[TriEmbed] TriEmbed Digest, Vol 16, Issue 17

Tue Sep 16 15:17:41 CDT 2014

Pete, 

Thanks for the response - was wondering if I was the only one who struggled with something as basic as finding an on-off switch.  

Here is the data sheet for the push button on-off switch.  Thanks for the pointer on the cheaper Digikey alternative for my SPDT switch.  Guess I will be ordering more of them.

Two other notes not related to this topic.  

	1) I finished my testing of three potential 3.3V power supplies - Boost, Buck-Boost and Linear.  I posted the results on the Triembed.org blog but, it turned out that the TI Switching Buck-Boost power supply could extract about 37% more power from four AA batteries than the linear supply.  
	2) If you are looking for a discount on Sparkfun products, there is a contest running this week that can get you up to a 25% discount off your next order.  It involves taking some social media stuff but, hey I am not above sending a few tweets for a discount.

Thanks,

Chip

On Sep 16, 2014, at 1:00 PM, triembed-request at triembed.org wrote:

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> Today's Topics:
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>   1. Re: Switching Switches (Pete Soper)
> 
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> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Tue, 16 Sep 2014 11:35:40 -0400
> From: Pete Soper <pete at soper.us>
> To: triembed at triembed.org
> Subject: Re: [TriEmbed] Switching Switches
> Message-ID: <541858CC.6010306 at soper.us>
> Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"
> 
> 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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