1756-PLS / Resolver / Digital input

Has anybody used 1756-PLS module.

can you please comment about it.

I just want to know whether i can use the 16 Digital inputs available in that card for

reading fast response inputs comming from my photo and proxy sensor.

is that digital inputs fast response type.

Can i use that 16 digital input present in that card for other purpose than for PLS function. is that possible.

Also can i use any Resolver or should i have to use it only with Allen Bradley 846SJ industrial resolver as said in manual.

why have they kept it to be used only with AB resolver. which doesnot solve the purpuse for us as we just wanted only
to replace the external panel mount PLS module to PLC based PLS. but now we cannot use our existing Resolver and now we need to
change to new AB resolver, coupling, mounting etc.all added work.

Also if i cannot use my 16 digital inputs for reading fast inputs, then i just wan to know is there any equivalent card
for 1771-IT.

thanks

grison

why have they kept it to be used only with AB resolver. which doesnot solve the purpuse for us as we just wanted only
to replace the external panel mount PLS module to PLC based PLS.

Click to expand...

I have found that resolvers & their PLS's are usually paired - even when updating from one PLS to a newer one from the same manufacturer, I have had to replace the resolver too.

As far a other uses for the card (other than e-Bay) if not using it as a PLS:
1. Doorstop
2. Paperweight
3. Workbench leg shim
4. Spare IC chips for electronic projects
etc.

These cards internally read the resolver & report the position, direction & speed to the PLC, they dont pass the actual inputs to the PLC to be able to use for a logic purpose.

Resolvers are a high precision, close tolerance and yet robust device. They are usually used in critical, demanding applications where absolute position and/or safety are the main considerations.

I would guess that >90% of positioning applications are done with much lower cost encoders, so resolvers occupy a small high-end niche in the market.

Yes, I've used it

Yes, you can reference the inputs directly in your program.
e.g. Local:x:I.InputDataRaw.y
where x is the slot number of the centre module and y is the bit number.
InputDataRaw is the real state of the inputs whereas InputData contains any 'over-rides' that may be configured.

According to the spec sheet:
Off to On delay is typically less than 15 microsec @ 30 deg. C and a maximum less than 150 microsec. @ 60 deg. C
On to Off delay is typically less than 30 microsec. @ 30 deg. C and maximum less than 200 microsec. @ 60 deg. C.

More of a consideration would be the RPI for the module which is a minimum of 2 millisec. and your program's scan rate. If you're hoping to tag input events to resolver position, you may have difficulties.

Definitely use the recommended AB resolver. It is designed to work with the specific reference voltage and frequency that the PLS module supplies.

Latches

Gerry, doesn't the PLS module latch the current count when the input goes high or low? The 2 ms RPI will not be a problem as long as the inputs latch the current count. Otherwise I don't see the point of the module.

The M02AE module has a latch that can be armed to save away the current count when triggered by a home input. This is all done in a FPGA, not in software so the results are very repeatable. The RPI makes no difference as long as two events do occur within one RPI.

Thanks

Thanks all for your post.

I have one question for Gerry.

Is there any fast response digital input card in 1756 platform or an equivalent to 1771-IT. I donot find any in catalog.

Gerry so you mean to say that i can read the digital inputs present in the left and right module.

So in this case i will wire my fast response photo sensor and proxy to left and right modules.

Actually i just want to replace Mini PLS from Autotech company.

in our existing setup the channel 1 to 4 outputs from autotech mini PLS is wired to our 1771-IT module.

And also some position sensors like photo and proxy are wired to 1771-IT module.

now as such i want to replace 1771 platform with 1756 platform and was selecting equivalent I/O modules in 1756. when i saw 1756-PLS i thougt i can also replace Mini PLS with 1756-PLS.

Now if i want to replace 1771 to 1756 without 1756-PLS ( by keeping autotech mini PLS) then i would need a fast response card in 1756 platform. which i donot find. Is there any way around.

thanks

Peter,
The purpose of the module is to switch its outputs at programmed positions. Once programmed (using message instructions), it functions independently of the CLX processor. When operating solenoids (for example), the operating delays for on and off can be incorporated in the programming to compensate for variable speeds from the resolver. The inputs are primarily intended for gating the outputs in one of three modes, described as AND, PULSE, and WINDOWED.
AND - output is on while input and position band coincide.
PULSE - if input is on at beginning of position band, output is on for duration of position band.
WINDOWED - if input turns on during a separately defined position window, output will turn on for position band.

Output operation can also be time-limited and/or speed-limited.

Grison,
If the photo eye and proximity sw. are for conditioning actions controlled by the PLS, perhaps the 1756-PLS can do the whole job?

Otherwise, as Ken Roach has pointed out, there is the 1756-IB32/B with a 0.4 millisec. delay which should compare favourably with the 1771-IT module's 0.6(+/-0.2)millisec.