PIR tripped Chipcorder - MK174

I would like to trip the electronic Record/Playback mini kit (MK174) using a PIR detector (Quasar kit 3030) via a relay (Smart electronics kit 1168). All modules work correctly separately. I have managed to combine them all with the caveat of operating each board off a separate power supply - if I run the PIR and relay off the same supply (8*1.5V - AA batteries) the relay is automatically tripped once power is supplied to both boards. My question therefore is how can I isolate the power supply to each board and what is the best means of supplying kit mk174 with the required 4.5V from the 12V supply - should I use a regulator or can I use resistors?

Thanks in advance and apologies if this is not a good place to post.

Schematic diagram: http://tinypic.com/r/259xu84/5

The problem is the ‘led activated switch’, it will always turn on the relay if connect as shown in your diagram.
Leave the ‘- IN’ pin of the led activated switch as-is
Connect the ‘+ IN’ pin of the led acitved switch to the pin marked ‘OUT’ of the IC of the PIR detector.

As for the power supply, if you have 8 cells in series, it is easy to get 4.5V for the MK174 if you take its power between the - of the first and the + of the third battery.