Homebrew PCBs

Anyone hack digital temperature control into a laminator?  My GBC 9"
laminator seems too cool for toner transfer and too hot for photofilm.

I'm pondering adding something to mine to let me control and monitor
the temperature more accurately, using a K thermocouple where the old
temperature switch is and a triac to power the heater.  Add an MCU,
LCD, potentiometer, and external enclosure...

Anyway, anyone done this before?  Any gotchas I should be aware of?

Or you could simply use a thermistor, pot, transistor, and solid state
relay, throw that together and be done with it. If you think about it,
there really is no need for rocket science here.

But if you want to throw more processing power at it than they
required for the moon landings, be my guest. I know you like to play
with software so it probably doesn't pain you as much as me.

ST

On Wed, Dec 10, 2008 at 3:32 AM, DJ Delorie <dj@...> wrote:
>
> Anyone hack digital temperature control into a laminator?  My GBC 9"
> laminator seems too cool for toner transfer and too hot for photofilm.
>
> I'm pondering adding something to mine to let me control and monitor
> the temperature more accurately, using a K thermocouple where the old
> temperature switch is and a triac to power the heater.  Add an MCU,
> LCD, potentiometer, and external enclosure...
>
> Anyway, anyone done this before?  Any gotchas I should be aware of?
>

"Stefan Trethan" <stefan_trethan@...> writes:
> Or you could simply use a thermistor, pot, transistor, and solid state
> relay, throw that together and be done with it. If you think about it,
> there really is no need for rocket science here.

What's the working range for thermistors?

I was thinking of using a MAX6675 chip, which goes from type K to SPI
readout of degrees directly, with no extra math or hardware needed.
An R8C MCU with an ADC pin reads the pot, and the LCD displays the set
point and the roller temp in actual degrees (rather than just 0..10 :)

I figure for $50 in parts (including power supply module) it lets me
know it's set to the right temperature, something I see only in
laminators costing hundreds of dollars.  My thought is that I can set
the desired temperature to a specific setting according to the specs
of whatever I'm laminating, and know when it's at that temperature.

> I know you like to play with software so it probably doesn't pain
> you as much as me.

There is that :-)

If you plan to spend money, you could also get one of ebay #
250337695389 (Or any other commercial temperature controller, used one
are cheaper as long as you get the right TC interface.).
I've used a similar controller for a SMD hotplate, and it works pretty well.

I've seen the MAX6675, and if one feels inclined to bother with the
SPI it looks nice, but personally i wish someone would make cheaper
analog interfaces (thermocouple to mV).
Analog devices makes them (forgot the number), but they are pretty expensive.

Anyway, everything will work. I chose the cheap solution with the
least number of parts for my laminator and it works fine, but there
are definite advantages to having a readout of actual temperature for
sure. Personally i would avoid the microcontroller route as long as
possible.

ST

On Wed, Dec 10, 2008 at 4:18 PM, DJ Delorie <dj@...> wrote:
>
> "Stefan Trethan" <stefan_trethan@...> writes:
>> Or you could simply use a thermistor, pot, transistor, and solid state
>> relay, throw that together and be done with it. If you think about it,
>> there really is no need for rocket science here.
>
> What's the working range for thermistors?
>
> I was thinking of using a MAX6675 chip, which goes from type K to SPI
> readout of degrees directly, with no extra math or hardware needed.
> An R8C MCU with an ADC pin reads the pot, and the LCD displays the set
> point and the roller temp in actual degrees (rather than just 0..10 :)
>
> I figure for $50 in parts (including power supply module) it lets me
> know it's set to the right temperature, something I see only in
> laminators costing hundreds of dollars.  My thought is that I can set
> the desired temperature to a specific setting according to the specs
> of whatever I'm laminating, and know when it's at that temperature.
>
>> I know you like to play with software so it probably doesn't pain
>> you as much as me.
>
> There is that :-)
>
> ------------------------------------
>
> Be sure to visit the group home and check for new Links, Files, and Photos:
> http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
>
>
>
>

--- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:
>
> 
> Anyone hack digital temperature control into a laminator?  My GBC 9"
> laminator seems too cool for toner transfer and too hot for photofilm.
> 
> I'm pondering adding something to mine to let me control and monitor
> the temperature more accurately, using a K thermocouple where the old
> temperature switch is and a triac to power the heater.  Add an MCU,
> LCD, potentiometer, and external enclosure...
> 
> Anyway, anyone done this before?  Any gotchas I should be aware of?
>


Personally, I love this project as I seem to want to MCU everything I see!

