A-B 1746-HSCE2 Multi-Channel High-Speed Counter

Hardware Features 

The module’s hardware features are illustrated below.

Installing the Module

1. Make sure your SLC power supply has adequate reserve current capacity.

The  module requires 250 mA at +5V dc. 

2. Align the full-sized circuit board with the chassis card guide as shown below.

The first slot of the first chassis is reserved for the processor.

3. Slide the module into the chassis until the top and bottom latches catch. 

To  remove the module, press the release clips at the top and bottom of the module  and slide it out. 

4. Cover all unused card slots with the Card Slot Filler, catalog number 1746-N2.

Important Wiring Considerations

Use the following guidelines when planning the system wiring for the module:

• Install the SLC 500 system in a NEMA-rated enclosure.

• Disconnect power to the SLC processor and the module before wiring.

• Make sure the system is properly grounded.

• Group this module and low-voltage DC modules away from AC I/O or 

high-voltage DC modules.

• Shielded cable is required for high-speed input signals A, B, and Z. Use 

individually shielded, twisted pair cable lengths up to 300 m (1000 ft.).

• Shields should be grounded only at one end. Ground the shield wire outside 

the module at the chassis mounting screw. Connect the shield at the encoder 

end only if the housing is isolated from the motor and ground.

• If you have a junction in the cable, treat the shields as a conductor at all 

junctions. Do not ground them to the junction box.

Considerations for Reducing Noise

In high noise environments, the 1746-HSCE2 inputs may accept “false” pulses, 

particularly when using low frequency input signals with slowly sloping pulse 

edges. To minimize the effects of high frequency noise on low frequency signals, 

the user can do the following:

• Identify and remove noise sources.

• Route 1746-HSCE2 input cabling away from noise sources.

• Install low pass filters on input signals. Filter values are dependent on the 

application and can be determined empirically.

• Use devices which output differential signals, like differential encoders, to 

minimize the possibility that a noise source will cause a false input.

Electronic Protection

The electronic protection of the 1746-HSCE2 has been designed to provide 

protection for the module from short-circuit and overload current conditions. The 

protection is based on a thermal cut-out principle. In the event of a short circuit or 

overload current condition on an output channel, all channels turn off within 

milliseconds after the thermal cut-out temperature has been reached. 

IMPORTANT

The module does not provide protection against reverse 

polarity wiring or wiring to AC power sources. Electronic 

protection is not intended to replace fuses, circuit breakers, or 

other code-required wiring protection devices.

Auto Reset Operation

IMPORTANT

1746-HSCE2 outputs perform auto-reset under overload 

conditions. When an output channel overload occurs as 

described above, all channels turn off within milliseconds 

after the thermal cut-out temperature has been reached. While 

the overcurrent condition is present, the module tries resetting 

the outputs at intervals of 500 ms. If the fuse cools below the 

thermal cut-out temperature, all outputs will auto-reset and 

resume control of their external loads as directed by the 

module until the thermal cut-out temperature is again reached.

Removing power from an overloaded output channel would 

also allow the fuse to cool below the thermal cut-out 

temperature, allowing auto-reset to occur when power is 

restored. The output channel then operates as directed by the 

module until the thermal cut-out temperature is again reached.

To avoid auto-reset of output channels under overload 

conditions, monitor the fuse blown status bit (FB1) in the 

module’s status file and latch the output off when an 

overcurrent condition occurs. An external mechanical fuse 

can also be used to open an output circuit when it is overloaded.

Short-Circuit/Overload Current Diagnostics

If a short-circuit or overload current condition occurs on an output channel:

1. The FLT LED flashes, provided that power is applied to the module. 5V dc via 

backplane and load power via an external supply is required.

2. Fuse status bit (FB1) is set (1) when the fuse is tripped. The module tries to 

reset the outputs at intervals of 500 ms. During each retry, the fuse status bit is 

reset (0). After the overload condition is corrected, the fuse status bit resets (0) 

automatically.

When FB1 is set, outputs 0 through 4 will not function.

3. All output channels will be turned off in the case of a short-circuit or overload condition.

Recovery from Channel Shutdown

1. Remove the SLC 500 system power and correct the conditions causing the 

short-circuit or overload current condition.

2. Restore the SLC 500 system power. The module automatically resets and 

resumes control of the output channel and associated load.