Radio Shack | 22-218 | Troubleshooting guide | Radio Shack 22-218 Troubleshooting guide

Developed By
Jennifer R. Barnes and Stephanie A. Popp
Adapted from:
A Switch to Turn Kids On,
Center for Best Practices in Early Childhood,
Western Illinois University
The "Life’s a Switch" project was sponsored by:
National Science Foundation, Biomedical Engineering Program and Research to Aid Persons with Disabilities
Program, “University of Wyoming, College of Engineering, Undergraduate Design Projects to Aid Wyoming Persons
with Disabilities”, NSF Grant BES-0201736, March 2002.
National Science Foundation, Biomedical Engineering Program and Research to Aid Persons with Disabilities
Program, “University of Wyoming, College of Engineering, Undergraduate Design Projects to Aid Wyoming Persons
with Disabilities - Research Experience for Undergraduates” (REU Supplement), NSF Supplement 0224737, April
Life’s a Switch
A Guide for Building Assistive Switches
National Science Foundation • College of Engineering • Wyoming New Options in Technology
University of Wyoming • Laramie, WY 82071
Table of Contents
Overview of WIND/WYNOT……………………………………………………………1
Objectives……………………………………………………………………………….. 4
Overview of the Manual………………………………………………………………… 7
Safety Guide ……………………………………………………………………………...8
Battery Care…………………………………………………….………..10
Basic Circuits……………………………………………………………………..…….. 11
Equipment Operation Guide.…………………………………………………………….17
Wire Stripping……………………………………………………………26
Switch Technology………………………………………………………………………27
Switch Adaptation……………………………………………………………………….32
Inline Plug and Jack……………………………………………………...33
Battery Interrupter……………………………………………………….36
Switch Design and Implementation……………………………………………………...42
Trouble Shooting Guide…………………………………………………………………50
Switch Resources and Part Numbers…………………………………………………….55
Overview Of WIND/WYNOT:
Overview of WIND/WYNOT:
WYoming New Options in Technology (WYNOT) is Wyoming’s federally
funded assistive technology project and is administered by The Wyoming Institute for
Disabilities (WIND), a department of the University of Wyoming’s College of Health
WYNOT is part of a national network of technology related assistance
programs. These programs were initiated through federal legislation in 1988. The
original legislation has since been renamed and reauthorized as the Assistive Technology
Act (AT Act) of 1998. The legislation federally funds projects for the U.S. Department
of Education’s Office of Special Education and Rehabilitative Services. The legislation
extended funding to the fifty states and six territories to develop permanent,
comprehensive, statewide programs devoted to technology related assistance for those
with disabilities.
In 1993, WYNOT became Wyoming’s Tech Act project administered by the
Division of Vocational Rehabilitation. In 1996, the project was reassigned to WIND.
Funding, however, was reduced by 25% in year 9, which began on October 1, 2001. The
funding will be reduced by 50% during year 10 of the federal grant, which will begin on
October 1, 2002.
The mission of WYNOT is to build statewide capacity for universal access to
assistive technology for all of Wyoming and to establish a self-sustaining system that will
continue to meet the state’s need for assistive technology after federal funding for
WYNOT has ended.
In order to meet the program goals, WYNOT will provide
information, training, and technical assistance to statewide and community-based
organizations to enhance their capacity to meet the assistive technology needs of
individuals with disabilities.
Funding For the Project:
In order to provide this information, training, and assistance to Wyoming citizens,
WYNOT has partnered with the College of Engineering at the University of Wyoming.
This partnership has been established to allow students from the College of Engineering
to create and provide custom-designed assistive devices. This partnership will also allow
students to become involved with the community and gain hands on design experience.
One of the projects WYNOT gained interest in was a workshop on switches and toy
Stephanie Popp and Jennifer Barnes, two engineering students from the
University of Wyoming, were selected to develop this instructional manual and facilitate
the accompanying workshop. The workshop provides people from the public with the
knowledge and skills necessary to make their own assistive equipment, such as simple
The National Science Foundation provided the College of Engineering with a
grant to be used as part of the Biomedical Engineering Program and Research to Aid
Persons with Disabilities Program – Research for Undergraduate Education Grant.
For reprints of this manual, please contact:
Dr. Steven Barrett
Electrical Engineering Department
College of Engineering
P.O. Box 3295
Laramie, WY 82071-3295
(307) 766-6181
Introduction to assistive technology
Stimulatory teaching aids
Affordable solutions
Introduction & Objectives:
Before we begin to design and construct any assistive devices, it is important that
we cover the basic objectives of this project. In order to understand these objectives it is
important to understand the reasons, needs, and uses for assistive technology.
What is assistive technology?
Assistive technology can be defined as any device that maintains or enhances a
person’s quality of life. Assistive technology is beneficial for enhancing an individual’s
ability to perform activities of daily living, enhancing communication, improving
mobility, allowing participation in education, enhancing vocational activities, or enabling
One of the main goals of assistive technology is to provide countless opportunities
for children with disabilities to explore, play, learn, and communicate with others. One
way that these opportunities can be provided is through the use of a switch.
A switch simply opens or closes an electrical circuit. It is so basic in our daily
routine that it sometimes is taken for granted. The simple use of a switch gives access to
any appliance, toy, or machine that is operated by a battery or the use of electricity.
This concept is very important in the case of assistive technology.
Stimulatory Teaching Aids
By simply using different types of switches, the lives of children with disabilities
can be changed forever. For example, activating a battery-operated toy through the use
of a special switch allows children, with even severe disabilities, the opportunity to
control external events. This control over external events helps a child to understand
cause and effect, predictability, and normality.