One advantage to a MCU control would be precision.  With a static
temperature sensor the heater would turn fully on till it reaches the
set point + hysteresis and then turn fully off till the temperature
drops below the set point - hysteresis.  This means the temperature
actually swings, sometimes this is very little sometimes this is a
lot, above and below the set point.

With an MCU you could implement a Proportional Integral Derivative
(PID) algorithm and apply a PWM signal to the Triac giving very fine
and nearly linear (depending upon the PWM frequency) power control to
the heater element.

Using the SPI thermocouple interface would eliminate the need for an
MCU with an ADC as well as the commensurate fussy analog signal
conditioning.  If you wanted to save even more cost you could replace
the LCD with three 7-segment LED displays and replace the POT with two
switches, one up one down.


I don't know what your MCU background is so please forgive me.  The
math for a good PID control is a bit complex for a little 8-bit MCU
but well within reach.  I've done several 0.18 degree per step Brushed
DC Servo Motors with all digital PID positioning on 8-bit mid-grade
PICMIcro MCU's with 2kHz+ update rates.

I would recommend, as a starting point, the PIC16F677 MCU from
microchip.  It is a 20 pin device, has ample program space, RAM, and
EEPROM storage as well as an internal 8MHz clock including a hardware
SPI interface. The cost is under $1.50 so that makes it nice.  I like
microchip because of the huge community of hobbyists and the large
amount of development software available for little to no cost.

Here is a link regarding 7-Segment LED Displays and how to drive them
with an MCU...

http://www.melabs.com/resources/articles/ledart.htm

Hope you give it more thought, MCU projects really are fun.

Aaron

--- In Homebrew_PCBs@yahoogroups.com, "demolitron" <ahardinger@...> wrote:
>
> --- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@> wrote:
> >
> > 
> > Anyone hack digital temperature control into a laminator?  My GBC 9"
> > laminator seems too cool for toner transfer and too hot for photofilm.
> > 
> > I'm pondering adding something to mine to let me control and monitor
> > the temperature more accurately, using a K thermocouple where the old
> > temperature switch is and a triac to power the heater.  Add an MCU,
> > LCD, potentiometer, and external enclosure...
> > 
> > Anyway, anyone done this before?  Any gotchas I should be aware of?
> >
> 
> 
> Personally, I love this project as I seem to want to MCU everything
I see!
> 
> One advantage to a MCU control would be precision.  With a static
> temperature sensor the heater would turn fully on till it reaches the
> set point + hysteresis and then turn fully off till the temperature
> drops below the set point - hysteresis.  This means the temperature
> actually swings, sometimes this is very little sometimes this is a
> lot, above and below the set point.
> 
> With an MCU you could implement a Proportional Integral Derivative
> (PID) algorithm and apply a PWM signal to the Triac giving very fine
> and nearly linear (depending upon the PWM frequency) power control to
> the heater element.
> 
> Using the SPI thermocouple interface would eliminate the need for an
> MCU with an ADC as well as the commensurate fussy analog signal
> conditioning.  If you wanted to save even more cost you could replace
> the LCD with three 7-segment LED displays and replace the POT with two
> switches, one up one down.
> 
> 
> I don't know what your MCU background is so please forgive me.  The
> math for a good PID control is a bit complex for a little 8-bit MCU
> but well within reach.  I've done several 0.18 degree per step Brushed
> DC Servo Motors with all digital PID positioning on 8-bit mid-grade
> PICMIcro MCU's with 2kHz+ update rates.
> 
> I would recommend, as a starting point, the PIC16F677 MCU from
> microchip.  It is a 20 pin device, has ample program space, RAM, and
> EEPROM storage as well as an internal 8MHz clock including a hardware
> SPI interface. The cost is under $1.50 so that makes it nice.  I like
> microchip because of the huge community of hobbyists and the large
> amount of development software available for little to no cost.
> 
> Here is a link regarding 7-Segment LED Displays and how to drive them
> with an MCU...
> 
> http://www.melabs.com/resources/articles/ledart.htm
> 
> Hope you give it more thought, MCU projects really are fun.
> 
> Aaron
>

