Homemade short circuit alarm device

When inspecting the automobile circuit, we often encounter the fault of the positive power line short circuit and the fuse on the line being burned out. Sometimes, many factors such as many branches on the line and hidden lines make it difficult to troubleshoot the fault and waste time. Sometimes, many fuses have to be burned out to check the fault. For example, there are many branches on the S3 fuse line of Santana 2000GSi. The fuse is connected to the clock, radio, cigarette lighter, interior lights, luggage compartment and centralized control lock, etc., which will cause trouble if you are not careful.

In response to this situation, the author used a few simple electronic components to make a short-circuit alarm device, which can easily check this kind of fuse-related circuit fault, and these electronic components are basically derived from scrapped parts of automobiles.

The device consists of a 10 A resettable fuse, a 1 A/50 V rectifier bridge and an electronic buzzer of about 15 V (connection as shown in Figure 3). The 10 A resettable fuse and other components can be purchased on the market, or directly use the resettable fuse of the comfort system control unit of the abandoned Era Pride car. The fuse plug can be made by sawing off half of the 4-pin plug on the Santana lock. The purpose of connecting the rectifier bridge here is to ignore the current direction when the device is plugged into the car fuse socket.

The device is plugged into a socket on the line that is prone to burning fuses. When the line is short-circuited, the recoverable fuse can be tripped in 2 to 3 seconds, and only a very small part of the current flows through the fuse. Most of the current passes through the rectifier bridge and then forms a circuit through the buzzer. The buzzer sounds an alarm, so the fault range can be narrowed by plugging in and out of each branch of the line or electrical appliances until the fault is eliminated. When the short-circuit point stops ringing due to unplugging a plug or electrical appliance, 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.

Comments: During use, the recoverable fuse will be disconnected in 2 to 3 seconds due to the influence of short-circuit resistance, so the lead between the plug and the buzzer of the short-circuit alarm device will heat up, which is a normal phenomenon. In fact, as long as you can pay attention, you can make some targeted small devices for some typical faults. Although these small devices look simple, they can solve many problems, improve work efficiency, and make troubleshooting easier.