When a child with developmental
disabilities understands the connection between the activation of a switch and the
resulting action it triggers, the knowledge of cause and effect is gained. Therefore, the
basis for all future learning is established.
Encouraging and providing independent learning is the goal of any switch activity
designed for the use of persons with disabilities. Independent learning can be enhanced
using switches coupled with software programs, or modified toys to foster the child’s
realization that they have impact and control over their environment.
In addition, switches allow equalized play opportunities for children with physical
disabilities. A child can participate in group activities through the use of a switch. This
gives a child not only a feeling of self-accomplishment but also a sense of belonging to a
group. All of these factors provide many opportunities, not only for the child but also for
the family. Most importantly, the realization is gained that the disability need not prevent
the child from independently impacting their environment.
A variety of switches are available to meet the needs and skill levels of children
with disabilities. Since there are so many different types of switches available, a careful
and thorough evaluation of the child and their disability must be completed.
evaluation should include determining the most reliable and comfortable body position
and the most controlled and consistent body movements. Through the results of the
evaluation, the best choice of switch type and positioning of the switch can be
determined. Matching the switch type to the child’s disability is essential if that child is
to be successful at using the switch. Although there is a large variety of switches to
purchase or make, some of the most common assistive switches are the push, tread, and
pillow switches. These different types of switches, their uses, functions, and composition
will be discussed in detail later in the text.
Affordable Solutions
One of the current problems facing assistive technology users, including switch
users, is the cost of the available items. One of the goals of this project is to provide
more affordable solutions for switch users.
One way to provide more affordable
solutions is to educate and teach the families of switch users how to make their own
switches and adaptors. For example, some assistive technology vendors sell large button
switches from $25.00 to $45.00, tread switches for $40.00, and pillow switches for
$35.00. Throughout this manual, we will be referring to these commercially available
switches as assistive switches. Amazingly, all of the parts used to make these assistive
switches can be bought and made into your own assistive devices averaging a cost of
around $10.00. This affordable solution is gained through the understanding of assistive
In order to accomplish these objectives and successfully create more cost effective and
reliable equipment, this manual will be covering the following topics:
Basic circuits
Equipment operation
Switch technology
Switch design and implementation
Switch adaptation
Troubleshooting guide
Safety Guide
What you need to know when working with electricity
Do’s and don’ts for electronic devices and wiring
Getting comfortable with electricity
Battery care and safety
Electrical Safety
Do examine cords periodically and check for fraying or other damage.
Do check that cord ratings are the same or higher than the Watts needed by the appliance.
Do wear insulated gloves and use insulated tools when wiring electrical devices
Do use adaptors to connect different types of plugs.
Do unplug devices before handling the wiring.
Do unplug small devices when not in use.
Don’t overload outlets and cords.
Don’t run cords under rugs and carpet.
Don’t remove the 3rd prong on a plug.
Don’t force a plug into an outlet.
Don’t connect a multimeter to a wall outlet.
If an electrical appliance comes in contact with water:
1. Shut off power to the circuit in which the appliance is plugged.
2. Unplug appliance.
3. Drain water and retrieve appliance.
4. Allow the appliance to dry and have a qualified repairman check appliance
before using it again.
Did you know?
Ø The third prong on many plugs provides a path to ground for straying or
leaking electricity. This helps prevent electric shock.
Ø Polarized plugs (where one prong is wider) help prevent electric shock by
insuring the plug is properly inserted into the outlet.
Battery Care and Safety
Ø Store batteries in a cool dry place, never in direct sunlight. Never leave batteries in
temperatures below 30° F or above 100° F.
Ø Store batteries in original package or in a similar organized manner.
Ø Keep batteries out of reach of children.
Ø Only recharge batteries marked as rechargeable.
Ø Do not mix used and new batteries or different brands of batteries.
Ø Replace all batteries at once with the same brand of battery.
Ø Take care to properly align + and – ends.
Ø Maintain clean contact surfaces by rubbing contacts in devices with a clean pencil
eraser or a rough cloth after each battery replacement.
Ø Never dispose of batteries in fire; they can explode.
General purpose alkaline
batteries may be disposed of in small quantities in the trash. Check with your area’s
disposal service provider for recycling options and disposal methods for other types
of batteries.
Basic Circuits
• Power source and load
• Switches
• Voltage, current, and resistance
• Ohm’s Law
• Types of circuits
Basic Circuits
After learning the necessary precautions that should be taken when working with
electricity, it is now possible to build assistive equipment. In order to do this it is
important to gain an understanding of basic circuitry. A circuit diagram is a model of
how electricity flows and the elements it passes through. The following sections explain
the various attributes of a basic circuit.
Power Source and Load
Electricity is made up of electrons. This flow of electrons is called a current. A circuit is
a path for current to flow. This path begins at a power source, continues through the
various elements of the circuit, and finally arrives at the load.
The power source is
usually a battery or an electrical outlet. The path through which the current travels can be
made of anything that is a conductor of electricity. A conductor is a material that allows
an electrical current to pass through freely. A good conductor is typically made of a
metal such as copper. Finally, the load is the element receiving and using the electricity.
This can be anything from a light bulb to a buzzer, or even a toy.
Basic Circuit
Power Source
There can be many elements within a circuit. One common element within a circuit is a
switch. A switch is a device that when triggered closes the circuit, allowing the current to
flow from the source (battery) to the load (light). When the switch is released, it opens
the circuit stopping the current flow. By turning the switch on or off, one can regulate
the flow of current through the circuit thereby turning the light on or off. Below are the
circuit diagrams for an open and closed circuit.
