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Rowan Hall 238A beard@rowan.edu http://rowan.jkbeard.com April 09, 2006 Sophomore Clinic ENGR 01-202 5, CRN 20686 Integrating the PIC and the H- Bridge James K. Beard, Ph.D.
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Slide 2 Sophomore Clinic II April 09, 2006 Topics Driving the MOSFETs from 5 Volts The pin out of the H-bridge Connecting the H-bridge and the PIC board
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Slide 3 Sophomore Clinic II April 09, 2006 MOSFETs in Switching Switching properties Off When they’re off, they’re off Gate-source voltage must be below threshold voltage On When they’re on, the drain-source resistance is very, very low The achieved on resistance is a function of the drive voltage Drive must be much higher than the threshold voltage 5 Volts drive provides sufficient drive
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Slide 4 Sophomore Clinic II April 09, 2006 On V-I Characteristics N-ChannelP-Channel
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Slide 5 Sophomore Clinic II April 09, 2006 Conclusion Typical characteristics from the IRC data sheets N-channel is IRFZ24N P-channel is IRF9Z24NPbF Data sheet shows N-channel on resistance of 1/8 Ohm P-channel on resistance of 2/5 Ohm Both limit current to about 2.5 A Good to go for Sophomore Clinic Project motor drives A good choice for magnet drive – switch directly from the PIC
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Slide 6 Sophomore Clinic II April 09, 2006 Pin-Out of the H-Bridge Board Power connector +5 Volts, ground from the rails Power to the motors comes from here Connectors for the motors Three redundant ground connections Eight lines to the PIC board
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Slide 7 Sophomore Clinic II April 09, 2006 1 3 5 7 8 6 4 2 ABC D G5 G2G2 G4G4 G1G1 G3G3 G6G6 G8G8 G5G5 G7G7 G2G2 G1G1 G3G3 G4G4 V DD H 12 H 34 H 78 H 56 H 34 H 12
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Slide 8 Sophomore Clinic II April 09, 2006 The H-Bridge Drive The MOSFETs are complementary – The P- channel is driven by the reverse polarity signal to the gate +5 Volts is OFF Ground is ON We want to drive them form the PIC hardware, not the software Solution We use the PWM output of the PIC We use the motor direction toggle from the PIC We drive the H-bridge with hardware using these signals
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Slide 9 Sophomore Clinic II April 09, 2006 Interface Circuitry G2G2 G4G4 G1G1 G3G3 G6G6 G8G8 G5G5 G7G7 Toggle PWM G4G4 G1G1 G2G2 G3G3 From PIC To H-Bridge
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Slide 10 Sophomore Clinic II April 09, 2006 The Chips CMOS to provide full 5 Volt swing on logic one 4000 series to allow use in other circuits up to 15 Volts Two-chip solution for both motors CD4011 or MC14011 quad NAND CD4069 or MC14069 hex inverter
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Slide 11 Sophomore Clinic II April 09, 2006 Chip Pin-Outs
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Slide 12 Sophomore Clinic II April 09, 2006 Wiring the Interface Logic: G2 G4 G1 G3 G6 G8 G5 G7 C0C1C2C3C4......... PIN 14: HOOK TO +5VDC PIN 7: HOOK TO GND TAKE YOUR TIME – TRIPLE CHECK EVERY CONNECTION! Errors here can cause permanent damage to the uC board and/or H-Bridge! CD4011 17 14 23456 1312111098 On both ICs: CD4069 1234567 141312111098
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Slide 13 Sophomore Clinic II April 09, 2006 The Interface Logic Wired
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Slide 14 Sophomore Clinic II April 09, 2006 Electromagnet Drive Circuit D SG Electromagnet Output From PIC +5 Volts From Rail Or H-Bridge IRFZ24N N-Channel MOSFET (same one that the H-bridge uses) G S D
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