Bulletin No. PRS1-H
Drawing No. LP0026
Released 8/05
Tel +1 (717) 767-6511
Fax +1 (717) 764-0839
www.redlion.net
MODEL PRS1 - PLUG-IN SPEED SWITCH
5 RANGES, FROM 0.1 Hz to 10 KHz
OVER-SPEED, UNDER-SPEED, OR ZERO-SPEED DETECTION
4 OPERATING MODES
REPEATABILITY TO 1/2% OF MAX. RANGE
LED RELAY “ON” INDICATOR
PROGRAMMABLE INPUT CIRCUIT ACCEPTS OUTPUTS FROM
A VARIETY OF SENSORS
DESCRIPTION
The PRS1 is a versatile, reliable and economical solution to most machine
speed switching problems. It is not affected by overspeeding and will operate in
either direction of rotation.
The heart of the PRS1 is a solid-state CMOS logic circuit, that continuously
measures the elapsed time between successive trailing edges
(negative going)
of
an incoming pulse train or waveform. It compares this time with an adjustable
set-point reference and determines if the period of the waveform is longer
(underspeed)
or shorter
(overspeed)
than the set-point reference.
The internal relay is energized during
“normal”
operation and can be set to
de-energize on either under or overspeed by a programming switch. The unit
can be connected for simple over or underspeed detection or for latch/trip-off
operation in a machine STOP/START circuit.
The PRS1 features built-in hysteresis
(differential between pick-up and drop-
out)
of 5% of set-point speed. This prevents the output relay from chattering
when operating at or near the set-point speed. The set-point control is a 20-turn
screwdriver adjustment accessible at the top of the unit with a 10:1 adjustment
range. An LED indicates when the relay is energized. A built-in +12 VDC
regulated power supply, furnished power for the internal circuit and for external
sensor excitation.
The plug-in module mates with a heavy duty, CSA approved base mounting
socket with pressure clamp screw terminals that accept stripped wires without
lugs. Closed back construction allows mounting directly on metal panel without
an insulation barrier.
SPECIFICATIONS
1.
PRIMARY SUPPLY VOLTAGE:
Available for 115 or 230 VAC ±10%,
50/60 Hz; 2.5 VA
(See Ordering Information).
2.
SENSOR OUTPUT POWER:
+12 VDC ±5% regulated, 60 mA max.
3.
SIGNAL INPUT CHARACTERISTICS:
See
“PRS1 Input Circuits,
Sensor Connections & Configuration Switch Set-ups”
section.
4.
FREQUENCY RANGES AVAILABLE:
Available in 5 ranges, each range
providing a relay pick-up or drop-out adjustment span of 10:1.
(See Ordering
Information)
5.
RELAY CONTACT OUTPUT:
FORM
“C” (SPDT)
contacts max. rating 5
amps @ 120/240 VAC or 28 VDC
(resistive load),
1/8 H.P. @ 120 VAC
(inductive load).
The operate time is 5 msec nominal and the release time is
3 msec nominal.
6.
RELAY LIFE EXPECTANCY:
100,000 cycles at max. rating.
(As load
level decreases, life expectancy increases.)
7.
RESPONSE TIME:
Response time is equivalent to the period of set-point
frequency, plus 5 msec for relay pickup or plus 3 msec for relay dropout.
8.
OPERATING TEMPERATURE RANGE:
0 to 60°C.
9.
WEIGHT:
PRS1 PLUG-IN MODULE - 8 oz (226.8 g).
WARNING:
SPEED SWITCHES MUST NEVER BE USED AS PRIMARY
PROTECTION AGAINST HAZARDOUS OPERATING CONDITIONS.
Machinery must first be made safe by inherent design, or the installation of
guards, shields, or other devices to protect personnel in the event of a
hazardous machine speed condition. Then a speed switch may be installed to
help prevent the machine from entering the unsafe speed condition.