Open Circuit
Closed Circuit
(light is
Current Flows
(light is "off")
Current does not Flow
Voltage, Current, Resistance
In order to design, test, and troubleshoot any electronic device, it is important to
understand what differentiates one circuit from another. The first thing to understand is
how current flows through a circuit. This can be explained by voltage. Voltage is
measured in Volts (V) and is the “pressure” pushing electrons through the circuit. Once
again, this flow of electrons through the circuit is current. Current is measured in
Amperes (Amps, A). Finally, in any electronic device there is resistance. Resistance is
anything in the circuit that opposes the flow of electricity. Resistance can be used to
control the amount of current flowing through a circuit. Resistance is measured in Ohms
(Ω). More resistance in a circuit means less current flow. Less resistance in a circuit
means greater current flow.
Ohm’s Law:
Ohm’s Law is a formula used in electronics to calculate an unknown amount of current,
voltage, or resistance. Current is abbreviated I. Voltage is abbreviated V. Resistance is
abbreviated R. The relationship between voltage, current, and resistance is expressed as:
V= I x R, or voltage equals current times resistance. Use this formula to solve for an
unknown value when the other two values are known.
(Remember the battery is the device producing the voltage and should be calculated as
voltage in Ohm’s Law).
Types of Circuits
The final thing to understand about basic circuits is the different ways that circuits can be
constructed. The three types are series, parallel, and combinational circuits.
Series Circuit
A series circuit is a circuit where all circuit elements are arranged in a loop so all current
passes through each element without branching. In a series circuit, there is only one
straight path through which current can flow. One example is a string of Christmas lights
that are in series. All loads (the lights) are in a single path, like the series diagram below.
If one light burns out, the rest of the lights will turn off because the circuit has a break in
it and current can no longer flow to the rest of the lights.
Power Source
Series Circuit
Load 1
Load 2
Parallel Circuit
A parallel circuit has two or more branching paths for the current to travel. This is
accomplished by constructing the loads parallel to each other. This is where the term
parallel circuit comes from. If the loads are Christmas lights in parallel, when one light
burns out the rest of the lights stay lit since there is more than one path for the current to
Power Source
Parallel Circuit
Load 1
Load 2
Combinational Circuit
A combinational circuit includes both series and parallel paths for the electricity to flow.
Load 1
Power Source
Load 2
Load 3
Circuit with a Toy:
Now that you have an understanding of basic circuits and the difference between series
and parallel circuits, it is important to understand how a switch and toy are a circuit. All
toys will be used as a series circuit. This will be done by placing an interrupter into the
battery pack. Taking the current that the battery is generating and moving it outside of
the toy. This battery interrupter connects to an external switch. When the switch is
pressed down, it will complete the series circuit and the toy will activate. The circuit
diagram for this specific series circuit is shown below.
Toy as a Series Circuit
Equipment Operation Guide
• Voltage/ohmmeter operation
• Soldering iron
• Wire stripping
What is a multimeter?
A multimeter is a combination of three meters used to take measurements from an
electric circuit. A typical multimeter includes an ammeter, voltmeter and
ohmmeter. The ammeter measures current in Amps, the voltmeter measures
potential difference between two points (voltage) in Volts, and the ohmmeter
measures resistance in Ohms. There are buttons or dials to select these different
functions and two probes to connect the multimeter to the circuit.
There are two types of multimeters: digital and analog. Digital multimeters give
an output in numbers on a digital display. Analog multimeters give an output
with a needle moving along a dial with multiple scales. An analog multimeter is
selected for use in this program because of its cost effectiveness.
The multimeter is a valuable tool for troubleshooting electrical wiring, broken or
poor connections, faulty parts, and absence of power. The instructions for using a
multimeter are given first, then some examples of applications you may use with
this manual. Multimeters are easily damaged; so take care to understand all
directions before use!
Dial and Scales
Ohmmeter Selection
Ammeter Selection
Voltmeter DC
Voltmeter AC
Negative Probe
Positive Probe
Radio Shack #22-218
General Tips:
Never connect a multimeter to a wall outlet or any similar power supply.
Do not drop the multimeter.
Use the tips of the probes for contact with the circuit. Don’t let your fingers touch
the metal. Connect the red probe to the positive probe input and the black probe
to the negative probe input.
Read instructions thoroughly so you properly select the function and scale of
measurement. This will prevent overloading the multimeter.
Check the pathways in the wiring or device you are testing for any random or
loose wiring that touches the circuit you are testing. This will prevent short
circuits, which allow free current flow and can harm you, destroy equipment, and
start fires.
Each function of the multimeter (voltmeter, ohmmeter, ammeter) is connected to
a circuit in different ways, so review the following sections before each use.
If the multimeter does not work, try replacing the fuse and/or the battery.
Using the voltmeter function
1. The voltmeter measures the voltage between two points in a circuit.
measuring voltage, the circuit is not changed. Begin by disconnecting the power
to the circuit.
2. Next, determine if the voltage you wish to measure is from an AC or DC source.
AC means alternating current and comes from a wall outlet. DC means direct
current and comes from a battery or other steady voltage source.
3. Notice that on the multimeter there are three choices of scales for both the AC and
DC voltage measurement. If you know approximately the highest voltage value
you anticipate to read, choose the scale with the next highest value. If you are
unsure of the scale to choose, choose the highest scale. If the needle shows little
or no movement when you take measurements, switch to the next lower scale.
Power Source
4. Now that you know how to select the
function and scale on the multimeter,
check this before touching the probe tips
to the circuit. To connect the probes to
Black Probe
Load 1
Red Probe
the circuit, a parallel connection must be
made with the probes and the circuit.
This means you do not change the circuit
at all. Touch the red and black probes to the corresponding positive and negative
ends of the part of the circuit you wish to measure.
