Analysis of Power Supply Problems of CCTV Microphone

  • source: sizheng;
  • Time: 2019-05-28

There are always users who have doubts about the power supply of the CCTV audio microphone when the CCTV microphone is connected to the network camera. Some customers use centralized power when installing the CCTV audio microphone, or share a power supply with the camera. Some may have poor sound quality of the CCTV audio microphone, the camera picture is not clear, and some users have not encountered such problems. Can the CCTV microphone share a power supply with the camera? Below we analyze this issue.

cctv mic power supply

1. The power supply mode of the CCTV microphone requires remote centralized power supply

(that is, centralized power supply at the audio recording device end/sound amplification device end), and its main purpose is to be more resistant to interference and noise. The CCTV microphone is generally powered by 12V DC regulated power. If the distance is very long, 15V can be supplied in the equipment room. Since the cctv mic is a very sensitive small signal amplifying device, it is sensitive to the clutter of the power supply, and it is necessary to use a clean high-quality DC stabilized power supply with small clutter.

A single cctv mic consumes approximately 1-20 mA of current, and a 1 amp DC regulated power supply can be used for several CCTV microphone simultaneously. There is no need to have a separate power adapter for each CCTV audio microphone.

The DC regulated power supply referred to here is a commonly known "transformer", which is generally composed of a power transformer, a rectifier diode, a filter capacitor, and an integrated voltage regulator.

Try not to use a switching power supply, it can cause a lot of circuit noise! Many switching power supplies on the market have poor quality and a very large ripple factor, which can cause the CCTV microphone to him. What is a switching power supply?

Simply put: the switching type DC stabilized power supply is an automatically regulated power supply composed of an electronic switch tube and an electronic switch oscillator. For example, a common desktop computer power supply is a switching power supply.


2. Common ground connection between the negative pole of the power supply and the audio ground

The audio ground of the CCTV microphone and the negative pole of the power supply are combined into one. It must be connected to the negative pole of the DC stabilized power supply and the ground of the audio input (Line In) of the audio equipment.

If the power ground and the audio ground are not well connected, the sound quality may be degraded or there may be no sound. If the ground of the Line In terminal of the audio device is not connected to the ground of the CCTV audio microphone, the sound will generally be very small.
(1) 3.5 Stereo plug: used for miser, IP network camera, etc.
(2)Lotus plug: mainly use for input and output plugs between audio equipment or video equipment
(3) BNC plug: it mainly use for connection between video equipment, but it is also used to input audio signals in many brands of hard disk recorders/cards.


3. Audio cable connection

Devices with audio signal lines and audio ground lines that can be directly connected:

Walkman headphones, active speakers, audio amplifiers, audio and video splitters, DVR Digital video recorders, video servers, mixers, recorders, sound cards or other audio devices with Line-In  liner input end(microphone interface is strictly prohibited).

3-1 DVR. DVRs all have corresponding audio input ports, generally coaxial cable BNC plugs. The CCTV microphone audio cable needs to be connected to the center pin position of the BNC plug. The CCTV microphone needs to be connected to the outer casing of the BNC plug (that is, the shielded copper mesh connecting the coaxial cable).

3-2 Active speakers with their own amplifiers. A set of ordinary active speakers are generally left and right only, corresponding to the left and right channels of the audio line. This CCTV microphone only provides one source, so it is a “mono” source. The audio cable of the CCTV audio microphone is connected to the left/right channel audio cable of the speaker cable, and the CCTV microphone is connected to the ground of the speaker cable in common.

3-3 Other methods of connecting audio devices such as amplifiers and mixers are equivalent to the above.

3-4 It is strictly forbidden to connect the audio pick up to the microphone (MIC) input of the sound card, mixer, amplifier, etc., otherwise the device may be damaged. This is because although the inside of the CCTV microphone also includes a microphone, it also includes circuits such as amplification, noise reduction, and echo processing, and outputs a "Line Out" audio signal of 1 Vpp or more.
3-5 Notebook computers are rarely equipped with a “Line In” audio input jack, usually only with a MIC input jack and a SPEAKER output jack. The CCTV microphone can't be directly connected to the MIC port. You can only purchase a professional external USB interface desktop sound card and use the “Line In” port to connect it.

3-6 The CCTV microphone audio cable can't be directly connected to two types of audio equipment. The audio surveillance microphone adapter must be connected to avoid deterioration of the sound quality due to impedance mismatch.

Note: Adjust the volume of your amplification device to a minimum during all connections or when you switch the switch to avoid an instantaneous electrical shock.



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