Delay circuit

Hi, i need a delay circuit where if the logic input changes from a 0 to a 1 it delays this signal to the output from between 500ns to 1us - i need to be able to change this delay, i also need an equation of what values i need to get the desired delay. When the logic input changes from 1 to a 0 there must be no delay,

I dont want to use microcontrollers as these will be a waste and i want the operating voltage between 12 and 15v, 15v, please can someone help, thanks

What logic family are you using? A Vdd of 12-15V suggests the 4000 series family, which typically has a worst case propagation delay time (For gates @ 15V) of apx 90ns which is 18% of 500ns!

I do prefer to use the 4000 series but the only problem is that the turn off delay is long too, could anyone sugest another idea, thanks anyway