Bad design?

[Rob]

Is this a bad design:

I have 5 connections (switches on a X10 mini home controller) that either
need to get shorted with pin A or pin B.

I am planning on using two CD4066 bilateral switches
(http://www.fairchildsemi.com/ds/CD/CD4066BC.pdf).

Each of the 5 inputs would have TWO connections connected to it, one from
pin A and one from pin B (outputs of two of the 'spare' switches). As long
as I am careful not to have both switch A and switch B enabled at the same
time is this a bad design?

I know that I could use an inverter to protect against having both A and B
active at the same time, but I am going to use a PIC to control the
switching. In an effort to keep parts to a minimum I can do this with
careful coding.

Thanks

 

[petrus bitbyter]

Is this a bad design:

I have 5 connections (switches on a X10 mini home controller) that either
need to get shorted with pin A or pin B.

I am planning on using two CD4066 bilateral switches
(http://www.fairchildsemi.com/ds/CD/CD4066BC.pdf).

Each of the 5 inputs would have TWO connections connected to it, one from
pin A and one from pin B (outputs of two of the 'spare' switches). As long
as I am careful not to have both switch A and switch B enabled at the same
time is this a bad design?

I know that I could use an inverter to protect against having both A and B
active at the same time, but I am going to use a PIC to control the
switching. In an effort to keep parts to a minimum I can do this with
careful coding.

Thanks

Not necessarily. It's common practice (bustranceivers for instance) to tie
outputs together and make sure the hardware always keeps at least all but
one in tristate. So if you have it in your own hand, it will do. It's still
the hardware - controlled by your program but nevertheless - that enables at
most of the switches.

petrus bitbyter

 

[Jack B. Pollack]

Is this a bad design:

Not necessarily. It's common practice (bustranceivers for instance) to tie
outputs together and make sure the hardware always keeps at least all but
one in tristate. So if you have it in your own hand, it will do. It's still
the hardware - controlled by your program but nevertheless - that enables at
most of the switches.

petrus bitbyter

Thanks

 

[ehsjr]

Is this a bad design:

I have 5 connections (switches on a X10 mini home controller) that either
need to get shorted with pin A or pin B.

I am planning on using two CD4066 bilateral switches
(http://www.fairchildsemi.com/ds/CD/CD4066BC.pdf).

Each of the 5 inputs would have TWO connections connected to it, one from
pin A and one from pin B (outputs of two of the 'spare' switches). As long
as I am careful not to have both switch A and switch B enabled at the same
time is this a bad design?

I know that I could use an inverter to protect against having both A and B
active at the same time, but I am going to use a PIC to control the
switching. In an effort to keep parts to a minimum I can do this with
careful coding.

Thanks

We really need more information. But setting that aside,
you can often protect the condition where A backfeeds into B
when both are enabled, by using diodes. Example:
/
A---o o--->|----+---[InputPin]
|
/ |
B---o o--->|----+

Actually, if you want to know if the design is good or bad,
you need to post the whole circuit. For example, you
mention "shorted", but the 4066 will have an on resistance,
not a short. Impossible to tell with certainty from what you
have posted if the 4066 will work for you.

Ed