"I have noticed that the light that shows when the pid is calling
for heat is not steady, it's on and off. I'm pretty sure that helps
with temp overshoot and under temp conditions."
Yup, that's the idea. The PID controller measures not just the current
temperature, but monitors it over time and does some calculus to
determine the optimal power level needed to reach the set point or
maintain it if it's already there. The output of the PID calculation is
not just on or off like a thermostat but a numeric power percentage. It
then takes that number and "pulse code modulates" it--i.e. quickly turns
the element on and off--to achieve the desired power level.
On 1/21/2016 11:51 AM, herman dickens wrote:
Fwiw I just completed a similar operation on my brewtus II today. I
upgraded to a pid. The cost was 235 for all the parts. I had to remove
the old thermowell and thermocouple and install the pid sensor. I
removed the old display and the PID display fit perfectly in the old
opening. I had to drill 2 holes in the base to mount the new relay. I
also had to extend 2 wires that were not long enough. The kit I used
had all of the screws, connectors, heat shrink tubing, and parts
necessary to do the conversion with the exception of the tape dope for
the thermowell. Total time start to finish was a little over an hour.
The pid seems to regulate the temp much better than the old AKO
controller. The temp goes back and forth between 199 and 200. The set
point is 200. I have noticed that the light that shows when the pid is
calling for heat is not steady, it's on and off. I'm pretty sure that
helps with temp overshoot and under temp conditions. ymmv
Herman
On Thu, Jan 21, 2016 at 2:29 PM, Schindler <[email protected]
<mailto:[email protected]>> wrote:
The USA distributor of AKO controllers can help with any questions
http://schindlertechnologies.com/
On Thursday, May 5, 2005 at 10:46:25 AM UTC-5, Doug Shannon wrote:
AKO's New Temperature Controller
First, I have to thank Sean for the hours he has spent on the
phone
with me discussing and guiding me through this process. If it
wasn't
for him, none of this would have been possible.
Description:
AKO's newest controller (model 14725) is capable of displaying
3 digits
in degrees F up to 999F. Temperatures below 100F can be
displayed in
tenths of a degree resolution. This enables the user to set
the all
important offset parameter in tenths of a degree. The new
controller
accepts a J or K type thermocouple allowing for faster
response times
as compared to the stock controller RTD type sensor.
The size of the controller (due to having 3 digits) is
slightly larger
than the stock controller which will require a somewhat bigger
panel
cut out. Although tedious, the current cut out can be made the
correct
size with the use of a dremel tool. The width of the current
cut out
needs to be 1/2 in. wider and the height needs to be increased
by 1/8
in. There are no depth issues.
You can see a picture of the 14725 on the brewtus group under user
folders/Doug.
Programming and Connections:
I connected a common household extension cord to the power
terminal of
the controller. This allowed me to take my time programming the
controller without fear of it affecting the operation of the
brewtus.
Once the controller was programmed which was a simple process
by the
way, I connected it to the brewtus using the same wires used
to connect
the stock controller. There are a total of 4 wires (power, sensor,
relay, and common). As recommended by Sean, I used a 30 ga. K type
sensor installed in the brew boiler's thermo well along side
the stock
sensor in order to hold it in place. As compared to the RTD stock
sensor, the K type has greater accuracy and much faster response.
Finally, I temporarily installed another sensor in the thermo
well so
that, using my Fluke 54, I could test the accuracy and
response of the
new controller.
Initial Testing Results:
After all connections were made and verified I plugged the
brewtus'
power cable into the wall, took a deep breath, and flipped the
power
switch with my barely controllable trembling hand. At this
point, I had
Sean on the phone who was intently listening for explosions
and looking
south outside his office window for mushroom clouds.
Thankfully, there
were none. The controller powered up and called for heat. Once the
steam boiler reached 1.2 bar the temperature display began
it's rise.
Once it reached my set point of 203F, the heat light went
out. But, oh
no, the temperature display kept rising! The fluke display
kept rising
matching the readings from the controller. What could be
wrong? The
stock controller never rises above the set point! There must be
something wrong with the controller, I thought. I certainly
didn't
program it incorrectly and if I did it would have been Sean's
fault,
not mine (hehe). After verifying the programming was correct and
apologizing to Sean we decided to re-connect the stock
controller and
compare it's readings to that of the fluke. Our eyes were
opened! The
stock controller display would dip to 94 causing a call for
heat. At
this time, the fluke read 94C and then started to climb back
to 95C as
it should but alas, it kept rising all the way to 99C. That's
an 8F
temperature swing within the boiler but the stock controller's
display never rose above 95C! Based on this information, we
suspect
that AKO specially programmed the stock controller for Expobar
so that
it would never show readings above the set point which gives the
impression that the controller is doing a much better job at
controlling boiler temperature than it really is. The new
controller
doesn't do this. It truly shows the actual temperature,
whatever it
may be.
After watching many heating/cooling cycles on the stock
controller and
determining there is on average an 8F swing in boiler
temperature, I
re-connected the new controller and continued testing. Upon
watching
numerous heating/cooling cycles, I determined that, on average
it was
able to control boiler temperature to within a 4.5F range - ½ that
of the stock controller. I believe this is due to the
difference in
resolution between degrees F and degrees C as well as better
electronics, faster probes, and the ability to set offset in
tenths of
a degree.
How did all of this affect brew temperature variance and average?
Here's a comparison between the two controllers. First, let me
outline the testing parameters:
Warm Up Time: 2 hours
Tested only 1st shot of the day (this is because I only brew
one shot
in the morning then one at night)
Coffee used: vivace vita
Shot volume: 1.5 oz.
Shot time: 25-30 sec.
Tamp pressure: 40lbs.
Flush routine: 1.5 oz. flush, 1 minute to dose/tamp, 1.5 oz.
flush,
immediately pull shot.
Target Brew Temp: 203F
Stock Controller:
Brew Temperature Variance: 1.2F (readings taken from the 10
sec. on as
per Schomer)
Average Brew Temp off target: +- .8F
New Controller:
Brew Temperature Variance: .7F (readings taken from the 10
sec. on as
per Schomer)
Average Brew Temp off target: +- .2F
picture of a brew temp graph for the new controller is
available on the
brewtus group under user folders/Doug
It should be noted that the time in which you start the shot
within the
heating/cooling cycle will greatly affect average brew
temperature. If
you start the shot just as the controller heats up to the set
point you
will get the results seen above. However, if you start the
shot during
the cooling phase or just before the controller calls for
heat, your
average brew temperatures will be off as much as minus 2F.
Unfortunately, this is the Achilles heel of these controllers.
It would
take installing a PID controller to eliminate this problem.
The AKO
controllers are really just glorified thermostats. Their
operation is
analogous to a car approaching a stop sign at 60 MPH. It waits
until it
reaches the stop sign before applying the brakes causing sever
overshoot whereas a PID controller is analogous to that same
car gently
applying the brakes as it approaches and actually stops at the
stop
sign. Sigh.
In conclusion, I feel the new controller although falling way
short of
a PID controller, offers the following improvements over the stock
controller:
1. Displays 3 digit degrees F
2. Faster more accurate readings and response time
3. Ability to program offset in tenths of a degree
4. Offers improved temperature stability
Questions and comments are welcome. If enough people are
interested we
can put together a group buy. I will glady put together an
installation
manual for the group if there is enough interest.
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