Reciprocating Saw - Variable Resistors and Switches By: Ryan Kim

1. Reciprocating Saw - Variable Resistors and Switches By: Ryan Kim

2. Contents • Introduction to the Saw and Variable Resistors • Different Types of Variable Resistors • Rheostats • Potentiometers • Applications • Conclusion and References

3. Introduction Reference: http://www.ryobitools.com

4. Introduction (Cont’d) 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

5. Introduction (Cont’d) 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

6. 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.htmlhttp://www.kpsec.freeuk.com/components/vres.htm

7. 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.htmlhttp://www.kpsec.freeuk.com/components/vres.htm

8. 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.htmlhttp://www.kpsec.freeuk.com/components/vres.htm

9. 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/Resistorhttp://www.kpsec.freeuk.com/components/vres.htm http://www.aage.dk/default.asp?page=/Shoppingsystem/vare.asp?varenr=26398

10. 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=/Shoppingsystem/vare.asp?varenr=26398. • “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/components/vres.htm. • “Resistor.” Accessed on November 13, 2005 http://en.wikipedia.org/wiki/Resistor.