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Some of these posts are very old and might contain outdated information. You may wish to search for newer posts instead.
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lovingtickels
wit a engineringdegre wo neds tono how 2 spel


Registered: 04/10/07
Posts: 220
Loc: North or South America
Last seen: 11 years, 11 months
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speed controller for lc magnetic stirrer
#7979783 - 02/04/08 08:27 PM (16 years, 15 days ago) |
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i built my first magnet stirrer today. it works great, but not so great... i am using resistors to control the current using ohms law and they are getting so hot they fail. i am using a 12v 500mah power supply with my cooling fan. the vortex is absolutely dependent on the rpm. a range i am reading in volts to be withing 300 rpms. seams i have put myself in a hot tight spot. does anyone have any experience with controlling current to such a motor inexpensively and conveniently. hell Ive tried every combination of resistors i have on hand and at the highest wattage. the resistance needs to be somewhere between 11250 ohms and 11220 dependent on the heat generated and degradation time of the resistors. i need something variable and reliable/
-------------------- I never guess. It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. Sir Arthur Conan Doyle Mistakes are a part of being human. Appreciate your mistakes for what they are: precious life lessons that can only be learned the hard way. Unless it's a fatal mistake, which, at least, others can learn from. - Al Franken
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The shroomy 1
Luminous beings surround me




Registered: 03/27/07
Posts: 5,543
Loc: The Aether
Last seen: 5 months, 23 days
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Re: speed controller for lc magnetic stirrer [Re: lovingtickels]
#7979954 - 02/04/08 08:56 PM (16 years, 15 days ago) |
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I don't know how much this will help you, but here is a link to my very first attempt on making a Magnetic stirrer. It will show what I used to control the speed. The controller worked great for my application. Don't really know what yours is.https://www.shroomery.org/forums/showflat.php/Number/7226049#7226049
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AMU Q&A thread.
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RogerRabbit
Bans for Pleasure



Registered: 03/26/03
Posts: 42,214
Loc: Seattle
Last seen: 11 months, 21 days
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Re: speed controller for lc magnetic stirrer [Re: The shroomy 1]
#7980017 - 02/04/08 09:05 PM (16 years, 15 days ago) |
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Is it a DC motor? If so, 12 volts at 500ma means you need a six watt resistor, but if you're using 11 K ohms, it sounds like you're trying to control an AC fan by reducing current, which doesn't work.
If it's a DC fan, try getting a power supply of lower voltage. A rheostat of the correct watt rating would be large and expensive. If it's an AC fan, get a motor speed controller. http://www.littlegreenhouse.com/accessory/controls2.shtml RR
-------------------- Download Let's Grow Mushrooms semper in excretia sumus solim profundum variat "I've never had a failed experiment. I've only discovered 10,000 methods which do not work." Thomas Edison
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lovingtickels
wit a engineringdegre wo neds tono how 2 spel


Registered: 04/10/07
Posts: 220
Loc: North or South America
Last seen: 11 years, 11 months
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Re: speed controller for lc magnetic stirrer [Re: RogerRabbit]
#7980100 - 02/04/08 09:17 PM (16 years, 15 days ago) |
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12vDC .35a pc case fan. ps is 12vdc 650mA. gotta find a proper potentiometer. thanks for the link that helped, guess i should have searched first.
-------------------- I never guess. It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. Sir Arthur Conan Doyle Mistakes are a part of being human. Appreciate your mistakes for what they are: precious life lessons that can only be learned the hard way. Unless it's a fatal mistake, which, at least, others can learn from. - Al Franken
Edited by lovingtickels (02/04/08 09:20 PM)
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Cryogenicz
what?


Registered: 07/01/04
Posts: 2,421
Loc: Oregon
Last seen: 4 years, 8 months
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Re: speed controller for lc magnetic stirrer [Re: lovingtickels]
#7980155 - 02/04/08 09:29 PM (16 years, 15 days ago) |
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why not just buy a cheap magnetic stirrer... this seems like such a PITA.
-Graham
-------------------- www.MycoPath.com Mushroom Spawn, Cultures, Fungi Bags, Casings, Master Grain Jars, Bags for In-vitro, Laboratory supplies, and much more! Mushroom Supplies. Fast Turnaround Times. Great Service. orders@mycopath.com enter code shroomery for 10% off product. www.FungiForum.com
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lovingtickels
wit a engineringdegre wo neds tono how 2 spel


Registered: 04/10/07
Posts: 220
Loc: North or South America
Last seen: 11 years, 11 months
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Re: speed controller for lc magnetic stirrer [Re: Cryogenicz]
#7980162 - 02/04/08 09:30 PM (16 years, 15 days ago) |
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cause i got zero dollars and two hours in it and what fun is buying something. hell i got a friend in amsterdam that would attempt to send what ever i want. but picking it out of poo. priceless. research, work, and accomplish. that is what satisfies me in this world
Edited by lovingtickels (02/04/08 09:33 PM)
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Cryogenicz
what?


