dimmers
- Thread starter mario
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rick hart
Senior Member
- Location
- Dallas Texas
Re: dimmers
OK let's REALLY go over the deep end:
How much power is being consumed when the 100% lamp DIMMER is at full?
I chuckled when I saw the rheostat explained in a book over a half century old.
OK let's REALLY go over the deep end:
How much power is being consumed when the 100% lamp DIMMER is at full?
I chuckled when I saw the rheostat explained in a book over a half century old.
Re: dimmers
Sorry I haven't been back on; been watching all the responses though ... absolutely great ... learned a bit ... will be checking it out myself in next couple of days with my "T-5"(tools are at my son's new house we're wiring) ... will let you know results ... thanks to all ... hey if there's more to this, let me know ... M
Sorry I haven't been back on; been watching all the responses though ... absolutely great ... learned a bit ... will be checking it out myself in next couple of days with my "T-5"(tools are at my son's new house we're wiring) ... will let you know results ... thanks to all ... hey if there's more to this, let me know ... M
al hildenbrand
Senior Member
- Location
- Minnesota
- Occupation
- Electrical Contractor, Electrical Consultant, Electrical Engineer
Re: dimmers
The 0.7 V across the triac is essentially constant through the range of the dimmer, that is, constant for all the possible effective current levels the dimmer runs at.
So, the 100 W bulb, given full voltage will want to draw:
100 W ? 120 V = 0.8 A
The power dissipated at the triac heat sink in the dimmer, running the bulb at 99% will be just slightly less than:
0.8 A ? 0.7 V = 0.56 Watt
There will also be a smaller bit of heat coming from the inductor (EMI / RFI choke) and the switch contact and the wire itself. This amount of heat is as negligible as the power used in the control circuit of the dimmer (the control that triggers the triac).
Recalling my solid state circuit theory, from back when, the triac, being constructed of silicon, will have a voltage drop of 0.7 V when it is conducting.
The 0.7 V across the triac is essentially constant through the range of the dimmer, that is, constant for all the possible effective current levels the dimmer runs at.
So, the 100 W bulb, given full voltage will want to draw:
100 W ? 120 V = 0.8 A
The power dissipated at the triac heat sink in the dimmer, running the bulb at 99% will be just slightly less than:
0.8 A ? 0.7 V = 0.56 Watt
There will also be a smaller bit of heat coming from the inductor (EMI / RFI choke) and the switch contact and the wire itself. This amount of heat is as negligible as the power used in the control circuit of the dimmer (the control that triggers the triac).
Re: dimmers
i would agree with al hildenbrand interms of power loss at dimmer.
But not in total power consumption...
As far as dimmer concern, it may (?) consume 0.56w whether it is low mode or high mode,irrespetive of regulation.It is constant once you turn on the Dimmer.
But as far as load concern (any kind of load),
the resistance remain same ,we are not controlling the resistance of the load here....
Forget about diac,triac,thyrister etc,.See the fundamental........
If ,we assume the dimmer is controlling the voltage here.the load (100w) will consume more current to meet the power demand of the 100w bulb,since the resistance remain same.
(Second one,It is just for a debate) If we assume the dimmer is controlling the current, the load (100w) would consume more voltage to meet the 100w power demand,since the resistance remain same.(But practically it is not possible because our system has standard voltage of 120V)
So, as far as my concern,once the dimmer is turned on, the entire system (100w load + Dimmer) will consume 100W+0.56W= 100.56W.
I really dont konw what exact power consumption,that may includes wire loss also.
So let us wait till MARIO go to site and come back with clear picture.
Thanks for all...
Jeyakumar
.
i would agree with al hildenbrand interms of power loss at dimmer.
But not in total power consumption...
As far as dimmer concern, it may (?) consume 0.56w whether it is low mode or high mode,irrespetive of regulation.It is constant once you turn on the Dimmer.
But as far as load concern (any kind of load),
the resistance remain same ,we are not controlling the resistance of the load here....
Forget about diac,triac,thyrister etc,.See the fundamental........
If ,we assume the dimmer is controlling the voltage here.the load (100w) will consume more current to meet the power demand of the 100w bulb,since the resistance remain same.
(Second one,It is just for a debate) If we assume the dimmer is controlling the current, the load (100w) would consume more voltage to meet the 100w power demand,since the resistance remain same.(But practically it is not possible because our system has standard voltage of 120V)
So, as far as my concern,once the dimmer is turned on, the entire system (100w load + Dimmer) will consume 100W+0.56W= 100.56W.
I really dont konw what exact power consumption,that may includes wire loss also.
So let us wait till MARIO go to site and come back with clear picture.
Thanks for all...
