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Aaron407
electronics forum beginner
Joined: 27 Jun 2006
Posts: 5
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 Posted: Mon Jul 17, 2006 3:58 am Post subject:
Slow, Automatic Light Dimmer
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I'm hoping someone will have some insight into a simple design for a
type of light dimmer. I'm looking to build a light dimmer that, after
given power by an external timer, will slowly rise from a low dim on
the ac light output (ie. low rms voltage level) to the full voltage
over a course of about 15 minutes. I'm looking for 120Vac input, and
hoping to not require a microcontroller to control anything (not too
into programming). My biggest issue is how to control the voltage
variation that slowly without a manual control or microcontroller.
Overall, I'm just looking for a starting point to base my design on.
I'm an electrical engineering graduate so I do have some background, so
please throw some ideas at me, I'm all ears.
-407 |
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PN2222A
electronics forum beginner
Joined: 07 Jun 2005
Posts: 28
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| Posted: Mon Jul 17, 2006 4:47 am Post subject:
Re: Slow, Automatic Light Dimmer
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"Aaron407" <suekaaron@hotmail.com> wrote in message
news:1153108707.390738.137570@h48g2000cwc.googlegroups.com...
| Quote: | I'm hoping someone will have some insight into a simple design for a
type of light dimmer. I'm looking to build a light dimmer that, after
given power by an external timer, will slowly rise from a low dim on
the ac light output (ie. low rms voltage level) to the full voltage
over a course of about 15 minutes. I'm looking for 120Vac input, and
hoping to not require a microcontroller to control anything (not too
into programming). My biggest issue is how to control the voltage
variation that slowly without a manual control or microcontroller.
|
OK 407.
So. D'yer know how a dimmer works? Go find that bit out.
Then you'll discover you need a ramp on the control voltage what triggers
the SCR (you _do_ know about the SCR?)
That ramp is gonna be real, real ... slow.
So you need to figure about high value resistors and low leakage capacitors.
Am I going too fast?
PN2222A
fsubt 250MHz. |
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Aaron407
electronics forum beginner
Joined: 27 Jun 2006
Posts: 5
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| Posted: Mon Jul 17, 2006 1:19 pm Post subject:
Re: Slow, Automatic Light Dimmer
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Um, yeah, I do know about the conduction angle for firing an SCR to
control the rms voltage you jackass, you don't have to patronize me.
FYI, I focus on large power systems for my degree but I was hoping to
start exploring electronics a little more, thanks for all the help.
PN2222A wrote:
| Quote: | "Aaron407" <suekaaron@hotmail.com> wrote in message
news:1153108707.390738.137570@h48g2000cwc.googlegroups.com...
I'm hoping someone will have some insight into a simple design for a
type of light dimmer. I'm looking to build a light dimmer that, after
given power by an external timer, will slowly rise from a low dim on
the ac light output (ie. low rms voltage level) to the full voltage
over a course of about 15 minutes. I'm looking for 120Vac input, and
hoping to not require a microcontroller to control anything (not too
into programming). My biggest issue is how to control the voltage
variation that slowly without a manual control or microcontroller.
OK 407.
So. D'yer know how a dimmer works? Go find that bit out.
Then you'll discover you need a ramp on the control voltage what triggers
the SCR (you _do_ know about the SCR?)
That ramp is gonna be real, real ... slow.
So you need to figure about high value resistors and low leakage capacitors.
Am I going too fast?
PN2222A
fsubt 250MHz. |
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martin griffith
electronics forum Guru
Joined: 06 May 2005
Posts: 1098
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| Posted: Mon Jul 17, 2006 1:49 pm Post subject:
Re: Slow, Automatic Light Dimmer
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On 16 Jul 2006 20:58:27 -0700, in sci.electronics.design "Aaron407"
<suekaaron@hotmail.com> wrote:
| Quote: | I'm hoping someone will have some insight into a simple design for a
type of light dimmer. I'm looking to build a light dimmer that, after
given power by an external timer, will slowly rise from a low dim on
the ac light output (ie. low rms voltage level) to the full voltage
over a course of about 15 minutes. I'm looking for 120Vac input, and
hoping to not require a microcontroller to control anything (not too
into programming). My biggest issue is how to control the voltage
variation that slowly without a manual control or microcontroller.
Overall, I'm just looking for a starting point to base my design on.
I'm an electrical engineering graduate so I do have some background, so
please throw some ideas at me, I'm all ears.
-407
How about a binary counter with a R2R network on the output, and use |
the FF state of the counter to inhibit the clock input.
