Introduction
Building a Simpit is no small task no matter which way you look at it, especially if you're trying to correctly emulate a real cockpit. Having gotten the physical cockpit construction sorted, you're left with the problem of making all those fancy switches you've installed control your favourite simulator program. The KE72 keyboard encoder from Hagstrom Electronics can make life very much easier for you and at $119.95 (Jan 2002) it won't break the bank either! 

The KE72 supports 72 individual switch inputs activated using just about any form of switch including simple push-buttons or regular toggle switches. Each input on the KE72 is programmable using a simple configuration file, and the really smart thing is that each switch input can be programmed to issue one or more keystrokes when the switch contacts are closed AND/OR when they are opened. This becomes really useful where you need to send different keystrokes for switch on and switch off. For example, supposing your simulator uses lower case 'g' for gear down, and upper case 'G' for gear up - the KE72 can easily be programmed to issue the 'g' when the switch is closed, and 'G' when the switch is opened. 

The fun doesn't end here though... the KE72 can also be programmed to issue sequences of keystrokes including those normally awkward keys like CTRL, SHIFT and ALT. There is a limit of 32 keystrokes when a switch is closed, and 16 when it is opened. 

The KE72 has been cunningly designed so that it will fit into a standard PCI slot in your PC (though it uses none of the PCI connections) - this is purely for convenience and the board may be mounted externally. The end connectors on the KE72 are for links to the PC's keyboard port, to an external keyboard, RS232 connector and to a trackball (KE72-T only). The 72 input connections are made by means of two 40-way IDC connectors on the board itself. 
 
 

Wiring the KE72
This is made easier using the optional IOX36 breakout board which provides simple screw terminals rather than the default IDC headers on the KE72 card itself. Each switch must be wired to one of the 72 inputs, and to the common ground connection. A simple connection using a changeover toggle switch is shown below. The green wire is the common, and each of the orange wires goes to a KE72 input. 
 
 

You can of course dispense with the breakout board and make your own. Since my own simpit has to be modular, I elected to make a connection panel which simply converts from the 2 IDC connectors on the KE72 to a set of 9 25-way D-type sockets as shown below. 
 
 

Programming the KE72
This could not be easier, a simple configuration file is created and downloaded to an EEPROM on the KE72 either through the keyboard port or through the KE72's own RS232 port. The configuration file is in plain text so you can edit it with something as simple as Windows Notepad. Click here to view the sample configuration file supplied with the KE72 which contains useful comments explaining the many features available. A few minutes browsing the example configuration will explain things far better than I could here. 

Q&A
Having spent the last year dabbling with simpits, and with this review in mind, I emailed those friendly folks at Hagstrom with a few questions. With their kind permission here's what they said: 

Q. Can more than one KE72 be connected in series? (understanding that only one can be live during programming via the keyboard interface).

A. It is possible to connect two KE72 units in series. The main consideration here is that the cable (keyboard cable) lengths be kept to a maximum distance of 10 feet total. The problem that arises in longer runs is that voltage is dropped across the cable, and the end unit may not receive proper operating voltage if the connecting cables are too long (allowing more voltage drop). The unit attached directly to the keyboard port could be programmed through that port. The second unit in line can be programmed through the serial port, since that option is available as well. 

Q. How susceptible to electrical noise are the inputs? I've used shielded cable to my cockpit switchgear, but have been concerned about noise from relays activated by the same switches etc.

A. The KE72 inputs are debounce in software to sort out the mechanical debounce associated with switches. This debouncing also provides some protection against noise generated from outside sources. The susceptibility will depend on the cable length from the KE72 header to the end switch connection and heavily on the environment that the unit is being operated in. Shielded cable is a smart way to go if there is a high energy surge, such as a relay, in the adjacent cable bundle. 

Q. Have you any plans to create an encoder with more inputs or to handle analogue-digital control?

A. We are always working on new products based on customer requirements. We have had a number of requests for some type of analog input to be integrated into our devices, so that may be a product in the future. We may also introduce an encoder with more inputs, since that has also been a request. Some options with present products would be to combine, say a KE72 with a KE-USB36. This would give you two different connections (PS2 and USB) with 72 + 36 inputs. Our KE-USB36 (which programs through USB) also has a feature which allows two KE-USB36 devices to be attached to the same PC, but seen as two different USB devices which may be programmed independently. 

Summary:
The KE72 provides a very simple solution to a tricky problem for any simpit builder, and does so at a very reasonable price. Software configuration and wiring are very easy, tech support from Hagstrom can't be faulted and taking power from the keyboard port means one less wall-wart. If I had one criticism at all, it would be an unfair one - there aren't enough inputs! Even with a fairly modest simpit, 72 inputs is soon eaten up - but then at this price, just use two KE72's! 

Accessories:

• IOX36 Breakout Board as shown in Fig 3, this provides simple screw terminals to the many KE72 inputs. You'll need two of these if you want to use all 72 inputs. 
• KE-MM6-mini - Male-Male cable to connect from the PC keyboard port to the KE72. (also needed by KE72-T users to connect to the PS2 mouse port when using the Trackball Interface). 
• KE-TBH3 Cable for connecting to a Happ Controls Trackball. 

Links:

• Hagstrom Electronics - Hagstrom Electronics Homepage. 
• Test Configuration - This is a test configuration file for the KE72 I used to test my switch inputs. It simply outputs strings like 7-ON or 7-OFF which can be very useful while debugging your wiring. 

The Disclaimer:
I have no links with Hagstrom whatsoever other than as a very satisfied customer. My order with them was dispatched very quickly and their technical support people (thanks Dave!) have been not only very quick to respond to my questions - but have provided very helpful responses.