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Enhancing your Enigma-E
We've just finished the wooden boxes for our own Enigma-E units and have made some nice enhancements that we'd like to share with you. First of all, we've added some chargeable batteries to the unit, plus a proper charge circuit. Next we found a place to put the power socket, the power switch and the socket for the serial port. One of the most significant improvements we've made so far is the addition of white LEDs on the lamp panel though...
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Using chargeable batteries
If you want to carry your Enigma-E kit around and use it in every location, you might want to add chargeable batteries to it. You can use standard AA-size NiCd batteries, which are relatively cheap these days. 6 of such AA-size cells will give you about 7.2V (1.2V each), which is enough to power your Enigma-E for days.

When using chargeable batteries, it's important to use a proper charge circuit. Just applying a voltage isn't suitable and is likely to damage your battery cells. A proper charge circuit is given in the drawing below. It supplies a constant current of 60mA to the batteries, which is 10% of the maximum current the battery can deliver without damaging the cell.

This curcuit required only a few components and can easily be built on a small piece of vero board. You may even be able to fit the batteries and the charge circuit in a small case which can be mounted inside the Enigma-E box.

For this circuit, we've made use of the rectifier that is present on the Enigma-E PCB (BRIDG1). The power from your adapter first goes to the rectifier on the Enigma-E board (AC1 and AC2). The output from the rectifier (N) goes to the charge circuit. The output of the charge circuit goes to the Enigma-E circuitry (C). The circuit is in effect a constant current source, the base of which is formed by the transistor TR1 and the yellow LED D1. Please note that we've used an LED to create the correct reference voltage. The Zener diode D2 is used as a protection against overcharging. F1 can be an ordinary fuse, but it's better to use a self-restoring multifuse instead. Please note that it is important to use a 100mA fuse as close to the battery cells as possible, despite the fact that the Enigma-E PCB already contains a fuse. After all, you are using wires to connect to the switch and the PCB and if you make a mistake you will need the fuse as a protection.
Fitting the socket for the power adapter
The kit is supplied with a socket to allow you to connect an external power adapter. Many people have asked us what the best place would be to fit the socket. Of course, if you've built a wooden box around the unit, you could drill a hole in it and fit the socket. That would however destroy the authenticity of the case, now wouldn't it?
After a bit of trying and probing, we found that the ideal place to put the power socket, is on the Steckerbrett. Both at the left and at the right of the Steckerboard sockets there is enough room to fit a socket. We've mounted it on the right hand side of the Steckerbrett as you can see in this picture. Be careful when drilling a hole in the Steckerbrett PCB as you might otherwise damage the tracks on the rear side. If you do, don't worry, you can easily repair them with a couple of wires.

As we wanted to be able to see that our unit was on, we've added a bright blue LED to this panel as well. Fir this, we've drilled very small hole in the YiG logo, as you can see in the picture.
Click for a larger view

Below are two images showing the rear of the Steckerbrett PCB. You can clearly see how the power socket and the blue LED have been mounted. Please note the series resistor (used between the power source and the LED) and a protection diode (1N4148) connected anti-parallel over the LED. The latter is used to protect the LED against reverse current in case you are using an AC power adapter.
The power socket mounted on the Steckerbrett Fitting the diode and the resistor Wiring of the power connector

Fitting the power switch
Whilst on the subject of modifying the Enigma-E, we found a good place to mount a power switch. For this we've used the centre hole of the Steckerbrett. This hole is intended as a mounting hole when using the PCB in a horizontal position. However, in the wooden case, the Steckerbrett is mounted straight up and the centre hole isn't used. Find a suitable tumble switch and solder or glue it to the rear of the PCB.

In the images on the right you'll see a tumble switch glued to the rear of the Steckerbrett, using two-component glue. The hole had to be enlarged slightly.

Fitting the socket for the serial port
The Enigma-E has a fully functional serial port that can be used to connect the machine to, say, a PC (using a terminal program) or another Enigma-E. Normally, a 9-way sub-D connector is used for this purpose, but that may be too large to fit to the Enigma-E.
One user suggested to use a 3.5 mm stereo mini jack for this purpose, which fits nicely on the left hand side of the Steckerbrett. As you can see in the picture, we've tried this too and we're very happy with it.

Before drilling the hole somewhere in the Steckerbrett, please ensure that you are not cutting any tracks of the PCB. The area indicated in the picture, is free from tracks in all versions of the PCB. Also check the quality of the jack socket before buying one. There are many variants of this socket, but the best results are obtained with the slightly more expensive ones.

The best way of wiring the 3.5 mm stereo jack is shown in the drawing below. If we all use the same wiring, all Enigma-E machines can be connected together. Use three-way cable to connect the serial port: 2 wires plus a shield.
   One wire is used for transmission (TX) and one for reception (RX). The shield is connected to the Ground connection if the Enigma-E. We've used the tip for TX, the ring for RX and the ground for the cable shield. You may then use a cross cable to connect two Enigma-E machines together.
The power switch at the centre of the Steckerbrett Power switch seen from the rear Fitting a socket for the serial port

Using white LEDs on the lamp panel
Although white LEDs are much more expensive than the usual yellow, green or red one, we couldn't resist to try them out on the Enigma-E kit. After an extensive search, we've found some low-power, high-brightness ones which work well on the Enigma-E. Follow the link below to read more about the use of white LEDs. Partnumber and datasheet are available. Update: All Enigma-E kits with a serial number of 503 or higher are now supplied with high-brightness yellow LEDs, so for these users there is no need to swap the current LEDs for white ones.

 Read more about using white LEDs

Further information

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Crypto Museum. Last changed: Sunday, 18 March 2012 - 08:50 CET.
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