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Common troubleshooting of reversing camera

by:Eagle Mobile Video     2019-12-28
Common troubleshooting of reversing camera 1: When reversing, the displayed image shakes, or there are more interference lines on the image, and sometimes it cannot be switched to the reversing image. Analysis and maintenance: the fault mainly occurs on some models of German cars and American cars. The reason is that after the engine is started, the output voltage interferes greatly, and it is not pure direct current that supplies reversing lights, instead, a pulse signal is superimposed ( Test with oscilloscope, its waveform is a square wave signal). During the modification, the power supply line of the camera is directly placed on the reversing lamp. If there is no filter circuit inside the reversing camera, the working voltage fluctuation will cause the camera to work abnormally, the output video signal is not normal, so the above fault phenomenon occurs. There are two main solutions to the fault: one is to add a primary filter circuit to the power supply input of the camera, and the specific circuit is shown in figure 8; The second is that the power supply line of the camera is not connected to the reversing lamp, but is connected to ACC by adding a relay, and the coil of the relay is connected in parallel with the reversing lamp, I . e. the reversing lamp power supply is used to control the on/off of the relay, and the camera's power ground wire and video ground wire directly ride the body iron. Fault phenomenon 2: The displayed picture is opposite to the actual situation. Analysis and maintenance: There are two solutions to this failure: one is to set the parameters of the display, refer to the data of the display, enter the factory mode of the display, and find 'acc mir- ROR ', modify the value of this item, if it is' ON ', change it to' OFF ', if it is' OFF ', change it to' ON '; The second is to change the camera image output settings, set it to non-mirrored output, or replace the camera with a non-mirrored camera. Fault phenomenon 3: The color of the image is not correct. During the shift switching process from D block to P block, it is necessary to reverse (R) The position of the gear, as shown in Figure 17, will add a sudden voltage pulse to the reversing camera at this time. In the long run, it is easy to cause damage to the camera, especially the cheap camera, however, the color is normal when the display displays the DVD navigation screen. Analysis and maintenance: the fault phenomenon should be caused by the wrong format of the camera output signal. On the one hand, the setting of the host can be adjusted to make it correspond; on the other hand, the camera can be disassembled to change the format of the camera output video signal. For example, the 14 legs of BF3003 reversing camera's main chip are the switching terminals of PAL system and NTSC system, as shown in Figure 15, the system switching can be carried out by removing the 0Ω resistor on the back, as shown in Figure 16. In addition, removing the 8-pin integrated block in Fig. 16 can remove the marking and remove the mirror image function. Fault phenomenon 4: when the car is in the reverse state, the host can switch to the rear view state, but there is no image display. Analysis and maintenance: When troubleshooting the fault, after confirming that the video connection and grounding wire are properly connected, it can be determined that the fault is caused by camera damage. From the actual repair situation, the reversing camera installed in the automatic car is more damaged. The reason should be from the parking (P Block)Go to the car (D Block) Or the damage from the camera is mostly internal 12V to 3. 3 v dc-The DC conversion circuit is damaged. For illustration, the internal circuit of BF3003 reversing camera is attached. As shown in Fig. 18, the input 12V voltage is reduced by U2 and U3 and then output 3. 3 V, supply the main chip. If U2 or U3 is damaged, it will result in No 3. 3V voltage output, main chip does not work, no video signal output. Since U2 and U3 are difficult to buy, 1084-3. 3 for overall replacement, about to 1084-3. Of 3 (Lose people) Connect the negative end of diode D1, pin ② to the positive end of C5, and pin ① to ground. In addition, in order to avoid the sudden voltage impact of the automatic car on the reversing camera during the shift process, a primary power-on time delay circuit can be installed, and the dual voltage comparator LM393 (U1), MOSFET tube (V1)The components are as shown in Fig. 19. The circuit is connected in parallel with the reversing lamp, V1 is the power supply control tube of the reversing camera, R3 and R4 form a voltage dividing circuit, and the inverted terminal voltage of the comparator is set to 6 V. When switching to the R Gear, the reversing light is on, the 12V voltage is charged to the capacitor C1 through the resistor R1, and the voltage across C1 begins to rise. In this process, because the ② pin voltage of U1 is higher than the ③ pin voltage, the ① pin outputs a low level, V1 is off, and the reversing camera does not work. When the voltage across C1 exceeds 6 V, the ① output of U1 is at a high level, the MOSFET tube is turned on, and the reversing camera is powered on.
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