54M-1BB-1AL Grayhill Inc, 54M-1BB-1AL Datasheet - Page 3

• Manufacturer Part Number: 54M-1BB-1AL
• Description: 54M30-01-1-03N & 01-1-12N-C T, Military 85&deg
• Manufacturer: Grayhill Inc

Specifications of 54M-1BB-1AL

• , 30°: , 1 Deck, 1 Pole/deck, 2 Positions/pole, Non-shorting & 1 Deck, 1 Pole/deck, 2 Positions/pole, Non-shorting, 54M-1BA-1BA
• Lead Free Status / Rohs Status: Compliant

F-3
CATALOG RATINGS
Are catalog ratings misleading? In most cases,
yes. Load and life ratings shown in most catalogs
are usually invalid for most applications. This
results from the complex interplay of such factors
as environment, duty cycle, life limiting or failure
criteria, actual load, etc. Circuit designers should
be aware of these factors, and the effect they
have on the useful life of the switch in their
applications.
The problem of switch rating arises from the
wide variety of requirements placed on the
switch. This includes various applications, and
the sensitivity of the switch to change in
requirements. If we attempted to establish life
ratings for all possible applications, we would
have an almost infinite variety of ratings.
To simplify the problem, switch manufacturers,
switch users, and the military, have established
certain references for ratings. These include
loads, life requirements, environments, duty
cycles, and failure criteria. These references
are arbitrarily established. But, they allow you to
compare different switch designs. They do not,
however, match the actual requirements for
most applications.
The curves shown here are an example of some
of the life load curves. These curves are life load
characteristics of the Grayhill 42M and 44M
switches. Note that the curves consider only
two voltage sources and two types of loads.
These voltages and loads are, however,
considered as standards for testing procedures
by the industry.
Curve data is based on tests conducted at
sea level, 25°C and 68% relative humidity.
Cycle = 360° rotation and return. Cycling
rate is 10 cycles per minute. Switch rating is
for non-shorting contacts.
1.7
1.5
1.2
1.0
.75
.50
.20
7
6
5
4
3
2
1
0
0
Grayhill, Inc. • 561 Hillgrove Avenue • LaGrange, Illinois
0
0
(2.8 HENRIES)
INDUCTIVE
10
10
VOLTAGE 115 VAC
VOLTAGE 30 VDC
25
25
CYCLES x 1,000
CYCLES x 1,000
RESISTIVE
RESISTIVE
Rotary Switch Engineering Information
50
50
These curves allow you to predict the expected
life of the switch once you know the voltage,
current and type of load. Also note that each
cycle is approximately a 360° of rotation and a
return. For a ten position switch this would be a
rotation from position 1 to position 10 and back
to 1. This cycle runs approximately ten times a
minute. Thus testing causes more electrical
and mechanical wear than what the switch
incurs in actual use.
Summary
The life and load ratings in this and other
catalogs are probably not totally valid for your
application. The bright side of the picture is that
in most applications the switch will perform
better than its ratings. This is because the
standard industry test conditions are more
stringent than those found in most applications.
This difference can be very dramatic. For
example, Grayhill’s 42A and 44A Series Rotary
Switches, are rated at 1 ampere (115 Vac
resistive). However, they will operate at 5
amperes in many applications. To see how
some major factors influence switch
performance, read on.
USEFUL LIFE CRITERIA
The “useful” life of a switch in your application
depends on what you demand of it. This includes
parameters such as contact resistance,
insulation resistance, torque, detent feel,
dielectric strength, and many other factors. For
example, a contact resistance of 50 milliohms
may be totally unusable in certain applications
such as a range switch in a micro-ohm meter. In
other applications a contact resistance of 5
ohms may be perfectly satisfactory.
In establishing “useful” life for a switch in your
application, you must first determine “failure
criteria,” or “end of life” parameters. At what
level of contact resistance, dielectric strength,
etc., is the switch no longer acceptable for your
application?
Most switches are acceptable on all parameters
when new. There is a gradual deterioration in
performance with life. The rate of deterioration
varies greatly with basic switch design. Often,
circuit designers select a switch on the basis of
its performance when new. This is a mistake.
The performance of the switch after several
years of equipment use is more significant. To
estimate this, first determine the life limiting or
failure criteria for your application. In most uses,
important life-limiting (failure) criteria include
the following parameters:
Contact Resistance
Insulation Resistance
Dielectric Strength
Actuating Force
60525-5997 • USA • Phone: [phone] • Fax: [phone] • www.grayhill.com
Contact Resistance
This is the resistance of a pair of closed contacts.
This resistance effectively appears in series
with the load. Typical values are in the range of
a few milliohms for new switches. These values
usually increase during life. The rate of increase
is greatly affected by the voltage, current, power
factor, frequency, and environment of the load
being switched. Typical industry standard “end
of life” criteria for this parameter are:
Contact resistance can be measured by a
number of different methods. All of them are
valid depending upon the switch application
and the circuit. Grayhill uses the method in
applicable military specifications. This method
specifies an open circuit test voltage and a test
current. The voltage drop across the closed
contacts is measured. The contact resistance is
determined by Ohm’s Law from the test current
and the measure voltage drop. MIL-S-3786,
MIL-S-6807 and MIL-S-8805 require a maximum
open circuit test voltage of 2 Vdc; they require
a test current of 100 milliamperes. MIL-S-83504
requires a maximum test voltage of 50 millivolts
and a test current of 10 milliamperes.
When a switch is rated to make and break 5 or
more amperes, there is a difference. Contact
resistance is determined by measuring the
voltage drop while the switch is carrying the
maximum rated current.
The voltage drop that occurs across the contacts
determines, in part, the contact temperature. If
the temperature rise of the contacts is sufficient,
it affects contact material. A chemical reaction
will take place that can cause an insulating film
to appear on the contacts. This film is present
between the contacts during the next switching
operation. This film formation can cause failure
due to increasing contact resistance. For
switching of very low voltages and currents, this
resistance may be the failure criteria.
MIL-S-3786:
MIL-S-6807:
MIL-S-8805:
MIL-S-83504:
20 milliohms
(Rotary Switches)
20 milliohms
(Snap Pushbuttons)
40 milliohms
(Pushbuttons)
100 milliohms
(DIP Switches)