Smoking Pot

[Alex C]

This is sort of related to Deep Blue's  â€œFried pot?” post, but I thought that a new topic with this name would get more attention.

A few years ago I cooked up a fan system for my paintall mask, using a 12 volt fan from radio shack (ripoff) and eight AA batteries soldered and hot-glued together.  I didn’t have a switch at the time to turn the power on and off, so I used a tiny cheapo pot salvaged from a crappy danelectro mini pedal.  It worked fine, turn it one way- on, turn it the other-off.  Then I tried to experiment with other pots (full-size alpha-the good kind).   This time when I hooked up power, there were sparks and the pot was smoking like crazy.  There were more sparks when I turned it, and it still smoked more.  What’s going on here?  I’ve used the same pots in my AX84 P1 amp, with much higher voltages than 12v.  Is it current?  I don’t quite grasp the entire concept of current yet, I know the water analogy where it’s the amount, and voltage is like the pressure, but I’m still sort of confused.  Any ideas?

[C Bradley]

It's the current. AA's will put out over an amp each when short circuited. So, if those Alpha's are 1/4 watt, you're putting close to 8A through it and it's burnin' up. Your P1 isn't putting more than a few milli-Amps of current through it's pots.

Chris B

[Andy]

mmmmmm smoking pot  aww maaaaaannnnn

[zachary vex]

It's the current. AA's will put out over an amp each when short circuited. So, if those Alpha's are 1/4 watt, you're putting close to 8A through it and it's burnin' up. Your P1 isn't putting more than a few milli-Amps of current through it's pots.

Chris B

eight AA cells in series forming 12VDC will NOT deliver 8 amps.  if they were in parallel, maybe, but the total delivered current in series will DROP from the maximum available from one cell as their internal resistance begins to add up.

[Ge_Whiz]

Essential information: what's the resistance of the pots you have used?

[C Bradley]

It's the current. AA's will put out over an amp each when short circuited. So, if those Alpha's are 1/4 watt, you're putting close to 8A through it and it's burnin' up. Your P1 isn't putting more than a few milli-Amps of current through it's pots.

Chris B

eight AA cells in series forming 12VDC will NOT deliver 8 amps.  if they were in parallel, maybe, but the total delivered current in series will DROP from the maximum available from one cell as their internal resistance begins to add up.

My bad Zach! :oops: I must have had a brain fart when I was writing that. :roll:  I know better than that. Depending on the resistance of the pot, it could be up to 12W on a device that's only rated for 1/4W to 1/2W.   I got my answer half right, it is the current burning it up.  :wink:

[Alex C]

I used a 1M Alpha 24mm 1/4 watt pot.

Those are good explanations, but why didn't the Danelectro mini pot fry?