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Author: Subject: Keep the temperature
Mixe
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[*] posted on 21-12-2022 at 13:10
Keep the temperature


Ok, so noob question time.
I have a heating mantle with stirrer which sort of works great, able to reach temps well over 350 and great for distillations where most of the vapours keep a constant temperature by the boiling point.
Unfortunately it has no automatic temperature control, and the heating knob is not graded at all, so when I actually need to keep a refluxing reaction mixture at a constant temp it’s a damn guessing game.
Anyone have any good tricks to get this sorted? I’m running a reaction that needs to keep 60C constantly for six hours, and I just over- or undershoot all the time, desperately correcting the knob.
What should I do to find the temp setting for this bugger? I know I know I should get a heating plate with temp settings, but I honestly don’t have the money right now. Any tips?
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violet sin
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[*] posted on 21-12-2022 at 16:51


PID temperature control for your device would be a cheap fix. In my experience, Most come with a thermocouple probe, an SSR and some lies about being a le to drive that thing directly. But it's been a few years since I've had to chase my tail on this subject. I'm speaking of the REX100C PID controller that was about 13$.

https://www.ebay.com/itm/165653821639

There's a simple way to extend the measurement range with menu button pressing. Opens more possibility than 0-400°F.

You can bypass the internal Relay to hijack 12v to activate the included SSR easily.

This hobby will teach you a lot about all kinds of equipment, how to overcome obstacles and press on.
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Mixe
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[*] posted on 21-12-2022 at 17:25


This was more or less what I had in mind, but I thought I would have to construct it from an arduino. Great tip, thank you! question is how I connect this to a heating mantle of this type (which is what I have):


Screenshot 2022-12-22 at 02.24.47.png - 1.2MB
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BromicAcid
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[*] posted on 21-12-2022 at 19:57


Put some marks on it when you figure out boiling points. You'll get to know your dial with practice and you'll use those marks even if you never boil the same things again as a guide. Practice is really what is going to fix your issue. I've used PIDs before but they're not very useful for distillation and even in reflux you need someone to figure out the reflux temperature (i.e., even if you're in a solvent of a known boiling point it can be altered by the constituents). There's a lot of finesse to chemistry that I thought early on were easy things to plan for but ended up being more skill than textbook.



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Sulaiman
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[*] posted on 21-12-2022 at 21:14


For fractional distillations I like to use a 'dimmer' (phase angle) type controller
(settable constant power) for stability.

To maintain a constant temperature I use pid controllers (REX-C100 and others)

Your mantle has stirring so you'd need to keep that as-is and bring out separate wires from the heating element to your controller.
Wiires inside the mantle should have high temperature insulation, ie NOT normal pvc insulation.




CAUTION : Hobby Chemist, not Professional or even Amateur
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Johnny Cappone
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[*] posted on 22-12-2022 at 02:36


Quote: Originally posted by Mixe  
question is how I connect this to a heating mantle of this type (which is what I have):


A PID controller would be a good choice, although it's a bit of a bulky device. Like @Sulaiman, I have successfully used "dimmer" type controllers to control heat output from electrical resistances. They are also useful for controlling the rotation of tools that use universal electric motors. A dimmer module is usually slightly cheaper than a PID controller and can also be used to get a "more-or-less-constant" temperature once the adjustment where the heat produced by the heating element and the lost heat is found.

I believe that these (PID and dimmer controllers) are the cheapest alternatives to solve the problem. Some research on YouTube can shed more light on the differences between them. Once you've made your decision, just buy one of them and, if necessary, ask for help on the installation. It's a really pretty basic procedure.

IMG_20221222_073436_717.jpg - 92kB IMG_20221222_073440_484.jpg - 115kB




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Mixe
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[*] posted on 22-12-2022 at 02:52


Thank you all for excellent feedback and ideas.
I can do without YouTube, I’m an old time electronics hobbyist and programmer and it shouldn’t be a problem to hook this up, also to my newly designed ArduinoCode- based pH/ temp measure/control panel with touchscreen. I’ll be posting info and schematics to this shortly, now with PID included.

Regards

M
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