Timed resistor

[Diarmuid]

I am building a small 10V control panel, for a stage lighting system at my local school.

I have so far, got a working plan, of all of the desk apart from one bit, the fade timers.  I am looking for a chip, or poteniometer, so that, I can twist the potentiometer to full, then when a current is applied, it will take up to 180 seconds to fade to that. and when the potentiometer is at 0, it will have no effect, on the other master potentiometer.  (I'm not sure if that made sense, so I will try and clarify it a bit more.)
I've got one fader, which fades between all channels on and all off, I need a timer circuit above that, so that it fades, for  the time it has been set at and when it is set at 0, has no effect on the resistor.

Thanks for your help

[windoze killa]

Sounds like a pretty simple task. All you need is a 555 timer. There are plenty of circuits on the net that should do the job for you.

[Diarmuid]

From what I can find, 555 timers only seem to be able to output pulses, is this right, because I need a steady output as opposed to a pulsing one.

Thanks very much

[Enac]

How about a digital pot driven by a variable-frequency oscillator (555)? Maxim, or other mfrs, may have other parts that will work as well or better. Google (digital pot".

[windoze killa]

From what I can find, 555 timers only seem to be able to output pulses, is this right, because I need a steady output as opposed to a pulsing one.

Thanks very much

You can make a 555 do almost anything. But what you require is a pulse, one that can be varied from 0s to 180s. You can do this using a pot and capacitors or you could do it with fixed resistors and capacitors and use a switch to select fixed delays.