Reciprocating Saw

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Reciprocating Saw - Variable Resistors and
Switches By Ryan Kim
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Contents

1. Introduction to the Saw and Variable Resistors
2. Different Types of Variable Resistors
3. Rheostats
4. Potentiometers
5. Applications
6. Conclusion and References

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Introduction
Reference http//www.ryobitools.com
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Introduction (Contd)
Variable Switch Component

• Variable Resistors
• Resistance can change by turning a shaft or
  sliding a control
• Resistance tracks can be made of carbon, cermet,
  or a coil of wire
• Two main methods are to increase tension in the
  wire or to increase contact area
• Two main types are rheostats and potentiometers

References http//www.ryobitools.com http//en.
wikipedia.org/wiki/Resistor
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Introduction (Contd)
Schematic for Variable Resistors

• Overall Objective
• To learn how a variable resistor works
• To be able to distinguish the difference between
  a rheostat and a potentiometer
• To know the main applications for a variable
  resistor

References http//www.allaboutcircuits.com/vol_6
/chpt_3/6.html
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Two Types of Variable Resistors

• Potentiometer (Rotary)
• 3 terminals (2 fixed, 1 variable)
• Normally used to vary voltage
• Most commonly used variable resistor
• 1 terminal at each end is hooked to power source
• 1 terminal in the middle acts as a wiper that
  axially rotates
• Turning a knob moves the wiper across a resistive
  metal strip (Modern resistors use a resistive
  plastic track)

• Rheostat (Linear Potentiometer)
• 2 terminals (1 fixed, 1 variable)
• Normally used to vary current
• Variable wiper end can be controlled by a slider
  or a screw mechanism for a rotating motion)
• Consists of a resistive track that is made of
  plastic (or metal) and the slider moves across
  the track, increasing or decreasing resistance

References http//www.allaboutcircuits.com/vol_6
/chpt_3/6.html http//www.kpsec.freeuk.com/compone
nts/vres.htm
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Rheostats (Linear Potentiometers)

• Often used with high currents
• Usually use a plastic track due to easy corrosion
  and wear from metal tracks
• Track orientation is linear (a.k.a. sliders)
• Track resistance can be either linear or
  logarithmic
• Reciprocating Saw
• Wiper moves along the track and decreases the
  resistance, which in turn, gives more voltage to
  the DC motor

References http//www.allaboutcircuits.com/vol_6
/chpt_3/6.html http//www.kpsec.freeuk.com/compone
nts/vres.htm
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Potentiometers (Rotary)

• Associated with lower current ratings
• Wiper rotates around a resistive metal strip to
  vary resistance from 0 to the maximum resistance
• Track orientation is rotational
• Usually used for fine-tuning a circuit (digital
  displays can be added to show number or rotations
  of dial)

References http//www.allaboutcircuits.com/vol_6
/chpt_3/6.html http//www.kpsec.freeuk.com/compone
nts/vres.htm
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Applications
Figure 1 Technics SH-MZ1200 Mixer

• Potentiometer (Rotary)
• Volume controls
• Audio amplifiers
• Any other dial-based design

• Rheostat (Linear Potentiometer)
• Light dimmer switches (digital versions are now
  used)
• Variable speed switches (i.e. reciprocating saw)
• Faders and sliders on a mixer

References http//en.wikipedia.org/wiki/Resistor
http//www.kpsec.freeuk.com/components/vres.htm
http//www.aage.dk/default.asp?page/Shoppingsyste
m/vare.asp?varenr26398
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Conclusion and References

• Conclusion
• Several different types of variable resistors
  allow them to be used more widely in applications
• Linear variable resistor in a switch allows
  reciprocating saw to have a variable speed switch

• References
• AAGE. Technics SH-MZ1200. Accessed on November
  13, 2005 http//www.aage.dk/default.asp?page/Shop
  pingsystem/vare.asp?varenr26398.
• Potentiometer as a Voltage Divider. Accessed on
  November 13, 2005 http//www.allaboutcircuits.com/
  vol_6/chpt_3/6.html.
• Hewes, J. Variable Resistors. Accessed on
  November 13, 2005 http//www.kpsec.freeuk.com/comp
  onents/vres.htm.
• Resistor. Accessed on November 13, 2005
  http//en.wikipedia.org/wiki/Resistor.