DIY high power USB car charger

For some time I felt the need of an USB charger in my car, but all the commercial ones I’ve seen haven’t convinced me they are reliable. So I proposed myself to build one which would have to be “virtually indestructible”, stable and safe for the devices I connect to it.

I remembered that I had a LM340KC-5.0 (5V positive regulator in TO-3 case), laying around somewhere, and told myself that this is perfect for the job. After I looked over the datasheet, I did a test circuit, and it performed perfectly.

I bought a telephone outlet to use it as a case, and I mounted two USB receptacles (which I dismembered from an old computer motherboard) instead of the telephone jack, and the LM340 on top of the case.

The USB pins configuration you can find on Wikipedia.

I have also added a green LED to know if is working.

Have fun.

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