Toaster Oven dimmer ?

[Sylvain Munaut]

Hello,

To try to approximate the temperature profile of a reflow oven, I'd like
to make a computer controlled dimmer for a toaster oven.

Does any one here as a schema / base where I can start from for the
Hipower part (digital and pc interface is ok). I found some dimmer
schema but they where all for light and a power of 500W max. Here, the
heating element is more like 2500W. Is it just a matter of putting a
bigger triac, that can handle that load ?


Thanks,


Sylvain

 

[Dave]

"Sylvain Munaut" <com.246tNt@tnt> wrote in message
news:42e9f836$0$11670$ba620e4c@news.skynet.be...

Hello,

To try to approximate the temperature profile of a reflow oven, I'd like
to make a computer controlled dimmer for a toaster oven.

Sounds interesting

Does any one here as a schema / base where I can start from for the
Hipower part (digital and pc interface is ok). I found some dimmer
schema but they where all for light and a power of 500W max. Here, the
heating element is more like 2500W. Is it just a matter of putting a
bigger triac, that can handle that load ?

Use a SSR (Solid State Relay). These come with opto isolated, logic level
inputs which can be safely driven by any micro processor.

Dave




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[martin griffith]

On Fri, 29 Jul 2005 11:35:00 +0200, in sci.electronics.design Sylvain
Munaut <com.246tNt@tnt> wrote:

Hello,

To try to approximate the temperature profile of a reflow oven, I'd like
to make a computer controlled dimmer for a toaster oven.

Does any one here as a schema / base where I can start from for the
Hipower part (digital and pc interface is ok). I found some dimmer
schema but they where all for light and a power of 500W max. Here, the
heating element is more like 2500W. Is it just a matter of putting a
bigger triac, that can handle that load ?


Thanks,


Sylvain
this was in circuit cellar

http://www.circuitcellar.com/library/print/0704/Lacoste_168/


martin

 

[Joerg]

Hello Martin,

this was in circuit cellar
http://www.circuitcellar.com/library/print/0704/Lacoste_168/

And the author can sometimes be found on this newsgroup as well as on
fr.sci.electronique.

To be honest I didn't even know that there were toaster ovens with
quartz top heaters. Guess I am barbequeing too much (ribs yesterday).

Regards, Joerg

http://www.analogconsultants.com

 

[Sylvain Munaut]

Joerg wrote:

Hello Martin,

this was in circuit cellar
http://www.circuitcellar.com/library/print/0704/Lacoste_168/

Yes, thanks.
I've seen similar article. But I was wondering if using a a dimmer to
for example be able to set the heaters to 50% of it's nominal power
would be better/worse than just turning it on/off bruptly.

To be honest I didn't even know that there were toaster ovens with
quartz top heaters.

Is it really necessary to have top quartz heaters ? I just did 3 stores
and none of them had quartz heater. They all had classical resistors
(either in S shape, or several straight line ).

Guess I am barbequeing too much (ribs yesterday).

I'm more a merguez type of guy



Sylvain

 

[martin griffith]

On Fri, 29 Jul 2005 11:42:33 GMT, in sci.electronics.design Joerg
<notthisjoergsch@removethispacbell.net> wrote:

Hello Martin,

this was in circuit cellar
http://www.circuitcellar.com/library/print/0704/Lacoste_168/

And the author can sometimes be found on this newsgroup as well as on
fr.sci.electronique.

To be honest I didn't even know that there were toaster ovens with
quartz top heaters. Guess I am barbequeing too much (ribs yesterday).

Regards, Joerg

http://www.analogconsultants.com
Hi Joerg

I've only just bought my first blender, ever, I dont even have a
microwave. It is not advisable to light a BBQ here, serious drought
problems/fires

I'll stick with Tapas in the local bars, less washing up


martin

 

[Mochuelo]

On Fri, 29 Jul 2005 11:35:00 +0200, Sylvain Munaut <com.246tNt@tnt>
wrote:

Hello,

To try to approximate the temperature profile of a reflow oven, I'd like
to make a computer controlled dimmer for a toaster oven.

Does any one here as a schema / base where I can start from for the
Hipower part (digital and pc interface is ok). I found some dimmer
schema but they where all for light and a power of 500W max. Here, the
heating element is more like 2500W. Is it just a matter of putting a
bigger triac, that can handle that load ?

