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Sophomore Clinic
ENGR 01-202 5, CRN 20686
Integrating the PIC and the HBridge
James K. Beard, Ph.D.
Rowan Hall 238A
[email protected]
http://rowan.jkbeard.com
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
April 09, 2006
Sophomore Clinic II
Slide 2
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
April 09, 2006
Sophomore Clinic II
Slide 3
On V-I Characteristics
April 09, 2006
N-Channel
Sophomore Clinic II
P-Channel
Slide 4
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
April 09, 2006
Sophomore Clinic II
Slide 5
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

April 09, 2006
Sophomore Clinic II
Slide 6
1
3
5
7
6
8
VDD
H12
2
A B C D
G 5
G1
4
H78
H56
H34
H12
G3
H34
G 2 G 4 G 1 G 3 G 6 G 8 G5 G 7
G2
April 09, 2006
G4
Sophomore Clinic II
Slide 7
The H-Bridge Drive

The MOSFETs are complementary – The Pchannel 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
 We
 We
use the PWM output of the PIC
use the motor direction toggle from the PIC
drive the H-bridge with hardware using these
signals
April 09, 2006
Sophomore Clinic II
Slide 8
Interface Circuitry
From PIC
Toggle
G 2 G4 G1 G3 G6 G 8 G 5 G7
PWM
G1
G4
To H-Bridge
G3
G2
April 09, 2006
Sophomore Clinic II
Slide 9
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
April 09, 2006
Sophomore Clinic II
Slide 10
Chip Pin-Outs
April 09, 2006
Sophomore Clinic II
Slide 11
Wiring the Interface Logic:
On both ICs:
PIN 14: HOOK TO +5VDC
PIN 7: HOOK TO GND
G2
G4
G1
14
13
12
11
10
9
8
14
13
CD4011
1
2
3
4
5
12
11
10
9
8
G6
CD4069
6
7
1
2
3
4
5
G3
6
7
G8
G5
G7
C0 C1 C2 C3 C4 ... ... ...
TAKE YOUR TIME – TRIPLE CHECK EVERY CONNECTION!
Errors here can cause permanent damage to the uC board and/or H-Bridge!
April 09, 2006
Sophomore Clinic II
Slide 12
The Interface Logic Wired
April 09, 2006
Sophomore Clinic II
Slide 13
Electromagnet Drive Circuit
Electromagnet
G D S
Output
From PIC
April 09, 2006
D
G
220 
+5 Volts
From Rail
Or H-Bridge
IRFZ24N
S N-Channel
MOSFET (same one that
the H-bridge uses)
Sophomore Clinic II
Slide 14