Tight Arse Stir Plate

[BjornJ]

brando, you've got it spot on - 10k pot with 1k3 fixed will work just as well, should give you 1.25V - 10.9V


Bjorn, you've got the wrong end of the stick, again. Computer fan speed controllers are not (or at least, bloody well shouldn't be) simple potentiometers. Every one I've ever seen has a small circuit board attached to the pot, which contains a small linear regulator or PWM circuit. The pot is just there for adjustment.

This is a pic of the computer fan speed controller I bought.
Looks like just a potentiometer to me, but I am pretty thick on the subject in question so thougth I should put it up here for review


[


thanks
Bjorn

edit: forgot to add the pic.

 

[leiothrix]

i havent read thru the 33 pages and if pwm circuit has be dicussed before please forgive me.
i have just finnnished putting this circuit together and it works very well,I havent tried it with a stir bar in a flask yet but will soon

View attachment 40566

the parts cost about $10 from jaycar, i used a IRFZ40N instead of the stated mosfet because of availablity.

cheers matho

that looks like the one i made. B)

I used a power darlington instead of a mosfet, also due to availability.

kicks the crap out of a linear power supply.

 

[Ade42]

you all seem to be useing a mechanical solution

has any one looked in to a solid state solution?

i carnt seem to find what i am looking for but this pic is close

now take the top disk off so you have a circular array of electro magnets

then wire them up to something like this in opposing pairs

http://www.high-voltage-lab.com/169/led-chaser



tap off the LED's to i think there called triacs? to take the load of trigger the magnets

replace R2 with a trim pot and maybe even add in a trim pot for the power going to the magnets

i was looking at about 8 magnets (4 sets of 2)

*DISCLAIMER* i have never managed to get/make any type of kit to work as i am hopeless with electronics it seems.
but am i heading down the right path for someone to design and construct something like this?

ahah, thats the "motor" used in my Pioneer Direct Drive Turntable, the motherboad that had the windings on had snapped, so i picked up the complete turntable for nothing, a few weeks micro soldering and is good as new!

 

[BjornJ]

All right, I got the thingy I ordered from ebay.
($10 delivered if anyone else wants one)

It looks like this:



I have a new 12V computer fan ripped out of an old computer, and my 12V power supply.

I understand I connect the 12V power supply on the left where it says "DC AC In" but does it matter where I put plus and minus or will this only impact which direction the fan spins?

On the right side I will connect the black and yellow cables for the fan, again does it matter which is which?

(the thing has no markings for plus/minus positive/negative wires)

Appreciate any help from the electronic wizards on here

thanks
Bjorn

 

[matho]

Bjorn,
On the input it doesn't matter because it goes thru what is called a bridge rectifier that will make sure the positive goes to the right place. On the output I'm not too sure but I don't think a reverse polarity will hurt the fan it just won't turn so try it and if the fan spins then it will be right but I could be wrong about the fan

Cheers matho

 

[BjornJ]

Awesome, thanks for your help Matho.

Bjorn

 

[BjornJ]

it doesn't work...

Connected the power supply and the fan to the little "voltage controller" and plugged the power supply in the wall.
The fan spins like crazy, the little LED is lit.
Turning the little screw say 10 turns left or right does nothing.
There is no stop either in or out, but screwing quite a bit both ways and no difference in fan speed that I can see.
how is this thing actually controlling/regulating the voltage?

 

[matho]

Bummer

Mate Briton lesands isn't to far from where I work (south Sydney) I could make you a pwm controller like the one I just made for about $15 it will be on proto board but it will work let me know if you would like one and I'll make it for you

Cheers steve

 

[BjornJ]

Matho, I've been needing this thing for a year!

:lol:

And when I log back in to say it WORKS when I swapped the fan for a 0.56A model from the 0.4A one I used first, it suddenly started working.
Maybe the output from the thingy is too high in A for the smaller fan so even when it is set to low it will be too high.

Back on track:
If you can build a "thingy" that I can connect a computer fan to in one end and a 12 V power supply in the other and a way to control the fan speed from outside of the project box (or tell me what size potentiometer to put on it), I will please take two.
I am sure you could sell a hundred of them on here..

