Our knobs go to 11 - but which way round? - Page 1
Forum section: electronics / general

author: nfmax
author_rank: Super Contributor
timestamp: June 22, 2022, 11:33:24 am
content: For as long as I can remember, all* rotary control knobs on electrical & electronic equipment turnclockwisetoincreasewhatever it is that they are controlling. On the other hand, water, air and steam control valves all turnanti-clockwiseto increase the flow.So why the difference? I assume control valves came first. Given the general preference for right-hand threads it makes sense that a threaded stem would close a valve when turned clockwise. Why we chose right-hand threads I don't know. Probably, it is down to spontaneous symmetry-breaking: the choice is initially random, but once made, sticks.So why are electrical controls different? And when did this difference first appear? With the appearance of 'wireless', or earlier? I don't know if early electrical installations used rotary controls of any sort, or even rotary switches. Was it a deliberate choice, an independent event, or a consequence of an unrelated design decision? As a speculative example, you might have a rheostat in the filament circuit, using 'water valve' convention, so that turning anti-clockwise increases the resistance. Used as a volume control, this means that turning clockwiseincreasesthe volume. OTOH there were tuning and reaction controls on wireless sets well before volume controls became necessary - and I don't know what convention these used.(*) Except on the Sebo vacuum cleaner I am currently repairing. Which is what prompted this post

author: penfold
author_rank: Frequent Contributor
timestamp: June 22, 2022, 11:55:57 am
content: Quote from: nfmax on June 22, 2022, 11:33:24 amInteresting point, it is possible that because the right handed thread for right handed people gives a more natural greater force in the clockwise direction, the choice between CW and CCW could just be particular to the style of valve and whether more force is needed to open or close, perhaps against the pressure of fluid. Just thinking out loud... not thought through for all valves in all cases or cases when the thread direction is reversed to preserve convention over other optimisations.Otherwise, when mechanical advantage or other constraints don't matter, its just a matter of having numerals in a more conventional CW direction.

author: Circlotron
author_rank: Super Contributor
timestamp: June 22, 2022, 12:36:45 pm
content: And clockwise would have originated from the direction of travel of the shadow of a sundial in the northern hemisphere.

author: Circlotron
author_rank: Super Contributor
timestamp: June 22, 2022, 12:38:30 pm
content: Left handed guitars would be a good case for a volume pot going anticlockwise to increase volume.

author: xrunner
author_rank: Super Contributor
timestamp: June 22, 2022, 12:43:18 pm
content: Quote from: nfmax on June 22, 2022, 11:33:24 amWell I can argue it's not reversed ...Turn the volume clockwise and it increases audio output.Turn the water faucet clockwise and it increases restriction of the water output.Just a matter of your point of view.

author: ataradov
author_rank: Super Contributor
timestamp: June 22, 2022, 05:27:54 pm
content: I would agree with that. The goal of the valve is to restrict or close the flow. Turning CW does more of the thing.

author: Geoff-AU
author_rank: Frequent Contributor
timestamp: June 23, 2022, 04:58:53 am
content: Yes.. the purpose of a valve is to stop the flow, not to start it.

author: PlainName
author_rank: Super Contributor
timestamp: June 23, 2022, 01:01:58 pm
content: As y'all note, a valve is typically based on a right-handed thread, and screwing in closes it. But that also means that you press harder by turning to the right, and if you want something louder then you acoustically pressing harder, hence screwing in the volume control.

author: nfmax
author_rank: Super Contributor
timestamp: June 23, 2022, 02:00:40 pm
content: My experience with valves is that if you want it open, it sticks closed. But if you want it closed, it sticks open. Each way is harder to turn than the other

author: PlainName
author_rank: Super Contributor
timestamp: June 23, 2022, 02:08:25 pm
content: That's why we switched all our taps to ball valves

author: TimFox
author_rank: Super Contributor
timestamp: June 23, 2022, 03:48:58 pm
content: As an undergraduate in the late '60s, I ran the microphones and lights for the Sunday chapel services.The chapel's PA system was a high-class Altec-Lansing system, with a vacuum-tube mike mixer and power amplifier located at the front end of the sanctuary and a remote (opto-isolated) volume control knob in the balcony.I would enter from the front end of the building, turn on the system at a master power switch, and walk to the stairs at the rear to ascend to my perch at the volume control and light switches.One Sunday, when I was half-way to the back of the auditorium, there was a horrible feedback screech (after about 10 sec warm-up) and I ran back to the amplifier to kill power.I went upstairs and found the knob turned full CW (maximum volume), which I reset to CCW, returned to turn the amplifier power on, and went back to the control and ran the system normally.This happened once more. The third Sunday, I started upstairs at the volume control, found it at CW again, and started everything properly.The elderly organist complained to me, and I replied "some idiot keeps turning the volume control to maximum while I'm gone".She was taken aback, since the idiot was herself: Altec-Lansing had labelled the knob in dB attenuation, with CCW = 40 dB attenuation and CW = 0.She had interpreted that as 0 being minimum volume (at CW).

author: xrunner
author_rank: Super Contributor
timestamp: June 23, 2022, 04:07:54 pm
content: My Samsung TV shows volume attenuation: as the volume decreases the number at the bottom right of the screen gets "bigger" (even though it's a negative number). Well, it mightseemthat way to the mass consumer, to us it is getting more and more negative, which means more attenuation. That's correct.It does have a "-" sign in front of the number and then a bit more to the left a "speaker" symbol. But I'm positive many people will not think that much about it, all they see is a number getting larger, which to them should mean "louder".

author: nfmax
author_rank: Super Contributor
timestamp: June 23, 2022, 05:21:06 pm
content: Quote from: TimFox on June 23, 2022, 03:48:58 pmSee also: BBC faders

author: PlainName
author_rank: Super Contributor
timestamp: June 23, 2022, 05:59:56 pm
content: QuotePerhaps the TV is meant to be a sub-part of a system. If the intention is for the sound to be piped via a hifi system, say, then typically you have a master volume on the hifi which you use to set the desired output level. The volume control on the sub-parts (TV, tape player, etc) would not be adjusted once set. In that kind of situation the device output would be assumed to be max, so if you need to adjust it at all, to match all the other devices, you will be attenuating it.

author: bill_c
author_rank: Regular Contributor
timestamp: June 23, 2022, 08:06:54 pm
content: Get a calculator (or keyboard with number pad), hold it next to your phone dial pad...