Registered: 07/01/04
Posts: 2,421
Loc: Oregon
Last seen: 4 years, 8 months
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Re: speed controller for lc magnetic stirrer [Re: lovingtickels]
#7980192 - 02/04/08 09:34 PM (16 years, 15 days ago) |
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-------------------- www.MycoPath.com Mushroom Spawn, Cultures, Fungi Bags, Casings, Master Grain Jars, Bags for In-vitro, Laboratory supplies, and much more! Mushroom Supplies. Fast Turnaround Times. Great Service. orders@mycopath.com enter code shroomery for 10% off product. www.FungiForum.com
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dumbfounded1600
Stranger

Registered: 07/29/07
Posts: 2,624
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Re: speed controller for lc magnetic stirrer [Re: Cryogenicz]
#7980268 - 02/04/08 09:43 PM (16 years, 15 days ago) |
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lovingtickels
wit a engineringdegre wo neds tono how 2 spel


Registered: 04/10/07
Posts: 220
Loc: North or South America
Last seen: 11 years, 11 months
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Re: speed controller for lc magnetic stirrer [Re: Cryogenicz]
#7980275 - 02/04/08 09:44 PM (16 years, 15 days ago) |
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no no no non ononnonnononononnonononononnaw but thanks yo. ain't no fun that way. and thats what this is to me. fun. ill post some pics tomorrow of my project. sorry if i am wasting yalls time. but somepeople smoke herb, some people beat there wives.. i try to diy everything
-------------------- I never guess. It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. Sir Arthur Conan Doyle Mistakes are a part of being human. Appreciate your mistakes for what they are: precious life lessons that can only be learned the hard way. Unless it's a fatal mistake, which, at least, others can learn from. - Al Franken
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RogerRabbit
Bans for Pleasure



Registered: 03/26/03
Posts: 42,214
Loc: Seattle
Last seen: 11 months, 21 days
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Re: speed controller for lc magnetic stirrer [Re: lovingtickels]
#7980444 - 02/04/08 10:09 PM (16 years, 15 days ago) |
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12 volts at .35 amps is 4.2 watts. Your pot will have to be able to dissipate that much heat or burn up. A 100 ohm rheostat should be able to give full speed control, provided you find one rated 4 watts or above. Don't use the motor speed controller I linked to above on a DC motor. You could probably run it on a 6 volt battery charger to get half speed. RR
-------------------- Download Let's Grow Mushrooms semper in excretia sumus solim profundum variat "I've never had a failed experiment. I've only discovered 10,000 methods which do not work." Thomas Edison
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lovingtickels
wit a engineringdegre wo neds tono how 2 spel


Registered: 04/10/07
Posts: 220
Loc: North or South America
Last seen: 11 years, 11 months
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Re: speed controller for lc magnetic stirrer [Re: RogerRabbit]
#7980590 - 02/04/08 10:29 PM (16 years, 15 days ago) |
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yea i need way less then half speed, just enough to make it turn. almost like a fluorescent light enough cornet to start it then a steady current at the lowest possible speed to create a vortex maybe i am doing something seriously wrong/ as no one else has had this problem/ possible bad fan selection... oh yea im drunk writing this post so i might have to edit it and apologize tomorrow
-------------------- I never guess. It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. Sir Arthur Conan Doyle Mistakes are a part of being human. Appreciate your mistakes for what they are: precious life lessons that can only be learned the hard way. Unless it's a fatal mistake, which, at least, others can learn from. - Al Franken
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MayorMcCheese
Mayor



