Categories: let's build a lab

PCR machine

PCR is a method of selectively duplicating a specific part of DNA.
For this, we are going to need a PCR machine.

I choose to make my own, because I like making stuff and it’s way way more economical.
Firstly, I wanted to make myself a quick prototype on breaboards to try how it alll should work and if temperature changes I need to achieve with peltier elements are achievable.

Here are some photos from the build of a prototype:

This build was more intended to see if I can control reliably such temperatures with a microcontroller using Peltier modules in heating/cooling mode and just to experiment around to get a working cycler machine

The data suggest that yes, it works.

I have also got heating in the lid working in tandem together with main chamber temperatures.

The next phase is CNC-ing the heating element out of the aluminum block and re-do everything from scratch, more cleanly and neatly.

caveats & challenges:

  1. choosing the heating element: Peltier vs resistance heating
  2. balancing the ramp-down and ramp-up times
  3. balancing the PIDs (though I enjoy this part)
  4. balancing appropriate cooling system
  5. keeping thermocouple sensors calibrated over time

My solution was to use a Peltier fed by the highest possible frequency PWM (yes, I am aware of a shorter lifecycle), using an H-Bridge I can invert polarity on Peltier. Two temperature sensors are placed on the body of a chamber and the lid of a chamber. Temperature correction is then set with a PID loop.

So now it kinda works. Next part will be building it sturdy and compact with better chamber made on CNC, stronger heating elements and its custom software.

I also plan on releasing components lists, prices and code for arduino / controling software once its ready.