Post by thread:Re: ADC Recommendation

Technical Geniuses, I'm considering a first project! I'm wanting to sample a CdS cell(s) using a 16C84, but I'm not quite sure as to what A/D converter I would use. I'm at Maxim's site, and they offer samples...hehe, could anyone recommend a particular A/D Converter? Thank you guys again for your vast ammount of knowledge! Tim H.

Tim Hamel wrote: > > Technical Geniuses, > > I'm considering a first project! I'm wanting to sample a CdS cell(s) using a > 16C84, but I'm not quite sure as to what A/D converter I would use. I'm at > Maxim's site, and they offer samples...hehe, could anyone recommend a > particular A/D Converter? > Thank you guys again for your vast ammount of knowledge! > > Tim H. I know there are at least a few gal Tech Geniuses in the audience... :-) -- ___________________________ | Darrel Johansen | | tempe, arizona | | spam_OUTdarreljTakeThisOuTprimenet.com | |_________________________|

> > Technical Geniuses, > > I'm considering a first project! I'm wanting to sample a CdS cell(s) using a > 16C84, but I'm not quite sure as to what A/D converter I would use. I'm at > Maxim's site, and they offer samples...hehe, could anyone recommend a > particular A/D Converter? > Thank you guys again for your vast ammount of knowledge! Well unless you need something really high speed you don't need an A/D converter to do the job. Here's two really quick ways of doing it. 1) I'm using this one for my outside light controller. Put the CDS in a simple 555 timer circuit set for one shot mode with a PIC line for the trigger and another for the output of the 555. The PIC code triggers the 555 and measures how long the output remains high. 2) Another way to do it is to roll your own version of the Parallax BasicStamp POT command which measures variable resistance. The basic idea is to charge a capacitor to full charge, then to measure the amount of time it takes to gradually discharge the same cap through a variable resistance. The trick that I missed when trying this method is for the PIC to actively discharge the cap by switching the sensing line between output low and input causing the cap to discharge bit by bit. I haven't implemented this method yet but the next time I need to measure a varaible resistance, I plan to try it. Hope these ideas help. The 555 is simple, cheap, and can be done with $3 of Radio Shack parts. BAJ > > Tim H. >

A simple to interface is the MAX187ACPA (8 pin plastic DIP), it is 12 bits ADC with internal Reference Voltage. Pretty cool 3 wire interface SCLK, DATA, /CS, +5Volts, cost around $18 at digikey... :) Wagner. Tim Hamel wrote: {Quote hidden}> > Technical Geniuses, > > I'm considering a first project! I'm wanting to sample a CdS cell(s) using a > 16C84, but I'm not quite sure as to what A/D converter I would use. I'm at > Maxim's site, and they offer samples...hehe, could anyone recommend a > particular A/D Converter? > Thank you guys again for your vast ammount of knowledge! > > Tim H.

Byron A Jeff wrote: > 1) I'm using this one for my outside light controller. Put the CDS in > a simple 555 timer circuit set for one shot mode with a PIC line for > the trigger and another for the output of the 555. The PIC code > triggers the 555 and measures how long the output remains high. <Maxwell Smart> Ahhh! The old PC Joystick interface trick eh? </Maxwell Smart> -- Cheers, Paul B.