Vernier Digital Control User Manual

Vernier Digital
Control Unit (DCU)

Order Code DCU-BTD

The DCU is an electronic device that allows on/off control of motors, lamps, LEDs,
buzzers, and other DC electrical components. It works with any Vernier interface
that has at least one DIG port (SensorDAQ, LabPro, and all LabQuest models). The
DCU can be used to create sensor-based projects, such as alarm systems,
temperature-controlled environments, automated scientific instruments, kinetic
sculptures, and smart robots. DCU projects are a great way to introduce STEM,
engineering, electronics, programming, or the mathematics of feedback and control.

Overview

The DCU is a small unit with a circuit board extending from one end. On the side
opposite the circuit board is a short cable, which connects to any DIG port on a
Vernier interface. On the circuit board are a variety of header pins and a detachable
terminal strip connector for connecting electronic devices. There are eight
connections to six digital lines, plus a power and a ground connection.

The circuit board also includes six red LEDs that indicate the status of the six digital
output lines—D1, D2, D3, D4, D5, and D6. There is one green LED labeled EN (for
engaged) that indicates when the DCU is properly connected to the interface. There
is also one blue LED labeled XP (for external power) that indicates that a power
supply is attached. Learn to check the EN and XP LEDs; they can warn you if things
are not set up correctly.

The DCU can be used as a set of six remote-controlled switches. These electronic
switches use transistors to function like mechanical switches. If you connect an
electrical device, such as a motor or lamp, between a DCU output line and a ground
connection, you can control this device by switching the output line on or off.

The basics of digital output control can be taught without complicated programming
by using the DCU. This booklet explains how to use the DCU to create simple
projects using Vernier’s Logger Pro software or National Instrument’s LabVIEW™
software. You can control three digital lines with Logger Pro and all six lines with
LabVIEW. Both Logger Pro and LabVIEW can be used on Windows or Macintosh
computers.

Users wishing to control the DCU with Arduino should refer to the Engineering
section of the Vernier web site, www.vernier.com/engineering/arduino

Users wishing to control the DCU using a LabPro with LabVIEW or with a TI
graphing calculator should refer to the previous version of the DCU manual at
www.vernier.com/files/manuals/dcu-btd_20050425.pdf

Power Source

There are two different ports on the DCU for connecting power supplies. Both are
near the short cable that connects to the interface. A LabQuest Power Supply can be
connected to the smaller port. Alternatively, a LabPro or ULI Power Supply can be
connected to the larger port. A complete list of power sources that can be used with
the DCU is provided below:

 LabQuest Power Supply (order code LQ-PS): 5 V DC, regulated, 1.5 A
 LabPro Power Supply (order code IPS): 6 V DC, regulated, 600 mA
 ULI Power Supply (order code ULI-PS): 9 V, unregulated, 1000 mA
 Battery power supply: one lantern battery or four to eight 1.5 V cells connected in

series. You can use either port for a battery power supply if you follow the
polarity guides in Table 1.

Input Supply Voltage 4–12 V
LabQuest Power Supply 5 V
LabPro Power Supply 6 V
ULI Power Supply 9 V
Polarity LQ-PS 3.5 mm OD Socket (Center Positive)

Output Voltage Set by input supply voltage
Max Output Current per Line 600 mA steady; 1200 mA momentary
Max Overall DCU Current 1800 mA

If power supplies are connected to both ports at the same time, only the power
supply connected to the larger port will be used.

Note: When building projects, you should always keep the power limitations of the
DCU in mind. Never apply more than 12 V DC to the DCU or use AC power
supplies. The total current drawn by your project should not exceed the capability of
your power source.

Table 1 Power specifications

IPS or ULI-PS 5.5 mm OD Socket (Center Negative)

Connecting the DCU to an Interface

1. Connect the DCU to any DIG port on the interface.

2. Connect a power supply to the DCU.

3. Connect the interface to the USB port on the computer.

4. If you are using LabQuest 2 or original LabQuest, make sure it is turned on.

Connecting Devices to the DCU

The DCU provides two easy ways to connect your electronic device: a screw
terminal or header pins.

 To connect to the screw terminal, loosen the screw, insert the lead (wire) into the

hole, and then tighten the screw to secure the lead. The screw terminal is
detachable. Therefore, you can easily connect and disconnect your electronic
device.

 To connect to the header pins, use header connectors or small alligator clips to

attach the leads of your device to the appropriate pins. One row of header pins
connects to the D1–D6 lines while the other row of pins connects to ground, as
shown in Figure 1. This minimizes crossing wires when connecting two-lead
devices such as motors.

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Whichever option you choose to connect your device to the DCU, you must insulate
the metal leads on all components so that they cannot accidentally touch each other.

The DCU also includes a third connection option: a cluster of three pins providing
connections to the power supply, ground, and line D4. This facilitates connection to
many servo motors. Servo motors require pulse width modulation (PWM) digital
output that can only be used with LabVIEW software.

Table 2

Pin DCU line

1 D1
2 D2
3 D3
4 D4
5 D5
6 D6
7 XP
8 GND

Figure 1 DCU output connectors

What can you connect to the DCU outputs?

In general, you can connect any electrical device that runs on DC electricity at a
voltage that matches your power supply. The DCU output voltage can range from 5
to 12 volts, as shown in Table 1. You can find thousands of different 5 to 12 volt
devices at most hobby and electronic stores, such as Mouser, DigiKey, or
Radio Shack.

One common application is using the DCU to turn on an electronic device when a
sensor reading reaches a threshold value. For example, the circuit in Figure 2 shows
a small 5 volt hobby fan connected between the D1 and GND lines of the DCU. If
the temperature reading of a sensor connected to the interface gets too hot, you
would like the fan to automatically turn on just like the air conditioning system in
your home. Conversely, when the temperature cools down, you would like the fan to
turn off. The DCU gives you this on/off control.

shown in Figure 3 of a motor wired between the D1 and D2 lines of the DCU. The
circuit on the left has D1 turned on and D2 turned off, so current will flow from D1
to D2 causing the motor to spin in a clockwise direction. The circuit on the right has
D1 turned off and D2 turned on, so current will flow from D2 to D1 causing the
motor to spin in the opposite direction.

Figure 3 Wiring diagram for running a motor in two directions

Using the DCU with Logger Pro

Logger Pro is Vernier’s data-collection and analysis program. The Logger Pro
Digital Out feature allows you to control up to three output lines of a DCU
connected to the DIG 1 or DIG 2 port of a LabQuest or LabPro. Each of the three
lines can be individually controlled based on user-configured conditional statements.
This allows you to develop projects that turn DC motors, lamps, LEDs, buzzers, and
other DC electrical devices on and off based on sensor readings, time, or calculated
columns.

Note: Logger Pro does not support the SensorDAQ interface. To use the Vernier
SensorDAQ with a DCU, you must use LabVIEW software.

Setting up the DCU in Logger Pro

1. Connect the DCU and at least one other Vernier sensor to the data-collection
interface.

2. Choose Set Up Sensors from the Experiment menu and select your interface.

Figure 2 Wiring diagram for connecting a fan to the DCU

Sometimes you would like to use an electronic device that has the ability to operate
in two different directions. Pairs of DCU lines can be used together to allow you to
switch the polarity or direction of current flow in your device. Consider the circuits

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Figure 4 Logger Pro sensor setup window

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