Video Surveillance cameras are becoming more common today as new technology is making it easier and more cost effective for broad use. IP Network, analog security, thermal imaging, video doorbell and baby or pet monitors are examples of the diverse application base. Within these different devices there are three main motor applications; Infrared (IR) filter, lens motors (zoom and focus) and camera motors (pan and tilt). Figure 1 provides and overview for these different functions and Table 1 provides a list of devices with system benefits.
Infrared cut filters are a common application in cameras to help achieve both day and night vision. Most cameras sensors can see the whole visible light and IR spectrum which is advantageous in dark settings but during the day the IR waves need to be blocked. Low voltage brushed DC motors can be used to move this filter in and out of place. Device such as the DRV8210P provide a small footprint for space conscious boards that can reduce a layout size by up to 93% when compared to a discrete design as shown in Figure 2.
Another benefit of an integrated design is low-power sleep mode for when the motor is not in operation which helps to conserve power and battery. The IR filter only needs to move a few times a day so insuring that the motor driver is not draining too much power when idle is important. Lastly the DRV8210P also integrates protection features such as thermal shutdown, under voltage lockout and overcurrent protection to increase system reliability.
Video surveillance is becoming more advanced with the adoption of lens motor driving to zoom and focus the image. Older cameras have a way to manually change the zoom but today this same function is achieved through low torque stepper motors. To drive these motors, TI offers a range of benefits to fit different designs such the DRV8410, DRV8411 or DRV8411A. The DRV841x family offers advanced sensing and control, industry common footprint, low-power sleep mode and is cost competitive. DRV8410 and DRV8411 provide design flexibility in the industry common 5.00mm × 6.2mm, 16-pin HTSSOP package while DRV8411A takes integration a step further by included integrated current sensing. Figure 3 shows that by adding this feature, external sense resistors are no longer need.
The DRV8411A does not require these external sense resistors to sense current because the device performs this function internally. Check out the Advantages of Integrated Current Sensing Application Note for more information. This device also creates a proportional, scaled down current that is sent out through the “IPROPI” pin (IPROPI = Current proportional Current) allowing for further diagnostic ability.
The DRV8410, DRV8411, and DRV8411A are also available in a 3mm × 3mm QFN package which becomes adventitious when trying to make smaller
The last area to discuss is the pan and tilt functions that allows for the camera view to be changed left or right and up or down. This function requires more torque than the lens zoom features because now the whole camera is moving and not just the lens. For this application there are a couple different options starting with the DRV8845. This device is able to support the higher torque load but comes with minimal features to provide the benefits of integrated drivers but also be cost competitive in an industry common, 36-pin QFN package.
DRV8434A which adds a couple more features, notably this device has sensorless stall detection. The DRV8434A is able to detect the change in phase between the motor winding and back-EMF. By detecting back-EMF phase shift between rising and falling current quadrants of the motor current, the DRV8434A can detect a motor overload stall condition or an end-of-line travel. Without Stall Detection, the driver continues to drive through the obstacle, causing heating, audible noise and damage to the system. Figure 4 shows this shift.
This article detailed just a few key considerations when selecting a motor driver for an IR cut filter, zoom and focus and pan and tilt but there are still many more ways to implement these features. TI motor drivers provided a wide range of voltages, currents and features to help meet the design needs for IP Network cameras, analog security cameras, thermal imaging, video doorbell and baby or pet monitors.
Function | Application | TI Device | Benefit |
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IR Cut Filter | Control the amount of IR light that passes through to the camera sensor, allowing for night visionLow-voltage brushed DC motors | DRV8210P | Single H-Bridge 1.65V to 11V, 1.76A |
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Lens Motors Zoom and Focus | Open loop system with no sensors to change field of view Low torque stepper motors | DRV8410, DRV8411 | 1.65V to 11V, 2.5A and 4A dual H-bridge motor driver with current regulation |
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DRV8411A | 1.65V to 11V, 4A dual H-bridge motor driver with current regulation and IPROPI | |||
DRV8847 | 18V, 2A dual H-bridge motor driver with current regulation and independent Half-bridge control | |||
Camera Motor Pan and Tilt | Open loop system with position feedback to move camera up, down, left, and right Higher torque stepper motors | DRV8845 | 35V, 1.5A quad H-bridge motor driver with Smart Tune technology |
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DRV8849 | 35V, 1.5A quad H-bridge motor driver with Smart Tune and integrated current sensing | |||
DRV8434A, DRV8434S | 48V, 2.5A dual H-bridge motor driver with integrated current sensing and stall detection (S Version has SPI) | |||
DRV8428 | 35V, 1A dual H-bridge motor driver with integrated current sensing and 1/256 micro-stepping |
For more information, see https://www.ti.com/motor-drivers/.