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A few quick questions. (Connectors and Power Supplies)


Conrad, Robert

Jan 1, 1970
First question: Is there a place that makes inexpensive cables/connectors
that would:
- allow me to run 10-12 pairs between a control box and a relay panel.
- Handle about 200ma per pair.
- Be small enough that I could put roughly 25 of these connectors on the
back of the control box. The control box is 3in high and 8in wide.

If that isn't possible: Is there a cheap ($3-4US) way of building a reliable
5V power supply that could be included in the relay box (pretty small).

Conrad, Robert

Jan 1, 1970
Okay, I know its bad form to reply to your own post but I just read some
cool stuff that could make my life MUCH easier and negate the need for my
previous comment.

I was looking up SPI and IO expanders. I found the MAX7301 which has a SPI
interface. Is it possible/safe to send that SPI output to each relay box. In
the relay box I could put a MAX7301 IO expander that actually controls the

I still need a cheap power supply in this case, or I need to power the
device through the connector cable. This doesn't sound safe to me so I am
trying to avoid this solution.

I also need to know something else. Can I use a multiplexed to access the
Chip Enable bit on the MAX chips, and tie all the other SPI pins (Data in,
Data out, and Clock) together on all the components? Would I have problems
with this configuration?