Is there a better way to do this?

[default]

I've got some 4KW 240 volt lamp dimmers from China.

What I want is a cheap electric range current regulator. (For safety
I plan to replace the potentiometers with switched ones and add dual
pole contactor - so "off" really is off)

The controls I'm replacing use a bimetallic switch with an extra
contact to switch off both sides of the 240 line in the off position
via a cam on the rotating part.

It would be cool and useful if I could also add a dual color LED to
show the approximate power setting from across the room. My only idea
so far is to treat it like a resistance divider with the common leg of
the LED tied to the junction between the dimmer and heating element
connection. I would use capacitive reactance to lower the voltage and
a diode so the LED isn't reverse biased.

Presumably this should give a relatively smooth transition from green
to red as the control calls for more power.

Does this sound like it aught to work? Is there a better way?

(Horsing the range in and out is no fun. Controls are due to arrive
today..)

 

[George Herold]

On Friday, May 8, 2015 at 8:31:49 AM UTC-4, default wrote:

I've got some 4KW 240 volt lamp dimmers from China.

What I want is a cheap electric range current regulator. (For safety
I plan to replace the potentiometers with switched ones and add dual
pole contactor - so "off" really is off)

The controls I'm replacing use a bimetallic switch with an extra
contact to switch off both sides of the 240 line in the off position
via a cam on the rotating part.

It would be cool and useful if I could also add a dual color LED to
show the approximate power setting from across the room. My only idea
so far is to treat it like a resistance divider with the common leg of
the LED tied to the junction between the dimmer and heating element
connection. I would use capacitive reactance to lower the voltage and
a diode so the LED isn't reverse biased.

Presumably this should give a relatively smooth transition from green
to red as the control calls for more power.

Does this sound like it aught to work? Is there a better way?

(Horsing the range in and out is no fun. Controls are due to arrive
today..)

Is your question about running the stove with lamp dimmers,
or how to do the led's?

George H.

 

[default]

On Fri, 8 May 2015 09:34:19 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

On Friday, May 8, 2015 at 8:31:49 AM UTC-4, default wrote:
I've got some 4KW 240 volt lamp dimmers from China.

What I want is a cheap electric range current regulator. (For safety
I plan to replace the potentiometers with switched ones and add dual
pole contactor - so "off" really is off)

The controls I'm replacing use a bimetallic switch with an extra
contact to switch off both sides of the 240 line in the off position
via a cam on the rotating part.

It would be cool and useful if I could also add a dual color LED to
show the approximate power setting from across the room. My only idea
so far is to treat it like a resistance divider with the common leg of
the LED tied to the junction between the dimmer and heating element
connection. I would use capacitive reactance to lower the voltage and
a diode so the LED isn't reverse biased.

Presumably this should give a relatively smooth transition from green
to red as the control calls for more power.

Does this sound like it aught to work? Is there a better way?

(Horsing the range in and out is no fun. Controls are due to arrive
today..)

Is your question about running the stove with lamp dimmers,
or how to do the led's?

More about LEDs. From the control's point of view, a heating element
is just a load resistor.

Specifically I'm wondering what effect, if any, the steep rise of the
triac firing will have on the capacitor used to limit current/voltage
to the LED, or any effects from putting what amounts to a small
(.25uf) cap across the load and control (would that influence the
firing angle?)

 

[Jasen Betts]

On 2015-05-08, default <default@defaulter.net> wrote:

On Fri, 8 May 2015 09:34:19 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Friday, May 8, 2015 at 8:31:49 AM UTC-4, default wrote:
I've got some 4KW 240 volt lamp dimmers from China.

What I want is a cheap electric range current regulator. (For safety
I plan to replace the potentiometers with switched ones and add dual
pole contactor - so "off" really is off)

The controls I'm replacing use a bimetallic switch with an extra
contact to switch off both sides of the 240 line in the off position
via a cam on the rotating part.

It would be cool and useful if I could also add a dual color LED to
show the approximate power setting from across the room. My only idea
so far is to treat it like a resistance divider with the common leg of
the LED tied to the junction between the dimmer and heating element
connection. I would use capacitive reactance to lower the voltage and
a diode so the LED isn't reverse biased.

Presumably this should give a relatively smooth transition from green
to red as the control calls for more power.

Does this sound like it aught to work? Is there a better way?

(Horsing the range in and out is no fun. Controls are due to arrive
today..)

Is your question about running the stove with lamp dimmers,
or how to do the led's?

