The volume control on the radio in my car is not like the older controls which come to a hard stop at the end of their range. This one continuously variable even when the volume reaches it's highest/lowest value. When the knob is turned, there is sort of a tactile feedback that makes you believe there are detents in the control. What are these puppies? Can I buy them? What do I search for?
Any enlightenment will be appreciated.
Vic
Volume Control???
Volume Control???
Vic Fraenckel
KC2GUI
windswaytoo ATSIGN gmail DOT com
KC2GUI
windswaytoo ATSIGN gmail DOT com
A classic volume control is a variable resistor. A wiper arm swings an arc, rubbing agains a resistive material, changing the point of contact, and hence the ratio of the two parts of the resistive divider. The device truely mimics its schmatic representation.
The control you are describing is generally implimented digitally. One can use a smart rotary shaft encoder, with built in electronics, to generate an Up pulse and a Down pulse, just as if one had used two push button switches for the volume instead of a rotary type knob interface.
Depending on the design, a pulse, and an Up/Down bit may also be provided, instead of two pulse streams.
Early versions used gears, cams, and cogs to physically bump either an up or down push button switch, depending upon the rotation of the shaft. A 'dumb' digital switch, with debouncing being done by the micro.
The detent is simply physical, and gives a nice feel to the knob, and defines the arc per pulse. A spring pushing a ball bearing against a disk with indentations on the circumference is one method of providing the tactile feedback.
With micros on the back end of the device, digital pulses are much easier and faster to process, rather than having an AtoD reading a variable resistor input. Also, true variable resistors get worn, and scratchy, making the volume adjustment noisy, and imprecise, as the devise ages.
While you search for one you like, you can mimic the input with two push button switches, one for up, the other for down. The micro controls a digital variable resistor to control the amplifier gain.
JC
The control you are describing is generally implimented digitally. One can use a smart rotary shaft encoder, with built in electronics, to generate an Up pulse and a Down pulse, just as if one had used two push button switches for the volume instead of a rotary type knob interface.
Depending on the design, a pulse, and an Up/Down bit may also be provided, instead of two pulse streams.
Early versions used gears, cams, and cogs to physically bump either an up or down push button switch, depending upon the rotation of the shaft. A 'dumb' digital switch, with debouncing being done by the micro.
The detent is simply physical, and gives a nice feel to the knob, and defines the arc per pulse. A spring pushing a ball bearing against a disk with indentations on the circumference is one method of providing the tactile feedback.
With micros on the back end of the device, digital pulses are much easier and faster to process, rather than having an AtoD reading a variable resistor input. Also, true variable resistors get worn, and scratchy, making the volume adjustment noisy, and imprecise, as the devise ages.
While you search for one you like, you can mimic the input with two push button switches, one for up, the other for down. The micro controls a digital variable resistor to control the amplifier gain.
JC
I'd guess that those volume/tuning knobs on consumer electronics provide (1) a series of pulses as you turn the dial; (2) a CW vs. CCW indicator. Likely the two are combined in some manner, i.e., two pulses, and the first-occurring indicates direction. Or some such. Might be done with opto-isolators for long life.
This Wikipedia article explains the various encoding techniques for rotary encoders.
A quadrature encoding is in effect a two-bit gray code (00, 01, 11, 10) which may repeat multiple times in 360 degree rotation. For example some motors have a built in encoder that may have 256 and 512 counts per revolution. The direction of rotation is determined by the order of the codes (e.g. 00, 10, 11, 01, 00 ... may indicate CCW).
Quadrature decoders translate the input pulses from an encoder to a up/down indicator and a count which could then be translated to distance moved by a wheel assuming no skidding.
A quadrature encoding is in effect a two-bit gray code (00, 01, 11, 10) which may repeat multiple times in 360 degree rotation. For example some motors have a built in encoder that may have 256 and 512 counts per revolution. The direction of rotation is determined by the order of the codes (e.g. 00, 10, 11, 01, 00 ... may indicate CCW).
Quadrature decoders translate the input pulses from an encoder to a up/down indicator and a count which could then be translated to distance moved by a wheel assuming no skidding.
Mike Perks