That's an option. Another one is to use two MOSFETs in "anti-series."
Tie their sources together, and also their gates together. Effective
total switch between drain1 and drain2. Excite between gate and source
with Vgs > Vgs_th. The advantage of this over the TRIAC is that it
consumes nothing, from the excitation circuit, while in static
conditions. In your application, you have very few transitions, so
this makes sense.

Thanks,


Sylvain

 

[Rich Grise]

On Fri, 29 Jul 2005 16:21:15 +0200, Sylvain Munaut wrote:

Joerg wrote:
Hello Martin,

this was in circuit cellar
http://www.circuitcellar.com/library/print/0704/Lacoste_168/

Yes, thanks.
I've seen similar article. But I was wondering if using a a dimmer to
for example be able to set the heaters to 50% of it's nominal power
would be better/worse than just turning it on/off bruptly.

It's the same effect. The only difference is between the built-in
thermostat on the oven vs. the electronics to do the switching, well,
electronically. Or standing there watching the thermometer.

Although, I haven't used a toaster oven in quite some time - they
_do_ have a knob, don't they? As opposed to just an on-off switch?

To be honest I didn't even know that there were toaster ovens with
quartz top heaters.

Is it really necessary to have top quartz heaters ? I just did 3 stores
and none of them had quartz heater. They all had classical resistors
(either in S shape, or several straight line ).

I think a heater is pretty much a heater. I have no idea what's so
special about a "quartz heater", unless the envelope protects the
element from corrosion. Watts in == watts out, after all, and the
inefficiencies show up as heat anyway - what's the benefit to some
high-tech heating element? Marketing hype?

Thanks,
Rich

 

[martin griffith]

On Fri, 29 Jul 2005 15:51:27 GMT, in sci.electronics.design Rich Grise
<richgrise@example.net> wrote:

On Fri, 29 Jul 2005 16:21:15 +0200, Sylvain Munaut wrote:

Joerg wrote:
Hello Martin,

this was in circuit cellar
http://www.circuitcellar.com/library/print/0704/Lacoste_168/

Yes, thanks.
I've seen similar article. But I was wondering if using a a dimmer to
for example be able to set the heaters to 50% of it's nominal power
would be better/worse than just turning it on/off bruptly.

It's the same effect. The only difference is between the built-in
thermostat on the oven vs. the electronics to do the switching, well,
electronically. Or standing there watching the thermometer.

Although, I haven't used a toaster oven in quite some time - they
_do_ have a knob, don't they? As opposed to just an on-off switch?

To be honest I didn't even know that there were toaster ovens with
quartz top heaters.

Is it really necessary to have top quartz heaters ? I just did 3 stores
and none of them had quartz heater. They all had classical resistors
(either in S shape, or several straight line ).

I think a heater is pretty much a heater. I have no idea what's so
special about a "quartz heater", unless the envelope protects the
element from corrosion. Watts in == watts out, after all, and the
inefficiencies show up as heat anyway - what's the benefit to some
high-tech heating element? Marketing hype?

Thanks,
Rich
Could be the wavelength of the infra red,and absorbtion factors of the

solder gloop rather than just wattage.


martin

 

[Ben Bradley]

On Fri, 29 Jul 2005 11:35:00 +0200, Sylvain Munaut <com.246tNt@tnt>
wrote:

Hello,

To try to approximate the temperature profile of a reflow oven, I'd like
to make a computer controlled dimmer for a toaster oven.

Does any one here as a schema / base where I can start from for the
Hipower part (digital and pc interface is ok). I found some dimmer
schema but they where all for light and a power of 500W max. Here, the
heating element is more like 2500W. Is it just a matter of putting a
bigger triac, that can handle that load ?

There's a difference in heater control units and light dimmers.
Light dimmers use an SCR or triac that turns on at different places
during each half wave to get varying power and varying light.
(Electronic) Heater controls turn on and off at zero crossings, and
thus don't put a noise spike on the power line as dimmers generally
do.
I looked at the referenced Circuit Cellar reflow oven, it uses a
mechanical relay to control the heating element! That probably
produces spikes, but probably just one (or a few, depending on how
bouncy the contacts are) every couple of seconds or so, or however
fast it switches the relay.
Someone else mentioned a solid-state relay, and that sounds like
the solution, ISTR that some (or perhaps all nowadays?) only switch
off and on during zero crossing, and that's what you want to keep from
dumping spikes on the power line.

