#### patelankur2603

Joined Jun 6, 2022
40
I am trying to work on a design were 3 24v inputs should be connected to one pcb and one of the input if triggers 24v then output should change to 24v and other 2 inputs shouldn't get affected.

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#### crutschow

Joined Mar 14, 2008
34,019
Not clear what you want.
Is there just one output that goes to 24V if any of the inputs is 24V?
What if more than one input is 24V?

#### Papabravo

Joined Feb 24, 2006
20,990
It sounds like what you want is a logical OR operation. The output is +24V as long as any of 3 inputs are at +24 V. I'm guessing there is some threshold in between +24 V and Ground, that defines the difference between High and Low.

#### AnalogKid

Joined Aug 1, 2013
10,943
other 2 inputs shouldn't get affected.
Do you mean that you do not want the 24 V from one module to be back-fed into the other two modules?

ak

#### BobTPH

Joined Jun 5, 2013
8,659
Does the 24V out provide power to something, if so, how much?

Same with the inputs, can they provide power and how much?

Are the 3 minus inputs common or are all the inputs isolated?

#### patelankur2603

Joined Jun 6, 2022
40
basically there are 3 inputs which are at 1v nearby to that voltage and whenever system goes into alarm depending on which input is bad , it triggers 24vdc supply to that input. now i am designing a circuit which will identify which input is bad and then give an output of 24vdc whenever somthing goes into alarm.

#### crutschow

Joined Mar 14, 2008
34,019
i am designing a circuit which will identify which input is bad and then give an output of 24vdc whenever somthing goes into alarm.
So, to repeat my question, how many outputs will your circuit have?
What form is the signal that identifies the bad output (binary or?).

#### BobTPH

Joined Jun 5, 2013
8,659
If you would bother to answer our questions, we might be able to answer yours.

#### patelankur2603

Joined Jun 6, 2022
40
So, to repeat my question, how many outputs will your circuit have?
What form is the signal that identifies the bad output (binary or?).
1st: only one output with 24vdc signal. 2nd: its analog singal. which gives 24vdc signal

#### patelankur2603

Joined Jun 6, 2022
40
Does the 24V out provide power to something, if so, how much?

Same with the inputs, can they provide power and how much?

Are the 3 minus inputs common or are all the inputs isolated?
think that a line with 0v is passing and whenever something happens it gives 24vdc power to that line.
i am creating a simple circuit which will take these 3 inputs which can go from 0v to 24vdc and output a single 24vdc line whenever one of the input turns 24v from ov.

#### patelankur2603

Joined Jun 6, 2022
40
think that a line with 0v is passing and whenever something happens it gives 24vdc power to that line.
i am creating a simple circuit which will take these 3 inputs which can go from 0v to 24vdc and output a single 24vdc line whenever one of the input turns 24v from ov.
3 inputs are not common and not isolated.

#### patelankur2603

Joined Jun 6, 2022
40
I will right clearly, what is happening. i am having 3 different input wires with analog signal having 1v or so normally. each of the input wire behaves similarly i.e whenever i system goes into alarm , a 24vdc is passed to specific input wire. now i need to design a circuit which takes these 3 inputs and outputs 24vdc whenever there is an 24vdc input signal. normally it will do nothing means 1v.

#### BobTPH

Joined Jun 5, 2013
8,659
3 inputs are not common and not isolated.
Sorry, but that is a binary choice, they either have one if their wires common or they do not. It cannot be both.

It sounds like they are isolated, which means no two of the incoming wires are connected together or to the output wires. If that is so, the problem is more complicated, you will need opto isolators and an independent source of 24V.

#### patelankur2603

Joined Jun 6, 2022
40
Sorry, but that is a binary choice, they either have one if their wires common or they do not. It cannot be both.

It sounds like they are isolated, which means no two of the incoming wires are connected together or to the output wires. If that is so, the problem is more complicated, you will need opto isolators and an independent source of 24V.
i dont think i need a 24v source. the inputs are coming from a chip output ULN2803 and actually now i realised that it will be 6 inputs as there are 2 wires from one module so total of 6 outputs from 3 modules. 6 inputs to new circuit and one output. 6 input llines which gives only 1 output.

#### patelankur2603

Joined Jun 6, 2022
40
Do you mean that you do not want the 24 V from one module to be back-fed into the other two modules?

ak
no.. i want if one the inputs among 6 gives 24vdc then output should be 24vdc. thats it

#### crutschow

Joined Mar 14, 2008
34,019
A diagram showing the exact inputs and outputs you need would be helpful, as I'm still confused about that.

#### patelankur2603

Joined Jun 6, 2022
40

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#### crutschow

Joined Mar 14, 2008
34,019
Could you not just use a diode in series with each line with the cathodes connected together to give an OR connection to the output?

#### patelankur2603

Joined Jun 6, 2022
40
Could you not just use a diode in series with each line with the cathodes connected together to give an OR connection to the output?
i need 24v output . . yes i can use diodes and a or gate but what about output.

#### AnalogKid

Joined Aug 1, 2013
10,943
How much current do you need out of the 24 V output?

What power source is available to power this output circuit?

ak