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New lamp dimmer application?

R

Rich Grise

Jan 1, 1970
0
Well, I'm not looking for reasons why I shouldn't do it, but how to do
it.

A lamp dimmer would work, if you could figure out how to add some
temperature feedback, like a thermocouple or using the element
itself in a bridge, there are lots of possibilities.

But if the lamp dimmer is rated for as much or more power than
the element, then there's no problem, other than temp. control,
as I said.

Have Fun!
Rich
 
D

default

Jan 1, 1970
0
I'd worry about 2 things..

1)lots of EMI generated from 50 Amp pulses floating around

2) if the triac shorts your burnner will be on full tilt and may be
dangerous if you are not there, may want to include a mechanical
overtemp saftey device. The triac could decide to short even when
the burner is not in use when you are not home etc......

Maybe triac + mechanical overtemp saftey + mechanical on/off


The other failure mode I have seen is that the burner shorts to its
outer shell and this is very bad becasue you can't turn it off
because the burner stays activated by one side of the 240 line unless
you have both sides of the line switched...

take care

Mark

Thanks

The EMI seems to be nothing . . . but a few years ago I found the
range burners were causing my computer modem to slow way down due to
EMI. Took me years to figure out the stove was causing the problem .
.. . but I built a common mode filter for the incoming power (all 20+
amps or so). The filter is still in there.

It wouldn't be the first time the mechanical range controls shorted
and caused the burner to stay full on, so the triac is no worse in
that respect.

The idea that the triac, just sitting there, could decide to short has
me worried too. I have a lamp dimmer in my bedroom that is one of
those push on/off. I leave it on, and just turn it down all the way
and it hasn't shorted in 20 years.

But there's more to lose if the range shorts so I want a double
make/break switch for that.
--
 
D

default

Jan 1, 1970
0
A lamp dimmer would work, if you could figure out how to add some
temperature feedback, like a thermocouple or using the element
itself in a bridge, there are lots of possibilities.

But if the lamp dimmer is rated for as much or more power than
the element, then there's no problem, other than temp. control,
as I said.

Have Fun!
Rich
The silly "infinite control" they use for the stove really only
manages to sense the ambient temperature and that is iffy at best.
Bimetallic switch with a little heater by it is all the switch is -
there is no feedback to the range element. At best, it could sense
the temperature inside the enclosure and that might cause it to change
calibration.

There are some stoves that do sense range element heat and regulate
that, but mine doesn't.


--
 
J

James Sweet

Jan 1, 1970
0
The EMI seems to be nothing . . . but a few years ago I found the
range burners were causing my computer modem to slow way down due to
EMI. Took me years to figure out the stove was causing the problem .
. . but I built a common mode filter for the incoming power (all 20+
amps or so). The filter is still in there.

It wouldn't be the first time the mechanical range controls shorted
and caused the burner to stay full on, so the triac is no worse in
that respect.

The idea that the triac, just sitting there, could decide to short has
me worried too. I have a lamp dimmer in my bedroom that is one of
those push on/off. I leave it on, and just turn it down all the way
and it hasn't shorted in 20 years.

But there's more to lose if the range shorts so I want a double
make/break switch for that.
--

The mechanical controls have no temperature feedback either, it's all open
loop.

You'll definitely want a mechanical power switch prior to the triac that
switches both sides.
 
R

Ross Herbert

Jan 1, 1970
0
:On Mon, 04 Feb 2008 14:03:41 -0500, default wrote:
:
:> On Mon, 04 Feb 2008 18:18:50 GMT, Ecnerwal
:>
:>>In article <[email protected]>,
:>>
:>>> The range is old and I use it a lot - cooking and beer making are
:>>> hobbies. That last can be hard on ranges.
:>>
:>>As it happens, I make beer on mine. Invested in a "canning element" 13
:>>years ago, put a 10 gallon pot on there and boil 8 gallons or so of wort
:>>down to 5, no problems with the range at all in 13 years. Catching the
:>>drips the exhaust fan can't keep up with and cleaning everything to suit
:>>me before I get started is more of a problem. The range, and the range
:>>controls, have had no trouble at all with this...
:>
:> Well, I'm not looking for reasons why I shouldn't do it, but how to do
:> it.
:
:A lamp dimmer would work, if you could figure out how to add some
:temperature feedback, like a thermocouple or using the element
:itself in a bridge, there are lots of possibilities.
:
:But if the lamp dimmer is rated for as much or more power than
:the element, then there's no problem, other than temp. control,
:as I said.
:

I don't think it will need temperature feedback at all. It would simply work the
same as it would in controlling lamp brightness when used as a dimmer, ie. time
proportional power control. It only needs temp feedback if you want the temp to
be controlled to agree with a dialled temp setting. If the scale is marked
simply 1 - 10 for example it doesn't really matter whether there is feedback or
not - it is simply an arbitrary power setting determined by the potentiometer.

Have a look at the NXP app note in my post down the bottom of the thread and
then look at (p.545, 546) and fig.14 and you will see that the lamp dimmer would
work in the same manner, just without the zero crossing triggering.
 
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