More about LEDs. From the control's point of view, a heating element
is just a load resistor.

Specifically I'm wondering what effect, if any, the steep rise of the
triac firing will have on the capacitor used to limit current/voltage
to the LED, or any effects from putting what amounts to a small
(.25uf) cap across the load and control (would that influence the
firing angle?)

seeing as you're going to have 100 ohms in series with it to protect
the rectifier, not much.

--
umop apisdn

 

[Dimitrij Klingbeil]

On 08.05.2015 14:31, default wrote:

I've got some 4KW 240 volt lamp dimmers from China.

What I want is a cheap electric range current regulator. (For safety
I plan to replace the potentiometers with switched ones and add dual
pole contactor - so "off" really is off)

The controls I'm replacing use a bimetallic switch with an extra
contact to switch off both sides of the 240 line in the off position
via a cam on the rotating part.

It would be cool and useful if I could also add a dual color LED to
show the approximate power setting from across the room. My only
idea so far is to treat it like a resistance divider with the common
leg of the LED tied to the junction between the dimmer and heating
element connection. I would use capacitive reactance to lower the
voltage and a diode so the LED isn't reverse biased.

Presumably this should give a relatively smooth transition from green
to red as the control calls for more power.

Does this sound like it aught to work? Is there a better way?

(Horsing the range in and out is no fun. Controls are due to arrive
today..)

There are several likely issues with your design.

1. Note that the heaters may not survive continuous operation and may
require a maximum duty cycle for safe operation. You have to make sure
to not exceed the heaters' ratings, and if the original controls imposed
a maximum duty cycle - so must yours. If the original controls had
another means of overtemperature protection, e.g. a thermostat, then you
have to make sure that this protection still works in your setup.

2. Ratings / derating of the lamp dimmers. There may be some numbers
printed on them, and they may indicate a rating of 4 kW, but whether
these controls can actually handle that power - and whether they can
handle it for any extended period of time - is not a given.

Any number advertized in bold letters is likely to be overstated by a
factor of 2 at the least. Besides, you have not made clear, in what
temperature range these ratings are supposed to apply. If that's not
given, then most likely the ratings only apply at a nominal room
temperature - like 23 °C or thereabouts. All taken together could mean
that the controls won't handle 4 kW for hours in the thermal environment
of a stove's control bay. They may handle 1 or 2 kW, but for anything
higher you'd better pay close attention to the environmental
specification of these controls. And since most specifications are
egregious lies anyway - better open one of them and have a look at the
triac, its thermal management and its overtemperature protection.
Do a quick datasheet sanity-check of the triac and a similarly sized
heatsink, just to be sure. Remember, since you probably imported them
yourself, their safe operation will be your responsibility.

3. Use of capacitors to "feed" LEDs from mains, particularly from triac
phase-controlled mains. This is a horribly bad idea that smells of an
electrical fire. Forget about is as quickly as you can.

Capacitors, even "X" rated ones, are usually not made to withstand
continuously pulsed loads. "Normal" capacitors won't even withstand a
typical mains surge, which can have 2 to 4 kV. Applying a pulse train
from a low-impedance source (mains) via a low-impedance switch (triac)
to a low-impedance load (capacitor during the pulse risetime) will blast
that load (capacitor + LED) with sharp current spikes that can have
peaks as high as hundreds of amps (for microseconds). This will fry the
LEDs really fast, and it will also fry the capacitor after some
unspecified time unless the cap is rated for such continuous impulse
loads. Failing caps connected to mains with hardly any current limiting
tend to short out and go up in flames.

If you absolutely must use capacitors, then make sure that you:
a) use capacitors with at least an "X1" rating for 240 V mains and with
a recognized agency approval (UL / CSA / TÜV / ...)
b) use additional resistors in series with the caps
c) size the resistors so that the current spike, when switching the peak
of the sinewave into a discharged capacitor, will be limited to a
reasonable value - preferably below 100 mA. In practice this means a
resistor of at least 3.5 k resistance - better 5 k.
d) size the cap to limit the RMS current to a reasonable value -
preferably at 10 mA or below.
e) use at least 2 resistors in series for single fault tolerance
f) size the resistors such that they can withstand at least 1 kV pulses,
for each resistor (assuming you have 2 in series)
g) don't underestimate power dissipation in resistors (ca. 0.5 W)
h) don't forget the freewheeling diode across the LED to protect it from
reverse voltage.

