Re: [DIYbio] Electronic requirements for redesign of Arduino PCR thermal cycler

On Thu, Feb 26, 2015 at 11:33 PM, Andy Morgan <andrew.r.morgan@gmail.com> wrote:
> I came across this design
> (http://2013.igem.org/Team:Paris_Saclay/PS-PCR/detailed_description) that
> was build (and apparently for only 30 euros!) using peltier elements, but
> the electronic schematics look intense.

That looks like a pretty nice design. Here is what I believe is
happening: The LM339N are op-amps which are going to 'buffer' the
arduino GPIO pin signal, and they are 'buffering' relative to opposite
polarity/voltage (see the - terminal of the triangles is connected to
either 76% or 24% VCC) to /prevent/ what is called 'shoot through' on
the two left-side MOSFETs (Q2 and Q4)... which is a condition where
both of the left or both of the right-side transistors were turned on
at the same time, allowing the top 12V Vcc to shoot-through the
transistors and straight to ground... just wasting power (and possibly
over-heating the transistors or stressing the power supply).

This would be a fun project to build a schematic and
printed-circuit-board for. I will have time in a few weeks I think.
But essentially it's an arduino on the left-side of the schematic
page:
http://2013.igem.org/wiki/images/b/b5/Pspcr_schema.png

and the peltier control stuff is on the right-side.


You could probably also just use a couple easydrivers:
http://www.ebay.com/itm/EasyDriver-Shield-stepping-Stepper-Motor-Driver-V44-A3967-For-Arduino-/400522271040

--
-Nathan

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