MOSFET as a Switch For Solenoids

[Fubari33t]

First, I am a n00b at this power stuff, so my terms might be way off, and the use of components might be way off. I want to build a analog control box for my A340e Toyota slush box. My computer controls it right now, but switching from ECU control to Analog "Paddle Shifters" is a goal I'm set out to achieve. There are two solenoids inside this trans that control shifting, 12V of course. I want to build a relatively small unit for this, along with other outputs via same type of switching components. I'm looking at MOSFET's to do this. but am lost on the whole Gate(switch that I press?) Source(the solenoid?) and Drain(ground?) From what I read, they can handle the 12V and 3A no problem, and given proper heat-sink hold for long periods of time? Such as hours if need be? There are many other components inside the box I am trying to design, such as RPM sensors to stop Over-Reving, Speed sensor to stop me from throwing it into reverse by double tapping the down paddle. As well as Torque converter lockup for highway cruising. and various other switchable things. Basically, the ECU will send it's signals through the box, UN-interupted for regular use, then a flip of a toggle, will stop ECU signals, and will allow me to go up and down through the gears via the two solenoids by pressing either the up, or down paddles. Should I use a mechanical relay, or try the MOSFET? While one solenoid is active(1-2 shift) the 2nd will be activated while the first remains on(3-4)

 

[rocky79]

Try this for a mosfet. For more info search google for "driving a solenoid with a mosfet"
A 100 ohms instead of a 1k and 10k instead of 100k should be enough.