THE DESIGN CYCLE
well rooted in theory and high on
implementation. With that, the
Redstone Rocket and the Saturn Launch
Vehicle are shown working together in a
real-world application in Photo 3.
What we have just done is to
assemble simple circuitry driven by PIC
microcontroller I/O pins that perform
very useful tasks. Each of the electronic
switch components are controlled by a
logical state of high or low, which
emanates from a PIC microcontroller I/O
pin. The results of this simple binary pattern include spinning motors, energizing
solenoid valves, and switching relay contacts which, in turn, play an important
role in the overall system mission. I think
that you will agree that this stuff is easy.
There is no rule that useful electronic
devices have to be complicated.
PIC18F2685
23 CAN_TX
24 CAN_RX
1 MCLR/Vpp
23 RA0 4 RA1 5 RA2 6 RA3 7 RA4 RA5
11 12 RC0 13 RC1 4 RC2 15 RC3 16 RC4 17 RC5 18 RC6/TX RC7/RX
OSC2 10
GND 8 GND 19
OSC1 9
VCC 20
PGD/RB7 28 PGC/RB6 27 RB5 26 RB4 25 RB1 22 RB0 21
.1uF
UDK2559
45 GND ENABLE 14 12 GND 13 GND GND
9 10 IN1 5 IN2 16 IN3 IN4
11 VCC
+5VDC
BASIC I/O CONDENSED
.1uF
Suppose you need a quartet of
ZVN4306G-like control circuits to control some low-voltage devices (less than
60V) that draw no more than 700 mA
each when active. There’s nothing wrong
with lining up four of the ZVN4306G
circuits depicted in Schematic 2 on a
piece of PCB real estate. However, each
ZVN4306G buffer is made up of a
minimum of five components. Can I
show you how you can assemble four
ZVN4306G-like buffers for this application with only four components?
Behold Schematic 3 and the
Allegro MicroSystems UDK2559. The
four components that make up our
electronic switch are the UDK2559, the
UDK2559 power supply bypass capacitor, and the UDK2559 bulk device
source voltage bypass capacitor pair.
I’ve purposely left the PIC’s particulars out of Schematic 3 as the UDK2559
connection specifics are the important
part of the schematic contents.
Logically, the UDK2559 is a collection
of four sets of AND gates feeding four
high-current bipolar outputs that can
each sink up to 700 mA in their “on”
state. Schematic 3 shows all of the
UDK2559 drivers being linked up to the
same bulk device source voltage of + 12
VDC. If you need to use differing bulk
device source voltages, you can divide
the four UDK2559 drivers into pairs and
provide one of your bulk device source
K2 K7
OUT1 8 OUT2 6 OUT3 3 OUT4 1
220uF
+
+12VDC
LED
330
+12V SOLENOID
LED
330
1
2
3
4
5
NO
COM
NC
■ SCHEMATIC 3. Yes. The PIC has been
neglected here. The idea is to show you
how to hook up the UDK2559. If you’re
PIC challenged, just look back at past
Design Cycle columns to get a grasp
on standard PIC configurations.
DC MOTOR
LAMP
January 2008 85