Cheap LED Alarm Light ?

Chocman

Chocman

Young grasshopper
Feb 22, 2019
71
8
Leicestershire, UK
Has anyone any suggestions on where to start looking for a hard-wired LED alarm light or experiences of using them? Something I can hard-wire to the NVR, which flashes when an alarm situation occurs? I know my NVR has an Alarm Out port, and I think a little visual deterrent would be a possitive add-on. I'm not after an all singing and dancing light, just something basic that makes it perfectly clear, that intruder alert has been activated.
 
Thanks @looney2ns, I honestly didn't realise that a basic 'strobe light' could be used in this situation, and simply wired in to the NVR. I've a lot to learn!
 
Having looked at @looney2ns links further, I am after something much more subtle - it's for a domestic property, nice neighbours very nearby and with the amount of false alarms I get, something as glaring as a full on strobe light would cause me an awful lot of grief & complaints. Any tthoughts from the community on a more subtle LED light?
 
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Chocman said:
Having looked at @looney2ns links further, I am after something much more subtle - it's for a domestic property, nice neighbours very nearby and with the amount of false alarms I get, something as glaring as a full on strobe light would cause me an awful lot of grief & complaints. Any tthoughts from the community on a more subtle LED light?
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Automotive LED floods or spots are 12VDC, made for outdoors and can be EXTREMELY bright.

LED_flood.jpg
 
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I assume you're just looking for something bright that will light up if the alarm goes off. The Alarm Out port is basically just a switch that closes, so you need to wire up a light and a power adapter. You can use something like this:

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Plug the DC adapter into one of the pigtail connectors. One of the pigtail leads then connects to one lead of the LED light using a standard twist-on wire connector, or a female-to-female crimp, or solder and heat shrink depending on your skill level. The other lead of the LED light, and the other pigtail lead, connect into the Alarm Out terminals on the DVR. You may need a wire stripper to peel back the insulation for the leads. Make sure you get the polarity of the LED light connected correctly, or it won't turn on.

This is overkill because you're getting more parts than you need, but it will work. You can also use the flashing light suggested by @Old Timer in his post if you want something that flashes instead of just lighting up.
 
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I suggest knowing the rating of the alarm output. On my 5216-4ks2 it's 1 amp DC and half amp AC. For myself I'd hold to 50% of the rating because the relay is soldered to the motherboard and I don't want it to break.
 
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+1^^.
Decent $5 Opto-isolated relay board discussed here (these are 5VDC but 12VDC units are available and the schema is the same).

Also, 12VDC versions available like these.

5v_opto-relay_board.jpg
 
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Many thanks for your replies, all very helpful. I'll have a ponder and a good look at all the suggestions.
 
@TonyR I'm getting into this now thanks to the communities assistance. I've seen you've posted several comments previously on Alarm Out wiring etc. and have a lot of knowledge in this area. If I followed the suggestion of @wtimothyholman (comment above), do I need a Opto-isolated relay board ? What is the role of this unit?
 
Chocman said:
do I need a Opto-isolated relay board ? What is the role of this unit?
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It depends on the current the light is drawing. If the current is too big for the NVR alarm contact then a relay acts like another switch that can handle larger current loads.

The NVR contacts will switch power to the relay, the relay turns on and switches the light.
 
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Got it! I wont need a relay then.

I'm planning on fitting a low wattage/current light, just something that would be noticed rather than light up the whole neighbourhood! It's purpose is purely to alert an intruder that an alarm has been activated once breach of intrusion zone occurs. A visual 'silent alarm' if that makes any sense...
 
I should also mention that it is advisable (and likely required) for this light not to be mains voltage, a safe low 12v is ideal. I would not trust the NVR's contacts with mains voltage.
 
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Chocman said:
Having looked at @looney2ns links further, I am after something much more subtle - it's for a domestic property, nice neighbours very nearby and with the amount of false alarms I get, something as glaring as a full on strobe light would cause me an awful lot of grief & complaints. Any tthoughts from the community on a more subtle LED light?
Click to expand...
It may be overkill for this one situation, but if you are at all considering smart home gadgets, this might be a good time to jump in. I have my Smartthings hub flash my kitchen, bedroom, and living room lights if any of my fence gates are opened or any outside motion is detected after a certain hour if my alarm is armed.
 
