Simple homemade short circuit alarm device

When inspecting automobile circuits, we often encounter faults such as a short circuit in the positive line of the power supply and a blown fuse on the circuit. Sometimes, many factors such as many branches on the line and concealed lines make troubleshooting difficult and waste time. Sometimes it is necessary to burn out many fuses in order to check for faults. For example, there are many branches on the S3 fuse line of Santana 2000GSi. The fuse is connected behind the clock, radio, cigarette lighter, interior lights, luggage compartment and centralized lock, etc. If you are not careful, it will cause trouble.
In response to this situation, the author made a short-circuit alarm device using a few simple electronic components, which can easily check the fuse-related circuit failure, and these electronic components are basically derived from scrapped parts of the car.
The device consists of a 10 A recoverable fuse and a 1 A/50 V rectifier bridge (the rectifier bridge is a rectifier tube sealed in a shell. It is divided into full bridge and half bridge. The full bridge is the connected bridge The four diodes of the rectifier circuit are sealed together. The half bridge is to seal together the two halves of the bridge rectifier. Two half bridges can be used to form a bridge rectifier circuit, and one half bridge can also be used to form a transformer with a center tap. The full-wave rectifier circuit, the rectifier bridge should be selected considering the rectifier circuit and operating voltage) and an electronic buzzer of about 15 V (the connection is shown in Figure 3), 10 A resettable fuse and other components are available on the market. You can buy it, or you can directly use the recoverable fuse of the comfort system control unit of the discarded era pride car. The fuse plug can be modified by sawing off half of the 4-pin plug on the Santana latch. The purpose of connecting the rectifier bridge here is that when the device is plugged into the car's fuse socket, the direction of the current flow can be ignored.
Plug the device into a socket on the line where the fuse is easy to burn. When the line is short-circuited, the recoverable fuse can trip in 2 to 3 seconds. Only a very small part of the current flows through the fuse, and most of the current passes through the rectifier bridge. A loop is formed through the buzzer, which sounds an alarm. In this way, the scope of the fault can be reduced by unplugging and plugging in various branch plugs of the line or electrical appliances until the fault is eliminated. When the short circuit point is caused by unplugging a certain plug or the buzzer of an electrical appliance stops sounding, it means that the fault is here or behind the plug. After long-term practice, the author found that this device is a very practical and effective device.
Comment: During use, because the recoverable fuse is affected by the short-circuit resistance and will disconnect in 2~3 seconds, the lead between the plug of the short-circuit alarm device and the buzzer will heat up, which is a normal phenomenon.