CCTV NVR piezo alarm sounder to control a relay.

Thread Starter

azafayath

Joined Nov 13, 2023
7
I have a Hikvision CCTV NVR 7608 K1 without a built-in alarm output relay system. It supports motion detection triggering an alarm through a small onboard buzzer. Unfortunately, the buzzer's sound is too low. I need a basic circuit that uses a high-sound-output buzzer to trigger a relay.

Can you share a simple circuit for this?
 

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Ya’akov

Joined Jan 27, 2019
8,975
Adding to @MrChips’ suggestion, you could use the cheap and ubiquitous KY-038 sound sensor module*.

1699871375702.jpeg
The microphone can be desoldered and remotely mounted (using the shortest practically leads, preferably using a short shielded jumper) by literally gluing it over the port in the piezo buzzer. I would expect the sensitivity adjustment to have enough range to eliminate false alarms due to ambient noise, but if the ambient noise was particularly high you could insulate the mic/buzzer using a closed cell foam.

*The link is to a listing on Amazon but a search will find many other sources. The board is sold with at least two different microphones. The one picture uses a much smaller device soldered past the U shaped cutout in the board and is probably a better option. The other uses a large device soldered to the S and G pads on the arms of the U. It would work but the larger size might prove to be less desirable.

On the other hand, the large device is through hole and the smaller is usually surface mount, so depending on your confidence with soldering the larger device could be better for that reason.
 
Hi, friend. If you want to increase the alarm volume, you can use an external high-power buzzer instead of the built-in one. Here is a simple diagram for connecting a high power buzzer to your system:

Get a powerful buzzer that suits your volume requirement. Connect one wire from the buzzer to the "COM" output of the NVR, which is usually used to trigger the buzzer built into the NVR. Connect the second wire from the buzzer to the "NO" (usually "Normally Open") contact of the relay. When an alarm is triggered, the NVR will close the relay contacts (alarm) and sound the buzzer. This will allow you to use a powerful external buzzer instead of the built-in one for a louder alarm sound. Make sure that the buzzer and NVR operate compatible and that the voltage and current used in the circuit meet the requirements of the equipment.
 

Ya’akov

Joined Jan 27, 2019
8,975
Hi, friend. If you want to increase the alarm volume, you can use an external high-power buzzer instead of the built-in one. Here is a simple diagram for connecting a high power buzzer to your system:

Get a powerful buzzer that suits your volume requirement. Connect one wire from the buzzer to the "COM" output of the NVR, which is usually used to trigger the buzzer built into the NVR. Connect the second wire from the buzzer to the "NO" (usually "Normally Open") contact of the relay. When an alarm is triggered, the NVR will close the relay contacts (alarm) and sound the buzzer. This will allow you to use a powerful external buzzer instead of the built-in one for a louder alarm sound. Make sure that the buzzer and NVR operate compatible and that the voltage and current used in the circuit meet the requirements of the equipment.
Welcome to AAC.

This could work but it faces at least two problems.

First, it requires modifying the NVR PCB. Desoldering the existing buzzer and connecting an inductive load (the relay) to a place one is not expected.

Second, the image of the board suggests the current buzzer is of the passive type. This means the signal sent to the buzzer is something like a ~1KHz square wave, not a DC voltage. This may not be able to drive a relay at all.

If modifying the PCB is acceptable, removing the buzzer and measuring the signal at the pads would be the first step. Once that is known, designing a circuit that can safely and effectively use whatever the board is producing follows. It would probably include a solid state device (e.g.: MOSFET, BJT) as the active component triggered by the buzzer signal—not a relay.
 

Thread Starter

azafayath

Joined Nov 13, 2023
7
Hi, friend. If you want to increase the alarm volume, you can use an external high-power buzzer instead of the built-in one. Here is a simple diagram for connecting a high power buzzer to your system:

Get a powerful buzzer that suits your volume requirement. Connect one wire from the buzzer to the "COM" output of the NVR, which is usually used to trigger the buzzer built into the NVR. Connect the second wire from the buzzer to the "NO" (usually "Normally Open") contact of the relay. When an alarm is triggered, the NVR will close the relay contacts (alarm) and sound the buzzer. This will allow you to use a powerful external buzzer instead of the built-in one for a louder alarm sound. Make sure that the buzzer and NVR operate compatible and that the voltage and current used in the circuit meet the requirements of the equipment.
Thanks for your comment

however in my NVR doesnt have inbuilt alarm relay module
 

Thread Starter

azafayath

Joined Nov 13, 2023
7
Adding to @MrChips’ suggestion, you could use the cheap and ubiquitous KY-038 sound sensor module*.

