[TriEmbed] Giving this Surface Mount Thing a Try - Transistor Help Needed

Fri Mar 21 20:36:32 CDT 2014

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
>  
> 
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