Introduction: HackerBoxes 0004: Three Fives Replica and 555 Timer Experiments

Your timing is perfect! This month, subscribers to HackerBoxes are building a jumbo-sized, functioning replica of the 555 chip from discrete transistors. We are also working on several experiments based upon the venerable 555 timer chip, which is the integrated circuit that has sold more units than any other chip in the entire history of semiconductors. The 555 has already earned its place in history while still widely in use to this day.

This Instructable contains information for working with HackerBoxes #0004. HackerBoxes is the monthly subscription box service for electronics hobbyists, makers, and hackers. If you would like to receive a box like this right to your mailbox each month, please SUBSCRIBE HERE and join the HackerBoxes adventure!

Even if you are not a HackerBoxes subscriber, you can still join in the fun using your own materials and equipment. Also, you can get a Three Fives Kit from our friends over at Evil Mad Scientist and you can find various 555 project kits from our friends over at Nightfire Electronics.

Step 1: HackerBox #0004 Contents

This month we made a BOXING VIDEO while packing the box. Have a look.

  • Three Fives Kit (Black PCB, Aluminum Lead Stands, Thumbscrews)
  • Evil Mad Scientist Decal
  • Solderless Breadboard
  • Various Jumper Wires or Dupont Jumpers
  • 9V Battery Terminal
  • 8 Ohm Mini-Speaker
  • Momentary Buttons (five)
  • LEDs (ten)
  • 7-Segment LED Display (Common Cathode)
  • Photo Resistors (two)
  • 555 Timer Chips (three)
  • 4017 Decade Counter Chip (info)
  • 4026 7-Segment Display Driver Chip (info)
  • 2N3904 NPN Transistors (thirteen)
  • 2N3906 PNP Transistors (thirteen)
  • 1N4148 Switching Diodes (ten)
  • Various Capacitor values (0.01uF, 0.1uF, 0.47uF, 1uF, 3.3uF, 10uF, 22uF, 220uF)
  • Various Resistor values (100, 220, 620, 820, 1K, 3.9K, 4.7K, 5.1K, 6.8K, 10K, 15K, 22K, 33K, 68K, 100K)
  • 10K Potentiometer
  • 500K Potentiometers (two)

EXPLOSIVE! Please Note that some of the capacitors are electrolytic capacitors. These are polarized, which means that each capacitor has a positive lead and a negative lead. The polarity of such capacitors needs to be used properly within the circuit or the capacitor may explode, rupture, or otherwise fail.

PART ALLOCATION! Also note that some of the components in this list (and in the HackerBoxes) are required for building the Three Fives Kit. It would be wise to pull all of these out (and maybe just go ahead and build the Thee Fives Kit) prior to consuming any of the components in other projects or experiments. Here are the specific items from the parts list that are needed for the Three Fives:

  • 2N3904 NPN Transistors (thirteen)
  • 2N3906 PNP Transistors (thirteen)
  • Resistors (one each): 100, 220, 820, 1K, 3.9K, 6.8K, 10K, 15K
  • Resistors (two): 100K
  • Resistors (seven): 4.7K

The list above is a general list of items needed for the projects and experiments presented here. Please note that the exact characteristics of contents within a particular HackerBox may vary by color, type, manufacturer, count, or so forth due to sourcing and bulk packing.

Step 2: Introduction to the 555 Timer

The 555 timer is an integrated circuit (IC) chip used in a variety of timer, pulse generation, and oscillator applications. It was introduced in 1971 by American company Signetics and is still in widespread use due to its low price, ease of use, and stability. It has been estimated that one billion 555 ICs are manufactured every year.

The 555 chip contains 24 bipolar transistors, two diodes, and 15 resistors forming six functional blocks:

Green Block: A voltage divider consisting of three identical resistors connected between the supply voltage VCC (+) and the ground GND (-) generates two reference voltages 1/3 VCC and 2/3 VCC.

Yellow Block: A first comparator evaluates the threshold input pin voltage against the 2/3 VCC reference voltage.

Orange Block: A second comparator evaluates the trigger input pin voltage against the 1/3 VCC reference voltage.

Purple Block: A flip-flop stores the state of the timer and is controlled by the two comparators. The reset input can override the other two inputs such that the flip-flop (and therefore the entire timer device) may be reset at any time.

Pink Block: An output stage follows the output of flip-flop. The totem-pole output block can be loaded at the output port up to about 200 mA.

Blue Block: An output transistor is connected, via its collector, to the discharge output port.

It's interesting to play with this interactive online simulation of the signals within the 555 timer chip.

For further reading, there is a lot of information about the 555 chip and see a lot of example circuits at Talking Electronics. (Be sure to click through to all three pages.)

Also quite interesting is an oral history of the 555 timer chip from the Semiconductor Museum site. (Be sure to click though to all nine pages.)

And lastly, a very nice video of simulations for some 555 circuits.

