How to read analog 0-1v signal

jbalat

Is it possible, if so..
Is this on along a similar line to the RC time stuff ?

Tapperman

Use an A/D chip (like TLC-548) with AA bat as a reference voltage, might be quickest?

hover1

What kind of resolution are you looking for? Do you want to meaure .5 , .25, .1 volt increments, or more accurate measurements? Or is it just ON/OFF at 0/1 volt?

A little more information is needed to give you the proper solution.

Jim

Post Edited (hover1) : 2/1/2010 12:31:06 AM GMT

Mike Green

Don't forget that the Propeller can do ADC with just a couple of resistors and capacitors. Read the application note on the cog counters (AN001 - www.parallax.com/tabid/832/Default.aspx)

jbalat

I need 0.05v accuracy

I just thought instead of using a pot I just use the 1v source with a lower resistor if any at all as per the standard rctime circuit with the capacitor ?

PUB Pot | potTime, M

' Configure counter module.
ctra[noparse][[/noparse]30..26] := %01000 ' Set mode to "POS detector"
ctra[noparse][[/noparse]5..0] := POT_PIN ' Set APIN to P0
frqa := 1 ' Increment phsa by 1 for each clock tick

repeat
' Charge RC circuit.
dira[noparse][[/noparse]POT_PIN] := outa[noparse][[/noparse]POT_PIN] := 1 ' Set pin0 to output-high
waitcnt(clkfreq/100_000 + cnt) ' Wait for circuit to charge

' Start RC decay measurement. It's automatic after this...
phsa~ ' Clear the phsa register
dira[noparse][[/noparse]POT_PIN]~ ' Pin to input stops charging circuit
waitcnt(clkfreq / 5 + cnt) ' Wait for Decay 1/5 second

' Get Time difference
potTime := (phsa - 624) #> 0
M := (potTime / 360) ' use a factor to get right voltage

waitcnt(clkfreq / 20 + cnt) ' Wait 1/20 second -> 10 Hz

kwinn

.05V resolution from a 0-1.0V signal is less than 8 bits so you could easily use 2 pins for an ADC as Mike suggested.