Fault indicator

[kwame]

Hi folks!
Most motor control panels i have seen locally , have a lamp/indicator labelled 'fault'. It is illuminated when there is a fault of any sort in tthe circuit.Unfortunately , how the wiring is done is above my head.
Can anyone help me out?

Cheerio

 

[Norator]

Start by researching 'OR gate.'

 

[KeepItSimpleStupid]

Many control panel are 24 VDC which makes it easy. The technique is called a "wired-or" https://en.wikipedia.org/wiki/Wired_logic_connection.

It's done fairly regualrly in a vehicle to help distinguish a drivers door from a passenger door being opened.
The door switces are say connected to the dome light via a diode to ground. This effectively isolates the switches.
This does implement When either door is open, the dome light comes on.

I wanted a buzzer that operated when the driver's door was opened AND the headlights were on.

But let;s make it simpler for the time being, I want a light that says, "Passenger door open" and one thet says "Driver's door open".

I can again take +12, a light bulb and diode (2 sets) and connect them to each door swich and get an indicator for each door open and one for either door open (The dome light).

How did I do the heatlight on with the driver's door open?

 

[dr pepper]

Nearly every time I've come across that in industry the fault lamp is connected to the overload relay, if the motor pulls too much current the overload relay 'trips' disconnecting the supply to the coil of the motor contactor, the fault lamp is connected to the normally open contacts of the thermal relay so its on when a trip has occured.

Later control panels use a plc, a programmed controller, the fault indicator in this case is controlled by software.