[TriEmbed] TriEmbed Digest, Vol 10, Issue 30

Charles McClelland chip at mcclellands.org
Fri Mar 28 13:13:56 CDT 2014


To all, 

Thanks to your bread advice and an afternoon with Pete, I have completed the design for the surface mount version of my trail traffic counter - version 5.  You can see the end result as a shared project on OSHPark here - https://oshpark.com/profiles/chipmc

I realized that this board could be more than just a trail traffic counter.  In fact, this board could be used to record any input from an I2C or SPI sensor, apply a date and time stamp and write it to a microSD card.  I met with the EPA earlier this week (on IBM business) but in our discussions in the hall, it occurred to me that this same design could be used to record air quality and environmental data as well.  Maybe this project will have more uses than what I originally imagined.  

There were a few lessons learned (and probably many more to come before version 6) that I thought I would share:

	- EAGLE - To start with I imported the Sparkfun Arudino Pro Mini 3.3 into EAGLE and pulled the board apart.  This gave me a great starting point.
		- I had been using the Sparkfun design rules to check my board by Pete pointed out that OSHpark has their own rules and they are slightly different
		- Oshpark design rules: Eagle DRU file
	- I replaced the 0402 and 0603 parts in the Sparkfun design with 0805 so I could more easily solder them
	- I learned a lot from Peter about surface mount, here are some items I bought on his recommendation:
		- Super fine 0.015” solder - http://www.amazon.com/gp/product/B00HNVBIW8/ref=oh_details_o01_s00_i01?ie=UTF8&psc=1
		- Tack Flux - http://www.amazon.com/gp/product/B001KADQZU/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1
		- Cool boxes to store these crazy small parts - http://www.amazon.com/gp/product/B00EINM3BE/ref=oh_details_o01_s00_i00?ie=UTF8&psc=1
	- After trying to apply solder paste freehand wit Pete, I took the same EAGLE files I send to OSHpark and bought a stencil for the board at www.oshtencils.com
	- Kept the simple linear voltage regulator but moved to a Schottky diode (thanks Carl) and will look at a switching power supply in v6 based on Pete’s suggestions.

I will find out in a couple weeks if this design works.  Perhaps I can even bring it to the next meeting.  

Thanks,

Chip

P.S.  - Saturday is Arduino day - Sparkfun is selling the Pro Mini for $3!!!!




On Mar 21, 2014, at 9:36 PM, triembed-request at triembed.org wrote:

