Door switches with lamps indicator

[mulderm]

Hi everybody,

I have a production machine that have around 12 security
doors with switches to give an emergency stop when a door
is open.
The 12 switches are in serie.
The problem is when a door is half open or the switch is not good working I must looking around the machine wich door is not operated.
This can be during a lot of time.
Now I want use for each door a lamp indicator so I can see
wich door is open or the switch is not very well.
Can anyone tells me how to make this?
I can use 12 relays but maybe is there a simply way.

Greetings,

mulderm

 

[melone]

Can you put a lamp after each switch, and just look for the first unlit light?

 

[IRstuff]

You can, but it'll be a little tricky, and will depend on the amount of current that the safety circuit supplies.

The standard trick used in the alarm industry is to parallel each switch with a relatively high impedance load such as a resistor. If such an impedance is replaced with a light or a relay load, you could make it work if the safety circuit supplies enough current for the light or the relay. A light load such as an 10-20mA LED might be possible.

Otherwise, the circuitry will need to be redesigned to supply more current.

TTFN

 

[harryr]

How far apart are the door switches?
Are the series switches closed and they open when a door opens or are they open and then close when a door opens?

 

[pablo02]

We have used small neon lights in parallel with such switches to indicate a switch open -- however, if more than one switch is open, you may have trouble locating it due to the impedance of the lights (won't light or extremely dim). The neon lights should provide sufficient impedance not to allow the safety circuit to operate even though current is flowing through the light (and circuit). [This is how illuminated light switches for homes used to work] The local Radio Shack or other electronics store should have some of these neon lights already to wire up.

Using lights in series after the switches will probably provide too much voltage drop and the circuit won't work even with the switches closed.

If you use any other type of light in parallel, you may need to include a dropping resistor to assure that the safety circuit will function as required... (you want to take a larger voltage drop across the light so the safety circuit will still function as intended) -- what ever you do, make sure that the system is thoroughly tested before putting it back into service.

 

[mulderm]

Hi Harryr,

About your question:
The series switches are closed and they open when a door opens.
The cable lenght is 4 meter to another door.

 

[melone]

Why won't my suggestion work?

 

[mulderm]

Hi Melone,

Because I want for example when door 6 is open the indicator above door 6 is lighting.

 

[melone]

What is more important, figuring out which door is open, or turning on a light that indicates which door(s) are open?

 

[mulderm]

I want to turning on a light upside the door so I can see
which door are open.
There are a n.o. and n.c. contacts in the switch.
The n.o. are used for the emergency stop circuit (in series).

 

[ScottyUK]

You have a n.c. contact which is open when the door is in the closed position, I think. If so, try the following:

Either have a lamp which is illuminated when the door is closed - i.e. a 'healthy' lamp.

Or feed an LED through a resistor, and use the switch to short across the LED, dropping the supply across the resistor only.

Or use a low voltage relay in place of the LED and connect the relay contact to whatever you want. If you want to really show off, use a solid-state relay in place of the LED.


Scotty.

 

[harryr]

Melone/ Mulderm

Melone:
It would be nice if we could attach a schematic to this post.
Is there a way to do that?
I think we are all looking at different wiring diagrams.
If I understand the wiring diagram and your solution, if the first light goes out, they will all go out since the
the contacts are in series.
Is that correct?

Mulderm:
How about changing the wiring so that all the lights are on
when all the doors are closed (say green lights).
Then when a door opens the light goes out and the safety
circuit is activated.
To do this--
1. Connect all the wiper arms in parallel
2. Connect the voltage to the first wiper arm
3. Connect all the normally open contacts in parallel with
the safety circuit
4. Connect each normally closed contact to a light
Will that work? Draw it out on paper (make a schematic)

 

[melone]

The low side of each lamp is grounded, but the high side could be switched in when the door is closed.