Well, if you're saying its a universal motor, you could use phase-control. But I'm confused on how would you do this with an emitter-follower. Or are you proposing rectifying the AC voltage first, and then using the emitter-follower to limit the drive current? I've seen this done with a thyristor. I guess we need to have the original poster specify what kind of AC motor was meant. But if he wants it by this weekend, it's probably too late :( -----Original Message----- From: jhancock [mailto:jhancock@CWV.NET] Sent: Friday, February 16, 2001 5:32 PM To: PICLIST@MITVMA.MIT.EDU Subject: [EE]: URGENT Power Control help needed I would agree if it is a true "ac" motor that the emitter follower will not work. If it is an ac/dc motor it may work. If it requires 240 vac to run, then getting that from a 5 or 12v source is doubtful within the time frame. Simpler to go to Sears (or equivalent) and purchase a battery driven handheld variable speed drill. The actual requirement was not specified so don't know if that would serve or not. In any case - good luck! Jess -----Original Message----- From: Eisermann, Phil [Ridg/CO] To: PICLIST@MITVMA.MIT.EDU Date: Friday, February 16, 2001 4:41 PM Subject: Re: [EE]: URGENT Power Control help needed >no, you can't control an AC motor with a single transistor that way. you'd >need several in a bridge configuration. There are actually special power >bricks made for this (e.g POWEREX). And don't forget, he's asking for a 240V >AC motor! There's factor of sqrt(2), not including any transients. At a bare >minimum, you'd need a 600V device for this. So i guess the 2N3055 is right >out... so is the IRF511 from radio shack (which is rated at 80V). > -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads