Electric window blinds

[boatsman1]

I have electric window blinds (220 VAC 50Hz). I want to be able to raise and lower them to variable heights using a time clock. If I just use the time clock the blind will either completely rise until it it switched off by a limit switch when it reaches the top. The same thing with the other direction. I have found that it takes 25 seconds to completely raise or completely lower the blind. I need some circuit that will raise the blind, for example, threequarters the way up (or threequarters the way down) when the time clock switches on. I'd like to be able to adjust the time so I can alter the amount the blind goes up or down. All the circuits I've seen using a 555 timer need a single pulse to trigger the 555, but the time clock switches on for a minimum of 15 minutes. Can anyone advise me or suggest a suitable circuit?

 

[alec_t]

You can still use a 555-based circuit, but create a brief trigger pulse for the 555 from the time clock output. Is that output at mains voltage? Or is it a volts-free switch?

 

[boatsman1]

You can still use a 555-based circuit, but create a brief trigger pulse for the 555 from the time clock output. Is that output at mains voltage? Or is it a volts-free switch?

Thanks Alec. The time clock is 220VAC but the switching contacts can be 220 volts or even DC as there is no built in connection between the motor supply and the switching contacts. So how do I get a pulse?

 

[alec_t]

Here's a suggestion. Motor run should be adjustable in the range ~ 2s - 38s with the components shown.

 

[boatsman]

Thank you alec.
I was unable to view the file you sent as windows 7 doesn't recognize the asc ending. I did however print out the circuit diagram and hope to try it out on a breadboard.

 

[alec_t]

The .asc file is for simulation in LTspice. I'm not surprised Windows 7 doesn't recognise it. If you want to see its content (rather than run a simulation) just change the extension to .txt.