Hall effect button uses? - Page 1
Forum section: electronics / projects

author: jrmymllr
author_rank: Regular Contributor
timestamp: December 11, 2023, 02:25:31 pm
content: I happened to find Hall-effect pushbuttons on Digikey when I was looking for standard contact-based pushbuttons. I never knew these existed. Given their crazy price, I'd be hard-pressed to find a good reason to buy one even though they sound like a great way to overdesign something. Example:https://www.digikey.com/en/products/detail/apem-inc/IHSH36F6/2601899It makes me wonder, what are real-world use cases for these? I realize their operational life is limited only by how many times the plastic parts can slide past each other, and the output is bounce-free. Maybe in explosive environments since there's no contacts?Have any of you designed these into something, or seen them used?

author: TimFox
author_rank: Super Contributor
timestamp: December 11, 2023, 02:34:10 pm
content: There are many applications that require "explosion proof" or "flame proof" enclosures or components.

author: SeanB
author_rank: Super Contributor
timestamp: December 11, 2023, 02:36:33 pm
content: Seen them used in keyboards as the switches, and they are common in vandal resistant switches used all over, though the most common application is in lifts, where the limited travel, and very large overload capacity are very useful. Actually got some V3B switches that used them as well, which made retrofitting to replace a regular one in an application easy, as it fitted in the same space, and also was coincidentally easy to interface, as it was used with a 5V supply, and the open collector output was perfect to emulate the switch. Plus unaffected by dust, which is what was killing the regular mechanical V3B switches there, and the weatherproof versions would not fit, as they are larger in the back end dimension. Never replaced the switch after that.

author: ejeffrey
author_rank: Super Contributor
timestamp: December 11, 2023, 02:56:15 pm
content: Hall sensors themselves are pretty cheap so the price of buttons like this is presumably due to them being specialty itemsFor instance hall effect limit switches and shaft position sensors are cheap and very common.Explosive or extreme contamination environments seem like the most obvious use case for big panel mount buttons.

author: tszaboo
author_rank: Super Contributor
timestamp: December 11, 2023, 03:00:47 pm
content: Quote from: TimFox on December 11, 2023, 02:34:10 pmThat could be a good answer, but these (specifically the linked ones) aren't that. If they would be, then that would be marked on the datasheet, with the standards it applies, and the protection methods.I think in this one is just the combination of 5 million cycles and IP67.

author: jmelson
author_rank: Super Contributor
timestamp: December 11, 2023, 04:22:31 pm
content: Also, extremely resistant to dirt, liquids and other contaminants. Can't say for sure, but those switches might actually work fine underwater.Jon

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: December 11, 2023, 04:29:43 pm
content: Quote from: TimFox on December 11, 2023, 02:34:10 pmExcept these don't appear to have the required approvals for use in such applications

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: December 11, 2023, 04:31:15 pm
content: Quote from: jmelson on December 11, 2023, 04:22:31 pmYes- the electronics can be completely encapsulated, so waterproofing becomes a lot easer once you no longer have to transmit motion through a seal. Also more scoper for different actuation force, feel etc.

author: TimFox
author_rank: Super Contributor
timestamp: December 11, 2023, 08:04:40 pm
content: They would still make it easier to get the entire assembly (in a rated enclosure) approved as "explosion proof" by the appropriate agencies.

author: temperance
author_rank: Super Contributor
timestamp: December 11, 2023, 09:03:31 pm
content: I use some high quality vandal proof IP67 mechanical switches. (those stainless steel ones) The mechanics inside the switches work fine as long as you stay above the required wetting current and voltage.They stop to work fine when someone decides to spill some soft drink on them and everything sticks together. Washing them doesn't help.The switch shown has the same problem. Depending on the application, they might be a waste of money. They are also more expensive than an illuminated vandal proof switch while they look like a toy from 1970.

author: voltsandjolts
author_rank: Unknown
timestamp: December 11, 2023, 09:08:33 pm
content: Heh, we had some sealed hall switches that stopped working when water got in them...and then froze! Murphy gets you every time.

author: tszaboo
author_rank: Super Contributor
timestamp: December 11, 2023, 11:13:35 pm
content: Quote from: TimFox on December 11, 2023, 08:04:40 pmI'm not that familiar with the explosion proof enclosure (EX d or Ex t) safety concept, only read the standard a maybe two times. But as I recall, every plastic part that are part of the enclosure, needs to have very strict UV rating, thermal aging rating and so on. So for an enclosure, you cannot just throw it together from random parts, every part needs to be specifically rated for very specific standards. For example there are ATEX cable glands, that are a lot more expensive than regular ones.If we are talking about intrinsic safe (not explosion proof), then a hall sensor switch makes sense, because there isn't arcing when opening or closing a switch.

