Re: [DIYbio] Re: Making my own incubator inexpensively

Hm, I wouldn't skimp on temperature control personally. It's the
critical "input" of the circuit, and LM35s can achieve 0.1C accuracy,
and are very easy to code for. Most other forms of temperature readout
that I've encountered are a bit batch-variable, and I wouldn't be
surprised if the same is true of something cool but hack-ey like your
onboard diode idea (which *is* an awesome hack, I'll grant you!).

For reproducible results, it's nice to offload variables and pay the
extra 50c for a decent IC package.

On 23/04/12 21:19, John Griessen wrote:
> On 04/23/2012 02:43 PM, Andreas Sturm wrote:
>> Well, 2 Outputs for the LED indication of temperature, one ADC (you
>> called it A2D).
>> I use LM335 because it's very very easy to use. Of course, I could
>> also use a PTC
>
> That is $1 each in ones qty, so maybe you could use the inherent
> temperature dependent volts in circuitry you already have. Often
> microcontrollers
> take a known steady small current diode junction in the chip and arrange to
> switch its voltage to the input of
> the measuring ADC, with which you can use
> a look up table of temperatures. A little more work in code and testing
> and
> a whole dollar off! No big loss in accuracy for the range you care about.
> Degrees C +/- 0.5 degree is easy. If there's not an internal convenient
> diode volts
> to measure, you can add a diode and resistor to +DC power supply as your
> temp sensor
> attached to a comparator/ADC input.
>
> John
>

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