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"Timming issue"

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Trini - (2 posts) Feb-11-01, 05:11 PM (EST)

"Timming issue"

I have an omron plc(cpma1) and I have one left input for two opto switch sensors for the operator to insert his/her fingure in each sensor to activate a press. I need the switchs to activiate only if they are within the time I set,if time expire for either switch,the input to plc does not turn ON. I tried to use two timers with not much success. Does any body thier know how to acheive this task without programming the plc?(no unsed inputs avialable or an expansion module).

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Table of contents

RE: Timming issue, Steve Bailey, Feb-11-01, (1)
RE: Timming issue, Bob Earnheart, Feb-12-01, (2)
RE: Timming issue, iant, Feb-12-01, (3)
RE: Timming issue, Steve Bailey, Feb-12-01, (4)
RE: Timming issue, iant, Feb-13-01, (5)
RE: Timming issue, Chris@TECH3, Feb-13-01, (6)

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Steve Bailey - (749 posts) Feb-11-01, 05:23 PM (EST)

1. "RE: Timming issue"

Two-hand control is not a function that should be controlled by the PLC. You should use hardwired, standalone devices designed for the application.
Even if your local codes allow you to let the PLC control the two-hand trigger, you would need two inputs to do it. This is not the place where you would try to come up with a 'creative' solution to overcome a deficiency on your machine. How would you feel if the program you wrote to get around the lack of the proper equipment caused the operator of the press to lose his hands?
There was a thread in this forum recently regarding safety issues for presses. I suggest you look it up, download the OSHA standard, and study it. If your boss is telling you to do this, find a new boss.

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Bob Earnheart - (37 posts) Feb-12-01, 01:04 AM (EST)

2. "RE: Timming issue"

I do agree, that you have some serious safety issue here but I will give you a suggestion. Take the two switches and have each control a dry contact relay. Put two NO contact (one from each relay) in series with a timer that will reset if either relay outputs are broken. This way your operator will always have to have both hands on the run switch before the machines main contactor latches in. Even if the PLC fails, your operator will still have one hand on one switch and one hand on the other. You are, don't forget, pointing a smoking gun at yourself and the operator by using a PLC in this way. Better thing about it.

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iant - (150 posts) Feb-12-01, 07:18 AM (EST)

3. "RE: Timming issue"

just a side note . All safety aspects should be properly investiated before you attempt any PLC button control.
You will be the only person responsible should an accident occure
again for an eg. on safety devices try http://www.pilzusa.com/
and your OHSA body

Ian Trost

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Steve Bailey - (749 posts) Feb-12-01, 07:34 AM (EST)

4. "RE: Timming issue"

The thread I was referring to is titled 'Press Brake Monitor' and was begun by Wayne on 1/14/01. The applicable OSHA standard is section 1910.217. Here's the link:
http://www.osha-slc.gov/OshStd_data/1910_0217.html

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iant - (150 posts) Feb-13-01, 07:20 AM (EST)

5. "RE: Timming issue"

I could not remember Steve.
But thats right
Ian Trost

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Chris@TECH3 - (2 posts) Feb-13-01, 12:56 PM (EST)

6. "RE: Timming issue"

You need to purchase an ANTI-TIEDOWN safety relay which will have two palm button unputs & one or more outputs.The Timing & safety are already built in so all you have to do is hook it up. It will cost between $400-$500 but are OSHA approved & will save you the time

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Trini - (2 posts)	Feb-11-01, 05:11 PM (EST)
"Timming issue"
I have an omron plc(cpma1) and I have one left input for two opto switch sensors for the operator to insert his/her fingure in each sensor to activate a press. I need the switchs to activiate only if they are within the time I set,if time expire for either switch,the input to plc does not turn ON. I tried to use two timers with not much success. Does any body thier know how to acheive this task without programming the plc?(no unsed inputs avialable or an expansion module).
	Top

Steve Bailey - (749 posts)	Feb-11-01, 05:23 PM (EST)
1. "RE: Timming issue"
Two-hand control is not a function that should be controlled by the PLC. You should use hardwired, standalone devices designed for the application. Even if your local codes allow you to let the PLC control the two-hand trigger, you would need two inputs to do it. This is not the place where you would try to come up with a 'creative' solution to overcome a deficiency on your machine. How would you feel if the program you wrote to get around the lack of the proper equipment caused the operator of the press to lose his hands? There was a thread in this forum recently regarding safety issues for presses. I suggest you look it up, download the OSHA standard, and study it. If your boss is telling you to do this, find a new boss.
	Top

Bob Earnheart - (37 posts)	Feb-12-01, 01:04 AM (EST)
2. "RE: Timming issue"
I do agree, that you have some serious safety issue here but I will give you a suggestion. Take the two switches and have each control a dry contact relay. Put two NO contact (one from each relay) in series with a timer that will reset if either relay outputs are broken. This way your operator will always have to have both hands on the run switch before the machines main contactor latches in. Even if the PLC fails, your operator will still have one hand on one switch and one hand on the other. You are, don't forget, pointing a smoking gun at yourself and the operator by using a PLC in this way. Better thing about it.
	Top


	iant - (150 posts)	Feb-12-01, 07:18 AM (EST)
	3. "RE: Timming issue"
	just a side note . All safety aspects should be properly investiated before you attempt any PLC button control. You will be the only person responsible should an accident occure again for an eg. on safety devices try http://www.pilzusa.com/ and your OHSA body Ian Trost
		Top

Steve Bailey - (749 posts)	Feb-12-01, 07:34 AM (EST)
4. "RE: Timming issue"
The thread I was referring to is titled 'Press Brake Monitor' and was begun by Wayne on 1/14/01. The applicable OSHA standard is section 1910.217. Here's the link: http://www.osha-slc.gov/OshStd_data/1910_0217.html
	Top


	iant - (150 posts)	Feb-13-01, 07:20 AM (EST)
	5. "RE: Timming issue"
	I could not remember Steve. But thats right Ian Trost
		Top

Chris@TECH3 - (2 posts)	Feb-13-01, 12:56 PM (EST)
6. "RE: Timming issue"
You need to purchase an ANTI-TIEDOWN safety relay which will have two palm button unputs & one or more outputs.The Timing & safety are already built in so all you have to do is hook it up. It will cost between $400-$500 but are OSHA approved & will save you the time
	Top

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