Here is a link regarding the interfacing of Thermocouples directly to
the MCU, this could also be used to reduce the cost... 

http://ww1.microchip.com/downloads/en/AppNotes/00844a.pdf

"Stefan Trethan" <stefan_trethan@...> writes:

> I've seen the MAX6675, and if one feels inclined to bother with the
> SPI it looks nice, but personally i wish someone would make cheaper
> analog interfaces (thermocouple to mV).

The DS2762 is a bit cheaper, but still not "cheap".

I wonder if red's reflow oven controler couldn’t be adapted (in fact, I'm
pretty sure it will work)
http://www.thesiliconhorizon.com/reflow.htm
60$ apiece... just add a TC and a static relay. The temperature readout can
be done via the windows interface of your computer, or, in "stand alone"
version, with an I2C driven lcd/keyboard.
The firmware is not "open sourced" but delivered freely by the author to
whom may ask for it. 

Mark

"demolitron" <ahardinger@...> writes:
> Personally, I love this project as I seem to want to MCU everything I see!

Well, it will show up on my web site eventually.

> With an MCU you could implement a Proportional Integral Derivative
> (PID) algorithm and apply a PWM signal to the Triac giving very fine
> and nearly linear (depending upon the PWM frequency) power control to
> the heater element.

Would I need a 60hz sync signal for this?  Or can it run much slower
than that?

> Using the SPI thermocouple interface would eliminate the need for an
> MCU with an ADC

Need that for the potentiometer reading anyway, and most mcu's come
with adcs - at least, small ones that are "good enough" for a pot
reading.

> as well as the commensurate fussy analog signal conditioning.

Agreed :-)

> If you wanted to save even more cost you could replace the LCD with
> three 7-segment LED displays and replace the POT with two switches,
> one up one down.

The LCD is only $8.30 and I have pots in my junk boxes.  Using an LCD
means I can choose an MCU with fewer pins (less $$) and need a smaller
power supply.

> I don't know what your MCU background is so please forgive me.

I work for Red Hat writing embedded compilers.

> The math for a good PID control is a bit complex for a little 8-bit
> MCU but well within reach.

I tend to use the Renesas R8C chips, which are 16 bit.  I have a spare
R8C/27 from a past project, which has plenty of ram and flash.  20 MHz
clock, 10 bit adc, etc.  32 pins.  Not the cheapest of their chips -
$5.20 - but I already had it, and I've used them for lots of projects
so I have all the tools I need.  It also runs at 3.3v or 5v which
comes in handy.

> ST wrote:
> <SNIP>
> Analog devices makes them (forgot the number), but
> they are pretty expensive.
> <SNIP>

AD595

Came in ceramic dip and plastic dip.

The ceramic ones where expensive.

If I am building one off things I go for the
maxim part.  $10 of chip verus 30 minutes of
my time to do it another way.

>> demolitron wrote:
>> <SNIP>>
>> With an MCU you could implement a Proportional
> Integral Derivative (PID) algorithm and apply
>> a PWM signal to the Triac giving very fine
>> and nearly linear (depending upon the PWM
> frequency) power control to the heater element.

> DJ wrote:
> Would I need a 60hz sync signal for this?  Or
> can it run much slower than that?

