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Wooden case by Peter Meijer, Germany
Peter Meijer from Germany, has sent us pictures of the wooden box that he created for his Enigma-E. But what's more, he found a clever way to use the morse code sounder, without added an extra buzzer and he's come up with an alternative circuit to feed the Enigma-E, for those who'd like to give it a try.

Peter used the back of on old cupboard (8 mm) for the case, and some new 4 mm plywood for the top cover, which is not as dark as the rest.

The first image shows the finished box without the electronics and you can clearly see the black battery holder, fitted inside the case, and two 3.5 mm stereo sockets for the serial ports. One socket is wired as suggested elsewhere on this website and connects to the PC. The other 3.5 mm socket is used to connect an LCD terminal that is used to display the decrypted text. As the LCD terminal only needs the TX line, the other wire (normally used to carry the RX signal) is tied to +5V to provide power for the LCD terminal.
Using only 2 AA type batteries
Rather than using a standard 9V block battery, which won't last very long if the Enigma-E is used extensively, Peter has used 2 standard AA size batteries, e.g. Alkaline, NiCd (chargable) or NiMH. As the two batteries together will produce no more than 3V, but the Enigma-E requires at least 5V to operate, so Peter had to come up with a solution and designed a small but cunning circuit.

The circuit is based on the LT1073 Switching Regulator from Linear Technologies, which can deliver up to 100 mA in this circuit, more than sufficient for the Enigma-E. The PCB with this circuit is fitted to the bottom of the case, as can be seen in the leftmost picture above. The black tube to the right of the small PCB is the battery holder for two AA cells, which can be accessed from the rear of the case, as can been seen in the rightmost picture.
Older versions of the Enigma-E board
If you want to use this circuit with your Enigma-E, some components have to be removed from the Enigma-E PCB. The following components should be removed and will not be used elsewhere: C8, C15-C17, C23, C24, BRIDG1, D33, FUSE1, IC6. The mounting hole of the 78M05 (IC6) is now used to accomodate the power switch, as can be seen in this picture.

 View the circuit diagram
 Datasheet of the LT1073 Switching Regulator
Newer versions of the Enigma-E
Please note that on later versions of the Enigma-E PCB, some components, and hence the numbering of the ICs, have been changed. In his description, Peter is referring to the power regulator (7805) that is located in the top left corner of the main board. On later boards it is called IC9 (78L05). It has no mounting hole and looks just like a normal transistor. The pin-out of this IC, when looking at the text, is OUT, GND, IN.

Some words about the circuit: The inductor is not critical. It should be in the range between 50 and 100 µH (toroid or pod core with low resistance). The diode D1 should be a schottky type, D2 in uncritical (universal type). The two 100nF capacitors should be ceramic capacitors.
Please note that the modifications described on this page are suggested by Peter Meijer and not necessarily by the Enigma-E development team. Any modifications made to the Enigma-E are entirely at your own risc.
Using the morse sounder without an extra buzzer
If you want to use your Enigma-E to produce morse code, the manual suggests to add an extra buzzer, similar to the one supplied with the kit. Peter, however, has used the existing buzzer to generate the morse code. This is done by using a universal NPN transistor (Tr1 in his circuit diagram, e.g. a BC547) which works as a Wired-OR with transistor T7 on the Enigma-E board.   

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Crypto Museum. Last changed: Monday, 11 April 2011 - 10:43 CET.
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