5. After checking for correct placement of the probes, turn on the power to the
circuit and take a reading.
Using the ohmmeter function
1. The ohmmeter measures the resistance of an
element in a circuit.
Before using the
Load 1
ohmmeter, the element must either be
removed from the circuit or have no power
running to it when the resistance is measured.
2. Now, set the multimeter to the ohmmeter function, one click counterclockwise
from the off position (shown on first page of section). This selection is labeled
1KΩ (one kilo Ohm).
3. Calibrate the ohmmeter by touching the two probes together and set the needle to
zero using the calibration dial on the side. Do this every time before use.
4. Make sure there is no power connected to the element you are measuring. Touch
the probes to opposite ends of the element and check the reading on the
Using the ammeter function
1. The ammeter measures the current in a circuit. To measure current, the circuit
must be broken to connect the ammeter in series. First, make sure the power in
the circuit is off.
2. Set the multimeter to the ammeter function and notice that maximum reading can
be 150 mA DC. This means the source of power can only be direct current (e.g.
3. Break the circuit where you want to
find the current, and touch the black
probe to the negative side and the red
probe to the positive side.
Power Source
batteries) up to 150 milli Amps (or 0.150 Amps).
Red Probe
Load 1
4. Turn on the power to the circuit and
Black Ammeter
take the reading.
Always check these general steps before using the multimeter:
1. Begin by disconnecting the power to the circuit.
2. Set the appropriate function on the multimeter.
3. If applicable to the function, select the range for the scale. For the multimeter
recommended in this manual, this applies only to the voltmeter function.
4. Properly connect the multimeter to the circuit or element of the circuit you need to
measure. This is very important. Each function requires a different set-up!
Power the circuit for current and voltage measurements.
5. Write down the reading and turn off the multimeter and circuit.
The following applications are examples of simple uses for the multimeter. These
are only a few ways to make use of a multimeter and are meant to illustrate the
previous instructions. In most cases it is easier to use the voltmeter and ohmmeter
for troubleshooting, so the following examples focus on those two functions.
Testing Batteries for Power
Set the function to DC Voltage and the scale range above the voltage of the
battery. For A through D batteries, set the range to 15 V. Match the polarity of
the probes to the battery with the red probe on the positive and the black probe on
the negative end. Check the reading. If the voltage reading is more than 20%
below the original rating the battery needs replaced.
Check for a bad plug or broken wire
Set the multimeter to the ohmmeter function. Make sure there is no power
connected to the element you want to check. Attach the probes on opposite ends
of the plug or wire, so that the possibly damaged part is between them. Check the
reading. A reading of zero or close indicates no resistance. If you are checking
wire, this means the wire is unbroken. If you are checking a plug, it means the
plug is shorted. A high or infinite (∞) reading indicates the circuit is open. For
wire this means it is damaged. If you are checking a plug, this reading means the
plug is fine.
Test a jack in the same manner used for testing plugs.
Check for a connection in a switch
Set the multimeter to the ohmmeter function. Make sure there is no power
connected to the switch. You can check whether the switch is connected or
disconnected depending on the position of the switch. This is especially useful
when wiring. Touch the probes to the leads on the switch you are exploring and
check the reading. A reading of zero indicates no resistance and therefore a
connection. A high or infinite (∞) reading indicates the switch is disconnected in
this position.
Interpreting Measurements
You now know how to use the multimeter for a limited number of applications.
Keep in mind that you can use the voltmeter or ohmmeter functions for almost
any troubleshooting. Use the voltmeter when you want the power source on in
the circuit, or when you can’t remove an element from the circuit. Use the
ohmmeter when you want to check for broken or damaged parts individually.
Also, if you wired something correctly by checking if it completes a circuit with
the ohmmeter.
When using the ohmmeter, keep the following in mind:
A very high or infinite (∞) reading indicates an open circuit. This means little
or no current can flow and the resistance is high. This can mean any of the
following: a broken or loose connection, a faulty part, or the probes of the
multimeter are not connected well.
Don’t forget the ohmmeter needs
calibrated before each use.
A reading of zero indicates a closed circuit. This means current can flow and
the resistance is low. This can mean the part is working properly, but it can
also indicate a short circuit. A short circuit is when a broken connection with
a loose wire touches another part of the circuit you are measuring. Avoid this
by checking the circuit pathways for loose wiring before making
Soldering forms electrical connections quickly and with little expense. This technique is
easy to learn and safe if the following precautions are noted.
Radio Shack #910-2425
Soldering Iron
Safety Precautions:
Use needle nose pliers or wear heat resistant gloves to hold small pieces.
Wear safety glasses.
Solder only on fire resistant surfaces.
Never leave soldering iron plugged in and unattended.
Be aware of the people around you, and avoid sudden and wide movements with the
Only set hot iron on stand. The iron reaches temperatures of around 650° F.
Replace worn or burnt cords.
Making a solder joint:
1. Plug in the soldering iron about ten minutes before use so it can heat up to the required
temperature (around 650° F).
2. All parts must be clean for a good soldering connection. Clean off dirt and grease
with a rag soaked in cleaning solvent. Avoid touching parts after cleaning.
3. “Tin” the tip of the iron if it is a new tip. This is done by applying solder to the
working end of the tip and wiping it off onto a moist sponge. This is repeated until a
thin film of solder forms on the working surface of the tip.
4. Add a tiny amount of fresh solder to the cleansed tip. This promotes rapid heat
transfer to the connection in the next step.
5. Preheat the area of the connection by holding the iron tip on the area for a couple
seconds. With the iron tip still heating, apply solder to completely cover the area of
the connection. It takes two or three seconds to solder the connection.
