Commercial quality stir plates at affordable prices!
Look around the net and you'll find plans for hundreds of
magnetic stir plate
plans, from units stuffed in cheap plastic food containers to others built
in extravagant cabinets. You can also find low cost stirplates for sale on the net very
cheap, less than $50.00 cheap! But look a little closer and you'll discover
that all of these are based on someone's "home built
project". Now, I'm the first to say "save money wherever you can" and the
homebrew community can get quite creative when it comes to saving a few
dollars. But, why buy someone else's home built project when you can
build your own?
You won't see ours for sale for $50.00! But why are our magnetic stir plates more expensive than those cheap
ones you see on the net? The greatest cost difference between our unit and the
theirs is the commercial quality housings we chose for ours.
The housings we use are sturdy enough to support any size starter you dare
place on our stirplate! The next greatest cost difference is the PWM
circuit we designed and produce ourselves. PWM provides superior speed regulation over any
other circuit, even a speed controller based on a LM317 regulator.
Also, a note on warranties. There is no such thing as a
lifetime warranty. A company who offers a lifetime warranty is doing so for
marketing purposes. They understand that once a product gets through it's
early life failure stage they will see very few failures and even less
returns. And the "lifetime warranties" offered by individuals? Those are usually
only good until the individual has decided to move on to something else -
usually in one to three years.
Our units ship with a 1 year, 3 month warranty
against workmanship defects and the warranty extends from the manufacture
date of the product. This loosely translates into a 1 year warranty with up
to 3 months buffer for time the stir plate to sit on our shelves or our
distributor's shelves. Why did we settle on this time period? Because we
understand that almost all consumer products fail during the first three
months and after that period, most customers will enjoy many years of
trouble free service from their stirplate. In other words, a one year
warranty will cover any failure that may be our fault.
Now, watch us on
YouTube!
Home Designed Stir Plates
Home built magnetic stirplates can be loosely lumped into three
categories, LM317 regulator based, Rheostat base and model Train Transformer based.
And although all three designs work, we discovered through experimentation that
each suffers from one or more basic design flaw.
LM317 Voltage Regulator Based
These designs use a LM317 voltage regulator to vary
the voltage supplied to the motor and the motor speeds up & slows down based
on what you set the voltage to. Most home built stir plates are based on
this design because it's cheap and easy to build. We have 3 issues with this design.
The stirplate won't self start at slow speeds and is
easy to stall at slow speeds.
On the ones we build, only about 2/3 of the adjustment range was useable - the lower 1/3 of the
speed setting would not even spin the motor.
The LM317 regulator can produce a lot of heat, so much that you will
need a heat sink inside the stir plate box & the last thing you need is
an additional head source sitting under your yeast culture.
Rheostat Based
These designs use a rheostat, basically a large
variable resistor, to vary the motor speed. These designs are also extremely
simple to build - you just wire the rheostat in series with the motor. Of all the designs we tested,
this one seemed the least reliable.
Just like the LM317 regulator design, the rheostat
based design won't self start at slow speeds and is easy to stall at
slow speeds.
Only about 1/2 of the adjustment range is useable - the lower 1/2 of the
speed setting won't even spin the motor.
The one we tried seemed to stall at slow speed after the yeast culture
ran for a while.
Model Train Transformer Based
These designs use a model train transformer to supply power
to the motor and the varying the voltage changes the motor speed. These
actually
make decent stirplate power supplies, assuming you to have a train
transformer laying around somewhere. The other advantage is that any heat
generated is outside and away from the box - the transformer gets hot, not
the box.
Just like the LM317 design, the train transformer
based design won't self start at slow speeds and is easy to stall at
slow speeds.
Only about 2/3 of the adjustment range is useable - the lower 1/3 of the
speed setting won't even spin the motor.
Our overall observations? None of these designs start well
at slow speeds and all stall at slow speeds, the speed you need to run at to
grow your yeast culture. A PWM based unit does not exhibit
these symptoms because a PWM regulated motor still has its full starting torque
even at slow speeds. This is why we chose a PWM design even though we could have
designed a stirplate around any of these other technologies for less money.
And What Did We Do Different with our design?
Our magnetic stirplates feature:
 PWM Technology - PWM (Pulse
Width Modulation) technology is a better solution than a regulator based
controller - PWM allows better motor speed control with less wasted energy.
This means no heat from the box that could raise your yeast
culture temperature higher than expected. PWM also translates into better
speed regulation and a product that starts better and is less likely to
stall at slow speeds.
Low Power Consumption - PWM
also means less power consumption. Regulator based designs waste a lot
of energy - if the speed control set to half, 1/2 the energy is used to
drive the motor while 1/2 the energy is turned into waste heat. And if the
speed control set to one quarter, 1/4 the energy is used to drive the motor
while 3/4 the energy is turned into waste heat. With a PWM system, power is
fed to the motor in varying widths of full-on - full-off pulses.
For 1/2 speed, the pulses are 1/2 on & 1/2 off. For quarter speed, the
pulses are 1/4 on & 3/4 off. And because power is always all the way on or
all the way off with PWM, there is no waste heat.
External DC Power Supply Included
- By using a UL approved external plug-in DC power supply, we moved one more
potential source of heat away from your yeast starter. This also makes the power
supply user replaceable in the unlikely case that it should fail.
Professionally Designed - All
of our controller cards are professionally designed using state of the art
PCB design and layout software.
Professionally Manufactured -
Built on commercial quality double sided 0.062" FR4 PCB's with 1 ounce
copper and full solder mask on both sides. The same quality construction you
will find in any high-end electronics equipment. 100% Tested Product with a
10% sample subjected to a 24
hour run-in. As of 12/18/09, we've had zero run-in test failures. All of our units are tested with 2000 ML Borosilicate Glass
Erlenmeyer Flasks of water before shipping.
Tough, High Impact Polystyrene Housing -
No cheap Radio Shack project box here. We designed our stir plate to fit
inside a commercial quality polystyrene housing that's strong enough to
support any flask that will sit on the box.
Designed around Neodymium Rare Earth Magnets
- No used or surplus hard drive magnets are used in our designs!
Includes 1.2" long Stir Bar -
We ship with two 1.2" long X 3/16" diameter stir bars. We originally started
with a 1.5" stir bar but discovered that a 1.2" long stir bar stays centered
on the magnets better. Also, a 1.2" stir bar seems to work great in a
container as small as a 500 ml flask, as large as a 1 gallon jug or anything
in between. You need two stir bars, one to hold against the outside of the
flask to hold the inside stir bar in place while pouring out your starter.
Bright, large power indicator
- We did not skimp on the power-on light - large and bright enough to see
from across the room.
Linear speed Control & Control Range that you can Use
- We designed the speed control in such a way that the entire adjustment
range is useable. Most home built projects are set-up so that only 1/2 to
2/3 of the adjustment range is useable. Our design
gives the user full adjustment range for increased sensitivity. Note: Even
with our adjustment range, some settings will be too fast or too slow for
some starters.
Contact Information
- Postal address
-
12021 South Memorial Pkwy, Suite N-4, Huntsville, AL 35803
- Electronic mail
- General Information:
sales@stir-plate.com
Sales:
sales@stir-plate.com
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