[SS2S-Main] Re: temperature controller with arduino
- From: "Lampe, Mattias SLC CT PEK" <mattias.lampe@xxxxxxxxxxx>
- To: "sugarshot@xxxxxxxxxxxxx" <sugarshot@xxxxxxxxxxxxx>
- Date: Tue, 1 Jul 2014 10:15:41 +0800
Hi all,
regarding SSRs, I have some spare ones I can send to Vicente, if needed.
I don’t have much experience with thermal calculations and designs, but
regarding the use of hair dryers/heat guns my idea would have been to NOT put
the entire device into the oven – which indeed would cause some issues with the
overheat protection and possibly melt some plastic parts of the devices – but
to just use it to blow hot air through the chamber. The hair dryer itself would
stay outside the oven and suck in cold air.
This certainly is not a very energy efficient method, since the hot air you
blow into the oven will eventually have to come out at at the other end, and I
cannot tell how much power you’d need to reach the target temperature within
the desired time, but the targeted 100 degrees C don’t sound too challenging to
me. But I may be wrong. It wouldn’t cost much effort to do a rough test with a
hair dryer and a large cardboard box, though.
One question I am curious about: Is the temperature profile referring to the
air temperature, to the surface temperature, or to the core temperature of the
cured parts? The latter seems to make the most sense to me, but wouldn’t that
imply that very thick parts would “over-cure” on the surface? Or is the limited
thermal conductivity of the material already somehow accounted for by the
slopes of the temperature profile, i.e. considering the surface heats up before
the core does but also cools down before the core does?
Mattias
From: sugarshot-bounce@xxxxxxxxxxxxx [mailto:sugarshot-bounce@xxxxxxxxxxxxx] On
Behalf Of Tim young
Sent: Tuesday, July 01, 2014 2:01 AM
To: sugarshot@xxxxxxxxxxxxx
Subject: [SS2S-Main] Re: temperature controller with arduino
My best advice is to use the BCS-460. This will give you everything you
originally wanted in the controller.
If that's not possible your existing PID will work for providing the
temperature control. By control I mean it will sense, via your Type-K
thermocouple, the temperature at the "tip" of the probe & provide this signal
to the controller. The controller will provide an output signal to the heating
device. The PID feedback loop in the controller will monitor the sensed temp
compared to the set point temp and adjust the output so that you don't
radically overshoot the set point. It will then maintain the set point temp
within the accuracy of the heating "System". I don't know if your REX-C700 PID
has any built in programming abilities that would allow you to program a
temperature curve some of the low cost one do but most don't.
Your controller can not directly handle a large output amperage so the output
signal is normally wired to a SSR Solid State Relay. Most PID controllers can't
directly control the heater. You would also need to use SSR(s) with the
BCS-460.
The PID's signal will modulate the electric heating element. Most PID could
also use an electrical mechanical contactor (relay) but the this is not ideal
for several reasons. 35 years ago SSR were just starting improve in
reliability (you had a 50/50 chance of them lasting 1-year) but they were high
priced. Today's SSR's have low price & good reliability.
Since you only have 1 sense point with your existing PID ( the BCS-460 has 4)
you will not be able to sense both the oven temp and the product temp with the
same thermocouple. I expect that there will not be a point on the nosecone
where you could insert the tip of the thermocouple into the construction to
sense it's temperature during the curing process. I would recommend that you
make some separate pieces that are representative of the construction that you
could insert the tip of the thermocouple. While this will not be an exact
indication of the temperature of the nosecone it will be close enough. Again
sensing the oven air temperature will not be sufficient to properly monitor the
temperature of the nosecone.
If you plan on using a hair dryer (or any consumer heater device) you will
probably need to remove the high temperature cut-off device. Also the fan
motors in these devices expect to see 100% ambient (cool) air, not recycled
heated air. Normally in ovens the fan motors are located outside of the heated
space with only the fan blade or wheel actually seeing the heated air.
Convection ovens rely upon high velocity air (high hundreds to thousands of
feet per minute velocity) to both maintain uniform oven temperature & to
eliminate the insulating boundary layer of air at the surface of the part.
When this boundary layer is eliminated the thermal energy in the air is
transferred to the part much more efficiently. Therefore the air temperature
in the oven needent be a great deal higher then the desired temperature of the
part.
Unless you plan on doing many curing runs it may be worth a few phone calls or
emails to local Universities or Business to see if they will donate some oven
time to this project.
Solid State Relay
SSR-40DA 40A /250V W I/O 3-32VDC/24-380VAC & Heat Sink
US $8.73
http://www.ebay.com/itm/Solid-State-Relay-SSR-40DA-40A-250V-W-I-O-3-32VDC-24-380VAC-Heat-Sink-/330924166119?pt=LH_DefaultDomain_0&hash=item4d0c9e0be7
On Mon, Jun 30, 2014 at 7:08 AM, James Fackert
<jimfackert@xxxxxxxxx<mailto:jimfackert@xxxxxxxxx>> wrote:
mine too. an hour or two learning to program a $50 temp controller (maybe $100
with multiple ramps and usb with pc based programmer )
is much cheaper than the hours and learning curve to program and to properly
interface an arduino that will cost at least $100 with box and interface
circuitry.
jim fackert
On Jun 30, 2014 9:17 AM, "Vicente Alvero Zambrano"
<vicente_alvero_14@xxxxxxxxxxx<mailto:vicente_alvero_14@xxxxxxxxxxx>> wrote:
Your opinion is to use the existing PID device?
> Subject: [SS2S-Main] Re: temperature controller with arduino
> From: waaslandwolf@xxxxxxxxx<mailto:waaslandwolf@xxxxxxxxx>
> Date: Mon, 30 Jun 2014 14:21:03 +0200
> To: sugarshot@xxxxxxxxxxxxx<mailto:sugarshot@xxxxxxxxxxxxx>
>
> I agree with Peter. Trying to save a mere 180$ by developing a solution that
> already exists isn't good use of resources.
>
> > Op 30-jun.-2014 om 00:52 heeft Peter Johansson
> > <rockets4kids@xxxxxxxxx<mailto:rockets4kids@xxxxxxxxx>> het volgende
> > geschreven:
> >
> > On Sun, Jun 29, 2014 at 6:36 PM, Vicente Alvero Zambrano
> > <vicente_alvero_14@xxxxxxxxxxx<mailto:vicente_alvero_14@xxxxxxxxxxx>> wrote:
> >
> >> My idea is to use an old oven heater like the picture.
> >> With respect to the PID controller, maybe it is cheaper to do it manually,
> >> without writing code.
> >
> > One option to consider -- and an advantage to going with a homebrew
> > solution -- is to simply read a configuration file containing the
> > temperature profile and PID tunings over over the serial port.
> >
> > This way you get the maximal possible control with the minimal
> > hardware cost and minimal software development time.
> >
> > -p.
> >
>
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