6. Remove the solder and then the iron tip. Wipe the tip on a moist sponge to clean it
and replace the soldering iron to its stand.
7. Do not move the parts until the solder has cooled. A properly soldered connection is
smooth and shiny in appearance.
8. If you are not satisfied, the solder can be removed with desoldering braid (Radio
Shack #64-2090). Place the desoldering braid over the solder connection, then place
a hot soldering iron on top of the braid. Remove the braid and iron after all the solder
has been melted and drawn into the braid.
First Aid:
If you are burned, cool the affected area with cold running water, ice, or anything else in
the freezer for ten minutes. Remove any rings etc. before swelling starts. Bandage the
area to protect against infection and do not apply lotions, ointments etc., nor prick any
blisters which form later. Seek professional medical advice when necessary.
Wire Stripping
The wire cutter/stripper shown and recommended in this kit is adjustable for 10 to 30
gauge wire. A larger gauge wire has a smaller diameter and a smaller gauge wire has a
larger diameter. Wire strippers are used to remove the protective insulator from wire and
expose a short bare wire lead so it can be connected to a terminal.
Notch for stripping
protective insulator
Blades for clipping wire
Adjustable slide screw
Radio Shack #64-2129
Wire Cutter/Stripper
1. If the wire is polarized (has two leads stranded together),
begin by clipping between the wires with the tip of the
wire cutter. Each lead should maintain its own insulator
as you separate the two ends with your fingers.
2. Now adjust the wire stripper for the size if wire you are using. Place a piece of wire
that is the same gauge you will be using in the stripping notch at the head of the wire
strippers. Close the handles firmly and check how far the strippers cut through. Now
adjust the wire strippers so they cut only the protective insulator, not the wire. Move
the slide screw toward the head of the tool for thicker wire. For thinner wire move
the screw toward the handles. Check again for proper adjustment (no wire is cut).
3. Place about ¼ inch of the wire lead you need stripped in the notch at the head of the
wire strippers.
4. Close the handles firmly and continue holding them closed with one hand.
5. Grasp the longer end of the wire with the other hand as
close to the wire strippers as possible and push the
stripper head away with your thumb. The protective
insulator should slide off and expose bare wire strands.
Switch Technology
• Switch selection
• Switch technology
• Pole versus throw terminology
• Commercially available switches
Switch Technology
Switch Selection
Many different switches are available on the market that can meet the needs of children
with disabilities. In the following chapters, you will learn about the different types of
switches, how to connect them to a toy, and how to adapt them to meet your specific
needs. This manual focuses on using switches to adapt toys to help enhance the child’s
learning process. The switch is used to control the toy instead of the on/off switch
already on the toy. In this way, a switch can be selected that will best suit the needs of
the child. You can decide how best to customize the switch to offer a stimulating action
for the child to complete in order to activate the toy.
When selecting a switch, consider the possible placement of the switch, how the child
will activate it, and the stimulus to motivate the child. Make sure the switch is placed
where the child can be in a stable position to easily activate it. Avoid placing the switch
in the child’s resting position. Determine if the child will need to activate the switch by a
pushing, pulling, squeezing, or stepping action. This will be the most helpful information
when selecting the switch type.
This chapter in the manual will aid you in understanding how switches work and the
terminology associated with switches. This chapter will also explain many commercially
available switches and how you can use them to fit your needs. Later chapters explain
how to customize these switches or how to make your own.
Switch Technology
All switches essentially perform the same action: they connect and disconnect a circuit as
A connected circuit is also referred to as a closed circuit.
Similarly, a
disconnected circuit is referred to as an open circuit. Some switches are normally open
or normally closed. Normally open means that unless the action associated with the
switch is implemented, the circuit is open (disconnected). For example, a switch that
must be pressed down to activate a toy is normally open. Normally closed means that the
switch is closed (connected) unless the switch is activated. This would be a switch where
the toy would always be running unless the switch is pressed and held. For the purposes
of adapting toys, normally open switches are suggested.
Pole/Throw Terminology
When buying switches, you will need to understand the pole-throw terminology
associated with switches. A pole is the moving connector in the switch. The throw is the
connection. There can be multiple poles and throws. The following diagrams show what
a circuit of the switch looks like on the left and how many wires can be hooked up on the
right. A single pole single throw switch looks like the following picture:
With one action the pole can be moved to connect with the throw. You may see this type
abbreviated SPST. Another common switch is single pole double throw (SPDT). The
pole can be moved to either connection (throw).
If only one of the throws is wired, the SPDT functions like a single pole single throw.
The above examples are very simple and most likely what you will use. For an example
of more throws, a single pole four throw looks like a rotary switch:
The pole can be moved to four positions, each throw can be wired to its own function.
Commercially available switches
Now that you know a little bit about switch technology, use the following list as a short
guide to commercially available switches.
Reed Switch
A reed switch is a tube with two wire leads coming from each side. Inside the tube are
two metal reeds that are not touching. To connect the switch and close the circuit, a
magnet is placed over the middle of the tube, drawing the reeds together. As long as the
magnet is in place the circuit is closed and the connected device will operate. One way to
use a reed switch is to place it inside a block of wood. An opening drilled above the
switch fits a removable magnet. Varying shapes and colors on the magnet and block can
be used to make this more stimulating.
Roller Lever Switch
The roller lever switch is a single pole double throw switch. There are three terminals on
the bottom of the switch. The terminals are labeled “C” (common), “NO” (normally
open), and “NC” (normally closed). One wire always connects to the common terminal.
