EGAFT Electronic Guitar Audio Frequency Tuner Eric Nelson & Peter Sulcs September 23, 2003.
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Transcript of EGAFT Electronic Guitar Audio Frequency Tuner Eric Nelson & Peter Sulcs September 23, 2003.
Project ObjectivesProject Objectives
Design and build a device that will automatically tune a guitar
Once setup, it operates hands-free
SpecificationsSpecifications
ResolutionThe tuner will know the strings’
frequencies to +/- 2 cents or +/- 0.12%Accuracy
A tuned guitar’s strings will tested for accuracyagainst a store-bought tuner.
StrummerStrummerEasily attaches to
guitar with suction cups
Stepper motor belt drive
Plucks one stringMutes all other
strings
Strummer – Pick ShuttleStrummer – Pick Shuttle
Reliable feedback through micro switches
StableHigh precision: .022”
per Step
Strummer - Back RailStrummer - Back Rail
Stabilizes pick shuttleSupports the damper wireLocation of shuttle travel end stops
Peg Tuner ConfigurationPeg Tuner Configuration
Servos are positioned to fit guitarRubberized Aluminum plates bolt togetherStraps attach over guitar headstock
Peg TunerPeg Tuner
Controlled by modified servo motorsUses special MUX (dubbed SpMUX)
EN S2 S1 S0 Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y00 0 0 0 W W W W W W W X0 0 0 1 W W W W W W X W0 0 1 0 W W W W W X W W0 0 1 1 W W W W X W W W0 1 0 0 W W W X W W W W0 1 0 1 W W X W W W W W0 1 1 0 W X W W W W W W0 1 1 1 X W W W W W W W1 d d d W W W W W W W W
Frequency AnalyzerFrequency Analyzer
Electric guitars have an output jackA sound wave of a given frequency
is a nice sine wave
Frequency AnalyzerFrequency Analyzer
A nice sine wave can be convertedto a nicer square wave with a TTL-compatible comparator
Frequency AnalyzerFrequency Analyzer
The HCS12 can calculate the timebetween edges using it’s timer
This is the string’s periodBut is the HCS12’s timer fast enough
to give adequate precision?
Frequency AnalyzerFrequency Analyzer
The reading is skewed when the inputand timer are not synchronized
Frequency AnalyzerFrequency Analyzer
CLK
2string
measuredstring, f
fΔf
fCLK = 250 kHz
fstring Error (Hz) Error (Cents)
500 1 3.46
200 0.16 1.38100 0.04 0.69
Frequency AnalyzerFrequency Analyzer
TCLK = 100kHz
Periods fstring Error (Hz) Cents Periods fstring Error (Hz) Cents
1 2000 40 34.28 11 2000 3.64 3.142 2000 20 17.23 12 2000 3.33 2.883 2000 13.33 11.50 13 2000 3.08 2.664 2000 10.00 8.63 14 2000 2.86 2.475 2000 8.00 6.91 15 2000 2.67 2.316 2000 6.67 5.76 16 2000 2.50 2.167 2000 5.71 4.94 17 2000 2.35 2.048 2000 5.00 4.32 18 2000 2.22 1.929 2000 4.44 3.84 19 2000 2.11 1.8210 2000 4.00 3.46 20 2000 2.00 1.73
CLK
2string
measuredstring, f * Periods
fΔf
Frequency AnalyzerFrequency Analyzer
Easy! Now, just
hook up the output to the guitar jackAdmire the perfect sine wavesit backrelax
Electrical PlanElectrical Plan
Completed workResearched ideas for Frequency AnalyzerMade 5 Servos ConsistentBuilt 1 Circuit for Frequency AnalyzerBought all partsWrote PAL SpMUX code
Electrical PlanElectrical Plan
Work to do:Program SpMUXBuild rest of Frequency Analyzer circuitsWrite code for each subsystemInterface everythingTest everything
Mechanical PlanMechanical Plan
Work to do:Build StrummerBuild Peg TunerInterface everythingTest everything
Test PlanTest Plan
Unit testing is most important!Integration testing will happen between
First between Peg Tuner and Frequency AnalyzerThen Peg Tuner/Frequency Analyzer combo. With
StrummerThe last two weeks before project is due
are reserved for verification testing.
Power ConsumptionPower Consumption
Device Max Current Typical Current
Servo Motors (6) 200mA (Full Load) 80mA (Slow Speed)10mA (off)
Stepper Motor 1.2A 0.55A (Moving)0A (Off)
Stepper Driver ON – 84mAOFF – 24mA
ON – 32mAOFF – 18mA
Power ConsumptionPower Consumption
Device Max Current Typical Current
HCS12 100mA 100mA
Op-amps (19) 2.8mA 1.4mA
Comparators (8) 4mA 2.5mA
PAL 155mA 50mA
Power ConsumptionPower Consumption
Steady State Current – <500mAServos 60mA Stepper 0AStepper Driver 24mAHC12 & PAL 255mASignal Conditioning 112mA
Power ConsumptionPower Consumption
Peg Tuner In-Action Current – <700mAServos 250mA Stepper 0mAStepper Driver 24mAHC12 & PAL 255mASignal Conditioning 112mA
Power ConsumptionPower Consumption
Strummer In-Action Current – <1100mAServos 60mA Stepper 550mAStepper Driver 84mAHC12 & PAL 255mASignal Conditioning 102mA
Power ConsumptionPower Consumption
‘D’ Battery lasts 18,900 mA-Hours Source: Energizer.com
Maximum Life – 36 hoursMinimum Life – 17 hours
System Cost - ElecticalSystem Cost - ElecticalPart Quantity Retail Price
(ea.)
HCS12 1 $150
LM393 Comparators 4 $1
L293D Stepper Driver 1 $2
MAX4239 Op-amps 19 $0.60
Micro Switches 4 $0.26
System Cost - MechanicalSystem Cost - MechanicalPart Quantity Retail Price
(ea.)
Servos 6 $10
Stepper Motor 1 $3
Belts/Pulleys/Suctions cups - $24.68
Raw Material (Rubber sheeting, Aluminum)
- $20
Hardware (Bolts, Screws) - $30