Is there a "standard" way to convert switch operation? - Page 1
Forum section: electronics / general

author: Fred Basset
author_rank: Regular Contributor
timestamp: July 09, 2020, 08:58:11 am
content: I was looking at switches (one of my favorite componenets) and found myself wondering if they had the type of switch I liked, but in a normal on/off contact, rather than momentary? OK< I can use a flip-flop, but is that over-engineering?That is when it struck me to wonder if there is some "typical" (ie cheap, easy and reliable) to convert momentary to latching, latching to momentary, both to only-on-as-long-as-you-press-it, and so on? I have never heard of anything like this, but it could be a good chart for when you cannot get the switch you want, or are modifying already existing equipment?

author: capt bullshot
author_rank: Super Contributor
timestamp: July 09, 2020, 11:08:34 am
content: Switches of this (and similar) kind can be configured and manually converted from latching to momentary, or radio-button mode (pressing one key releases others) by manipulating their mechanical elements:

author: Benta
author_rank: Super Contributor
timestamp: July 09, 2020, 07:07:47 pm
content: Quote from: capt bullshot on July 09, 2020, 11:08:34 amYep. Used to be Schadow, then ITT Schadow, today it's C&K. Search for the "F series":https://www.ckswitches.com/product-selection/pushbutton/

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: July 10, 2020, 02:43:45 am
content: Quote from: capt bullshot on July 09, 2020, 11:08:34 amWhen the OP states'to convert momentary to latching, latching to momentary, both to only-on-as-long-as-you-press-it'his idea of 'momentary' which is not congruent with standard usage, seems to be similar to an 'Einschaltwischer'. Can those switches be converted into that? I don't see how.To be really free in creating most of the switch actions defined in the related standards, one needs a different type of switch.I have done that on several occasions, but it needs a combination of electromechanical knowledge, extreme dexterity and some not-so-common fine tools.Then you can start with switches, that have open contact sets and you can convert them into any characteristic that you want. For example the functions 'Folgeschliesser' and 'Folgeoeffner' (sequential closing and opening contacts, which can apply to a set of three contacts making contact among all three or to two electrically separate NO contacts) can be build as well as wipers. Manipulating the actuation part will change between latching and momentary action.Examples of such Switches would be the series FgBv87 of the former DBP, which was in use by all major telephone and telecommunications manufacturers. (See the larger switches in the Picture below)Not only can their contact sets be manipulated, but there are very interesting switch variants by design. For example, I do have both a switch with a holding coil and several with a lever, onto which a tripping coil (or other mechanical actuation) can act. In the picture, both push-actuated switches and rotation-actuated switches are shown. The nice thing is, that they all share a mounting geometry.Another type of switch which lends itself to such practices are Kellog switches, although their narrow definition of up-down or up-neutral-down lever actuation limits the possibilities somewhat. There exists even a series of miniature Kellog switches (the FgBv of which I sadly o not know) which share the contact set components with the FgBv87. The Kellog switches shown are momentary as well as bistable (or tristable ones.One must sacrifice some specimen (or have some defective ones) initially in order to gain contact elements, the so-called 'pimpel' and the thin isolator sheets. An absolute necessity for such an undertaking is the availability of contact adjusting pliers and -levers.Another possibility, which is seen on some more recent industrial examples of combination switch actions is the use of encapsulated snap-action switches in combination with a specially shaped actuator.

author: capt bullshot
author_rank: Super Contributor
timestamp: July 10, 2020, 05:51:08 am
content: For an electronic way to convert the switch action (e.g. push-button to on/off), today specialty on-off ICs do exist. These may have special functions to e.g. produce a reset signal if the button is pressed long enough. Within a complete system, this task (system on-off / reset) sometimes is assigned to a smallish low power microcontroller.Anyway, these old "Deutsche Post" switches mentioned by Neomys give some other kind of user experience(I vaguely remember them too). Used in POTS equipment, both central exchange and end user units. In automated telephone exchange, tons of relays were used that had similar means to adapt their contacts and energizing coils.

author: capt bullshot
author_rank: Super Contributor
timestamp: July 10, 2020, 05:58:30 am
content: Quote from: Neomys Sapiens on July 10, 2020, 02:43:45 amI remember some kind of "WIschkontakt", that was attached to the bar that is the base of a multiple switch array. Within that bar is a kind of slider that releases other switches if one is pressed. The movement of this slider could be used to create that "Wischkontakt" action (momentary contact when a switch is pressed, like an edge detector). Don't ask me for further details, it's just a vague picture in my mindOld TV of a certain generation sets had mains power switches with build-in "Wischkontakt", these looked and operated like a single of the "Schadow" switches (just larger, due to the voltage and ampere rating).

author: Fred Basset
author_rank: Regular Contributor
timestamp: July 10, 2020, 11:34:38 am
content: NeomysIn what way is my understanding of "momentary" wrong? I think you have misundrstood my post...Momentary means that no matter how long you hold the button in, you will get only a momentary contact inside the switch.Latching switches are the opposite. There the switch will stay on (or off) until it is pressed again, or a special release button is pressed.The last part referred to switches where the contacts are closed (or open as in the case of NC) as long as the button is held in. Such as in starter switches.This is only a muse, so not formally written, however it is congruent. I am sorry you misunderstood me.

