An article on understanding camera power supply: from interface selection to construction pit avoida

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In modern security systems, powering surveillance cameras is a critical aspect of solution design and installation. Understanding power supply interfaces, specifications, and various power methods not only ensures smooth and efficient project completion but also prevents equipment failures and instability issues. This article provides a comprehensive analysis of camera power supply knowledge, covering both home and industrial cameras.

1. DC Round Port Power Supply: The Most Traditional Method

Most home and some industrial cameras use DC round port power supply, which may appear simple but has precise specification requirements.

Universal DC Interface Specifications:

• Plug Outer Diameter: 5.5mm (Tolerance ±0.05mm)

• Plug Inner Diameter: 2.1mm (Tolerance -0/+0.1mm, i.e., 2.1-2.2mm)

• Polarity Configuration: Power adapter plug has positive pole inside and negative outside; the camera interface is reversed, with negative inside and positive outside

Special DC Interfaces: Panoramic cameras (fisheye cameras) use smaller DC interfaces:

• Outer Diameter: 3.5mm (Tolerance ±0.05mm)

• Inner Diameter: 1.35mm (Tolerance -0/+0.1mm)

• Polarity configuration same as universal adapters

Power Supply Principle: Household 220V AC power must be converted to DC through a power adapter to supply cameras. DC is characterized by constant current direction, making it ideal for electronic devices.

💡Physics Lesson

• Direct Current (DC): Current flows consistently in one direction, with voltage and current polarity remaining constant. Common in battery-powered devices like flashlights and mobile phones.

• Alternating Current (AC): Current direction and magnitude change periodically, typically represented by a sine wave. Household and industrial power primarily use AC, commonly at 220V or 380V.

Household power is 220V AC, requiring a power adapter to convert to DC. As long as the adapter output voltage meets the camera requirements, it can supply power normally and is considered a universal device.

2. PoE Power Supply: Modern Intelligent Choice

PoE (Power over Ethernet) is a technology that transmits both data and electrical power through network cables, widely used for its simplicity, safety, and standardization.

Standard PoE Power Supply:

• Power supplied through pins 1236 or 4578 of the network cable

• Pins 1236 transmit data simultaneously

• Complies with IEEE 802.3af and IEEE 802.3at power supply standards

• Wide applicability and strong compatibility

Non-standard PoE Power Supply:

• Directly provides fixed 12V, 24V, 48V, or 54V voltage

• Regardless of whether terminal devices support PoE

• Requires matching custom equipment and cannot be mixed arbitrarily

• For example, TP-Link's TL-IPC5Y36F-A only supports Passive PoE power supply

3. Centralized Power Supply: Preferred Solution for Large Projects

In security installations, centralized power supply solutions allow unified control and management of power, reducing the amount of wiring required.

However, centralized power supply often suffers from insufficient power issues, causing IPCs to fail to boot or repeatedly restart at night. Solutions include:

1. Appropriately increase the power supply output voltage (adjust at the +V ADJ position with a screwdriver)

2. If using network cable for power, use a 2+2 method where pins 4 and 5 are combined as positive, and pins 7 and 8 are combined as negative to reduce impedance

3. Replace with better quality, thicker gauge power cables (such as pure copper/0.75mm, etc.)

4. Understanding Power Supply Specifications

Camera labels indicate operating voltage and power requirements, which are key criteria for selecting power adapters.

Voltage Requirements: Cameras typically have three operating voltage specifications: 12V, 9V, and 5V. The power adapter voltage must match the device's rated voltage; you cannot use a 5V adapter for a 12V camera, nor a 12V adapter for a 5V camera.

Power Requirements: According to the formula: Rated Power = Rated Voltage × Rated Current

For example: If a device is rated at 12V with 6W power, the power adapter should be at least 12V/0.5A. To ensure stable operation, a 12V/1A adapter is recommended.

With consistent voltage, current can exceed the rated current. Regarding excessive current: the device will draw power as needed without being damaged by higher adapter current (only wasting energy).

 

Power Adapter Selection Core Parameter Comparison Table

Selection Dimension	Core Requirement	Common Misconceptions	Risk Consequences
Output Voltage	Must exactly match device rated voltage (e.g., 12V device with 12V adapter)	Thinking "higher voltage than rated works" or "just avoid voltage that's too low"	Too high: damages electronic components, burns device, may cause short circuit/fire; Too low: device fails to start, unstable operation (lagging/dropping offline), long-term operation damages circuit
Output Current	Adapter rated current ≥ device rated current (e.g., device requires 2A, adapter should be 2A or higher)	Pursuing "higher current is better" or "current slightly lower than device is okay"	Insufficient current: inadequate power supply, device cannot operate normally; Excessive current: device draws as needed, won't be damaged by higher adapter current (only wastes energy)
Interface Polarity	Must completely match device interface polarity (e.g., center positive/outer negative or center negative/outer positive)	Ignoring polarity labels, connecting arbitrarily	Reverse connection directly burns internal circuit, irreparable damage
Interface Specification	Adapter interface dimensions (diameter/plug type) must perfectly fit device interface	Using "fits loosely" as judgment standard, ignoring loose connections	Poor contact causes power interruption, abnormal operation, long-term looseness may cause overheating

Supplementary Key Notes

1. Voltage is a "hard matching item" with zero tolerance - must precisely correspond to device rated voltage (e.g., 5V device must never use 9V/12V adapter).

