[sdiy] 1/8" shaft pot comparison: Honeywell/Clarostat vs. Vishay & Bourns stiffness

[Robin Whittle]

Hi "megaohm",

You wrote, in part:

> The Bourns 51 series I like. I haven't noticed any stiffness but
> perhaps the conductive plastic pots are stiff. I have cermet ones.

"Stiff" is a subjective assessment.  I want to use these pots with
9mm collet knobs and to have people turning them quickly, such as
for musical expression moment-to-moment.  This is rather different
from judiciously setting the gain on a mixer, when a slow movement
with a relatively stiff pot might be best.

I showed the Bourns and the Honeywell Clarostat pots to a friend
recently, thinking she would notice the difference in feel.  Her
initial response was that she liked the Bourns best - she felt it
was more substantial.

I think there is a perception that things which are easy to move are
also flimsy and likely to break.

When I explained my reason for preferring the Clarostat pots, she
understood - especially after I explained I had pulled one apart and
found it to be very solid inside.

I just tested the pots, with a collet knob wrapped to 1cm radius
with insulting tape - and some some dental floss wrapped around it
reducing the force on some digital scales.   Figures are gram
centimetres.  Divide by about 100 to get Newton centimetres.

These are all 1/8" shaft conductive plastic pots.


Honeywell (Clarostat)  308 (Digikey recently)         11 - 12

   Very smooth and light.
   Probably too light for some folks.

http://sensing.honeywell.com/index.cfm/ci_id/140301/la_id/1/pr_id/109327.htm


Bourns  51/53                                         80 - 120

   Noticeably more resistance at higher rotational
   velocities, which gives the higher figure.  This
   is a "viscous" kind of friction.


Old Mexico Spectrol 148-SXN48S103SP 10 0320 (2003?)   20 generally

   Became lighter at one end, down to about 13.

   http://www.wavemakers-synth.com/motm/chiclets.html
   except mine has 1/8" shaft.


New Vishay "Spectrol" 148 SXN48S103SP 0811 (2008?)    105 to 120
Czech Republic (RS Components).

   This had a dry friction sensibility, a feeling of
   dragging something across a somewhat rough surface.
   Torque did not appreciably increase with velocity
   as it did with the more "viscous" Bourns pot.

http://au.farnell.com/jsp/level5/module.jsp?moduleId=en/388662.xml


There is a 10:1 range of torque here - maybe more for the bump at
the end of the new Vishay "Spectrol" pots or for the Bourns when
turned fast.

  - Robin