Residential dimmers

[russellroberts]

Residential dimmers

Do modern residential dimmers use scr's to do the deed or something else. Enlighten me please.

 

[Ed MacLaren]

Re: Residential dimmers

Re: Residential dimmers

The basic dimmer uses a bi-directional device called a triac, which is equivalent to two SCRs connected in inverse parallel.

Two separate SCRs could be used.

If a single SCR were used, it would rectify the AC to half-wave DC and cut the voltage to the load in half.

Ed

 

[russellroberts]

Re: Residential dimmers

Re: Residential dimmers

Thanks Ed. I'm probably a bit over my head here,but the triac works on both waves of the ckt,(both directions)? I hope I said that right .

Russell

 

[Ed MacLaren]

Re: Residential dimmers

Re: Residential dimmers

Yes, it switches both halves of the cycle.

The triac is just a very fast electronic switch. By adjusting the 100k pot (R1) the "firing point" (the point at which the triac turns on) can be caused to occur earlier or later in each half-cycle.

The earlier it turns on, the higher the average voltage at the load. The sketch below shows the waveform with the dimmer set at about half voltage.

Ed

 

[russellroberts]

Re: Residential dimmers

Re: Residential dimmers

Great drawing Ed! It really makes it come alive for me,especially the sine waves.

Thanks again,Russell

 

[Guest]

Re: Residential dimmers

Re: Residential dimmers

I took electronics in 9th grade and that was many moons ago.

Question: How do motor dimmers vary from incandescent dimmers in circuitry? Also, how do fluorescent dimmers vary?

And, motor dimmers are usually rated at 3 amps, while incandescent are usually rated at 1000 watts, etc.

I would be interested in hearing the nickel tour on dimmers. The first tour was excellent!

../Wayne

 

[hurk27]

Re: Residential dimmers

Re: Residential dimmers

Here is a good site for catching up"

All About Circuits

 

[hurk27]

Re: Residential dimmers

Re: Residential dimmers

Ed I'm wondering what is causing the instability in Leventon toggle dimmers after they heat up.
I'm thinking they might of tried to put a bipolar cap on the gate that causing an oscillation when the circuit gets warm. the light's will start to strobe. and this is at 80% of the rating or the dimmers.

 

[Guest]

Re: Residential dimmers

Re: Residential dimmers

Wayne,
I have never witnessed the exact dimmer situation you are describing. My experience has been they work; sometimes they hum; sometimes they die. However, I saw a situation where some dimmer switches were knocking out satellite TV. I was staying at a rental estate and sometimes the satellite TV didn't work. It said "finding signal" or such. The owner said it was the weather, but I didn't quite understand that. It was a big place and they had various dimmer switches all over. I found that when certain lights were dimmed (even one) it would take out the satellite TV system. I did not fully troubleshoot the problem as I was there on vacation so I just notified the owner. It was those Leviton sliding preset dimmers that have the little bitty slide for the preset, and then a regular toggle switch for on/off. Do you think the circuit issue you are describing is caused by the same kind of "defect"?

../Wayne C.

PS: I failed to find a link from your link above that would help me in understanding how dimmer switches vary in their circuitry. I was just looking for a brief answer-- nothing too technical-- more of a curiosity. Sorry to bother you.

 

[vanwalker]

Re: Residential dimmers

Re: Residential dimmers

ED thanks for causing more questions
1.are these numbers typical for 1200w loads
2.why do they hummm
THANKS GEO

 

[ctroyp]

Re: Residential dimmers

Re: Residential dimmers

russellroberts:
I don't mean to "steal the thunder" from the excellent help you've received in this forum, but I have run across an excellent source on dimmer's--almost in layman terms.
I have found this site very helpful and would like to hear comments or validity from others on this site.
Regards...

How Dimmer Switches Work

 

[Guest]

Re: Residential dimmers

Re: Residential dimmers

I understand electronic incandescent dimmers and I understand resistor type dimmers.

Without re-learning electronics can somebody chime in with how these dimmers vary in methodology?

1. Household motor "dimmer" (motor speed control) usually limited to 3-amps. Suitable for ceiling fans, etc.

2. Fluorescent dimmers (for standard ballast). What makes them different and why are they so expensive?

Many thanks,

../Wayne

PS: The dimmer link was very straight forward and helpful with the basics of electronic incandescent dimming. It lays out the basics step-by-step. The dimmer page actually starts here:
How Stuff Works: Dimmer Switch

Image property of: http://home.howstuffworks.com

[ September 10, 2003, 10:55 AM: Message edited by: awwt ]

 

[ctroyp]

Re: Residential dimmers

Re: Residential dimmers

Originally posted by awwt:

Without re-learning electronics can somebody chime in with how these dimmers vary in methodology?

1. Household motor "dimmer" (motor speed control) usually limited to 3-amps. Suitable for ceiling fans, etc.

2. Fluorescent dimmers (for standard ballast). What makes them different and why are they so expensive?

Wayne:
I have been trying to get some detailed information from a Leviton engineer on your questions above, but have been unsuccessful so far. I, like you, understand the basics of these items, but want to know more about them. I may contact another manufacturer in the mean time and will repost when I get the info.

 

[Guest]

Re: Residential dimmers

Re: Residential dimmers

While you are checking I'm also interested to know why a motor dimmer is OK for a ceiling fan, but not recommended by the mfg. to slow down a 2-amp attic fan? These motor dimmers are usually rated at 3-amps.

Thanks!

PS: Thanks to the crew here for educating me fully about the functionality of incandescent electronic dimmers.

../Wayne C.

[ September 16, 2003, 07:31 PM: Message edited by: awwt ]