What You Need For Your 555 Timer Circuits With Flashing LED
- 555 Timer IC
- 10VDC Power Supply
- 10uF Electrolytic Capacitor (16V or higher)
- 1 kΩ Resistor
- 470 Ω Resistor
- 9 kΩ Potentiometer (or any variable resistor)
- LED (whatever color you like!)
- Red and Black Wires (solid core – 22 AWG)
How To Hook It Up
For those who want a quick explanation, just hook up the pins of the 555 timer illustrated in the basic schematic below. Match up the numbers of the pins with the numbered leads of the circuit elements as shown in this diagram. You will find a more detailed explanation and image of the finished breadboard below. You can also reference the LM555 datasheet for better explanations of the pin-outs.
The Schematic Of The Circuit
The semi-circular notch on the IC chip indicates the top of the chip. The pins are numbered from 1 to 8 in a counter-clockwise fashion starting with 1 at the top left (as shown).
You want to hook up this circuit exactly as shown and with the exact same components I used because I have experienced problems quickly if you stray from the specified components. You can make it work with other resistor and capacitor values, but you may need to do some calculations to see whether it will work. You will need to calculate your time constant (T = RC) to determine how your capacitor will charge and discharge to get the appropriate frequency of flashing. In the video, I explain that your time constant equals your total resistance multiplied by your total capacitance. Resistances add in series and in parallel you have:
Where this equation gives you your total resistance. The resistor connected to the LED does not affect your time constant, but it is only there to keep your LED from frying!
Capacitors actually add in the exact opposite manner to resistors. Capacitance just add in parallel, and you can use the same equation above to add capacitance in series.
The 555 timer actually produces a square wave, like a serial clock used in digital logic, where a series of transistors inside the IC chip produce a sequence of on and off voltages at a certain frequency. Thus, 555 timer circuits are frequently used in digital logic.
Pin 1 on the timer chip is the ground (GND) pin that is connected to the common ground on your power supply. Pin 8 is where your power is supplied, and in our case it is 10VDC. The rest of the pins deal with the way that your voltage signals are timed, and this is impacted by your resistors and capacitors. Here is an illustration of what each pin is responsible for:
For more tutorials on circuits design, continue by clicking here.