pH and Temp controller - Final Approval

Hi,

I've attached a pic of the final schematic, If you could please check and see if i've got it right, i've broken it down into coloured block to help, the "connection" points will go to a display board where it will be displayed on 3 different Voltmeters.

The threshold op-amps have a hysteresis resisters for chatter free switching.

The outputs from the pH circuits go to a AND logic to act as a safe gaurd, ensuring the tank pH is above a set limit for the relay to opperate.

Component values not shown.

PLEASE advise if I have made any error with the schematic.

Thanks in advance!

In a tightly temperature-controlled environment (both the water and the controller circuitry), you might get away with the pH amplifier circuitry. I think you should read my comments in this thread, and tell us what you think.

Roff said:

In a tightly temperature-controlled environment (both the water and the controller circuitry), you might get away with the pH amplifier circuitry. I think you should read my comments in this thread, and tell us what you think.

Click to expand...

I'm not an expert in electronics, but take it your taking about the effect of the temp on the probe or circuit?

What difference on the ouput would say 1 Deg.C make? bearing in mind tank temp will stay within 1/2 a Deg C

None of the current "OEM" aquarium units have any temp compensation built in them.

Other than that, does it look ok?

sir
my house watered from a bore well.i wand to fill the water tank automatically.
i want simple circuit.from where i get the electronices components?
tks Mathew