Where are they used? Was there a second set of windings on the rotor, armature, stator, field laminations? Is there a circuit available online or of a work-alike?
Sounds like a guy from the old days" of car generators. This was common then.
1st and 5th not good. A friend lent me a car when my '70 MGB got vandalized, was something like a '70 Toyota Celica with only 2nd and 4th. for a couple of weeks. The MG shifted fantastically well.
SW
Just a nitpick, but technically, the resistance goes up as the _temperature_ increases. :-)
Cheers! Rich
Gently stroke them while saying romantic things.
Hope This Helps! Rich
Does anyone know what this curve looks like? I would actually like a V vs. I curve for a typical incandescant. Googled some, wiki has an inneresting table on incandescant efficiency
Presumably a similar curve would arise from both AC and DC?
Did we change the subject to fluorescent bulbs now?
We always laughed about the ones that didn't want to start, in those terms.
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Hope This Helps! Rich
Josepi wrote:
The ambient temperature may have a slight effect on that curve also since as, as Rich so graciously pointed out, "the resistance goes up as the temperature_"
Perhaps lamp manufacturer sites?
Presumably a similar curve would arise from both AC and DC?
Josepi wrote: Lightbulbs are not a linear load. Their resistance goes up as the voltage increases. You would need to monitor the voltage and the current to get anything useful.
That would give you the data for that one bulb. There are manufacturing variations from lamp to lamp. For instance: HP used a small lamp in their early audio generators to control the gain. They had to be hand selected to get the lowest distortion in each generator.
(...)
From the context of the conversation, I assume that your goal is to use an incandescent bulb as a voltmeter.
Is that correct, PV?
--Winston
Yep. Those were called "barreters". They were in the feedback loop of a Wein bridge oscillator. As the amplitude of the signal grew, so did the resistance until the loop gain became exactly 1 and amplitude stabilized at a steady-state value.
I have a TS-382F I am rebuilding. It is a military version of the early HP 200 series, with the addition of a frequency meter. All the 'bathtub' capacitors are leaky, and a few 2W 5% resistors are burnt. All metal tubes in the 'Wein bridge' and output amp.
Close.... as a wattmeter..... :) I monitor the voltage, and based on the applied voltage, impute power. But I need to know resistance as a function of V, which a V vs I curve would yield.
In the other thread I started specifically on this question, it seems the data/links others provided will provide this.
Iow, if you have a 60 W bulb glowing away at 120 V (its rated voltage), you know it's drawing 60 W. But what if the voltage is 100? or 75? or 150?
Yep even Heath Kit used the same thing. I built a number of them for the Coyne Radio and TV school in 1950 after I graduated there I worked for the school for about 6 months. Of course the 7 1/2 W bulbs were just the ordinary "nite light" bulbs but they worked just fine. Havent heard (or read) that term "Wein Bridge" for a very LOOOOOOOONG time. :-) ...lew...
Just to complicate things, read the voltage on the bulb. The long life units are sometimes rated at 130 volts and the cheap one at 115 volts and 117 volts. Some may be 110 volts depending where they are manufactured. The Chinese think we are all short and short on voltage too....LOL
I am not sure I would go by the rating of the bulb unless 10% error is a good tolerence.
Are we pushing your accuracy requirements to new heights or what?....LOL
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In the other thread I started specifically on this question, it seems the data/links others provided will provide this.
Iow, if you have a 60 W bulb glowing away at 120 V (its rated voltage), you know it's drawing 60 W. But what if the voltage is 100? or 75? or 150?
Nice one!!
According to the second link the current curve is not perfectly linear but very close by the few specimens I checked. Buggers used a log scale one direction though. GRRRRRR...
Anybody scratch their LCD screen with a metal ruler?
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50% voltage the lamp draws 69% of normal current, so the power would be 34.5%, rather than the 25% you would get for a fixed resistance. For V=150% the current is 125%, yielding 187.5% of the nominal power.
(...)
Why not use a nice, linear Hall Effect current sensor?
ACS758ECB-200B-PSS-T
This one acts like a 10 milliohm sense resistor but offers only 100 micro ohms of actual resistance to your circuit.
-Requires only a small DC power supply and a couple reference resistors to sense up to +-200 A with your multimeter.
--Winston
I've seen plenty of Chinese bulbs marked for 130 volts.
Firstly There are no light bulbs made in N.America.
Secondly They are commonly used for rural applications and exit sign where voltage surges are common and long life is desired, respectively.
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--------------- Josepi wrote: Just to complicate things, read the voltage on the bulb. The long life units are sometimes rated at 130 volts and the cheap one at 115 volts and 117 volts. Some may be 110 volts depending where they are manufactured. The Chinese think we are all short and short on voltage too....LOL
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