Magnetic stirrer

[pcremades]

We could use a commercial magnetic stirrer and hack the electronic controller.
Another option would be to use an MK2 heated bed (the one that 3D printers use) and design a magnetic stirrer. The benefit would be that this solution is cheaper and parts are more widely available.

[amchagas]

Cool, I would also suggest to have a chat with the team building an pcr machine. they are having to deal with temperature control too! @MaxZimmer maybe have a look here?

[pcremades]

@amchagas , couldn't find any discussion about temperature control in the repo...

[amchagas]

Maybe they didn't upload it yet, but the discussions have been taking place. you can also ping them on their slack channel.
On a related note, these might be interesting
https://hackaday.com/2018/04/14/pid-control-with-arduino/

http://brettbeauregard.com/blog/2011/04/improving-the-beginners-pid-introduction/

[pcremades]

Thanks André. I used the code from Brett to control an inverted pendulum, so I have experience with that one. Anyway, if we decide to go for a MK2 heated bed, then we can use the PID control in Marlin firmware. They already figured out the PID coefficients for that bed.

[pcremades]

I've been reading and apparently, the MK2 heated bed can reach 110°C in 30 min with a 24V power supply. Would this be enough to heat the reactor?

[vektorious]

Depends on the temperature you need to reach. I guess it will be impossible to heat it above 100 and it will take a lot longer than the 30 min to heat up the liquid just to 50 degrees. But this also depends on the volume of the reactor.

We used a water bath to heat our microbe reactor which is much faster and makes uniform heating easier. We also thought about wrapping the reactor with a heating pad.

[guadapinna]

The idea is to work in a water bath, calculation that reaches about 80 degrees would be fine.

[vektorious]

If you want to go to higher degrees (above 100), you can use glycerol (which is more expensive).

[pcremades]

Ok, now I think we are going in another direction. As we will be using a water bath, it would be easier to use an immersion electric heater and forget about the heated bed. It will be cheaper as well.