It is recommended that the other wire connects to the normally open terminal so the
attached device is off unless the switch is pressed to complete the circuit. The switch is
operated by applying pressure to the lever with the hand, foot, head, etc. As long as
pressure is applied, the circuit will be completed and the connected device will operate.
When the pressure stops, the device will stop. Another pressure activated switch is the
pillow switch. This is a soft sensitive switch that you will be taught to make in a later
Push Button Switch
The push button is another common switch. The bottom only has two leads so wiring is
easy. There are two types of push button switches. A momentary push button is held
down to turn a device on and released to turn it off. An on/off push button is pushed to
turn a device on and pushed once more to turn it off. These simple switches come in all
different shapes and sizes so there are many applications using different covering and
mounting techniques.
• Switch Adaptation
• Battery interrupters
• Switch extension cords
• Jacks and plugs
• System connected with a toy
Switch Adaptation
You are finally ready to begin making your own switch and adapting it to a toy. The
following sections include directions for all of the parts that need to be connected in order
to adapt a switch into an assistive device.
Inline Plug
Inline jack and plug set
Polarized, stranded wire
Soldering Iron and Solder
Wire Strippers
1. Cut a piece of wire to a length of about 6 feet or to the length you need. Use wire
cutters/strippers to separate both ends of the wire to about ½ inch. Then strip the
insulator from the ends of each lead to expose about ¼ inch of bare wire.
2. Take the jack and plug set. This is what the set looks like when it is opened from the
3. Pull the jack and the plug set apart, to separate the two pieces from each other.
Unscrew the plastic casing from the jack and the plug. The picture below shows the
jack and plug when the casing has been unscrewed. The inline plug and casing are
pictured on the left, and the inline jack and casing on the right. For this step, we will
be using the inline plug.
Inline Jack Casing
Inline Plug Casing
Inline Plug
Inline Jack
4. Take the plug without the casing. Find the two terminals to which you will solder
wire. The longer one is the negative terminal and the shorter one is the positive
Take one exposed lead and run it
through one of the small holes on either the
Negative Terminal
positive or negative terminal. Once you have
the wire looped through the hole and secured,
solder it to the terminal. Take the other lead,
run it through the hole on the other terminal, and
solder it.
Once you solder the wire to the
Positive Terminal
positive terminal, wrap electrical tape around it. This prevents the positive and
negative terminals from touching each other, causing a short.
5. After the wire has been soldered to the plug, feed the free end of the wire through the
plastic casing and screw the casing back onto the plug.
Inline Jack
Inline Jack
Polarized, Stranded Wire
Soldering Iron and Solder
Wire Stripper
1. Construct an Inline Jack in the same manner used in steps one through five for the
Inline Plug.
Battery Interrupter
Thin Clear Plastic (packaging from curling irons, electronic equipment, and toys)
Copper Tape
Polarized, Stranded Wire attached to an Inline Jack
Soldering Iron and Solder
Wire Strippers
1. First, cut a piece of thin plastic into a square about ½” x ½”. Any plastic that is
comparable to that recommended in durability and thickness can be used. Consider
that the plastic must act as an insulator between two pieces of copper tape, and must
be thin enough to fit in the battery pack compartment of a toy.
2. Place a piece of copper tape on each side of the plastic. Do not let the copper tape on
one side touch the copper tape on the other side. Remember, you are trying to
insulate the copper sides from each other. This will now be referred to as the battery
3. Separate (½ in.) and strip (¼ in.) the free end of the wire attached to the jack.
4. Solder one lead to the copper tape on one side of the battery interrupter. Solder the
other lead to the copper tape on the other side of the battery interrupter. Make sure
when soldering that the exposed leads will not touch each other. Check once more
that the pieces of copper tape are fully separated by the plastic.
Side View
5. Check to make sure that your battery interrupter is going to work by using your
Place the probes of the ohmmeter on opposite sides of the battery
interrupter. If your battery interrupter is functioning properly, the needle on the
multimeter should continue to point to infinity (∞).
6. To use the finished battery interrupter, place it in a toy. In order to do this, remove the
battery pack covering from the toy. Place the battery interrupter between one of the
batteries in the pack and its corresponding connection. Replace the cover on the
battery pack. Make sure the original switch on the toy is in the ON position.
Polarized, Stranded wire attached to the Inline Plug
Switch of your choice
Soldering Iron and Solder
Wire Strippers
1. Separate (1/2 in.) and strip (1/4 in.) the free end of the wire that is attached to the
plug. These leads will be soldered to the leads on the switch.
2. Turn the switch over and solder one lead to the free terminal. This should be labeled
common or “C”. Solder the other lead to the normally open terminal, labeled “NO.”
If there are no labels, or you cannot determine which terminal to solder to, refer to the
Multimeter section of the Equipment Operation Guide.
3. To ensure that the switch is properly connected, use the following pages as a guide to
connecting the switch to the toy circuit. When the switch is pushed the circuit will be
closed ensuring that the toy will turn on.
Conclusion of Switch Adaptation
Now you have a wire soldered to a plug and to a switch. This plug connects to a jack,
which runs to a toy.
Toy as a Series Circuit
You now have all the components to make a toy into a series circuit. You have made a
battery interrupter, which takes the current from the battery of the toy and transfers it to
an external switch. When the switch is triggered, it closes the circuit and the toy turns on.
The picture below shows the components you have made and how they connect.
On the left is the switch, which runs to the plug. This is connected with the jack, which
runs to the battery interrupter. The battery interrupter is placed into the battery pack of a
toy. In this picture, the battery pack has been removed from the toy. As long as the toy’s
original switch is ON, when the switch is pressed the current flows to the toy, turning the
toy on.
Using Switch Adaptation
You can now make the system shown on the previous page into many different types of
assitive switches.
