[TriEmbed] TriEmbed Digest, Vol 16, Issue 17

Tue Sep 16 17:03:37 CDT 2014

That was Chip McClelland. :-)
-Pete

On 09/16/2014 04:59 PM, Michael Fulbright wrote:
> 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
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
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