Allen bradley slc 500 High speed counter encoder

[dotrixe]

Hello!

We have a drum rotation machine controlled by a AB SLC 500.
The drum rotation inputs comes from a encoder into a 1746-HSCE.
We are using 2 channels AA and BB. The encoder is supplied with 24vdc.

Every 5 - 6 month the machine have trouble to rotate. We have to replace the 1746-HSCE card. The card itself have some cracks and burnt resistors.

Have anyone else this problem or any idea what causes this?

 

[Lynx777]

Hi dotrixe, Welcome to the forum.

From my experience grounding issues can cause problems like this.
I would check that the machine and the encoder are all properly grounded.
I would also check that the shielding for the encoder is properly connected.

 

[dotrixe]

Thanks Lynx777 for your quick reply to my post.

I'm going to check the grounding and shielding.

Hi dotrixe, Welcome to the forum.

From my experience grounding issues can cause problems like this.
I would check that the machine and the encoder are all properly grounded.
I would also check that the shielding for the encoder is properly connected.

 

[GaryS]

it looks to me like you have the input jumpers set for 5VDC in and the encoder is sending 24VDC out to the HSC card
check chapter 3 of the manual
if you had a bad ground i would expect to see the counts / position to be not repeatable
so if it counts OK but just burns up the same resisters it's a good be it the input voltage is set wrong

let us know how you make out

 

[dotrixe]

Hi GaryS,
Thanks for your help.

I'm using the same wiring as refer page 3-11 in the manual.

I'm using differential not single ended. The only terminals im using is A+ A- and B+ B-. I'm not using the LS(24VDC) Terminal.

Are you talking about SW1 dipswitch?
I can see my dipswitches on SW1(inputs) is set to off. Refer to the manual if i use differential inputs the switches should be on. 2.8-4.5V dc. So mine is wrong set.

it looks to me like you have the input jumpers set for 5VDC in and the encoder is sending 24VDC out to the HSC card
check chapter 3 of the manual
if you had a bad ground i would expect to see the counts / position to be not repeatable
so if it counts OK but just burns up the same resisters it's a good be it the input voltage is set wrong

let us know how you make out

 

[GaryS]

A few thoughts that may help
It looks to me like the input resisters to the opto isolators is burning up that only happens if the voltage to then is too high.
You must first understand what Differential output means. I know it look clear but there more to it then it appears. It phrase is shortened from the original “Deferential Line Drive” it is great system extremely good noise immunity but the line driver means that
When the channel is True the + out / counter input is connected to the Pos power supply of the encoder with only a few ohms of resistance and the – output / counter input is connected to the Neg power supply of the encoder with only a few ohms of resistance. When the channel is False this is reversed. So there is always full power supply potential on the counter inputs all the times in your case 24VDC
The inputs of the HSCE module are all opto isolated so if the resisters are set for 5 VDC on th e inputs and u supply it with 24VDC it will burn up the resisters and that what I am seeing on you pictures
If you look at Chapter of the manual they show 6 input voltage jumpers the need to set for the correct voltage supplied by the encoder.
I noticed on you picture that you are using Rev A and I could not find the 6 jumpers anywhere in the picture. The manual clearly says you need to set the jumpers for the expected input voltage. That would lead me to believe the Rev A is not capable of supporting a 24VDC encoder. I know they are up to at least Rev C on the HSCE
You need to call Rockwell support to get clarification on that.
I have installed many of those over the years and never have I seen this problem and you say you have the same problem repeating itself. It’s clear that the problem is the input voltage is wong.
If you keep using the same rev, I think you will keep burring out the input resisters.
If you don’t have a manual for the 1746-HSCE module you can down load it or pm me with an email address and I can send you a copy of the one I have.