DIMENSIONS In inches (mm)
1
PRS1 APPLICATIONS
The following guidelines and considerations will help to assure the best
performance when applying the PRS1 Speed Switch.
1.
SENSOR AND FREQUENCY RANGE SELECTION
(See “PRS1 Sensor & Frequency Range Selection” section.)
2.
RESPONSE TIME
The PRS1 has an internal adjustable timer whose
“time-out”
period is
determined by the set-point adjustment. In operation, this timer is reset
(retriggered)
at the start of each signal cycle and the internal logic circuitry
monitors whether the signal cycle concludes before time-out occurs
(overspeed)
or if time-out occurs before conclusion of the signal cycle
(underspeed).
This operating scheme results in an inherent delay in output
switching response which is insignificant at moderate and higher frequencies,
but can be appreciable at low frequencies. For example, with the PRS10011
(Range 0.1 to 1 Hz)
set to the minimum range, underspeed output will not
occur until 10 sec after the initiation of the last signal cycle. Overspeed
response is directly related to the period of the signal frequency and will be
faster, depending on the amount of overspeed.
The inherent delay at low frequencies can be an advantage when the PRS1 is
applied as a zero-speed switch. However, for fast response, a higher
frequency unit with an appropriate sensor arrangement should be used. This
can often be accomplished simply by moving the sensor to a higher speed
shaft, or by going directly to the drive motor shaft with an ARCJ Ring Sensor
Kit.
(See Sensor Section of the RLC Catalog.)
3.
ERRATIC OR IRREGULAR SHAFT MOTION
Since the PRS1 operates by timing each successive signal cycle, relay chatter
can be experienced when the set-point speed is adjusted close to the running
speed and the motion of the sensor shaft is irregular. For example, if a sensor
detects teeth of the driven sprocket in a chain drive with a good deal of chain
slack, the period between adjacent signal cycles can vary as much as 2:1 as the
driven sprocket alternately overhauls and takes up slack. This does not present
a problem if the set-point is adjusted at 5 or 10% of running speed, but if the
set-point is to be 90% of running speed, the PRS1 output will chatter as the
chain picks up and gives out slack. Again, the solution to this problem is to
locate the sensor at a point in the drive train where the motion is smooth.
Note: The PRS1 has built-in hysteresis of 5% of set-point speed, i.e. underspeed
output occurs at 95% of the overspeed set-point. This allows a set-point near
running speed provided shaft motion is reasonably smooth.
4.
OVERSPEED OPERATION AND HI-FREQUENCY SENSOR
DROPOUT
All ranges of PRS1 units can be operated in the overspeed condition up
through 10 KHz without experiencing operational discontinuities. However,
when subject to higher input signal frequencies
(12 to 15 KHz),
signal roll-
off will occur in the input circuit and the output will transfer to underspeed
as if the signal had dropped to zero frequency.
Sensor signal drop-out at high frequencies will also cause a false underspeed
output. Caution is advised when selecting proximity, photo-electric, and other
sensors that have limited high frequency ratings, to ensure that their maximum
output frequency limit is not exceeded at maximum machine speed.
OPERATING MODES
MODE A:
LOW SPEED OPERATE, OVERSPEED
Internal relay is energized at all speeds below the set-point
speed, and de-energizes when speed exceeds the set-point
speed. Relay again energizes when speed drops approximately
5% below the set-point speed.
MODE B:
HIGH SPEED OPERATE, UNDERSPEED
DROPOUT
Internal relay is de-energized at all speeds below the set-
point speed, and energizes when the speed exceeds the set-
point. The relay again de-energizes when the speed drops
approximately 5% below the set-point.
MODE C:
LATCH, HIGH SPEED OPERATE,
UNDERSPEED DROPOUT
Pushing the Start button energizes the internal relay and
starts the machine. When operating speed is reached, the relay
stays latched with the Start button released. If the machine
speed drops below the set-point, the relay unlatches, sounding
the alarm and stopping the machine.