4. Miscellaneous points to consider

Isolate the LEDs properly. A mains-operated LED has no business
"sticking out" accessible to people. The LED's plastic encapsulation is
not a safety insulation either. It can break off and it's not rated for
mains surges. Put the LEDs into properly insulated holders intended for
mains operation (like e.g. those used for neon lamps).

Make sure that your potentiometers are properly isolated too - and that
their isolation is rated for mains operation. For a safety grounded
metal case that also implies at least a BASIC insulation from
potentiometer circuits to the case.

Isolate your wiring properly. That includes appropriate temperature
ratings of the wiring isolation used! Isolate all auxiliary circuits
(relays, capacitors, resistors, circuit board if any) properly too.
That also includes clearances, creepage distances and choice of
materials with respect to flammability and operating temperature.
Given your intended environment, that also includes appropriate
placement of those auxiliary components with respect to heat sources.

Always remember that it's you who is responsible for your (and your
family's) safety as far as any electrical work is concerned.

Additionally, LEDs driven from half-wave-rectified mains can flicker
rather annoyingly. Apparently the human eye is sensitive to the duty
cycle and the risetime of light pulses to some extent, so LEDs that
light up and extinguish essentially instantly flicker more than
e.g. discharge lamps that have more significant time constants.
Unlike the points noted above, this is obviously not safety-relevant,
but you may still want to avoid the flicker anyway.

If you don't want the flicker, consider adding another diode and an RC
circuit to feed the LED with a more steady DC current. Note that since
the LED is a current-driven device, the RC circuit will become a "CR"
circuit. It is "inverted" - with the R in series with the LED and the C
"feeding" the R+LED combination. This is opposite to a "normal" RC
circuit where the C is connected in parallel to the (voltage-driven) load.

Dimitrij

 

[Dimitrij Klingbeil]

Sorry, forgot one more thing...

The lamp dimmers that you intend to use as heater controls may have fuse
ratings specified. These may sometimes be denoted with a "fuse" symbol
and an amperage rating next to it (like e.g. "-[====]- 16A"). The fuse
ratings indicate that the control can only be used safely on a circuit
that is fused with a fuse of the rating indicated. Since the fuses (or
circuit breakers) in your house wiring are likely to have higher ratings
than the dimmer controls call for, you may have to install appropriate
fuses in series with these dimmers in order to satisfy their specified
fuse ratings. If those dimmers already have internal fuses installed,
then they are less likely to specify requirements for additional fuses.
But if they neither have fuses of their own nor specify fuse ratings for
the installation, then their maker was probably less concerned about
safety. In this case, it's probably prudent to install fuses based on
the specified maximum power ratings. In any case, always install fuses
with interrupt ratings appropriate for the circuits they are in (like
HRC fuses for mains circuits).

Dimitrij

 

Dimitrij Klingbeil <nospam@no-address.com> wrote:

Since the fuses (or circuit breakers) in your house wiring are likely
to have higher ratings than the dimmer controls call for, you may have
to install appropriate fuses in series with these dimmers in order to
satisfy their specified fuse ratings.

In the US, a standard electric stove circuit is 240 V, 50 A (12 kW).
Most houses will have a thermal-magnetic circuit breaker for this, but
some older houses (before roughly the early 1960s) may still have fuses.

The original poster might be better served by using thermistors or
thermocouples at each surface element to drive a comparator that drives
the red-green LEDs, and a regular transformer power supply to power the
comparators and LEDs.

Matt Roberds

 

[Dimitrij Klingbeil]

On 09.05.2015 11:51, mroberds@att.net wrote:

Dimitrij Klingbeil <nospam@no-address.com> wrote:
Since the fuses (or circuit breakers) in your house wiring are
likely to have higher ratings than the dimmer controls call for,
you may have to install appropriate fuses in series with these
dimmers in order to satisfy their specified fuse ratings.

In the US, a standard electric stove circuit is 240 V, 50 A (12 kW).
Most houses will have a thermal-magnetic circuit breaker for this,
but some older houses (before roughly the early 1960s) may still have
fuses.

The original poster might be better served by using thermistors or
thermocouples at each surface element to drive a comparator that
drives the red-green LEDs, and a regular transformer power supply to
power the comparators and LEDs.

Matt Roberds

Thanks, good to know. Here in Germany, 25 A seems to be more common.
With US-type 50 A circuits, the OP should better fuse his dimmers at
20 A (or similar) separately.

