Homebrew PCBs

On Fri, 07 Apr 2006 at 21:13:44 -0500 badgers wrote:
>...I am interested in building a PCB for a circuit that I did not design.
>It is a 7106 A/D with LCD driver to be used as a thermostat with a diode
>and a 9 volt LM7809 volt regulator.
>
>The circuit is based on Fig 18 on Page 13 of the following PDF>
>http://www.cpdee.ufmg.br/~aguirre/datasheets/FN3082.PDF

As the yokel said to the lost tourist;
"Ee zur, iffen I wanted to go there I wouldn't start from here."

The 7106 is a nice, self-contained (if rather old) basis for an LCD
digital meter but rather unpromising ground for a thermostat.

It doesn't have a means for monitoring a set point:
no way of entering a set point value, no way of storing it,
no way of comparing it to the measured value or outputting
an over/under signal, and, just to make life really difficult,
the temperature output is not just seven-segment encoded
but also XORed with the backplane voltage and oscillating
between V+ and an internal digital ground voltage.

You will have fun designing the logic for a temperature
controller around that.

OTOH, there are DPM ICs which include set points...


Regards, LenW
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