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Offlinenoiz
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Registered: 08/20/13
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Magnetic Stirrer Speed Control Help
    #18847526 - 09/16/13 03:07 AM (10 years, 5 months ago)

So I tried to make a magnetic stirrer and everything works well except I cant control the speed here are two pics one is my fan one is my router plug. Any help would be awesome im a noob with the electronics so take it easy thanks.

[image][/image]

[image][/image]


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Offlinehuffinglue
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Re: Magnetic Stirrer Speed Control Help [Re: noiz]
    #18847577 - 09/16/13 03:53 AM (10 years, 5 months ago)

I have no idea, but I know adding a dimmer switch to an aquarium filter will burn the motor out for some reason if you turn it down. I'm an electric newb too, but I read that on a fish forum...


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I fucking hate grammer nazis! Yes, I can't spell. Yes, I don't have perfect grammer. I post from my phone and dont give a shit about people whose lifes are so boring they get off on putting people down for not having perfect fucking grammer, even though they know excactly what there saying.. Fuck You. It's just a ride mang...


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OfflineSockadin
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Re: Magnetic Stirrer Speed Control Help [Re: huffinglue]
    #18847647 - 09/16/13 04:39 AM (10 years, 5 months ago)

Try Ohm's Law for that dimmer switch.

Everything in America runs on a preset 60hz.

http://en.wikipedia.org/wiki/Ohm's_law





Your problem is your resistance, when you install a dimmer it increases or decreases resistance. This will raise or lower your current. If you do that to a motor it can throw off the amount of current going through the brushes into the armature, and back through the winding. If the current is high, the armature spins faster, if there is more resistance, than the strength is lower.


Crash course in why you shouldn't fuck with electricity.


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InvisiblePestile

Registered: 05/02/13
Posts: 875
Loc: Northern Europe
Re: Magnetic Stirrer Speed Control Help [Re: Sockadin]
    #18847662 - 09/16/13 04:47 AM (10 years, 5 months ago)



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OfflineFunnyLight
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Re: Magnetic Stirrer Speed Control Help [Re: Pestile]
    #18847932 - 09/16/13 07:24 AM (10 years, 5 months ago)

Couple of things going on here.

First, the main idea is that you want to adjust the voltage going into your DC Brushless Fan (fancy name for a fan with a nice motor). Adjusting the voltage being fed to a motor will ultimately adjust it's speed.

That fan looks like it's pretty beefy. It has "12v, 2.50A" specs on it. Which means, that it CAN pull about 2.50Amps of current at 12v. And that 12v is DC, not AC. This means you do NOT want to use that little dimmer switch Pestilence listed above.

Looking at the power supply (or wall wart) it's listed at 12v and 1.0A. This means that it will provide the correct voltage of 12v DC, but it may not be able to provide enough current. So a bigger supply, MIGHT be needed, but not necessarily. It's worth a shot to try to get it all hooked up.

The best way to control the speed of the fan would be to hook up your power supply to a voltage regulator, like this one. Then run that regulated, or stepped down voltage to the fan.

This might seem complicated and daunting, but in reality it's not. People naturally feel very uneasy messing with electricity.


--------------------
The most powerful drive through the ascent of man, is pleasure in his own skill.
J. Bronowski

Home of delicious "Psychedelic Nyotaimori".
Thanks Lemmingp for that.

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OfflinePussyFart
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Re: Magnetic Stirrer Speed Control Help [Re: FunnyLight]
    #18847942 - 09/16/13 07:30 AM (10 years, 5 months ago)

All he needs is a 10K linear potentiometer in line...that is all.

It will act as the "dimmer switch".

http://www.lmgtfy.com/?q=10k+linear+potentiometer


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OfflineFunnyLight
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Re: Magnetic Stirrer Speed Control Help [Re: PussyFart]
    #18848935 - 09/16/13 12:30 PM (10 years, 5 months ago)

10K seems pretty high. He'll have next to no adjustment range. I it'll act pretty much like an on/off switch.

A 100-Ohm might get you something useful, but I'm still weary of the rating on that fan.

