need help on latching relay circuit

Thread Starter

555timer

Joined Feb 13, 2011
13
I looking for a latching cirucit that will light up the LED if the copper wire is open cirucit at the other end. Is it a simple cirucit to build? Any guide? thanks.
 

KMoffett

Joined Dec 19, 2007
2,877
We need a lot more info. Is the copper wire part of an existing circuit? What voltage/current/distance/AWG are involved? Give us the big picture.

Ken
 

Thread Starter

555timer

Joined Feb 13, 2011
13
We need a lot more info. Is the copper wire part of an existing circuit? What voltage/current/distance/AWG are involved? Give us the big picture.

Ken
The copper wire is part of the existing circuit. So when there is a open copper wire, the latch relay should light up the LED and remain so until it been reset. As for the voltage/current i not sure and the distance can be like 100 to 200 meter away. I know if there is an open cooper wire, the resistance is around 50M ohm and if is not open, is around 50ohm or so. Please advise on a simple design. Thanks.
 

Wendy

Joined Mar 24, 2008
22,141
Schematics are the language of electronics. If you don't understand a schematic then you can't speak the language, or understand the concepts.

Is this something you are hoping to design? It could be simple, but if the wires are in use then maybe not. We simply don't have enough information to be able to help.
 

Thread Starter

555timer

Joined Feb 13, 2011
13
ok, i found one circuit which is close to my application. Pleas see the link below:
http://www.youtube.com/watch?v=IjlX0AZjdIU&feature=related

However, I notice a small problem in this circuit and need help from your help. When SW1 is closed and the push button switch is pressed, the relay mechanism will "move" to the left. When SW1 is open, the relay mechanism will "move" to the right. But I was wondering how long can the relay mechanism remain at the left until before SW1 is open. If it is just a short duration, how can i modify the circuit such that it will last a long period of time, until SW1 is open.

Hope you all get what I mean. =)

Please advise. Thanks.
 

KMoffett

Joined Dec 19, 2007
2,877
It's not the latching circuit schematic we're looking for, it's the schematic of the circuit you're trying to monitor. That will help in determining what would be needed to trigger the latching circuit...the easy part.

Ken
 

Thread Starter

555timer

Joined Feb 13, 2011
13
ok... the circuit i am trying to montor open circuit and is like the SW1 switch, when there is an open circuit and the LED will off if base on this circuit.
 

Thread Starter

555timer

Joined Feb 13, 2011
13
Just to add in more information, I am monitoring an alarm unit for some equipment. So need the latching relay to see which alarm unit give the fault.
 

KMoffett

Joined Dec 19, 2007
2,877
The copper wire is part of the existing circuit. So when there is a open copper wire, the latch relay should light up the LED and remain so until it been reset. As for the voltage/current i not sure and the distance can be like 100 to 200 meter away.
The problem is: the open-detection circuit has to deal with the voltage/current that is normally present on the copper wire. That's what I'm looking for...a schematic for what is normally on both ends of the wire.

Ken
 

Thread Starter

555timer

Joined Feb 13, 2011
13
The problem is: the open-detection circuit has to deal with the voltage/current that is normally present on the copper wire. That's what I'm looking for...a schematic for what is normally on both ends of the wire.

Ken
ok, i will take measurement reading on that. sorry, i cant give you the schematic on the both end of wire. It is just purely just amplifier on the other end of wire.
 

SgtWookie

Joined Jul 17, 2007
22,210
Well, you started out with a wire that was ~50M when open, and ~50 Ohms when closed.
Now you have an alarm system of some type on one end, and a "purely just amplifier", whatever that is, on the other end.

What kind of alarm system is it? Burglar alarm? Machinery fault alarm?

Can you contact the manufacturer of the alarm and get more information?
 

Oclaf

Joined Mar 26, 2011
15
Not sure how relevant this is to what your wanting but this is a basic transistor latching circuit.
I guess you could hold the trigger low and run the signal from your "copper wire" through a NOT to pull the trigger high when the signal is lost.
Need more info on the existing circuit.
 

Attachments

SgtWookie

Joined Jul 17, 2007
22,210
There are problems with adding components to an existing alarm system. If you change the resistance of the alarm wire, it may trip continuously.

I really haven't worked with home alarm systems much, and it was a very long time ago. However, if the resistance in the loop is either too low or too high, the alarm will go off.

So, adding in something like the circuit Oclaf proposed could possibly cause the alarm to trip continuously, or perhaps not function at all when there was a fault condition.
 

Thread Starter

555timer

Joined Feb 13, 2011
13
There are problems with adding components to an existing alarm system. If you change the resistance of the alarm wire, it may trip continuously.

I really haven't worked with home alarm systems much, and it was a very long time ago. However, if the resistance in the loop is either too low or too high, the alarm will go off.

So, adding in something like the circuit Oclaf proposed could possibly cause the alarm to trip continuously, or perhaps not function at all when there was a fault condition.
:( ...sound so complicated. I just wan to monitor the alarm unit through LEDs.. sound easy but implement is hard...
 

Wendy

Joined Mar 24, 2008
22,141
If you measure the voltage compared to the negative lead on the battery, is it positive voltage or no voltage. I have a circuit in mind that may work. Basically I'm looking for a positive voltage to work with.

What is the power supply voltage I have to work with?
 

Thread Starter

555timer

Joined Feb 13, 2011
13
If you measure the voltage compared to the negative lead on the battery, is it positive voltage or no voltage. I have a circuit in mind that may work. Basically I'm looking for a positive voltage to work with.

What is the power supply voltage I have to work with?
should be positive voltage. The power supply should be 5V
 

CDRIVE

Joined Jul 1, 2008
2,219
Reading through this thread is like getting a tooth drilled without anesthetic. Your replies are like a guy who's been subpoenaed to testify against himself! You simply don't answer questions or give complete descriptions of the system you're dealing with. Without vagaries, describe the alarm system and the equipment it's protecting. Is it monitoring unauthorized access or failure of a machine or system, temperature etc?
 
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