A List to Aid in Writing Specifications

Give your project a name

You'll probably be using this name a lot in the future - If you keep your project name short, it'll save you time! If it's 7 letters long, and unique enough to do a text-search on, you've got a real winner.

Describe the project (Opening Statement)

Describe the market

Estimate the production volume

The types of specification points or clauses

The way to arrange a specification is as a list of bullet points, or clauses. Bullet points have the advantage of being clear and concise. A specification should describe all the required attributes of the project - make a separate, if attached, wish list. When writing a specification it is important to distinguish between required and desired. Think carefully before you state a desire as a requirement - if you specify that the project is to be no larger than a cassette case, be sure that the market really warrants that feature. A specification reads like a list of project features, describing the unit, and will usually include:






Modes of operation

Power Supply




Review the specification to ensure it describes the project clearly and succinctly. The specification should describe the project, as you need it produced. The specification can be followed by a wish list - desirable features or possible extensions. Possible extension might include a connector for I/O expansion.

An example of the distinction between the required and the desirable: The size of an electronic project is frequently described as a requirement when it is more often just desirable that it be as small as possible. The specification is a terse point-by-point document with a brief opening description. It often helps to attach a plain written description of the project, which is more general, and describes the way the project works more from the perspective of how it is used.


Keyboard and Switch inputs

Other switch and relay contact inputs

Opto-isolated inputs - Used to isolate the input circuit from the main electronics

Temperature sensors

Light Sensors

Magnetic Field sensors



Parallel outputs, TTL level

Open collector outputs

High current outputs

Analog outputs


Solid State Relays (SSR's)



Light Emitting Diodes (LED's)

LED displays - LED bar

Lamps - Incandescent

Audible Indicators

Indicators: Displays

LED displays - 7 segment with decimal point

Liquid Crystal Displays (LCD) - 1,2 or 4 lines of characters

LCD: Displays - Graphic type

LCD: Displays - color Graphic type


Modes of operation


Power Supplies

Plug Pack, or wall adaptor - reasonably priced for power up to 10-15W