MODE D:
LATCH, LOW SPEED OPERATE, OVERSPEED
DROPOUT
Pushing the Start button energizes and latches the relay and
starts the machine. The relay stays latched as long as machine
operates below set-point speed. If the machine exceeds the
set-point speed, the relay unlatches, sounding the alarm and
stopping the machine.
ORDERING INFORMATION
PART NUMBERS FOR AVAILABLE SUPPLY VOLTAGES
MODEL NO.
DESCRIPTION
A.C. POWER
0.1-1 Hz
1-10 Hz
10-100 Hz
100-1 KHz
1 K-10 KHz
PRS1
__
Speed Switch
Socket, 12-Pin
115 VAC
230VAC
PRS10011
PRS10012
2300200
PRS10101
PRS10102
PRS11011
PRS11012
PRS11021
PRS11022
PRS11031
PRS11032
2
PRS1 INPUT CIRCUITS, SENSOR CONNECTIONS & CONFIGURATION SWITCH SET-UP
The Model PRS1 Speed Switch uses the circuit shown on the right. The
circuit uses a comparator amplifier connected as a Schmidt trigger circuit to
convert the input wave form into the pulse form required for proper circuit
operation. Three set-up switches are used to configure the input circuit to accept
signals from a wide variety of sources, as follows:
S1 - ON:
Connects a 1 K pull-down resistor for sensors with sourcing output.
(Maximum sensor output current is 12 mA @ 12 V output.)
S2 - ON:
Sets bias of input to trigger at V
IL
= 2.5 V, V
IH
= 3.0 V; for logic level
signals.
OFF:
Sets the bias of input to trigger at V
IL
= 0.25 V, V
IH
= 0.75 V; for
increased sensitivity when used with magnetic pickups.
S3 - ON:
Connects a 3.9 K pull-up resistor for sensors with current sinking
output. (Maximum sensor current is 3 mA.)
OTHER CHARACTERISTICS & SPECIFICATIONS
Maximum Operating Frequency:
10 KHz with maximum pulse width ON
and OFF times of 50 µsec.
Maximum Input Voltage:
Pin 7
(Input)
may be driven from an external voltage
up to ±90 V provided S1 and S3 are “OFF” to disconnect internal load
resistors.
(Maximum Input Voltage with S1 “ON” is ±16 V)
Input Impedance:
With S1 and S3 “OFF”, the resistive input impedance
exceeds 1 Megohm, as long as Pin 7 voltage is greater than zero and less
than +12 V.
Paralleling With a Counter and/or Rate Indicator Inputs:
The PRS1 can be
operated from a common sensor with current sinking output that is also used
to drive the input of a Counter or Rate Indicator. Connect Pin 8 to the
Common Terminal and Pin 7 to the Input Terminal of the Counter or Rate
Indicator; set S1 and S3 “OFF” and S2 “ON”. DO NOT PARALLEL
CONNECT THE +12V OUTPUTS (Pin 9) OF PRS1 UNITS WITH THE
+12V OUTPUTS OF COUNTERS, DITAKS, OR OTHER PRS1 OR PRA2
UNITS. These units have regulated supplies that will not load-share. Multiple
inputs cannot be operated from sensing switches, 2-wire proximity sensors,
or magnetic pickups.
CONNECTIONS & CONFIGURATION SWITCH SET-UP FOR VARIOUS SENSOR OUTPUTS
MAGNETIC PICKUPS
SENSORS WITH CURRENT SINK OUTPUT (NPN O.C.)
RECOMMENDED RULES FOR MAGNETIC PICKUP CONNECTIONS
1. Mount the PRS1 in a relatively “noise-free” environment, away from motor starters,
control relays, or other sources of electrical interference.
2. Use 2-wire shielded cable for magnetic pickup signal leads.
3. Never run signal cable in conduit, troughs, or cable bundles with power carrying
conductors.
