Dimmer switch incompattable with non-incandescent light bulbs

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Fritz t. Cat
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I just tried for the third time to replace the dimming light in the dinette with a more efficient bulb. It flashed and dimmed to around the power of a candle. The other two tries were a compact fluorescent from a local hardware store and a different led bulb from DHGate. This time an led bulb in another room also quit.
So I think that this condominium that was fixed up to sell has at least one substandard dimmer switch, that blows out anything but an incandescent bulb. The fix is clearly to buy a new switch from a reliable store and try again. I have studied electromagnetic compatibility, but this caught me by surprise. It does not affect the radio, or noticeably the wireless network. From what I know about regulations, I guess that this switch was smuggled into the US.

dave_
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Sounds strange. Are your

Sounds strange. Are your bulbs actually made for the use with a dimmer? Many are not.

Woody
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dave_ wrote:Sounds strange.

dave_ wrote:
Sounds strange. Are your bulbs actually made for the use with a dimmer? Many are not.

+1 – I’ve seen “do not use with dimmer” on many non incandescent bulbs.

texaspyro
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Fritz t. Cat wrote:I have

Fritz t. Cat wrote:
I have studied electromagnetic compatibility, but this caught me by surprise.

Electromagnetic compatibility has NOTHING to do with whether your dimmer and bulb are compatible… it has to do with your electronics emitting signals that mess with radios and TVs).

Some bulbs are not dimmable (very few CFLs are, maybe half the LED bulbs are). Some dimmers will only work with incandescent bulbs or require a certain minimum load to work.

I have over 300 bulbs in my house (http://budgetlightforum.com/node/9179) , all LEDs, almost all on dimmers, almost all bought from a company that re-sells returned items from places like Home Depot (at less than 20% of retail prices). I suspect that most were returned because of dimmer compatibility issues.

Fritz t. Cat
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dave_ wrote:Sounds strange.

dave_ wrote:
Sounds strange. Are your bulbs actually made for the use with a dimmer? Many are not.

They were listed as such, and based on my experience with flashlights, it would be highly unlikely that two would be so inaccurately described. To clinch it, I recall that the compact fluorescent I bought at a local hardware store also failed. I tried them all in another socket, but only afterward when they were already broken.

Fritz t. Cat
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Electromagnetic compatibility

texaspyro wrote:
Fritz t. Cat wrote:
I have studied electromagnetic compatibility, but this caught me by surprise.

Electromagnetic compatibility has NOTHING to do with whether your dimmer and bulb are compatible… it has to do with your electronics emitting signals that mess with radios and TVs).

That included working on the electrical system of the Bradley fighting vehicle. It has a military standard that covers the quality of the electricity and the ability of the devices to function with it and withstand large spikes, like when the turret is rotated or the gun fired. The electronic devices need to filter their power or they will get burned up by the first voltage surge. It also included interference problems in the power systems in laboratories.

What actually happened here was more complicated. An other led bulb in another room also failed and the nightlight in the bedroom changed color modes. Apparently there was an oscillation set up between the dimmer and the bulb. I hope my neighbors didn’t lose anything.

At least the older power control devices use silicon control rectifiers (SCRs ), (also known a thyristors because they are the semiconductor equivalent of a thyratron). Variable voltage transformers are too expensive, and variable resistors are too inefficient. So they are active devices that can oscillate. They always need to be used with filters, because they work by switching on at some point in the voltage cycle so that only the desired amount of power is passed. They need to switch fast in order that the first part to switch is not burned out before the voltage across it drops. Of course ones sold in the US should comply with FCC or whatever regulation, but this condominium was fixed up cheaply to sell and has problems like the toilet being out of plumb and light sockets that don’t fit the bulbs well, so these are probably non-conforming switches that were bought cheaply or smuggled in.

gerald_clark
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Your foil hat is leaking.

Your foil hat is leaking.

dave_
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I lack creativity

I lack creativity sometimes.
How in the world would you get a standard leading edge SCR dimmer to resonate with it’s load?

comfychair
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http://www.youtube.com/watch?

http://www.youtube.com/watch?v=w3qFdbUEq5s

edit: Metallic oxide salts in the water supply killed the bulbs, obvs.

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Fritz t. Cat
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dave_ wrote:I lack creativity

dave_ wrote:
I lack creativity sometimes.
How in the world would you get a standard leading edge SCR dimmer to resonate with it’s load?

Well, don’t know enough about these devices to pin it down, but these are two active devices from questionable and distantly related sources. The light is programmed to act sort of like a resistive load, on the time scale of the line frequency, but that is done with active control that has bandwidth limitations. The dimmer has a volt meter that it reads to decide when to open the scr, but it is designed and tested with passive loads. It should have a filter after the active part to smooth things out for both it and the load, but if it is substandard as I suspect it is the filter is minimal or absent. So we have two devices including amplifiers closely coupled with no significant lossy elements. SCRs by nature make current spikes of about the size of the line voltage and with bandwidth limited only by series inductance that is expensive and therefore minimal.

texaspyro
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There are no voltmeters or

There are no voltmeters or amplifiers inside of any lighting dimmers you are ever likely to see. Also, no SCR’s these days… they use triacs. The circuit is very simple. Google is your friend…

dave_
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Yeah, even in the fancier

Yeah, even in the fancier devices with features like a touch sensor or remote control, the firing voltage of the triac is still directly derived out of the line voltage.
Introducing noise to the grid from hard switching is one thing, but actually having multiple zero crossings to turn off/of the triac at any higher frequency than that from your grid, that doesn’t sound realistic to me.

There may be a more likely reason for your problem.
Over here, we had sometimes problems with the now obsolete TNC networks (grounding without a special grounding conductor.) Breaking of the neutral conductor would lead to strange effects, including random damage and death of electronic devices.
I don’t know much about US power grids (and those SWER systems with pole transformers look dodgy to me anyway Tongue), but maybe a defect in your house distribution could cause such effects?
An experienced electrician familiar with those systems might know that.

Fritz t. Cat
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texaspyro wrote:There are no

texaspyro wrote:
There are no voltmeters or amplifiers inside of any lighting dimmers you are ever likely to see. Also, no SCR’s these days… they use triacs. The circuit is very simple. Google is your friend…

I said at least old ones.

Fritz t. Cat
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dave_, I think it is the

dave_, I think it is the dimmer, because that is what may be sub-standard and because led and compact fluorescent bulbs work in other dimming lights here. It could be that the dimmer just puts out constant spikes and it is the bulb’s reaction to those that caused the other problems.

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