Thanks,


Sylvain

-----
http://www.mindspring.com/~benbradley

 

[Joerg]

Hello Sylvain,

I've seen similar article. But I was wondering if using a a dimmer to
for example be able to set the heaters to 50% of it's nominal power
would be better/worse than just turning it on/off bruptly.

The reaction time of a heater element is so slow that I'd guess it
doesn't matter. Except that a dimmer for such power levels would be
quite expensive. Small triacs are cheap because evey dimmer in the
hardwares store contains one. Not so for the big ones.

Is it really necessary to have top quartz heaters ? I just did 3 stores
and none of them had quartz heater. They all had classical resistors
(either in S shape, or several straight line ).

Email Robert Lacoste about it. There must be a reason why he ordered one
via the web for $150 where he probably could have gotten a regular oven
for $30 or so at Carrefour.

Guess I am barbequeing too much (ribs yesterday).

I'm more a merguez type of guy

AFAIK those have to be cooked in oil at the end. They say the same about
bratwurst which should be pre-cooked in beer. But we didn't find much of
a taste difference versus just slow cooking them on charcoal.

Regards, Joerg

http://www.analogconsultants.com

 

[Joerg]

Hello Martin,

I've only just bought my first blender, ever, I dont even have a
microwave. It is not advisable to light a BBQ here, serious drought
problems/fires

Same here but we do not use any fossil fuel products. The charcoal is
started in a "starter chinmney". Just a couple of crumpled newspaper
pages in the cavity underneath is enough, you just have to wait 1/2
hour. The typical American barbeque grill is a "Weber". It is a
completely enclosed round thing with adjustable vents on top and bottom.
Quite safe if you are careful.

I'll stick with Tapas in the local bars, less washing up

Tapas are more healthy, too. You aren't presented with a chock full
plate of food that in the end is consumed much too fast. Do they still
place the saucers on top of the beer or wine glasses?

So, are you permanently lving in Spain?

Regards, Joerg

http://www.analogconsultants.com

 

[dlharmon]

Sylvain Munaut wrote:

Hello,

To try to approximate the temperature profile of a reflow oven, I'd like
to make a computer controlled dimmer for a toaster oven.

Does any one here as a schema / base where I can start from for the
Hipower part (digital and pc interface is ok). I found some dimmer
schema but they where all for light and a power of 500W max. Here, the
heating element is more like 2500W. Is it just a matter of putting a
bigger triac, that can handle that load ?


Thanks,


Sylvain

I have done this with some success. I used a Sunbeam oven that cost $20
and had the quartz elements. The oven is somewhat slow heating (less
than 1 degree C per second and slows down the hotter it gets). I am
considering moving the bottom element to the top and/or purchasing a
second oven for more elments. I just used a relay to control it. That
is all it should take. I used a MAX6675 thermocouple to SPI converter
to measure temperature. The board I ran was a complete success
including the 1mm pitch BGA.
I simply used thermostatic control, and it was nearly perfect. Note
that the pink line is the goal temp, and it is covered up by the fuzzy
blue line (measured temp).


There are temp profile from the oven linked at:

http://dlharmon.com/smd.html

Darrell Harmon

 

[Sylvain Munaut]

dlharmon wrote:

Sylvain Munaut wrote:

Hello,

To try to approximate the temperature profile of a reflow oven, I'd like
to make a computer controlled dimmer for a toaster oven.


I have done this with some success. I used a Sunbeam oven that cost $20
and had the quartz elements. The oven is somewhat slow heating (less
than 1 degree C per second and slows down the hotter it gets). I am
considering moving the bottom element to the top and/or purchasing a
second oven for more elments. I just used a relay to control it. That
is all it should take. I used a MAX6675 thermocouple to SPI converter
to measure temperature. The board I ran was a complete success
including the 1mm pitch BGA.
I simply used thermostatic control, and it was nearly perfect. Note
that the pink line is the goal temp, and it is covered up by the fuzzy
blue line (measured temp).

Yes, I've seen that. Actually it's when I saw you successfully soldered
BGA that I decided to try it by myself

I've just bought a oven, it's not quart element, just 2 heating resitors
on the top and 2 heating resistors on the bottom. 1500W total power. The
inside looked exactly like
http://www.sparkfun.com/tutorial/ReflowToaster/reflow-toaster.htm

To do a quick heat speed test, I placed a thermocouple inside. However,
it was near the back panel, not really centered (it's a multimeter probe
so i inserted it trhu a screw hole). And at posteriori the real inside
temp must have been quite hotter than that.

