Input expansion or multiple break beam inputs with prop 1?

[electricbob]

Hello.. I'm considering a project requiring multiple break beam sensors (at least 4) on a prop-1. Will break beam or PIR sensors work on the lower pins (p5 and lower) without the utilization of pull-down or pull-ups? AND is there a way to create more inputs on the prop-1 with some sort of expansion unit for inputs?

By the way, I'm kinda new at this and I learn more by example... so...  Is there a source out there for prop-1 examples that show specifics and, more importantly, specific device hookups and configurations? Many Thanks. Bob

[JonnyMac]

The ULN acts as a pull-down so you can use the [Parallax] PIR that we carry on any pin.  I helped one of our friends with a project that monitored several PIRs and then sent control messages to a DC-16 to control outputs.

You can use a chip like the 74HC165 to expand inputs -- but you'll have to build it up on a board (like our proto board).  With the '165 and a little bit of code you can turn three IO pins into eight digital inputs.