How to Keep iPhone Lock Screen ON (keep it from Dimming / Blanking / Going to Sleep)?

I'm having a jailbroken iPhone 4S, running iOS5. What I would like it to do is to keep the "lock screen" (the one with the clock and the slider, not the homescreen) ON for ever, if connected to a cable. I have a neat stand for my iPhone next to my computer, and would like to use the iPhone as a clock (but without having to start a specific app, it should happen automatically).

How can I get this to work?

Thank you for any help!

Btw. I did some web research, of course, but could not find a solution. (1) I tried "nolock" (on Cydia) does not work on iOS5, (2) "lock screen dim delay" only delays by 30 min, (3) disabling auto-lock in setting prevents the lock screen from coming up, it does not keep the lock screen on

You can't.