Jeyakumar
Re: dimmers
Electronic dimmers utilize electronic switches (Triacs) to perform duty cycle modulation on the AC wave. A crude model would be a rapidly operating mechanical switch in series with a fixed resistance. As the duty cycle increases, the effective current increases which in turn increases the dissipation in the lamp and in the dimmer. The dimmer controls both effective current and effective voltage!
Furthermore, at 100% duty cycle, the dimmer inserts a resistance in series with the lamp which drops the applied voltage slightly, therefore, the dissipation will be reduced from 100W. There is no way that the total dissipation can be more than 100W.
Al's analysis is basically right, but the 0.7V drop (approximate diode drop) is perhaps too high for Vce(sat) of a bipolar transistor. Also, there is a resistive element to consider as well as the chopped up sinusoidal current. A circuit analysis program with the right transistor model and parameters would be required to compute this drop with any degree of accuracy.
Not so!
Electronic dimmers utilize electronic switches (Triacs) to perform duty cycle modulation on the AC wave. A crude model would be a rapidly operating mechanical switch in series with a fixed resistance. As the duty cycle increases, the effective current increases which in turn increases the dissipation in the lamp and in the dimmer. The dimmer controls both effective current and effective voltage!
Furthermore, at 100% duty cycle, the dimmer inserts a resistance in series with the lamp which drops the applied voltage slightly, therefore, the dissipation will be reduced from 100W. There is no way that the total dissipation can be more than 100W.
Al's analysis is basically right, but the 0.7V drop (approximate diode drop) is perhaps too high for Vce(sat) of a bipolar transistor. Also, there is a resistive element to consider as well as the chopped up sinusoidal current. A circuit analysis program with the right transistor model and parameters would be required to compute this drop with any degree of accuracy.
dave_asdf
Member
- Location
- tampa florida
Re: dimmers
quick question guys, its been a long time since i looked at any solid state stuff but i was wondering where that .7V drop came from... wouldnt that depend on the type of scr or diode and different doping levels and arrangements of the silicon layers? i would think that a solid state diode rated at 4 volts in electronics and a static switch rated at 1000A would have different voltage drops associated with them. i'm sure on the dimmer switch level all this is trivial but then again we're already 2 pages into it.
i'm way out of my league here and i probably have no clue what i am talking about but i figured you guys could set me straight. thanks guys
quick question guys, its been a long time since i looked at any solid state stuff but i was wondering where that .7V drop came from... wouldnt that depend on the type of scr or diode and different doping levels and arrangements of the silicon layers? i would think that a solid state diode rated at 4 volts in electronics and a static switch rated at 1000A would have different voltage drops associated with them. i'm sure on the dimmer switch level all this is trivial but then again we're already 2 pages into it.
i'm way out of my league here and i probably have no clue what i am talking about but i figured you guys could set me straight. thanks guys
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Re: dimmers
Jeyakumar,
When you have a fixed resistance the current in the circuit is a function of the applied voltage I=E/R^2, so at 70% voltage we will have 70% current. A "heater" load can not draw more current to generate it's rated output, instead it lowers it's output based on the amount of current available.
This behavior is not true for motors and other inductive loads.
Jeyakumar,
When you have a fixed resistance the current in the circuit is a function of the applied voltage I=E/R^2, so at 70% voltage we will have 70% current. A "heater" load can not draw more current to generate it's rated output, instead it lowers it's output based on the amount of current available.
This behavior is not true for motors and other inductive loads.
peteo
Senior Member
- Location
- Los Angeles
Re: dimmers
What a great topic! Please don't let my comments stop anyone from digging in. I'd like to comment on two of the questions being discussed, first energy savings and second the dimmer technology.
Here in California we've had a major upgrade to energy codes recently (Nov 1) - even last year's included language about dimming. To stick to the topic, yes dimmers do save electricity. I agree with Rattus and the rest, but Rick had the point nailed - even if we set up an RMS meter, the equipment would be hotter or cooler tomorrow, and the line in would change. These and other effects would result in a different level, ultimately requiring an extra light switch in every room to verify hitting the 50% or 35% level. This has been the interpretation for three years and is now written into the new code.
As almost an aside, at one point we were putting together a solid state relay circuit (triac, with an optocoupler) for a machine tool in 1999. Triacs have a silicon junction, so they have at least 0.7 volts drop. Ours was a very simple three terminal device, with goesin, goesout, and an RC timer. That timer just sets up the delay between when the sine wave crosses zero and the junction is turned on. Faster the junction is slapped ON, less heat is created, which is why they build the matched triac/ coupler. The actual thing fit into two inches of 1/2 inch heatshrink. About the size of a blue wirenut.
