Usage of Push buttons

sreeramu · Feb 15, 2011

Hi all

I would like to know weather i can use push buttons instead of communication throu HMI for activating Drives throu PLC. Which is best by HMI or by Mechanical Push buttons can any one please help me.

Rube · Feb 15, 2011

You can but it depends on your application as to whether it's the best way to go...

rdrast · Feb 15, 2011

/shrug.
You can use virtually any method you can dream up. Soft-buttons (HMI buttons), Hard-wired buttons (physical devices), Toggle switches, Photo-eyes, and another thousand or so methods of control.

What is best is almost 100% situational, although Emergency Stops should be hard-wired, physical operators in any case.

bguinn · Feb 15, 2011

Typically, I always hardwire my operator start, stop, and main speed pots. Anything else that is repetitive use, I hardwire, nonessential things such as auto/off/manual selectors, enable/disable, or speed offsets, I will put on an HMI if the project is big enough to warrant an HMI. The biggest thing I use the HMI's for is monitoring, fault annunciation, and configuration. Again it depends if the project is big enough to even need an HMI.

Badger · Feb 15, 2011

I voted for both.

harryting · Feb 15, 2011

Depend on the application, doesn't it?

E-Stop => mechnical

Self-Destruct => HMI with password

Binaural · Feb 15, 2011

rdrast said:
/shrug.
You can use virtually any method you can dream up. Soft-buttons (HMI buttons), Hard-wired buttons (physical devices), Toggle switches, Photo-eyes, and another thousand or so methods of control.

What is best is almost 100% situational, although Emergency Stops should be hard-wired, physical operators in any case.

...unless it's a safety PLC, in which case it can be an input to a controller.

The Plc Kid · Feb 15, 2011

I use all HMI where possible. Only Estop is a button and most of those are going to Guardlogix so they are aonly hardwired to the point I/O in the HMI enclosure.

drphil69 · Feb 15, 2011

As many have said, it is situational dependent. I usually try to find out what the end user (operator) would want.

shawn_75 · Feb 16, 2011

harryting said:
Depend on the application, doesn't it?

E-Stop => mechnical

Self-Destruct => HMI with password

Your self destruct comment made me laugh and think of something I've always wanted to make. I want to build an operator just like the one Kahn used in Star Trek the Wrath of Kahn to start the genesis device. If you've never seen the movie, it is the Rube Goldberg of OF/OFF switches with concentric cylinders that aparrently require great force to rotate. When rotated, each cylinder falls down until the last cylinder drops. If I ever do build it I'll hook it up to something mundane around the office like the paper shredder or coffee pot. In retrospect, the coffee pot is certainly not mundane.

rdrast · Feb 17, 2011

Binaural said:
...unless it's a safety PLC, in which case it can be an input to a controller.

Yes, but the question was about physical vs. virtual pushbuttons. EStops, even if wired to a safety controller should always be physical buttons/devices.

Jeebs · Feb 17, 2011

It depends.
Mostly on your operators.

Done both.
Seen both pushbuttons and HMI get utterly destroyed by an angry operator.
The pushbuttons he fixed by physically connecting the wires (didn't surprise me).
The HMI......well he had a hard time explaining that one.

uptown47 · Feb 17, 2011

rdrast said:
/shrug.
You can use virtually any method you can dream up. Soft-buttons (HMI buttons), Hard-wired buttons (physical devices), Toggle switches, Photo-eyes, and another thousand or so methods of control.

What is best is almost 100% situational, although Emergency Stops should be hard-wired, physical operators in any case.

Wot he said.

Paul B · Feb 18, 2011

For things that get used all the time I prefer pushbuttons.
Alarm clear, horn silence are no-brainers. When the horn is blowing, give them a button to press. On a system with higher margins we include system start & stop buttons. So, total of four buttons. Makes for a nice looking panel. For everything else, HMI.

For low-margin panels we put everything on the HMI but I still think one button for alarm clear/silence horn is mandatory. I program the plc so the first time they press the button the horn is silenced, the second time it clears the alarm. $19 for an illuminated pushbutton is well worth the cost if you ask me. Which you did in the poll, LOL

I also voted for both!

Tom@Pton · Feb 19, 2011

FWIW we use both. Last setup had equipment that should only be started with the operator in direct attendance. Once up and running any further adjustments and Stop could be made at an HMI. Starting was not an option at the HMI.

Usage of Push buttons

mechanical action or HMI

Mechanical

HMI

sreeramu

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Rube

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rdrast

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bguinn

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Badger

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harryting

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The Plc Kid

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shawn_75

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rdrast

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