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newbie pot usage


terrakota
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hi,
I'm a completle newbie in electronics
what I'm trying to do is to control the brightness  of a 6v lamp with a 6 volt battery whit a 50k potentiometer,

will i damage the pot because the power dissipated in the pot?
how can i solve the circuit if there's a risk to damage the potentiometer?

i think that when the pot is at near zero resistance the current will be high and power too throw the pot,

thanks for any help and please excuse my poor english

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Hi,
A 50K pot has a value far too high for an incandescent light bulb. Also, the pot is probably rated for only 1/2W over its entire resistive part. So when you turn it so that the lamp is half bright, only a tiny part of it must dissipate the same power as the lamp, burning it.

To dim a lamp with a simple resistor in series, you need something that can survive dissipating power, like a power transistor connected as an emitter-follower, that acts the same as a variable resistor. Since the transistor has current gain, a voltage-divider pot that is feeding it has a very small current that is within the power rating of the pot.

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To control the brightness of a 120V lamp, a pot feeds a small current to a lamp dimmer circuit with a triac in it. The triac switches full power to the lamp at 120 times per second using pulse-width-modulation. For full brightness, the triac switches the lamp on most of the time for its pulses at 120Hz. For dimming, the triac switches the lamp on for a very short time at 120Hz.

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