Tight Arse Stir Plate

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MattC

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updated diagram to make it a bit neater and include the new values.
Jaycar parts:
LM317T - ZV1615
5k linear pot - RP3508 or RP7508
knob to suit - pick one. Not the ones which say "spline" or suit 9mm pot
680ohm resistor - RR0568
switch - pick one. Any will do, so long as it's a latching type, not momentary. Pushbuttons, toggle switches, rockers, etc.
10u cap - RE6070
100n cap - RC5360
Would a similar circuit work with a 1K linear pot? if so what other components would I have to swap on the diagram?

Heading to Jaycar this WE want to ensure I have correct parts

Cheers
 

leiothrix

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It wont really work with a 1k pot.

I'm not sure of the exact circuit you're using, but I'm assuming it's like the one in the attached image.

The formula for Vout is:
Vout = 1.25 * ( 1 + R2/R1 )

Where R1 is 680ohm (according to your parts list) and R2 is the pot.

With a 1k pot you get 1.25->3.1V
With a 5k pot you get 1.25->10.4V

So with the 1k pot you probably won't have enough power to get the fan spinning. In general, if you 1/2 the voltage the current will drop by 1/2 as well, leaving you with 1/4 the power (i.e. inverse square relationship).

I'd still recommend a PWM power supply though. Reducing the voltage really kills the performance of the fan. It's a slightly more complicated, but not by much.

I'm pretty sure that makes sense, but I've been 'sampling' some rather nice bourbon :icon_chickcheers:

Rob.

lm713t.png
 

MattC

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Circuit is from LC's post a while back, The fan wont spin unless the pot is up high, then you have to turn it down. The max speed of the fan is lower than when connected to the fan straight from the 12 V power source. I guess this is the reason why?

Will grab a 5K pot and wire it up as in diagram.

I did have a fan controller but its a 4 terminal one and too large for what I need.

Cheers

circuit.png
 

LethalCorpse

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It wont really work with a 1k pot.

I'm not sure of the exact circuit you're using, but I'm assuming it's like the one in the attached image.

The formula for Vout is:
Vout = 1.25 * ( 1 + R2/R1 )

Where R1 is 680ohm (according to your parts list) and R2 is the pot.

With a 1k pot you get 1.25->3.1V
With a 5k pot you get 1.25->10.4V

So with the 1k pot you probably won't have enough power to get the fan spinning. In general, if you 1/2 the voltage the current will drop by 1/2 as well, leaving you with 1/4 the power (i.e. inverse square relationship).

I'd still recommend a PWM power supply though. Reducing the voltage really kills the performance of the fan. It's a slightly more complicated, but not by much.

I'm pretty sure that makes sense, but I've been 'sampling' some rather nice bourbon :icon_chickcheers:

Rob.
This.
 

Franko

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where would one add a LED to this circuit as a power on display

Franko

circuit.png
 

leiothrix

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Assuming that the 12V input is reasonably stable, between the + & - just after the switch would be fine.

If you do it after the regulator then the light will dim as the fan slows down. And it will probably turn off about half way across the range too.

You also want to put a resistor in series with the LED to stop it blowing up too. A value of around 500ohms will be fine. It depends on the source voltage and the power rating of the LED though. A 560ohm resistor at 12V will give you 18mA across the LED. They usually have a current rating of either 20 or 30 mA, so it's best to err on the low side first.

Rob.
 

Wolfy

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My Tight Arse Stir Plate Version 1.0 went well until over-flowing yeast shorted out the power supply to create some interesting fireworks in the loungeroom in the middle of the night.

So now I have the high-tech-spill-proof Stir plate Version 2.0:


Very simple and easy to make:
12V speed controlled super-bright-blue-LED computer fan
12V power supply (from and old cable-Internet modem)
4x small round rare-earth magnets
Plastic computer HDD bay fan mount
and the all important high-tech-spill-proof 9L square plastic tub from the $2 shop.

In theory, if I ever needed a 5-6L starter, I could just I wash/sanitise the 9L square plastic tub (it has a lid) and use it directly.
 

LethalCorpse

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Highly recommended. Don't leave your stirplate unattended without spill protection
 

501

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Hey Wolfy,
are you using one of those 3 speed case fans ?
no pot mentioned.

Cheers
 

Wolfy

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Hey Wolfy,
are you using one of those 3 speed case fans ?
no pot mentioned.
While we do use the 3-speed fans on the computers we have here, I don't think they would be that useful for the stir plate.
The fan used on the the stir plate comes pre-assembled with an adjustable knob/dial, which I presume is connected to a pot and any other electronics required.
Here is a picture (from some random Google'd website) of the fan I'm using:

I think you can buy the fully adjustable speed controlled fans at most PC shops now days.
 

501

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Thanks mate :chug:
 

praxis178

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LM317_3.JPG

So if using this circuit what changes would need to be made to use it with a 5V supply and fan? Although I can solder (quite well, been doing it since I was ~10), I know next to nothing about electronic components etc.
 

BjornJ

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I went to Jaycar again on Saturday, asking for some help to get that PMW "thingy" to control the fan speed.
After a bit of digging in their system they found that it stands for Pulse Width Modulator, and that they don't have any.
Or at least that there is nothing "ready" I could buy.

Am I looking for a 12 V power supply that has a "PWM" inbuilt and a knob to regulate the power, or is this PWM thing something I have to put between the fan and the power supply I already have?

thanks
Bjorn
(with no idea on this whole electronics thing :lol: but some of you may already have gathered that)
 

LethalCorpse

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dude, you need a fan speed controller from any computer store.
 

Banshee

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I went to Jaycar again on Saturday, asking for some help to get that PMW "thingy" to control the fan speed.
After a bit of digging in their system they found that it stands for Pulse Width Modulator, and that they don't have any.
Or at least that there is nothing "ready" I could buy.

Am I looking for a 12 V power supply that has a "PWM" inbuilt and a knob to regulate the power, or is this PWM thing something I have to put between the fan and the power supply I already have?

thanks
Bjorn
(with no idea on this whole electronics thing :lol: but some of you may already have gathered that)
http://www.jaycar.com.au/productResults.as...keyform=KEYWORD

look here. I believe you through away the trimpot and wire in a 10k pot.

Others here may be able to help where and how to wire in the pot.
 

LethalCorpse

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You've seen Bjorn's previous posts, and you want to point him at a soldering iron and say "have at it"?
 

BjornJ

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You've seen Bjorn's previous posts, and you want to point him at a soldering iron and say "have at it"?

HEHEHE, exactly what I was thinking!

Any electronics kit will be a bit to advanced for me by the looks of things.

That's why I was hoping for that PWM thingy to come and be a part I just buy and plug in :)


thanks
Bjorn
 

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