2. Current is a "minimum matching item" - adapter current can exceed device requirements but cannot be lower, otherwise failure due to insufficient power will occur.

3. Polarity is usually marked on the device power interface or adapter (e.g., "center + outer -"), verify before connecting.

 

Device and Adapter Matching Checklist

Check Step	Check Content	Pass Standard	Check Method	Remarks
1	Device rated voltage	Adapter output voltage exactly matches device rated voltage (e.g., 12V device must have 12V adapter)	Check "rated voltage" on device nameplate/manual, compare with "output voltage" on adapter casing	Voltage mismatch means direct rejection, zero tolerance
2	Device rated current	Adapter output current ≥ device rated current (e.g., device marked 0.5A, adapter must be ≥0.5A)	Read device "rated current/working current", confirm adapter "output current" meets minimum requirements	Current can be slightly higher without damaging device, only provides power margin
3	Interface polarity	Adapter polarity exactly matches device requirements (center positive/outer negative or center negative/outer positive)	Check device power interface label (e.g., "+", "-" symbols), compare with adapter casing polarity marking	Polarity error directly burns device, must be carefully verified
4	Interface specification	Adapter interface dimensions, plug type perfectly match device interface	Physical plug test (must be secure without looseness), or verify device interface diameter (e.g., 5.5mm×2.1mm)	Looseness causes power interruption and overheating; mismatched interface requires plug replacement (polarity must remain unchanged)
5	Power type	Adapter type (DC/AC) matches device requirements	Device marked "DC input" requires DC adapter, avoid using AC adapter for direct power	Most electronic devices (e.g., cameras) require DC power
6	Additional function compatibility (if applicable)	When device requires special power functions (e.g., POE, wide voltage), adapter must support corresponding functions	Check device manual for special power requirements, confirm adapter function compatibility	When no special requirements, satisfying first 5 items is sufficient

Usage Instructions

1. Check item by item; compatibility requires meeting "pass standard" for every item. Any item not meeting standard means unusable.

2. When checking, prioritize device nameplate and adapter casing labels; consult product manual when information is unclear.

3. If replacing a connector (e.g., interface size mismatch), only physical connector may be replaced; voltage, polarity and other core parameters cannot be changed.

5. Special Scenario Power Solutions

Vehicle Power Supply:

• Small vehicles: Use cigarette lighter socket to DC power conversion

• Large vehicles: Use dedicated battery output for stable DC power

• Note: Large transport vehicles are generally 24V, small cars are generally 12V. 24V requires a step-down converter to 12V to power most cameras

Solar Power Supply: Solar power systems (e.g., TL-ZJ800&TL-K234) output 12V DC power with maximum output current up to 5A, meeting multi-scenario requirements.

Note: Currently solar power systems can power up to three loads maximum, with built-in DC-DC circuit for voltage regulation, outputting stable 12V.

International Power Supply: When using surveillance equipment in different countries, pay attention to differences in power interfaces and specifications:

• For devices requiring 12V DC, use local power adapters to provide 12V power

• For devices requiring AC mains power, interface and voltage adaptation is needed

• Two-pin plug devices usually support 110V-240V wide voltage and work normally with US standard outlets

• For devices requiring 220V, an inverter is needed to convert voltage to 220V

• For three-pin 220V devices, a US converter plug is needed before connecting to inverter

6. Frequently Asked Questions

1. What is the typical power cable length for cameras, and do they support extension cords?Camera power cables typically come in 3m and 5m specifications, supporting external DC extension cords. It is recommended to use 0.5mm oxygen-free copper or better quality cables to reduce line loss.

2. How to use standard PoE power for non-PoE cameras?A PoE splitter can be used to separate power and data signals from standard PoE lines into DC power and network interface, enabling non-PoE camera connections.

3. If cameras support both DC and PoE, what is the power priority?For IPC products, there is no explicit power priority; whichever power method provides higher voltage will be used.

4. What are the voltage, current and power specifications for IEEE 802.3af and 802.3at standards?

Standard	PSE Power	Voltage Range	Max Current
IEEE 802.3af	15.4W	44-57V	350mA
IEEE 802.3at	30W	50-57V	600mA

Conclusion

Camera power supply is a fundamental aspect of security surveillance systems that cannot be overlooked. Choosing appropriate power supply methods, understanding various interface specifications, and knowing solutions for special scenarios not only ensure stable operation of the surveillance system but also improve construction efficiency and quality. We hope this article provides practical reference value for your engineering projects.