It will be better than a RC type time constant. The clock could be
mains derived. One of the problems is that the normal incandescent
lamp does not have a linear relatioship between volts applied and
light output
martin |
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Aaron407
electronics forum beginner
Joined: 27 Jun 2006
Posts: 5
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| Posted: Mon Jul 17, 2006 2:25 pm Post subject:
Re: Slow, Automatic Light Dimmer
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Thanks Martin, I'll look into it. I really appreciate sincere help.
martin griffith wrote:
| Quote: | On 16 Jul 2006 20:58:27 -0700, in sci.electronics.design "Aaron407"
suekaaron@hotmail.com> wrote:
I'm hoping someone will have some insight into a simple design for a
type of light dimmer. I'm looking to build a light dimmer that, after
given power by an external timer, will slowly rise from a low dim on
the ac light output (ie. low rms voltage level) to the full voltage
over a course of about 15 minutes. I'm looking for 120Vac input, and
hoping to not require a microcontroller to control anything (not too
into programming). My biggest issue is how to control the voltage
variation that slowly without a manual control or microcontroller.
Overall, I'm just looking for a starting point to base my design on.
I'm an electrical engineering graduate so I do have some background, so
please throw some ideas at me, I'm all ears.
-407
How about a binary counter with a R2R network on the output, and use
the FF state of the counter to inhibit the clock input.
It will be better than a RC type time constant. The clock could be
mains derived. One of the problems is that the normal incandescent
lamp does not have a linear relatioship between volts applied and
light output
martin |
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Fred Bloggs
electronics forum Guru
Joined: 25 Mar 2005
Posts: 2468
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| Posted: Mon Jul 17, 2006 2:35 pm Post subject:
Re: Slow, Automatic Light Dimmer
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| Quote: | I'm hoping someone will have some insight into a simple design for a
type of light dimmer. I'm looking to build a light dimmer that, after
given power by an external timer, will slowly rise from a low dim on
the ac light output (ie. low rms voltage level) to the full voltage
over a course of about 15 minutes. I'm looking for 120Vac input, and
hoping to not require a microcontroller to control anything (not too
into programming). My biggest issue is how to control the voltage
variation that slowly without a manual control or microcontroller.
Overall, I'm just looking for a starting point to base my design on.
I'm an electrical engineering graduate so I do have some background, so
please throw some ideas at me, I'm all ears.
|
It depends on what kind of effect you are trying to achieve, the timing
is not so much an issue as setting the triggering angle. If you want the
brightening ramp to be barely perceptible ("slowly") then there is
something called the Weber-Fechner Law which relates actual light output
intensity to changes to human perception. This roughly means that if the
bulb drive is increased in discrete increments, then the increase
between increments should be no more than 10% of the intensity
corresponding to the preceding drive. Since the circuit most likely will
use binary counters, this adds other constraints. If say you decide to
use 64 drive levels, as derived from a simple resistor ladder off 6-bits
of counter, and the increment is set to 8% , then this gives you
(1.0 ^64~ 120 to 150 range of intensity for the ramp. The 64 drive
levels also implies 15 x 60 /64 = approximately 14 seconds of dwell at
each level, and this is 15 x 60 x 60/64= 844 line cycles, the most
readily available time base. So your basic circuit will be to initialize
for an RMS output of Vmax/150, count cycles, increment the DAC counter,
servo the bulb drive to Vmax/150*1.08, and so forth until the drive
produces Vmax. I'll leave it to Jim Thompson to work out the best
configuration of parts for you- he has plenty of time on his hands and
claims to relish a challenge. |
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martin griffith
electronics forum Guru
Joined: 06 May 2005
Posts: 1098
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| Posted: Mon Jul 17, 2006 3:34 pm Post subject:
Re: Slow, Automatic Light Dimmer
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On 17 Jul 2006 07:25:46 -0700, in sci.electronics.design "Aaron407"
<suekaaron@hotmail.com> wrote:
| Quote: | Thanks Martin, I'll look into it. I really appreciate sincere help.
martin griffith wrote:
On 16 Jul 2006 20:58:27 -0700, in sci.electronics.design "Aaron407"
suekaaron@hotmail.com> wrote:
I'm hoping someone will have some insight into a simple design for a
type of light dimmer. I'm looking to build a light dimmer that, after
given power by an external timer, will slowly rise from a low dim on
the ac light output (ie. low rms voltage level) to the full voltage
over a course of about 15 minutes. I'm looking for 120Vac input, and
hoping to not require a microcontroller to control anything (not too
into programming). My biggest issue is how to control the voltage
variation that slowly without a manual control or microcontroller.
