Picture of Make your own Enigma Replica

EDIT: This Instructable has won Second prize in the 2013 Radio Shack Microcontroller Contest. Thank You to all who voted!

EDIT2: Our "Open Enigma Project" Kickstarter is now over. Please visit if interested. THANK YOU for your support!

This is our very first Instructable and this step by step guide will show you how to build a fully functional electronic replica of the world famous German Enigma machine. This Arduino based Open Source project is able to encrypt & decrypt any Enigma M4 encoded message.

This first ever fully functional Open Source Enigma "exact " Replica was inspired by the Kid's Game to Arduino Enigma Machine by sketchsk3tch.

Using Charlie-plexing Multiplexing for the LEDs, this circuit with 115 light emitting diodes uses only 38 pins and the 36 push buttons use only 4 pins total thanks to properly placed resistors (and the P-Channel MOSFETs) in the keyboard loop. These 4 16-Segment displays & an LED for each keyboard button would add up quickly the total number of pins required and even the Arduino Mega would have ran out of pins without the 2 methods mentioned above....

In response to the overwhelming demand, we designed the PCB and made it available through Skip to Step 10 & beyond for more info. We also offer it as a complete electronics kit & an assembled & tested complete product.

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Step 1: Proof of concept on Breadboard

Picture of Proof of concept on Breadboard
Before going all out on the development of this electronic Enigma replica, we wanted to make sure we could properly drive the 16 Segment LEDs. If we can do that, than we will be able to do everything as the rest is only Math...
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ST-Geotronics (author) 1 year ago
Boards are tested, working great and available now for shipping. Kits & assembled/tested/boxed Enigma Replicas are also available. to order.
DIY93931 year ago
This is amazing!

You deserve a reward!
If you don't mind me asking, how much did all of this cost you?
ST-Geotronics (author)  DIY93931 year ago
Thank You DIY9393 for the kind words.
I guess we should have mentioned the hardware costs in the instructable. All in all, we spent less than $200 in materials. But QUITE a few hours...
No problem!

Thanks for the info!
ST-Geotronics (author) 1 year ago
The PCB drawing phase is completed. We have ordered them from the Fab & are anxiously awaiting their arrival so we can populate & test 1 set ensuring that everything works fine. As soon as this crucial step is completed, they will be available for ordering/shipping.

NOTE: There was NOT enough space on the Enigma PCB to have all necessary components AND connect to the Arduino Mega2560, so we had to create a daughter card for the Mosfets & to receive the Duino. This daughter card will be sandwiched between the motherboard & the Mega2560.
ST-Geotronics (author) 1 year ago
We just posted the second and last Circuit Schematic (for the lampfield and keyboard) at the end of the instructable.

We will start soon working on the PCB design, so stay tuned. Don't forget to vote, every vote counts. Thank You!
Thank you!!
reflector wheel=b
wheel order 1,2,3ring setting A,A,A
ground setting RAF
ST-Geotronics (author) 1 year ago
In response to the popular demand, we just added the first of 2 Circuit Schematic at the end of the Instructable. You can now find how each of the 4 16-Segment Displays are wired. Stay tuned: We are currently working on the 2nd Circuit Schematic, which will show the rest of the Perfboard wiring: how the 26 keyboard buttons, the 10 function keys, the 26 keyboard lamps & the 5 LEDs are all hooked up. After that, we will design & post the PCB file.

Thank You for the overwhelming positive feedback & don't forget to vote for this Instructable in both contests if you enjoyed it.

thompsms1 year ago
I just can't wait for the PCB!! Astounding. You deserve a Bletchley Park Medal.
Junophor1 year ago
I am really deeply impressed!!
Take a bow

Yours Aeon Junophor
bob30301 year ago
Most intriguing instructable I've seen. Must be a record for lines of code in an instructable. Your patience in the wiring is commendable. I would be interested in the PCB you mentioned. Thanks for posting.
DavidO225 days ago

What exactly are the "Alpha buttons" and where can I find them?

Are LEDs attached to them to light up the correct letter, or how does it work?

ST-Geotronics (author)  DavidO225 days ago
DavidO2, for the first unit we ever made described in this instructable, (and the next couple), we used normally open buttons containing a blue led with a cap with a character of the alphabet. We found these on ebay but seem to no longer be available. These were a pain to install and solder, not to mention very expensive.

Since then (and for every machine sold in our kickstarter), we simply used surface mount white LEDs and added a printed sheet on top that contains every key in sequence of the keyboard. This provides more light and looks a lot more like a real Enigma...

Visit for components, kits and assembled/tested units...
Razapple127 months ago

What kind of buttons did you use? I'm trying to make one... :) This is a really great looking replica by the way

ST-Geotronics (author)  Razapple127 months ago
Razapple12, Like most everything else, we found them on eBay:

Search for something like: "Momentary Tactile Push Button Switch 12x12x11mm DIP + Black Round Cap"

This is an example:

Razapple127 months ago
Where did you buy your buttons?
ST-Geotronics (author)  Razapple127 months ago

Razapple12, Like most everything else, we found them on eBay:

Search for something like: "Momentary Tact Tactile Push Button Switch 12x12x11mm DIP + Black Round Cap"

This is an example:

nwsayer8 months ago

This is great, but it always astonishes me greatly when folks embed a prototyping board in a custom printed circuit board design. If you're going to all the trouble to design a custom printed circuit board, then why not just embed the ATMega chip directly into your design? It just can't help but be cheaper, lighter and smaller that way.

