Hi
I'm completely new to arduino , want to build a monitored loop with end of line resistor as a alarm loop , is this possible with arduino ,mwhere do I start
Would really appreciate help
Thanks
Craig
want to build a monitored loop with end of line resistor as a alarm loop
Could you elaborate on what this means?
Hi
So I want to have a bit of alarm cable and put a resistor across the end of it , then I want to monitor this cable so I know if anyone has cut it or shorted it ,
Let me know if you need any more info
Cheers
Craig
How about just making it part of a voltage divider (Voltage divider - Wikipedia) and connecting the middle to an analog input of the Arduino?
Hi
I think that is sort of what I need , what I need it to do is if the loop of wire is cut or shorted out I need it to set of a alarm , I am really looking for a step by step guide as I havnt got a clue , first project
Cheers
Craig
I am really looking for a step by step guide as I havnt got a clue , first project
You get help here but don't expect step by step solutions for your custom projects. You got the hints and know now where to look for additional information but you have to do your project yourself, we won't do it for you.
In your IDE there are examples that will help you learn the basics.
Going through them will give you a good foundation in programming the Arduino.
Yes, we've had previous threads on this subject.
It's perfectly straightforward to do, but there are a few important engineering tricks to it.
The main two concerns are protection of the Arduino, and interference, and these are addressed together. To start with, your "loop" is to ground, and powered from your main supply (not the Arduino) which is presumably 12V, via a resistor of three times the loop resistor value, say 1k5 with 470 ohms on the end of the loop. This results in a voltage of around 3V, which you feed to an analog pin on the Arduino through a 4k7 resistor which limits any adverse input into the Arduino when either the loop is broken, or some sort of impulse (lightning!) is coupled into the loop. For additional protection you might put a 4.7V Zener across the input and a 0.47µF capacitor (plastic, not electrolytic) to suppress radio interference and switching transients from mains wiring.
And then of course, you read the analog voltage at about 100 ms intervals in your main processing loop, and use a "debounce" routine to detect significant alterations in the value measured that persist for more than five successive readings - about ½ a second.
There you go!
Paul__B:
The main two concerns are protection of the Arduino, and interference, and these are addressed together. To start with, your "loop" is to ground, and powered from your main supply (not the Arduino) which is presumably 12V, via a resistor of three times the loop resistor value, say 1k5 with 470 ohms on the end of the loop. This results in a voltage of around 3V, which you feed to an analog pin on the Arduino through a 4k7 resistor which limits any adverse input into the Arduino when either the loop is broken, or some sort of impulse (lightning!) is coupled into the loop. For additional protection you might put a 4.7V Zener across the input and a 0.47µF capacitor (plastic, not electrolytic) to suppress radio interference and switching transients from mains wiring.And then of course, you read the analog voltage at about 100 ms intervals in your main processing loop, and use a "debounce" routine to detect significant alterations in the value measured that persist for more than five successive readings - about ½ a second.
Thanks! This is exactly the kind of info what I have been looking for too.
It is amazing how few info there are on the net considering that all the legacy alarm systems use such a simple resistor loops.
Would it be easy (how?) to make the voltage detection to control relays to latch and give binary info on each of the voltage levels. And then "read" those with arduino for additional safety? I mean there would be four relays for each scenario of 1) short circuit, 2) eol resistor only, 3) cut wire and 4) alarm. I think some alarms have even separate internal failure state that could add another relay. The voltage levels should perhaps be adjustable to the case with potentiometers.
It would be perfect if that kind of a circuit would be a ready made module.
tsamppa:
It would be perfect if that kind of a circuit would be a ready made module.
Well you might be waiting awhile.
Your suggestion is to use a number of comparators - LM339s in addition to the Arduino. Yes, quite do-able.