Second thermistor reading with Gen3

Hi all,
we have a first generation Mendel with Gen3 electronics (from Makerbot = Motherboard v1.2 and Extruder controller v2.2)
which we're upgrading with a improved extruder assembly and a heated build platform (HBP).

And it's with the HBP that we're having some difficulties,
we plan to control a relay with one of the unused MOSFET's on the Extruder controller to provide the power resistors from juice.



But the temperature reading of the build platform is a problem, the Extruder controller only has one thermistor terminal.



The hardware behind this aint rocket science, only a pull-up resitor fed with Vcc and a 10 uF capacitor parallel with the thermistor,
but it will also need an UNUSED ANALOG INPUT PIN on the Atmega168 chip.



Here we finally are at the question:

Is there an UNUSED ANALOG INPUT PIN on the Atmega168 which can be used for a second thermistor?


All replies or other suggestions will be appreciated!

Pins A6 and A7 have their own headers with gnd and vcc, right from the pot (with crystal down).
The labels on your board might be incorrect refer to picture or board file, or trace them instead.
[www.reprap.org]

For temp sensor: take two .100' headers, one with 3 (female) and other with 3 (but take/cut out off middle one so 2 remain), connect the gnd thick wire to hold them, mount the cap and resistor in between, you got a temps sensor that can sit right on top of a header like that.

Good luck.

Edited 1 time(s). Last edit at 10/12/2011 05:03PM by NoobMan.

See this picture.
If you hook it up to A6 then it works with the RepRap firmware and drives output A for the heated bed.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
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