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3.3V in series, cre...
 
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3.3V in series, create open circuit

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 Anonymous
Joined: 53 years ago
Posts: 0
Topic starter  

Hello all, this is my first post. I am excited to join the community; I have had my Arduino for a few years but am just now getting to put it to use. So far it has been fun and very educational.

What I want to do achieve:
I have a 3.3V circuit that runs along several switches in series. These switches are attached to a relay that relies on the 3.3V to keep the circuit closed. If one of my switches fails, the relay collapses, and a warning LED lights.
I want to wire my Arduino in series with these switches and if my Arduino program runs into a certain circumstance (using an if statement), I want to open the circuit at the Arduino and control the LED. Is this possible? If so, a nudge in the right direction, would appreciate.

If anyone has question or I need to clarify, please let me know. Thank you in advance!


   
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 Hans
(@hans)
Famed Member Admin
Joined: 9 years ago
Posts: 2311
 

So if I get this right:

You have a bunch of switches in series; all need to be close so the relay stays on.
Now you'd like to have the arduino basically detect which switch opened. Right?

Since I do not know the exact purpose of your circuit, ...
Maybe you could replace the switches with "double" switches (also called "dual" or "(DPST) Double Pole Single Throw Switch")?

These "double" switches are quite common and in fact have two independent switches build in (verify for the switch you may be using!).
One half of the switch can then for your current circuit, and other half for you to connect to an Arduino pin.

Something like this (just an example I found here, for two independent circuits, but one common switch):

So one side of the switch for your existing circuit (the light bulb in the example), and the other side each to its own Arduino pin (the light motor in the example).
Note: If you have more switches than pins, then you may have to work with a switch matrix (a little more complicated - but nothing scary).

 


   
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 Anonymous
Joined: 53 years ago
Posts: 0
Topic starter  

Thanks @hans.

Sorry it is a bit confusing. What I have is an already designed circuit that holds a relay open with 3.3V along multiple in series switches. If any of the switches open, the relay collapses closed, allowing 12V through to light a tower light.

What I am doing with the Nano, is adding another fault condition. I want the Nano in series with the already existing circuit. nothing should happen, unless my programmed condition occurs. At which point, the Nano should open the circuit, which will light my tower light. I was hoping to run the Nano in series using the GPIO pins only, but I am not finding any info related to this.

With that said, I think I am going to add a NC relay module to the Nano and have it open the relay if my condition occurs, lighting my light.


   
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 Hans
(@hans)
Famed Member Admin
Joined: 9 years ago
Posts: 2311
 

Ah OK, sorry for the mix up ... 😊 

So your nano is like "one of the switches" in your current circuit.
The yes, a relay could be the way to go. Definitely the easiest way.

Depending on the setup, if you choose to use a relay, then pick a relay that can match the default switch position. meaning; if a switch typically is "off", then make sure the relay is in that position when the relay isn't powered (or vice versa). Keep in mind that a relay is designed to switch occasionally. So you'd ideally want the relay to be in "rest" position, not powered, most of the time. I hope that made sense. 

As non-mechanical alternative, you can use a so called solid state relay.

Very much depending on the rest of your circuit, there are even more potential options like using a transistor or opto-coupler.


   
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