4. Connect the shield to the common Terminal “8” at the input of the PRS1. DO NOT
connect the shield at the pickup end, leave it “open” and insulate the exposed shield to
prevent electrical contact with the frame or case. (Shielded cable, supplied on some
RLC magnetic pickups, has open shield on pickup end.)
RLC SENSOR MODELS:
ASTC, LMPC, PSAC, LSC, RPGC, RPGB, RPGH, RPGQ, HESS, etc.
SENSORS WITH CURRENT SOURCE OUTPUT (PNP O.C.)
2-WIRE PROXIMITY SENSORS
A.C. INPUTS FROM INVERTERS, A.C.
TACHOMETERS GENERATORS, ETC.
SWITCH CONTACT INPUT
RLC SENSORS WITH -EF OUTPUT
R - Resistor to limit input current to 5 mA peak
C - Filter cap required when input A.C. has “ringing”
characteristics as with inverters.
A.C. Power sources exceeding 50 V output
should be coupled with an isolation transformer.
INPUT FROM CMOS OR TTL
RLC SENSOR MODEL: LMPEC
The addition of two external resistors and a capacitor
allows the PRS1 to be operated from input signals
generated by a switch contact. The external RC network
forms a Low-Pass Filter which operates in conjunction
with the hysteresis of the input circuit to “De-bounce” the
Switch Contact signal.
Use of the Low-Pass RC Filter places a high-speed
restriction on the circuit, and it cannot be used at
frequencies of more than 200 to 300 cps. However, Switch
Contact input is normally limited to low speed operation,
so this does not impose a serious restriction.
3
PRS1 SENSOR & FREQUENCY RANGE SELECTION
The PRS1 Speed-Switch normally operates from a variable frequency signal
supplied by a machine mounted sensor. The sensor signal varies in frequency in
direct proportion to machine speed, and may be a sinusoidal, triangular, square,
or pulse-type waveform. The sensor arrangement can take a variety of forms
such as a Magnetic Pickup or Proximity Sensor detecting passing teeth on a
sprocket or gear, a Photo-Electric Scanner viewing passing pulley spokes, a
Rotary Pulse Generator coupled to a machine shaft, or a Length Sensor driven
by a web or ribbon of material passing through the machine. (See Sensor
Section of the catalog for more information on sensors.)
Since the PRS1 operates from the frequency content of the incoming signal,
the response time of both devices is also related to the signal frequency. This
gives rise to the cardinal rule of selecting a sensor arrangement:
WHEN RESPONSE TIME IS IMPORTANT, SELECT A SENSOR
ARRANGEMENT & LOCATION THAT WILL PROVIDE A HIGH
FREQUENCY OUTPUT AT OPERATING SPEED.
INTERMEDIATE SHAFT SPEEDS (10-1000 RPM)
- Magnetic Pickups, the
LMPC, RPG’s and some Proximity Sensors are appropriate at these speeds.
HIGH-SHAFT SPEEDS (1000 RPM and up)
- Magnetic Pickups, the LMPC
and RPG’s are usually the best choices.
FOR LINEAR SPEEDS ON PAPER WEBS, TEXTILE, RIBBON, STRIP
AND WIRE
- The LSC Length Sensor may prove desirable.
CAUTION: When selecting a sensor for operation at any speed, make sure the
sensor is also capable of delivering an output for the entire speed range up
through maximum machine speed.
DETERMINING SENSOR FREQUENCY OUTPUT &
SELECTING THE PROPER FREQUENCY RANGE
Machine speeds are normally expressed in revolutions/minute
(RPM)
while
the PRS1 has adjustable frequency ranges in cycles/second or Hz. In addition,
sensor arrangements usually deliver a number of signal cycles or pulses for
each shaft revolution. The following formula provides a convenient way to
relate these variables:
RPM x PPR
FRQ (CPS or Hz) =
60
When a PRS1 application is first contemplated, it seems to be natural to think
in terms of applying the sensor to the low speed end of the power drive train. In
some cases this may be the only practical location for the sensor, and if fast
response is needed from the PRS1, a sensor arrangement capable of delivering
a high number of cycles or pulses/revolution
(PPR)
will be required. In a great
number of applications however, generating a higher frequency sensor signal is
simply a matter of locating the sensor on a intermediate or high speed shaft such
as directly on the drive motor shaft.
