[TriEmbed] Switching Switches

[Pete Soper]

I'm not an expert, but I've spent dozens of hours looking at switch 
specs over the past few years and know your pain. I haven't found a 
decent cheat sheet for the nomenclature Digikey and others use either 
(e.g. "off-(on)"). I spent another few minutes searching and only 
reminded myself that the Wikipedia page 
<http://en.wikipedia.org/wiki/Switch#Contact_terminology> is still 
worthless for this nomenclature. Can anybody reading this put us out of 
our misery?

But don't buy that E-Switch part from Sparkfun, buy it from Digikey as 
EG1903-ND 
<http://www.digikey.com/product-detail/en/EG1218/EG1903-ND/101726?WT.z_cid=ref_octopart_dkc_buynow&site=us> 
($13.69 for 25). This is the same switch I've been using for a while. 
There doesn't appear to be the obvious, potentially smaller SPST choice 
(the E-Switch data sheet doesn't show one). But I agree 100% with your 
heart: there is a much smaller press-on, press-off switch out there some 
place. And this little slide switch we're using is the pits as far as 
stuff splashing on it.

I haven't found any smaller switches except for tactile momentary ones, 
which you wouldn't want unless you wanted to try Dave Jone's 
soft-latching switch design 
<http://www.eevblog.com/2012/03/30/eevblog-262-worlds-simplest-soft-latching-power-switch-circuit/>. 
(Not recommending that as a good choice for you, just as an FYI and 
maybe of interest to others).

I'll try to remember to bring the collection of tactile switches I got 
to try out for a project a while back. It might give folks at the next 
meeting some idea of the mapping between "X grams pressure" and what 
that really feels like, as well as sizes, etc.

Finally, we need a generic link to that Digikey switch you mentioned: 
the URL in your msg isn't valid.

-Pete

On 09/14/2014 03:59 PM, Charles McClelland wrote:
> To any switch experts,
>
> I have been looking for a small switch to turn on and off my low-power 
> board (less than 100mA) and have not found anything great.  Part of 
> the issue is that the terminology of switches is confusing: on-off, 
> on-mom, off-(on), etc.  and some of it must be due to my last of skill 
> in doing parametric searches on Digikey and Mouser.  I just know the 
> switch I am looking for is out there but which of the tens of 
> thousands is it?
>
> I have been usingthis <https://www.sparkfun.com/products/102> Single 
> Pole Double Throw (SPDT) power switch from Sparkfun.  It works well 
> but it takes up space and I only need a Single Pole Single Throw 
> (SPST) variety.  Ideally, I could find a push-on, push-off switch 
> which - I believe - is written on-off in the switch function 
> terminology but I have yet to find a source in my Google searching 
> that would confirm this.
>
> I found this switch 
> <http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail&itemSeq=157282720&uq=635463031929636734> after 
> a long search but I am still not sure it is the one I need as it only 
> says it is on-off (and not the more descriptive push-on, push-off) 
> anywhere on the documentation or website.  Also, I am not sure if 
> there is something else I am missing after Paul's presentation where 
> the switch had significant noise.  This should not be a big deal for a 
> power switch as I have a couple capacitors on both sides of the power 
> regulator - correct?
>
> I am sweating these decisions because I need to make a number of these 
> boards for a project with the City of Raleigh and I don't want to 
> screw it up.  If you have other suggestions within my component budget 
> of $1.50 a piece, please let me know.
>
> Thanks,
>
> Chip
>
>
>
>
>
>
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