Active low transmitter question

[richard]

which in turn drives a loud sounder

why a relay at all ? the 2n7000 could drive that alarm directly with ease

[LEDave]

why a relay at all ? the 2n7000 could drive that alarm directly with ease

I never thought of that, great idea, cheers Richard.

What do you think the best way to drop the 12v from the sensor output to 3.3v into the pic, would the voltage divider be ok/work?

[richard]

works for me. you could protect against divider failure with a 3 to 5v zenner if you are paranoid
the first pic may be unnecessary too if the tx works like i think it does

[LEDave]

works for me.

Excellent, voltage divider it is then.

you could protect against divider failure with a 3 to 5v zenner if you are paranoid

Yes I do fit into that category (mildly at present), will look at at a backup with Zenner.

the first pic may be unnecessary too if the tx works like i think it does

I hear what your saying Richard, so I need to built the Tx cct on the bench now and test the Tx driven directly by voltage diver (no pic).

Thanks for your help, appreciated.

David