Electro-cam PS-6144 Series Bedienungsanleitung PDF herunterladen (Seite 5)

1-1 Introduction

Mechanical Cam Switches

Mechanical Cams The PS-6144 Programmable Limit Switch electronically simulates mechanical cam

switches. A cam switch consists of a roller limit switch whose arm rides on a cam as

shown in Figure 1. The cam shaft is driven by a machine at a 1:1 ratio, so that the cam

switch turns on and off at specific positions in the machine cycle. Cam limit switches

have the following disadvantages:

• The roller, the cam, and the limit switch wear out.

• The machine must be stopped during adjustment.

• On/off patterns are limited, and changing the pattern may require replacement of one

cam with another. For example, a cam that switches on and off twice in one revolu-

tion would need to be replaced with a different cam if three on/off pulses per revolu-

tion were required.

• They cannot run at high speeds because of contact bounce and excessive mechani-

cal wear.

Figure 1—Basic Cam Switch

Programmable Limit Switches

PS-6144’s & Resolvers The PS-6144 Programmable Limit Switch uses a resolver (see Figure 2 on page 2)

instead of a cam to indicate machine position. A resolver uses fixed and rotating coils of

wire to generate an electronic signal that represents shaft position. The resolver is

usually coupled to a machine shaft at a 1:1 ratio so that one resolver shaft rotation

corresponds to one machine cycle. Resolvers have no brushes, contacts, or any fric-

tional moving parts to wear out.

Based on the resolver signal, the PS-6144 Programmable Limit Switch turns electrical

circuits, or “Outputs,” on and off, simulating the mechanical roller limit switch. Because

the combination PS-6144/resolver system is completely electronic and has no frictional

parts, it offers several advantages over mechanical cam switches:

• Long service life with no parts to wear out.

• “On” and “off” points can be adjusted instantly from the keypad; there are no cams to

rotate or replace.

• Adjustment is possible with the machine running or stopped.

• Programmable logic allows complex switching functions that are impossible with

mechanical cams.

• Operation at speeds up to 3000 RPM.

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Electro-cam PS-6144 Series Bedienungsanleitung Seite 5