Light bulbs

[Don Y]

Incandescent lamps only represent a "sizeable" load on startup. Once the filament gets warm, current approaches that of a purely resistive load. And, as startup can (theoretically) occur at any point in the (half) waveform, the chances of the cold filament encountering PEAK line voltage is small. E.g., if the instantaneous line voltage is

20V, then even a 10X reduction in cold resistance makes the lamp look like a *warm* lamp seeing 200V (instead of 170V that it would normally see at peak).

CFL/LED ballasts, OTOH, are *always* reactive -- rarely have power factor correction. So, that "surge" happens every (half) cycle. And, ALWAYS at the peak of the cycle (when the bridge is conducting!).

*Opening* the relay at this time usually poses the biggest risk for contact weld as current is already flowing and wants to continue to flow across the ever widening gap between the contacts. So, you draw an arc and start melting metal.

Engineering is the endless pursuit of the "least bad" solution -- acknowledging that all solutions are "bad" in some way...

[Don Y]

If you are just putting the bulb in a typical fixture with a mechanical switch, youo should have no/few problems regardless of (practical) "size". Do note that different spectra result in different growth patterns. E.g., flowering plants tend to like the "blue-er" wavelengths.

Note that this is not the same as the "color temperature" of the bulb but, rather, specific wavelengths of light in that composite "white".

You have an understated way of describing a ~$70 purchase! :>

[Muggles]

Great! thanks.

[Muggles]

hmmm I read that the "red" wavelength promoted flowering and the "blue" one was more for the foliage?

Understood...

LOL

[Don Y]

I could well have misremembered the details. It's been 40 years since I was trying to grow anything indoors! ;-)

Nowadays, we count on the Sun to provide the optimal mix -- almost unavoidable when the things you're growing are 15+ feet tall/wide!

Getting this level of detail from an OTC product may be difficult. Unless you are specifically purchasing a "grow light"

[gfretwell]

You should be fine. The biggest issue with the 75w equivalent is size. I have seen some "60w only" pendant lights that would not hold the 75w CFL.

[gfretwell]

Next time I am sitting at my bench, bored, I will put a current probe on a CFL and shoot some scope pictures.

[Muggles]

I guess I got lucky because it fit just fine.

[Don Y]

Lots of folks/institutions have already done this. Your friendly neighborhood search engine will save you the headache.

Essentially, the ballast just looks like a cap sitting on the output of a bridge. So, you get all the current flowing through the bridge near the peak of the AC (voltage) waveform and none at other times (diodes being reversed biased as the cap stores a higher voltage than available on the line, at that time).

By contrast, current waveform for incandescent lamp will just look like voltage waveform scaled by some factor representative of the *hot* resistance of the filament.

The implications of CFL/LED and other highly reactive loads on power distribution can be pronounced. *Every* CFL/LED is drawing those peak loads at roughly the same (unfortunate!) time in the waveform. So, the copper wire is just acting as a heatsink for most of the time; not conducting any current!

[Ed Pawlowski]

Enjoy the extra light. You are using only 14 watts. The factor in the rating of the fixture is based on the heat output of the bulb and you are putting out far less with the LED.

For years we use watts for rating bulbs, but in reality, lumen is what counts for brightness. That is how you can compare the given light of incandescent, fluorescent, and LED.

We also like the daylight type bulb too.

[clare]

No. you just need to be using a motion sensor "that uses a neutral"

- in other words a 3 wire device.. If you have a 2 wire device it doesn't matter how smart you are.

[clare]

But with a much lower rate of rize than the solid state stuff.

[clare]

You could if you sequentially switched them. Turning them all on at once would turn the switch into an arc welder if it didn't trip the breaker.

I have 7 9 watt LEDs on a normal switch and you cna hear it when you turn them on..

[clare]

No problem . Use it in good health.

[clare]

I've seen 60 watt ceiling fixtures that wouldn't hols a 40 watt equivalent cfl. without changing to a longer glass.

[Muggles]

I sure do love the extra daylight from that bulb with so many cloudy days in the fall and winter.

[Muggles]

Thanks for the info!

[Don Y]

Move someplace sunnier! :>

(seriously)

When I moved here (S.Az), I saw a sign in the airport claiming "360 days of sunshine/yr" and laughed. "Yeah, sure". I've since learned that it is pretty close to the truth! So much so that cloudy/overcast days are REALLY noticeable!

[Don Y]

Yup. You're essentially driving a (momentary) short as all those caps soak up charge!

[Muggles]

hmmm retirement is creeping up soon, so, who knows?