Detect the Zero crossing and then trigger an
SCR/Triac a proprtional amount beind the zero
crossing.  This option is only suitable for
small resistive loads (like a laminator)

or

Full Wave rectify the AC (No need for filter
caps) then use a FET at what ever (high) PWM
freq you like.  This method is only good for
things like resistive loads that don't care
that it is now 110/240V DC rather than 110/240V
AC.

or

Detect the zero crossing and turn on/off for
full cycles for a proportional amount of
50/60Hz cycles.  Your on/off cycle time will
have a minimum "legal" amount of time.

I've read many of the responses to this initial post, but decided to 
reply to this first post to address what I see as something that 
needs to be looked into - before hacking your GBC-91 laminator.

I use a GBC "Heatseal", model-200 to do toner transfer when 
fabricating my printed circuit boards.  This GBC model has plenty of 
heat to produce excellent toner transfer.

The concern that I have is that the GBC-9 may not be able to produce 
the required heat to properly transfer the toner from the paper to 
the copper-clad.

If this is the case, hacking a temperature controller into the GBC-9 
won't provide any benefit toward good quality toner transfer.  If the 
heat content isn't there, no amount of control or precision will 
increase the heat content of the heating elements.  Too small, is 
simply too small.

I'd hate to see you spend unnecessary time and money on a project 
that might otherwise be an effort of futility.

Before I would spend any time on a hack for an external temperature 
controller, I'd look inside the GBC-9 and see if there is an 
adjustment on the thermostat controlling the heating element.  If 
there is an adjustment on the internal theromastat, you might be able 
to raise the operating temperature a bit to acquire better toner 
transfer.  Then you can move forward with the controller hack - after 
you are sure that the heating elements can, in fact generate the 
neccessary heat content.

At a minimum, you could examine the heating elements and determine 
the wattage that is being used in the thing.  There might even be a 
ballast resistor in series with the heating elements that could be 
reduced in value to push the operating temperature up a bit.

But if the heating elements won't deliver the heat content, hacking a 
controller won't provide any benefit.

I hope this helps you a little, before you spend time & money that 
could be used to achieve your goal by other more practical methods.

Have a great holiday season.

--- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:
>
> 
> Anyone hack digital temperature control into a laminator?  My GBC 9"
> laminator seems too cool for toner transfer and too hot for 
photofilm.
> 
> I'm pondering adding something to mine to let me control and monitor
> the temperature more accurately, using a K thermocouple where the 
old

> temperature switch is and a triac to power the heater.  Add an MCU,
> LCD, potentiometer, and external enclosure...
> 
> Anyway, anyone done this before?  Any gotchas I should be aware of?
>

"Andrew" <andrewm1973@...> writes:
> Detect the zero crossing and ...

Ok, I'll add a zero crossing detector ;-)

"Carl W. Livingston" <microcarl@...> writes:
> The concern that I have is that the GBC-9 may not be able to produce
> the required heat to properly transfer the toner from the paper to
> the copper-clad.

It does.  My current problem is that it's *too* hot for photofilm - I
end up destroying the film instead of laminating it.  I need to cool
it down a little.

> Before I would spend any time on a hack for an external temperature
> controller, I'd look inside the GBC-9 and see if there is an
> adjustment on the thermostat controlling the heating element.

Nope.  I did take it off and put a thin wire under it to reduce it's
thermal footprint - i.e. make it a little hotter.

My GBC 330 laminator has an analogue controller with a temperature
adjust pot on the back. The max temp was a bit low for toner transfer,
so I checked inside, and sure enough, there was a trimmer to adjust
the max temperature..

I just took the cover off and twiddled the trimmer and it now does
toner transfer, film, and anything else needed.

I can't imagine any other laminator working better.

OK so yours is probably different, but check inside first to see what
is controlling the temp.

Chris

C--- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:

>
> 
> Anyone hack digital temperature control into a laminator?  My GBC 9"
> laminator seems too cool for toner transfer and too hot for photofilm.
> 
> I'm pondering adding something to mine to let me control and monitor
> the temperature more accurately, using a K thermocouple where the old
> temperature switch is and a triac to power the heater.  Add an MCU,
> LCD, potentiometer, and external enclosure...
> 
> Anyway, anyone done this before?  Any gotchas I should be aware of?
>

"Chris Horne" <chris@...> writes:
> OK so yours is probably different, but check inside first to see what
> is controlling the temp.