Dimitrij

 

[Dimitrij Klingbeil]

On 09.05.2015 11:51, mroberds@att.net wrote:

The original poster might be better served by using thermistors or
thermocouples at each surface element to drive a comparator that
drives the red-green LEDs, and a regular transformer power supply to
power the comparators and LEDs.

P.S. Electronic solutions are all well and good, but for the hostile
thermal environment of a stove control bay I think something simpler
should be better. Even transformers might end up operating right at
their thermal cutout limits, without even being loaded much.

My preference would be 2 neon lamps, one orange and one green (actually
the green ones are with mercury vapor and phosphor coating but they look
just like neon lamps). They are available with identical sizes and
similar brightness levels. Here's an example:

http://www.farnell.com/datasheets/1662580.pdf

Connect current limiting resistors as indicated, making sure to use at
least 2 in series for surge and single fault tolerance, then the lamps
can be connected across the dimmer (green) and across the heating
element (normal neon) just like the OP intended to connect the LEDs.
That should be simple and provide a reasonable degree of passive safety
(it's difficult to induce a fault that would take out the lamp circuit
in an unsafe way).

Regards
Dimitrij

 

[default]

On Sat, 9 May 2015 09:51:41 +0000 (UTC), mroberds@att.net wrote:

Dimitrij Klingbeil <nospam@no-address.com> wrote:
Since the fuses (or circuit breakers) in your house wiring are likely
to have higher ratings than the dimmer controls call for, you may have
to install appropriate fuses in series with these dimmers in order to
satisfy their specified fuse ratings.

In the US, a standard electric stove circuit is 240 V, 50 A (12 kW).
Most houses will have a thermal-magnetic circuit breaker for this, but
some older houses (before roughly the early 1960s) may still have fuses.

The original poster might be better served by using thermistors or
thermocouples at each surface element to drive a comparator that drives
the red-green LEDs, and a regular transformer power supply to power the
comparators and LEDs.

Matt Roberds

Hey I like that idea. May be a touch more than a thermistor could
deal with, but there are easy to use thermocouple conversion devices
these days.

 

[default]

On Fri, 08 May 2015 23:35:03 +0200, Dimitrij Klingbeil
<nospam@no-address.com> wrote:

On 08.05.2015 14:31, default wrote:
I've got some 4KW 240 volt lamp dimmers from China.

What I want is a cheap electric range current regulator. (For safety
I plan to replace the potentiometers with switched ones and add dual
pole contactor - so "off" really is off)

The controls I'm replacing use a bimetallic switch with an extra
contact to switch off both sides of the 240 line in the off position
via a cam on the rotating part.

It would be cool and useful if I could also add a dual color LED to
show the approximate power setting from across the room. My only
idea so far is to treat it like a resistance divider with the common
leg of the LED tied to the junction between the dimmer and heating
element connection. I would use capacitive reactance to lower the
voltage and a diode so the LED isn't reverse biased.

Presumably this should give a relatively smooth transition from green
to red as the control calls for more power.

Does this sound like it aught to work? Is there a better way?

(Horsing the range in and out is no fun. Controls are due to arrive
today..)

There are several likely issues with your design.

1. Note that the heaters may not survive continuous operation and may
require a maximum duty cycle for safe operation. You have to make sure
to not exceed the heaters' ratings, and if the original controls imposed
a maximum duty cycle - so must yours. If the original controls had
another means of overtemperature protection, e.g. a thermostat, then you
have to make sure that this protection still works in your setup.

2. Ratings / derating of the lamp dimmers. There may be some numbers
printed on them, and they may indicate a rating of 4 kW, but whether
these controls can actually handle that power - and whether they can
handle it for any extended period of time - is not a given.

Any number advertized in bold letters is likely to be overstated by a
factor of 2 at the least. Besides, you have not made clear, in what
temperature range these ratings are supposed to apply. If that's not
given, then most likely the ratings only apply at a nominal room
temperature - like 23 °C or thereabouts. All taken together could mean
that the controls won't handle 4 kW for hours in the thermal environment
of a stove's control bay. They may handle 1 or 2 kW, but for anything
higher you'd better pay close attention to the environmental
specification of these controls. And since most specifications are
egregious lies anyway - better open one of them and have a look at the
triac, its thermal management and its overtemperature protection.
Do a quick datasheet sanity-check of the triac and a similarly sized
heatsink, just to be sure. Remember, since you probably imported them
yourself, their safe operation will be your responsibility.

3. Use of capacitors to "feed" LEDs from mains, particularly from triac
phase-controlled mains. This is a horribly bad idea that smells of an
electrical fire. Forget about is as quickly as you can.