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Chocman said:
@TonyR I'm getting into this now thanks to the communities assistance. I've seen you've posted several comments previously on Alarm Out wiring etc. and have a lot of knowledge in this area. If I followed the suggestion of @wtimothyholman (comment above), do I need a Opto-isolated relay board ? What is the role of this unit?
Click to expand...
It depends. The need for an external and optically isolated relay boils down to several things, any one should prompt its use:
  • If the alarm contacts inside the NVR or camera are not "dry" relay contacts but instead are a solid state output. The optical isolator portion of the external relay will help protect the solid state output. External inductive loads, like the coil of a relay, can produce back EMF when the coil is switched off and its collapsing field can damage a solid state output.
  • If it is desirable to switch something that draws more current than the camera or NVR output can handle.
  • If the device to control by the camera or NVR is NOT powered by low DC voltage but is instead typical 120VAC line voltage (called "MAINS" in your area).

For me, $6 or $10 for an external, optically-isolated relay board is a trivial amount to spend to help protect a relay inside a $100 camera or $300 NVR that if damaged even accidentally, could be difficult or close to impossible to repair. I always recommend using one.
 
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TonyR said:
It depends. The need for an external and optically isolated relay boils down to several things, any one should prompt its use:
  • If the alarm contacts inside the NVR or camera are not "dry" relay contacts but instead are a solid state output. The optical isolator portion of the external relay will help protect the solid state output. External inductive loads, like the coil of a relay, can produce back EMF when the coil is switched off and its collapsing field can damage a solid state output.
  • If it is desirable to switch something that draws more current than the camera or NVR output can handle.
  • If the device to control by the camera or NVR is NOT powered by low DC voltage but is instead typical 120VAC line voltage (called "MAINS" in your area).

For me, $6 or $10 for an external, optically-isolated relay board is a trivial amount to spend to help protect a relay inside a $100 camera or $300 NVR that if damaged even accidentally, could be difficult or close to impossible to repair. I always recommend using one.
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@TonyR's advice is very sound. One thing that you've not indicated is the NVR model. What are the current / voltage ratings for the Alarm Out contacts? Knowing that would help in figuring out if the contacts are (for example) open collector / open drain, mechanical, or opto-isolated on the NVR circuit board.

I deliberately chose an LED light with a low current (150 mA) in my previous post, just to be on the safe side, under the assumption that you're not experienced in electronics or electricity (hence your original question). I wanted to make it as simple as possible, but make it bright enough to notice. But if you really want to minimize risk to your equipment, then follow @TonyR's recommendation and learn how to use the opto-isolator module. Or at the very least, find out the maximum current voltage / current ratings of the Alarm Out contacts. If you see something like 120 VAC @ 1 A in the technical specs, then the circuit I suggested may work fine.
 
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This has become an incredibly useful and beneficial thread for me (thanks again to all for invalable contributions) and I really do hope it also helps others too, who may have similar matters to consider. I wish I'd studied electrical engineering at school rather than chemistry or woodwork, it would have been far more useful now I'm into my mature(r) years!:)

@TonyR - totally agree with you that for a few $/£'s investment in a optically isolated relay it is a better decision than frying an NVR. I'm not sure what a 'dry' relay contact means, but I'm guessing my NVR is solid state?
@wtimothyholman - remiss of me not to have included NVR details in my footer, I've updated this just now - it's an Dahua NVR 5216-16P 4KS2E (from Andy) and I'm about to check the the spec of the max current output of the Alarm Out port. You are 100% I'm not experienced in electronics/electricty, but willing to spend time working things out, once I've got the gist of things....
@Jessie.slimer thank you for your comment, very helpful - I'm very into Smart Home tech, next on my list of things to install & planned in - so it's possible to link an NVR to a Smartthings hub, is that what you've done?
 
Chocman said:
so it's possible to link an NVR to a Smartthings hub, is that what you've done?
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I have Blue Iris, so mine is compatible with a little work around, but an NVR should be able to work as well. If not by software, you can hook a cheap zwave door/window sensor that has contacts (such as Ecolink) to your NVR or camera relay output. This sensor will then trigger your smarthome hub to do any number of things using other smart locks, lights, openers that you may have.
 
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