Homebrew PCBs

DJ Delorie, you mentioned before you did your own temperature controller for your laminator. Did you do anything special to control the temperature? Did you use any control loop or just on/off monitor of the temperature. 

Thanks

Trev

"trevwhite74" <trevor.white100@...> writes:
> DJ Delorie, you mentioned before you did your own temperature
> controller for your laminator. Did you do anything special to
> control the temperature? Did you use any control loop or just on/off
> monitor of the temperature.

The thermocouple chip I used returns four samples per second, so I
just did a plain "less than=on/greater than=off" test, once per 0.25
seconds.  It keeps the heater within about 10F with a 10-30 second
cycle, which is fine for me.  Recall I'm sensing the heater temp, not
the roller temp.

I did put in a 60Hz sensor with appropriate timed delays to syncronize
with the zero crossings.  At the moment, I just use it to push the new
setting out, but I put it in in case I wanted to play with PID control
later.

Hi DJ Delorie. 

Thanks for the feedback. I am going to do one myself for a laminator. Those max chips are just cool. 

Trev


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

>
> 
> "trevwhite74" <trevor.white100@...> writes:
> > DJ Delorie, you mentioned before you did your own temperature
> > controller for your laminator. Did you do anything special to
> > control the temperature? Did you use any control loop or just on/off
> > monitor of the temperature.
> 
> The thermocouple chip I used returns four samples per second, so I
> just did a plain "less than=on/greater than=off" test, once per 0.25
> seconds.  It keeps the heater within about 10F with a 10-30 second
> cycle, which is fine for me.  Recall I'm sensing the heater temp, not
> the roller temp.
> 
> I did put in a 60Hz sensor with appropriate timed delays to syncronize
> with the zero crossings.  At the moment, I just use it to push the new
> setting out, but I put it in in case I wanted to play with PID control
> later.
>

If you are interested in the more economical version, this is it:
<http://s5.tinypic.com/9ghpxj.jpg>

Just a transistor, and a few resistors, and not a line of code in sight.

It uses the thermistor integral to the fuser unit, but a suitable
thermistor can be added to any laminator.

Initially I just threw this together in a junction box to try toner
transfer, but it works so well I never changed it.
(These days i would just cough up the $30 or less for an industrial
controller from ebay).

ST

On Fri, Mar 27, 2009 at 1:55 AM, trevwhite74
<trevor.white100@...> wrote:

> Hi DJ Delorie.
>
> Thanks for the feedback. I am going to do one myself for a laminator. Those max chips are just cool.
>
> Trev
>
>

Stefan Trethan <stefan_trethan@...> writes:
> If you are interested in the more economical version, this is it:
> <http://s5.tinypic.com/9ghpxj.jpg>

I thought about doing something like that.  The problem was, I needed
a specific temperature (the film says 240F), and had no way of
measuring the actual temperature in the laminator.  The advantage of
using a thermocouple with the MAX chip is that it tells me *actual*
temperature, in degrees.  No need to calibrate the dial - just turn it
until the right number shows up, and the chip keeps the laminator at
*that* temperature.

I had tried just hacking the temp sensor in the laminator by putting
things between it and the roller to make the rollers run hotter, but I
had no way of knowing if it was working or not.

Of course, my way cost me about $50 in parts :-P

Yes, i have several meters with thermocouple probes, so that was no problem.
For $50 you can probably get one of the chinese digital controllers on
ebay and a semiconductor relay.
(But then, programming does not cause you as much horrible pain as it
does for me......)

ST

On Fri, Mar 27, 2009 at 2:41 PM, DJ Delorie <dj@...> wrote:
>
> Stefan Trethan <stefan_trethan@...> writes:
>> If you are interested in the more economical version, this is it:
>> <http://s5.tinypic.com/9ghpxj.jpg>
>
> I thought about doing something like that.  The problem was, I needed
> a specific temperature (the film says 240F), and had no way of
> measuring the actual temperature in the laminator.  The advantage of
> using a thermocouple with the MAX chip is that it tells me *actual*
> temperature, in degrees.  No need to calibrate the dial - just turn it
> until the right number shows up, and the chip keeps the laminator at
> *that* temperature.
>
> I had tried just hacking the temp sensor in the laminator by putting
> things between it and the roller to make the rollers run hotter, but I
> had no way of knowing if it was working or not.
>
> Of course, my way cost me about $50 in parts :-P
>

Stefan Trethan <stefan_trethan@...> writes:
> For $50 you can probably get one of the chinese digital controllers on
> ebay and a semiconductor relay.

My usual response to these types of statements is "my way is more fun" :-)

> (But then, programming does not cause you as much horrible pain as it
> does for me......)

Since I write embedded development tools, yeah, the software side of
this stuff is easy for me.