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.
Step 1: Circuit
Current draw from the USB port is slightly under 5mA.
Step 2: PCB
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.
Step 3: Parts
- 2x 5mm Super Bright LED
- 2x 470 ohm 1/8 or 1/4W (R1, R4) (yellow-purple-brown-gold)
- 2x 47k ohm 1/8 or 1/4W (R2, R3) (yellow-purple-orange-gold)
- 2x 22uF 10V or higher Electrolytic Capacitor (C1, C2)
- 2x NPN General Purpose Transistor (Q1, Q2)
- 1x Custom PCB
If you are using "standard" type LEDs (non "super bright"), you might want to give them more current to get the decent brightness. Use 220 or even 150 ohm for R1 and R4 (up to 20mA with 150 ohm).
Dig into your parts drawers or junk box. You might have all the parts you need (except maybe the PCB). Of course you can purchase the PCB or full kit from my site.
Step 4: Assembly
However if you are completely new to soldering, you might want to do a bit of practice before assembling USB Blinky.
Start soldering the low profile pars first - try soldering in this order:
- Resistors - Bend the leads, insert them into the holes on the PCB, flip the PCB over, and solder.
- Capacitors - bend the lead at the bottom of the body, watching the polarity. Longer lead is the positive (+).
- Transistors - match the shape of them with the marking on the PCB. Bend the leads to fit the holes. Solder.
- LEDs - watch the polarity again. Longer lead goes into the hole with the square pad. You can also use the shape of LEDs and the marking on the PCB to identify the orientation. (One side of LED is flat)
Step 5: Plug it in!
Pick your favorite color LEDs and make one. Happy blinking!