Safety : two hand operation

aand74

Member
Join Date
Dec 2005
Location
Deinze
Posts
131
I have an application where I should do two hand monitoring for safety.
However, I have several standard inputs, and only one failsafe digital input.
For an operation the button on the failsafe input must be pushed together with one of the buttons on the standard digital inputs.
I should think I need to activate two digital inputs for real safety standard.
Has in my case : combination safety input and digital input, any safety relevance?
 
Wouldn't connecting both buttons in series into that digital input do what you need?

I'm not familiar to the standard on this, but seeing as every or nearly every emergency stop button on Earth is wired in series with a couple more, perhaps the same logic can be applied here?
 
It's against the regulations cardosocea.

The two buttons have to be pressed within a short time to each other (stops somebody wedging one of them on)
 
Wouldn't connecting both buttons in series into that digital input do what you need?

I'm not familiar to the standard on this, but seeing as every or nearly every emergency stop button on Earth is wired in series with a couple more, perhaps the same logic can be applied here?

This is absolute not the way!!! An operator can easily stick one button with tape ore something, and use the other button in "one-hand" mode.
A safety relay mentioned for this function checks for the timing between both rising flanks of both inputs.

Funny thing is that there are also pneumatic types...
 
This is not e-stop this is THC which requires the operator to have both hands placed on a separate button for the entire duration of the dangerous movement. The buttons must be spaced a certain distance apart, the height of this station must be a certain height from the floor to prevent button pressing from the hip etc, the buttons must be shielded. The station must be a certain distance from the danger zone. The THC relay has logic that both buttons must be pressed within 0.5s of each other - releasing either button during the operation requires that both buttons must be released and then set again within 0.5s - this prevents an object being placed on one.

http://www2.schneider-electric.com/...Y2SB Instruction manual (140836201A55_05).pdf
 

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