author: Fred Basset
author_rank: Regular Contributor
timestamp: July 10, 2020, 11:50:16 am
content: Quote from: capt bullshot on July 09, 2020, 11:08:34 amCaptain Bullshot - Thank you very much indeed. These are indeed the sort of switches I was thinking I might have to emulate in some way. I could not find them, probably because I was not looking for the right name. My grateful thanks to Benta for pointing out they are C&K now.I was just wondering how I could convert between the different properties of how the contacts make contact, when I realised I had never seen an "official" answer anywhere. It seemed like the sort of problem a teacher might set their students and so I thought there might be some fun in seeing if we could come up with the best method.However I know from my previous work that it is hard to beat "radio" switches for price and format. Especially if they are good quality, they can be very reliable also. I just have not seen them for sale for a long time now.Another variation of course is make-before-break, or break-before-make contacts, But thanks to Neomys' post there seems little point in continuing a thought experiment into changing how contacts behave.Thank you for your help!

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 10, 2020, 12:40:49 pm
content: Quote from: Fred Basset on July 10, 2020, 11:50:16 amThat functionality is most often done in a microcontroller nowadays.

author: tooki
author_rank: Super Contributor
timestamp: July 10, 2020, 01:07:47 pm
content: Quote from: Fred Basset on July 10, 2020, 11:34:38 amYes, your understanding is wrong.“Momentary” in the context of switches means “activated as long as you hold it”. I actually don’t know what you’d call a switch that only creates a defined-length pulse; I’ve never heard of such a switch. For that effect, you use a momentary switch and a timer circuit.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: July 10, 2020, 01:25:15 pm
content: According to IEC, the term for 'Wischkontakt' is 'passing make contact'. Maybe 'impulse contact' would be the term more often practically used.@Fred Basset: as you may have noted, I did not hold it against you or declared it as wrong, but. as I wrote, as not in line with the standard usage. Would I not be intimately familiar with those terms both in standards and in industrial practice, I might have chosen the same wording.But as you can easily see from the commerial offerings, momentary action pushbuttons are manyfold, and the functionality described is not met by them.

author: Fred Basset
author_rank: Regular Contributor
timestamp: July 10, 2020, 01:38:11 pm
content: I used to buy small switches with a "hat". They were sold as "ordinary" momentary contact switches at most electronic supply stores. I breadboarded them, and using an LED, you got close to a 0.25 second closure of the contacts, irrespecive of how long I held in the button, or released it quickly. They were useful for producing pulses for 4000 series and 74 series ICs. They were often used for that very purpose becuase of that property.Maybe it is difference in language? Since two of you now are saying the same thing, maybe there is a difference between our countries in the meaning of momentary then? What you are describing would have been known in my country as non-latching on/off push switches.

author: capt bullshot
author_rank: Super Contributor
timestamp: July 10, 2020, 02:21:23 pm
content: Quote from: Fred Basset on July 10, 2020, 01:38:11 pmThat's an interesting kind of switch. Never seen one, and never heard of that. There must be some spring action inside, similar what Neomys called the "Wischkontakt", though the ones I knew had a slightly different action.Don't know any term for what you describe, neither German nor English. Anyway, the big mighty internet explains "momentary switch" as a push button that closes or opens a circuit as long as you press it - that's what I did understand in the first place.

author: tooki
author_rank: Super Contributor
timestamp: July 10, 2020, 04:41:57 pm
content: Quote from: Fred Basset on July 10, 2020, 01:38:11 pmNope. I’m American, and as a kid I shopped for parts at radio shack, where they were called momentary switches. For example, look at page 133 of the 1990 radio shack catalog:https://worldradiohistory.com/Archive-Catalogs/Radio-Shack/Radio-Shack-1990.pdfI’m not sure where you got your terminology, but your private vocabulary doesn’t agree with standard usage. Non-latching is certainly understandable, but everyone understands “momentary” to mean the same thing as that. Pushbutton pulse generating switches I’ve never heard of (other than piezo buttons).

author: Benta
author_rank: Super Contributor
timestamp: July 10, 2020, 05:51:27 pm
content: The Schadow, or now C&K F-series all work the same way. I attach a drawing from the datasheet to explain what I mean.The basic F-switch has a push-on, push off function.If you remove the small clip shown in red, it turns into a momentary switch.If you want "radio button" functionality, you need the U-profile mount, plus the related "release bar" with leaf spring. This provides a different latching function through a slot in the switch, blue in the picture.

author: Fred Basset
author_rank: Regular Contributor
timestamp: July 10, 2020, 10:13:08 pm
content: That is where the problem arises then, I did not grow up or learn electronics in America.Do not tell others they are wrong, or refer to private terminology as it can cause offense.

author: tooki
author_rank: Super Contributor
timestamp: July 11, 2020, 12:24:22 am
content: Quote from: Fred Basset on July 10, 2020, 10:13:08 pmYou’rethe one who brought up country of origin! Regardless, this discussion is talking about what they’re called in English, and in English, a “momentary” switch hasoneaccepted meaning, no matter which country one is from.You asked how your understanding is wrong, and I confirmed that it’s wrong and explained why.Telling someone that their incorrect usage is a “private vocabulary” is offensive? Say what now?