EDIT:
You may be okay if you trim off all of those fan blades. Still, 10K is a huge amount of resistance. Go to radio shack, pick up 100Ohm, and 10KOhm if ya can.


--------------------
The most powerful drive through the ascent of man, is pleasure in his own skill.
J. Bronowski

Home of delicious "Psychedelic Nyotaimori".
Thanks Lemmingp for that.

:mushroom2::grin::mushroom2:


Edited by FunnyLight (09/16/13 12:36 PM)


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OfflinePussyFart
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Re: Magnetic Stirrer Speed Control Help [Re: FunnyLight]
    #18849050 - 09/16/13 12:59 PM (10 years, 5 months ago)

Quote:

FunnyLight said:
10K seems pretty high. He'll have next to no adjustment range. I it'll act pretty much like an on/off switch. 



I made one with a 50K and it was like an on/off switch, but I still could just barely, and I mean barely control the speed.

In my mind, a 10K would have been perfect, but still might have been too much.


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Offlinenoiz
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Re: Magnetic Stirrer Speed Control Help [Re: PussyFart]
    #18849305 - 09/16/13 01:56 PM (10 years, 5 months ago)

Sorry you guys I was up really late last night and it turns out I left out some needed info. So I made this about a week ago hooked it all up to a left over light switch it worked but the fan starts out slow then gets faster and faster until its hauling ass then it slows down and starts over. So first thing i tried was a dimmer switch well that failed because im stupid and havent messed around with electronics for a long long time but thats part of the fun building this. Anyways i new i was fucked so i went to radio shack turns out none of the 3 guys working there knew anything about what i was doing except for this kinda cute girl. she sent me home with this potentiometer but said it prolly wont work because i didnt have any of the specs on me. So i went home hooked it up and the fan doesnt even power up but thanks to you guys im going to go back get a 10k potentiometer and that girls number and maybe she can come over and help me build it lmao.

But seriously thanks im going to try it out and keep you guys posted. [image][/image]
[image][/image]


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OfflineTheReckoning
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Re: Magnetic Stirrer Speed Control Help [Re: noiz]
    #18849332 - 09/16/13 02:03 PM (10 years, 5 months ago)



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Offlinenoiz
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Re: Magnetic Stirrer Speed Control Help [Re: TheReckoning]
    #18849364 - 09/16/13 02:12 PM (10 years, 5 months ago)

Yeah I wish I would have thought about that before cutting the end off my fan cords and tossing it and I dont think my friends wants to give me another fan after I mess this one up lol. When i was younger i would make all kinds of things with old electronics like cars and boats and I was just thinking yeah ill just rig up some sort of dimmer switch and it will work then i realized im retarded and its been a while...


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OfflineFunnyLight
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Re: Magnetic Stirrer Speed Control Help [Re: noiz]
    #18849400 - 09/16/13 02:24 PM (10 years, 5 months ago)

That might all work fine. No point in NOT trying it out.

If you notice the wall wart getting hot. Try trimming the fan blades off the fan. Try to trim them as close to the plastic base as you can so you can keep everything consistent and balanced.

That 5K potentiometer is an audio-taper. Meaning it's logarithmic. Say with a linear pot you give it a full rotation, you would have doubled your resistance (slowed down your fan by 1/2). With a logarithmic/audio-taper when you give it a full turn you increase the resistance by a factor of 10, or slowed down your fan by a factor of 10.

But you've got all the parts, so wing it together and see how it behaves.


--------------------
The most powerful drive through the ascent of man, is pleasure in his own skill.
J. Bronowski

Home of delicious "Psychedelic Nyotaimori".
Thanks Lemmingp for that.

:mushroom2::grin::mushroom2:


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Offlinenoiz
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Re: Magnetic Stirrer Speed Control Help [Re: FunnyLight]
    #18849424 - 09/16/13 02:31 PM (10 years, 5 months ago)

Thank you but sorry what is a wall wart?  :shrug:


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OfflineFunnyLight
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Re: Magnetic Stirrer Speed Control Help [Re: noiz]
    #18850116 - 09/16/13 04:48 PM (10 years, 5 months ago)

the wall wart is the little plug in power supply.

sits on the wall like a wart. or some such shenanigans.


