DXARTS 470

1
DXARTS 470

• Lecture 2 Digital Input

2
Transduction

• The conversion of one form of energy into
  another.
• What is the input / output?
• Use appropriate materials
• Less lt-------gt More

3
Digital Electronics

• On / Off
• High / Low
• Up / Down
• Left / Right
• In / Out

4
Switches

• Normally Open (NO)
• No event waiting for an intervention
• Normally Closed (NC)
• Continuous Events interrupted by external events
• Momentary
• Toggle
• Switches are rated for voltage and current. You
  can use any amount of voltage / current up to
  that amount -- i.e. there is no minimum.

5
Current

• Current is the measure of the rate at which
  electrical charge carriers (electrons) flow.
• Thicker wire can allow more current to flow
• Unit is Amperes (A)
• 1mA 0.001A
• Direct Current (DC)
• Alternating Current (AC)

6
Resistance

• Resistance is the opposition that a component /
  device / circuit offer to the flow of electric
  current.
• Unit is Ohm (?)
• 1k? 1000?
• Materials / Devices with low resistance are good
  conductors those with high resistance are good
  insulators.
• Resistors have fixed resistances.
• Test resistance using your multimeters, there
  must be no current flowing inside the circuit.

7
Voltage

• Voltage is the amount of electromotive force in a
  circuit. It can be understood as electrical
  pressure.
• Unit is Volt (V)
• 1mV 0.001V
• 1kV 1000V
• Power supplies (eg. batteries) can have fixed or
  variable voltages.
• Voltage is static until a conductive path (eg.
  wire) provides it with a conductive path through
  which to flow.

8
Ohms Law

• When 1V is applied across a component with a
  resistance of 1?, a current of 1A is driven
  through it.
• All DC circuits can be simplified to voltage (V),
  current-carrying conductors (I) and overall
  resistance (R).
• Ohms Law
• V IR
• I E/R
• R V/I
• Make sure you have the correct units.

9
Circuit Diagrams

• Connecting wires have a black dot
• Wires crossing but not connecting have no dot.
  Dont use a half circle.
• Always use the same symbol for the same device.
• Dont use diagonal lines everything should be
  either horizontal or vertical
• Use labels resistors are R1, R2, etc.
  Capacitors, C1, C2, etc. Write a code elsewhere
  on the page describing rating, part nos., etc.
• Get in the habit of writing down schematics. It
  will save you time in the future.
• http//library.thinkquest.org/10784/circuit_symbol
  s.html

10
Poles and Throws

• Pole number of movable contacts
• Throw number of possible closed positions
• SPST (single pole, single throw)

11
Poles and Throws

• Pole number of movable contacts
• Throw number of possible closed positions
• SPDT (single pole, double throw)

12
Poles and Throws

• Pole number of movable contacts
• Throw number of possible closed positions
• DPST (double pole, single throw)

13
Poles and Throws

• Pole number of movable contacts
• Throw number of possible closed positions
• DPDT (double pole, double throw)

14
Switch Varieties

• The Invisible vs. The Obvious
• Pressure Pads
• Detecting presence, movement, location.

Coldcut Headspace, Gridio (2002-)
Beryl Graham, Individual Fancies (1997)
15
Switch Varieties

• Push Buttons
• Content is fixed, pre-recorded. Artwork is
  reactive rather than generative.
• Does not necessarily need a computer.

James Coupe, In the Event of an Emergency (1999)
Marco Evaristti, HELENA (2000)
16
Switch Varieties

• Micro Switches
• Events are discreet automated state changes
  typically occurring device-device rather than
  human-device.

LEMUR, TibetBot
Camille Utterback, see/saw (2001)
17
Switch Varieties

• InfraRed Proximity Switches
• More flexible and mobile than pressure pads
• Also used to detect presence, movement, location

Paul Garrin Yuppie Ghetto with a Watchdog (1990)
James Coupe / Hedley Roberts, 9PIN (2004)
18
Switch Varieties

• Vibration Switches, accelerometers
• Detect minute physical movements
• Useful for measuring change over time

Jonah Brucker-Cohen, Livewindow (2001)
DXARTS in progress
19
Switch Varieties

• Tilt Switches
• Uses mercury to detect orientation.
• Use two or more simultaneously to identify
  multiple axes.

RCA CRD, Blowing Windows
Roger Ibars, Nintendo Gun Shoots Sony Digicube
(2005)
20
Switch Varieties

• Magnetic Reed Switches
• The original wireless switch only one half
  needs to be wired.
• Used for detecting objects that have been picked
  up, put down, opened, closed, etc.

21
The Teleo Intro Module

• Easy to use
• Uses max externals via USB
• Needs to be tethered to computer to run
• http//www.makingthings.com
• Limited devices
• 4 analog inputs
• 2 digital inputs
• 2 digital outputs (2A max.)
• 2 pwm outputs
• Relatively expensive
• Expansion modules are similar prices to the intro
  set

22
Teleo Electronics

• Has 5V, 12V (V) and Ground power terminals
• Never connect V to 5V
• If the board starts getting hot, then unplug and
  check your connections
• Digital In terminals are internally wired to
  ground via resistors

23
Teleo Digital In

• 2 Digital In terminals
• Terminals can be addressed using arguments
• Check your Max window for binding / freeing of
  devices

24
Key tools Breadboard

• Contacts run horizontally
• Two power strips on each side run vertically
• Use to prototype a circuit before soldering
• Be careful not to place more than one component
  terminal on each horizontal contact strip

25
Key tools Multimeter

• Use for analyzing current, voltage, resistance,
  continuity
• Essential for debugging circuits
• Two probes allow you to test values between any
  two points in a circuit
• Dial selects amps / volts / ?
• Select value range (2k, 20k, 200k, etc.)
• Test value of resistors, switch contacts, voltage
  at various points, etc.

26
Key tools Soldering Iron

• Use only for permanent connections
• Always tin your tip to get a smooth consistent
  coating
• Use the tip cleaner to remove excess solder --
  keep your tip clean
• Turn iron off when you are not using it
• Dont use too much solder
• Heat the joint, not the solder -- everything
  needs to be the same temperature
• Use mini-vise, helping hands, etc
• Be careful -- its hot!

27
Wiring Switches

• Use a multimeter to identify which contacts to
  use
• Use a wire stripper to remove a small amount of
  insulator from the wire
• Use a soldering iron to fix wire to the contacts
• Use heatshrink to protect and insulate the joints

28
Switch De-Bouncing

• When switches open, they do not necessarily move
  cleanly from open to closed. This is called
  bounce.
• In order to compensate, we implement hardware
  and/or software debounce.

29
Lab Session 1

• Form 6 groups (5 x 3, 1 x 2)
• Group rules
• Pick your own
• No group can have 2 people from the same class in
  a degree programme
• Make these switches
• Toggle
• Pushbutton
• Micro
• DPDT
• Reed
• Tilt
• Use solder, wire, heatshrink.
• Connect up to your teleo sets and build patches
  for each switch.
• Keep your switches for next time.