Jinc8
Harmless
Posts: 14
Registered: 23-3-2022
Member Is Offline
|
|
Made myself a magnetic stirrer
I'd been thinking about this for a while, but I finally decided to make myself a magnetic stirrer, since I could find nothing in my country for less
than 200€ (plus making stuff is always fun)
So, I ordered a few stir bars earlier this week, got a 12v computer fan for 4€, plus a few magnets I'd had for a while and this is the result:
I'm planning on 3d printing an enclosure for the "ugly" part, but there are a bunch of higher priority prints going on right now and I'll probably get
to that next week. The current "setup":
(Basically just use anything taller than the fan+magnets and a ceramic/plastic plate on top)
I might consider adding a ceramic heating plate/heating mantle (interchangeably) on top, since I'm using ferrite magnets and temperature isn't as much
of a threat to them.
I also haven't yet figured out how to conveniently set it's power as I thought it could be controlled with an Arduino, but turns out my fan doesn't
have a pwm pin :/ . Unsurprisingly, it seems to be a little too strong for my little 200ml flasks but who cares, a vortex is a vortex.
I know it's not that much of a masterpiece but I figured I could post it here and update every now and then with changes I've made.
|
|
|
Rainwater
National Hazard
Posts: 919
Registered: 22-12-2021
Member Is Offline
Mood: indisposition to activity
|
|
If i may make a few suggestion.
Go all out. But be cheap.
Est cost, $40usd
3d print a spin plate and load it with magnets. As many as your motor can spin
You can have a digital rpm readout.
https://create.arduino.cc/projecthub/ambhatt/dc-motor-speed-...
You can have a digital speed controller.
https://playground.arduino.cc/Code/PIDLibrary/
And with a simple observation function. You can incorporate "stir bar decoupling" detection and have the device auto correct the issue. As well as
slowly increase the spin rate until the desired speed is achived.
You can also heat any sample up to temperature in just a few seconds by adding this cheap do dad
http://dontcrushmydreamsbro.example.com
One of these is a lie.
"You can't do that" - challenge accepted
|
|
|
j_sum1
Administrator
Posts: 6320
Registered: 4-10-2014
Location: At home
Member Is Offline
Mood: Most of the ducks are in a row
|
|
I have a couple of computer fan stirrers that I have made. I have not needed to use them for a while, but they have been useful in the past. The big
attraction was that they cost me essentially nothing since I had the fans and power supplies on hand.
|
|
|
ManyInterests
National Hazard
Posts: 930
Registered: 19-5-2019
Member Is Offline
|
|
Nice! I've seen videos of those on youtube. I think I should try to make one, since I do need a flat surface since my mantle is curved and putting
things in an ice bath and stirring is near impossible.
|
|
|
draculic acid69
International Hazard
Posts: 1371
Registered: 2-8-2018
Member Is Offline
|
|
I use one of these to control the speed and use a phone charger 3.7-5v as a power source. There excellent and can run all day.
[Edited on 14-4-2022 by draculic acid69]
|
|
|
Jinc8
Harmless
Posts: 14
Registered: 23-3-2022
Member Is Offline
|
|
I actually managed to control it with a simple 1k ohm potentiometer (not that broad of a control range but it works), which is apparently not really
safe but its just 12 volts so whats the worst that could happen....?
The design for the enclosure is also done, quite a good design imo but it'll be a total of 26hours and I've recently been having issues with long
prints.
Yeah id definitely like to give it Relay-PID controls, but I dont think its worth the effort yet as I get just what i want from my current circuit
Thanks for your replies!
p.s. I just happened to have been experimenting with iron salts recently, and have a fecl2 solution which i could oxidise to etch pcbs, which also
seems fun (though my current design doesnt really need one).
[Edited on 14-4-2022 by Jinc8]
|
|
|
Sulaiman
International Hazard
Posts: 3692
Registered: 8-2-2015
Location: 3rd rock from the sun
Member Is Offline
|
|
Quote: Originally posted by Jinc8  | control it with a simple 1k ohm potentiometer
Yeah id definitely like to give it Relay-PID controls, but I dont think its worth the effort yet |
Using a resistor will give poor torque at low speeds and generally poor speed control.
