I bought a couple of these last year and found that older versions didn't have reverse polarity protection. The latest version appears to be protected. However, the safety MOSFET is tiny, and if you daisy chain multiple boards or run many servos at higher current, a lot of current can flow through it and burn it out. Despite these limitations, these boards work as advertised. I've powered them with both 5V and 3.3V logic from Arduinos and ESP8266.
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