MarkCauer9 months ago

How does the arduino measure the resistance if there is no current traveling through the resistor and pushbutton setup? Shouldn't there be a ground somewhere?

qbrown21 year ago
I guess i can peak at the code but how did you translate the 7 segment digit dispays to nixie ?
ST-Geotronics (author)  qbrown21 year ago
QBrown2, we didn't:

The 7 Segment displays are actually 16-Segment displays (17 if you count the decimal point) and we are using these as opposed to 7 Segment so we can have a nice Alphabet.

We decided to wire them standing up & encapsulate them inside a test tube to give it somewhat the look of period accurate Nixie Tubes.

So, no Nixies were used in this project...
P.S. the printed circuit board we made allows for 16-Segments LEDs to be horizontal or vertical, but still has not been designed with Nixies in mind...
ST-Geotronics (author) 1 year ago
Thanksgiving Holiday brought us our Prototype boards. We are now busy populating & testing one to make sure it works as great as the proof of concept does. We are now accepting orders at & expect very soon to start shipping. We added Step 10 to this Instructable to show pictures & more details.

ST-Geotronics (author) 1 year ago
We are finished drawing the motherboard PCB (top), and have started drawing the daughter car (interface between top PCB & Arduino). Daughter card is required cause we can't fit all components on motherboard. As soon as daughter board is complete and we verify they fit together in Enigma machine, we will send them for production. We expect both boards in our hands sometime in December.
Thank you. Will you upload the PCB design file?
ST-Geotronics (author)  englishfire1 year ago
Yes englishfire, we will upload both PCB design files (Motherboard & Daughter Card) once they are both complete & tested. We are aiming for sometime in December.
Any news about the PCB?
ST-Geotronics (author) 1 year ago
stringstretcher: Reflector wheel= C Wheel order = 3,2,1 ring setting A,A,A Ground setting = USA IYRF TTQP DUPA AIMC DBTG YTNF

It would be interesting to use Wamco KW-105AL numitrons. They operate at 5 Volt and are alphanumeric.
NoseyNick1 year ago
Love Enigma. Love Arduino. Love LEDs. Love Nixie-tubes. Gotta love LEDs pretending to be Nixie-tubes. Love this project! :-)

Would love to see the rest of the circuit - can you explain the charlieplexing and the analog keyboard?
ST-Geotronics (author)  NoseyNick1 year ago
NoseyNick, the full circuit schematic is now posted in the instructable.

We need to make a correction, as "JuMP" pointed out about the Hackaday article on our Enigma (, for this project, we are not Charlie-Plexing, we are simply Multiplexing.

Multiplex is just a little simpler to code as we only deal with two states of logic: high or low. It also lets us drive the common anodes easily with a p channel mosfet. This allows more current so a brighter display while observing the rated maximum current limitations of the atmega 2560.
To truly “charlieplex” requires three state logic: high, low, and open. To achieve the open, the pin mode needs to be changed from output to input thus releasing the 2560′s internal pull up and pull down circuits. True charlieplexing would have saved us 7 pins however we did not feel that it was appropriate to sink the anodes of up to 17 LEDs to only one IO pin.

The Analog keyboard refers to all 26 keyboard buttons plus 10 function keys only using 4 analog pins: All 10 functions keys are daisy-chained to Analog 0 with a 1Kohm resistor between each button. Same thing with the first row of 9 keyboard buttons being separated by 1KOhn resistor and daisy-chained to Analog 1. And so on for middle & bottom rows of keyboard...

Then, all we do to know which key has been pressed is read the resistor value at the Analog Pin. Since each button needs to go through a different qty of resistors before it hits the Analog pin, you end up with a different value that is consistent for each key. Very reliable, simple design... We possibly could put even more keys one 1 analog pin, but figured that 1 row per pin was good enough...

Neat idea, thanks for sharing. So, I enter a letter at a time and it is encrypted and shown on the display. Correct?
Does your version have the capability to enter a string of characters, encrypt each character, then cat the encrypted characters into a string and either save it in a file or send it out the serial line?
ST-Geotronics (author)  three_jeeps1 year ago
Three_Jeeps, thank you for the feedback.
Not correct on the process: Just like the real Enigma, for each key you press on the keyboard, a encrypted letter gets lit on the lamp field right after the 16-segment display shows you the new "rotor" position.

The existing code in this Replica was written to emulate as close as possible the operation of a real Enigma. Your suggestion is currently accomplished by many simulators and would be relatively easy to implement on this Arduino, but we have not written that, ...yet.

Cant wait to See the wiring schematic! Great Job!!!
nwlaurie1 year ago
Wow! ... just WOW!
TheZuke!1 year ago
I don't see the clear domes listed, where/what did they come from?
ST-Geotronics (author)  TheZuke!1 year ago
You're right, my bad... I forgot to list them.
They are 2 Liter soda bottle injection molded preform tubes cut to the desired length.

test tubes with screw cap 22mm x 25mm x 140mm 01.jpg
Great ible, especially for a first! Can you provide any source info for these injection molded tubes?

Can't wait to attempt my own Enigma. Thanks!
ST-Geotronics (author)  gscsderby1 year ago
Thank You gscsderby for the positive feedback.
We bought our Preform Test tubes from Science Bob:
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