[TriEmbed] TriEmbed Digest, Vol 16, Issue 17

Tue Sep 16 15:59:43 CDT 2014

Pete,

   Thanks for putting up your comparison of power supplies.  I've been 
building some temperature sensors using the NRF24L01+ module and came 
upon the Microchip MCP1700-3302E (3.3V LDO) for my purpose.  I don't 
really like using LiPos (except outdoors in RC planes where I won't burn 
down the house) and in my case I selected a 4 x AA Enerloop battery 
pack.  The MCP1700 has a very low quiescent current but I'm not sure 
about the efficiency compared to your best module.  The datasheet 
doesn't give any information. My current use case is probably different 
than yours as I only need ~30ma peak.  The MCP1700 is good up to 250ma.  
Also the MCP1700 comes in a TO-92 package which I liked since I'm not up 
to speed on making and soldering SMD PCBs (yet).

   I'll have to investigate the power supplies you tested some more to 
see if it makes sense to build newer temperature sensors with those.

Michael Fulbright

On 9/16/2014 4:17 PM, Charles McClelland wrote:
> 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 
> <http://media.digikey.com/pdf/Data%20Sheets/Judco%20PDFs/50-0015-00.pdf> 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 <http://triembed.org/blog/?page_id=234> 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 <https://www.sparkfun.com/news/1594> 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 
> <mailto:triembed-request at triembed.org> wrote:
>
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>> Today's Topics:
>>
>>   1. Re: Switching Switches (Pete Soper)
>>
>>
>> ----------------------------------------------------------------------
>>
>> 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
>>>
>>>
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> Triangle, NC Embedded Computing mailing list
>>> TriEmbed at triembed.org
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