Connecting encoder to High Speed Input, not Pulse Input?

Hi,

I came across a project using Mitsubishi (FX2N48-MR) PLC where they connect 3 units of encoder (Omron E6B2-CWZ6C) to the PLC Digital Input points (which they claimed to be high speed input points). I've not go thru deeply into the machine nor justify on the performance of the machine, but the programmer tell me it's working fine.

If we can connect the encoder to high speed input, instead of pulse input module, that will save a lot of money.

Someone experience pls advise me Thank you.

A lot of manuafacturers of the shoe box type (brick) PLCs have one or 2 of the inputs able to be used as high speed inputs.
Rggards Alan Case

Alan Case said:

A lot of manuafacturers of the shoe box type (brick) PLCs have one or 2 of the inputs able to be used as high speed inputs.
Rggards Alan Case

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Alan, yeah but can we connect encoder to high speed input instead of pulse input module built for encoder? Can they work?

I have quite often, it has to be the right sort of encoder. ie you can't connect one of the sine/cos types to a high speed input.
Also the khz ratings of the inputs are not that high sometimes.
Check the spec of the encoder and of the input.
Regards Alan

Alan,

The encoder is NPN type with 100pulse/rev.

There are 3 phases in encoder Phase A, B & Z

__|--|__

They are not sine wave encoder.

I taught the high speed input act as the normal Digital Input module, just that they can accept faster OFF-ON-OFF contact. It does not calculate the pulses like the Pulse Input (for encoder) does, right?

If the plc can see the input change then it should be able to count it.
The AB micrologix has inbuilt functions to count the pulses.
Regards Alan Case

The high speed inputs on the FX are designed for an encoder input like this. There is a specific instruction for it (which I can't remember off the top of my head). I think you use X0 X1 and X2 or X3

you probably didn't get to read any manuals for FX PLCs yet, their inputs can be wired for either sink or source. first six inputs in FX series PLCs can be used as high speed counter inputs. in other words they can be connected to encoder. since the machine you are talking about has three encoders, it means that one of the A,B,Z channels is not connected. it may depend on application but usually it will be Z that is left out. as for input type, i think you are confused with operation of some units (dry contact vs. transistor output). also all encoders have pulse output while resolvers have sine/cosine. some people call them same but they are not...

JohnW said:

The high speed inputs on the FX are designed for an encoder input like this. There is a specific instruction for it (which I can't remember off the top of my head). I think you use X0 X1 and X2 or X3

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Hi,

Yeah, they are connecting the encoder to the X2, X3, X4. The first 7 Inputs are for high speed inputs.