To really test the new thing, a heavy inductive load was used, namely our cafeteria lights. The cafeteria had three fluorescent circuits, and household motion detectors were used to switch the relays. Those darn things had, if I remember, 6, 12, and 18 - 4 tube, 8 foot fixtures! The only 'problem' was when the detectors cycled the lights off then back on. Some heating at the device, but never hot to the touch. It was a very good test of just how much is lost in dimmers - I'd say negligible.
[ January 20, 2006, 11:19 AM: Message edited by: peteo ]
What a great topic! Please don't let my comments stop anyone from digging in. I'd like to comment on two of the questions being discussed, first energy savings and second the dimmer technology.
Here in California we've had a major upgrade to energy codes recently (Nov 1) - even last year's included language about dimming. To stick to the topic, yes dimmers do save electricity. I agree with Rattus and the rest, but Rick had the point nailed - even if we set up an RMS meter, the equipment would be hotter or cooler tomorrow, and the line in would change. These and other effects would result in a different level, ultimately requiring an extra light switch in every room to verify hitting the 50% or 35% level. This has been the interpretation for three years and is now written into the new code.
As almost an aside, at one point we were putting together a solid state relay circuit (triac, with an optocoupler) for a machine tool in 1999. Triacs have a silicon junction, so they have at least 0.7 volts drop. Ours was a very simple three terminal device, with goesin, goesout, and an RC timer. That timer just sets up the delay between when the sine wave crosses zero and the junction is turned on. Faster the junction is slapped ON, less heat is created, which is why they build the matched triac/ coupler. The actual thing fit into two inches of 1/2 inch heatshrink. About the size of a blue wirenut.
To really test the new thing, a heavy inductive load was used, namely our cafeteria lights. The cafeteria had three fluorescent circuits, and household motion detectors were used to switch the relays. Those darn things had, if I remember, 6, 12, and 18 - 4 tube, 8 foot fixtures! The only 'problem' was when the detectors cycled the lights off then back on. Some heating at the device, but never hot to the touch. It was a very good test of just how much is lost in dimmers - I'd say negligible.
[ January 20, 2006, 11:19 AM: Message edited by: peteo ]
Re: dimmers
Yo Peteo (sounds Italian) ...did you suceed in "Dimming the Lights" (flourescent) ?? did you check the wattage consumed ??
I guess I'm gonna hav'ta go buy me a "watt meter" and check this my self ...
Don't get me wrong guys, the input has been excellent .. the info though, as was expected, has opinions in about all aspects of the original question ... I'm still a bit confused though .. I've read both sides of ""The Dimmer "DOES/DOESN'T" Save Energy Consumed"" .. HHMMMM..who do I believe ... I'm definitely more educated in the "Electronics" area though .. thanks
keep it coming guys ... M
Yo Peteo (sounds Italian) ...did you suceed in "Dimming the Lights" (flourescent) ?? did you check the wattage consumed ??
I guess I'm gonna hav'ta go buy me a "watt meter" and check this my self ...
Don't get me wrong guys, the input has been excellent .. the info though, as was expected, has opinions in about all aspects of the original question ... I'm still a bit confused though .. I've read both sides of ""The Dimmer "DOES/DOESN'T" Save Energy Consumed"" .. HHMMMM..who do I believe ... I'm definitely more educated in the "Electronics" area though .. thanks
keep it coming guys ... M
al hildenbrand
Senior Member
- Location
- Minnesota
- Occupation
- Electrical Contractor, Electrical Consultant, Electrical Engineer
Re: dimmers
Yes, without question.
Re: dimmers
You don't need a wattmeter. Just use your senses as the lamp gets hotter or cooler. Ditto for the dimmer itself.
One must understand that a 100W lamp dissipates 100W only when rated voltage is applied. Reduce this voltage and the current falls as well. That is the VxI product (power) falls.
Now let me correct myself. I think now that Al's estimate of 0.7V for the dimmer voltage drop is too low. The Triac current must flow through a base-emitter junction as well as through the collector-base-emitter of a second transistor. I would say 1V would be a better estimate.
[ January 20, 2006, 03:53 PM: Message edited by: rattus ]
No need to keep count Mario. It is obvious that the dimmer reduces power to the lamp. It is also obvious that power loss in the dimmer is roughly proportional to the power dissipated in the lamp.Originally posted by mario:
Well, thats (1) for the "DOES" side ... M
You don't need a wattmeter. Just use your senses as the lamp gets hotter or cooler. Ditto for the dimmer itself.
One must understand that a 100W lamp dissipates 100W only when rated voltage is applied. Reduce this voltage and the current falls as well. That is the VxI product (power) falls.