Will PM you my details in case you are willing to build some.


thanks
Bjorn

 

[matho]

Mate I i don't need to make anymore money so a production line is out of the question
But I'll put two together for you, the one I put together took me just under an hour. I'll get the parts sometime this week and start on it soon. I'm thinking maybe a donation to ahb as payment. Speak to you soon
Cheers steve

 

[BjornJ]

woohoo, can't wait

thanks!

Bjorn

 

[LethalCorpse]

Maybe the output from the thingy is too high in A for the smaller fan so even when it is set to low it will be too high.

Not possible - the current rating of a supply in A is simply the maximum current it is able to provide. A load will (for a given supply voltage (V)) draw as much current as it requires. If the load tries to draw too much current, the supply will begin to have problems - fail to regulate the voltage, overheat, catch fire, etc. In short, the current rating on a supply can't be too big, it can only be too small.

And stop saying "power thingy". It gives me the screaming heebie jeebies



@Matho: Love your work, mate.

 

[BjornJ]

thanks for clearing that up, always interesting in learning more.

I have read a little about the LM317 3 terminal adjustable regulator tonight, more out of curiosuity than anything else

I have now made it make a whirlpool in my 1 litre erlenmeyer flask by adjusting the height between the magnets and the stir bar with stacking DVD covers on each side, real high-tech!
But it seems really flakey, and doubt it would be able to do a good job of a heavy yeast slurry.
One of my server hard drive supermagnets seems to work better than two of those small super magnets I bought at jaycar glued to a bigger disk to spread them out.

Hoping matho's power thin...eh PWM will work better .

thanks
Bjorn

 

[matho]

i havent read thru the 33 pages and if pwm circuit has be dicussed before please forgive me.
i have just finnnished putting this circuit together and it works very well,I havent tried it with a stir bar in a flask yet but will soon

View attachment 40566

the parts cost about $10 from jaycar, i used a IRFZ40N instead of the stated mosfet because of availablity.

cheers matho

putting two together last night i realised that i used a IRF540N instead of the IRFZ40N that i quoted above just thought i would correct myself.

thanks leathal but i can't claim the circuit as my own stole it off the net

cheers steve

 

[aussiechucka]

Here is a pic of my Stir plate. Thanks for all the info on how to build one. :super:
HAve already used it a couple of times.
Thanks
Chucka

 

[Ade42]

Mate I i don't need to make anymore money so a production line is out of the question
But I'll put two together for you, the one I put together took me just under an hour. I'll get the parts sometime this week and start on it soon. I'm thinking maybe a donation to ahb as payment. Speak to you soon
Cheers steve

Gday mate, Just wondering if you could take some pic's of your PWN proto board, both sides please!
I'm going to make up a couple and could do with the help, if its no trouble of course!


Is the circuit that you have posted before 100%? (don't wanna buy the wrong bits, or ask you to make me one! but if you are cool with a donation ahb i'd be up for that as well!)


Cheers
Ade

 

[matho]

hey ade
yes this circuit does work with the parts that are shown, as i said i used an IRF540n mosfet instead of the IRFZ46n just because jaycar doesnt stock it. I have just about finnished the one's for bjornj so i can take a few pics tomorrow for you.
about making one for you i dont really want to get into the hassle of posting and stuff like that, as luck would have it bjornj works just around the corner from me so its convenient for me sorry mate

cheers steve

 

[matho]

here is some pics as i promised hope this helps out




is a link of a video i took of the controller in action its not the best but i took it from stopped up to full speed and back down again it can go down to just over 1 revolution a second.

cheers steve

 

[BjornJ]

Does that mean I soon will have a working stir plate!!?

woohoo :lol:


Happy.Very.

Bjorn

 

[Ade42]

here is some pics as i promised hope this helps out
View attachment 40930

View attachment 40931

is a link of a video i took of the controller in action its not the best but i took it from stopped up to full speed and back down again it can go down to just over 1 revolution a second.

cheers steve

Thanks, I'll help!. Just got all the bits from Jaycar, They don't have any IN5818's so i opted for the IN5819 Ive looked at the spec sheets and i hope it works. ok if i blow some 555's. I just found a box of dozens!