Camera TechnologyClock & Timer Circuit DiagramsRadio Circuit Diagrams

On-Train Radio Camera Schematic Circuit Diagram

Continuous Transmission and Rapid Response for Moving Trains

For effective surveillance, it’s crucial for the camera to transmit constantly while the train is in motion. Moreover, it should continue transmitting for a few minutes after the train comes to a stop. However, if the train restarts after a lengthy pause. The camera imagery must be transmitted immediately. Achieving this requires a power source that ensures uninterrupted operation. Rechargeable batteries are not suitable due to their slow charging time, and primary batteries pose environmental concerns. The ideal solution lies in GoldCaps, offering swift charging capabilities and ample reserve power to sustain the radio camera’s functionality for several minutes.

Swift Charging and Reliable Reserve Power

The power supply circuit, depicted in Figure 1, receives the incoming DC voltage from the left. This voltage is safeguarded against brief power interruptions by capacitor C1, ensuring continuous operation. The primary reserve power source comprises four GoldCaps connected in series, each with a rating of 22 F / 2.3 V. This configuration results in a net capacitance of 5.5 F / 9.2 V, providing a robust reserve power solution. It’s essential to maintain the charging voltage below the maximum limit of 9.2 V to ensure the GoldCaps operate effectively and reliably.

On-Train Radio Camera Schematic Circuit Diagram

Precise Voltage Regulation for GoldCaps Charging

Achieving reliable charging for the GoldCaps is made possible by a modern adjustable low-drop voltage regulator, specifically the LT1086. This regulator is finely tuned to a nominal output voltage of 9.57 V through the configuration of resistors R2 and R3. It accounts for the 0.6 V voltage drop across D5. The LT1086 is robust, capable of handling a current of 1.5 A with built-in current limiting. Even when the GoldCaps are completely discharged, they can be swiftly charged in a matter of seconds when the dc voltage is present. During this period, the GoldCaps are charged through D2. Notably, when the dc voltage is available, the camera draws power directly from the track via D4, with D5 preventing this voltage from reaching the capacitor bank. Additionally, D4 ensures the GoldCaps do not discharge via the track when no voltage is present, creating an effective OR gate.

Output Stage for Camera Power Supply

To power the radio camera, which requires 5 V and draws a current of around 70 mA. The circuit incorporates an output stage. This stage consists of a conventional 7805 fixed voltage regulator alongside the standard capacitors (C9, C10, C11). The presence of these components ensures a stable power supply for the camera. The circuit incorporates two low-current LEDs as indicators, revealing the presence of voltage on the track and the charging status of the storage capacitors. While these LEDs are optional, they provide valuable visual cues. It’s crucial to position the 100-nF capacitors as close as possible to the voltage regulators for optimal performance and stability.


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