two-stage pushbutton switch, sort-of DPDT? - Page 1
Forum section: electronics / beginners

author: jayeye
author_rank: Contributor
timestamp: February 19, 2019, 10:04:32 pm
content: My parametric search abilities are failing me here, and digikey does not allow me to do a raw SQL queryI need a small pushbutton switch with two circuits, both normally open. When I push the button halfway, the first circuit is closed, and when I push it all the way both circuits are closed. Does such a beast even exist?(Of course I know I can have two pushbuttons one next to the other, press one, then press the other. Or do it with a 556 to have a delayed monostable pulse, and it will probably be cheaper than the pushbutton switch, but still...)The use case is having a one-finger operation for putting the ESP8266 and its ilk to upload mode: you pull GPIO0 low, pull RESET low, release RESET, release GPIO0. It *has* to be done in that order, can't even do it simultaneously (as if simultaneity existed in circuits, but that's for another show).Cheers,/ji

author: jeroen79
author_rank: Frequent Contributor
timestamp: February 20, 2019, 12:58:06 am
content: How do you want to use it?For something to use over and over during development I would go for one switch and some small microcontroller.For something to use once in a while in a finished product I would add in a double dip switch.If you want to build something yourself then you could use two switches.One is linked to the button with a spring, press it enough and it clicks.You can then press the button further until it touches the second switch.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: February 20, 2019, 02:03:20 am
content: These doulbe switch thingies are used in different applications.Some examples:- Foto camera's where a half puch starts the focussing sequence and a full push makes a picture.- Musical keyboards where the time difference is measured to calculate the velosity of the key movement.- Some specialised relays where a "big" contact takes the stress of opening / breaking a circuit and is bridged by a more sensitive contact during closing.It's because of stuff like this that I do not like to use bootloaders, and prefer to program uC's with a "decent" programmer.Put a target in a makefile for programming, which starts a command line uitility to talk to hardware that programs your shit.Takes a bit of work to setup, but you only do it once and there is no more need for complex Vulcan Finger Salutes to your hardware.I doubt you can buy off the shelf products for this, probably too specialized.You can however make something like this fairly easy yourself.Just take 2 regular push buttons and a lever.Put one button on the end of the leaver and the other near the hinge.The button near the hinge gets actived first, and when you push harder the second buttons gets activated.

author: MarkF
author_rank: Super Contributor
timestamp: February 20, 2019, 02:29:54 am
content: Would an ignition switch type (Off-On-Momentary) work?https://www.amazon.com/Momentary-Ignition-Toggle-Switch-Terminals/dp/B00JWZ8NYO

author: Psi
author_rank: Super Contributor
timestamp: February 20, 2019, 02:59:32 am
content: Most of the 3 position tack switches are On-On-OffSo in idle state they are on, press down a bit a different circuit is on, press down more and they go open.On-On-Offhttps://www.digikey.com/product-detail/en/judco-manufacturing-inc/50-0089-00/543PB-ND/935976On-Off-Onhttps://www.digikey.com/product-detail/en/judco-manufacturing-inc/50-0041-00/529PB-ND/611178

author: Dundarave
author_rank: Regular Contributor
timestamp: February 20, 2019, 03:22:14 am
content: A quick google using the string "three position push button" producedhttps://www.otto-controls.com/p2-3-position-momentary-action-pushbuttonamong other hits... The switch described in the link above looks like it has the action you're seeking. The form factor might be another matter, however, but it looked reasonable.

author: jayeye
author_rank: Contributor
timestamp: February 20, 2019, 03:29:24 am
content: Quote from: Dundarave on February 20, 2019, 03:22:14 amYes, this is exactly the sort of circuit I want. The form factor is an issue, though, but I'll keep it in mind for my missile-launcher projectCheers,/ji

author: jayeye
author_rank: Contributor
timestamp: February 20, 2019, 03:41:14 am
content: Quote from: Doctorandus_P on February 20, 2019, 02:03:20 amI like the lever idea, but this would be a small enough part (the switches are 3mm square) that 3d-printing it on my ultimaker won't have enough accuracy or even structural strength, and I don't have access to a proper mill to machine it (also, not the sort of thing I can just design and send for fabrication, it would need several iterations. In another life, maybe)