDs instead of incandescent lamps, and USB power instead of batteries, here's the USB Blinkly.

I integrated the USB plug into the PCB, so it's simpler as well as economical. You can plug USB Blinky into any USB receptacles - computers, chargers, everywhere.
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Step 1: Circuit

Picture of Circuit
The circuit is an ubiquitous astable multivibrator. I used NPN type transistors and used the super-bright LESs. As the values shown in the schematics, the blinking rate is about 2 times/second. You can adjust the R2,3 and C1,2 to achieve different speed. Larger the values, the slower the speed. I recommend keeping the values of R2 and R3 between 1k and 47k ohm. At larger resistance transistors do not get enough bias current to fully turn on the LEDs. At smaller resistance than 1k ohm, too much bias current flow into the transistors. Capacitors can be as small as 1uF (very fast blink, more like flicker), or as large as 1000uF (super slow).

Current draw from the USB port is slightly under 5mA.

Step 2: PCB

Picture of PCB
I made "built-in" USB plug right on the PCB. In order to fit nicely into USB ports, I used thicker (2mm) material for the PCB. This seems to work quite well, snug enough to give good electric connection, but not too tight.
However if you find your USB Blinky to be too lose in the connector, you can put some solder on the backside of the USB plug - there are two strips of pad that you can coat with solder. By putting a good amount of solder there you can adjust the fit of the USB plug.

ledartist (author) 2 years ago
USB Blinky kits are now available at The Maker Shed.

Arduino Tech8 months ago
I made it
dudes10 months ago

I made this circuit, but used 10k Ohm and 100 Ohm resistors for brighter LEDs. Great 'ible!

CommandoNinja12 months ago


deathofme1 year ago

I was able to make this using an LDR. its very cool. so it runs on a 9v and turns on in the dark. I put a on/off switch as well so I don't kill the battery and when I really don't want it on.

Could this be made with an ldr??? If so how

Well made project and instructable. Nice work!
ledartist (author)  Awesome-aniac2 years ago

Can we use a 9v battery?
Ploopy2 years ago
newbeatle2 years ago
congratulations, so simple and nice idea!!
ledartist (author)  newbeatle2 years ago
this reminds me from my first electronic project... :D
ledartist (author)  Timofte Andrei2 years ago
That's the idea...
Theres a cool LED Halloween, well.. decoration type project on stripboard HERE
I know it isn't quite a USB thing (which is pretty by the way) but I thought you might like to know.
JVC-Force2 years ago
Very good, This may be the first LED blinky kit for USB plugs ever made! By the way, the shape looks like Jah Jah Binks, LOL!
ledartist (author)  JVC-Force2 years ago
That's true - I was thinking more like a frog...
binoyxj2 years ago
Nice. Great kit for anyone getting started.