Charlieplexing Relays?

[BigRez]

Hey Jon (and everyone else),

I read and understand the post on Charlieplexing 30 LEDs from 6 pins , and wondered if the same thing can be done to control relays.   (I suspect it can, but wanted to pose the question first.)

A prop I'm working on is two outputs short and I don't want to go up to a Prop-2 or add a DC-16 for just two outputs.  So, if I understand correctly, I can control six items from three pins, knowing that only one of those items can be used at a time. (I only need five items.)

This is what I have planned:
P7= sound tx
p6= sound rx
p5= trigger
p4= relay
p3= valve
----------------
Using p0, p1, p2:
(A) Relay AC   (X01)
(B) Relay AC   (X10)
(C) Relay DC  (1X0)
(D) Valve using high-current add-on (works like a relay, right?) (0X1)
(E) Valve using high-current add-on (works like a relay, right?) (01X)
(F) unused (10X)


If this is doable, how would I wire up the five items using pin0-2?  I assume diodes are used in place of LEDs? What should I be cautious of?  Is there a better way of doing this?

Thanks!

[JonnyMac]

No can do, buckaroo.   

Charlieplexing, like multiplexing, works with LEDs because the retina retains an mage briefly (this is called persistence of vision); so we can turn LEDs on and off very quickly but the eye thinks they're on constantly.  If you do this with inductive devices they may not work at all or will buzz or chatter horribly.

Your least expensive solution is the DC-16.  Of course, you could build up an expander board on your own, but the parts and time would be far more that the cost of the DC-16.