Table of Contents
- Symptom Diagnosis
- Voltage Checks
- Cable Resistance Issues
- Power Supply Sizing
- Indian Power Quality Issues
- UPS and Surge Protection
- FAQ
Symptom Diagnosis
When a CCTV camera does not turn on, the cause is almost always in the power supply chain. Diagnose by symptoms:
- No LED, no image, no heat on camera: No power reaching camera. Check supply output, fuse, cable continuity.
- Camera LED on, no image on DVR: Power OK, video signal issue. Check BNC connector, video cable continuity, DVR channel setting.
- Camera works intermittently: Voltage drop under load, loose connection, corroded terminal. Check all terminals and voltage under load.
- Camera image has horizontal bars or roll: Ground loop or voltage ripple. Add ferrite core to power cable or use isolated power supply.
Voltage Checks
CCTV cameras typically run on 12V DC. Minimum operating voltage is usually 11V (some cameras 10.8V). Measure at each point in the supply chain with a multimeter:
- At power supply output terminals: should read 12.0-12.5V no-load
- At the far end of camera power cable: should read 11.5V+ under load
- At camera power connector: same as cable end
If PSU output is correct but camera voltage is low: cable resistance is the problem. If PSU output is low: PSU is overloaded, failing, or input voltage issue.
Cable Resistance Issues
Common in Indian CCTV installations. Two causes:
- Long cable runs: At 30m with 18AWG copper-clad aluminium wire (common in India): resistance = 2 x 30 x 0.06 ohm/m = 3.6 ohm. At 500mA camera current: V drop = 500mA x 3.6 = 1.8V. Camera gets 12 – 1.8 = 10.2V = too low.
- CCA (Copper-Clad Aluminium) vs solid copper: CCA wire has 1.5-2x higher resistance than solid copper. Indian market CCTV cable is predominantly CCA. For runs over 20m, use solid copper wire or 16AWG thicker cable, or use a dedicated power supply closer to the camera.
| Cable Length | Max Current (CCA 18AWG) | Max Current (Copper 18AWG) |
|---|---|---|
| Up to 15m | 500mA (0.9V drop) | 500mA (0.6V drop) |
| 15-30m | 300mA (1.1V drop) | 500mA (1.2V drop) |
| 30-50m | 200mA (1.5V drop) | 400mA (1.9V drop) |
Power Supply Sizing
Calculate total camera current draw: sum all camera specifications (usually 300-600mA each) and multiply by 1.5 for safety margin. A 4-camera system with 500mA cameras needs: 4 x 500mA x 1.5 = 3A minimum. Use a 5A PSU to allow for PTZ motor spikes. Common Indian CCTV power supplies: 12V 5A (Rs 300-500), 12V 10A (Rs 600-1,000), 12V 20A (Rs 1,200-1,800).
Indian Power Quality Issues
- Low voltage (brownout): Indian 230V supply frequently sags to 180-200V during peak hours (evenings 7-10pm). Switching power supplies handle this well (85-265V input range). Linear regulators do not compensate and output drops proportionally.
- High voltage spikes: Generator switchover, lightning nearby, or inductive loads on the same circuit. Can destroy unprotected switching supplies. Use MOV (metal oxide varistor) or TVS diode across supply input.
- Power cuts: Average Indian city: 30-60 minute cuts per day. UPS essential for 24/7 recording continuity.
UPS and Surge Protection
For Indian CCTV installations: minimum 600VA offline UPS (Rs 2,500-4,000) for DVR + 4-camera system. This provides 30-60 minute backup during cuts. Online (double-conversion) UPS provides better surge protection and zero switching time. Add a Rs 200-400 surge protector plug strip between UPS and CCTV equipment for additional protection from line spikes during power restoration.
Frequently Asked Questions
My cameras work during the day but fail at night – why?
Night vision IR LED arrays draw significantly more current than daytime operation (IR LEDs can add 200-400mA per camera). If the power supply is marginal for daytime use, IR LEDs push it over capacity at night. Measure camera current consumption with a multimeter in series during day (IR off) and night (IR on) to confirm. Upgrade to the next size power supply or add a second supply dedicated to night operation.
My DVR shows video for some cameras but not others on the same power supply.
Diagnose each failing camera independently: measure voltage at camera terminal. If low voltage: cable length or resistance issue specific to those camera runs. If correct voltage but no video: check BNC connector and coax cable for the failing cameras. If camera is warm to touch but no video: camera may have failed.
Why does my CCTV image have a rolling bar or hum?
Ground loop caused by different ground potentials between the camera location and DVR location. Occurs when camera ground (via power cable) and video ground (via coax cable) have different potentials. Solutions: use video ground loop isolator (Rs 100-200 per camera), use a common ground for all cameras and DVR, or use video balun with Cat6 cable (eliminates ground loop issue entirely).
Is it safe to run two separate power supplies for CCTV cameras?
Yes, commonly done in large installations. Ensure each PSU is correctly sized for its subset of cameras. Ground both PSU outputs together at the DVR if they share a common ground reference. Do not parallel two 12V PSUs directly to the same camera without current-sharing circuitry as slight voltage differences cause one PSU to bear all the load.
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