Another advantage of moving the sensor location up toward the high speed
end of the drive train is that the shaft rotary motion is usually much smoother
and more regular. Slow speed shafts will often rotate irregularly due to gear
backlash, “slop” in couplings, or slack in chain drives. This irregular motion
can have an adverse effect on the resulting output, especially when using the
PRS1 to perform a speed switching function near normal running speed.
WHERE:
RPM
is the speed of the shaft where the sensor is located in revolutions
per minute.
PPR
is the number of pulses (or cycles) produced by the sensor for one
shaft revolution.
EXAMPLE 1
A machine is to be equipped with a PRS1 Speed Switch. A 42-tooth timing
belt pulley is available in the power drive train, and an LMPC is to be used to
sense passing teeth. The PRS1 set-point is to be adjusted to provide overspeed
output when the timing belt pulley reaches 730 RPM. What should the
frequency range of the PRS1 be?
730 RPM x 42 PPR
FRQ @ set-point =
= 511 Hz
60
SELECTING AN APPROPRIATE SENSOR ARRANGEMENT
There are no exact rules governing the selection of a sensor arrangement
since machine geometry and conditions can vary widely from one application
to the next. However, the following generalized criteria will prove useful as
guidelines toward selecting the best sensor arrangement.
(See Sensor Section of
the catalog for more information.)
ULTRA-LOW SHAFT SPEEDS (10 RPM or less)
- Proximity Sensors, Photo-
Electric Scanners, or Rotary Pulse Generators, are usually the best selections.
In most ultra-low speed applications, it is advisable to provide as many pulses
per revolution as possible
(high PPR)
to get acceptable response times.
LOW-SHAFT SPEEDS (10-100 RPM)
- LMPC (Super-Sensitive Magnetic
Pickup), Proximity Sensors, Photo-Electric Scanners and RPG’s can usually
be applied in this speed range.
SELECT:
PRS11021 (or PRS11022 for 230 VAC) which has an adjustable
range of 100-1000 Hz.
LIMITED WARRANTY
The Company warrants the products it manufactures against defects in materials and workmanship for a period limited to two years
from the date of shipment, provided the products have been stored, handled, installed, and used under proper conditions. The
Company’s liability under this limited warranty shall extend only to the repair or replacement of a defective product, at The
Company’s option. The Company disclaims all liability for any affirmation, promise or representation with respect to the products.
The customer agrees to hold Red Lion Controls harmless from, defend, and indemnify RLC against damages, claims, and expenses
arising out of subsequent sales of RLC products or products containing components manufactured by RLC and based upon personal
injuries, deaths, property damage, lost profits, and other matters which Buyer, its employees, or sub-contractors are or may be to
any extent liable, including without limitation penalties imposed by the Consumer Product Safety Act (P.L. 92-573) and liability
imposed upon any person pursuant to the Magnuson-Moss Warranty Act (P.L. 93-637), as now in effect or as amended hereafter.
No warranties expressed or implied are created with respect to The Company’s products except those expressly contained herein.
The Customer acknowledges the disclaimers and limitations contained herein and relies on no other warranties or affirmations.
Red Lion Controls AP
Red Lion Controls
20 Willow Springs Circle
York PA 17402
Tel +1 (717) 767-6511
Fax +1 (717) 764-0839
Red Lion Controls BV
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NL - 3821 BR Amersfoort
Tel +31 (0) 334 723 225
Fax +31 (0) 334 893 793
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