Relay control would give poor speed control,
Pid is unneccessary
The pwm type shown above is a good option,
I over-specify stuff like this,
eg for a 1A motor use a 5A, 10A or more controller, very little extra cost for peace of mind.
CAUTION : Hobby Chemist, not Professional or even Amateur
|
|
|
draculic acid69
International Hazard
Posts: 1371
Registered: 2-8-2018
Member Is Offline
|
|
| Quote: Originally posted by Jinc8 | I actually managed to control it with a simple 1k ohm potentiometer (not that broad of a control range but it works), which is apparently not really
safe but its just 12 volts so whats the worst that could happen....?
[Edited on 14-4-2022 by Jinc8] |
I tried that and it worked for a minute then started to smoke.
That was with only 5volts.
|
|
|
Rainwater
National Hazard
Posts: 919
Registered: 22-12-2021
Member Is Offline
Mood: indisposition to activity
|
|
lazy amazon item that i use alot.
I cant comment on this seller but there are 100s of clones just like it
how the above circuit works
It's the current rating of the device. A pot with a high current rating is expensive.
You can easily configure a 555 timer to operate as a crude pwm controler to drive a transistor for very cheap.
"You can't do that" - challenge accepted
|
|
|
Jinc8
Harmless
Posts: 14
Registered: 23-3-2022
Member Is Offline
|
|
Really? I've left mine going for over two hours (under supervision of course) and nothing happened. The potentiometer does get a little warm, but
that's not really a problem when it's been running for hours.
[Edited on 16-4-2022 by Jinc8]
|
|
|
Jinc8
Harmless
Posts: 14
Registered: 23-3-2022
Member Is Offline
|
|
Anyway, here's an update on the project:
I printed the enclosure and did some soldering this morning.
This is the final (for now) result:
My next project will probably be an attempt at making H2SO4 from Citric acid and ferrous sulfate (not really sure if it'll work yet, but I think
ferrous citrate is insoluble, I'll have to do a little bit more research). Can't wait to use my stirrer and not have to keep mixing things by hand!
|
|
|
Sulaiman
International Hazard
Posts: 3692
Registered: 8-2-2015
Location: 3rd rock from the sun
Member Is Offline
|
|
Nice!
Please keep us updated... nice to see successful projects.
If your power supply is 5V or less then that may require a different controller,
I am not up to date but there must be plenty of choices due to microcontrollers.
But, if the 1k pot works for your needs then good enough. Very nice.
How resilient are printed objects to "lab" chemicals?
Maybe a ceramic tile (eg kitchen/bathroom wall/floor) on top?
[Edited on 16-4-2022 by Sulaiman]
CAUTION : Hobby Chemist, not Professional or even Amateur
|
|
|
Jinc8
Harmless
Posts: 14
Registered: 23-3-2022
Member Is Offline
|
|
This one was printed with PETG, which apparently really isn't resistant to a lot of chemicals (e.g. concentrated acids, bases, aldehydes, aromatic
hydrocarbons)... I forgot to check that before I printed it... but still I don't really have any 'chemical resistant' plastics to print with (the most
common plastic used for 3d printing is PLA, polylactic acid which gets depolymerized by strong bases). I really only picked PETG because it can
withstand a bit higher heat (ill still need additional insulation if I add a hotplate above it, though...)
So, yeah, I most likely will use some kind of cover on top of the plastic when i use it.
|
|
|
Rainwater
National Hazard
Posts: 919
Registered: 22-12-2021
Member Is Offline
Mood: indisposition to activity
|
|
You can use aluminum foil as a replaceable cover, but i recommended a good spray paint for a lasting protective coat. Very thin coats, or it will melt
your print.
Chemical compatibility tables are easy to obtain. You will be disappointed by most 3d filaments
Attachment: eriks - petg chemical resistance.pdf (105kB)
This file has been downloaded 256 times
"You can't do that" - challenge accepted
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