Now let me correct myself. I think now that Al's estimate of 0.7V for the dimmer voltage drop is too low. The Triac current must flow through a base-emitter junction as well as through the collector-base-emitter of a second transistor. I would say 1V would be a better estimate.
[ January 20, 2006, 03:53 PM: Message edited by: rattus ]
peteo
Senior Member
- Location
- Los Angeles
Re: dimmers
when a dimmer is used for lights, is the "Wattage" reduced in the circuit?
Yes, without question.
when a dimmer is used for lights, is the "Wattage" reduced in the circuit?
Yes, without question.
al hildenbrand
Senior Member
- Location
- Minnesota
- Occupation
- Electrical Contractor, Electrical Consultant, Electrical Engineer
Re: dimmers
The simple point that I did not punch hard is: The voltage drop across the silicon controlled solid state switch element is constant when the element is conducting, regardless of the current level.
When the 100 W bulb is full bright, the voltage drop across the dimmer is the same as:
When the 100 W bulb is getting 75% current, and is the same as:
When the 100 W bulb is getting 50% current, and is the same as:
When the 100 W bulb is getting 25% current, and is the same as:
Etc.
The power turned into heat at the dimmer is, simply, the current going through the dimmer times that constant voltage drop.
Since the dimmer voltage drop is constant, the power at the dimmer turned into heat gets larger as the current gets larger.
This is counter intuitive.
The dimmer is hottest when the dimmer is doing the least dimming (bulb is brightest).
The dimmer is coolest when the dimmer is dimming the bulb as much as it can (bulb is dimmest without being off).
I defer to your expertise.
The simple point that I did not punch hard is: The voltage drop across the silicon controlled solid state switch element is constant when the element is conducting, regardless of the current level.
When the 100 W bulb is full bright, the voltage drop across the dimmer is the same as:
When the 100 W bulb is getting 75% current, and is the same as:
When the 100 W bulb is getting 50% current, and is the same as:
When the 100 W bulb is getting 25% current, and is the same as:
Etc.
The power turned into heat at the dimmer is, simply, the current going through the dimmer times that constant voltage drop.
Since the dimmer voltage drop is constant, the power at the dimmer turned into heat gets larger as the current gets larger.
This is counter intuitive.
The dimmer is hottest when the dimmer is doing the least dimming (bulb is brightest).
The dimmer is coolest when the dimmer is dimming the bulb as much as it can (bulb is dimmest without being off).
Re: dimmers
I will try to find a reference on this.
Whatever, the dimmer is highly efficient. It does reduce power to the load, and it does reduce total power dissipation.
No question about it.
Al, you are right in principle, but the Triac in the ON state presents a resistive element in series with the load, therefore the voltage drop is somewhat dependent on current. It is not abolutely constant.
I will try to find a reference on this.
Whatever, the dimmer is highly efficient. It does reduce power to the load, and it does reduce total power dissipation.
No question about it.
al hildenbrand
Senior Member
- Location
- Minnesota
- Occupation
- Electrical Contractor, Electrical Consultant, Electrical Engineer
Re: dimmers
While not "absolutely" constant, it is, for educational simplification "essentially" constant, no?
I am, personally, interested in what the resistive nature of the conducting triac is, however. If you find something, I'd like to hear it.
While not "absolutely" constant, it is, for educational simplification "essentially" constant, no?
I am, personally, interested in what the resistive nature of the conducting triac is, however. If you find something, I'd like to hear it.
Re: dimmers
Al,
I found a data sheet for a very high current triac. The ON voltage ranged from about 1 to 2 volts from low current to high current. I would expect a low current Triac to behave in a similar manner.
First we have Vbe of a transistor which is exponentially related to Ib. A similar function exists for Vce(sat) of the second transistor. Then we have the bulk resistance of the silicon itself and the resistance of the interconnections.
At one time, I could plow through all this, but I have seen too many sunsets since then for me to try to explain it fully. GE used to be strong in power semiconductors. They published a nice handbook, but I no longer have one.
Still, the dimmer reduces power all around, no question about it!
Al,
I found a data sheet for a very high current triac. The ON voltage ranged from about 1 to 2 volts from low current to high current. I would expect a low current Triac to behave in a similar manner.
First we have Vbe of a transistor which is exponentially related to Ib. A similar function exists for Vce(sat) of the second transistor. Then we have the bulk resistance of the silicon itself and the resistance of the interconnections.
At one time, I could plow through all this, but I have seen too many sunsets since then for me to try to explain it fully. GE used to be strong in power semiconductors. They published a nice handbook, but I no longer have one.
Still, the dimmer reduces power all around, no question about it!
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