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Resistance on a Flexdrive?

Wolfman29

Wolfman29

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Hey everyone.

Does anyone have a spare flexdrive lying around that they can measure the pot's max resistance on?

I am curious to see what he does for that, because right now I am looking to design a pot-adjusting driver, and I can't seem to find any SMD pots that are around the 1Ohm range... anyone have any ideas?
 





Don't need a tiny pot turner :P I need a tiny pot! The thing is, I can't think of a way for the FlexDrive to be able to adjust such a huge range of currents so evenly without having a small resistance pot.... You know what I mean?
 
I'm not sure what you mean but I do have some tiny pots like the one used on the flex drive, these came off of a 12x sled, interested ? I'll send em or if you have an old 12x sled laying around look on it.

1.0 ohm pot is really small I have never heard of one before.
 
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Hm. Well, I took a look at the pots on the LPC sleds and they are about 500kOhm. What are the pots max rating on the 12x sleds?
 
Dang you know harvesting diodes is easier than harvesting tiny pots :crackup: but it can be done you just have to be very careful and sneak up on them from behind :eg:



And just when I thought that was enough I couldn't get the meter leads on them cuz they are so tiny and the leads seem so large, so I had to solder tiny wires on so I could get a meter reading.
It didn't matter where the wiper was so I must have been on the right two leads, one was just above 700 ohm one at 726 ohm and the third was to 789 ohm.





Wolfman29 said:
Hm. Well, I took a look at the pots on the LPC sleds and they are about 500kOhm. What are the pots max rating on the 12x sleds?
Click to expand...
 
Wolfman29 said:
Don't need a tiny pot turner :P I need a tiny pot! The thing is, I can't think of a way for the FlexDrive to be able to adjust such a huge range of currents so evenly without having a small resistance pot.... You know what I mean?
Click to expand...

I think with the buck-boost topology used the pot isn't on the high current path, but on a feedback loop that allows the current to be changed with those range resistors.

If you measure those pots, you would probably get an approximate value since the tolerances of those things are high, 10%, 20%, or higher.
 
I've been messing with pots lately myself. i can't find any smaller than 100 ohms that can handle a decent amount of wattage, are cheap, and that are really tiny. This is the last one I tried, but it's only rated for .1W. Unfortunately I broke off one of the contacts before I could get done completely testing it:

http://www.mouser.com:80/Search/Pro...Evirtualkey65210000virtualkey652-TC33X-2-101E


These cost a bit more but look about the same:

http://www.mouser.com/ProductDetail...=sGAEpiMZZMuCof0LOVDlLJpuk5YfHxcKeX/cvHWhje0=

http://www.mouser.com/ProductDetail...=sGAEpiMZZMuCof0LOVDlLA8vMoU7s8dkRccZUdl19uE=

Edit:
Actually, I think I might give these two a test run. Rated at 20 ohms, .25W. Unfortunately they are a lot more expensive and a bit larger:

http://www.mouser.com/ProductDetail...=sGAEpiMZZMuCof0LOVDlLO5q0jBuX1uI1SpFKWYAtXI=

http://www.mouser.com/ProductDetail...=sGAEpiMZZMuCof0LOVDlLMSiKQWB1gKmCG/pZabhuIo=
 
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