Going back to post #1 you said "pin 3 of the 555 gives -5 volts when 12 volts is reached".
When you say -5 volt from the 555 how are you measuring it, with respect to ground?

I just measured pin 3 and +5V from the 7805 or pin 8 from NE555

 

Measure pin 3 from ground which is pin1

 

Going back to post #1 you said "pin 3 of the 555 gives -5 volts when 12 volts is reached".
When you say -5 volt from the 555 how are you measuring it, with respect to ground?
I think you mean the output of the 555 is 0 volts when the battery is 12 volts.

ill go to the shed and measure things

 

Going back to post #1 you said "pin 3 of the 555 gives -5 volts when 12 volts is reached".
When you say -5 volt from the 555 how are you measuring it, with respect to ground?
I think you mean the output of the 555 is 0 volts when the battery is 12 volts.

Tested with MM Black and red leads
when the 555 senses >=12Volts
black lead to Pin 3 Red to Pin 8=+5V
Black lead to Pin3 Red to Pin 1 = 0V

 

You always measure voltages with the black lead at ground. Anyway that tells me that the output from the 555 is 0 volts when it senses 12 volts.
Try this arrangement connecting the 12 volt relay to pin #7. It's also recommended to connect pin #4 to 5 volts as well.

 

You always measure voltages with the black lead at ground. Anyway that tells me that the output from the 555 is 0 volts when it senses 12 volts.
Try this arrangement connecting the 12 volt relay to pin #7. It's also recommended to connect pin #4 to 5 volts as well.
View attachment 312862

Thanks very much Sghioto yes it runs the relay from pin7.. but I hadn't hooked pin to +5 which I will do
As expected the coil draws 48mA which the 555 can handle.. but just for interest I would like a transistor to run the relay (for learning purposes) do I hook +5V from pin 4 to the base through a 1k resistor and pin 7 to the emitter and collector to +12V?

 

No! In this case since the output is low one would normally use a PNP transistor like a 2N3906. Emitter to 12 volts, Collector to top side of relay, other side of relay to ground. Connect the base through a 1K resistor to pin 7.
Other choice one could use two NPN transistors like the 2N2222 wired as an inverter.
I'll post a schematic shortly.

 

Two ways using transistors.

 

View attachment 312872
Two ways using transistors.

thank you very much again learning a lot
I have some BC557 in stock it has Ic of 100mA which I thought would be Ok? attached sheet

 

BC557 should work OK.

 

BC557 should work OK.

thank you very much again