author: temperance
author_rank: Super Contributor
timestamp: December 11, 2023, 11:38:01 pm
content: The example switch "contact" has a maximum rating of 50 mA @ 24 V and requires its own power supply.Applying this switch in an intrinsic safe device requires:-an intrinsic safe power supply for the switch itself. 3.5...24 V, 5 mA max.-an intrinsic safe input on your device.For a normal switch you don't need this power supply able to supply 5 mA and only an intrinsic safe circuit able to deliver the minimum wetting current / voltage which is for a large switch around 1 mA and 5 V. Saving 4 mA can be a great deal for barrier circuits with only resistors.

author: SiliconWizard
author_rank: Super Contributor
timestamp: December 12, 2023, 12:46:56 am
content: Quote from: mikeselectricstuff on December 11, 2023, 04:29:43 pmYeah, I don't know how they would react when submitted to very high accelerations, so if "explosion proof" means that the sensor would still function nominally *during* and *after* the explosion, I don't know if that's the case.

author: abeyer
author_rank: Frequent Contributor
timestamp: December 12, 2023, 04:55:09 am
content: Quote from: jrmymllr on December 11, 2023, 02:25:31 pmnot those ones specifically, but hall effect has shown up several times in fancy over engineered keyboards, eghttps://fluxkeyboard.com/

author: pqass
author_rank: Super Contributor
timestamp: December 12, 2023, 07:26:57 am
content: Quote from: jrmymllr on December 11, 2023, 02:25:31 pmA few months ago I found a nice 4x4 keypad at a junk shop. I thought it was odd that each switch had 4 pins but bought it anyway. At home, I looked up the part number:Micro Switch SD 11A1A. I was pleasantly surprised to discover that each switch had a hall-effect sensor with two open-collector outputs. I'd never heard of such a thing!The SD series (second generation) was introduced in 1976; the earlierSW serieswere the first with hall-effect elements. This was the era of PDPs and Altos where 8 and 16 bit CPUs filled boards made from discrete logic. Keyboards were built like tanks with price to match.The claimed benfit for hall-effect elements were:a. broken plunger/housing can be pulled-off/replaced without desoldering the electrical part (also useful when cleaning the inevitable accumulation of sediment),b. having two open-collector outputs allows each switch to ground two different wires (one row wire, one column wire) thus avoiding the need for (at the time) expensive matrix scanning circuitry and having the encoded output available instantly,c. they are bounce-free, andd. no diode matrix needed..

author: tszaboo
author_rank: Super Contributor
timestamp: December 12, 2023, 11:42:29 am
content: Quote from: SiliconWizard on December 12, 2023, 12:46:56 amIt doesn't (necessarily) mean that. What you describe is, it would survive an external explosion.Explosion proof means the device wouldn't cause an explosion, there are half a dozen different methods of achieving this.Explosion proof, "protection by flameproof enclosure" (Ed d), is one of these methods, where there could be an explosion inside the enclosure, and it cannot leave the enclosure, so the outside is safe.

author: jrmymllr
author_rank: Regular Contributor
timestamp: December 12, 2023, 12:45:53 pm
content: Quote from: pqass on December 12, 2023, 07:26:57 amFascinating. This webpage says "Rated lifetime Tested up to 30 billion (extremely long)" LOLhttps://deskthority.net/wiki/Micro_Switch_SD_SeriesAnd they claim a keyboard using these was made as late as 1996 for Sun!

author: Dan123456
author_rank: Regular Contributor
timestamp: December 12, 2023, 01:05:37 pm
content: Quote from: tszaboo on December 12, 2023, 11:42:29 amI was thinking the same thingLike to be used in a situation where you absolutely can not ever have the possibility of a spark. I.e. in places where a flammable gas leak is a real possibility, such as a natural gas refineryYou wouldn’t want to hit the emergency off switch if there was a chance the switch could produce a tiny spark and blows the whole place up!Apart from that situation, I have no idea what you would use them for

author: abeyer
author_rank: Frequent Contributor
timestamp: December 12, 2023, 08:33:58 pm
content: Quote from: jrmymllr on December 12, 2023, 12:45:53 pmWhich doesn't bode well for actual experience, given how awful most Sun keyboards were!

author: electr_peter
author_rank: Unknown
timestamp: December 13, 2023, 09:56:41 pm
content: Example of magnetic type switches used in a medical drill (from 9:04 to 11:50)