Alex Torres wrote: > > From: Robert McAtee > > > > >I'm trying to use a PIC to control several amps (PWM). From what I read > in > > >catalogs, etc. MOSFETs are the way to go so I bought a 4A MOSFET > (IFR510) at > > >RadioShack. The ratings and specifications that came with the mosfet > says > > ---------- SNIP------------- > > I used the IFR510 to control a small RS motor from the basic stamp pin. > > Output was 5v and I put a 500K resistor in series with the gate. A > "micro" > > ampmeter did not show any gate current at all ???. I used a 6v lantern > > battery for motor power..... ==Mac== > > Why you need _SERIES_ resistor in MOSFET ??? You may shortly connect PIC's > output to gate. Nope, you can't. The maximum capacitance _directly_ connected to an output pin is something like 50pF (or was is 25pF - I can't remember). The inrush current into the MOSFET gate could cause a few nasties. A small series resistor keeps this down to an acceptable level. 5V/20mA = 250ohm minimum, so use a 270 Ohm. -- Friendly Regards Tjaart van der Walt mailto:tjaart@wasp.co.za |--------------------------------------------------| | WASP International | |R&D Engineer : GSM peripheral services development| |--------------------------------------------------| |SMS mailto: 0832123443@wasp.co.za (160 chars max)| | http://www.wasp.co.za/~tjaart/index.html | |Voice: +27-(0)11-622-8686 Fax: +27-(0)11-622-8973| | WGS-84 : 26¡10.52'S 28¡06.19'E | |--------------------------------------------------|