Nedd cheap(er) panel mount optical encoders

[Robert Latest]

Hi folks,

I'm having to repair a device that has six 1000ppr panel-mount optical
quadrature encoders. The encoders are failing more and more because the
device is a box which gets dropped on concrete floor a bit too often.

I'm looking for replacement encoders but at that resolution (500ppr would
do, too) things get really industrial-grade and ball-beared with
associated cost ($100+ apiece). The encoders are hand-operated with knobs
so precision is not an issue.

Suggestions, anyone?

bob

 

[Roger Hamlett]

Hi folks,

I'm having to repair a device that has six 1000ppr panel-mount optical
quadrature encoders. The encoders are failing more and more because the
device is a box which gets dropped on concrete floor a bit too often.

I'm looking for replacement encoders but at that resolution (500ppr
would
do, too) things get really industrial-grade and ball-beared with
associated cost ($100+ apiece). The encoders are hand-operated with
knobs
so precision is not an issue.

Suggestions, anyone?

bob

If 'precision is not an issue', what are you doing using a device that can
potentially resolve 4000 points round a circle?. One reason the devices
have ball races, is because any shift in the shaft, will be seen as an
encoder movement, and with a typical encoder of this type, a sideways
movement of just 0.01mm, will be seen as a step. Consider if you could
provide the input knobs and shafts yourself?. If so, you could use much
cheaper 'bearingless' encoders, like the push-on ones from US Digital.
Some of these are under $20 each. US Digital do some types that sound
significantly cheaper than your current units, with the 'H1' (ball bearing
unit up to 1250ppr), coming in at $57.
If you could come down even lower on the resolution (unless the knob is
very large, do you really think people can generate/resolve movements
finer than perhaps 1 degree?), some of the digital potentiometer units
(usually 90ppr, to give 1 degree resolvable), are also significantly
cheaper.

Best Wishes

 

[Luhan Monat]

If 'precision is not an issue', what are you doing using a device that can
potentially resolve 4000 points round a circle?. One reason the devices
have ball races, is because any shift in the shaft, will be seen as an
encoder movement, and with a typical encoder of this type, a sideways
movement of just 0.01mm, will be seen as a step. Consider if you could
provide the input knobs and shafts yourself?. If so, you could use much
cheaper 'bearingless' encoders, like the push-on ones from US Digital.
Some of these are under $20 each. US Digital do some types that sound
significantly cheaper than your current units, with the 'H1' (ball bearing
unit up to 1250ppr), coming in at $57.
If you could come down even lower on the resolution (unless the knob is
very large, do you really think people can generate/resolve movements
finer than perhaps 1 degree?), some of the digital potentiometer units
(usually 90ppr, to give 1 degree resolvable), are also significantly
cheaper.

Best Wishes

Mechanical shaft encoders are commonly used as input devices. I pay
about $3 each in small quantities. Check Digi-Key and Mouser.

 

[Steve Kavanagh]

unless the knob is
very large, do you really think people can generate/resolve movements

finer than perhaps 1 degree ?

When it is reasonably large (say 2 inches diameter) it is amazing how
well a round knob can work for fine control, if there is some feedback.
An experienced radio operator can tune an SSB receiver within about
1/1000 of a turn (around 10 Hz resolution at 10 kHz/turn, for example).
I suspect a motion control system might do even better, where the eyes
are used for feedback rather than the ears.

Steve

 

[Robert Latest]

If 'precision is not an issue', what are you doing using a device that can
potentially resolve 4000 points round a circle?.

Ah, this is interesting: The computer to which the current
encoders are connected registers 1000 counts per turn, which is
why I specified 1000 ppr. But I guess 250 is enough for me,
then.

"Precision is not an issue" is, of course, an unprecise
statement. What I mean is that I can live with possible loss of
counts or similar errors. To my surprise I have found that 1000
steps per revolution is not completely overblown for a
hand-operated device with visual feedback, but half the
resolution is enough.

One reason the devices
have ball races, is because any shift in the shaft, will be seen as an
encoder movement, and with a typical encoder of this type, a sideways
movement of just 0.01mm, will be seen as a step.

I guess that's the reason why it is hard to find the combination
"many steps with plastic mechanics".

If you could come down even lower on the resolution (unless the knob is
very large, do you really think people can generate/resolve movements
finer than perhaps 1 degree?)

Absolutely. You'll be surprised when you try it (I was).

robert

Best Wishes

Thanks!

 

[Robert Latest]

When it is reasonably large (say 2 inches diameter) it is amazing how
well a round knob can work for fine control, if there is some feedback.
An experienced radio operator can tune an SSB receiver within about
1/1000 of a turn (around 10 Hz resolution at 10 kHz/turn, for example).
I suspect a motion control system might do even better, where the eyes
are used for feedback rather than the ears.

Exactly, and the application in this case _is_ a motion control
system.

robert

 

[Spehro Pefhany]

Hi folks,

I'm having to repair a device that has six 1000ppr panel-mount optical
quadrature encoders. The encoders are failing more and more because the
device is a box which gets dropped on concrete floor a bit too often.

I'm looking for replacement encoders but at that resolution (500ppr would
do, too) things get really industrial-grade and ball-beared with
associated cost ($100+ apiece). The encoders are hand-operated with knobs
so precision is not an issue.

Suggestions, anyone?

bob

Try US Digital


Best regards,
Spehro Pefhany