Overall, I'm just looking for a starting point to base my design on.
I'm an electrical engineering graduate so I do have some background, so
please throw some ideas at me, I'm all ears.
-407
How about a binary counter with a R2R network on the output, and use
the FF state of the counter to inhibit the clock input.
It will be better than a RC type time constant. The clock could be
mains derived. One of the problems is that the normal incandescent
lamp does not have a linear relatioship between volts applied and
light output
martin
WRT Fred's good info, you could use a photocell to monitor the light |
output, and effectively put lamp in a feedback loop, this might give
you a linear response, or it might just be a bit OTT for a simple
device
martin |
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Paul E. Schoen
electronics forum Guru Wannabe
Joined: 01 Jul 2005
Posts: 171
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| Posted: Mon Jul 17, 2006 4:15 pm Post subject:
Re: Slow, Automatic Light Dimmer
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"Fred Bloggs" <nospam@nospam.com> wrote in message
news:44BBA01C.6@nospam.com...
| Quote: |
I'm hoping someone will have some insight into a simple design for a
type of light dimmer. I'm looking to build a light dimmer that, after
given power by an external timer, will slowly rise from a low dim on
the ac light output (ie. low rms voltage level) to the full voltage
over a course of about 15 minutes. I'm looking for 120Vac input, and
hoping to not require a microcontroller to control anything (not too
into programming). My biggest issue is how to control the voltage
variation that slowly without a manual control or microcontroller.
Overall, I'm just looking for a starting point to base my design on.
I'm an electrical engineering graduate so I do have some background, so
please throw some ideas at me, I'm all ears.
It depends on what kind of effect you are trying to achieve, the timing
is not so much an issue as setting the triggering angle. If you want the
brightening ramp to be barely perceptible ("slowly") then there is
something called the Weber-Fechner Law which relates actual light output
intensity to changes to human perception. This roughly means that if the
bulb drive is increased in discrete increments, then the increase between
increments should be no more than 10% of the intensity corresponding to
the preceding drive. Since the circuit most likely will use binary
counters, this adds other constraints. If say you decide to use 64 drive
levels, as derived from a simple resistor ladder off 6-bits of counter,
and the increment is set to 8% , then this gives you (1.0^64~ 120 to
150 range of intensity for the ramp. The 64 drive levels also implies 15
x 60 /64 = approximately 14 seconds of dwell at each level, and this is
15 x 60 x 60/64= 844 line cycles, the most readily available time base.
So your basic circuit will be to initialize for an RMS output of
Vmax/150, count cycles, increment the DAC counter, servo the bulb drive
to Vmax/150*1.08, and so forth until the drive produces Vmax. I'll leave
it to Jim Thompson to work out the best configuration of parts for you-
he has plenty of time on his hands and claims to relish a challenge.
|
This really is a perfect application for a small PIC or other
microcontroller. It would be difficult to make an analog ramp for phase
angle to produce a visually linear change in intensity over a long period.
A PIC could use a lookup table that could be adjusted for the desired
effect. This would compensate for the problem that voltage is not linearly
related to phase angle, and also lamp brightness is not linear with
voltage.
Since so many things are now being done with PICs, it is important to have
a good working knowledge of their capabilities. They are also often much
cheaper and smaller than the equivalent set of conventional logic ICs or
linear components, and have the advantage of simple reprogramming to make
changes, rather than twiddling pots or changing components.
I have the phase modulation PIC code already working for my SCR board, and
it could be readily adapted to this project. I'm willing to email the code
and help with some of the specific programming and circuitry. You can get a
complete development kit (PicKit I) for about $30 from www.microchip.com.
Good luck.
Paul |
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PN2222A
electronics forum beginner
Joined: 07 Jun 2005
Posts: 28
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| Posted: Mon Jul 17, 2006 8:03 pm Post subject:
Re: Slow, Automatic Light Dimmer
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407, man, you cut me to the quick! J***A***? This is usenet,dude. We do
have our standards.
What I'd be looking to do for this problem is this:
Zero-crossing circuit starts a timer when the line voltage is zero.
Prolly the timer's a 555 or so. At the beginning of time (your 15-minute
interval)
the timer waits 8.32msec and sends out a quick pulse.
That pulse fires the triac, turning the lamp on for a bit, until the next
zero-crossing.
As the time runs out of the hourglass, the delay drops from 8.32msec to
zero, or nearly so.
So I want a circuit that drops the trigger voltage steadily (more or less)
from some initial voltage down to zero. Typically an R-C network. Maybe
with a current source to make the ramp linear, and some low-input current
buffers.
Depends on how accurate, and how complex.