Registered: 11/10/07
Posts: 390
Last seen: 8 years, 3 months
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Re: speed controller for lc magnetic stirrer [Re: lovingtickels]
#7981039 - 02/05/08 12:07 AM (16 years, 15 days ago) |
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You could get a variable voltage ac adapter from radio shack to switch between a few common voltages.
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Sillicybin
Registered: 02/14/05
Posts: 2,134
Loc:
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Re: speed controller for lc magnetic stirrer [Re: MayorMcCheese]
#7981703 - 02/05/08 08:19 AM (16 years, 14 days ago) |
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12VDC fans slow down great if you use a 7 volt power supply. If you're looking for adjustable speed, the best possible thing you can use is a PWM fan speed controller.
http://www.frozencpu.com/products/992/bus-34/FrozenCPU_Black_PWM_6x_Fan_Controller_525_Bay.html http://www.nomad.ee/micros/pwm555.html
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RogerRabbit
Bans for Pleasure



Registered: 03/26/03
Posts: 42,214
Loc: Seattle
Last seen: 11 months, 21 days
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Re: speed controller for lc magnetic stirrer [Re: MayorMcCheese]
#7981704 - 02/05/08 08:19 AM (16 years, 14 days ago) |
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Quote:
MayorMcCheese said: You could get a variable voltage ac adapter from radio shack to switch between a few common voltages.
NEVER run a DC motor on AC current. RR
-------------------- Download Let's Grow Mushrooms semper in excretia sumus solim profundum variat "I've never had a failed experiment. I've only discovered 10,000 methods which do not work." Thomas Edison
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sandman420
Saint PP


Registered: 06/17/04
Posts: 5,384
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Re: speed controller for lc magnetic stirrer [Re: RogerRabbit]
#7981763 - 02/05/08 08:45 AM (16 years, 14 days ago) |
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coulda just bought a real magnetic stirrer used for like 20-30 bux. Are you stirring with homemade stir bars too? Growing with homemade spawn bags? Sometimes it doesn't pay to do-it-yourself.
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Serial
Cake or Death?




Registered: 11/10/07
Posts: 58
Loc: Middle of Nowhere
Last seen: 8 years, 11 months
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Re: speed controller for lc magnetic stirrer [Re: sandman420]
#7981804 - 02/05/08 09:04 AM (16 years, 14 days ago) |
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Mine is made out of a 80mm case fan with the fins broken off, a 12v dc 300ma power adaptor, and a volume controller out of a cdrom drive, i cut away the part of the circuit board i wanted and soldered on my fan leads. It works pretty well, it doesn't do well at slow but its got a solid medium to fast. Pretty good for 10 minutes work and free 
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shroober
Myco Junkie

Registered: 01/02/08
Posts: 879
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Re: speed controller for lc magnetic stirrer [Re: sandman420]
#7981912 - 02/05/08 09:43 AM (16 years, 14 days ago) |
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Quote:
sandman420 said: coulda just bought a real magnetic stirrer used for like 20-30 bux. Are you stirring with homemade stir bars too? Growing with homemade spawn bags? Sometimes it doesn't pay to do-it-yourself.
some people actually like building stuff themselves, even if it's not as efficient or even if it's more costly. this is another reason many people choose to build elaborate FCs. Obviously buying a rubbermaid box and drilling some holes in it would be easier but in my opinion its not nearly as fun as forming your own ideas and creating something unique. some people are creative, some people are not, simple as that.
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lovingtickels
wit a engineringdegre wo neds tono how 2 spel


Registered: 04/10/07
Posts: 220
Loc: North or South America
Last seen: 11 years, 11 months
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Re: speed controller for lc magnetic stirrer [Re: shroober]
#7985385 - 02/06/08 12:56 AM (16 years, 14 days ago) |
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it doesn't have to pay. rr i think he was talking about those ac to dc fixed amperage variable voltage pieces of crap with the ten different changeable tips.?. didn't have time tonight to attempt the potentiometer but a friend did send me a schematic he thought would work. and it just so happens i have it all on hand. even the pcd mount pot. ill bread board it this weekend when i get to sleep late...till 7 am wooo hooooo and recouperate from a long work week. ill get to the pics then. i also can't reiterate... i can buy it, but why. im all about diy, besides the martha, the jars, the aluminum foil, syringes, ultrasonic and cool mist, tape etc.... im not just here to grow, im here to diy
-------------------- I never guess. It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. Sir Arthur Conan Doyle Mistakes are a part of being human. Appreciate your mistakes for what they are: precious life lessons that can only be learned the hard way. Unless it's a fatal mistake, which, at least, others can learn from. - Al Franken
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