On car and home HiFi I have a knob to control the volume. It is not a
variable resistor - it turns infinately. I guess is somehow creates a
proportional and directional signal to the amplifier - but what is in the
mechanism and how does it work?
They now use an opto-coupler, basically they (two pairs, so they get a
direction) shine a beam of light through a segmented disk. The output
of which controls an IC to vary the volume. They are used on many
things - volume controls, tuning controls, microwave ovens and etc..
Anything which needs a rotary control to change a value.
Not all. Before optical some used multiple sliding contacts, and become
annoyingly noisy. I had a mini system and even a Sony walkman with
issues like this where at a random point the contacts would become open
circuit and assist in digitally creating a gain setting not too distant
from the number 11.
Then you have tinnitus, lost teeth and sore joints for a few hours after
the unscheduled urgent launch to explore the galaxy far far away beyond
the ceiling in your room....
On Wednesday, 30 November 2016 12:49:03 UTC, Dave Plowman (News) wrote:
A cheap and popular method is still used by mice, well not lots of mouses b
ut optical mice still use an LED. They don't use a light chopper but 'take'
a picture of teh surface table and use that and subsequent movments to wor
k out it;s position. I;'m not sure if hall effect sensors are still used fo
r this sort of thin unless in a specialsed area of use.
Not unlike a stepper motor but with the coils connected to a sensor that
determines direction and rate of rotation from the clicks.
Prior to that there were absolute position encoders using Grey codes
that would allow you to read the angle (but costly to do at high
precision). Telescope drives and CNC tools use them for feedback.
When I built one back in the 70's the cheapest was a light source, a 50
50 slotted wheel., and two photo detectors, plus a bit of CMOS logic
Coils and magnets are a no no as they don't detect *very slow* movement.
Truth welcomes investigation because truth knows investigation will lead
to converts. It is deception that uses all the other techniques.
Often they also have a push in action to fix the volume from getting moved
or in some cases to set it so it comes on at that volume when turned off.
Too much cleverness being built in to something that does not really need
it in my view.
I have one of these on a radio to move between preset stations, but the
clickery bit is knackerd and now and again it has a mind of its own and
moves between stations in a demented and anti social manner.
This newsgroup posting comes to you directly from...
Brian - bear in mind that this sopisticated changes are to benefit the
manufacturer - not the user. Think how many potentiometers were saved by
making remote control standard!
Many radios in cars have a setting to the switch on volume level - hidden
in the settings.
That is more than amusing. Its the truth.
A quality potentiometer wired into a board probably adds £1 to its
final cost, and is a source of wear and short product life.
Trying to get rid of mechanical things has been a drive in electronics
ever since valves went out of fashion.
I am working on a hobby project involving a piece of digital electronics
that I want to control via loads of pots.
I COULD use a mouse or a touchscreen, but I like the old fashioned feel
Using that as control inputs will be the single most expensive feature
in the design.
Mine just reverts to where it was when I switched off.
Gun Control: The law that ensures that only criminals have guns.
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