At this point, somebody will insist that it's easier to do with a PIC.
They'll be right.
PN2222A
pinout ebc, looking at the package. |
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Aaron407
electronics forum beginner
Joined: 27 Jun 2006
Posts: 5
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| Posted: Mon Jul 17, 2006 8:42 pm Post subject:
Re: Slow, Automatic Light Dimmer
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Ok, I realize I may have been a little harsh, but when a person is
patronized without a request for any clarification, I believe that this
is lowering oneself to a sub-par professional standard and comes off as
mere ignorance to me.
Anyway, as for your solution, that was actually the direction I was
originally headed in to begin with as I have some experience with 555
timers and RC circuits. I just stated the problem broadly as to not
limit myself to any particular foundation for design. However, as you
stated, there will likely be many people that will claim that a PIC
solution is much simpler, and I will probably succomb to the peer
pressure and follow suit, but I'd like to keep my options open at this
point.
407
PN2222A wrote:
| Quote: | 407, man, you cut me to the quick! J***A***? This is usenet,dude. We do
have our standards.
What I'd be looking to do for this problem is this:
Zero-crossing circuit starts a timer when the line voltage is zero.
Prolly the timer's a 555 or so. At the beginning of time (your 15-minute
interval)
the timer waits 8.32msec and sends out a quick pulse.
That pulse fires the triac, turning the lamp on for a bit, until the next
zero-crossing.
As the time runs out of the hourglass, the delay drops from 8.32msec to
zero, or nearly so.
So I want a circuit that drops the trigger voltage steadily (more or less)
from some initial voltage down to zero. Typically an R-C network. Maybe
with a current source to make the ramp linear, and some low-input current
buffers.
Depends on how accurate, and how complex.
At this point, somebody will insist that it's easier to do with a PIC.
They'll be right.
PN2222A
pinout ebc, looking at the package. |
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Dennis
electronics forum beginner
Joined: 04 Feb 2005
Posts: 12
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| Posted: Tue Jul 18, 2006 12:09 am Post subject:
Re: Slow, Automatic Light Dimmer
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PN2222A wrote:
| Quote: |
At this point, somebody will insist that it's easier to do with a PIC.
They'll be right.
PN2222A
pinout ebc, looking at the package.
|
Something like ww1.microchip.com/downloads/en/AppNotes/40171a.pdf |
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Don Lancaster
electronics forum Guru
Joined: 30 Apr 2005
Posts: 416
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| Posted: Tue Jul 18, 2006 12:31 am Post subject:
Re: Slow, Automatic Light Dimmer
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Aaron407 wrote:
| Quote: | I'm hoping someone will have some insight into a simple design for a
type of light dimmer. I'm looking to build a light dimmer that, after
given power by an external timer, will slowly rise from a low dim on
the ac light output (ie. low rms voltage level) to the full voltage
over a course of about 15 minutes. I'm looking for 120Vac input, and
hoping to not require a microcontroller to control anything (not too
into programming). My biggest issue is how to control the voltage
variation that slowly without a manual control or microcontroller.
Overall, I'm just looking for a starting point to base my design on.
I'm an electrical engineering graduate so I do have some background, so
please throw some ideas at me, I'm all ears.
-407
Use a PIC or a BASIC STAMP of course. |
Not using a microcontroller for this ap is fundamentally insane.
--
Many thanks,
Don Lancaster voice phone: (928)428-4073
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
rss: http://www.tinaja.com/whtnu.xml email: don@tinaja.com
Please visit my GURU's LAIR web site at http://www.tinaja.com |
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anno4000@radom.zrz.tu-ber
electronics forum beginner
Joined: 07 Jul 2006
Posts: 4
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| Posted: Thu Jul 20, 2006 12:12 pm Post subject:
Re: Slow, Automatic Light Dimmer
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martin griffith <mart_in_medina@yahoo.esXXX> wrote in sci.electronics.design:
| Quote: | On 17 Jul 2006 07:25:46 -0700, in sci.electronics.design "Aaron407"
suekaaron@hotmail.com> wrote:
Thanks Martin, I'll look into it. I really appreciate sincere help.
martin griffith wrote:
On 16 Jul 2006 20:58:27 -0700, in sci.electronics.design "Aaron407"
suekaaron@hotmail.com> wrote:
|
[...]
| Quote: | How about a binary counter with a R2R network on the output, and use
the FF state of the counter to inhibit the clock input.
It will be better than a RC type time constant. The clock could be
mains derived.
|
15 min at 60 Hz gives a count of 54000. A 16 bit counter would fit
nicely.
Anno |
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