Temp and pH Controller

[cyberwollf]

Another idea to simplify design.  Ususaly you are only running a probe to monitor the tank OR a reactor. So if you know which case you will use exclusively we can set the onboard ADC to read it.

for Cal reactor are are running ~4 Ph.  That would be ~-0.18V output.  If you run that through an inverting buffer you get 0.18V and just set the ADC from 0-0.25V and you should get excellent resolution

for tank monitoring ~8 pH.  that would be ~0.10V.  If that was put through an NONinverting buffer and set the ADC for 0-0.15V you should get excellent resolution.

I would think it would be rare to measure both tank and reactor with a single probe. Is that assumption correct? That was our problem. We had to be able to scale the voltage to all positive without corrupting a very small signal.  At the very least this REALLY simplifies the dedicated Cal reactor controller.

[cyberwollf]

The above idea would allow 2 probes to run on independent ADCs with a single 0.25v reference voltage.

One port would be for the acidic probe while the other was for the basic probes. 

[jd]

If we can find a ADC that will handle all of our application without having to throw switches, I'd rather do that. This way, we can use one ADC and multiplex a large number of inputs while reusing the same conversion code, yeah know?

EDIT: two ADC's add cost....

[j80]

Bump, could i get a parts list and where to buy them for this? Thanks

[cyberwollf]

Like everything me an Josh did, this never got finished lol.  pH is a pita becuase you have to multply the probe output by -17 (if i remember correctly).  What are you trying to do?  honestly in the time since we played around with this project the new reefkeepers lites are SOO cheap now, its almost not worth it