Theres a load of waffle in this post - what it really boils down to is "what's a good way for a BOB signal to switch 12v DC, 500mA power"?

I've got one of those 250mW LASER modules. I've soldered up the constant-current supply circuit, fed it some electric from a 12v wall-wart transformer, and got a nice shiny red line coming out the front of the LASER. Lovely.

But what I'd like to do is to be able to turn it on and off really quickly, so I can draw dots and lines etc.
I'm pretty quick at flicking a power switch on a 13A mains socket, but not *that* quick. :heehee:

I use an SSR to control my proxxon mini-drill from the computer (EMC2), which works very nicely. But when I use the same method to control the LASER, the beam takes a while to switch off. About half a second. It's the capacitor in the wall wart doing its best to smooth the power.

So I've then tried using a FET. But I'm no electronic whizz. I can read a circuit diagram, but I'm lost when it comes anything remotely tricky.
It's a little 2.7A power MOSFET. I've used them before to control a 1A LED from a microprocessor, so I thought this would be a doddle.
The Gate is connected to the logic pin from the BOB.
The Sink is connected to ground, and the 12v LASER circuit connects between Drain and 12v.

But the LASER stays on constantly.

So here's the questions (at last!)

1) Does the FET sound like a good plan? In the way I described?

2) What do other people use to switch this kind of thing?


Cheers!

Keith.

p.s. To save anyone worrying about my eyesight, with the 250mW LASER bouncing about everywhere... I've actually been cunning, and while testing I'm just using a a dozen LEDs across the constant-current power circuit, rather than the LASER diode.