Electronic Fuse

This circuit is an electronic version of fuse. The electronic fuse cuts off the current (like the ordinary fuse does) and lights up the LED when a certain current level is exceeded. The advantage of this fuse in comparison to a conventional one is that it can be reset and re-used. The electronic fuse can handle a 500mA maximum of current but it can be increased beyond 500mA by changing the value of R1 with the aid of this formula: R1 = 0.4(I), where I = desired maximum current.

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Overvoltage Crowbar Circuit

A simple circuit but very effective to protect a main circuit which is sensitive to overvoltages. The circuit uses a zener diode in parallel to the power line of the protected circuit or device. Once the output of the power supply increases due to a malfunction, the excess voltage will be routed to ground by the zener diode. If the voltage will increase further, the total current consumption will exceed the capacity of the fuse. The fuse will blow at this moment and the current supply is broken.

The schematic diagram can be download here!

MP4 Regulated Power Supply for my Car

Recently, I acquired a Sony MP4 player which was Made in Japan according to the label. But, I doubted that it is not Made in Japan for obvious reasons. Anyway, the purpose of buying this gadget is to be used in my car stereo as a source of crisp digital music from MP3 and MP4 media format. During my travel to provinces, my gadget was powered from a lithium-ion battery that lasted more than two hours only in which I need to recharge the battery again, once it will be drained. So, I decided to develop a very simple regulated power supply that can sustain the long journey of travel without thinking and worrying of no power supply for the gadget.

The schematic diagram can be downloaded here!.