Voltage Adder circuit?

[ArnieW]

Dear picaxers,

I would like to use sensors (acting as switches) to get info on levels in a vessel. I have a working circuit where the liquid closes the sensor contacts and turns a picaxe digital input on.

What I am wondering is: is there a simple way to duplicate this (say 10 switches) and combine them into a single (rather than 10) analog input? Is there some kind of simple voltage adder circuit so that the first switch closing caused 0.1 V on the input, the closing of two caused 0.2 V etc.

Any help would be appreciated.

Arnie

PS. Condolences to Microzed Bob's family

 

[ANJ]

Gday Arnie
One option is to make a simple voltage divider of say
5V-10K-1k-1k-1k-1k-1k-...-gnd
Take a tapping from the 10k to 1k junction to the PIC analogue input
Then parallel each 1k resistor with one of the switches.
As the level goes up, the switches close sequentially and essentially remove the paralleled resistor from circuit, thus giving stepped voltages at the tapping point.
A bit crude, but you only require 1 analogue input. Resistors can be selected to give you the output trigger shape you want
Andrew

 

[ArnieW]

Hi Andrew,

thanks, I think that has potential. Simple is good, and I was trying to think of some kind of resistive divider that would do it, so I am grateful for your help. The resolution on an analog input is much higher than tolerance or steps I'm after with such a system, so it should function quite well.
regards, Arnie

 

[ANJ]

Gday Arnie
"I think that has potential"
Nice pun
Actually it has changing potential, which is why it works
Andrew