I would like my burgler alarm system to email me pictures from my security cameras. The alarm outputs a 12vdc signal, but the security camera nvr needs just a dry contact. 1. Should I use a mechanical relay? 2. Should I use a transistor? 3. If I were to use a transistor, what would be the simplest way to accomplish this?
Thank you.

 

Those output signals are usually ready to be connected to a relay, that is their purpose. Without knowing the specs of the alarm we could not tell, but I am 99% sure if it is dedicated output 12V signal that the alarm is triggered, it can go to relay.

 

A relay (reed relay?) would be a solution, as would an opto-isolator. Either would provide full isolation between the devices, which a transistor would not. Its possible that isolation is not necessary, but simplest to put it in.

 

Please explain how would you use reed relay for this application. (???)

Just get a 12V relay module, you have DIN mount variants for easy mounting and that's all folks.

 

How to use a reed relay??? Use it in a manner similar to using any other sort of relay. But not at all like using the automotive cube relays that are used for many suggested schemes here.

A reed relay has coil terminals and contact terminals. Usually the contacts are normally open, they will each get a wire attached to connect to the security camera "NVR" terminals. The two coil terminals of the reed relay will be connected to the alarm 12 volt output connection.
It will need to be a reed relay specified for 12 volt DCoperation.

 

In my vocabulary this is a reed relay:

 

Hello,

What you are showing is a reed switch.
A reed relays has a coil around it.

Bertus

 

Fair enough. Although if you google "reed relay" the most of the results are like on my picture. Also where I am from that relay "switch" is sold as reed relay.

 

In my vocabulary this is a reed relay:
View attachment 340259

To control the sealed contacts, you need either a permanent magnet or a coil attached to it. By applying voltage to the coil, we obtain a magnetic field. The magnetic field causes the contacts to close.

 

In my vocabulary this is a reed relay:
View attachment 340259

That is not a reed relay, but the 'reed' from one. Just as the contacts of an automotive relay are not a 'relay' without the coil.

 

 

Fair enough. Although if you google "reed relay" the most of the results are like on my picture. Also where I am from that relay "switch" is sold as reed relay.

When I search the web for "reed relay" I get pictures of reed relays not reed switches. I believe you are mistaken about the nomenclature, even where you are from. A reed switch, which is the subject of your photo, is the moving bit of a reed relay, but it is also a part in its own right and so must be able to be specified independently.

If you call that part a "reed relay", how can you call out a "reed switch"?

 

As I can see in our stores, everything goes under reed relay: reed relays with metal enclosure, reed relay IC, switches (sensors)... As I said, fair enough, it was a language barrier that we overcome.
Of course the TS can implement what they want with a reed relay.

 

When Radio Shack was still around, I had been known to buy a reed relay to extract the reed switch when I needed one.

Reed relays usually require very little current ro activate. But they're designed for low-current or signal switching.

 

When Radio Shack was still around, I had been known to buy a reed relay to extract the reed switch when I needed one.

Reed relays usually require very little current ro activate. But they're designed for low-current or signal switching.

Low current, yes, as well as high speed, small size, and low resistance contacts. Used extensively in RF, telecom. and digital applications.

 

IIRC I have seen them used to the switching of chanels in a very old VHF marine transceiver.

 

IBM 029 and 059 card punch and verifiers came in models that used cards of 5PST reed relays for all the logic.

 

Probably the person making the labels at the store the Ts mentioned would not know the difference between a reed relay and a buffalo burger. But ignorance does not define reality. AND (deleted)