> Send TriEmbed mailing list submissions to
> 	triembed at triembed.org
> 
> To subscribe or unsubscribe via the World Wide Web, visit
> 	http://mail.triembed.org/mailman/listinfo/triembed_triembed.org
> or, via email, send a message with subject or body 'help' to
> 	triembed-request at triembed.org
> 
> You can reach the person managing the list at
> 	triembed-owner at triembed.org
> 
> When replying, please edit your Subject line so it is more specific
> than "Re: Contents of TriEmbed digest..."
> 
> 
> Today's Topics:
> 
>   1. Re: Giving this Surface Mount Thing a Try - Transistor	Help
>      Needed (Charles McClelland)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Fri, 21 Mar 2014 21:36:32 -0400
> From: Charles McClelland <chip at mcclellands.org>
> To: The MacDougals <paulmacd at acm.org>
> Cc: TriEmbed Discussion <triembed at triembed.org>
> Subject: Re: [TriEmbed] Giving this Surface Mount Thing a Try -
> 	Transistor	Help Needed
> Message-ID: <5F457724-0B71-400C-8AF1-A44552BFFB59 at mcclellands.org>
> Content-Type: text/plain; charset="windows-1252"
> 
> Paul, 
> 
> With the Sleep, I2C, SPI and SD libraries, my code is currently 18k.  Guess that settles it unless I was willing to go to a SPI accelerometer and reduce the code.
> 
> I have attached it here: 
> 
> Thanks,
> 
> Chip
> 
> On Mar 21, 2014, at 9:19 PM, The MacDougals <paulmacd at acm.org> wrote:
> 
>> How big is your code?  If it is 8K or larger, you will have to go through the pain of reducing it.  If it is much larger, you may not ever succeed.
>> If you decide to try the Tiny, I can help with examples of using pin change interrupt.
>> 
>> ---> Paul
>> 
>> 
>> From: Charles McClelland [mailto:chip at mcclellands.org] 
>> Sent: Friday, March 21, 2014 5:41 PM
>> To: The MacDougals
>> Cc: Glen Smith; TriEmbed Discussion
>> Subject: Re: [TriEmbed] Giving this Surface Mount Thing a Try - Transistor Help Needed
>> 
>> Paul, 
>> 
>> I was planning on using the ATMEGA328 as that is what is on the Arduino Pro Mini board.  Now that you mention it, I guess I could use the ATTiny84.  I did try to use the pin change interrupt on the ATTiny84 but was not able to get it to awake form sleep except with a LOW signal.  I wonder if that may be a limitation of the Sleep library I am using.  
>> 
>> Back to the chip choice.  Please let me know if I am missing anything on this list of pros and cons:
>> 
>> ATTiny84
>>            - Pros: Cost, size, number of external components required
>>            - Cons: This board uses both SPI and I2C so would need to learn how to ?bit bang?
>>            - Don?t know - power / battery life?
>> 
>> ATMEGA328
>>            - Pros: More pins for inputs and indicators (thinking about adding some more controls)
>>            - Cons: Cost, size, needs an external crystal
>> 
>> The easy choice would be to stay with the ATMEGA328 as I have the sketch working and have developed and field tested the design over the past 6 months.  But, am I missing something that could sway me toward the Tiny?
>> 
>> Thanks,
>> 
>> Chip
>> 
>> 
>> On Mar 21, 2014, at 4:42 PM, The MacDougals <paulmacd at acm.org> wrote:
>> 
>> 
>> Since you are collapsing all of the breakout boards, what are your plans for the processor?
>> As I recall, the reason for having to invert the signal was due to a limitation on the external
>> interrupt pin of the processor.  Newer Atmel chips have pin change interrupts on all pins
>> and can handle either edge.  So, if you go with an ATTiny 84 or similar, you don?t need the transistor.
>> 
>> ---> Paul
>> 
>> 
>> From: TriEmbed [mailto:triembed-bounces at triembed.org] On Behalf Of Charles McClelland
>> Sent: Friday, March 21, 2014 3:47 PM
>> To: Glen Smith
>> Cc: TriEmbed Discussion
>> Subject: Re: [TriEmbed] Giving this Surface Mount Thing a Try - Transistor Help Needed
>> 
>> Glen, 
>> 
>> I am using EAGLE - it allows you to set the names so I guess I have to take responsibility  - Resister Base (RB)  - I am learning so if there is a better naming convention I should be using, I would be open to it.
>> 
>> Thanks,
>> 
>> Chip
>> 
>> 
>> On Mar 21, 2014, at 1:29 PM, Glen Smith <mrglenasmith at gmail.com> wrote:
>> 
>> 
>> 
>> Charles,
>> 
>> As Bill said, there are single gate IC's to do what you want, a quick glance indicates the cheapest (in one'sie two'sie quantities) is $0.33. But there are 2222 transistors available in SOT-23 packages: Jameco has them here: 
>> http://www.jameco.com/webapp/wcs/stores/servlet/StoreCatalogDrillDownView?langId=-1&storeId=10001&catalogId=10001&freeText=2222%20sot-23&search_type=jamecoall 
>> qty 10 available at $0.09 each. Or, to keep the comparison, DigiKey has them here: 
>> http://www.digikey.com/product-search/en?pv7=2&FV=142c0042&k=MMBT2222A&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25 
>> (for one'sie two'sie quantities) at $0.18 each.
>> 
>> It has been far too long since I did transistor circuit design to tell you whether what you have will do the inversion you want, but you can hook it up on a breadboard with your discrete's and see how it works.
>> 
>> Since I'm sending this note anyway, is there a reason why you chose RA, RB RC designations? It took me a few minutes looking at your circuit to figure out that it was a designator rather than a ResistorCapacitor (RC) network. Maybe it is just what I'm used to working with. Which layout tool are you using? KiCAD or Eagle? If one of them forces me to use RA, RB, RC - I think I will use the other.
>> 
>> Glen
>> 
>> 
>> On Fri, Mar 21, 2014 at 12:46 PM, Bill Farrow <bill at arrowsreach.com> wrote:
>> Charles,
>> There are single logic gate ICs in surface mount which should do what you want. Here's my quick digikey search.
>> 
>> http://www.digikey.com/product-search/en?pv247=24&pv64=1&pv667=1&pv69=3&FV=fff40027%2Cfff8019d&k=single+gate&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25
>> 
>> 
>> Bill
>> 
>> 
>> _______________________________________________
>> Triangle, NC Embedded Computing mailing list
>> TriEmbed at triembed.org
>> http://mail.triembed.org/mailman/listinfo/triembed_triembed.org
>> TriEmbed web site: http://TriEmbed.org
>> 
> 
> -------------- next part --------------
> An HTML attachment was scrubbed...
> URL: <http://mail.triembed.org/pipermail/triembed_triembed.org/attachments/20140321/bd2f5a19/attachment.html>
> -------------- next part --------------
> A non-text attachment was scrubbed...
> Name: Sleeping_Trail_Counter_v4.zip
> Type: application/zip
> Size: 10109 bytes
> Desc: not available
> URL: <http://mail.triembed.org/pipermail/triembed_triembed.org/attachments/20140321/bd2f5a19/attachment.zip>
> -------------- next part --------------
> An HTML attachment was scrubbed...
> URL: <http://mail.triembed.org/pipermail/triembed_triembed.org/attachments/20140321/bd2f5a19/attachment-0001.html>
> 
> ------------------------------
> 
> Subject: Digest Footer
> 
> _______________________________________________
> TriEmbed mailing list
> TriEmbed at triembed.org
> http://mail.triembed.org/mailman/listinfo/triembed_triembed.org
> 
> 
> ------------------------------
> 
> End of TriEmbed Digest, Vol 10, Issue 30
> ****************************************

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.triembed.org/pipermail/triembed_triembed.org/attachments/20140328/4abd0537/attachment.htm>


More information about the TriEmbed mailing list