Pulse Width Controler circuit needed if anyone can help please?

Hi,

What i'm trying to build is a controller that once triggered will vary the pulse width to a solenoid from 20% to 100% (so in effect open a little to fully open), over a variable peroid of time, say 1-10 seconds.
A high power transistor like a TIP122 will be needed to run the solenoid, but that is about all I know! lol

Can anyone help me with this?

Many thanks!

Karl.

Do you just want to do it "open loop", or do you want to do it "closed loop", where some parameter like flow or pressure is being controlled?

Open loop is fine, it will be controlling a Nitrous Oxide solenoid so once triggered instead of it coming in with a bang fully open, it comes in progressively over a user selecable period (1-10sec).
Forgot to say the NOS solenoid will have a constant 12v+ so it needs to be the earth pulse width that is controlled.

Thanks!
Karl.

Open loop is fine, it will be controlling a Nitrous Oxide solenoid so once triggered instead of coming in with a bang fully open, it comes in progressively over a variable period of time (1-10sec).
Forgot to say the solenoid will have a constant 12v+ so it's the earth that needs to be pulse width controlled.

Thanks!
Karl.

Open loop is fine, it will be controlling a Nitrous Oxide solenoid so once triggered it just needs to complete it's task and then stay at 100% until the trigger signal stops, and can then be re-triggered again.
Forgot to say that it is the earth that needs to be PW controlled and the solenoid will have a constant 12v+ to it.

Thanks,
Karl.