Photocell circuit

[john kitz]

I have an Allen Bradley process controller I have wired as a burglar alarm
on all the windows and doors throughout the house. My next step is to wire
in motion detectors outside. I have several X-10 wireless motion detectors
that work well detecting, but I need to find a circuit that will look at the
flashing LED or tap into the LED circuit and give me a contact closure for
the AB.
Can anyone help.
Thanks.
John

 

[Fred Bloggs]

I have an Allen Bradley process controller I have wired as a burglar alarm
on all the windows and doors throughout the house. My next step is to wire
in motion detectors outside. I have several X-10 wireless motion detectors
that work well detecting, but I need to find a circuit that will look at the
flashing LED or tap into the LED circuit and give me a contact closure for
the AB.
Can anyone help.
Thanks.
John

It is best to use a *retriggerable* logic monostable in the LED circuit
to drive a reed relay to the AB. See the 74HCT123, set the timeout for
greater than the interpulse time to the LED- it can trigger off positive
or negative going edges- and work from 2-6V.