Differences in PLCs

richleva

Member
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Join Date
Sep 2012
Location
ontario
Posts
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Hey guys,

I'm designing a Laser Barrier Curtain system for underground mining equipment. I was planning to use Allen Bradley Safety PLC and Relays. But my boss suggested that I use Eaton's EASY Intelligent Relays to cut cost. He figures I'll have the same programming capabilities. Has anyone used this ? any suggestions....
 
richleva said:
Hey guys,

I'm designing a Laser Barrier Curtain system for underground mining equipment. I was planning to use Allen Bradley Safety PLC and Relays. But my boss suggested that I use Eaton's EASY Intelligent Relays to cut cost. He figures I'll have the same programming capabilities. Has anyone used this ? any suggestions....
Click to expand...

It doesn't have the same programming capabilities but does it need to have? What is the PLC doing? A lot of people leap to the idea of using PLCs for safety but for a basic system e.g. a light guard shutting down a motor, they are over the top. A hardwired system allied with your laser control system could easily be fully compliant with safety regulations, then just use a basic PLC for monitoring and operator display. Cheap isn't necessarily nasty if you know what you're doing. Only you can make the judgement of course!
 
Its has a four point perimeter (4sensors). Operator should have the capability to use 1,2 or 3 sensors depending on what there doing and location in the mine. The operator is standing 100 feet away from the machine and is controlling the machine with a remote control. If anyone come near the machine my barrier system will turn the machine off for safety. I'm planning to install the controller or PLC on the machine with a 100" cable that will link my controller or PLC to a seconded device that will allow the operator see which sensor has tripped using LEDs to indicate. There will also be push button to activate the barrier system and a emergency stop button. The controller or PLC will also need to monitor jumper loops inside each connectors, therefor if a sensor is disconnected. The machine should not work, unless the sensor was properly bypassed using a specially jumper,

I need:

12 digital outputs
12 digital input
2 analogue inputs (0-24VDC)
Ethernet connectivity

Would you choose a PLC or a Cheap Controller to save on cost?
 
richleva said:
Its has a four point perimeter (4sensors). Operator should have the capability to use 1,2 or 3 sensors depending on what there doing and location in the mine. The operator is standing 100 feet away from the machine and is controlling the machine with a remote control. If anyone come near the machine my barrier system will turn the machine off for safety. I'm planning to install the controller or PLC on the machine with a 100" cable that will link my controller or PLC to a seconded device that will allow the operator see which sensor has tripped using LEDs to indicate. There will also be push button to activate the barrier system and a emergency stop button. The controller or PLC will also need to monitor jumper loops inside each connectors, therefor if a sensor is disconnected. The machine should not work, unless the sensor was properly bypassed using a specially jumper,

I need:

12 digital outputs
12 digital input
2 analogue inputs (0-24VDC)
Ethernet connectivity

Would you choose a PLC or a Cheap Controller to save on cost?
Click to expand...

As far as I can see on the Eaton website there isn't a version of the easySafety that meets these requirements.
 
To be honest if all you need to do is kill power to a machine then a hardwired system might suffice i.e. your laser controller which I assume has safety guided contacts (?) and a Pilz type relay for the E.Stop circuit.

Don't know much about the Eaton thing, but if it can handle all you need I/O and programming wise then why not? Otherwise maybe look at an entry level "proper" PLC.
 
Since this is a mining facility, I recommend the following.

1. look up your regulations in regards to safety controllers and requirements.
then get with engineering and safety and do a risk assessment.

in my opinion, since this is a safety device controller to control the machine if the light curtain is broken, you must use a safety controller.

you MUST cover all your bases: dot every I and cross every t.
you don't need to have an accident and it come back on your company or you.

regards,
james
 
James Mcquade said:
Since this is a mining facility, I recommend the following.

1. look up your regulations in regards to safety controllers and requirements.
then get with engineering and safety and do a risk assessment.

in my opinion, since this is a safety device controller to control the machine if the light curtain is broken, you must use a safety controller.

you MUST cover all your bases: dot every I and cross every t.
you don't need to have an accident and it come back on your company or you.

regards,
james
Click to expand...

I second this motion.
You will also need to know what 'level' of safety you need in manufacturing it is sometimes called SIL level.
Not all "Safety" devices are created equal.

...Also why laser instead of Radar?
 
RussB said:
I second this motion.
You will also need to know what 'level' of safety you need in manufacturing it is sometimes called SIL level.
Not all "Safety" devices are created equal.

...Also why laser instead of Radar?
Click to expand...

I did say laser, but I will be using PIR Motion detection
 
Last edited:
James Mcquade said:
Since this is a mining facility, I recommend the following.

1. look up your regulations in regards to safety controllers and requirements.
then get with engineering and safety and do a risk assessment.

in my opinion, since this is a safety device controller to control the machine if the light curtain is broken, you must use a safety controller.

you MUST cover all your bases: dot every I and cross every t.
you don't need to have an accident and it come back on your company or you.

regards,
james
Click to expand...

Must use one? There are safety relays from Pilz or laser controllers from Sick that are hardwired devices and conform to the highest levels of industrial safety. Simple systems which the above seems to be do not need safety PLCs. Hardwired systems can handle the safety element to the required standards and then the functionality/operator interface can be handled by any PLC with the capability.

A risk assessment will give you the safety level required, the controls engineer needs to decide whether a safety PLC is necessary or if alternative options should be considered. As I say, cheap is not necessarily nasty. Going for a safety PLC when a Pilz relay and Sick controller at SIL3 will do the job is more expensive but not in any way safer.
 
I used AS-I interface safety module. installed E-stops, sensors and light curtains.its way cost effective than safety PLCs and their software.
 
Rich,

From an I/O perspective the FMD1616-10 from Triangle Research meets your requirements. This unit also includes an Ethernet Port.

http://www.eternity-sales.com/tri-plc/fmdseries.htm

I would suggest reviewing the programming manual from the link of our web page provided above to see if it meets your desired programming requirements.

Disclosure - ESI is an authorized Triangle Research Distributor. We also have a line of Touch Screens and Ethernet Switches should you require them for your application.
 

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