Solid state SPDT?

[EROMLIGNOD]

Hi guys:

What is the best way to get an SPDT effect using transistors/chips?

Here's my problem. I have over 200 little circuits to address. They are all
hooked to the same square wave output. I poll them one-at-a-time and switch
them from the square wave line to a common input line to my MPU and measure a
wave coming FROM them. Then I switch them back and go on to the next circuit.
Think of it like an SPDT switch with the common leg connected to the circuit,
one leg connected to the output bus and one leg connected to the input bus.

I realize there are ways to do this with discreet transistors, or single switch
circuits. Isn't there an economical way to do the 219 circuits with a
transistor array, or some type of off-the-shelf chip?

All replies are greatly appreciated.

Don

 

[EROMLIGNOD]

Well, I like the concept, but I'm not sure I'll have the space for 219 of them!
Isn't there anything smaller?

Don

 

[Dana Raymond, a minor God]

Do you have development control of the 200 circuits themselves?
If so, design them such that their outputs can be tristated (hiz) and a
control input and a control output on each along with a common clock. Wire
the circuits up bucket brigade style (like a serial shift register). You can
then clock in a serial bit stream to select which device you want driving
its output. A single d-type FF and a tristate buffer circuit per device can
do this.

There's a lot of ways to implement this including the control scheme.

Hope this helps.
Dana Raymond

"EROMLIGNOD" <eromlignod@aol.com> wrote in message
news:20030802104740.14491.00000905@mb-m04.aol.com...

Hi guys:

What is the best way to get an SPDT effect using transistors/chips?

Here's my problem. I have over 200 little circuits to address. They are
all
hooked to the same square wave output. I poll them one-at-a-time and
switch
them from the square wave line to a common input line to my MPU and
measure a
wave coming FROM them. Then I switch them back and go on to the next
circuit.
Think of it like an SPDT switch with the common leg connected to the
circuit,
one leg connected to the output bus and one leg connected to the input
bus.

I realize there are ways to do this with discreet transistors, or single
switch
circuits. Isn't there an economical way to do the 219 circuits with a
transistor array, or some type of off-the-shelf chip?

All replies are greatly appreciated.

Don

 

[MAG]

Don,
It would help to know about the voltages and currents you expect to see.
But here are some chips you can look at.
4066 & 4016- are Quad Bilateral switches [ 4 spst]
4051- is a Single 8-channel analog Multiplexer/Demultiplexer [like a 8 pole
rotary switch]
How do you want to pole each switch? Do you want to do it randomly or in
sequence with a count down/up circuit?

MAG

"EROMLIGNOD" <eromlignod@aol.com> wrote in message
news:20030802104740.14491.00000905@mb-m04.aol.com...

Hi guys:

What is the best way to get an SPDT effect using transistors/chips?

Here's my problem. I have over 200 little circuits to address. They are
all
hooked to the same square wave output. I poll them one-at-a-time and
switch
them from the square wave line to a common input line to my MPU and
measure a
wave coming FROM them. Then I switch them back and go on to the next
circuit.
Think of it like an SPDT switch with the common leg connected to the
circuit,
one leg connected to the output bus and one leg connected to the input
bus.

I realize there are ways to do this with discreet transistors, or single
switch
circuits. Isn't there an economical way to do the 219 circuits with a
transistor array, or some type of off-the-shelf chip?

All replies are greatly appreciated.

Don