Ss Brewing Technologies Giveaway!

Home Brew Forums > Home Brewing Beer > DIY Projects > Rheostat or Potentiometer for Stirplate?

Reply
 
LinkBack Thread Tools
Old 02-14-2011, 03:48 AM   #1
rrittenhouse
Feedback Score: 0 reviews
Recipes 
 
Join Date: Sep 2009
Location: Newark, Ohio
Posts: 117
Likes Given: 3

Default Rheostat or Potentiometer for Stirplate?

Hello EE's I have a question. I am planning on building a stir-plate and I am seeing designs with a rheostat and others with circuits that were built with a couple components.

Are there any differences/advantages/disadvantages in these designs?

Thanks

__________________
Quote:
Originally Posted by ChshreCat View Post
If you aerated well, you should be fine. They're multiplying. Listen close and you'll hear your yeast humping. Seriously. Give them some privacy and they'll get to work when they're done.
rrittenhouse is offline
 
Reply With Quote Quick reply to this message
Old 02-14-2011, 09:07 AM   #2
rekoob
HBT_SUPPORTER.png
Feedback Score: 0 reviews
 
rekoob's Avatar
Recipes 
 
Join Date: Feb 2011
Location: Norfolk, VA
Posts: 956
Liked 42 Times on 37 Posts
Likes Given: 2

Default

if your going with a DC fan to make your stir plate, you can just use a POT to very the 12 volts to the fan.

not much difference between the two, the POT has a wiper arm, the rheostat has two terminals. either will work for you case, not sure what the price difference is for them. what plans are you following for your build? I suppose that will decide.

__________________

Last edited by rekoob; 02-14-2011 at 09:12 AM. Reason: added info:
rekoob is offline
 
Reply With Quote Quick reply to this message
Old 02-14-2011, 12:04 PM   #3
rrittenhouse
Feedback Score: 0 reviews
Recipes 
 
Join Date: Sep 2009
Location: Newark, Ohio
Posts: 117
Likes Given: 3

Default

The latest plans with the rheostat are located here: http://www.wortomatic.com/articles/B...ast-Suspension

I guess I've read that you need the rest of the circuitry if you go with the pot instead of the rheo but I wanted to confirm this. If its that easy i'm just going to use the rheo. I was told the pots can only handle about 0.25W or so. I am just trying to clear this all up so I can build one.

Thanks again

__________________
Quote:
Originally Posted by ChshreCat View Post
If you aerated well, you should be fine. They're multiplying. Listen close and you'll hear your yeast humping. Seriously. Give them some privacy and they'll get to work when they're done.
rrittenhouse is offline
 
Reply With Quote Quick reply to this message
Old 02-14-2011, 02:07 PM   #4
a10t2
Feedback Score: 0 reviews
Recipes 
 
Join Date: May 2010
Location: Leadville, CO
Posts: 557
Liked 14 Times on 13 Posts
Likes Given: 1

Default

If you're going to use just a pot you need to get one that's rated for at least 2W (assuming you'll be using a 12 VDC power supply). You can also use an LM317 to dissipate the current, in which case the power rating for the pot doesn't really matter. The only additional components needed to put together a basic LM317 circuit would be a resistor and two capacitors. http://seanterrill.com/2010/04/26/bu...ter-stirplate/

__________________
http://seanterrill.com/category/brewing/
Quote:
Originally Posted by monty3777 View Post
squeeze your sack like it owes you money.
a10t2 is offline
 
Reply With Quote Quick reply to this message
Old 02-14-2011, 05:32 PM   #5
rrittenhouse
Feedback Score: 0 reviews
Recipes 
 
Join Date: Sep 2009
Location: Newark, Ohio
Posts: 117
Likes Given: 3

Default

Ok. So unless theres a huge price difference I can just get the rheostat or a 2W pot. As much as I like to tinker sometimes its just nice to simplify things.....at first lol. I'm sure i'll mod it later and add some un-necessary features.

Thanks for the response.

