Electronics Help wiring a illuminated automotive toggle switch?

Hello,

How would I wire a standard illuminated automotive toggle switch if I want the light in the switch to be on when the switch has removed power from the item it's controlling.

This switch will be controlling a 12v fan, but I want the light in the toggle switch to be on when the fan is off.

 

if you have a diagram of it connected normally, you will see that there is one Gnd connection, on my switches the terminal is marked "G"
and there is one called "B+" that is normally for the supply to the switch, but here you connect the load.
and the last terminal is marked "load" (on my switch) connect the supply here.
Now the light in the switch will be lit all the time, and the switch controlls the fan

 

It depends on two things:

1: Do you want constant light, or do you want the light to turn off when the unit is turned on?

2: What switch you have, and how it's constructed. If we get more info on what switch we are talking about, it will be much easier to help

 

1) I want the light to be on only when the fan is off.

2) This is the switch I have. It has 3 terminals labeled 12V, ACCY, and GND. I believe the GND is only the ground for the light and the other two terminals are the interruptor legs.

 

I know I can do this with a relay, but I'm trying to avoid that.

 

I see. What you need to do is to connect GND to the positive pole of your battery, and then connect both 12V and ACCY to the positive pole on the fan. The ground on the fan goes directly to the ground pole on the battery (Or to the chassis in the car).

Mind you, this isn't the best way to do it, ans some current will flow trough your fan. If the fan is big enough there shouldn't be any problem, but if it's a small fan (Like a computer fan) it may start turning slowly even when the switch is off.

What happens is that the bulb in the switch will draw current trough the fan to make it glow (The current the bulb allows trough shouldn't be enough to turn the fan). When the switch is turned on, it will short out the bulb, giving the fan full power.


If the bulb in the switch is a LED, you may have to connect the switch the other way around (12V and ACCY to the positive pole on the battery, and GND to the positive pole on the fan)

I suggest you test this out before you make a permanent solution.

 

Thanks for the help. I'll give that a try.

 

Close but no cigar.

Code:

            /
 (12V)--+-o/  o-+--(ACCY)-----+
        |       |             |
        |       |             |
        |      lamp          FAN
        |       |             |
        |       |             |
        |     (GND)           |
        |       |             |
        |       |             |
        +-----+12V           0V

It will work if the fan is a much higher wattage than the bulb (and if the "bulb" isn't a LED). My doorbell light uses the same principle, with only two wires to the push needed.

 

Yes, it's cigar:




edit: The ability to upload pictures on the new forums is simply awesome!

 

I think you'll find the switch internal is not quite as per your drawing...

Code:

            /
 (12V)--+-o/  o-+--(ACCY)
                |        
                |        
               Lamp
                |  
                |  
              (GND)

 

DO'H! Of course!

When I look at it, my switch would do nothing more than to just short out if used "correctly"...


So bajastx: Do as cpemma says. He actually knows what he's talking about. hehe

 

The switches I have uses a LED for the light, and leds do, (as most of us know) only work with the correct polarity.

So this is how you need to connect it if there is a LED.


As Smilodon mentioned, the fan will have a little current running thru it, but hopefully not enugh to make it run, or not stop...

oh, and sorry for the paint drawing..

FORK! now I saw that you had a link to the switch....
not the same as I was thinking about, but it still probably has a LED..