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PS-2252-12-TP1
Net Forward Encoder Interface
The PS-2252-12-TP1 Net Forward Encoder Interface (NFEI) accepts inputs from the A and B channels of a standard
quadrature encoder. The NFEI outputs a pulse for each forward direction transition of the encoder, but reverse direction
transitions result in no pulses. Furthermore, following reverse movement, no output pulses result from forward movement until the encoder position exceeds the furthermost forward position reached before the reverse movement. The
NFEI rejects jitter resulting from mechanical oscillation at a transition point of the encoder with the system at a zero
average velocity. Note: If more than 65,535 consecutive reverse encoder transitions are made, an Overflow output on
the NFEI is activated indicating that the reverse counter has lost track of reverse transitions. A reset input allows clearing
the reverse counter in order to restart.
Inputs
Channel A, Channel B: Standard Quadrature encoder A and B channels.
Reset: Resets internal reverse counter when high-level.
Outputs
Out 0: High-going pulse indicates forward increment of encoder.
Overflow: High level indicates overflow of internal 16-bit reverse counter.
Voltage Levels
Channel A & B Inputs: 5-15 VDC.
Reset Input On voltage: Optically isolated, 4.0 VDC min @ 10 mA.
Out 0 & Overflow Outputs: 7406 open collector.
VOL = 0.4V max @ IOL = 16 mA. VOH = 30V max.
Timing
Time Between Encoder Channel Edges: 17 microseconds minimum.
Reset Input Pulse Width: 50 microseconds minimum.
Output Pulse Width: 20 microseconds minimum.
Configuration
CW/CCW: Dip switch sets forward rotation direction.
1st switch ON = CW. 1st switch OFF = CCW. Switches 2-6 are not used.
Power Supply
Supply Voltage: 11-15 VDC.
Supply Current: 90 mA @ 12 VDC.
Environment
Operating Temperature: 0° to 55°C (32° to 131°F)
Storage Temperature: -40° to 70°C (-40° to 160°F)
Humidity: 95% maximum relative non-condensing.
Mounting
Brackets accept EN-50035 (''G'' profile) or EN-50022 (''Top Hat'' profile) DIN rail.
EN-50035 (''G'' profile) included.
13647 Metric Rd • Roscoe, IL 61073 USA • 815/389-2620 • FAX 815/389-3304 • 800-228-5487 (U.S.A. and Canada)
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Internal Encoder Count
Mechanical oscillation of the encoder is properly tracked by the NFEI as long as the minimum
time between encoder channel edges is within specification, as illustrated below.
For Example:
A
B
17 microseconds minimum
A quadrature encoder with 1000 pulses/revolution has 4000 edges
If this encoder revolves at 800 rev/min:
800 rev . 1min . 4000 edges = 53,333 edges
min 60 sec 1 rev sec
This implies 18.75 microseconds
Thus, the upper speed limit for a 1000 rpm quadrature encoder is 800 rpm.
Installation
Connect the NFEI using the Terminal Block Wiring illustration below.
Reset Input, Sourcing Reset Input, Sinking
Reset
Reset Input Common Reset Input Common
-
S
C
Not Used
Common
Reset
RC
S
Shield
-
+11-15
VDC IN
+
Overflow
Out 0
CHN B (from encoder)
CHN A (from encoder)
OBA
R
revolution
edge
Reset
OB
+
Mechanical Switch Mechanical Switch
A
R
-
S
C
OB
+
OR OR
A
Solid State Switch
PNP Transistor NPN Transistor
Solid State Switch
Troubleshooting
Symptom: Output does not turn on with encoder movement.
a. Verify that the voltage on the + and - terminals of the NFEI terminal block is between 11 and 15 VDC.
b. Verify with oscilloscope that proper encoder signals (per Internal Encoder Count illustration) are present at the Chn A
and Chn B terminals of the NFEI terminal block, and that the voltage levels are TTL compatible (logic 0 less than 0.8 v
and logic 1 greater than 2.0 v). If not, there is a problem with the encoder or encoder cable. If the encoder signals are
proper, the problem is internal to the NFEI, and the NFEI should be exchanged.
c. Verify that the configuration DIP switch setting agrees with the actual direction of encoder movement. If the Overflow
output is at a TTL high level, then the encoder has moved more than 65,535 counts in the reverse direction, and the
internal reverse count logic of the NFEI will not be accurate. Move encoder to “0” position and reset NFEI.
d. Verify with oscilloscope the status of the Out 0 terminal on the NFEI terminal block. If, after the reverse counts have
been counted out, there are pulses when the encoder moves in the configured direction, then the problem is not in the
NFEI.
800-228-5487 (U.S.A. and Canada) • Web Site: www.electrocam.com • email: ecam@electrocam.com
PRINTED IN U.S.A
269 12/98
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