Something else bothers me a bit. I have just read through the spec of the motor and I don't think this motor can handle more than 220V DC. Our mains supply is 220V Ac. Putting that through a bridge rectifier and a cap will probably push it to 320 V DC!! which is miles to much. What can I do to get this down to around 200V DC again? -----Original Message----- From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of John Dammeyer Sent: 13 April 2002 11:29 PM To: PICLIST@MITVMA.MIT.EDU Subject: Re: [EE]:High power DC switching.. Use a transistor circuit. A while ago I posted a link to my Casting Furnce controller http://www.pacificsun.ca/~john/pdf-files/Furnace.pdf There's your control for driving the FET. John > -----Original Message----- > From: pic microcontroller discussion list > [mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Kevin Howell > Sent: Saturday, April 13, 2002 2:14 PM > To: PICLIST@MITVMA.MIT.EDU > Subject: Re: [EE]:High power DC switching.. > > > Thanks I found the datasheet on the IRF740, I didn't know > that there are > inherent problems when driving a MOSFET (Cgs) . Now the > search is on for a > mosfet driver. Can't the IRF740 b interfaced directly to a > PIC? Surely it > was designed with a microcontroller in mind? > > Thanks > Kevin > > -----Original Message----- > From: pic microcontroller discussion list > [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of PY2NI > Sent: 13 April 2002 10:22 PM > To: PICLIST@MITVMA.MIT.EDU > Subject: Re: [EE]:High power DC switching.. > > > As a starting device try 2 or more IRF 740 (400V @ 10A > each) you have > better options if you don't put more than 200V on the FET you > can use only 2 > IRF 640 (200V @ 18A each). MOSFets are really friendly > devices when you pay > attention on how to handle then, especial care with driver > circuits, some of > then have quite a large input capacitive reatance. Cgs. > There are especial > ICs (GATE DRIVERS) designed to deal with this problem if you > don't want to > waste your time doing this. > Hope it helps a bit. > > P.S. the devices mentioned aren't expensive, I often buy then > for a buck or > less. > > [ ] s > Horta > > > ----- Original Message ----- > From: Kevin Howell > To: > Sent: Saturday, April 13, 2002 3:26 PM > Subject: Re: [EE]:High power DC switching.. > > > > I can't find any Mosfets that can handle 200-300V. The > problem is not to > > source them but to find a suitable part. (Keep in mind the 20A) > > > > Thanks > > Kevin > > > > > > -----Original Message----- > > From: pic microcontroller discussion list > > [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Bob Blick > > Sent: 13 April 2002 06:44 PM > > To: PICLIST@MITVMA.MIT.EDU > > Subject: Re: [EE]:High power DC switching.. > > > > > > > I have some high power fast switching transistors, BUV48, > which I want > to > > > use to control a 220V DC motor using PWM. The transistor > can handle 10A > Ic > > > and 400 Vce (hfe =8!!). My problem is that the motor > draws up to 20A and > > > thus I will > > > need more than one of these transistors in possibly a darlington > > > configuration. Please can someone help me with a circuit > to control this > > > current hungry motor using a pic ... > > > > Hi Kevin, > > > > Do you really have to use this transistor? Do you already have some > > other transistors to use as drivers for them? If not, perhaps you > > should consider some other transistors, I would suggest MOSFETs. > > Your losses will generally be lower. Also if you do PWM you will > > need a freewheel diode across the motor. > > > > Others will likely also have suggestions. A transistor with hfe of 8 > > doesn't sound like a whole lot of fun. > > > > Cheers, > > > > Bob > > > > -- > > http://www.piclist.com hint: The list server can filter out > subtopics > > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > > -- > > http://www.piclist.com hint: The list server can filter out > subtopics > > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > > > > > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > > -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics