Timed Switched On Power

[dellsam34]

The author said I can replace the 2M resistor with a 2M pot and a 1K resistor in series to adjust the timer. Also the BC557 can be replaced with TIP127 or any similar transistor. What do you think?

[Ian.M]

Yes, a TIP127 for the output transistor looks possible.  Its a beefy enough PNP power Darlington to do the job.

Before even considering putting a pot in there you should get the timing 'in the ballpark' by choosing an appropriate timing capacitor and resistor experimentally.  Then choose a preset + resistor that gives you the adjustment range you need.   Apart from 2Meg pots being fairly uncommon nowadays, if you do put one in I expect you'll find most of its range covers time periods that aren't at all useful.