LeeH68

All. I have 14Nr stainless steel plates, in each of these plates there are 3 illuminated switches, one red, one amber and one green. The three leds are a visual indication of the status of the room, green is room clean, amber is room needs cleaning, red is room in operation

So, the ideal situation is that only one illuminated switch can be on at any one time. This would have been a piece of cake if I had ordered latching switches, but being a numpty I ordered momentary switches and had the plates made to suit. I would simply change the switches but I cant find a latching illuminated switch the same size and as you can see from the photo it is a shame to change the flush appearance now.

As no-one seems to make a 24V bi-stable latching relay that works from a single impulse I am struggling to find the solution. To make things worse, I know absolutely bugger all about electronics (but I am learning fast)

Hero999

It's certainly possible.

No offence intended but it depends on whether you have the materials avaliable and are skilled enough to do it.

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KMoffett

LeeH68,

Now I get the picture. Expensive (ouch), lighted, tamper-proof switches, just indicating a status.

3 S-R latches
6 diodes
3 resistors
...and the 78L12 regulator
...and 2 capacitors

I'll add a schematic later.

Ken

Added!

I'm still not sure about driving the LEDs directly off the gates...I'll have to bench test it...unless someone has some documentation.

Attached Images

1of3 Toggle.gif (35.8 KB, 20 views)

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Roff

I'm not sure how much LED drive you can get before you screw up the logic threshold, but it's only a few milliamps. I think you need LED drivers. You do need pulldown resistors on your diode OR gates, and 79L12 is a negative regulator. In your text, you had a 78L12, which is right.

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Ron

KMoffett

A little too hasty throwing the schematic together. As I said I was uncomfortable with the LED on the outputs, so added some drivers...and the pull down resistors.

So, here is the MARK II.

Ken

Attached Images

1of3 Toggle 2.gif (36.1 KB, 18 views)

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"To invent, you need a good imagination and a pile of junk."
Thomas A. Edison (1847 - 1931)

Roff

That looks good. I would be inclined to use a CD4011 instead of the diodes and the OR gate pulldowns, and switch GND instead of Vcc on the inputs. You would wind up trading 6 diodes and 3 resistors for a 14 pin package.

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Ron

KMoffett

Ron,

Choices...choices...choices. I guess this gets down to costs and foot prints...and what LeeH68's intentions are.
Sooo...?

Ken

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"To invent, you need a good imagination and a pile of junk."
Thomas A. Edison (1847 - 1931)

Roff

Yeah, half of one, six dozen of the other...
Like I said, just my preference.

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Ron

LeeH68

Thanks to everyone for the help so far. Just to clarify what I actually have.

I have 14 stainless steel plates with 3Nr illuminated switches in each, one green, one amber and one red (see attached photo). I dont want the switches to do anything other than turn the integral led on. My problem is that the switches are momentary switches not latching ones and thus what should have been simple is now a bit more complex.

As I see it, without changing the switches or adding anything else to illuminate the led there are two options:

1. The prefered option would be to press any of the 3 buttons, the led on that button would illuminate and the other two would be inhibited, if another button is pressed then that led illuminates and the one that was on goes off. so at any one time only one of the leds can be illuminated at any one time.

2. The other option is to have each switch as an individual, i.e you press the button the led lights up, you press it again it goes off. This switch is not linked in any way to the other two so potentially you could have all 3 leds either on or off.

3. The other thing i considered was installing a 3 position key switch, the thought being that you switch to whatever colour of led you want (the switch section on the illuminated units I have would therefore be redundant). The problem I have here is that the bezel and bit where the key goes in must be stainless steel as the cleaning chemicals used in the facility will corrode plastic, chrome plate etc etc. I cant find one anywhere, does anyone out there know of any manufacturers?.

As I am a novice in electronics I need a very simple diagram to follow, the diagrams in my first post are very easy to follow and something like that would be fantastic.

Many thanks

Lee

Attached Files

Room Card.pdf (102.8 KB, 14 views)

KMoffett

LeeH68,

I had to take one more whack at it. This should work for Solution #1

I'm using a small, programmable, micro-controller chip (PICAXE 14M) to sense the pushbutton switches, and select the correct LED to light. An added feature could be a power-failure indication . If the 24V power went out and came back on, the microcontroller could flash all LEDs indicating you need to reset the selection. Or a selection recovery....the microcontroller could store each new selection, and recover the last selection when the power returns.

This could be assembled on a small printed circuit board, and mounted, somehow, inside each panel. There are companies that will layout, make, and stuff the boards to your spec's...for a price

Ken

Attached Images

1of3 Toggle 3.gif (26.4 KB, 17 views)

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"To invent, you need a good imagination and a pile of junk."
Thomas A. Edison (1847 - 1931)

LeeH68

Ken

Your a star, I will try and get someone to make one up for me.

Many thanks for your time, and thankyou to everyone else who posted responses.

Lee

Roff

Ken, are you going to program it for him?

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Ron

KMoffett

Could. Takes a PC, a serial cable, and two resistors for hardware. Free software. So once written, they can roll their own. But wouldn't do it without all the hardware in hand and a lot more details...you never know what you don' know.

Ken

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"To invent, you need a good imagination and a pile of junk."
Thomas A. Edison (1847 - 1931)

KMoffett

Ron,

OK, I had to do it...for fun. The software works.

Ken

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"To invent, you need a good imagination and a pile of junk."
Thomas A. Edison (1847 - 1931)

Roff

Cool! I just started playing with PICs a few weeks ago, and I was able to successflly program one. I have an application in mind for one, but I have some sort of mental block about starting it. I always seem to find something more important or more interesting to do.

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Ron