If you cant find a low Rds P-channel FET, check out the high side FET drivers at micrel.com. They have built in charge pumps to switch an N-channel FET at the appropriate voltage for high side switching. I think headlight modulating on cycles is 3 or 4 times a second. Maybe you meant to say 240 times per minute rather than 240 Hz? ----- Original Message ----- From: "Miles McKinnon" To: Sent: Thursday, June 28, 2001 3:27 PM Subject: [EE]: Modulating a headlight > I am building a motorcycle headlight modulator using a PIC to monitor > ambient light and a few other things. Anyway, the PIC has to modulate the > headlight ( ~ 4Amps) at a arount 240Hz or so. > > There are a few legal stipulations. They say that you cannot switch the > ground, you must switch the +12V to the headlight. I want to use a low Rds > HEXFET or simular transistor, but I think I would need a P-Channel device. > > Is a P-Channel Mosfet difficult to drive from a TTL logic level, such as a > PIC. > > Thanks for any help. > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.