Got my first order of boards for this project today, and got one built. Works quite well:
I hope that video has uploaded OK. The red release timing was set to minimum for the video but it can be adjusted up to more than 30 seconds with the trimmer pot. The yellow delay is set to 10 seconds but that can be changed also.
Seems to work very well. This is an early version and lacks provision for an LM78xx voltage reg. But the version uploaded earlier above has the reg provision.
Rod