How to build a stir plate for less than ten quid

[JapanBrew]

Did you try reversing the polarity? Internally the pot might have been made wrong.

 

[Spapro]

Did you try reversing the polarity? Internally the pot might have been made wrong.

I think the polarity is correct, using the multimeter on the output connectors of the PWM, with red probe on + and black probe on - the multimeter reports 11.98v, if I swap the probes the other way round then I get - 11.98v (ie minus).

So think polarity is correct.

Really stumped !

 

[JapanBrew]

Well, that's all I had. You won't hurt the fan to just flip the wires.

 

[sven945]

Finally put mine all together in a box, and here it is! I've got the controller blutacked to the bottom because I didn't have any shorter machine screws to fix it down. Maybe something for another day. I'm going to stick some rubber tape on the top so my flask is more stable when it's switched on. It'd be nice if you could calibrate the controller so you had more control than just the top 90% of the dial, but all is good for less than a tenner! Thanks for posting the instructions.

 

[BeerCat]

Finally put mine all together in a box, and here it is! I've got the controller blutacked to the bottom because I didn't have any shorter machine screws to fix it down. Maybe something for another day. I'm going to stick some rubber tape on the top so my flask is more stable when it's switched on. It'd be nice if you could calibrate the controller so you had more control than just the top 90% of the dial, but all is good for less than a tenner! Thanks for posting the instructions.

Neat job. What size fan did you use? I bought a 120mm but its very slow and wobbles all over the place. Should of bought a better quality one.

 

[sven945]

I used the one linked on the first page, so it's 92mm. Fits perfectly in the box I used. When I tried it out the stir bar kept flying out of reach of the magnets, but I put another couple of magents on top so it should be fine. The fan is fixed at the top of the machine screws.

 

[Spapro]

Totally stumped now

Measured with multimeter, input into pwm is 12.02v and output to fan is 11.98v with dial turned right up. Dial turned right down output to fan is 1.5v.

So pwm appears to be working correctly I think. Connected fan to power and it spins but wired back through pwm and it gives a little nudge around 70% but won't spin!

Connections look good, polarity and solder on back of pwm looks fine.

Any ideas chaps?

Bought a new fan and everything is now working - still stumped as to why the original fan would work direct to power but not through PWM ???

This fan I bought from a UK seller, arrived in 2 days and is 3 wire (don't connect the yellow wire to anything, just use the red + and black - wires), 90mm 3pin selected: http://www.ebay.co.uk/itm/12v-SATA-...hash=item4867741bb5:m:mft5OtN-HX3j5kYt0gQES3g

Anyway, all sorted, will post pic later

 

[Spapro]

Heres a quick pic of mine now its all working - I only made the stir plate, we bought the slow cooker from Argos :lol:

 

[strange-steve]

Heres a quick pic of mine now its all working - I only made the stir plate, we bought the slow cooker from Argos :lol:

Looks great, good job. The stir plate looks good too
Glad you got it working :thumb:

 

[Spapro]

Cheers Steve :lol:

 

[sven945]

Where do we all keep our stir bars when we're not using them? My memories of A level physics are hazy so I can't remember if I should keep it attached to the magnets, or away from magnetic influence.

 

[IainM]

Where do we all keep our stir bars when we're not using them? My memories of A level physics are hazy so I can't remember if I should keep it attached to the magnets, or away from magnetic influence.

Store the stir bar away from the magnets.

 

[sven945]

Cheers!i'll find somewhere else to keep it.

 

[strange-steve]

Where do we all keep our stir bars when we're not using them? My memories of A level physics are hazy so I can't remember if I should keep it attached to the magnets, or away from magnetic influence.

Beyond my pay grade that, but I'm sure Iain is correct as usual :thumb:

 

[BeerCat]

Just picked up a 5l flask for £6. Lets hope they honor the deal.

 

[strange-steve]

Just picked up a 5l flask for �£6. Lets hope they honor the deal.

Where did you find that?

 

[Gerryjo]

Just picked up a 5l flask for �£6. Lets hope they honor the deal.

Sounds like a cracking deal.

 

[BeerCat]

Of Ebay. I bought the last one or i would of posted the link straight away.

 

[strange-steve]

Surely it's not borosilicate at that price??

 

[BeerCat]

Surely it's not borosilicate at that price??

I think it was a mistake as now out of stock and priced at £49. Marked as sent though so expecting it in the next few days.
"Conical Flask Erlenmeyer Borosilicate, 5000 ml, 5 litre, glass joint 50/42"