So, you want to make an MR compatible button box.

Here are the simple instructions. If you do not feel that you understand these, please take the time to find someone who does.

The system is set up now so that you can easily create devices that emulate numeric key-presses to USB ports. All you will need to do is to place the switch array you like in a box, and to wire an appropriate cable. The interface box can handle up to nine separate switches and will send out nine different numeric codes.

Rules:

• You must use shielded cable.
• You must not run any signals through the shield.
• The wire shield should connect to the DB-25 metal case.
• You must have a fully insulated external box.
• You must avoid magnetic components, such as steel enclosures.
• You must have your device checked out by me, or an MR savvy individual, prior to first use. Ideally, this checkout should take place at the design stage as well.

It should be obvious that you do not need to have 9 buttons. If you use less than 9, only connect the wires you need to either end of the cable.

One way to do this will be to place your buttons into an aluminum box, and the place that inside of a plastic box. An alternative is to mount everything in a plastic box, and to line the interior with copper foil tape. Make certain that the box shield is connected to the cable shield. Do Not run your return currents through the shield.

The following is a simple wiring diagram:

In the future, it is my intention to supply +12V, -12V and +5V isolated power through the 25 pin cable. For the moment, do not connect anything to pin 10 or to any of pins 12 through 25.

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This page is maintained by Mark Cohen [updated 12.11.03]