Examples of assitive switches are large button switches, pillow
switches, and tread switches. In the next chapter, you will be given ideas and instructions
on how to turn inexpensive, off-the-shelf items into innovative assistive switches. Be
creative and experiment with different materials and switches in order to obtain the
teaching aids that you want and need.
Switch Design and Implementation
• Large button switch
• Tread switch
• Pillow switch
Large Button Switch
Cap or lid*, about 3” diameter
Pushbutton Switch
Base piece of wood or plastic, about the size of the cap or larger
Polarized, Stranded Wire attached to an Inline Plug
Velcro or Cushion Feet (optional)
*When choosing the cap, consider how the child will react to the large button switch.
Choose a colorful cap or one you can paint. Choose a size the child can easily push.
Many smooth caps and lids can be found on inexpensive household items such as soap
dispensing dish scrubbers, peanut butter or jelly jars, travel soap dishes, and aerosol
cans. Also consider cutting racquet or tennis balls in half.
Soldering Iron
Drill and bit
Wire Strippers
Hot Glue Gun and Glue, or Super Glue
1. Before starting, determine how the push button switch will be mounted onto the base
piece. Some switches may need holes drilled into the base piece so the screw mount
or terminals can fit through. Measure the diameter of the pieces that need to fit and
the distance between them to determine the drill bit size needed and where to put the
holes on the base piece. Drill these hole/s so the switch is centered on the base.
2. Separate (½ in.) and strip (¼ in.) the free end of the wire attached to the plug.
3. If the switch terminals go through the base, or if any part of the switch will go
through the base, feed the wire leads through the hole/s so they are ready for
4. Solder the wire leads to the switch terminals.
5. Be sure the switch fits easily into position onto the base. Then, attach the switch to
the base. If the switch has a screw mount, screw the switch to the base. Otherwise,
glue the switch to the base. Tape the wire to the base next to the switch or the holes
in the base. This prevents the wire extension from twisting around the terminal
connection and breaking.
6. Before gluing the cap onto the push button, be sure there is enough room for the cap
to fully press the switch without hitting the base piece. If the cap touches the base
and is too deep to be glued to the push button, glue an extra piece of wood or plastic
between the inside of the cap and the push button. Finally, attach the cap onto the top
of the push button with glue.
7. For comfort of use, consider attaching cushion feet or Velcro to the bottom of the
Tread Switch
Mini SPDT Roller Lever Switch
Two Boards or Plexiglass panels (3 ½” x 6”)
Polarized, Stranded Wire attached to an Inline Plug
Duct Tape
Rosin Core Solder
Cushion Feet
½ Yard Fabric
Drill and 3/16” bit
Soldering Iron
Wire Strippers
Hot Glue Gun and Glue or Super Glue
1. Find a place on one panel for the lever switch where the top panel will push down on
the roller lever, not on the hinge of the switch.
2. Trace around the switch on the bottom panel when you find the correct placement.
Some switches may need three holes drilled through the panel so the terminals on the
bottom of the switch can fit through.
If so, measure the distance between the
terminals and drill these holes now.
Be sure to hold the drill so the bit is
perpendicular to the panel.
3. Separate (½ in.) and strip (¼ in.) the free end of the wire attached to the plug.
4. If the switch leads go through the panel, feed one end of the wire through the holes.
Do this by threading one lead into the hole that will connect to the common lead on
the switch, and threading the other lead into the hole that will connect to the normally
open lead on the switch. Make sure the leads are through the panel before soldering
them to the switch in the next step.
5. Solder the wire leads to the switch terminals.
6. Be sure the switch fits easily into position onto the panel. Then, attach the switch to
the panel. If the switch has a screw mount, screw the switch to the panel. Otherwise,
glue the switch to the panel. Tape the wire to the panel close to the switch or to the
holes in the panel.
This prevents the wire extension from twisting around the
terminal connection and breaking.
7. You are now ready to assemble the body of the tread switch. Cut a piece of duct tape
to cover the width of the panel and tape the two panels together to create their vertex.
Be sure to leave about ¼ inch between the ends of the two panels so the hinged vertex
can move without tearing the tape.
8. Now you will use the foam to support
this top panel and to act as a spring to
return the panel to its original position
after pressing the switch. Cut a small
piece of foam and fold it in half. Place it
in the vertex of the two panels as shown. Glue it down once you find the proper
9. Gently push the top panel down until it is
just above, but not touching, the roller
lever. Tape this opening of the top and
bottom panels as shown so the panels
remain in the correct position. Use another piece of tape to completely cover the
open sticky end of the tape attached to the switch body.
10. Use your creativity to cover and decorate the switch body with contact paper or fabric
to provide visual stimulus.
11. Attach the cushion feet to each of the four corners on the bottom of the tread switch.
The switch is now ready for use.
Pillow Switch
2 Copper Clad Boards (about 4 in. x 4 in.)
Foam (about 1/8” thick)
Foam (about ½” – 1” thick)
Inline Plug
Polarized, Stranded Wire
Soldering Iron and Solder
Wire Strippers
1. Cut two copper clad boards and the foam to the size and shape of the desired switch
(A four inch diameter circle works well). The foam piece should be slightly larger
rather than slightly smaller than the copper board pieces.
2. Separate (½ in.) and strip (¼ in.) the free end of the wire attached to the plug.
3. At the other end of the wire, flatten the exposed wire
from each lead. Position one of the wire leads on the
edge of the copper board. Be sure the insulator of the
wire lead is as close as possible to the edge of the copper
Solder the lead to the board.
Repeat this
procedure to solder the other lead to the other copper
4. Cut out the center of the foam circle, leaving about ½” around the
outer edge.