The 9" has a simple temperature-sensitive switch, probably a bi-metal
type.  I looked up the part number at one point, but I don't remember
what the setpoint temperature is.

I have the GBC 9 inch laminator.  It isn't hot enough for toner
transfer so I just run the sandwich through multiple times.  That's a
lot less work than modifying the temperature controls.

--- In Homebrew_PCBs@...m, DJ Delorie <dj@...> wrote:

>
> 
> Anyone hack digital temperature control into a laminator?  My GBC 9"
> laminator seems too cool for toner transfer and too hot for photofilm.
> 
> I'm pondering adding something to mine to let me control and monitor
> the temperature more accurately, using a K thermocouple where the old
> temperature switch is and a triac to power the heater.  Add an MCU,
> LCD, potentiometer, and external enclosure...
> 
> Anyway, anyone done this before?  Any gotchas I should be aware of?
>

I just found the GBC H310 for about $54.69USD from Amazon. Some places wanted over double that. I've been using an iron for many years now, but the GBC H310 price was under my pain threshold and it's for a 12" wide model in case I go nuts and start making huge boards or multiples of a single board. Hopefully the temp adjust is similarly easy.

Mike



--- In Homebrew_PCBs@yahoogroups.com, "Chris Horne" <chris@...> wrote:

>
> My GBC 330 laminator has an analogue controller with a temperature
> adjust pot on the back. The max temp was a bit low for toner transfer,
> so I checked inside, and sure enough, there was a trimmer to adjust
> the max temperature..
> 
> I just took the cover off and twiddled the trimmer and it now does
> toner transfer, film, and anything else needed.
> 
> I can't imagine any other laminator working better.
> 
> OK so yours is probably different, but check inside first to see what
> is controlling the temp.
> 
> Chris
> 
> C--- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@> wrote:
> >
> > 
> > Anyone hack digital temperature control into a laminator?  My GBC 9"
> > laminator seems too cool for toner transfer and too hot for photofilm.
> > 
> > I'm pondering adding something to mine to let me control and monitor
> > the temperature more accurately, using a K thermocouple where the old
> > temperature switch is and a triac to power the heater.  Add an MCU,
> > LCD, potentiometer, and external enclosure...
> > 
> > Anyway, anyone done this before?  Any gotchas I should be aware of?
> >
>

I have the GBC Personal Laminator (9" size) that sells on ebay for $25 shipped - great little thing.  I think this is the same laminator sold by Pulsar on their website - photos look exactly the same.

It is temperature controlled by two bi-metal switches for the low (3mil) and high (5mil) settings. These two settings provide temperature to able 325°F temperature.  By jumpering the low setting the temperature now reaches well over 400°F so the heat is there.

I use a type "J" thermocouple wired to a mV meter to monitor the temperature.  I sure would like a controller with LCD display, but now I just heat up, run the board thru 3 or 4 times while watching the temperature. if gets a bit hot, just switch to the 5mil setting while it cools off a bit. The deadband in the thermal switches is 40°F or more.

I'll watch this thread for good (cheap:) ideas.

73 de Ken H> 

--- In Homebrew_PCBs@yahoogroups.com, "bob_ledoux" <bobledoux@...> wrote:

>
> I have the GBC 9 inch laminator.  It isn't hot enough for toner
> transfer so I just run the sandwich through multiple times.  That's a
> lot less work than modifying the temperature controls.
> 
> --- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@> wrote:
> >
> > 
> > Anyone hack digital temperature control into a laminator?  My GBC 9"
> > laminator seems too cool for toner transfer and too hot for photofilm.
> > 
> > I'm pondering adding something to mine to let me control and monitor
> > the temperature more accurately, using a K thermocouple where the old
> > temperature switch is and a triac to power the heater.  Add an MCU,
> > LCD, potentiometer, and external enclosure...
> > 
> > Anyway, anyone done this before?  Any gotchas I should be aware of?
> >
>