Capacitors, even "X" rated ones, are usually not made to withstand
continuously pulsed loads. "Normal" capacitors won't even withstand a
typical mains surge, which can have 2 to 4 kV. Applying a pulse train
from a low-impedance source (mains) via a low-impedance switch (triac)
to a low-impedance load (capacitor during the pulse risetime) will blast
that load (capacitor + LED) with sharp current spikes that can have
peaks as high as hundreds of amps (for microseconds). This will fry the
LEDs really fast, and it will also fry the capacitor after some
unspecified time unless the cap is rated for such continuous impulse
loads. Failing caps connected to mains with hardly any current limiting
tend to short out and go up in flames.

If you absolutely must use capacitors, then make sure that you:
a) use capacitors with at least an "X1" rating for 240 V mains and with
a recognized agency approval (UL / CSA / TÜV / ...)
b) use additional resistors in series with the caps
c) size the resistors so that the current spike, when switching the peak
of the sinewave into a discharged capacitor, will be limited to a
reasonable value - preferably below 100 mA. In practice this means a
resistor of at least 3.5 k resistance - better 5 k.
d) size the cap to limit the RMS current to a reasonable value -
preferably at 10 mA or below.
e) use at least 2 resistors in series for single fault tolerance
f) size the resistors such that they can withstand at least 1 kV pulses,
for each resistor (assuming you have 2 in series)
g) don't underestimate power dissipation in resistors (ca. 0.5 W)
h) don't forget the freewheeling diode across the LED to protect it from
reverse voltage.

4. Miscellaneous points to consider

Isolate the LEDs properly. A mains-operated LED has no business
"sticking out" accessible to people. The LED's plastic encapsulation is
not a safety insulation either. It can break off and it's not rated for
mains surges. Put the LEDs into properly insulated holders intended for
mains operation (like e.g. those used for neon lamps).

Make sure that your potentiometers are properly isolated too - and that
their isolation is rated for mains operation. For a safety grounded
metal case that also implies at least a BASIC insulation from
potentiometer circuits to the case.

Isolate your wiring properly. That includes appropriate temperature
ratings of the wiring isolation used! Isolate all auxiliary circuits
(relays, capacitors, resistors, circuit board if any) properly too.
That also includes clearances, creepage distances and choice of
materials with respect to flammability and operating temperature.
Given your intended environment, that also includes appropriate
placement of those auxiliary components with respect to heat sources.

Always remember that it's you who is responsible for your (and your
family's) safety as far as any electrical work is concerned.

Additionally, LEDs driven from half-wave-rectified mains can flicker
rather annoyingly. Apparently the human eye is sensitive to the duty
cycle and the risetime of light pulses to some extent, so LEDs that
light up and extinguish essentially instantly flicker more than
e.g. discharge lamps that have more significant time constants.
Unlike the points noted above, this is obviously not safety-relevant,
but you may still want to avoid the flicker anyway.

If you don't want the flicker, consider adding another diode and an RC
circuit to feed the LED with a more steady DC current. Note that since
the LED is a current-driven device, the RC circuit will become a "CR"
circuit. It is "inverted" - with the R in series with the LED and the C
"feeding" the R+LED combination. This is opposite to a "normal" RC
circuit where the C is connected in parallel to the (voltage-driven) load.

Dimitrij

I do appreciate your erring on the side of caution, and the time and
effort you spent. but... This isn't my first foray into electronics
and I've had one 5 amp SSR with slow pulse width modulation working
one element and another on a 10 A SSR with a small programmed
controller chip. With tricolor LEDs (and working off a low voltage
supply)

I was looking for something I could implement with a little less
effort.

The 4 KW controller looks like it may actually do 4 KW - heat sink and
aluminum chassis and the elements I'm intending to use them are 800
watts and 600 watts.

As for running LEDs with a diode, cap and small surge limiting
resistor - been doing that for some time now. The circuit is in the
Siemens Optoelectronics Data Book 1990 App note 6.

Safety is my primary concern, and my designs do reflect this. "This
ain't my first rodeo" is the idiom we use.

 

[Dimitrij Klingbeil]

On 09.05.2015 18:46, default wrote:

I do appreciate your erring on the side of caution, and the time and
effort you spent. but... This isn't my first foray into electronics
and I've had one 5 amp SSR with slow pulse width modulation working
one element and another on a 10 A SSR with a small programmed
controller chip. With tricolor LEDs (and working off a low voltage
supply)

I was looking for something I could implement with a little less
effort.

