Variation resistance on voltage of a halogen bulb

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Variation resistance on voltage of a halogen bulb




by Christophe » 12/01/09, 16:20

As part of these measurements on a universal motor as a generator: https://www.econologie.com/forums/moteur-uni ... t6819.html I made some measurements that allowed me to draw the curve of variation of the resistance according to the voltage and the load (the 2 being bound) of a halogen bulb of 12V. It's interesting so I put it in public.

Resistance of the 12V halogen bulb according to the voltage:
Image

Resistance of halogen bulb 12V depending on the load:
Image

We can not say it enough: except for exception the electrical resistance of a body varies with the temperature (and therefore the charge of the bulb), the hotter it is, the more it is resistant (and luckily if not all would burn!) !

Which is all in all quite logical: more molecular excitation = less "passage" for the eletrons ... obviously there are some exceptions I think!
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by elephant » 12/01/09, 17:45

This is not what we call the Joule effect, by chance?
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by Other » 12/01/09, 17:52

Hello

Only the old carbon filament bulbs do not have this answer.

takes an 100W lamp and measures its resistance to cold
and turns on the normal voltage and amperage measurement and voltage resistance increases considerably.
It is also for this reason that the lamps of long longevities that actually work under voltages lower than their desing are not economical, they give less light, for the energy they consume they have more calorific losses.

Maintaining those who use a dimmer to lower the intensity of a light (made the calul voltage at the terminals of the light and amperage in the light)

Andre
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by Christophe » 12/01/09, 18:01

Arf trap question!

For me the joule effect is the opposite: creation of heat by a circulation of an electric current. Obviously there is more resistance, so T °, ​​there is more joule power ... it's a vicious circle.

The 2 are therefore linked but I do not think that the rise of the electrical resistance under the effect of the heat can be called joule effect (the reverse yes by cons)
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Re: Variation of resistance on voltage of a halogen bulb




by paul_f5hpq » 17/04/20, 22:39

Hello,
a filament lamp is a resistor with a positive coefficient depending on the voltage across its terminals (VDR).
https://fr.wikipedia.org/wiki/Varistance
Indeed, the more it heats the more its resistance increases.

A diversion is made to convert this oddity into a hot wire anemometer. To be supplied with current only.
PAs bad literature on the subject, you will understand better suddenly the use of the joule effect for the measurement.

A bit like CTP and unlike negative CTN. https://fr.wikipedia.org/wiki/Thermistance
You can't use it to measure the temperature of course.

Good research!
Pol
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Re: Variation of resistance on voltage of a halogen bulb




by Evaluation » 18/04/20, 01:03

paul_f5hpq wrote:You can't use it to measure the temperature of course.

Why not ? if supplied with constant voltage.
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Re: Variation of resistance on voltage of a halogen bulb




by paul_f5hpq » 18/04/20, 20:42

Hello Evaluation,
How would you measure the temperature with a bulb supplied with constant voltage?
Can you develop the principle?
Kind regards.
Pol
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Re: Variation of resistance on voltage of a halogen bulb




by Evaluation » 19/04/20, 07:37

paul_f5hpq wrote:Hello Evaluation,
How would you measure the temperature with a bulb supplied with constant voltage?
Can you develop the principle?
Kind regards.
Pol

By measuring the variation of the current.
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Re: Variation of resistance on voltage of a halogen bulb




by Macro » 19/04/20, 08:21

The calculators of diesel engines measure the combustion temperatures, using glow plugs (a simple resistive element) they manage to determine injection faults with this principle ... So it must be quite possible
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Re: Variation of resistance on voltage of a halogen bulb




by izentrop » 19/04/20, 08:28

Evaluation wrote:
paul_f5hpq wrote:Hello Evaluation,
How would you measure the temperature with a bulb supplied with constant voltage?
Can you develop the principle?
Kind regards.
Pol
By measuring the variation of the current.
In general it is the case but by measuring a tension. : Wink:

The supply is always constant, whether it is a battery with negligible internal resistance compared to the measurement or from the mains followed by a stabilized voltage supply.
The classic diagram is a resistance in series with the thermistor, the measurement is made between the mass, common point of the power supplies, and the junction point.
Image The resistance is calculated so that the current at nominal temperature is centered on a "linear" range.

The amateur will use the arduino to measure http://f4cvm.free.fr/arduino/shields/ca ... re_ctn.htm

PS: for the glow plug it must be the same principle, but the measurement must be done with a hall effect current sensor https://fr.wikipedia.org/wiki/Capteur_d ... effet_Hall
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