Nuts and Volts - January 2008

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

²³CAN_TX ²⁴CAN_RX

¹MCLR/Vpp ²³RA0 ₄_{RA1 5 RA2 6 RA3 7 RA4 RA5}¹¹¹²^{RC0 13 RC}¹⁴^{RC2 15 RC3 16 RC4 17 RC5}₁₈RC6/TX _RC7/RX

OSC2 ¹⁰GND ⁸_{GND 19}

OSC1 ⁹

VCC ²⁰

PGD/RB7 ²⁸_{PGC/RB6 27 RB5 26 RB4 25 RB1 22 RB0 21}

.1uF

UDK2559

⁴⁵GND ENABLE ¹⁴₁₂_{GND 13 GND GND}

⁹₁₀IN1 ₅_{IN2 16 IN3 IN4}

¹¹VCC

+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 _K7OUT1 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.