Step 3: Three Fives Replica Kit

The Three Fives Kit, from the folks over at Evil Mad Scientist Laboratories, allows you to build your own beautiful, jumbo replica of the 555 Chip from discrete transistors. Best of all, it actually works. This ultra-geek-chic item is at home in both the lab or on display in your office or study. This well-made video is a great introduction to the kit.

While the Three Fives Kit includes excellently detailed instructions, it worth reiterating some additional pointers. Start by putting in the resistors since they are a little smaller. Double check that each resistor value matches those silk-screened on the printed circuit board. The resistors are not polarized. They can go in either way.

Next, solder in the transistors. Double check that you are putting the transistors from the NPN bag into the holes on the board labeled "2N3904" and be sure they are correctly oriented. They will not work if reversed. Similarly, be certain to place the transistors from the PNP bag into the holes on the board labeled "2N3906" and again carefully observe their orientation.

The Evil Mad Scientist site has a fantastic wiki page for this kit and the 555. It includes the kit instructions, a lot of likes to resources, and a really great Principles of Operation document that is worth checking out for sure. While you're there check out their online store where you can find a lot of other great items.

Dave over at EEVblog made this very detailed, and accordingly quite long, video covering build and operation of the Three Fives Kit. Like all of his videos, it is extremely informative. It is interesting to note that Dave's kit has the older version of the Three Fives support legs, which were plastic, while we now have the new aluminum ones.

Keep in mind while working with the experiments that follow that you can use an actual 555 timer chip in an 8-pin DIP package, or your can use the Three Fives replica. They should function identically. Give it a try!

Step 4: Oscillator for Blinking an LED

The 555 Timer IC has three operating modes: Bistable, Monostable, and Astable. These modes are determined by the other components and connections attached to the chip. In the astable mode, the 555 functions as an oscillator. This is generally the simplest mode to jump into experimenting with.

This video illustrates building and testing this circuit on a solderless breadboard. The 555 timer is configured as an astable multivibrator allowing it to generate a continuous oscillating output. This is useful for, among many other things, blinking lights or making sounds.

Here is a 555 oscillator tutorial.

Check out a visual simulation of a square wave oscillator using a 555 timer chip.

Here is another video showing a similar circuit being assembled on a solderless breadboard. This video has a bit of theory of operation of the oscillator circuit.

Step 5: Oscillator for Driving a Speaker

This demonstration illustrates driving a speaker using a 555 chip in oscillator mode.

Step 6: LED Sequence Scanner

This explanation and video illustrates building an LED sequence scanner using the 555 timer. This effect was seen on the KITT Car from the Knight Rider television show and also the Cylons in the original Battlestar Galactica television show. Accordingly, such circuits are often referred to as the Knight Rider Oscillator or the Cylon Oscillator.

The folks at Evil Med Scientist coined the term "Larson Scanner" for this effect. They have some cool Larson Scanner Kits should you ever need one for a demo or costume. Their name for these kits is a nod to Glen Larson who produced both the original Battlestar Galactica and Knight Rider shows.

Step 7: Reaction Timer Game

Test your reaction speed! This explanation and video illustrates building a Reaction Timer Game using the 555 timer chip.

Step 8: One-Step Sequencer Music Box

This Instructable shows how to build a Music Box Circuit using the 555 Timer Chip.

Step 9: Five-Key Toy Organ

This project demonstrates building a simple five-key toy organ using the 555 Timer Chip. Here are some more examples of this circuit including videos.

Step 10: Atari Punk Console (APC)

The Atari Punk Console (APC) requires two 555 timer chips, so you will sometimes see designs using a single 556 dual timer chip, which is basically just two 555s in one package. The APC, technically called a stepped tone generator, gets its popular name from the fact that its "low-fi" sounds resemble classic 1980s Atari console games. The APC operates as an astable square wave oscillator driving a monostable oscillator thus creating a single square pulse. The APC has two potentiometer controls. One potentiometer controls the frequency of the oscillator and the other controls the width of the pulse.

This instructable shows how to breadboard the APC and even gives an option for using light control similar to your next project.

Here is a cool video from Make: about the APC.

Synthrotek has a nice APC kit as well as lot of other related "low-fi" audio toys.

Step 11: Theremin

A theremin is an is a musical instrument that is played by sensing the electromagnetic fields associated with teh moving hands of the operator using one or more antennas. A simplier "light sensistive" version can be made using photoresistors also known as photocells or light-dependent resistors (LDR). Of course the oscillations controlled by the LDRs can be generated using the 555 timer chip as shown in the circuit here. This video illustrates assembling the light sensitive theremin on a solderless breadboard.

Step 12: Even More 555 Related Projects...

So many 555 projects and resources can be found online. Here are some great examples:

Colin Mitchell has some of the ultimate 555 information as well as hundreds of 555 circuits on the Talking Electronics site. The site also offers a lot of 555 related items and kits for sale.

Rob Paisley has assembled a long catalog of 555 Timer Circuits.

At ElectroSchematics, you can browse through a total of 127 circuits and projects using the 555 timer chip.

Lastly, Make: shared this amazing 555 stool project. Now that is a giant 555 chip.

