How to use varying voltage to choose between four circuits

[Ronald2]

Hi,

I'm hoping to make a simple circuit in which varying output from a flex sensor (http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_150551_-1), turns on one of four discrete circuits.
i.e. from 0 to 1 volts from the sensor, closes only switch A (Circuit A)... from 1 to 2 volts closes only switch B (Circuit B), etc.

I've seen a circuit diagram for a "bargraph voltmeter" which uses an LM339 Quad to control 4 LED's... (http://ecelab.com/circuit-simple-led-voltmeter.htm) and was thinking of replacing the LED's with NPN transistors as switches for the external circuits... but as these external circuits are part of another (low current) device, I'm not sure how the transistors will affect those circuits. I'm also realizing circuit A will stay on as circuit B comes on...

Is there a better solution?

in thanks.

 

[jackorocko]

Only thing I got is to use a pic with analog input???

 

[Harald Kapp]

Ronald,
you cabn use an LM3914 (http://www.national.com/mpf/LM/LM3914.html#Overview) which can be programmed for dot mode (only 1 LED on).
If you need to isolate the external circuit from the LM3914, use small relays or photocouplers - whichever is bettter suted to your particular application.

Harald

 

[(*steve*)]

I've posted this elsewhere, but realize it may be more appropriate here.

Please don't. Contact a moderator and ask that the thread be moved.

 

[Ronald2]

*steve*
Sorry about that. Not just new to posting here, but in general. Will avoid double posting in the future.

Jackorocko
Thanks for the suggestion. I was actually looking to avoid microcontrollers...

Harald
Thanks as well. The LM3914 definitely looks like the ticket.
Could you suggest a small and efficient relay to order along with it?