AB32TSM

1734 VSHC24/C with a single encoder. Help Required?

12 posts in this topic

I am using a Studio 5000 V29 to program a 1769-L18ER-BB1B PLC, part of the program involves feedback from an encoder which is connected to a 1734 VHSC24/C point I/O card.

I've download to the PLC configured the I/O and updated firmware and EDS files, the PLC is running without any errors and the VHSC card has two green light lit .

But when I look in the Controller Tags for the project none of the registers for the VHSC card are change when the encoder is rotating.

I have never use this point I/O card before so have no experience configuring and coding , Do I have to use the GET command to retrieve #101?

Edited by AB32TSM

Share this post


Link to post
Share on other sites

Are those two green lights just the Module Status and Network Status up at the top ?   Those confirm that your IO connection and configuration are all OK.

But you should see "flickering" on the Input A and Input B LED when you spin the encoder.   If not, then there's something wrong with your wiring.

Can you describe the encoder make and model and how it's connected to the VHSC24 ?    

In general the VHSC24 gives you an update on its counts every RPI.    The really fast reactions of the module are on its onboard outputs, when they're set to turn on and off within a count window or at a count threshold.

How are you using the VHSC24 ?   It is for position detection, or velocity measurement, or something else ?

 

Share this post


Link to post
Share on other sites

Hi Ken,

Yes the two lights are the module status and network status , I'm trying to get a shaft speed form the encoder I've wire up  a single phase A+ to input A and power UB and GND to the +Vaux and -Vaux. Attached is the datasheet for the encoder.  Should I be using a simpler point I/O card?

0900766b812f7c25.pdf

Share this post


Link to post
Share on other sites

That encoder says it's software-selectable for TTL or HTL output.  

The 1734-VHSC24 is built for 24V encoder signals, so you want the High Threshold Logic (HTL) setting.   You'll want to book up both A and A- so that the module can detect the differential voltage between those two terminals.

Share this post


Link to post
Share on other sites

In addition to the Link and Module lights, there are also A, B, and Z lights that show you whether the encoder inputs are registering.

If you don't have a differential encoder, you'll need to add resistors into the circuit. The manual has information on this. I had to do this on a recent job... with 23 encoders...

Edit: OK, now that I looked at the data sheet, you do have a differential encoder, so you can ignore that last bit.

Edited by JRoss
Foobar

Share this post


Link to post
Share on other sites

I'm still not having any success with this counter module, I now have both the Link and Module lights on. The encoder is configured HTL/push pull 1024 ppr. both the A+ and A- are wired to the module, the A light comes on intermittently when the motor starts to rotate and stays on no visible sign of pulsing and sometimes stays on when the motor has stopped.

I think I have the module configuration wrong, I am trying to achieve a shaft speed from the encoder.  Advice on the correct configuration would be most welcome?

Share this post


Link to post
Share on other sites

I have now got the card working with it giving me a shaft frequency in 2:I.PresentData and an encoder count in 2:I.StoredData.

Both the A+ and A- channels are wired.

Find attached a copy of the module configuration to assist

Module Properties for 1734 VHSC24_2.docx

2 people like this

Share this post


Link to post
Share on other sites

Hi guys, good afternoon, 

I had the same problem as the friend above, but the use of Encoder is not to measure speed but terms as position reference.  But when using the PresentCounter variable, it does not seem to increase by 1 in 1, but rather seems to jump.  That is, I can not compare with my reference positions (in unit of pulses).

The module we are using is VHSC24 and configured as counter and nofilter (for maximum speed).  The encoder we are using is programmable DFS60B (maximum limit of 10,000 PPR).  

What could be happening?

Share this post


Link to post
Share on other sites

Hello guys,

I am running an application for packaging measurement using a sick DFS60B incremental encoder (programmable from 1 to 10000 PPR). In more detail, it passes packaging on a conveyor belt and we have created an inspection station and an expulsion station (defective packaging), so we use the encoder to check at specific points of the packaging for defects (we use special sensors to check defects). ) (there are four in total). However, the problem we are having is the following: When reading the encoder in the PLC, the same means that performs "jumps" and does not enter the windows (GRT and LES) created on the ladder, ie, as if it were not continuous. .

I understand that because the VHSC24 card works at 1 MHz in counter mode, this type of problem should not occur according to our application is not even 100 KHz. For example, our case: Using 1000 PPR and the motor speed (coupling output) is 3600 RPM (in practice it is around 1750 RPM) the frequency is calculated as follows: F = (PPR X RPM) / 60. : F = (1000x3600) / 60 = 60 KHz, ie 60 KHz is much less than 1 MHz, I think this kind of problem does not occur.

Application Info:

. Studio 5000 V31
. PLC Model: Rockwell 1769 - L19ER-BB1B CompactLogix 5370
. Encoder Card: 1734-VHSC24 / C
. Incremental Encoder: Sick, DFS60 up to 10,000 PPR and HTL Electrical Interface. Using a 200 mm circumference / perimeter wheel.
. Motor Nameplate Data: 1670 RPM, 0.37 kW / 0.5 HP, 60 Hz
. Inverter: Weg CFW500, Output Frequency 62 Hz.

Card Settings we use
RPI: 2 ms
Type: Counter, but we already use it as Encoder X1
Store Count Mode: Disabled
Filter: No Filter, but we use 50 KHz and 5 Khz filters in our tests.
Counter Attenuator: 1

Wiring Diagram VHSC24
We turn on encoder A at input 0 and encoder Aret at input 1

In logic
(Structured Text) Using the PMUL instruction to convert encoder (Pulse) data to mm scale.
(Ladder) The window comparisons part (GRT and Les) and other part of the process. We emphasize that we performed the tests also only with the reading and comparison part of the data, excluding the other parts, precisely to verify the issue of Scan, but the problem persisted.

If anyone here in the forum has some information that can help us, I would appreciate it.

Share this post


Link to post
Share on other sites

Is the logic for the encoder in the main continuous scan task of the PLC? If so move it to a periodic task with a small execution time. If the logic is small enough, make this 1ms. What are the windows you're trying to capture?

Share this post


Link to post
Share on other sites

Yes, it is in the main task (continuous).  The scan is around 2ms.  The card rpi is set to 2 ms.  That is, for a Freq = (1000x3600) / 60 = 60 KHz, and I lose about 120 pulses, 60KHz * 2 ms, which would be equivalent to 24 mm, since I have 1000 pulses for 200 mm of the wheel.  Ideally, a resolution of 1 mm, but if not possible, could be 5 to 8 mm.  I tried to create an event task by calling event instruction, but I can tell if it's the correct one.  But what intrigues me the most is the fact that the card is 1 MHz and is compatible with the Clp CompactLogix L19ER and this kind of problem occurs for such a low frequency (60 KHz for example)

 

 

 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now