The one I got was a moderately simple circuit based on a 555 timer using a TO220 RU7088R 6mฮฉ N-channel FET with a SBR40100 flyback diode " TO220 driving. Using a car radiator fan rated at 11.5A @ 13V, the device showed a temperature rise of about 14ยฐC on the PCB and 9ยฐC on the FET heatsink after about 20 minutes Operating at 90% duty cycle as measured with a thermal imaging camera Somewhat surprisingly, the cheap, no-name 7812 voltage regulator was one of the hottest components on the boardโฆ