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POT burning/candle-like smell

t101

Jul 10, 2022
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Hello,

Am testing a POT on a breadboard and after turning it on approximately 20secs later a tell-tale burning smell occurs. The setup is easy enough: breadboard powered by single Voltage source (14v), and the variable resistor. When I set the wiper to maximum I get 7 Volts signal out; when I have wiper set to minimum the output is 14 volts.

If I am facing the POT - the left lead goes to hot; the middle a wire setup for probing by voltmeter and the right to ground. Is this setup correct? Obviously something is getting scorched.
 

t101

Jul 10, 2022
24
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Jul 10, 2022
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Bourns Incorporated
POT 1K OHM 1/5W CARBON LINEAR
1k Ohms
Power (Watts)
0.2W, 1/5W

Thanks
 

kellys_eye

Jun 25, 2010
5,116
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5,116
Even wired correctly it is on the limit of its wattage capability.......
 

t101

Jul 10, 2022
24
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Jul 10, 2022
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POT2.jpg
Sounds like it's wired incorrectly to me....
Here a few snaps. Facing the POT CCW view the left terminal should be the Vcc, the middle term to "output" and the right to ground. My circuit is super simple using a 14V voltage source. Ive tested the component after the smell, and its running in range using just my voltage meter -- so hopefully no permanent damage.

Moderators note : removed double picture
 
Last edited by a moderator:

bertus

Moderator
Nov 8, 2019
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2,726
Hello,

What is the powerrating of the pot?
At the moment it will have to dissipate (14 Volts X 14 Volts) / 1 K = 0.196 Watts

Ohm's_Law_Pie_chart.png
Bertus
 

t101

Jul 10, 2022
24
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Jul 10, 2022
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Thanks, 10k POT is thumbs-up

power rating for my POT in question is
0.2W, 1/5W
from data sheet

P = E^2/R = (15 x 15)/1.2K (as you stated)
= (15^2)/1200 = 0.188 W (close to .2W above)

By you increasing the resistance on the order of 10 likewise you double the R in P=E^2/R thereby reducing the P to a more reasonable Power that doesn't operate on the cusp of the components max specifications.

P = .0225 at POT = 10K. (check my math)

I have connected the POT correctly so I believe. No more odor.
Want to post that with some labeling missing before.
 

t101

Jul 10, 2022
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Jul 10, 2022
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Had the POT using the thumb screw almost at max - started smoking. Am acquiring 10k POT.
 

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roughshawd

Jul 13, 2020
254
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Jul 13, 2020
Messages
254
Maybe you have the wires connected in the wrong polarity. Reverse the current.
pots are bogus. I hate them. First you are trying to run a linear projection on an oscillator device, it just won't work. Electricity only travels in one direction. The word oscillator is used to identify circuit exchange. (unless your experimenting with draws and charges). The pot is either too small or your current is too high. This tech is a one way show. Smoke is usually not a good thing. You will find that if the power goes in the wrong direction, things will melt burn or explode, including the tech.
 
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