Tight Arse Stir Plate

[LethalCorpse]

bugger, thought they had 20K pots. Use a 680ohm resistor and a 5k pot instead. Pot can be RP3508 or RP7508, resistor should be RR0568, or if for some crazy reason they've run out (it's been a few years since they stocktaked resistors) RR2770.

 

[schooey]

I don't know if it's been mentioned in the umpteem posts before, but I reckon your ideal stir bar is a 40 mm teflon job. I went all out with my first effort and got a 3L conical flask and a 60mm stir bar (building a big starter for a 50L batch) and it was a pain in the arse to keep the stir bar centred. I have since got a 40mm bar and it works an absolute treat.

 

[Franko]

This is a question for the electronics gurus
Ive acquired a few 48 Vdc 120mm fans from work and would like to know what type of circuit would be best to use these for a stirplate.
The fans are 48 Vdc at .11 amps
The power supplies I have are 48 Vdc at 250ma

Many thanks
Franko

 

[LethalCorpse]

a 12vdc power supply, along with the circuit I posted before, should do nicely. You'll not want to run them anywhere near full speed, so as long as they start at 12V, they should be good to go.

 

[Franko]

a 12vdc power supply, along with the circuit I posted before, should do nicely. You'll not want to run them anywhere near full speed, so as long as they start at 12V, they should be good to go.

can only get it to start at 12v by spinning the fan manually thats with a 12V 200ma transformer.
12V 500ma did nothing at all

Franko

 

[LethalCorpse]

the current rating makes bugger all difference - it's just a maximum that the pack can deliver, the load determines the current draw, which is 110mA max at 48V, and rather a lot less at 12V.

So 12V didn't work eh? Hmm...A 48V controller is quite possible, but rather a lot more complex than 12V. Can you get your hands on a 24V supply? That should start it, and you can use the same controller by replacing the resistor with a 3kohm and the pot with a 50k. You might find the speed is fine with 24V straight off.

If all that fails you'll need a 48Vin switchmode variable PSU design.

 

[Franko]

the current rating makes bugger all difference - it's just a maximum that the pack can deliver, the load determines the current draw, which is 110mA max at 48V, and rather a lot less at 12V.

So 12V didn't work eh? Hmm...A 48V controller is quite possible, but rather a lot more complex than 12V. Can you get your hands on a 24V supply? That should start it, and you can use the same controller by replacing the resistor with a 3kohm and the pot with a 50k. You might find the speed is fine with 24V straight off.

If all that fails you'll need a 48Vin switchmode variable PSU design.

just got it spinning with a 15vdc 1amp plugpack it spins straight away on startup

would like to slow it down a little

Franko

 

[newguy]

Here is a circuit that will do the trick. Look at the "Typical Application" schematic in the middle of the page in the link. It's the same one I use for my stir plate but I use a 12V supply and 12V fan for mine. The adjustable resistor (R2) is what allows for voltage (speed) control.

 

[LethalCorpse]

If it won't start on 12V but is too quick on a 15V, the regulator circuit won't help you much, unless the 12V was a regulated pack and the 15V wasn't. You need to use a thing called Pulse Width Modulation (PWM) which works by switching the power on and off very quickly. If it's on for 70% of the time, then the fan gets an average of 70% full power. The big advantage for you, though, is that fans can be driven to much lower speeds, and still start under their own power, than they could with a linear regulator like the LM317. Jaycar has a circuit designed for this purpose, though it's intended for much bigger motors. It's called the 12/24VDC 10A motor speed controller, linky. From memory its input range is 10-28VDC, so your 15V supply should be fine.

 

[Zwickel]

Hi LC, thats a beautiful little thingy, would be great to control the spin of mash stirring motors, such like car wiper motors, as well.

very nice :icon_chickcheers:

 

[kabooby]

Why not use a light dimmer or fan controller. Should still work at the lower voltages

Kabooby :icon_cheers:

 

[LethalCorpse]

nope, sorry. Those things only work on AC power

 

[kabooby]

Of coarse, I looked over the fact that it was a DC motor.

A PWM is the best way to control the speed. If the speed does not need to be controlled than reducing the supply voltage will work. The speed of a DC motor is directly proportional to its supply voltage.

Kabooby :icon_cheers:

 

[crozdog]

Franko,

i have some 240v fans which you could use an off the shelf light dimmer or fan controller with.

Swap you one for a logo or 2 - hang on aren't i still waiting on 1 for a keg :lol:

 

[SJW]

I am not an electronic wiz at all, so why can't I just use one of the two phone chargers I have, a 12v and a 9.6v, and just hook that up to the fan/stir plate and just use the one that spins at the right speed? Does it need to be variable?


Steve

 

[Ross]

I am not an electronic wiz at all, so why can't I just use one of the two phone chargers I have, a 12v and a 9.6v, and just hook that up to the fan/stir plate and just use the one that spins at the right speed? Does it need to be variable?


Steve

Hi steve,

Yes, they really do need to be variable. For starters (no pun intended) you need need a higher speed to get the vortex happening which then needs to be backed off or you'll have yeast flying everywhere.

cheers Ross

 

[schooey]

If you have a phone charger for the power source, Steve, it's only a matter of wiring in a pot between it and the fan to make it variable, no rocket surgery involved.

 

[LethalCorpse]

No, it's not schooey, unless he wants to replace it regularly. Have another read of the thread.

Steve, if you're not confident enough to wire it up yourself, buy a cheap fan controller from any computer parts store. It will do the job.

 

[schooey]

No, it's not schooey, unless he wants to replace it regularly. Have another read of the thread.

Steve, if you're not confident enough to wire it up yourself, buy a cheap fan controller from any computer parts store. It will do the job.

*scratches head*

Buggers me, LC, mine seems to be still going solid after 12 months.

edit: You are right with the fan controller suggestion, quick easy and relatively cheap

 

[LethalCorpse]

Well, then you're very fortunate, aren't you? It's not a good idea dude.