--------------------
The most powerful drive through the ascent of man, is pleasure in his own skill.
J. Bronowski

Home of delicious "Psychedelic Nyotaimori".
Thanks Lemmingp for that.

:mushroom2::grin::mushroom2:


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Offlinenoiz
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Re: Magnetic Stirrer Speed Control Help [Re: FunnyLight]
    #18887583 - 09/25/13 01:07 AM (10 years, 4 months ago)

Notahacker420 was right I bought a 10k potentiometer and it gets the job done thanks :smile:


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OfflineSockadin
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Re: Magnetic Stirrer Speed Control Help [Re: noiz]
    #18887759 - 09/25/13 03:17 AM (10 years, 4 months ago)

I think going to a dry cell 12v battery and using all DC power would solve your problem here. The initial issue is the AC-DC creates a trickle charge. All that stuff your powering up would work better on a little battery backup power supply battery.


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OfflineFunnyLight
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Re: Magnetic Stirrer Speed Control Help [Re: noiz]
    #18888085 - 09/25/13 07:27 AM (10 years, 4 months ago)

:thumbup: awesome man!



What do you mean "trickle charge"? If he runs from a battery then he's gatta worry about it dieing and no longer stirring his stirrables?


--------------------
The most powerful drive through the ascent of man, is pleasure in his own skill.
J. Bronowski

Home of delicious "Psychedelic Nyotaimori".
Thanks Lemmingp for that.

:mushroom2::grin::mushroom2:


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InvisibleFred Teddy
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Registered: 07/18/11
Posts: 208
Re: Magnetic Stirrer Speed Control Help [Re: FunnyLight]
    #18888287 - 09/25/13 08:40 AM (10 years, 4 months ago)

DO NOT try to hook a potentiometer up to any AC voltage, especially line voltage !!! You will fry something, maybe yourself or others.

AC dimmer switches work on 'pulse width modulation' - PWM. PWM turns on and off a set AC voltage to the device. The more off time, the slower the motor or dimmer the light. Running an AC motor under-voltage will burn out the motor. Thats why AC motor controllers and dimmers use PWM and not a simple potentiometer.

PWM can also be used with DC motor speed control ( recommended ), but the simpler method is to use a voltage divider - a potentiometer hooked up as such. Not very efficient, and if not done correctly, wiring can get hot and cause problems. With the small computer fans that don't draw a lot of current, this is not a problem, but with higher current devices you run the risk of melting wires, burning down the house, etc.

DC motor control is voltage dependent. Resistance hooked up in-line will not work for DC motor speed control, it must be hooked up as a divider. In-line resistance will reduce current only, and act like an on-off switch at some point. You can get some control that way but it will be touchy. 

If you want to hook up a diy potentiometer to a DC circuit, you need some math to choose the correct value, and hook it up correctly. I can elaborate on this if anyone wants. For those that say " just hook up this simple device" - its not that simple. 

Peace,
FT


--------------------
... its all about fun and games ... and no one has poked their eye out ... yet.

Peace.

Disclaimer: Fact is ... Its all fiction.


Edited by Fred Teddy (09/25/13 09:03 AM)


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OfflinePussyFart
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Re: Magnetic Stirrer Speed Control Help [Re: Fred Teddy]
    #18888342 - 09/25/13 08:54 AM (10 years, 4 months ago)

No one is talking about using AC, he is converting 120v AC to 12v DC then using it.

Hence the wall wart.


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InvisibleFred Teddy
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Re: Magnetic Stirrer Speed Control Help [Re: PussyFart]
    #18888451 - 09/25/13 09:23 AM (10 years, 4 months ago)

Notahacker-

I know. I just wanted to remind people of the fact. There is a lot of misinformed postings on "electricity" on this forum. Honestly, some of the stuff I've seen previously posted over the years is downright scarey.

As an aside for instance, the OP's power supply wall wart is not long for this world if he runs a 2.5 amp fan off a 1 amp power supply. Its not going to burn the house down, but it won't last long.

Peace,
FT


--------------------
... its all about fun and games ... and no one has poked their eye out ... yet.

Peace.

Disclaimer: Fact is ... Its all fiction.


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