PWM motor control

For my question refer to the PWM circuit shown at

http://www.geocities.com/tjacodesign/motor/motor.html

I want to ramp current up at the 12V DC motor over a 2-3s time.
What components need t/b ADDED & OMITTED from this circuit to get
this "softstart"??

Thank you
K/ Thompson

Interesting circuit,
but to get to where you want to go, I would throw away this design and start from scratch. Although, you could keep everything to the right of the transistor 'Gate' and throw away the control circuit.

Doug

You don't care about "softstop"?

This is similar to another post I replied too. I assume you are going to control this with a plc? If so you could use an analog output instead of the potentiometer and use a timer to increment as wanted...ie if going from 0 to 12 in 3 seconds that would be 4 volts per sec which would mean 1 volt every .25 seconds which can be taken down to .4 volts every .01 seconds. I think my math is correct, I have the flu or something so not sure..looks ok.

This is just an example, the actual starting voltage and ramp specifications would be up to you...ie you may need to start at 6 volts and go to 12.

For that matter if the motor is small, current draw less than analog output ratings, then you may not need a controller at all.

There are a number of options, you could use multiple outputs with resistors to change the speed over time.

They make actuators, electric and pneumatic devices that can turn the pot.

I agree with Doug, may be better off going from scratch. Maybe use a digital potentiometer with a 555 ...the options are endless.