Methods of Designing Electronic Equipment

Monoblock design method - the equipment circuit is not broken down into separate functional units, but is realized as a single integral structure on one mounting base.

Module design method - a feature of building technical systems that consists in subordinating their dimensions to a design module and (or) in providing the ability to assemble a wide variety of complex non-standard technical systems with widely differing characteristics from a small, economically justified, number of types and standard sizes of identical primary (standard or unified) common module-elements.

Monoblock design method

Factors determining the choice of the monoblock method:

• - the equipment is for single use, has a limited service life and is intended for long-term storage;
• - the equipment requires no maintenance;
• - the shape of the installation site of the equipment differs from rectangular, and using modules of any BNK (basic bearing-structure) system would cause a large disintegration coefficient;
• - the equipment implements a small number of functions, making it impractical to break the circuit down into functional units;
• - small overall dimensions are expected;
• - the equipment is to be manufactured in small quantities;
• - the equipment is non-repairable and is designed for a short service life

Monoblock design method

Advantages:

• Low design costs (in terms of time and labor intensity).
• Minimal dimensions and weight compared with modular methods.

Disadvantages:

• Requires highly qualified developers.
• Low level of automation of assembly and installation work.
• Using miniature components requires highly qualified assembly workers.
• Relatively high costs for adjustment and inspection.

Basic module design methods

The functional-module method consists in creating equipment based on a catalog of function-standardized modules (design based on a standardized parametric range of modules).

The functional-unit method is based on dividing the entire electrical circuit into functionally complete units and using unified structures of the 1st structural level of the selected (or specified in the technical specification) BNK system.

In the block-module method, the equipment layout is assembled from large modules produced by various companies in the form of conversion units, memory units, power-supply units, etc.

In the functional-block method, functionally complete devices based on original circuits not found in block-module catalogs are implemented either as complete block-module structures using the selected BNK system, or in an original design consisting of a number of functional modules combined into a single structure - a block.

Main trends in the development of on-board electronic equipment affecting its design

2. Growth in equipment complexity and packing density.

3. Reduction in the relative dimensions of active elements and the energy level of signals.

4. Growth in the specific power dissipated by active elements.

LAYOUT OF ELECTRONIC EQUIPMENT UNITS

Layout is the process of arranging component modules, electronic components and parts of electronic equipment on a plane or in space, determining their basic geometric shapes and dimensions.

The following must be taken into account:

• requirements for optimal functional connections between modules;
• their stability and steadiness;
• strength and rigidity requirements; noise immunity and normal thermal conditions;
• manufacturability requirements;
• ergonomics requirements;
• convenience of operation and repair.

Purpose of bearing structures

A bearing structure (BS) is intended for placing, arranging and interconnecting electronic components and other constituent parts of a product in order to ensure its stable operation and protection from the effects of unfavorable operating conditions.

Diagram of structural hierarchy

Appearance of structural modules

Structural hierarchy of electronic-equipment modules

An electronic cabinet (rack, cabinet stand, console) is intended for housing radio-electronic systems and complexes. A functionally complete electronic cabinet is built on the basis of a third-level basic bearing structure (BNK-3) and possesses structural interchangeability.

An electronic frame (rack, cage) is intended for housing electronic devices. A functionally complete electronic unit is built on the basis of BNK-2 and possesses structural interchangeability

An electronic cell is intended for housing radio-electronic units. A functionally complete electronic cell (board) is built on the basis of BNK-1 and possesses structural interchangeability.

An IC (microassembly, microcircuit) is a functionally and structurally complete electronic device, dimensionally coordinated with BNK-1 and possessing structural interchangeability.

In addition to the requirements determined by their purpose, bearing structures must:

• meet ergonomic and technical-aesthetic requirements;
• meet manufacturability requirements;
• be legally protectable, i.e. possess patent clearance;
• have minimal weight and overall dimensions while maintaining the specified strength and operational-stability parameters;
• meet standardization requirements.

Sequence of decision-making on structural options for the modular layout of instruments and units:

• Stage 1 - compiling a list of structural elements of the instrument or unit.
• Stage 2 - placement of input and output connectors.
• Stage 3 - selecting a variant of the bearing elements of the structure for the modules.
• Stage 4 - determining the side (direction) of access to the modules (placement method) and the position of the backplane.

1 - frame; 2 - front panel; 3 - mounting panel; 4 - electrical connector; 5 - cell.

Layout options for plug-in-construction electronic-equipment units

1 - housing; 2 - cassette; 3 - swung-out cassette; 4 - bearing structure

Layout options for cassette-construction electronic-equipment units