It heats at about 1-1.5 °C at the start and at 0.2 °C/s when above
200°C. However these measure might be flawed see what follows.


As a quick test, I just took a PCB where the silk screen was failed and
where I did some solder test. I took some pads where there was a solder
"bubble" on the pad and applied flux, then some 0805 and 1206
components. Then I turned on the oven till I read 130 °C, maintain that
for 2 min, then heat up till 220°C and maintain that for 30 s. However
the temperature in there must have been higher as the pcb itself kindof
melted (the different layers separting themselves, bubble appearing
inside) Guess I have to get a better reading than that. The solders
looks ok though, even if the components and the pcb are near burnt


Sylvain

 

[dlharmon]

Sylvain Munaut wrote:

Yes, I've seen that. Actually it's when I saw you successfully soldered
BGA that I decided to try it by myself

I've just bought a oven, it's not quart element, just 2 heating resitors
on the top and 2 heating resistors on the bottom. 1500W total power. The
inside looked exactly like
http://www.sparkfun.com/tutorial/ReflowToaster/reflow-toaster.htm

To do a quick heat speed test, I placed a thermocouple inside. However,
it was near the back panel, not really centered (it's a multimeter probe
so i inserted it trhu a screw hole). And at posteriori the real inside
temp must have been quite hotter than that.

It heats at about 1-1.5 °C at the start and at 0.2 °C/s when above
200°C. However these measure might be flawed see what follows.


As a quick test, I just took a PCB where the silk screen was failed and
where I did some solder test. I took some pads where there was a solder
"bubble" on the pad and applied flux, then some 0805 and 1206
components. Then I turned on the oven till I read 130 °C, maintain that
for 2 min, then heat up till 220°C and maintain that for 30 s. However
the temperature in there must have been higher as the pcb itself kindof
melted (the different layers separting themselves, bubble appearing
inside) Guess I have to get a better reading than that. The solders
looks ok though, even if the components and the pcb are near burnt


Sylvain

I would say that you were way above 220 degrees C on the board that
seperated.

I have noticed that most of the heating takes place by infrared. If
the thermocoule was not in contact with the board, there could have
been large temperature differences. I saw a 50 C difference between a
piece of copperclad (very reflective of IR) and a board with green
soldermask in testing. I placed my thermocouple directly on top of the
board near the BGA.

Your heating speeds seem reasonable. Mine is about 2C/second at room
temperature and 0.5C/second at 200 C. Xilinx recommends ramping up to
the peak temperature at 2-3 degrees C per second if I remember
correctly. I believe I would be in that range with the second element
since the decrease in speed is probably due to the poor insulation of
the oven.

Darrell Harmon

 

[Joerg]

Hello Darrell,

Your heating speeds seem reasonable. Mine is about 2C/second at room
temperature and 0.5C/second at 200 C. Xilinx recommends ramping up to
the peak temperature at 2-3 degrees C per second if I remember
correctly. I believe I would be in that range with the second element
since the decrease in speed is probably due to the poor insulation of
the oven.

It could also be because of the large volume of the oven chamber versus
limited heater power. Just like it takes twice as long to heat a room of
twice the volume with a space heater of a given power, almost regardless
how good the house is insulated.

Unless you are talking about a different beast usually they design these
ovens so that one or two regular size chickens will fit. I don't know if
that would be safe: What if the oven were somehow modified to maybe a
quarter of its usual height?

Regards, Joerg

http://www.analogconsultants.com

 

[dlharmon]

Joerg wrote:

Hello Darrell,

Your heating speeds seem reasonable. Mine is about 2C/second at room
temperature and 0.5C/second at 200 C. Xilinx recommends ramping up to
the peak temperature at 2-3 degrees C per second if I remember
correctly. I believe I would be in that range with the second element
since the decrease in speed is probably due to the poor insulation of
the oven.

It could also be because of the large volume of the oven chamber versus
limited heater power. Just like it takes twice as long to heat a room of
twice the volume with a space heater of a given power, almost regardless
how good the house is insulated.

Unless you are talking about a different beast usually they design these
ovens so that one or two regular size chickens will fit. I don't know if
that would be safe: What if the oven were somehow modified to maybe a
quarter of its usual height?