Place this piece in between the two copper clad
boards, with the copper sides facing each other.
Lightly tape
around the edges of this assembly to hold the pieces in place.
Copper Clad Board
5. Now that you have made the switch, make a “pillow case” from visually or tactilely
stimulating cloth to encase it. Be sure to leave room to put foam or pillow stuffing all
around the switch.
Troubleshooting Guide
Troubleshooting Guide
What if you push the switch, but the toy won’t come on?
First, check that the plug and jack are securely connected. Check that the battery
interrupter is firmly placed in the battery pack of the toy between one battery and its
corresponding connection. Also, be sure the switch on the toy is in the ON position.
Visually check all wires for damage.
Then use the ohmmeter function of a
multimeter to check for resistance along the length of each wire. This method is
described in the Multimeter section of the Equipment Operation Guide.
Look at the underside of the switch. Visually check that the leads of the wires are
still soldered to the contacts on the switch and that the wires don’t touch. Then,
making sure the switch is in the OFF position, use the ohmmeter to see if there is a
short. Place the probes onto the switch terminals; if the needle moves toward zero the
switch is shorted. This means that there is a problem with the wire leads and contacts
or with the switch. First, remove the solder, cut the wire back, and reconnect the wire
to the switch. If the switch still shorts, the problem is probably the switch. Cut the
wire from the switch and solder it to a new switch. If the toy still doesn’t work after
you have determined there are no short circuits, the problem most likely lies
somewhere else.
Disconnect the plug and jack. Unscrew the plastic casing from the plug. Visually
inspect the positive and negative terminals of the plug making sure the terminals do
not touch and the wires do not touch each other. Refer to the Multimeter section of
the Equipment Operation Guide and check both the plug and jack for problems. If the
check shows a problem with the plug or jack, try resoldering the wire to the plug or
jack, or use a new plug or jack.
Remove the battery interrupter from the toy. Visually inspect the interrupter, making
sure the wires are securely soldered to each side of the interrupter.
AC – Alternating Current. Current that reverses its direction at regular intervals, such as
the current produced from a wall power outlet.
Ammeter – A device used to measure current flow in a circuit.
Ampere (Amp) – The units used to describe current.
Analog – A device in which data is represented by continuously variable physical
quantities, e.g. a meter that has a dial that moves along a scale is an analog meter.
Assistive Technology – Any device that maintains or enhances a person’s quality of life.
Circuit – A path for current to flow. This includes a power source, load, and any other
conducting components along the path.
Closed Circuit – A complete conducting path allowing current to flow freely.
Conductor – A material that allows an electrical current to pass through freely.
Current – A flow of electric charge.
DC – Direct Current. Current flowing in one direction only. This may come from a
battery power source.
Jack – The part in the in-line plug/jack set that has a hole to connect to the plug.
Load – An element in a circuit that uses the flowing electricity such as a light or toy.
Multimeter – A device used to measure properties in a circuit. A multimeter typically
includes a voltmeter, ammeter, and ohmmeter.
Normally Closed – Current flows through the circuit unless the switch is pressed. (Refer
to page 13).
Normally Open – Current does not flow through the circuit until the switch is pressed.
Ohm – The units used to describe resistance.
Ohmmeter – A device used to measure the resistance through an element of a circuit.
Open Circuit – A disconnected circuit; no current flow is possible.
Parallel – A circuit arranged whereby the current branches off to different elements.
Plug – The part in the in-line plug/jack set that has a protruding terminal to connect to the
Power source – The element in a circuit that produces current flow, such as a battery.
Resistance – An element in a circuit that resists electric current.
Series – A circuit arranged whereby the same current passes through each element
without branching.
Short Circuit – A connection of low resistance across two points in a circuit between
which points the resistance is usually much greater. An unintentional short circuit allows
free current flow where it may cause bodily harm, destroy equipment, and start fires.
SPDT – an abbreviation of Single Pole, Double Throw; a type of switch discussed in the
switch technology section.
SPST – an abbreviation of Single Pole, Single Throw; a type of switch discussed in the
switch technology section.
Switch – A device used to open and close a circuit.
Volt – The units used to describe voltage.
Voltage – The potential difference between two points; creates current flow in a closed
Voltmeter – A device used to measure the voltage across an element in a circuit.
Switch Resources and Part Numbers
Switch Resources and Part Numbers
Cap or Lid
(Soap Dish)
Store: K-Mart
Part #01900
Price: $2.29
Momentary Push Button Switch
Store: Radio Shack
Part #275-609
Price: $2.99
Store: Radio Shack
Part #22-218
Price: $14.99
Copper Clad Board
(Dual Sided PC Board)
Store: Radio Shack
Part #2761499
Price: $3.79
Roller Lever Switch
Store: Radio Shack
Part #275-017
Price: $2.49
Copper Tape
Store: RP Electronics
Part #22-509
Price: $8.64 +shipping
Soldering Iron
Store: Radio Shack
Part #64-2802
Price: $7.99
Cushion Feet
Store: Radio Shack
Part #64-2346
Price: $1.69
Store: Radio Shack
Part #64-025
Price: $2.99
Electrical Tape
Store: Radio Shack
Part #64-2380
Price: $2.99
Store: K-Mart
Price: 1.79
(Assorted Make-up Sponges work great)
Store: K-Mart
Inline Plug/Jack Set
(Mono to Mono Phone Plug/Jack Set)
Store: Radio Shack
Part #274-283
Price: $3.99
Wire Strippers/Cutters
Store: Radio Shack
Part #64-2129
Price: $2.99
Store: Radio Shack
Part #278-1301
Price: $3.19
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