switching - creating continuity

[Kris]

I have an IC which watches for continuity between pins to be created
using an external mechanical switch.

I want to automate feeding information to the IC, and thus need to be
able to create direct pin connections using a microcontroller.

This is an obvious application for electromechanical relays, but they
are very slow and noisy. If I use a transistor or solid state relay, I
get voltage drop (0.3V?) across the junction. Will this still work?

Is there any other switching solution that creates true continuity
other than an EM relay?

The IC in question is a standard ps/2 keyboard controller - I'm really
just simulating keyboard presses using a microcontroller like a basic
stamp coupled with switching circuitry.

thanks

 

[CFoley1064]

Subject: switching - creating continuity
From: ">Kris
Date: 3/16/2004 11:50 AM Central Standard Time
Message-id: <ftee505s40v3r2fu6eo664p2bhbf5iu17l@4ax.com


I have an IC which watches for continuity between pins to be created
using an external mechanical switch.

I want to automate feeding information to the IC, and thus need to be
able to create direct pin connections using a microcontroller.

This is an obvious application for electromechanical relays, but they
are very slow and noisy. If I use a transistor or solid state relay, I
get voltage drop (0.3V?) across the junction. Will this still work?

Is there any other switching solution that creates true continuity
other than an EM relay?

The IC in question is a standard ps/2 keyboard controller - I'm really
just simulating keyboard presses using a microcontroller like a basic
stamp coupled with switching circuitry.

thanks

If you don't have that many keys to simulate, try a CD4066 -- it will show a
very high resistance when off (0.05 nA typ), and a very low resistance (250 ohm
typ) at 5V. This should have a small enough voltage drop to work O.K. Logic
"1" to turn it on -- piece of cake.

Good luck
Chris