The 4 KW controller looks like it may actually do 4 KW - heat sink
and aluminum chassis and the elements I'm intending to use them are
800 watts and 600 watts.

As for running LEDs with a diode, cap and small surge limiting
resistor - been doing that for some time now. The circuit is in the
Siemens Optoelectronics Data Book 1990 App note 6.

Safety is my primary concern, and my designs do reflect this. "This
ain't my first rodeo" is the idiom we use.

Ah, alright then. You can't tell experience from a short usenet post,
and since high temperatures, electronics, and surges don't mix well,
I thought it better to call your attention to some caveats.

Hey, at least some of that info may turn up useful for some future
novices searching or reading some usenet archive somewhere

If you want a simple solution, why not 2 "neon" lamps with different
colors? Orange and green are common, and some other colors seem to
exist too (a photo on the the wiki page shows a blue one).
It's hard to beat resistors in terms of simplicity.

Dimitrij

 

[default]

On Sat, 09 May 2015 21:31:30 +0200, Dimitrij Klingbeil
<nospam@no-address.com> wrote:

On 09.05.2015 18:46, default wrote:
I do appreciate your erring on the side of caution, and the time and
effort you spent. but... This isn't my first foray into electronics
and I've had one 5 amp SSR with slow pulse width modulation working
one element and another on a 10 A SSR with a small programmed
controller chip. With tricolor LEDs (and working off a low voltage
supply)

I was looking for something I could implement with a little less
effort.

The 4 KW controller looks like it may actually do 4 KW - heat sink
and aluminum chassis and the elements I'm intending to use them are
800 watts and 600 watts.

As for running LEDs with a diode, cap and small surge limiting
resistor - been doing that for some time now. The circuit is in the
Siemens Optoelectronics Data Book 1990 App note 6.

Safety is my primary concern, and my designs do reflect this. "This
ain't my first rodeo" is the idiom we use.

Ah, alright then. You can't tell experience from a short usenet post,
and since high temperatures, electronics, and surges don't mix well,
I thought it better to call your attention to some caveats.

Hey, at least some of that info may turn up useful for some future
novices searching or reading some usenet archive somewhere

If you want a simple solution, why not 2 "neon" lamps with different
colors? Orange and green are common, and some other colors seem to
exist too (a photo on the the wiki page shows a blue one).
It's hard to beat resistors in terms of simplicity.

Dimitrij

Thanks, that is a good idea.

 

[default]

On Sat, 09 May 2015 18:43:55 -0400, default <default@defaulter.net>
wrote:

On Sat, 09 May 2015 21:31:30 +0200, Dimitrij Klingbeil
nospam@no-address.com> wrote:

On 09.05.2015 18:46, default wrote:
I do appreciate your erring on the side of caution, and the time and
effort you spent. but... This isn't my first foray into electronics
and I've had one 5 amp SSR with slow pulse width modulation working
one element and another on a 10 A SSR with a small programmed
controller chip. With tricolor LEDs (and working off a low voltage
supply)

I was looking for something I could implement with a little less
effort.

The 4 KW controller looks like it may actually do 4 KW - heat sink
and aluminum chassis and the elements I'm intending to use them are
800 watts and 600 watts.

As for running LEDs with a diode, cap and small surge limiting
resistor - been doing that for some time now. The circuit is in the
Siemens Optoelectronics Data Book 1990 App note 6.

Safety is my primary concern, and my designs do reflect this. "This
ain't my first rodeo" is the idiom we use.

Ah, alright then. You can't tell experience from a short usenet post,
and since high temperatures, electronics, and surges don't mix well,
I thought it better to call your attention to some caveats.

Hey, at least some of that info may turn up useful for some future
novices searching or reading some usenet archive somewhere

If you want a simple solution, why not 2 "neon" lamps with different
colors? Orange and green are common, and some other colors seem to
exist too (a photo on the the wiki page shows a blue one).
It's hard to beat resistors in terms of simplicity.

Dimitrij

Thanks, that is a good idea.

Or maybe not. The voltage has to exceed the firing threshold of the
gas, but that still may not be a bad idea. One neon on for minimum
power, two with some overlap for the midrange and the other on for
maximum power.

With my IC controller, the leds I have come on red when on and green
when off and can see the relative pulse width from anywhere in the
room. For maximum power there is no proportioning and I turn on the
red and blue together for magenta.