heater control for curing oven

Good info, thanks.

This post brings up a couple of questions...

1. Do I need breather with a bladder (to allow the air to be forced
out)?
2. Is there any concern with vapors building up in the oven and
causing a fire?
3. Perhaps it would be a good idea to put 2 bars in the bladder and
then put the whole thing in a vacuum bag so that the mold only sees
approximately 1 bar? This would keep the fumes out of the oven too.
4. Can thermocouples be joined together to "average" without using
software?
5. What is a very affordable PID controller (preferably under $100)
that will allow the ramp rate (up and down) to be set?

Thanks again folks.

Joe

wrote:
Good info, thanks.


5. What is a very affordable PID controller (preferably under $100)
that will allow the ramp rate (up and down) to be set?

Thanks again folks.

Joe

Try e-bay item 7546821715. I have one which I have used a couple of
times and am satisfied with.

Dan, U.S. Air Force, retired

"Dan, U.S. Air Force, retired" wrote in message news:1KiYe.29212$dm.24132@lakeread03...
wrote:
Good info, thanks.


5. What is a very affordable PID controller (preferably under $100)
that will allow the ramp rate (up and down) to be set?

Thanks again folks.

Joe

Try e-bay item 7546821715. I have one which I have used a couple of times and am satisfied with.

Dan, U.S. Air Force, retired

47 bucks delivered with the thermocouple! Does it do PID? Heck of a deal it looks like...

..Blueskies. wrote:
"Dan, U.S. Air Force, retired" wrote in message news:1KiYe.29212$dm.24132@lakeread03...

wrote:

Good info, thanks.


5. What is a very affordable PID controller (preferably under $100)
that will allow the ramp rate (up and down) to be set?

Thanks again folks.

Joe


Try e-bay item 7546821715. I have one which I have used a couple of times and am satisfied with.

Dan, U.S. Air Force, retired


47 bucks delivered with the thermocouple! Does it do PID? Heck of a deal it looks like...


I'd be able to answer if I knew what PID is.

Dan, U.S. Air Force, retired

Dan,

Does this unit allow you to set the ramp both going up and coming down?
Does it work with a solid state relay? How easy are the directions to
follow (assuming I can't read Chinese!)?

PID is described in the message below.

Joe

wrote:
Dan,

Does this unit allow you to set the ramp both going up and coming down?
Does it work with a solid state relay? How easy are the directions to
follow (assuming I can't read Chinese!)?

PID is described in the message below.

Joe


It's a basic temperature controller. You set the temperature you
want, the internal relay closes turning on your heater, if the
thermocouple says it's too high the internal relay opens so it's
basically an accurate thermostat. Since it comes without instructions I
have no idea what the relay specs are so I drove another relay with it.

There are two vertical 5 pin barrier strips on the back. The left pin
out is: 1-ground, 2 and 3 - 110 VAC, 4 and 5 are relay out. The right
pin out is: 6 and 7 - alarm, 8 - NC, 9 and 10 are the thermocouple.

I haven't tried the alarm function so I haven't bothered to figure
out how to set it. The power requirement is 100 VAC 50 cycles but it
operated rather nicely on 60 cycle for the half hour I tested it.

I still haven't gotten around to building my li'l oven yet. One of
these days I'll get around to procrastinating.

Dan, U.S. Air Force, retired

On Wed, 21 Sep 2005 17:49:49 -0500, "Dan, U.S. Air Force, retired"
wrote:



47 bucks delivered with the thermocouple! Does it do PID? Heck of a deal it looks like...


I'd be able to answer if I knew what PID is.

Dan, U.S. Air Force, retired

in control system parlance PID is proportion, integral and derivative.

they are used when the state of the process being monitored cant be
directly measured but must be inferred or calculated as the integral
of some calculation. one that comes to mind is the inference of a flow
rate from the upstream pressure and downstream pressure differential
of a fluid flow through a known diameter aperture plate.

Stealth Pilot

Should I be considering this method in building my fuel tanks? It's my
understanding that the higher cure temp, the higher delaminating temp.
Or am I reading too much into this?
Lou

In article ,
Stealth Pilot wrote:



in control system parlance PID is proportion, integral and derivative.

they are used when the state of the process being monitored cant be
directly measured but must be inferred or calculated as the integral
of some calculation. one that comes to mind is the inference of a flow
rate from the upstream pressure and downstream pressure differential
of a fluid flow through a known diameter aperture plate.

Stealth Pilot

PID control algorithms may well be used in conjunction with indirect
process monitoring, but that isn't my understanding of what PID means.

PROPORTIONAL --

You want to heat a pot of water to 170 degrees F with an electric
heating element. If you turn off the burner at 170, the water temp will
coast to 200. So you decide to scale back the power, beginning at 150.
The difference between target temperature ("set point") and the
beginning of scaling back power is called the "proportioning band."
Typically, the power to the burner is cycled off and on. 9 seconds on, 1
second off. Then 8 seconds on, 2 seconds off, etc. Even when the
temperature is above the target, you still get a couple of seconds of ON
time and 8 seconds of OFF time, just to minimize PIO -- Pilot Induced
Oscillation.

Now, you've got less initial overshoot, and smaller oscillations around
the set point. (An ON/OFF controller is always shutting off too late and
coming back on too late, because it can't anticipate and correct for lag
time in the system.)

INTEGRAL --

But, proportioning controllers tend to stabilize below set point. How do
you fix that? With manual reset, or, automatic reset, calculated
mathematically as an integral. Integral compensates for droop before it
exists.

DERIVATIVE --

We're still stuck with that pesky initial overshoot, the largest
magnitude deviation from set point, before the oscillations dampen out
to an acceptable level. (Tempering of chocolate requires very minimal
deviation, and the process requires many hours. Overheating and then
cooling a chocolate bar destroys the temper, and thereby the texture, so
don't do it!) The derivative function, obviously, watches the RATE of
change as the process temperature enters the proportioning band and
begins to approach the set point. To anthropomorphize, "where am I,
where am I going, and how fast am I getting there, and how quickly can I
react?" You start pulling the power back on downwind, at the latest,
planning a carefully controlled deceleration to stall speed two inches
off the ground. As things change, you keep fine tuning things.

Sorry for waxing pedantic on this one.

"Smitty Two" wrote in message news
In article ,
Stealth Pilot wrote:


Sorry for waxing pedantic on this one.

Spoken (written) very clearly, no apologies needed....