Regards, Joerg

http://www.analogconsultants.com

Before I bought the toaster oven, I had thoughts of making a very small
reflow oven using 4 500W halogen bulbs.

I would try to raise the floor, but the heating element is a single
300mm long quartz tube, and I am afraid that I would not get even
heating. I don't think any chickens would fit in this toaster oven. It
was the smallest one the store had and I chose it for that reason. The
label says 1350 watts, and I assume that would be with both elements
on. I have been using just the top element (broil setting). The oven
has no insulation (just 2 layers of thin sheet metal). The outside gets
really hot.

Assuming I have 675 watts of power going in whenever the element is on,
I would estimate that I am losing about 500 watts of heat when the oven
is at 200 degrees C based on the difference in ramp rate. So I
effectively have about 200 watts going to heat the oven and its
contents. If I double the power to 1350W, I will still be losing about
500W, but 850W will be going to heat the oven which should result in a
ramp rate of around 3 degrees C per second. Maybe I will test that
theory out tommorrow if I have time.

Darrell Harmon

 

[Jeff]

"Rich Grise" <richgrise@example.net> wrote in message
newsan.2005.07.29.15.53.43.819921@example.net...

On Fri, 29 Jul 2005 16:21:15 +0200, Sylvain Munaut wrote:

Joerg wrote:
Hello Martin,

this was in circuit cellar
http://www.circuitcellar.com/library/print/0704/Lacoste_168/

Yes, thanks.
I've seen similar article. But I was wondering if using a a dimmer to
for example be able to set the heaters to 50% of it's nominal power
would be better/worse than just turning it on/off bruptly.

It's the same effect. The only difference is between the built-in
thermostat on the oven vs. the electronics to do the switching, well,
electronically. Or standing there watching the thermometer.

Although, I haven't used a toaster oven in quite some time - they
_do_ have a knob, don't they? As opposed to just an on-off switch?

To be honest I didn't even know that there were toaster ovens with
quartz top heaters.

Is it really necessary to have top quartz heaters ? I just did 3 stores
and none of them had quartz heater. They all had classical resistors
(either in S shape, or several straight line ).

I think a heater is pretty much a heater. I have no idea what's so
special about a "quartz heater", unless the envelope protects the
element from corrosion. Watts in == watts out, after all, and the
inefficiencies show up as heat anyway - what's the benefit to some
high-tech heating element? Marketing hype?

Thanks,
Rich

Quartz supposedly gives off more infrared heat, vs. convection heat. This
would allow for quicker thermal responses.

 

[Spehro Pefhany]

On Sat, 30 Jul 2005 14:21:52 GMT, the renowned "Jeff"
<antispam@hotmail.com> wrote:

"Rich Grise" <richgrise@example.net> wrote in message
newsan.2005.07.29.15.53.43.819921@example.net...
On Fri, 29 Jul 2005 16:21:15 +0200, Sylvain Munaut wrote:

Joerg wrote:
Hello Martin,

this was in circuit cellar
http://www.circuitcellar.com/library/print/0704/Lacoste_168/

Yes, thanks.
I've seen similar article. But I was wondering if using a a dimmer to
for example be able to set the heaters to 50% of it's nominal power
would be better/worse than just turning it on/off bruptly.

It's the same effect. The only difference is between the built-in
thermostat on the oven vs. the electronics to do the switching, well,
electronically. Or standing there watching the thermometer.

Although, I haven't used a toaster oven in quite some time - they
_do_ have a knob, don't they? As opposed to just an on-off switch?

To be honest I didn't even know that there were toaster ovens with
quartz top heaters.

Is it really necessary to have top quartz heaters ? I just did 3 stores
and none of them had quartz heater. They all had classical resistors
(either in S shape, or several straight line ).

I think a heater is pretty much a heater. I have no idea what's so
special about a "quartz heater", unless the envelope protects the
element from corrosion. Watts in == watts out, after all, and the
inefficiencies show up as heat anyway - what's the benefit to some
high-tech heating element? Marketing hype?

Thanks,
Rich


Quartz supposedly gives off more infrared heat, vs. convection heat. This
would allow for quicker thermal responses.

Unless the process is very tolerant of wide swings in temperature, you
can't control a quartz heater effectively with zero-voltage switched
time proportioning because of the fast response-- you have to use
something like phase control (which is normally considered
undesirable). </run-on sentence>


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com