4 PB's in one 30mm hole

Alright gang, here is my problem.
Instead of getting a package site alarm system, I was tasked (as an EE at coal-fired power plant) with installing a group of air horns around the site. The idea was that in the event of an emergency, the operators in the control room would press a button, and the horn would sound.
The safety folk decided that this system needed to go in ***now** so that what we did, and right now, in our control room, there is one button, which fires all the horns.

Procedurally, we wanted to make our system like our neighboring plants, so I wrote a series of 4 different horn sequences (ex: 4 long blasts for "fire", 4 short blasts for evacuate, short/long for weather, and a 30second blast for 'all clear).

Pretty easy to remember- right ? There is only 4, we are getting hard hat stickers and posters made up, in addition to the a large training commitment.

Well, the operators pushed back on the safety group, and said "we dont want to press this button 4 times for a signal, we want to press one button for any given sequence - ie- they want to press one button for "fire", a different button for "evacuate" etc...

fair enough - if the word comes over the radio, they press the "fire" button, a ML1200 sounds the sequence and the operator goes back to surfing the internets (lol)

Problem is - this must fit on a floor to ceiling control panel, 1/8"(?) thick metal chock full of meters, pistol-grip swtiches, 30mm buttons and some pilot lights (yeah, we are old school like that)

In my case, I only have 1x 30mm hole to put these 4 buttons inside of. there is some unused panel space nearby (a few inches on each side) but If I cut a larger hole (like for a small HMI- I cringe at the thought)I'd be crowding nearby controls.



Are you able to follow me ? I need to stuff 4 pushbuttons in the space of 1 30mm hole on a panel.


Any ideas ? vendors ? Done this before ? screw it and just put in a small touchscreen ?

-John

Don't forget labels for these buttons. Bubba is not going to like learning color codes.

How is fat fingered Bubba going to push these tiny buttons?

Small touchsreen sounds right to me.

It's it illegal ( safety regulations) to put stickers on hard hats? ( I know everybody does it)

Could you use a selector switch with a short de-bounce time in the PLC (maybe 1 sec)? That would allow the correct selection to be in position before the plc reacted- 5 positions, off, then the 4 states.

tommy23t

a joy stick, maybe?

Not a joy stick, but maybe something like a d-pad?

I would use a 4 way toggle switch. AB part number 800T-T4T8AAXX
It is about 80% down the page on this site http://www.ab.com/en/epub/catalogs/12768/229240/229244/2531083/tab4.html

Something like this maybe?
http://www.allelectronics.com/make-a-store/item/PB-168/4-POSITION-PUSHBUTTON-SWITCH/1.html

Or a standard 4 position selector switch will work

hd_coop said:

I would use a 4 way toggle switch. AB part number 800T-T4T8AAXX
It is about 80% down the page on this site http://www.ab.com/en/epub/catalogs/12768/229240/229244/2531083/tab4.html

Click to expand...

Yeah, that's the joys stick I was envisioning...nice find

The Plc Kid said:

Something like this maybe?
http://www.allelectronics.com/make-a-store/item/PB-168/4-POSITION-PUSHBUTTON-SWITCH/1.html

Or a standard 4 position selector switch will work

Click to expand...

+1 from me. Simple = safe.

I would put a short time delay on it so you didn't get confusion while you were switching from one selection toanother.

Wow - fantastic ideas all the way around.

the joystick is leading right now becuase it has a neutral center.
drawbacks include- its much easier to accidentally bump a joystick than a seleector switch.

I was going to use a 4 position selector switch but I'd really need a 5-position (an "off" position). OR program logic to only actuate the alarm when the switch is moved - so if the test sound is sound #4, bubba would have to take the switch off of #4, then siwtch it back to #4. I'm not a fan of this if there are better options.
Its easy to guard a sel. sw. though.

That 4-push button is a neat idea, but without some kinda pilot light, you'd never know how many presses it has 'stored', so you'd press it once for sound #1, but since it was pressed once last time it'd now have 2 presses, and sound the wrong sound.

Any more ideas ? Eaton/C-H has a big square pushbutton (lighted- even better) but the contact development is cryptic, and the Eaton automation guy said "you can't do it". I'd take that as a challenge if I had mroe time.

I appreciate the responses guys !

-John

You could use an illuminated push button and logic as follows:

Normal condition, once every two seconds, the light will flash the current setting, similar to how a fault code is displayed on some devices. A 100ms pulse time would work well. To program a new setting, hold down the button for one second to enter program mode. This will cause the light to remain on. While in program mode, the operation of the light is reversed (pulses of no light showing the current setting), and pressing the button will increment the setting (1-2-3-4-1-2-3-4). To exit the program mode, hold the button down for one second again and you're done.

Here is a link to 5 position selector switches.

http://www.eecontrols.com/documents/171.pdf

Johnster said:

...drawbacks include- its much easier to accidentally bump a joystick than a seleector switch....

Click to expand...

OK. If I understand correctly, the operator will initiate an alarm using a pulse input to the PLC. The alarm will seal in until something (the operator or a timer?) turns it off.

Try this: using the joy stick, put in a 1 second de-bounce timer to prevent an alarm because of bumping (you could also instal raised shield that one has to reach inside). The operator holds the joy stick in place for 1 second - the alarm begins sounding - and he lets go. If you program it to act as a flip-flop, the operator would simply toggle the stick again to shut off the alarm.

Steve

markie said:

+1 from me. Simple = safe.

I would put a short time delay on it so you didn't get confusion while you were switching from one selection toanother.

Click to expand...

Yes that's the problem with a selector switch bumping over the other choices. You may be able to make it work with a time delay, but time delays suck in emergency situations.
It would be cool if they made a selector switch that was also a push button.
I can envision it, a regular push button with a bezel around the outside where you can make your selection.
Don't recall seeing one for sure.
Good Luck.

I would either go with the Joystick Switch, or you might be able to fit 4 16mm buttons in your space AB 800A‑L2CR24 or 800A‑M2FR
http://www.ab.com/en/epub/catalogs/12768/229240/229244/10891387/1309933/tab3.html

For a safety situation, I don't like the selector switch, multiple presses, or HMI option... too easy, to get the wrong message out, and the HMI is obviously a no, no, for anything safety.