Step 13: Have You Mastered the 555 Timer?

If you think so, how about a little test?

Step 14: Hack the Planet

If you enjoyed this Instrucable and you would like to have a box like this delivered right to your mailbox each month, please SUBSCRIBE HERE.
Does your Three Fives replica operate just like an eight-pin DIP 555 chip? What do you think about the soothing tones of the Atari Punk Console? Please share your success (below or on the HackerBox Facebook page) and certainly let us know if you have any questions.

Thank you for being part of the HackerBox adventure. Please keep your suggestions and feedback coming. HackerBoxes are YOUR boxes. Let's make something great!


demms made it! (author)2016-10-12

After assembling the Reaction Timer Game (Step 7) circuit, I added another 555, configured in bistable mode to drive the reset line of the 1st 555. Also added a 3rd button to separate the Start operation out from Reset. The Start & Stop buttons are connected to the Trigger & Threshold pins (with p/u & p/d resistors) of the 2nd 555. Now the count halts even after the Stop button is released.

AtomTrigger made it! (author)2016-03-06

I built the giant 555 project as soon as my box arrived. Very cool! In my experience, most "scale" models have been scaled down. I love that this one was a scale up.

I built a Larson scanner this afternoon. Totally awesome for a guy who grew up on Knight Rider and BSG. (Remember in the opening credits for the A-Team when Templeton "Faceman" Peck A/K/A Starbuck encounters a Cylon at Universal Studios?! Priceless.) Anyway, building this was a lot of fun!

One questions for the experts: Why are the diodes upstream of the LEDs necessary?

HackerBoxes (author)AtomTrigger2016-03-06

Diodes can be used to implement a "wired OR" which is basically a cheap logical OR gate to combine two outputs from the counter to drive each LED. Some implementations just use resistors instead of the diodes.

AtomTrigger (author)HackerBoxes2016-03-07

Thanks for the info. Makes sense. I get that some of the LEDs can be powered by 2 different pins from the decade counter. In this case though, doesn't the decade counter only power 1 pin at a time? So the diode prevents the unpowered pin from seeing voltage from the powered pin. But is there a risk associated with applying power to an unpowered output pin? I.e. is it really necessary in this application or is it just "good form"?

I guess in the spirit of hackerology, I might just try it w/o the diodes and see if the whole project bursts into flames. But i definitely appreciate the insight of the pros.

HackerBoxes (author)AtomTrigger2016-03-07

Be careful thinking about them as "unpowered output pin." Generally digital output pins are effectively attached to one of the rails. The rails being Logic_Zero (0V or GND) and Logic_One (typically 5V). Unless output pins are "open collector" (see link below) we never want an output pin "driving" a zero to be directly attached to an output pin "driving" a one. That's called a short, and as we all know, Electrical Engineers do it without shorts. At the very least, you want to have some load between the two pins for the 5V to drop across (waste as heat). Notice in the schematic for Step 6, there are 200 ohms (TWO 100 ohm resistors) between each output pin. Ideally (not often the case), the logic and/or code is designed to just never have any outputs fighting each other as that is a waste of electricity and introduces undue thermal cycling.

AtomTrigger (author)HackerBoxes2016-03-07

Awesome, totally makes sense. Thanks for the explanation!

HackerBoxes (author)AtomTrigger2016-03-07

Be careful thinking about them as "unpowered output pin." Generally digital output pins are effectively attached to one of the rails. The rails being Logic_Zero (0V or GND) and Logic_One (typically 5V). Unless output pins are "open collector" (see link below) we never want an output pin "driving" a zero to be directly attached to an output pin "driving" a one. That's called a short, and as we all know, Electrical Engineers do it without shorts. At the very least, you want to have some load between the two pins for the 5V to drop across (waste as heat). Notice in the schematic for Step 6, there are 200 ohms (TWO 100 ohm resistors) between each output pin. Ideally (not often the case), the logic and/or code is designed to just never have any outputs fighting each other as that is a waste of electricity and introduces undue thermal cycling.

zal42 (author)2016-03-05

I loved the three fives kit, and wanted to display it as an art piece. I thought it should actually do something, though, so I built the Larson scanner into a low-profile project box with the LEDs poking out the side. The box is short enough to fit comfortably under the assembled three fives kit. Now the kit display is compete: it's beautiful, and the glow from the LEDs emanates from beneath, shifting left and right.

I think I'll modify the design somewhat and use one of the photoresistors in the box to adjust the pulse rate of 555 so that the scan rate changes according to the immediate light level, to add a touch of interactivity.

This box has been (and continues to be) great fun! Thank you!

chris25b (author)2016-03-03

Can't wait for mine to arrive, I run several Code Clubs and am always looking for new things for the build table, and a Giant 555 chip fits the bill nicely. :) good work :)

grtyvr (author)2016-03-02

Yay! For three days now I have been all....


I am glad that it is this cool!

Wolfbane221 (author)2016-03-02

I'd love that 555 hacker box. really cool! That working jumbo 555 is awesome!