555 Astable Module
Intro: 555 Astable Module
Let me quote Wikipedia ("555 timer IC," Wikipedia: The Free Encyclopedia, June 21st, 2015)
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 ease of use, low price, 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 instructable will show you how to make a square-ware generator module from a 555 IC. A square wave is defined by its frequency and its duty cycle. The frequency is the number of cycles per unit of time and the duty cycle is the fraction of each cycle taken up by the high state. By changing the passive components of this module, it is possible to adjust the properties of the generated square wave. This module has a 3-pin SIP small footprint. The layout figure was produced using DIYLC.
You can see in the circuit figure that the 555 IC does not produce square wave out of the box but requires some wiring and passive components (image credits). This can be easily done on a breadboard, but in the end it is certainly nicer if packaged into a small 3 pin module.
In this instructable, I used values of R1 = R2 = 10 kΩ and C = 47 µF. This will generate a square wave of 1.023 Hz (almost 1 s cycle) with a duty cycle of 66.7% (2/3 of the cycle time will be high and 1/3 will be low). If you want to calculate values for a different square wave, I recommend the following online calculator: 555 astable calculator.
STEP 1: Parts
This project can be made using very inexpensive parts. Most likely, shipping will cost your more than parts...
- Small StripBoard 94x53mm (Silver), $0.74
- 40 Pin DIP SIP IC Sockets Adaptor Solder Type, $0.39
- 40 Pin 2.54mm Right Angle Single Row Pin Header, $0.17
- AWG 22 Black Hook-Up Wire 1FT (30cm) Solid, $0.10
- AWG 22 Red Hook-Up Wire 1FT (30cm) Solid, $0.10
- AWG 22 Yellow Hook-Up Wire 1FT (30cm) Solid, $0.10
- 0.01uF 50V Ceramic Disc Capacitor, $0.10 (for 10, 1 required)
- NE555 IC 555 Timer DIP-8, $0.13
- 10K OHM 1/4W 1% Metal Film Resistor, $0.12 (for 10, 2 required)
- 47uF 50V 105C Radial Electrolytic Capacitor 6x11mm, $0.03
- Total: $1.98 + shipping
As explained in the introduction section, you can change the value of the 10 kΩ resistors and the 47 µF capacitor to suit your needs. You may therefore consider buying bulk quantities of resistors and capacitors of various values.
STEP 2: Cut the Protoboard
Cut a 5 x 7 piece from the protoboard as illustrated using a Dremel equipped with a cutting disk. Make sure you cut it in the right orientation. Using a cutter, cut the first four traces as illustrated. Do not forget that you see the board upside down when you make this cut as opposed the layout image in the introduction section.
STEP 3: Solder and Add Components
Start by soldering the wires, SIP sockets, 3-pin header and 10 nF capacitor in place. Then insert the 555 IC, resistors and electrolithic capacitor in their respective sockets. Respect the polarity of the electrolithic capacitor. The negative pin of the capacitor should be connected to the top left trace.
STEP 4: You Are Done!
You are now ready to use you new square wave generator module. According to the datasheet, the NE555 supply voltage should be between 4.5 and 16 V. Also, you should not try to pull more than 200 mA from the output pin. Pinout from left to right is as follow: Out, Vcc, Gnd.
You can see the module in action with the output pin connected ground via an LED and a 1 kΩ resistor.
5 Comments
Dr_L 8 years ago
I just designed a PCB (8 pin SOIC 555, 10 nF SMD0805, 100 nF SMD0805). It should support astable and monostable modes. I have not tested it. Comments will be much appreciated.
https://oshpark.com/shared_projects/LROUWtOU
Dr_L 8 years ago
To be perfectly honest, it works for about 20 s. After that, the LED goes berseck! I have to unplug it and let it cool in order to have it work for another 20 s. I suspect I have a defective NE555. If you see something wrong in my instructable, please let me know...
Omnivent 8 years ago
You sure take the word "astable" serious ;)
I can't recall having ever seen a defective 555 (unless seriously abused), so for starters, I'd check the breaks you made in the stripboard - with a magnifying glass!
Usually, you use a ~3mm drill bit in the holes, but whichever method, always check for hair thin bits of traces partially shorting tracks.
Won't be too hard to test with another timer though.
Dr_L 8 years ago
You were right. I had about 150 kΩ resistance between all adjacent traces. Most likely it was some remaining solder flux. I cleaned it and the module is working fine.
dmwatkins 8 years ago