What kind of button caps to use for tactile switches

Discussion in 'The Projects Forum' started by misterconsister, Oct 16, 2011.

  1. misterconsister

    Thread Starter New Member

    Sep 23, 2011
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    I have this Velleman kit that has 4 tactile switches as can be seen in the first photo attachement. I mounted the PCB in the project box shown and would like to be able to have button caps to activate the 4 tactile switches. I would like to have the buttons mounted on the outside of the top of the box (see second photo).

    However, I cannot find a source for button caps that would activate the tactile switches I have and that also mount on the box. Can this be done? What kind of button caps work with these "low profile" tactile switches? VC_ProjBox1.jpg VC_ProjBox2.jpg

    Thank you, Eric
     
  2. KJ6EAD

    Senior Member

    Apr 30, 2011
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    The easiest way is to replace the tactile switches with another that has the same footprint but includes an extended actuator. Just google tactile switches and browse the offerings.
     
  3. Georacer

    Moderator

    Nov 25, 2009
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    Getting the switches on the outside of the box is one of my constant problems when building a device.

    If I have space, I mount the switches on the box and wire them to the board. Your situation is a bit shorter in space.

    If you don't want to change the switches, as KJ6EAD suggested, you could look for other switches' caps and modify your box to fit them.

    It's about your modding skills, really.
     
  4. Wendy

    Moderator

    Mar 24, 2008
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    You can also shape wood, plastic, or if you have the means, metal, to fit in the case. I've never done this yet, but I put a little thought into it. Here is how I would do it...

    [​IMG]

    The length of the bottom shaft on the center piece would be the same as the distance of the top of the tactile switch (not pressed) and the bottom of the hole in the case.
     
  5. misterconsister

    Thread Starter New Member

    Sep 23, 2011
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    Bill, thanks for the custom idea sketch. I considered doing something like this but, for this time, I think I'd like to get a manufactured solution.

    I've Googled it and have found some good ones with long actuators. Do they all have pretty much the same footprint (how can you tell the difference?) And does 0.05A @ 12V DC sound ok?

    Eric
     
  6. MrChips

    Moderator

    Oct 2, 2009
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    Why don't you post the part number you have found and I am sure someone is going check the footprint and specs for you.

    I like Bill's solution. It would be easy to make with wood dowelling glued on to a larger diameter dowelling. You can also use a standard straight nail cut to the right length.
     
  7. SgtWookie

    Expert

    Jul 17, 2007
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    Probably the best place to look would be on Digikey's site. Start by entering "tactile switch" in the search field, and you can then narrow down the choices presented.

    Getting familiar with reading datasheets will help you to determine if a particular part is suitable for your project. Switch datasheets usually include a 3-view drawing along with a pad layout.
     
  8. misterconsister

    Thread Starter New Member

    Sep 23, 2011
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  9. misterconsister

    Thread Starter New Member

    Sep 23, 2011
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  10. KJ6EAD

    Senior Member

    Apr 30, 2011
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    You must have concluded by now that there are certain industry standard nominal footprints such as 6mm, 9mm or 12mm. The term footprint refers to all of the properties of the device for which location and size must be planned or provided for in the x and y axes. The term outline only refers to the circumference of the component and is a subset of the term footprint. In your case you must be slightly concerned with the outline but mostly concerned with the footprint in regard to lead location and spacing.

    In the example you linked, the footprint drawing shows 4 1mm leads in a rectangle 4.5mm X 6.5mm. Does it match the measured lead spacing of your existing switches?
     
    Last edited: Oct 17, 2011
  11. misterconsister

    Thread Starter New Member

    Sep 23, 2011
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    Yes, the lead spacing is 6.5 x 4.5 and the switch is 6.0 mm square. Now I'm getting it narrowed down.

    My only remaining question is, given the attached diagram, would 12V 0.05A work? I'm not yet sophisticated enough to be able to identify the expected current at a given point in a circuit.

    Thanks,

    Eric
     
  12. KJ6EAD

    Senior Member

    Apr 30, 2011
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    ZD1 regulates the supply voltage to IC1 and it's modulation LED (LD2) at 3V but you may need to increase R1 to compensate for the higher voltage and prevent damage to LD1. The amplifier (IC2) is rated for 12V but 50mA is a very small 12V supply and may not be enough current. Are you sure it's not 500mA or 0.5A? Can you measure the current being drawn by the circuit when it's operating from a 9V supply during all modes of operation?
     
  13. misterconsister

    Thread Starter New Member

    Sep 23, 2011
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    Although I have a working understanding of electricity, my skills with circuits is still pretty limited. I'm not sure I'd feel confident that I wouldn't fry something poking around with my multimeter. It may be no coincidence either that my father in law just pointed out that my multimeter wasn't measuring voltage or current properly.

    So I'm not sure what the circuit's current is but if 0.5A makes more sense to you then it is quite a bit more likely to be that then my guess of 0.05A.

    BTW I'm looking at new multimeters right now - any manufacturer suggestions for a noob? I'm only looking for volts (DC and AC), amps (big and small), ohms, continuity test and digital.

    Thanks again,

    Eric
     
  14. Wendy

    Moderator

    Mar 24, 2008
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    There are two schools of thought on that one, buy cheap or buy expensive. My experience in general is the leads are more important. You must have a set that is easy to handle. Over the years I've bought accessories for the leads to allow them to "grab" a wire.

    Even cheap meters are surprisingly accurate, but when I see a set of leads permanently bonded to the meter it turns me off. Expensive meters come with extras like capacitance meters and frequency counters are useful. Really expensive meters tend to be super rugged, and can take more mechanical abuse, though I have seen some cheap knockoffs that also seem to be pretty rugged.

    I suspect you will get a lot of opinions, it seems to be a hot topic button with some people. I would get as cheap as you could and still have all the features you need. Your description says cheap. Personally I like having a capacitance meter and a frequency counter, it has come in handy over the years.

    Most serious hobbiests have more than one meter. This is because you occasionally need to measure more than one thing at a time.

    Oh, and one last thing, make sure the meter is really rated for AC use. Messing with a piece of equipment that may not handle house hold voltage can itself be dangerous, this is where brand names come in.
     
  15. KJ6EAD

    Senior Member

    Apr 30, 2011
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    I thought you were referring to the capacity of the supply, not the draw of the circuit. A 50mA rating is quite low for a supply but may be about right for the circuit as it's designed to operate from a 9V battery. I don't see any serious problems with running it from 12V.

    Take a look at the various multimeter reviews on the EEVblog. Start with this episode.
    http://www.eevblog.com/2010/04/14/eevblog-75-digital-multimeter-buying-guide/
     
  16. misterconsister

    Thread Starter New Member

    Sep 23, 2011
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    After some frustration finding a new tactile switch that has a plunger that's 17 MM high, I've given up for the time being and made very simple temporary buttons.

    I simply cut four buttons out of 1/4" plastic dowell, sanded them and attached them with a lttle dab of superglue on the center-top of the tactile switch pad. I made sure not to drip any SG onto the switch itself.
    (see photos). So far, over several hours they're holding up.

    I also bought a new MM and have attached a photo. I like that it's compact like my last one (a Philips) and that it has a backlit display and a Hold button.

    I'll get back to the switch buttons after I get some other things on my costume built. For now it works and lets me demo my costume.
     
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