What is 555 Timer?-The 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse generation, and oscillator applications. The 555 can be used to provide time delays, as an oscillator, and as a flip-flop element. Derivatives provide up to four timing circuits in one package.
Introduced in 1971 by American company Signetics, the 555 is still in widespread use due to its low price, ease of use, and stability. It is now made by many companies in the original bipolar and also in low-power CMOS types. As of 2003, it was estimated that 1 billion units are manufactured every year.
This is the first step in my learning to use the 555 timer chip. It alternately blinks two LEDs, and you can change the frequency by changing either the resistance or the capacitance. The 555 is not programmable like an Arduino or an ATtiny. You have to change the values of the capacitors and/or resistors to find the desired frequency. This is also a handy tool you can use to quickly find the right values to set the frequency for another 555 project. If you just want to just blink one LED that will work too. Just leave off either LED and it’s 330 Ohm resistor. But two is twice the fun.
You will need:
- 555 timer https://www.sparkfun.com/products/9273
- 2 330 Ohm resistors **
- 10 4.7K resistors
- Red LED
- Green LED
- Hookup Wire (Red, Black, Yellow, Green)
- An assortment of capacitors *
- Long male headers https://www.sparkfun.com/products/12693
- 9V Snap Connector https://www.sparkfun.com/products/91
- 9 Volt battery
* This capacitor kit will give you enough capacitors to get started. Or use what you have. I just grabbed a handful of different capacitors from my parts bin.
** This resistor kit has all the resistors you will need for this project, and a lot more.
Step 1: Assembling the circuit
Assemble the circuit as shown in the diagram.
The green wire should be long enough to reach the last resistor.
The little dot on the 555 marks pin one. It should be in the upper right corner.
Step 2: Directions for use.
Move the green wire to the resistance you want to use, the more resistance the slower it will blink.
You can try different capacitors, just put them in the same columns as indicated in the diagram. If you are using an electrolytic the minus side (short lead) goes to the black wire.
You can plug more than one capacitor in. If you do the capacitance adds when capacitors are connected in parallel.
The more capacitance the slower it will blink.
A 10 uF electrolytic capacitor is a good place to start. The blink rate was about 1/2 second with the lowest resistance setting and about 5 seconds at the highest.
With a 220 nF capacitor and the lowest resistance setting the lights were blinking so fast they appeared to be on all the time.
With a 200 uF capacitor and the lowest resistance setting the blink rate was about 12 seconds. When I set it on the highest resistance it was very slow. I can’t tell you how long it was, I got bored watching it.
It is okay to change either the resistance or the capacitance while the circuit is running. This seems to be a tough little chip.