aahhh, I get it now... so a driver, I'm taking a bit of a stab in the dark here as I've never worked with transistors or MOSFETs before so combining the two in one circuit should be fun.The problem is that a standard bjt 555's output doesn't go all the way to Vcc; it's about Vcc-1.7v. That might cause a P-ch MOSFET to be conducting in linear mode (ie: high resistance) which you don't want. That's why a driver is necessary.
my understanding of transistors is that they amplify the voltage applied to the base, so if 555 Vout is roughly Vcc-1.7v then it will be (roughly) 12.3v, the transistor will try to amplify that as much as it can but the highest it will be able to go is Vcc. so when there is 12.3v applied to transistor base, emitter = Vcc = MOSFET source
output from 555 -> transistor base
transistor Emitter -> MOSFET Gate
MOSFET Drain -> LED VCC
Transistor collector and MOSFET Source both connected to V+
am i close or way off the mark?
Ok so it doesn't really make much difference from 100-200 when it comes to heat that is produced...That's the basic idea. It doesn't have to be terribly precise. Targeting 200Hz would give you a pretty large degree of leeway for faster or slower.
so going from my previous calculations a mosfet that can handle 8-10A should be exactly what I need for both circuits...Hardly any at all, if a decently sized MOSFET (or pair of them) is selected.
First, you'll need to total up how much current all of the LEDs will draw if they were all ON and at maximum brightness. Then, you look for a MOSFET that is capable of a continuous drain current (Id) of twice or more that amount of current.
I'm a hand's on person so will understand fully how a MOSFET works when I can get some to play with... my plan is to drop into the local shop after christmas but before the new year and get some to play with...