The microphone can be desoldered and remotely mounted (using the shortest practically leads, preferably using a short shielded jumper) by literally gluing it over the port in the piezo buzzer. I would expect the sensitivity adjustment to have enough range to eliminate false alarms due to ambient noise, but if the ambient noise was particularly high you could insulate the mic/buzzer using a closed cell foam.

*The link is to a listing on Amazon but a search will find many other sources. The board is sold with at least two different microphones. The one picture uses a much smaller device soldered past the U shaped cutout in the board and is probably a better option. The other uses a large device soldered to the S and G pads on the arms of the U. It would work but the larger size might prove to be less desirable.

On the other hand, the large device is through hole and the smaller is usually surface mount, so depending on your confidence with soldering the larger device could be better for that reason.
Thanks for the guidance , Appreciated
 

Thread Starter

azafayath

Joined Nov 13, 2023
7
Adding to @MrChips’ suggestion, you could use the cheap and ubiquitous KY-038 sound sensor module*.

The microphone can be desoldered and remotely mounted (using the shortest practically leads, preferably using a short shielded jumper) by literally gluing it over the port in the piezo buzzer. I would expect the sensitivity adjustment to have enough range to eliminate false alarms due to ambient noise, but if the ambient noise was particularly high you could insulate the mic/buzzer using a closed cell foam.

*The link is to a listing on Amazon but a search will find many other sources. The board is sold with at least two different microphones. The one picture uses a much smaller device soldered past the U shaped cutout in the board and is probably a better option. The other uses a large device soldered to the S and G pads on the arms of the U. It would work but the larger size might prove to be less desirable.

On the other hand, the large device is through hole and the smaller is usually surface mount, so depending on your confidence with soldering the larger device could be better for that reason.


Appreciate your assistance and guidance.

In my understanding, if I have a sound detection module and remove both the buzzer ,microphone from both the PCB board and motherboard, connecting them with a short jumper,.

how can I connect a relay from the module? Could you please provide a concise illustration?
 

Ya’akov

Joined Jan 27, 2019
8,975
Appreciate your assistance and guidance.

In my understanding, if I have a sound detection module and remove both the buzzer ,microphone from both the PCB board and motherboard, connecting them with a short jumper,.

how can I connect a relay from the module? Could you please provide a concise illustration?
I am not sure you have it straight yet. Give me a bit to make a drawing so you can see what I mean.
 

Audioguru again

Joined Oct 21, 2019
6,620
The sound sensor module uses an LM393 comparator IC that has a very low output current of 4mA to 6mA that is much too low to drive a relay.
Its output goes low when sound is detected, then the output could drive a PNP transistor that drives a relay.
 

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Thread Starter

azafayath

Joined Nov 13, 2023
7
The sound sensor module uses an LM393 comparator IC that has a very low output current of 4mA to 6mA that is much too low to drive a relay.
Its output goes low when sound is detected, then the output could drive a PNP transistor that drives a relay.
Can you recommend a compact circuit?
 

Audioguru again

Joined Oct 21, 2019
6,620
I make my own circuits. Why would any company make the circuit you need?
We do not know the power supply voltage or current that your device has for a transistor to be added and drive a relay.
 

Ya’akov

Joined Jan 27, 2019
8,975
For what it's worth, I breadboarded a KY-038 module with a 2N7000 MOSFET and a 5V reed relay, and connected it to a small piezo buzzer using a piece of vinyl tubing that was a snug fit over the small condenser microphone element.

I realized that would be an easy way to provide electrical isolation and avoid desoldering parts. Though I didn't do it, because the setup was temporary, you'd want to use some hot glue or electronics grade silicone adhesive to hold the two ends in place.

It worked perfectly. I drove the buzzer with a function generator at 2KHz and after adjusting the threshold it was reliable and ambient noise did not trigger it.

Since you are happy with the relay-included board linked above, I won't document the arrangement further, but the description above requires only minimal experience to understand without that, so for posterity...
 
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