G+_John D. Hawkins Posted October 7, 2016 Share Posted October 7, 2016 All right Smart Guys... I'm in need of a small momentary tactile switch (not more than 1/4" square) for a project I'm working on. The catch seems to be in finding the right functionality. I want the circuit to open when its PRESSED and then close when the pressure is RELEASED. The pressure is going to be from a small rare earth magnet pulling an assembly down (when stored) then when you grab or lift it the pressure would be released. I've looked around on Amazon etc and see things that are close but I guess I'm not very good at explaining what I need. A small almost flat switch would be great. I've even been brainstorming "rube goldberg" like mechanisms to do this! That would be a bit cost prohibitive to scale though. Link to comment Share on other sites More sharing options...
G+_Douglas Biggers Posted October 7, 2016 Share Posted October 7, 2016 Why not a NC(Normal Closed) magnetic reed switch? Link to comment Share on other sites More sharing options...
G+_Jim Hofmann Posted October 7, 2016 Share Posted October 7, 2016 Not sure about your configuration. At first I thought a push button would work but then you mentioned a magnet. So, I'm thinking your attracting a metallic pad. Perhaps a micro switch with an attached pad or a magnetic micro switch. Link to comment Share on other sites More sharing options...
G+_Eddie Foy Posted October 7, 2016 Share Posted October 7, 2016 Whats the use? You could add in a bit more circuitry to use the N.O. button. Really nothing more then a transistor and bias resistor to do the inverting. Link to comment Share on other sites More sharing options...
G+_John D. Hawkins Posted October 7, 2016 Author Share Posted October 7, 2016 Its going to be a flashlight not much bigger than a 9V battery. Link to comment Share on other sites More sharing options...
G+_John D. Hawkins Posted October 7, 2016 Author Share Posted October 7, 2016 Awesome! I'll look into that stuff. I think I like the idea of a micro switch. I'm still really green with this stuff and haven't done anything more developed than soldering 22 awg wire. Link to comment Share on other sites More sharing options...
G+_Eddie Foy Posted October 7, 2016 Share Posted October 7, 2016 In all honesty, if you are just starting out, build your own inverting gate. You will learn copious quantities more, that can be use SO many more places. I can not recommend more, the Forest Mimms book(s) As the best 'hello world' book(s) for basic electronics. Example. I took a DPDT relay that as wired to self latch. I had a positive pulse(voltage) available to release the latch/relay. A single transistor/resistor (with a 2nd resistor as a pull-down to avoid the base from floating) did the trick. Link to comment Share on other sites More sharing options...
G+_Eddie Foy Posted October 7, 2016 Share Posted October 7, 2016 Also my old adage: Always do in hardware what you can do in software. I will do preconditioning of AD inputs in hardware to minimize the software manipulations, saving cycles. Link to comment Share on other sites More sharing options...
G+_John D. Hawkins Posted October 10, 2016 Author Share Posted October 10, 2016 I have not idea from a software perspective. This would be totally mechanical. I looked into the Reed Switches but they look like they'll be to big. I was considering fabricating a small piston like assembly that would simply lift the contacts away from each other when pressure is applied. Then lifting the whole assembly would lower it back down into contact. Link to comment Share on other sites More sharing options...
G+_Jim Hofmann Posted October 11, 2016 Share Posted October 11, 2016 If a reed won't fit, it must be a tight space. Could you use a pull up resistor and short to ground? Don't know what the load requirements are or the power requirements (battery?). If you DIY a contact, a "good" switch or relay (contact) are plated to prevent oxidation or swipe to clean the contacts. Some low load circuits don't have enough umph to breakdown the oxidation. I was working in the industry when electronics started to miniaturize. Added tatalum(?) caps to the outputs to help. Fun, fun, fun. Again, don't know your design and it sounds like the contacts will be open must of the time. Good Luck. Link to comment Share on other sites More sharing options...
G+_John D. Hawkins Posted October 11, 2016 Author Share Posted October 11, 2016 Man! Feeling a bit out of my league in here. These are all awesome ideas. The entire assembly (complete) will be slightly larger than a 9V battery. Which will also be the power source. You guys are awesome! Thank you very much for your input. Link to comment Share on other sites More sharing options...
G+_Eddie Foy Posted October 11, 2016 Share Posted October 11, 2016 Funny timing: The current issue of Nuts & Volts has a 'build your own gate' article. Link to comment Share on other sites More sharing options...
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