Lpc2000

Hi Tom,

  We use a IRFD110 (Hex Dip MOSFET) with a 1N4001 diode to control 0.5
amps in a very small package. They are also logic compatiable.

regards,
Charles

--- In lpc2000@yahoogroups.com, Tom Walsh <tom@o...> wrote:
>
> Robert Adsett wrote:
> 
> >At 02:45 PM 11/2/05 -0500, Tom Walsh wrote:
> >  
> >
> >>Rob Jansen wrote:
> >>
> >>    
> >>
> >>>>For that kind of drive I'd go for a MOSFET myself.  They are
resistance
> >>>>devices.  You might be able to drive them from the I/O pin.  If
you use a
> >>>>logic level FET and drive them at 5V you certainly will be able to.
> >>>>
> >>>>
> >>>>        
> >>>>
> >>>And do not forget to add a diode accross the FET, some MOSFETs have a
> >>>diode built in but it may be too small, depending on your load.
> >>>Solenoids and things like motors have huge coils - keep this in mind
> >>>when designing.
> >>>
> >>>
> >>>      
> >>>
> >>I generally use a 2N7000 or 2N7002 FET for driving relays.  They can
> >>sink up to 100ma easily and have an internal clamping diode to protect
> >>the gate when the coil (de)energizes.
> >>    
> >>
> >
> >
> >Well the original post did say they had a 2 Ohm coil.  That in turn
would 
> >suggest a multiamp drive was needed.  That diode in the 2n7000 won't 
> >protect against inductive spikes though, it's in the wrong part of the 
> >circuit.  You are probably getting avalanche breakdown and I don't
think 
> >I've seen a data sheet for either of these parts with an avalanche
rating.
> >
> >  
> >
> OW, missed that one!  Well, bigger FET and larger diode(s) then...  
> Perhaps an IRF530, lots of power in that, somewhere around 6 AMPs, 
> IIRC.  It could also be switched from 5volt logic.
> 
> Trouble with transistors is that they are current devices, they magnify 
> current based on the beta (gain) of the device.  You don't suffer that 
> problem with an FET as it controls current with a voltage on the GATE 
> (low current draw on the control voltage).  Definately would go with a 
> MOSFET or BI-FET.
> 
> TomW
> 
> 
> -- 
> Tom Walsh - WN3L - Embedded Systems Consultant
> http://openhardware.net, http://cyberiansoftware.com
> "Windows? No thanks, I have work to do..."
> ----------------------------------------------------
>