Lpc2000

> 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.

Check your mosfet of choice for Rds and Vgs. Rds is the resistance of 
the FET when fully open (saturated) under specific conditions.
Vgs is the voltage you need to open the channel (this is a bit simple 
but will do to get an idea).

So a MOSFET with Vgs = 20V will not do for a 3.3V lpc21xx controller, 
you may want to go for a different part.

Nice parts are the IRF540 
(http://www.irf.com/product-info/datasheets/data/irf540.pdf), Vgs = 
2-4V, Rds = 0.077 ohm.
Id (continuous drain current) is 28 Amps (at Vgs = 10V, so it will be 
less when driven by the lpc21xx directly).

For smaller currents check out the IRF7403 (it's an SMD package ...) Vgs 
= 1V, Rds = 0.022 ohm, Id = 8.5A.
It's big enough for most of my applications and I tend to use this one 
instead of a standard NPN transistor when driving small loads (up to a 2 
amps).

I get these part from http://www.reichelt.de (German ...) and the 540 
costs 0.52, in SMD version 0.70 and the 7403 is 0.42 - all prices in Euro.

I prefer the SMD parts. Since I design, etch and drill my own PCBs for 
home projects I prefer SMD.
Creating SMD layouts and transfering this to photo sensitive PCB 
material is easy to do (I use HPs overhead film).
Drilling holes is not only time consuming but I also tend to break the 
(fairly expensive) drills from time to time ...

Regards,

    Rob

> Unfortunately those are connected to the same side of the
> coil and you can end up trying to drive a lot of current to no effect.

except from the nice smoke effects that is :-)