Conceptual DesignIn EE, conceptual designs are usuallyexpressed using block diagrams.Conceptual design is individual activity.It’s the phase of the design processwhere individual’s creativity is key.Generating as many design conceptsas possible is a good practice.ECGR 2252Mehdi MiriECE Dept.UNC CharlotteConceptual Design - continuedA formal process for selection of the “best” conceptual design of the product is usually necessary (see Appendix B of textbook: “AHP”).Conceptual design selection is a team activity-”brain storming”.Following conceptual design selection, product design spec’s are revised.Design changes beyond this phase are usually costly.ECGR 2252Mehdi MiriECE Dept.UNC CharlotteConceptual Design ExampleNeed: Wireless remote-controlled on/off switchfor 240V, 1KW ac inductive load.Concept1: Sound SwitchECGR 2252Mehdi MiriECE Dept.UNC CharlotteVoltage Amplifier +BPFSignal ConditionerFVCThreshold ComparatorToggle F/FCurrent AmplifierSPST AC Power SW240V, 1KW Inductive LoadMicVthreshConceptual Design Example – cont.Concept 2: IR Remote Controller w/ backup SWReceiver/Load Module:ECGR 2252Mehdi MiriECE Dept.UNC CharlotteOpticalFilterInfraredDetectorHigh-GainAmplifierBandpassFilterIr BurstDemodulatorEdge-TriggeredToggle Flip-FlopCurrentAmplifierSPDT ACPower SWAC Load3-WayMechanicalBackup SWIr ReceiverModulatedIr BurstConceptual Design – Example continuedPushbutton Remote Control Unit:ECGR 2252Mehdi MiriECE Dept.UNC CharlotteIr Burst ModulatorCurrent AmplifierIr Burst TransmitterDCPushbuttonConceptual Design (Level 2) Burst Modulator:ECGR 2252Mehdi MiriECE Dept.UNC CharlotteAstable (f = burst freq)DCA Decision MatrixAlternative 1Alternative 2…..Alternative nCriteria 111121nCriteria 221222nCriteria mm1m2mnScore12mmiiiS111miiiS122miininS11. Determine the selection criteria.2. Determine the criteria weightings.3. Identify and rate alternatives relative to the criteria. 4. Compute scores for the alternatives.5. Review the decision.Steps of AHPDecision = select a design conceptStep 1: Determine Criteria Cost Convenience of operation Reliability of operation. Compactness. Power efficiency. Safety. Noise immunity. Effectiveness in meeting target market. Innovative features.Apply AHP:• Need to select weightings of criteria (relative importance)• Number of ways – one is pairwise comparison• Compare each criterion to all others with following scale:1 = equal, 3 = moderate, 5 = strong, 7 = very strong, 9 = extreme.Step 2: Select WeightingsStep 2 (paired comparison)CostConvenienceReliabilityNoise ImmunityCost11/31/71/5Convenience311/51/3Reliability7513Noise Immunity531/31Step 2: paired comparison with reduced biasCriteriaCostConvenienceReliabilityNoise ImmunityGeometric MeansWeightsCost11/31/71/5Convenience311/51/3Reliability7513Noise Immunity531/31Alternatives are determined to be:• Sound switch (Concept 1)• IR remote-controlled (Concept 2)Step 3: Identify Alternatives & Rate• Estimate cost of parts needed:11 = 1, 12= 0.82• Normalize11 = 0.55, 12 = 0.45Rate relative to Costcostmin{cost}• This is subjective => need to quantify subjective opinion• Use paired comparison to do so, with same scale as beforeRate relative to ConvenienceConcept 1Concept 2Convenience RatingConcept 111/30.25Concept 2310.75• This is subjective => need to quantify subjective opinion• Use paired comparison to do so, with same scale as beforeRate relative to ReliabilityConcept 1Concept 2Reliability RatingConcept 1130.75Concept 21/310.25• This is subjective => need to quantify subjective opinion• Use paired comparison to do so, with same scale as beforeRate relative to Noise ImmunityConcept 1Concept 2Noise Immunity RatingConcept 111/70.125Concept 2710.875Concept Selection Decision MatrixConcept 1 (Sound Switch)Concept 2 (IR Remote)Criterion 1(Cost)0.050.550.45Criterion 2 (Convenience)0.120.250.75Criterion 3 (Reliability)0.560.750.25Criterion 4 (Noise