__________________
Quote:
Originally Posted by ChshreCat View Post
If you aerated well, you should be fine. They're multiplying. Listen close and you'll hear your yeast humping. Seriously. Give them some privacy and they'll get to work when they're done.
rrittenhouse is offline
 
Reply With Quote Quick reply to this message
Old 02-14-2011, 06:40 PM   #6
Sawdustguy
Feedback Score: 1 reviews
Recipes 
 
Join Date: Mar 2009
Location: Manorville, New York
Posts: 2,772
Liked 28 Times on 25 Posts

Default

If you get a 2 watt Pot you can simply wire as a rheostat. You can use a simple 12 VDC 1 Amp wallwart as your voltage source. See below.....

__________________

Guy

Sawdustguy is offline
 
Reply With Quote Quick reply to this message
Old 02-14-2011, 07:30 PM   #7
rrittenhouse
Feedback Score: 0 reviews
Recipes 
 
Join Date: Sep 2009
Location: Newark, Ohio
Posts: 117
Likes Given: 3

Default

Does it really need to be a 2W potentiometer? Not that I cant find one but when I do the power calculation is around 50mW. Where did I go wrong?

__________________
Quote:
Originally Posted by ChshreCat View Post
If you aerated well, you should be fine. They're multiplying. Listen close and you'll hear your yeast humping. Seriously. Give them some privacy and they'll get to work when they're done.
rrittenhouse is offline
 
Reply With Quote Quick reply to this message
Old 02-14-2011, 07:54 PM   #8
a10t2
Feedback Score: 0 reviews
Recipes 
 
Join Date: May 2010
Location: Leadville, CO
Posts: 557
Liked 14 Times on 13 Posts
Likes Given: 1

Default

If your fan motor is pulling ~150 mA (roughly average from the ones I've seen), using a 12 V supply, and you want to run the motor at 4 V, the power dissipation in the resistor is:

(12 - 4)(0.15) = 1.2 W

The slower the fan is turning, the more power dissipated in the pot as heat.

__________________
http://seanterrill.com/category/brewing/
Quote:
Originally Posted by monty3777 View Post
squeeze your sack like it owes you money.
a10t2 is offline
 
Reply With Quote Quick reply to this message
Old 02-14-2011, 09:33 PM   #9
rekoob
HBT_SUPPORTER.png
Feedback Score: 0 reviews
 
rekoob's Avatar
Recipes 
 
Join Date: Feb 2011
Location: Norfolk, VA
Posts: 956
Liked 42 Times on 37 Posts
Likes Given: 2

Default

actually, Power=current times voltage. P=IE. so running at 4 volts would be .6 given your current draw. you would have to factor in the resistance to know what the current draw is overall. go with what ever you want as in a pot or a rheostat, if your using a CPU fan for your build its not going to draw enough to make any difference. the higher you get in resistance the less of the "throw" you will use, meaning half the "turns" might not change the speed of the fan.

__________________
rekoob is offline
 
Reply With Quote Quick reply to this message
Old 02-14-2011, 09:39 PM   #10
rekoob
HBT_SUPPORTER.png
Feedback Score: 0 reviews
 
rekoob's Avatar
Recipes 
 
Join Date: Feb 2011
Location: Norfolk, VA
Posts: 956
Liked 42 Times on 37 Posts
Likes Given: 2

Default

http://www.homebrewtalk.com/f51/diy-...easier-225340/

just in case you haven't seen this tread... plenty of info out there.
__________________
rekoob is offline
 
Reply With Quote Quick reply to this message
Reply


Quick Reply
Message:
Options
Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Semi-urgent Potentiometer help Ichthy DIY Projects 5 10-22-2010 12:37 PM
LM317T vs rheostat....stir plate build (cheap!) ekjohns DIY Projects 17 07-14-2010 06:23 PM
Ugh Rheostat RockfordWhite DIY Projects 6 02-04-2008 09:47 PM
A rocker, rheostat, power jack, and fan walk into a bar... ejdischer DIY Projects 7 12-11-2007 05:05 PM
potentiometer help WormBoy DIY Projects 6 09-14-2007 03:53 PM